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Why would you use electricity when the thermal energy from the Sun is far greater? You're going to take electricity and turn it into heat when the Sun is already producing heat Just have a container of liquid sitting outside. Painted black encased in glass and run that liquid in the house Years ago I lived in an old house and we had hot water to all the sinks except the laundry room sink. It was just cold water I bought a 75-ft black hose, just a garden hose and a connector so it would fit on the faucet of the sink I screwed one end of the hose to the faucet and Fed the hose out the window. Laid it down across my yard in a zigzag pattern and then back through the window into the sink. I could turn on that cold faucet and fill that sink with scalding hot water, hotter than my hot water heater would produce, it was literally steaming. If you waited 5 minutes, the water in the garden hose is already back up to that temperature even though you just displaced it with cold tap water. So you could fill a big deep sink with 5 minutes of solar radiation And that hose wasn't even insulated. It was just laying out
@@Jamey_ETHZurich_TUe_Rulez⚠️ God has said in the Quran: 🔵 { O mankind, worship your Lord, who created you and those before you, that you may become righteous - ( 2:21 ) 🔴 [He] who made for you the earth a bed [spread out] and the sky a ceiling and sent down from the sky, rain and brought forth thereby fruits as provision for you. So do not attribute to Allah equals while you know [that there is nothing similar to Him]. ( 2:22 ) 🔵 And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful. ( 2:23 ) 🔴 But if you do not - and you will never be able to - then fear the Fire, whose fuel is men and stones, prepared for the disbelievers.( 2:24 ) 🔵 And give good tidings to those who believe and do righteous deeds that they will have gardens [in Paradise] beneath which rivers flow. Whenever they are provided with a provision of fruit therefrom, they will say, "This is what we were provided with before." And it is given to them in likeness. And they will have therein purified spouses, and they will abide therein eternally. ( 2:25 ) ⚠️ Quran
I enjoyed your video but can't for the life of me understand why you went through the math exercises of figuring out Ohms & Amps? I mean whatever your panels are putting out and whatever heat is produced by them is really all that's relevant at this point. You stick the heaters in the sand and see what you get, then you can scale accordingly. Maybe I just missed your point? Anyway, it was a good review on the math, I'm not throwing any shade, I just didn't understand why you'd take the time to bother since it didn't really matter to the experiment.
@@Jamey_ETHZurich_TUe_Rulez Quick lime (Calcium Oxide) can be used as "hygroscopic energy storage". Here's some fun math. According to wikipedia, 3.1 kg of Calcium Oxide could get you about 1 kw-hour of thermal energy. If you're house needs about 15 kw-hour per day of thermal energy in the winter, you would need 3.1 kg/kw-hour x 15 kw-hour/day x 90 days/winter = 4185 kg of Calcium Oxide for the winter. That's about 9.2 tons of Calcium Oxide!
Another power source in a emergency could be a generator(or a moped if that`s all there is using 12volt heater parts) running on Browns Gas(cheep version of Hydrogen) and gasoline vapours....
Nice concept, but a couple of remarks... -1- With the fan, a thermistor is a temperature dependent resistor. You meant to say a Peltier element/thermo-electric element. -2- Connecting solar panels directly to a resistor (heating element) does not use the panels at their best. You would need an MPPT controller. -3- The round cooktop element is rated for higher temperatures, which is what you need. The long water heater elements are made to heat water. At the much higher temperatures that you're using them now, they will not last long. -4- You're doing this experiment with lots of sunlight plus you didn't show the ambient outside temperature. So how would this work in winter with a lot less sunlight and below freezing temps? Please keep up these experiments, I;m curious how this scales up.
This could be effectively used as a bleed-off for excess power from a wind turbine during a high-wind day. It is not a reliable option as a direct radiant heater, but it might be good as a water heater supplement.
A “Sand Battery ” Never needs a Mppt controller to function from solar. This is a different beast to tackle. In this configuration. This is considered a “Power Over PV device” or P.O.P.D. for short. The only thing missing from this design is a Capacitor slightly oversized for the voltage of the Panel to balance the power input coming into the sand battery.
MPPT is only useful if you're trying to maintain a specific voltage as it will drop the current to maintain the most power it can for that given voltage. It wouldn't make any difference in a direct connect resistive load. You'll have the same power output either way in this scenario.
@@daniellapain1576 Do you happen to be in the EU? I seen that set-up with the cap SO much while traveling. Just small systems all over the property to power specific things.
Interestingly enough you will get more accuracy using math for that. The numbers of BTU’s put into the sand will be the BTUs you get out of the sand. So take your starting room temperature and that will show how how fast the BTUs come back out of the sand. The lower the ceiling the closer you will be to the eventual warm air. The smaller the room the less stuff to heat up and the fewer walls for heat to escape. So the temperature of his room will have very little to do with the temperature of any other room. There are to many variables.
What matters is amount of heat transferred. That can be determined by the other parameters captured. The temp rise is too dependent on the unique room features.
It is not going to make a room warm you are right. But emergency heat is for small spaces. Put this in a large closet and you will be much warmer. Or drape some sheets over a table and you will have a small enough space that this will increase the temperature more than 10 degrees.
You are kinda recreating the pathway already done. What you are ultimately going to reach is that the optimal way to do this is to insulate the sand box, which allows the temperatures to get much higher and be almost permanent, and then run water pipes through the sand that feeds out and heats a radiator. There is a company in Norway that has a sand battery the size of farm silo, which then distributes hot water to hundreds of homes for heating... in winter, in Norway...
@@Jamey_ETHZurich_TUe_Rulez This is so sketchy. If you have free solar panels then of course converting electricity to heat and then storing it in sand to use it, makes sense. But doing so by using solar heat collectors for heating water and storing it in a big vessel seems more effective in all ways.
@jclandram hen house not recommended. If the heat crashes at any time, the chickens will die suddenly. Happened a lot when people have lost heat in hen houses during the winter.
To get the most power from the solar panels match the resistance of the panels to the resistance of the heating element. David Poz has an excellent video and spreadsheet to do this. To continue the keep it simple concept, use a kitchen oven, connect direct to PV, keep voltage around 100v and bypass switches/thermostat for safety, leave door open, fill with bricks. When sun shines it heats room and bricks. At night hot bricks heat the room.
This how night storage heaters work, been around since the 60`s They are heated in the night time when electicity is cheaper (off peak) Needs a dual tarrif meter.
Excellent video presentation. I currently use my 4.6 kwp of solar pv to power my house via a standard grid-tied inverter. Then heat-up my old fashioned storage radiators through an Immersun unit, so that the rads / kettle / shower heater; only use just surplus electricity from the panels, rather than exporting such to the external grid. The old fashioned storage radiators in the UK are just basically heating elements inside a brick pile, with insulation around & then encased in a metal skin. A simple bi-metal thermostat limits the maximum temperature. This has worked so well for me since 2011 that my electricity bill is only about £40 pa. So I'm well pleased. However, in the potential event of SHTF, if the electricity grid goes down, then your direct routing of the DC from the panels would still be of considerable use. A simple sand battery is a great concept. Thank you for the video.
I`ve been thinking about utilising my storage heaters in the same way (although I was thinking about using 12/24v halogen bulbs in place of the heating elements inside the storage heaters, & maybe building my storage heaters up with more bricks, possibly using lead acid batteries, or supercapacitors as a buffer), my concern is the fact we can easily go days, & even weeks in the UK without seeing an ounce of sun during winter, so how does it work out in reality?
@@MrPabsUk I'll try & provide the best answer that I can by splitting it into 3 sections:- a). I can't see any net benefit to using halogen bulbs inside storage heaters. They are fairly expensive, their service life can be much shorter than the old existing heating elements that are probably already in situ. b). The 'more bricks' has considerable merit, as it would increase the heat storage capacity & cool-down more slowly. My caveat to this is that old storage heaters are encased in an insulation & a sheet metal skin. I've been thinking along this line myself for some years. However, I think that it would require a second & substantially larger number of bricks around an existing storage heater, then fit heat insulation material around them & for safety - to manufacture an addition sheet metal skin to encase the additional materials. NB. The (now) very old designs of storage radiators were 'fat / thick' in their design & had many more bricks inside than the modern, better insulated, thin & cosmetically attractive modern versions. c). Little sun in the winter; yup, no way out of this one other than spending maybe £50k on 5x Tesla Powerwall / batteries to store energy on better days & release that storage during the dull / overcast days. My solution, for what it's worth, is simply to change my lifestyle. I simply retreat into one room that I can only partially heat & mega insulate the 'person' rather than 'waste' heat warming the room. The rest of the house stays unheated & cold until the brightness / sun returns. I can do this by choice, as I now live on my own & am a tough old codger. However, there is no hope that a wife or children would put-up with that 'inconvenience', even remotely. My apologies for the loooong essay; but I thought your sensible comment deserved my attempt at a good answer. Regards, John.
thats cool, I have heard another story about using hot water solar panels and installing a huge underground water tank. Then route underfloor pipes to heat the floors. In the winter and summer the floor/earth is a large portion of why a house feels hot or cold.
Great Content...Great Idea...Forget all the Smarty McSmart Pants comments this concept is an awesome off grid solution for green houses, well houses, people houses etc etc...Bravo!!
I use a solar air heater which is about 4 ft x 4 ft and during winter when the outside daytime temperature is typically 25°F, the heater will deliver air at ~ 110°F for 6 hours during a sunny day. I prefer this because the only electrical component is a fan which is powered by a 25 watt solar panel. The solar air heater does not block a window - - it is leaning against the outside wall of the house. Of course, when the sun sets, that's the end of the warm air.
