Cool your home with zero electricity costs!
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- Опубліковано 13 чер 2024
- Solar cooling sounds like a contradiction in terms, but it could become a household phrase in a sustainable future, especially in off grid regions and developing nations because, if done properly, it could reduce your home temperature by almost 10 degrees Celsius (19 F) with no electrical input at all. Now a team at MIT has developed the most efficient system yet.
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Thatched roofs have a similar effect because the organic materials absorb humidity and water(when it rains)and like wise when hot they evaporate.This bring back vivid memories of my first trip abroad which was to New Guinea,one of the most humid countries in the world with an almost constant temperature of 30 C for any non native person this unbearable but the moment you enter one of the native huts which are heavily thatched you are instantly cool,it was amazing and a great relief.
Many of the world's 'problems' are self-inflicted. Most have obvious and known solutions.
- My household cooling system includes the natural reflectance and evaporative cooling provided by trees. Since it takes a long time to grow a tree, the best short-term alternative solution is to grow vines on the available building surfaces. While growing vines may increase building maintenance costs, vines should pay-back in terms of reduced cooling expenses and improved urban landscapes. In dense urban environments, one might also need to build porticoes over adjacent sidewalks to shield them from bird poop. But those porticoes would also shade the ground-floor walls and provide cooling via vine or turf coverings.
If you live in a house with a pier and beam foundation or a trailer house, you can use the underside of your house to make the condenser of your air conditioner work better.
I built a wooden box around my condenser that covered all but the top where the hot air comes out and the back side that was butted up against the house where I had opened up part of the foundation and installed a metal frame with a screen on it. That way when the condenser was running it would pull air out from under the house.
The box was painted white and had foil backed foam insulation installed on the inside to stop radiant heat from getting in.
The air coming in is from the shaded area under the house so it is cooler. Any moisture under the house cools the air off even more.
The benefit is that you have cooler air going through the condenser, the air circulating under the house helps dry it out so there is less chance of mold and fungus that could cause rot of the floor structure, the box helps protect the condenser unit from inclement weather better than standing out in the open, and if done properly the box can easily be moved out of the way if there is a need for servicing.
That's a good idea! But you have to make sure there is enough room from the outside wall of the condenser to the inside wall of the box to allow the air from the crawl space to enter the condenser as the fan pulls air in from the sides across the coil and forces it up.
I would love to see this!! I thought about something like this a few years ago, but could never find a way to put it into practice! Right on man!
Sounds good on the first look, but then... sorry, I need to debunk this.
1) Cooling 9 °C below ambient temperature would not be sufficient to conserve food, when in a climate where ambient temperature is around 30 °C or higher (for useful refrigeration, temperature would have be at 8 °C or below, inside the conservation unit). A wet blanket sitting in the shade with a little bit of wind blowing over it would have the same effect, but with much lower technical effort, and magnitudes cheaper. (And that method is actually how I keep my drinks cool when going to the beach in the summer.)
2) It still works mostly by evaporation of water. As you said, that's the last thing you want in a humid environment, where it will be much less efficient, due to the higher saturation of the surrounding air with water steam (which, by the way, is the reason it needs much less frequent replenishment of water in these environments). And in many areas, water is too scarce to use it for this purpose. Besides that, you'd need quite clean water, so the pores in the aerogel would not get clogged over time. I'm pretty sure that you'd actually need distilled water or similar purity, because even crystallising salts would clog the pores. But water of this purity is a) expensive and b) not even widely available in the industrialised countries.
3) The reflected radiation will only partly go out into space. Another part of it will be absorbed by the dust, the clouds, the water vapour, and the CO2 (and other gases) in the atmosphere. Even in a clear sky, there is still water steam and those gases. And a good part of the heat will be contained as the mentioned latent heat in the evaporated water, and thus, end up in the atmosphere, too.
In conclusion, I consider this "game changer" just an expensive and complicated way of putting a wet towel around your water bottle and placing it under a white sunshade.
@Daniel Meyers what is the specific IR wavelength of sunlight?
I think large unglazed clay pots full of water with a central water proof container to contain food to chill it was used centuries ago .
Water gradually leaked and evaporated on the outside of the clay pot to keep the inside of the pot cool .
Early American cars used swamp coolers
Homes in the American desert southwest often have (had) swamp coolers.
The ongoing drought and lack of water safe for these systems has become a problem.
@@jimurrata6785 The Ancient Persians Used Cooling Towers, Even Kept Ice.
Large canvass containers were and are used to provide cool water. The canvass allows a small amount of water to evaporate and cool the remainder.
Looks very promising! There must be some maintenance keeping the aerogel surface clean & avoiding mineral buildup in the hydrogel. Hopefully clever designs will minimize this.
Now it has become a habit to eagerly wait for the week's episodes. Love it
Delighted to hear it :-)
Absolutely agree! It's so great to have a little bite sized piece of positive AND informative news
@@JustHaveaThink nice technology but I got it cheaper, it's called hybrid offgrid PV with AC unit on load phase 😀
@@JustHaveaThink you should cite your sources. The IPCC has indicated low confidence about any changes in extreme weather events. The damn report said there might be some exceptions, I am also curious about how they picked their data to generate the latest hockey stick.
@@jakubjakub8494 Didn't Dave cover that in the video? It isn't even a question of what is cheaper, it's a question of what is more energy efficient. Currently you're using the energy from your PV to cool your home. But imagine you didn't even need an air conditioner. That is much more efficient. And that energy from your PV could be directed elsewhere. We've known about the effect of radiative cooling for millenia. India and Iran used it in conjunction with convective cooling to make ice with nightime temps that were just above freezing. We discovered how to enhance that in 2014 with the development of metamaterials with very high reflective index that actually provide a daytime cooling effect. But you do need the right conditions - no clouds and low humidity.
Fascinating-thanks. 👍
And yes here in Oz, (Brisbane) we have serious problems with heat and humidity- yet half the new houses around here have dark and even black roofs. Complete and utter Madness! The trouble is those dark roofs that our neighbours have heats our environment up as well.
We have a bright white (steel) colorbond roof and it makes an absolutely huge difference to our A/C requirements. (We also have 6.5kW of solar, and export a