@@Bazza1968 Well, you people that live near the North Pole have fewer options. Of course, neither a solar air heater nor a solar sand battery will be of much use.
I can offer anyone my experience to add to the best outcome here. I hated a kettle of water on the stove last year to see if it works sufficiently keep the place comfortable. I then tried this same battery model. The sand did not collect the heat as efficiently as water. Also, the water out out steam in the air to humidify my living space. What a noticeable element of indoor comfort! That humidity adds to your sense of warmth, just like it adds to your misery in a cold damp environment. All the wood structures in the house appreciated it too. I hope this helps someone out!
That's because water has a wildly higher heat capacity than sand. Water has one of the highest heat capacities of any known non-exotic material, which is a huge part of why steam power is so effective.
I am confused that you said humidity is good for wood structures. Excessive humidity and condensation is the reason for wood mold/rot. During winter, humidity in warm indoor air, if allowed to migrate through wall cavity outside, might start condensing on the wood structures. Dew point for 20C/68F 50%RH air is 9C/48F. Humidity is good for you, optimally it's 50-55%. But it will rot and destroy the wooden structures if not controlled by a vapor barrier.
Nice video! Many solar systems have extra capacity that is throttled by solar chargers. I wonder if a water heater could be powered by directing extra productivity to the heater. In wind powered systems, there is usually a "dump load," which solar doesn't need. But, what if a solar electric system were designed to use a water heater as a dump load.
In hvac applications traditionally, resistive loads are wired parallel while control circuits or switches are wired in series if you had your heating elements wired in parallel, you would have less resistance, and therefore be able to dump more amps into your sand with less voltage drop assuming your panels can handle the amp draw
When doing the math, keep in mind that the resistance of the elements go up with temperature. The power rating is typically AT the temperature it is to be run at. The stove element gets far hotter than the water heater element (since the water heater elements are supposed to be in water). In the old days, you could measure the resistance of an incandescent bulb, then power it up and measure the current at its rated voltage - the resistance when on and hot, was at least triple its cold resistance and took under a second or so to reach.
I wonder if those who use a wood stove to heat the home could set the sand in containers on top of the wood stove to absorb heat and then carry to bedrooms to keep bedrooms warm at night?! Effective use in a greenhouse?
I think you will find the electric elements can reach higher than. A rocket stove might reach the higher temperatures but I think you will want to pipe outside air to the stove so it doesn’t suck out all the warm air in the room.
Yes, and/or also heating large DRY rocks works well also. Be sure rocks are dry in the middle or may explode from steam, but a bucket of hot rocks is a blessing at times too. Back in the day they heated an iron pan on a stick kind of thing to run under the bed covers to make jumping in more pleasant, I keep a few new bricks on hand for this when it -30c for a couple weeks on end... throw them under the cover and warm that mattress, yes please! lol I looooove my wood stove, I'll never be without one. For your greenhouse do look into Rocket Mass Heaters.
It is much more effective to just put a pot of water on a wood stove. Sand doesn't have anywhere near the heat capacity of water. Sand's only real advantage is that you can heat it up to 1000 degrees F without a massive pressure vessel.
Ecofan in sand, cool (haha). My thought right away seeing you have about 800 watts of panels, is that you should be seeing more like 700+ watts out vs 137w to the stove element and 250w to the water heater elements. Putting the water heating elements in parallel would be a simple and hotter config. Figures: Panel config - "max power resistance": One panel: Vmp 34, Imp 11.62, "Rmp" 2.92 ohms Two series: Vmp 68, Imp 11.62, "Rmp" 5.84 ohms Two parallel: Vmp 34, Imp 23.24, "Rmp" 1.46 ohms Resistor-heater element config: One *stove element - R= 38 ohms Two in series - R= 76 ohms Two in parallel - R= 19 ohms One *water heater element - R=10.8 ohms Two series - 21.6 ohms Two parallel - 5.4 ohms So I'd try two panels in series (5.84 ohms "Rmp") with 2 water heater elements in parallel (5.4 ohms R). Since the element resistances were taken cold, they might change significantly (up) as observed in other comments. Of the resistance elements on hand, 2 water heater elements is the closest match
I've seen these a lot on UA-cam recently. However, there are some issues that are not often considered. Comparing the sand battery to a hot water storage, the water storage almost always wins. While it is true that the sand battery stores higher temperatures. Due to the difference in specific heat, you need to heat an equal volume of sand to roughly 215 degrees celsius to reach the same energy storage capacity as 85c water. The issue with sand is its low thermal conductivity. This is a benefit when you want to store energy long term (seasonal storage), as the colder outer layer forms its own insulation around the hot inner core, but when you want it short term as shown here, it is a serious limitation as you can't quickly pull out the heat. Most people falsely interpret the sand staying hot for longer as a benefit, but when you want to use that heat it is most certainly not. Where sand batteries shine is at very high temperatures close to its 1500 melting point. In this case, your energy density compared to water is superior while the high temperature mitigates some of the issues surrounding thermal conductivity. The issue is, for residential purposes it's quite difficult to cheaply engineer such a solution that can handle the high temperatures. Therefore, doing the same but then with a water tank is a more practical solution: heat the water to 85-90c and you can easily take the heat out due to the high thermal conductivity. Additionally, you can use a heat pump to warm up water to such temperatures, using much less electricity to reach the same thermal energy storage in kWh. Heat pumps cannot output temperatures as required for sand batteries. Just another consideration to keep in mind!
Awesome! Thank you for this build and for showing the math calculations. Now I can keep my cat warm in the garden shed without paying $250/mo for grid electric. Also appreciate the links to solar resources for larger projects. Keep up the good work!
Intereating experiment. Maybe you could just put the sand in a metal bucket and heat it outside over a small wood fire, then when the bucket gets to the desired temp just carry it inside for the night. I once visited a castle in Poland. Under the king’s bedroom was a large chamber filled with boulders. They kept a fire going in that chamber which heated the boulders, and the residual heat would rise heating the kings bedroom.
Ideas: As water is a better conductor how to make a huge metal box with sands and water. just to make sand wet. 2. Box filled with river stones and water. Stones should release temperature longer. Maybe could work one of these
When you introduce these topics, it's helpful to remind new viewers how to experiment safely around voltages over 50V and power levels over 100W. (fuses, protecting wires from physical damage, etc) It can't hurt to repeat a safety message on each video.
Agreed. 70VDC can kill you. Two issues with DC, since the voltage never drops to zero (as with AC) your muscles never get a chance to release. Also when you disconnect the power the arc does not stop for the same reason. You could put the panels in parallel and add a third hot water element also in parallel and you would be a lot closer or the max power point. And the lower voltage would be a lot safer
@@toddmarshall7573there's old electricians, and bold electricians. If you've worked with live snakes you know never to turn your back on them either. Call it cowardice but us old guys call it living to see another day.
If using this in an emergency, I would try and reduce the space i need to heat, like a using it in a tent, or some makeshift shelter using blankets, etc.
Can nest tents in winter too. Like a blind or ice fishing tent with a smaller tent inside to insulate and precondition surrounding air. Will reduce condensation on sleeping tent too.
I have 800 watts solar going into similar size pot as this one shown. It gets hot over 250 degrees c. I live in Ireland so our Sunshine is far less than other parts of the world. I think their interesting and fun to do. I have a shunt type voltage meter on there to measure wattage and I'm getting about 1.3kwh per day out of my panels which are hung vertically so not ideal. Realistically that's not enough power to heat a room on its own though but it does help. Depending where you are,you might get better results. I took the element out of an old storage heater (240v) for my set up, best to string the panels in seris when using that kind of an element it's just the way it works. Have a go it's fun.
All you need to know to do this calculation is square footage of the space to be heated/cooled, surface area of the outside walls, net R-value of the insulation of the walls and ceiling, and the delta-T desired to meet expected temperature.
This is a good idea. I would advice not to use Wago connectors so close to heating elements like that especially for actual use. Very high temperature insulation like fiber glass and silicone should be used. There are screw terminals and spade connectors. Just use those. That's why they're there, anyway. The Wago connectors may have survived, but all that heat will likely cause the plastic to warp and stuff weakening the connectors and causing them to fail over time.
My small 4'x8' DIY greenhouse thanks you for this idea and video. I have a small greenhouse heater that is plugged into more extension cords after extension cords than I'm proud to admit, especially as a firefighter 😬😬. But this is a great idea that I am gonna replace that with ASAP
You can also make a HHO cell and do a Sand tube Burner. About the same Out put, but faster. Bury Sand tube HHO heater device, in Sand battery, Presto. Cheap, clean science. A wanna suggest, you dial in the, Sonic Fire Extinglisher device, 22o mhz cancel's FIRE. As seen here on YT, this could save your life, that Kid that firgured this out, is Under appreciated and his dicovery isn't used as much as it Should be.. Sound can also alter other thing's, see "Sound versus Science" music video and take this to your Cheif. I tried to get CA Fire to inpliment, but the Science was too, Science for them.. Make it work where your at, and get this Science moving into, Everyday use... Everything, vibrate's at different Frequecy's, Sound can Cut and it used in Surgury..
I think this is a great DIY emergency heat source. One thought with the fan is to fabricate a stake that's mounted to the fan base to gather the heat from deeper in the sand battery. The fan is designed to gather the heat from a Woodstove surface, so if it gets the heat from deeper down, it may transfer it up faster to the base. This is a project I now want to play with as winter is just about here. Lol
Interesting to use photovoltaics which are about 30% efficient at the moment to provide low grade heat when solar thermal solutions such as heating water or a transfer fluid directly are 70% efficient.
I just bought 10- 30W, 24VDC heater pads and a 24V Temperature Controller to build a heater for my outside battery bank. I used a 120cuft deck box to put them in and it holds 12- 12V Group 27 batteries. The Temperature Controller is only rated for 10A, so I will only use 8 of the pads. These pads are supposed to get to 370 degrees, so I will have to watch where I put them, I do not want to melt any lead-acid batteries. The pads have adhesive backs, so I will attach them to a piece of 1/4" aluminum deck plate. The controller will be mounted outside of the battery deck box so that no relay contact arcing will ignite any gasses from the batteries. I may try putting the 2 leftover pads into some sand for an area heater.
This video definitely got you a subscription from me. This is an interesting idea, but one thing you need to be aware of is that resistance rises as the temperature of the heating element goes up. That helps the element to current regulate at its rated voltage. If you want a fun experiment with an extreme example of this phenomenon, measure the cold resistance of an incandescent light bulb. A 12v 194 license plate automotive tag light bulb will have about 2 ohms cold (which would make you think it would flow 6A at 12V, or 72W) , but it will only flow about 0.3A (about 3.6W) when the fillament is glowing white hot.
The general advantage of these kinds of materials starts when you are able to dump MUCH more energy into them (as they'll happily exceed 1000C without causing the quartz sand any issues for example) whilst insulating them (e.g. aerogel) so they *gradually* release a small portion of the total energy over a Much longer time period (i.e. overnight).
keep in mind that heaters intended for water are usually not rated to "run dry" as they rely on the max water temp of 100c (212F) to stop the internals from melting themselves.
Using a solar diverter controller would make this way more effective. In the UK we have devices like the Myenergi Eddi, the Immersun, and others, which can run direct electric resistive heater elements directly.
I'm currently looking at how to heat a 12x12 greenhouse I just built. I was considering a similar method as you but using a 55 gal drum of water. Heating the water would be via an element (or two) as well as the natural warming by the sun. The problem I have is estimating how long the heat will last vs. outside temp. I like the sand method a bit better as the pots can be on the ground and don't need to be in the sunlight. Additionally the sand can get a lot hotter than water and therefore store more heat. I may try a hybrid of both methods. Looking forward to your additional research.
I think wiring your heating elements in parallel (5ohms) instead of series (20ohms) would help you see a lot more wattage flow from your series panels (7ohms) due to better impedance matching?
Ya I had mentioned wiring them in parallel but I was just thinking 10.8 ohms but ya your math is better but just 1 element would be double the power he is getting since he has plenty of solar but parallel might be to low resistance but i guess it would pull the voltage down but it might be more power still
This is an awesome idea!!! My brain flooded with all kinds of applications. You could embed these in an insulated block of concrete with air tubes going through it, so you could extract the heat when it's needed. Instead of a fan you could use convection, just have a small temperature actuated shutter.
I'm not the sharpest tool in the shed, but would it be possible to modify this to provide passive air circulation? Like putting this pot inside a bigger pot, then drill holes on the bottom of the bigger pot, add some clay columns to serve as channels so cold air gets sucked in between the layers as hot rises and escapes through the top, heating up the small room faster.
For sure, I think there are a bunch of different ways to better pull the heat out of the center of the pot. I will most likely do a few more iterations a one will for sure have some type of channel or duct running through the middle 👍.
Aluminum buried in the sand . Cans or Aluminum foil baking trays cut up and arranged within the sand to disperse the heat . Leaving some sticking out the top for the Peltier fan draw heat from
This is a great idea, especially for excess solar power in the winter. I'm planning an off grid cabin build and this is a perfect option for those sunny days the battery is fully charged and I want to capture the solar energy in thermal mass. Heck. I'd fill a whole wall with sand. 😅
The heat would be instant where as this is longer lasting cause sand will cool down slowly. The peak of the heat from the light will be higher so your room would get to a peak temp and as long as your insulation is good it would remain but I doubt most old homes have great insulation so sand may be better over long periods of time.
It depends on what you already have installed; we hooked up a water heater to consume excess PV capacity which would other be lost - as we are off grid. Using a 4.5KW tank, but at 120v it consumes ~1KW easily provided by our inverter. Timer let's it run 5hrs per day....
Yes, but you'd have to build something to concentrate the heat, like mirrors on a tube or something. Panels are cheap enough that cost wise, solar panels are easier. If you wanted to get fancy, you could make some insulated black boxes (with a glass face) with coiled tubing and a couple panels to power a heat pump to concentrate that heat down to a sand battery.
@@andrewt9204 having seen that project be built and rebuilt multiple times in multiple ways, a panel connected directly to a heating element is much cheaper
@@andrewt9204 all you need is an insulated box with as black as you can get paint and a coil of hose to run oil or water through. Covered in insulated glass if possible. No mirrors needed.
I have a few questions please!? what happens if you are under powered. do it fail to heat or just weaken suitably. what happens if you have lots of solar on on and then the sun blazes and your pushing a bit too much energy into a coil? do it self protect/limit in some way? what exactly is the mechanism that is making the element heat and not the wires, it is simply the element needs to be the highest resistance part of the circuit? How hot in real terms can those various elements generally get? i know the sand is safe at 600c but some high end can go to 1500c but concerned about understanding the elements. having to jump in feet first and cart before horse really out of neccesity, so these questions help shape my understanding quick sharp like a primer.
@@everydaysolar You missed the most important part of the direct solar calculations, the source vs load impedence. In short it's abount matching voltage and amps of both your load and source by using the resistance. As resistance is R = V/I. Said in another way Resistance is a ratio of voltage to amps, if you match this you will archieve peak efficency. You calcualted the load impedence, which is 3.84 ohms or 10.8 ohms (or 21.6 ohms). However you should talk about source impedence of your solar panel, at maxium power point one solar panels is 34V @ 11.62 amps. Using V/I = R, you can calculate a single panel would be 2.9ohms, two panels in series will be 5.85 ohms, or two panels in parallel would be 1.46 ohms. Maximum efficence will be gained by matching you source and load impedence. (Series resistance formular is R + R, and parallel is 1/R1 + 1/R2 = 1/Rtotal) For example your two water heater elements would work much better if they were in parallel. eg 1/10.8 + 1/10.8 = 1/5.4, 5.4 ohms (load) is far closer to the source 5.85 ohms, than the series of 21.6 ohms. Or if you ran your solar panels in parallel with the two cook top element in parallel, you source impedence would be 2.92 ohms (34 / 23.2 = 1.46) and load would be (1/3.84 + 1/3.84 = 1.92) Hope this give you more to talk about on the subject of direct solar.
First time finding your channel (not sure how UA-cam figured out I needed this). I have been trying to figure out an economical / easy way to keep my crawlspace above freezing. I have been looking at so many options. Today I watched a video on a rocket mass heater with copper tubing to heat a water mass, I like this much better. Thanks!
As a science experiment this is great. Fun to watch. The best method for heating via solar is a passive approach using the greenhouse effect to trap solar energy inside your house and storing it in thermal mass like the new 'net zero' homes do. The efficiency loss of using this solar panel approach isn't even worth considering for home owners as you'll get better tangible results upping the R-value of home insulation, replacing regular windows with triple pane, installing a heat pump, etc. I would assume using solar panels to power a heat pump system would be the best efficiency 'bang for your buck'. Great video by the way. It was enjoyable to see this experiment in action.
I plan on doing something similar for round 2 testing with a heat fan sitting on top of the aluminum or copper strips to help distribute the heat around the room.
My house has a oil tank underneath the stairs for when it used oil heating. It has since been disabled and my house is all electric. You just gave me an idea on how to use that tank.
If I was going to use it for Emergency heat, I would have a coil of copper tubing on the outer perimeter of the pot. But I would also have the pot lined with aluminum foil to keep the heat in better. Then I would circulate fluid through the tubing to a radiator to allow it to escape into the room. And you can turn on the pump only when the heat is needed.
Using the sun to heat a thermal mass is a great idea. Build a masonry heater in your home. Plant trees for the sun to help grow, for decades. Harvest other trees, preferrably those that have already died, to burn in the masonry heater. During an emergency, your entire home stays just as warm as it did previously. Your math showed ~750wh of energy stored in the pot full of sand. That is not enough energy, in any form, to keep you or your house warm during a cold winter day. You would have to scale that to a much larger solution...like a masonry heater.
We looked at a home a couple years back with a huge custom made masonry heater between the kitchen and living room. It was awesome and even had a lounge on one side to lay down on the warm surface. Pretty cool.
@@everydaysolar - They are expensive and take up a sizable amount of square footage in a home, but the warmth given off by a large thermal mass is better than any type of heat source that uses convection. Radiation and conduction are much more efficient and do a better job of making a person feel warm. Could you build a large, spread out, sand battery inside a home and use electricity from solar to heat it? :)
Back in the 80’s (I think) I was designing and building houses, building rules changed and we were required to have energy calculations for the buildings, some of the factors were, square foot, type if insulation, window square footage, heat source, north south orientation, and thermal mass. The thermal mass was interesting as it was calculated from items such as tile, brick, stone, items that were solid and would collect heat or cold and slowly release those temperatures back into the room. I would find it interesting to compare a system using solar panels to produce electricity which is the converted to heat by the element vs a thermal mass which is in direct line of view of the sun. It seems like there would be a large loss of energy converting the solar panel energy, wire power drop, heat element inefficiency.
That is an awesome idea! It eliminates the need to buy expensive batteries and inverters! Stove elements would be easy enough to find at the dump. Here in Canada it would be a cheap way to bring some extra heat into your home.
I have a setup like yours already with 2 large cooktop elements in parallel with 120v ac from my inverter in a 6 gallon metal bucket, 1 of them near the bottom & the other about halfway up. I put a thermostat on it to cut it off at 550 degrees but without it, It got up to 700 degrees. After shutting it off in the morning it still had 200 degrees remaining by the time I restarted it late afternoon.
curious to know how much of a difference this can make in the winter on heating bills. As others have mentioned, also using bricks in an old oven or cast iron stove might also work well.
There is a simpler option: the stones are heated red hot in a fire, then placed in an iron bucket and brought into the room. Warmth is guaranteed until the morning.
Did exactly this in fall cub scout (tent) camping when the night temps dropped well below freezing. Heated a "head sized" stone in the fire, wrapped it in multiple towels (to not burn myself) & took it inside sleeping bag with me. Based this on stories my parents told of heating bricks & tucking them under the quilts in the horse sled for the trip to town in their youth.
Your idea requires you to keep harvesting wood for the fire. When you get a lot older, you'll appreciate the heat generated by photovoltaic or photo-thermal panels. But, the idea of heating stone to a red hot temperature is a good one. You can do that with solar too.
Cool project, I have been looking at 12v air/water mass heating systems and soil warming wires from solar/lifepo4 batteries for a small cold frame to keep it from freezing overnight in the winter but never thought about a sand battery/direct mass heating for a small space.
Why not eliminate the 25% efficient solar cells and the heat wasted in the connecting cables by putting the pot of sand directly in the sun? Also, I think your fan is powered by peltier junction semiconductors that produce electricity when heated, and not by a thermistor.
Hey Dennis, thanks for the correction on the Peltier Module 👍. Even though there is an efficiency loss through the solar cells, wires, connectors, etc., we are able to take the increased surface area of the panels as compared to just the sand and clay pot surface.
I've wondered for a while if you could use something like this to keep energy for rapid heating an indoor sauna. Usually you have to wait a while after turning on a sauna for the heater to get the room up to temperature. If you put a sand battery under a bench so it's quite large, and run some radiator piping through it you could dump excess solar power in to it (instead of exporting), then when you want to use your sauna you have a small pump push some liquid through the radiator piping to a radiator in the room. Along with the sauna heater you'd be able to rapidly heat the room and use less energy (since sauna heaters are usually 8-15kw or so). Then I just think about lugging enough sand around to fill in a box under a bench to save a few pennies per sauna use and shudder...
Not a good idea, except if your room is dry with a humidity below 50%. Water evaporation has a cooling effect. Better put closed bottles around. If you want to increase thermal mass, put stones+sand. Or oil. Or just water in a hermetic boiler/radiator.
This a cool setup for people that already have a few solar panels in their garage for an RV or camping. Not sure it would be worth going out to buy panels just for this.
1. Don't do this with solar panels. PV is not good enough. Use solar radiators/ solar heaters since they are around 80% efficient compaired to pv at 17-20%. 1kW solar can then give 800w heat.
awesome video, this is the first video ive watched from you. i enjoyed the technical/methodical data. (who would click this vid to just"skip the math"? 😁)
This makes me wonder about floor heat. The ones that I've installed {I'm an electrician and just install the controllers) tend to pull about 15A @ 240VAC. I wonder how well it would work if you made a bed sized area maybe a foot deep that you could sleep on top of.
What is the thermodynamic most efficient way to heat it all up, would adding some copper wires into the sand help move the heat away to more parts of the sand faster, increasing the temp diff from the sand around the heating element and the element itself? I mean, all the energy goes in to the sand, but I feel like the rate of dispersion has an impact (and on how effective you can marshall it out with the fans after?) would be interesting to test in a sealed room with thermometers on timelapse for a whole day
I'm interested to see if an infrared heating panel might be a better option, the panels will need to charge a 200ah battery instead. I don't know how one of them panels will last heating up a room but if its well insulated I'm sure it will keep a room warm at night when its coldest temps.
Would it be helpful to preheat the sand in a tray, a thin layer covered with a black covering, outside in the sun, passively heating away prior to placing in the container. A thin layer would absorb the solar energy faster than a container that would require the sun rays to penetrate through more material.
3 questions. How hot will the bottom get? Enough to start a fire? What about off gassing from the sand, is it burning or creating carbon monoxide or worse?
Basically those are night storage heaters. For safety I would use the ready build ones. Yes you need a converter, but this also gives you MPPT, which increases your output. Insulation ensures that you only get heat out when needed. More power plus more safety plus more comfort... for sure worth spending some bucks.
Would help to know the BTUs or some measurement for comparison for example to an ordinary heater like an oil filled portable electric radiator that can run at 600, 800 or 1500 watts to heat a room. So would this just be a hand warmer, warm the space under a desk to be able to sit with a degree of comfort, keep a room above the freezing point or heat a closed closet to have a small space to sit & be comfortable for some time period.
Nice! I'd be interested in a study on the optimal volume/ mass of sand for the power and heating period length so that the system could be fine tuned to store and release for the whole non powered part of the 2 hour cycle. Obvs this would change throughout the year unless combined with a wind powered generator
The specific heat capacity of sand is between 0.180 and 0.191 BTU/lb-°F. Where as the specific heat for water is 1 BTU/lb-°F. I guess the advantage is sand can get hotter where as water is limited to 212F unless pressurized. I know it is not cool but I believe a water heater to be a better heat battery than a sand heater battery.
I am a big fan of passive solar and I like the idea of using sand as a battery to store heat. It would be very helpful to see this test conducted in the winter where the outside temp is recorded as well as the inside temp of the room from start to finish. Thanks for the idea, sand is a much better thermal mass than water or stone. I only wish I still owned my solar workshop so that I could play with this.
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Why would you use electricity when the thermal energy from the Sun is far greater?
You're going to take electricity and turn it into heat when the Sun is already producing heat
Just have a container of liquid sitting outside. Painted black encased in glass and run that liquid in the house
Years ago I lived in an old house and we had hot water to all the sinks except the laundry room sink. It was just cold water
I bought a 75-ft black hose, just a garden hose and a connector so it would fit on the faucet of the sink
I screwed one end of the hose to the faucet and Fed the hose out the window. Laid it down across my yard in a zigzag pattern and then back through the window into the sink.
I could turn on that cold faucet and fill that sink with scalding hot water, hotter than my hot water heater would produce, it was literally steaming.
If you waited 5 minutes, the water in the garden hose is already back up to that temperature even though you just displaced it with cold tap water.
So you could fill a big deep sink with 5 minutes of solar radiation
And that hose wasn't even insulated. It was just laying out
@@Jamey_ETHZurich_TUe_Rulez⚠️ God has said in the Quran:
🔵 { O mankind, worship your Lord, who created you and those before you, that you may become righteous - ( 2:21 )
🔴 [He] who made for you the earth a bed [spread out] and the sky a ceiling and sent down from the sky, rain and brought forth thereby fruits as provision for you. So do not attribute to Allah equals while you know [that there is nothing similar to Him]. ( 2:22 )
🔵 And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful. ( 2:23 )
🔴 But if you do not - and you will never be able to - then fear the Fire, whose fuel is men and stones, prepared for the disbelievers.( 2:24 )
🔵 And give good tidings to those who believe and do righteous deeds that they will have gardens [in Paradise] beneath which rivers flow. Whenever they are provided with a provision of fruit therefrom, they will say, "This is what we were provided with before." And it is given to them in likeness. And they will have therein purified spouses, and they will abide therein eternally. ( 2:25 )
⚠️ Quran
I enjoyed your video but can't for the life of me understand why you went through the math exercises of figuring out Ohms & Amps? I mean whatever your panels are putting out and whatever heat is produced by them is really all that's relevant at this point. You stick the heaters in the sand and see what you get, then you can scale accordingly. Maybe I just missed your point? Anyway, it was a good review on the math, I'm not throwing any shade, I just didn't understand why you'd take the time to bother since it didn't really matter to the experiment.
@@Jamey_ETHZurich_TUe_Rulez Quick lime (Calcium Oxide) can be used as "hygroscopic energy storage". Here's some fun math. According to wikipedia, 3.1 kg of Calcium Oxide could get you about 1 kw-hour of thermal energy. If you're house needs about 15 kw-hour per day of thermal energy in the winter, you would need 3.1 kg/kw-hour x 15 kw-hour/day x 90 days/winter = 4185 kg of Calcium Oxide for the winter. That's about 9.2 tons of Calcium Oxide!
Another power source in a emergency could be a generator(or a moped if that`s all there is using 12volt heater parts) running on Browns Gas(cheep version of Hydrogen) and gasoline vapours....
My cats would love that. It's a litter box and it's made of warm.
😛
the smell though
@@cameralife8Keeps away intruders. 🎉
Burned butt syndrome
They could lounge in the litter box. Oh wait.....
Nice concept, but a couple of remarks... -1- With the fan, a thermistor is a temperature dependent resistor. You meant to say a Peltier element/thermo-electric element. -2- Connecting solar panels directly to a resistor (heating element) does not use the panels at their best. You would need an MPPT controller. -3- The round cooktop element is rated for higher temperatures, which is what you need. The long water heater elements are made to heat water. At the much higher temperatures that you're using them now, they will not last long. -4- You're doing this experiment with lots of sunlight plus you didn't show the ambient outside temperature. So how would this work in winter with a lot less sunlight and below freezing temps? Please keep up these experiments, I;m curious how this scales up.
This could be effectively used as a bleed-off for excess power from a wind turbine during a high-wind day. It is not a reliable option as a direct radiant heater, but it might be good as a water heater supplement.
A “Sand Battery ” Never needs a Mppt controller to function from solar. This is a different beast to tackle. In this configuration. This is considered a “Power Over PV device” or P.O.P.D. for short. The only thing missing from this design is a Capacitor slightly oversized for the voltage of the Panel to balance the power input coming into the sand battery.
good in spring when there is minus 10C
MPPT is only useful if you're trying to maintain a specific voltage as it will drop the current to maintain the most power it can for that given voltage. It wouldn't make any difference in a direct connect resistive load. You'll have the same power output either way in this scenario.
@@daniellapain1576 Do you happen to be in the EU? I seen that set-up with the cap SO much while traveling. Just small systems all over the property to power specific things.
The main thing missing is temperatures in the room! Also some graphs with temp over time will be nice (both room temp and sand temp.).
Interestingly enough you will get more accuracy using math for that. The numbers of BTU’s put into the sand will be the BTUs you get out of the sand.
So take your starting room temperature and that will show how how fast the BTUs come back out of the sand.
The lower the ceiling the closer you will be to the eventual warm air.
The smaller the room the less stuff to heat up and the fewer walls for heat to escape.
So the temperature of his room will have very little to do with the temperature of any other room. There are to many variables.
Yes, that would have been a great addition to the testing.
What matters is amount of heat transferred. That can be determined by the other parameters captured. The temp rise is too dependent on the unique room features.
That little thing isn't big enough to make any difference in room temperature.
It is not going to make a room warm you are right. But emergency heat is for small spaces. Put this in a large closet and you will be much warmer. Or drape some sheets over a table and you will have a small enough space that this will increase the temperature more than 10 degrees.
You are kinda recreating the pathway already done. What you are ultimately going to reach is that the optimal way to do this is to insulate the sand box, which allows the temperatures to get much higher and be almost permanent, and then run water pipes through the sand that feeds out and heats a radiator. There is a company in Norway that has a sand battery the size of farm silo, which then distributes hot water to hundreds of homes for heating... in winter, in Norway...
Why using sand then? Water itself has 5 times more thermal mass than sand
@@airattoz water boils at low temperature and creates pressure issues. Sand can go well above 1000 degrees without changing volume.
@@PeterSedesse How can you safely transfer that heat to water? It will evaporate, or you have to use high pressure with risk of explosion
@@airattoz as I said, there is a company in Norway that does this exact thing for an entire town.
@@Jamey_ETHZurich_TUe_Rulez This is so sketchy. If you have free solar panels then of course converting electricity to heat and then storing it in sand to use it, makes sense. But doing so by using solar heat collectors for heating water and storing it in a big vessel seems more effective in all ways.
This might be nice for a mini greenhouse outside in winter
Or a hen house.
@jclandram hen house not recommended. If the heat crashes at any time, the chickens will die suddenly. Happened a lot when people have lost heat in hen houses during the winter.
To get the most power from the solar panels match the resistance of the panels to the resistance of the heating element. David Poz has an excellent video and spreadsheet to do this. To continue the keep it simple concept, use a kitchen oven, connect direct to PV, keep voltage around 100v and bypass switches/thermostat for safety, leave door open, fill with bricks. When sun shines it heats room and bricks. At night hot bricks heat the room.
I'd never hear the end of it from my wife if I did that. What about when you need to cook?
@@GOPRepubliklanPretty sure the idea is to get a second, old, half-broken oven for cheap / free and do it!
Cooking is going to be hard after you cut the connection ends off your burners.
Post a link
This how night storage heaters work, been around since the 60`s They are heated in the night time when electicity is cheaper (off peak) Needs a dual tarrif meter.
Excellent video presentation. I currently use my 4.6 kwp of solar pv to power my house via a standard grid-tied inverter. Then heat-up my old fashioned storage radiators through an Immersun unit, so that the rads / kettle / shower heater; only use just surplus electricity from the panels, rather than exporting such to the external grid. The old fashioned storage radiators in the UK are just basically heating elements inside a brick pile, with insulation around & then encased in a metal skin. A simple bi-metal thermostat limits the maximum temperature.
This has worked so well for me since 2011 that my electricity bill is only about £40 pa. So I'm well pleased.
However, in the potential event of SHTF, if the electricity grid goes down, then your direct routing of the DC from the panels would still be of considerable use. A simple sand battery is a great concept.
Thank you for the video.
I`ve been thinking about utilising my storage heaters in the same way (although I was thinking about using 12/24v halogen bulbs in place of the heating elements inside the storage heaters, & maybe building my storage heaters up with more bricks, possibly using lead acid batteries, or supercapacitors as a buffer), my concern is the fact we can easily go days, & even weeks in the UK without seeing an ounce of sun during winter, so how does it work out in reality?
@@MrPabsUk I'll try & provide the best answer that I can by splitting it into 3 sections:-
a). I can't see any net benefit to using halogen bulbs inside storage heaters. They are fairly expensive, their service life can be much shorter than the old existing heating elements that are probably already in situ.
b). The 'more bricks' has considerable merit, as it would increase the heat storage capacity & cool-down more slowly. My caveat to this is that old storage heaters are encased in an insulation & a sheet metal skin. I've been thinking along this line myself for some years. However, I think that it would require a second & substantially larger number of bricks around an existing storage heater, then fit heat insulation material around them & for safety - to manufacture an addition sheet metal skin to encase the additional materials. NB. The (now) very old designs of storage radiators were 'fat / thick' in their design & had many more bricks inside than the modern, better insulated, thin & cosmetically attractive modern versions.
c). Little sun in the winter; yup, no way out of this one other than spending maybe £50k on 5x Tesla Powerwall / batteries to store energy on better days & release that storage during the dull / overcast days. My solution, for what it's worth, is simply to change my lifestyle. I simply retreat into one room that I can only partially heat & mega insulate the 'person' rather than 'waste' heat warming the room. The rest of the house stays unheated & cold until the brightness / sun returns.
I can do this by choice, as I now live on my own & am a tough old codger. However, there is no hope that a wife or children would put-up with that 'inconvenience', even remotely.
My apologies for the loooong essay; but I thought your sensible comment deserved my attempt at a good answer. Regards, John.
Just build a firebox under an enclosed pile of bricks. Simple, if you prepare ahead of time.@@johnkay4701
thats cool, I have heard another story about using hot water solar panels and installing a huge underground water tank. Then route underfloor pipes to heat the floors. In the winter and summer the floor/earth is a large portion of why a house feels hot or cold.
Love it.
Getting 10 hours of heating would be the golden point for me.
I'm guessing greater sand mass would be the key for slower heat release.
Great Content...Great Idea...Forget all the Smarty McSmart Pants comments this concept is an awesome off grid solution for green houses, well houses, people houses etc etc...Bravo!!
I use a solar air heater which is about 4 ft x 4 ft and during winter when the outside daytime temperature is typically 25°F, the heater will deliver air at ~ 110°F for 6 hours during a sunny day. I prefer this because the only electrical component is a fan which is powered by a 25 watt solar panel. The solar air heater does not block a window - - it is leaning against the outside wall of the house. Of course, when the sun sets, that's the end of the warm air.
A well-insulated room should retain the heat for a while, though. But that's not an option for everyone
What about when there's a blanket of cloud? Here at 57N in Scotland it's rarely sunny, ever!!
@@Bazza1968 Well, you people that live near the North Pole have fewer options. Of course, neither a solar air heater nor a solar sand battery will be of much use.
@@n3evpn3evp Ever look at a map? Scotland is not anywhere near the NP and how are you getting this solar warm air INTO your house?
@@AIRDOODOO Yeah if the outside daily temperature is "typically 25F" that's colder than where I am!!
I can offer anyone my experience to add to the best outcome here. I hated a kettle of water on the stove last year to see if it works sufficiently keep the place comfortable. I then tried this same battery model. The sand did not collect the heat as efficiently as water. Also, the water out out steam in the air to humidify my living space. What a noticeable element of indoor comfort! That humidity adds to your sense of warmth, just like it adds to your misery in a cold damp environment.
All the wood structures in the house appreciated it too. I hope this helps someone out!
That's because water has a wildly higher heat capacity than sand. Water has one of the highest heat capacities of any known non-exotic material, which is a huge part of why steam power is so effective.
I am confused that you said humidity is good for wood structures. Excessive humidity and condensation is the reason for wood mold/rot. During winter, humidity in warm indoor air, if allowed to migrate through wall cavity outside, might start condensing on the wood structures. Dew point for 20C/68F 50%RH air is 9C/48F. Humidity is good for you, optimally it's 50-55%. But it will rot and destroy the wooden structures if not controlled by a vapor barrier.
@@chameleonh you make prescient points. I did not say excessive moisture is good for wood. I was addressing a lack of moisture.
STOP HATING WATER!! It’s ESSENTIAL for LIFE ITSELF!!!
@@bretsk2500You’re TOTALLY WRONG!!!!
Nice video! Many solar systems have extra capacity that is throttled by solar chargers. I wonder if a water heater could be powered by directing extra productivity to the heater. In wind powered systems, there is usually a "dump load," which solar doesn't need. But, what if a solar electric system were designed to use a water heater as a dump load.
In hvac applications traditionally, resistive loads are wired parallel while control circuits or switches are wired in series if you had your heating elements wired in parallel, you would have less resistance, and therefore be able to dump more amps into your sand with less voltage drop assuming your panels can handle the amp draw
When doing the math, keep in mind that the resistance of the elements go up with temperature. The power rating is typically AT the temperature it is to be run at. The stove element gets far hotter than the water heater element (since the water heater elements are supposed to be in water). In the old days, you could measure the resistance of an incandescent bulb, then power it up and measure the current at its rated voltage - the resistance when on and hot, was at least triple its cold resistance and took under a second or so to reach.
In electrical engineering with the bulb, it is called cold shock.
Dimming incandescent with a soft start on dim then ramp up to brighter and dim to low before turning off makes them last 100X longer //
I wonder if those who use a wood stove to heat the home could set the sand in containers on top of the wood stove to absorb heat and then carry to bedrooms to keep bedrooms warm at night?!
Effective use in a greenhouse?
I think you will find the electric elements can reach higher than. A rocket stove might reach the higher temperatures but I think you will want to pipe outside air to the stove so it doesn’t suck out all the warm air in the room.
Yes, and/or also heating large DRY rocks works well also. Be sure rocks are dry in the middle or may explode from steam, but a bucket of hot rocks is a blessing at times too.
Back in the day they heated an iron pan on a stick kind of thing to run under the bed covers to make jumping in more pleasant, I keep a few new bricks on hand for this when it -30c for a couple weeks on end... throw them under the cover and warm that mattress, yes please! lol
I looooove my wood stove, I'll never be without one.
For your greenhouse do look into Rocket Mass Heaters.
you might want to search for "rocket mass heaters"
It is much more effective to just put a pot of water on a wood stove. Sand doesn't have anywhere near the heat capacity of water. Sand's only real advantage is that you can heat it up to 1000 degrees F without a massive pressure vessel.
With a copper rod placed down in the center of the pot would be even more effective but yes it could absolutely work 👍
Ecofan in sand, cool (haha). My thought right away seeing you have about 800 watts of panels, is that you should be seeing more like 700+ watts out vs 137w to the stove element and 250w to the water heater elements. Putting the water heating elements in parallel would be a simple and hotter config. Figures:
Panel config - "max power resistance":
One panel: Vmp 34, Imp 11.62, "Rmp" 2.92 ohms
Two series: Vmp 68, Imp 11.62, "Rmp" 5.84 ohms
Two parallel: Vmp 34, Imp 23.24, "Rmp" 1.46 ohms
Resistor-heater element config:
One *stove element - R= 38 ohms
Two in series - R= 76 ohms
Two in parallel - R= 19 ohms
One *water heater element - R=10.8 ohms
Two series - 21.6 ohms
Two parallel - 5.4 ohms
So I'd try two panels in series (5.84 ohms "Rmp") with 2 water heater elements in parallel (5.4 ohms R).
Since the element resistances were taken cold, they might change significantly (up) as observed in other comments. Of the resistance elements on hand, 2 water heater elements is the closest match
I've seen these a lot on UA-cam recently. However, there are some issues that are not often considered. Comparing the sand battery to a hot water storage, the water storage almost always wins. While it is true that the sand battery stores higher temperatures. Due to the difference in specific heat, you need to heat an equal volume of sand to roughly 215 degrees celsius to reach the same energy storage capacity as 85c water. The issue with sand is its low thermal conductivity. This is a benefit when you want to store energy long term (seasonal storage), as the colder outer layer forms its own insulation around the hot inner core, but when you want it short term as shown here, it is a serious limitation as you can't quickly pull out the heat. Most people falsely interpret the sand staying hot for longer as a benefit, but when you want to use that heat it is most certainly not.
Where sand batteries shine is at very high temperatures close to its 1500 melting point. In this case, your energy density compared to water is superior while the high temperature mitigates some of the issues surrounding thermal conductivity. The issue is, for residential purposes it's quite difficult to cheaply engineer such a solution that can handle the high temperatures. Therefore, doing the same but then with a water tank is a more practical solution: heat the water to 85-90c and you can easily take the heat out due to the high thermal conductivity.
Additionally, you can use a heat pump to warm up water to such temperatures, using much less electricity to reach the same thermal energy storage in kWh. Heat pumps cannot output temperatures as required for sand batteries. Just another consideration to keep in mind!
Awesome! Thank you for this build and for showing the math calculations. Now I can keep my cat warm in the garden shed without paying $250/mo for grid electric. Also appreciate the links to solar resources for larger projects. Keep up the good work!
I'm curious if using salt would change your thermal retention. Another step in a possible experiment.
Intereating experiment. Maybe you could just put the sand in a metal bucket and heat it outside over a small wood fire, then when the bucket gets to the desired temp just carry it inside for the night.
I once visited a castle in Poland. Under the king’s bedroom was a large chamber filled with boulders. They kept a fire going in that chamber which heated the boulders, and the residual heat would rise heating the kings bedroom.
in the old days, they used to heat up beach rocks and put in the foot of the bed
I don’t think most people should be carrying a 50 pound bucket of hot sand around their house.
But if you happen to have servants, go ahead! ;)
Ideas: As water is a better conductor how to make a huge metal box with sands and water. just to make sand wet.
2. Box filled with river stones and water. Stones should release temperature longer.
Maybe could work one of these
When you introduce these topics, it's helpful to remind new viewers how to experiment safely around voltages over 50V and power levels over 100W. (fuses, protecting wires from physical damage, etc) It can't hurt to repeat a safety message on each video.
Yes please I'm hesitant to try this out until I understand the safety more.
Agreed. 70VDC can kill you. Two issues with DC, since the voltage never drops to zero (as with AC) your muscles never get a chance to release. Also when you disconnect the power the arc does not stop for the same reason.
You could put the panels in parallel and add a third hot water element also in parallel and you would be a lot closer or the max power point. And the lower voltage would be a lot safer
Thank you Chicken Little.
@@toddmarshall7573there's old electricians, and bold electricians. If you've worked with live snakes you know never to turn your back on them either. Call it cowardice but us old guys call it living to see another day.
Significant shock and fire risks here
Very interesting application of solar to thermal conversion! Really brings several concepts together. Thank you.
If using this in an emergency, I would try and reduce the space i need to heat, like a using it in a tent, or some makeshift shelter using blankets, etc.
Smart, thanks for the feedback!
Yeah could actually be very viable then
Can nest tents in winter too. Like a blind or ice fishing tent with a smaller tent inside to insulate and precondition surrounding air. Will reduce condensation on sleeping tent too.
I would like to see a long term analysis to keep a shed warmish over the winter.
That would be interesting, thanks for the feedback!
I wonder if you’re gonna inspire a lot of critters to try and get in there haha!
I have 800 watts solar going into similar size pot as this one shown.
It gets hot over 250 degrees c.
I live in Ireland so our Sunshine is far less than other parts of the world.
I think their interesting and fun to do.
I have a shunt type voltage meter on there to measure wattage and I'm getting about 1.3kwh per day out of my panels which are hung vertically so not ideal.
Realistically that's not enough power to heat a room on its own though but it does help.
Depending where you are,you might get better results.
I took the element out of an old storage heater (240v) for my set up, best to string the panels in seris when using that kind of an element it's just the way it works.
Have a go it's fun.
Put heating element and thermal fan in sand at safe distance ( as to not burn out thermistor), heat room as necessary.
All you need to know to do this calculation is square footage of the space to be heated/cooled, surface area of the outside walls, net R-value of the insulation of the walls and ceiling, and the delta-T desired to meet expected temperature.
This is a good idea. I would advice not to use Wago connectors so close to heating elements like that especially for actual use. Very high temperature insulation like fiber glass and silicone should be used. There are screw terminals and spade connectors. Just use those. That's why they're there, anyway. The Wago connectors may have survived, but all that heat will likely cause the plastic to warp and stuff weakening the connectors and causing them to fail over time.
What sands have you considered ??? Those little fans would need a hotter base to perform. Like our big wood burning heater
My small 4'x8' DIY greenhouse thanks you for this idea and video. I have a small greenhouse heater that is plugged into more extension cords after extension cords than I'm proud to admit, especially as a firefighter 😬😬. But this is a great idea that I am gonna replace that with ASAP
Use a medium sized steel trash can filled with sand it gives you a lot more volume to hold the heat
You can also make a HHO cell and do a Sand tube Burner.
About the same Out put, but faster.
Bury Sand tube HHO heater device, in Sand battery, Presto.
Cheap, clean science.
A wanna suggest, you dial in the, Sonic Fire Extinglisher device, 22o mhz cancel's FIRE.
As seen here on YT, this could save your life, that Kid that firgured this out, is Under appreciated and his dicovery isn't used as much as it Should be..
Sound can also alter other thing's, see "Sound versus Science" music video and take this to your Cheif.
I tried to get CA Fire to inpliment, but the Science was too, Science for them..
Make it work where your at, and get this Science moving into, Everyday use...
Everything, vibrate's at different Frequecy's, Sound can Cut and it used in Surgury..
I think this is a great DIY emergency heat source. One thought with the fan is to fabricate a stake that's mounted to the fan base to gather the heat from deeper in the sand battery. The fan is designed to gather the heat from a Woodstove surface, so if it gets the heat from deeper down, it may transfer it up faster to the base. This is a project I now want to play with as winter is just about here. Lol
Interesting to use photovoltaics which are about 30% efficient at the moment to provide low grade heat when solar thermal solutions such as heating water or a transfer fluid directly are 70% efficient.
I just bought 10- 30W, 24VDC heater pads and a 24V Temperature Controller to build a heater for my outside battery bank.
I used a 120cuft deck box to put them in and it holds 12- 12V Group 27 batteries.
The Temperature Controller is only rated for 10A, so I will only use 8 of the pads.
These pads are supposed to get to 370 degrees, so I will have to watch where I put them, I do not want to melt any lead-acid batteries.
The pads have adhesive backs, so I will attach them to a piece of 1/4" aluminum deck plate.
The controller will be mounted outside of the battery deck box so that no relay contact arcing will ignite any gasses from the batteries.
I may try putting the 2 leftover pads into some sand for an area heater.
This video definitely got you a subscription from me. This is an interesting idea, but one thing you need to be aware of is that resistance rises as the temperature of the heating element goes up. That helps the element to current regulate at its rated voltage.
If you want a fun experiment with an extreme example of this phenomenon, measure the cold resistance of an incandescent light bulb. A 12v 194 license plate automotive tag light bulb will have about 2 ohms cold (which would make you think it would flow 6A at 12V, or 72W) , but it will only flow about 0.3A (about 3.6W) when the fillament is glowing white hot.
The general advantage of these kinds of materials starts when you are able to dump MUCH more energy into them (as they'll happily exceed 1000C without causing the quartz sand any issues for example) whilst insulating them (e.g. aerogel) so they *gradually* release a small portion of the total energy over a Much longer time period (i.e. overnight).
keep in mind that heaters intended for water are usually not rated to "run dry" as they rely on the max water temp of 100c (212F) to stop the internals from melting themselves.
Yup, fire hazard (at much )higher wattage, best to blow air over nichrome wire in tube and make simple heat exchanger
Definitely NO fire hazard, what about electric oven? Thermal conductivity of air is much much lower then sand.
@@Martin-gn9xi different heating elements in an oven.
Remember they are runing at a fraction of their rated power 250w vs 5000w
@shaynegadsden stop trying to cloud the issue with facts
Using a solar diverter controller would make this way more effective. In the UK we have devices like the Myenergi Eddi, the Immersun, and others, which can run direct electric resistive heater elements directly.
I'm currently looking at how to heat a 12x12 greenhouse I just built. I was considering a similar method as you but using a 55 gal drum of water. Heating the water would be via an element (or two) as well as the natural warming by the sun. The problem I have is estimating how long the heat will last vs. outside temp. I like the sand method a bit better as the pots can be on the ground and don't need to be in the sunlight. Additionally the sand can get a lot hotter than water and therefore store more heat. I may try a hybrid of both methods. Looking forward to your additional research.
This is the way. 55 gallon of water passively heated with a pool heater and a tiny dc pump
A cheap chinese deisel heater would work really well for this application
Interesting. Thanks for posting. 13:40 The hot sand and pot _do function_ as a radiant heat source, regardless of heat transfer via convection.
💯
I love this! This will be a perfect project once my wife and I buy a house.
I think wiring your heating elements in parallel (5ohms) instead of series (20ohms) would help you see a lot more wattage flow from your series panels (7ohms) due to better impedance matching?
I squared power dissapation.....
Ya I had mentioned wiring them in parallel but I was just thinking 10.8 ohms but ya your math is better but just 1 element would be double the power he is getting since he has plenty of solar but parallel might be to low resistance but i guess it would pull the voltage down but it might be more power still
But the lower your voltage, the larger your wire gauge must be per unit of distance from source of power
This is an awesome idea!!! My brain flooded with all kinds of applications. You could embed these in an insulated block of concrete with air tubes going through it, so you could extract the heat when it's needed. Instead of a fan you could use convection, just have a small temperature actuated shutter.
ideally you would want this in a big block of concrete so it heat up during the day and cools down at night.
I'm not the sharpest tool in the shed, but would it be possible to modify this to provide passive air circulation? Like putting this pot inside a bigger pot, then drill holes on the bottom of the bigger pot, add some clay columns to serve as channels so cold air gets sucked in between the layers as hot rises and escapes through the top, heating up the small room faster.
For sure, I think there are a bunch of different ways to better pull the heat out of the center of the pot. I will most likely do a few more iterations a one will for sure have some type of channel or duct running through the middle 👍.
Trombe wall
Aluminum buried in the sand . Cans or Aluminum foil baking trays cut up and arranged within the sand to disperse the heat . Leaving some sticking out the top for the Peltier fan draw heat from
interesting idea
@@everydaysolaryes please
This is a great idea, especially for excess solar power in the winter. I'm planning an off grid cabin build and this is a perfect option for those sunny days the battery is fully charged and I want to capture the solar energy in thermal mass. Heck. I'd fill a whole wall with sand. 😅
Wouldn't it be more effective to capture the heat of the sun than converting the light to electricity to produce heat?
The heat would be instant where as this is longer lasting cause sand will cool down slowly. The peak of the heat from the light will be higher so your room would get to a peak temp and as long as your insulation is good it would remain but I doubt most old homes have great insulation so sand may be better over long periods of time.
It depends on what you already have installed; we hooked up a water heater to consume excess PV capacity which would other be lost - as we are off grid. Using a 4.5KW tank, but at 120v it consumes ~1KW easily provided by our inverter. Timer let's it run 5hrs per day....
Yes, but you'd have to build something to concentrate the heat, like mirrors on a tube or something. Panels are cheap enough that cost wise, solar panels are easier.
If you wanted to get fancy, you could make some insulated black boxes (with a glass face) with coiled tubing and a couple panels to power a heat pump to concentrate that heat down to a sand battery.
@@andrewt9204 having seen that project be built and rebuilt multiple times in multiple ways, a panel connected directly to a heating element is much cheaper
@@andrewt9204 all you need is an insulated box with as black as you can get paint and a coil of hose to run oil or water through. Covered in insulated glass if possible. No mirrors needed.
I have a few questions please!?
what happens if you are under powered. do it fail to heat or just weaken suitably.
what happens if you have lots of solar on on and then the sun blazes and your pushing a bit too much energy into a coil? do it self protect/limit in some way?
what exactly is the mechanism that is making the element heat and not the wires, it is simply the element needs to be the highest resistance part of the circuit?
How hot in real terms can those various elements generally get?
i know the sand is safe at 600c but some high end can go to 1500c
but concerned about understanding the elements.
having to jump in feet first and cart before horse really out of neccesity, so these questions help shape my understanding quick sharp like a primer.
Also, you look like Cobbs Pond from Frontier. ever thought about actor or stunt double!? :D
Great concept for a video, thank you for doing what most of us wouldn't try ourselves!
Thanks so much for the feedback and support 👍
@@everydaysolar You missed the most important part of the direct solar calculations, the source vs load impedence.
In short it's abount matching voltage and amps of both your load and source by using the resistance. As resistance is R = V/I. Said in another way Resistance is a ratio of voltage to amps, if you match this you will archieve peak efficency.
You calcualted the load impedence, which is 3.84 ohms or 10.8 ohms (or 21.6 ohms).
However you should talk about source impedence of your solar panel, at maxium power point one solar panels is 34V @ 11.62 amps. Using V/I = R, you can calculate a single panel would be 2.9ohms, two panels in series will be 5.85 ohms, or two panels in parallel would be 1.46 ohms.
Maximum efficence will be gained by matching you source and load impedence. (Series resistance formular is R + R, and parallel is 1/R1 + 1/R2 = 1/Rtotal)
For example your two water heater elements would work much better if they were in parallel. eg 1/10.8 + 1/10.8 = 1/5.4, 5.4 ohms (load) is far closer to the source 5.85 ohms, than the series of 21.6 ohms.
Or if you ran your solar panels in parallel with the two cook top element in parallel, you source impedence would be 2.92 ohms (34 / 23.2 = 1.46) and load would be (1/3.84 + 1/3.84 = 1.92)
Hope this give you more to talk about on the subject of direct solar.
First time finding your channel (not sure how UA-cam figured out I needed this). I have been trying to figure out an economical / easy way to keep my crawlspace above freezing. I have been looking at so many options. Today I watched a video on a rocket mass heater with copper tubing to heat a water mass, I like this much better. Thanks!
You bet, best of luck on your project!
Nice video! So, don't need inverter at all. Just connect directly to Solar Panels! Nice!
Yepper!
As a science experiment this is great. Fun to watch. The best method for heating via solar is a passive approach using the greenhouse effect to trap solar energy inside your house and storing it in thermal mass like the new 'net zero' homes do. The efficiency loss of using this solar panel approach isn't even worth considering for home owners as you'll get better tangible results upping the R-value of home insulation, replacing regular windows with triple pane, installing a heat pump, etc. I would assume using solar panels to power a heat pump system would be the best efficiency 'bang for your buck'.
Great video by the way. It was enjoyable to see this experiment in action.
if you slide flat copper down into sand standing above top of sand the heat will radiate longer. great for greenhouse thats what we use this for
I plan on doing something similar for round 2 testing with a heat fan sitting on top of the aluminum or copper strips to help distribute the heat around the room.
I agree. I tried a 120v water heater element and the steel turned blue. Guessing it wouldn't last long. A wet sand seemed to help.
My house has a oil tank underneath the stairs for when it used oil heating. It has since been disabled and my house is all electric. You just gave me an idea on how to use that tank.
Brilliant
Then run some coopertubes trough it, you will have a great waterheater.
I don't think you would ever rid your home of the smell of heating oil if you did so.
If I was going to use it for Emergency heat, I would have a coil of copper tubing on the outer perimeter of the pot. But I would also have the pot lined with aluminum foil to keep the heat in better. Then I would circulate fluid through the tubing to a radiator to allow it to escape into the room. And you can turn on the pump only when the heat is needed.
I give you a very big large giant thumbs up because it was a good video very good experiment thank you
Thanks for the feedback and support
Great video. I would have liked to now what the temps were about a foot from the pot and maybe 2 feet.
I will be doing an update video with some mods and will include a little more on the heat being given off to the room.
Using the sun to heat a thermal mass is a great idea. Build a masonry heater in your home. Plant trees for the sun to help grow, for decades. Harvest other trees, preferrably those that have already died, to burn in the masonry heater. During an emergency, your entire home stays just as warm as it did previously. Your math showed ~750wh of energy stored in the pot full of sand. That is not enough energy, in any form, to keep you or your house warm during a cold winter day. You would have to scale that to a much larger solution...like a masonry heater.
We looked at a home a couple years back with a huge custom made masonry heater between the kitchen and living room. It was awesome and even had a lounge on one side to lay down on the warm surface. Pretty cool.
@@everydaysolar - They are expensive and take up a sizable amount of square footage in a home, but the warmth given off by a large thermal mass is better than any type of heat source that uses convection. Radiation and conduction are much more efficient and do a better job of making a person feel warm. Could you build a large, spread out, sand battery inside a home and use electricity from solar to heat it? :)
@@jasonbroom7147 you could.
There's a lot of sand in the concrete used in Underfloor heating systems
Back in the 80’s (I think) I was designing and building houses, building rules changed and we were required to have energy calculations for the buildings, some of the factors were, square foot, type if insulation, window square footage, heat source, north south orientation, and thermal mass. The thermal mass was interesting as it was calculated from items such as tile, brick, stone, items that were solid and would collect heat or cold and slowly release those temperatures back into the room.
I would find it interesting to compare a system using solar panels to produce electricity which is the converted to heat by the element vs a thermal mass which is in direct line of view of the sun. It seems like there would be a large loss of energy converting the solar panel energy, wire power drop, heat element inefficiency.
That is an awesome idea! It eliminates the need to buy expensive batteries and inverters! Stove elements would be easy enough to find at the dump. Here in Canada it would be a cheap way to bring some extra heat into your home.
Thanks for your video but I would like to know how warm the room get with those elements if you use water.
How to make safer around kids. This is a great idea.
They'll figure it out quickly.
If they survive an electrical shock.
@@markmcculloch2570 yeah, some won't make it.
I am waitin to see can you calculate the energy except Watts for example in other units or not
Rondo Heat Battery is new technology. Upto 1,500⁰C temperatures.
Good video. 👍
You could cook a cake with this!
I have a setup like yours already with 2 large cooktop elements in parallel with 120v ac from my inverter in a 6 gallon metal bucket, 1 of them near the bottom & the other about halfway up. I put a thermostat on it to cut it off at 550 degrees but without it, It got up to 700 degrees. After shutting it off in the morning it still had 200 degrees remaining by the time I restarted it late afternoon.
that's actually, really impressive. for some situations, this would work great, like trivially putting heat in a greenhouse.
I think the greenhouse is the best use case mentioned thus far 👍👍
curious to know how much of a difference this can make in the winter on heating bills. As others have mentioned, also using bricks in an old oven or cast iron stove might also work well.
There is a simpler option: the stones are heated red hot in a fire, then placed in an iron bucket and brought into the room. Warmth is guaranteed until the morning.
Did exactly this in fall cub scout (tent) camping when the night temps dropped well below freezing.
Heated a "head sized" stone in the fire, wrapped it in multiple towels (to not burn myself) & took it inside sleeping bag with me.
Based this on stories my parents told of heating bricks & tucking them under the quilts in the horse sled for the trip to town in their youth.
Your idea requires you to keep harvesting wood for the fire. When you get a lot older, you'll appreciate the heat generated by photovoltaic or photo-thermal panels. But, the idea of heating stone to a red hot temperature is a good one. You can do that with solar too.
Cool project, I have been looking at 12v air/water mass heating systems and soil warming wires from solar/lifepo4 batteries for a small cold frame to keep it from freezing overnight in the winter but never thought about a sand battery/direct mass heating for a small space.
Why not eliminate the 25% efficient solar cells and the heat wasted in the connecting cables by putting the pot of sand directly in the sun?
Also, I think your fan is powered by peltier junction semiconductors that produce electricity when heated, and not by a thermistor.
Hey Dennis, thanks for the correction on the Peltier Module 👍. Even though there is an efficiency loss through the solar cells, wires, connectors, etc., we are able to take the increased surface area of the panels as compared to just the sand and clay pot surface.
I've wondered for a while if you could use something like this to keep energy for rapid heating an indoor sauna. Usually you have to wait a while after turning on a sauna for the heater to get the room up to temperature.
If you put a sand battery under a bench so it's quite large, and run some radiator piping through it you could dump excess solar power in to it (instead of exporting), then when you want to use your sauna you have a small pump push some liquid through the radiator piping to a radiator in the room. Along with the sauna heater you'd be able to rapidly heat the room and use less energy (since sauna heaters are usually 8-15kw or so).
Then I just think about lugging enough sand around to fill in a box under a bench to save a few pennies per sauna use and shudder...
Might want to try comparing results with dry sand vs. wet sand.
Not a good idea, except if your room is dry with a humidity below 50%. Water evaporation has a cooling effect. Better put closed bottles around. If you want to increase thermal mass, put stones+sand. Or oil. Or just water in a hermetic boiler/radiator.
This a cool setup for people that already have a few solar panels in their garage for an RV or camping.
Not sure it would be worth going out to buy panels just for this.
1. Don't do this with solar panels. PV is not good enough.
Use solar radiators/ solar heaters since they are around 80% efficient compaired to pv at 17-20%.
1kW solar can then give 800w heat.
I'd like to include a set up like this in my passive solar greenhouse. Specifically to warm the water in my reservoir. What do you think?
awesome video, this is the first video ive watched from you. i enjoyed the technical/methodical data. (who would click this vid to just"skip the math"? 😁)
Would that get hot enough to make a Stirling engine practical - even if only to power a fan?
This makes me wonder about floor heat. The ones that I've installed {I'm an electrician and just install the controllers) tend to pull about 15A @ 240VAC. I wonder how well it would work if you made a bed sized area maybe a foot deep that you could sleep on top of.
What is the thermodynamic most efficient way to heat it all up, would adding some copper wires into the sand help move the heat away to more parts of the sand faster, increasing the temp diff from the sand around the heating element and the element itself? I mean, all the energy goes in to the sand, but I feel like the rate of dispersion has an impact (and on how effective you can marshall it out with the fans after?) would be interesting to test in a sealed room with thermometers on timelapse for a whole day
What about using bbq volcanic lava rocks to add? along with cooper wiring pipes ?Along side the sand in heating or raising the temperature
Continuing with the added water, would damp sand be more efficient than wet sand, assuming water helps at all.
question? Making a sand battery, is it best to compact the sand or just leave it loose?
At the beginning you said you would like to see how long it would hold heating. Well how long?
With the home HVAC off in a room. What's a wall thermometer reading in the room over time.
Very, very good explanation, indeed! Thank you very much from Portugal.😀
I'm interested to see if an infrared heating panel might be a better option, the panels will need to charge a 200ah battery instead. I don't know how one of them panels will last heating up a room but if its well insulated I'm sure it will keep a room warm at night when its coldest temps.
Could you do this with underfloor heating in a concrete slab?
Would it be helpful to preheat the sand in a tray, a thin layer covered with a black covering, outside in the sun, passively heating away prior to placing in the container. A thin layer would absorb the solar energy faster than a container that would require the sun rays to penetrate through more material.
3 questions. How hot will the bottom get? Enough to start a fire?
What about off gassing from the sand, is it burning or creating carbon monoxide or worse?
How would perlite, vermiculite, or ashes perform for this application? Seems like it’d be lighter in weight than sand.
Basically those are night storage heaters. For safety I would use the ready build ones. Yes you need a converter, but this also gives you MPPT, which increases your output. Insulation ensures that you only get heat out when needed.
More power plus more safety plus more comfort... for sure worth spending some bucks.
Do you have a google sheet of the data or a temperature graph over time? I would love to see it.
Would help to know the BTUs or some measurement for comparison for example to an ordinary heater like an oil filled portable electric radiator that can run at 600, 800 or 1500 watts to heat a room. So would this just be a hand warmer, warm the space under a desk to be able to sit with a degree of comfort, keep a room above the freezing point or heat a closed closet to have a small space to sit & be comfortable for some time period.
I'd be curious if adding water to the sand would make the battery any more efficient or would it reduce the sand to act more like water?
I'm wondering if this would be more efficiect using water instead of sand. I realize it may not hold the heat as long.
Nice! I'd be interested in a study on the optimal volume/ mass of sand for the power and heating period length so that the system could be fine tuned to store and release for the whole non powered part of the 2 hour cycle. Obvs this would change throughout the year unless combined with a wind powered generator
This would be cool for a small greenhouse. I wonder how much energy it holds?
The specific heat capacity of sand is between 0.180 and 0.191 BTU/lb-°F. Where as the specific heat for water is 1 BTU/lb-°F. I guess the advantage is sand can get hotter where as water is limited to 212F unless pressurized. I know it is not cool but I believe a water heater to be a better heat battery than a sand heater battery.
@@kevinmiller5467 also no risk of the sand freezing and breaking its container when power is low for long periods
Would a mixture of rocks and sand retain more heat?
Sand and melting salt, which is better effective of heat power?
You should have plotted time against temperature drop. How much heat was it actually radiating, at what distance?
I am a big fan of passive solar and I like the idea of using sand as a battery to store heat. It would be very helpful to see this test conducted in the winter where the outside temp is recorded as well as the inside temp of the room from start to finish. Thanks for the idea, sand is a much better thermal mass than water or stone. I only wish I still owned my solar workshop so that I could play with this.
My thought is to put them two or three under the crawlspace of your home in winter. Please tell me what you think?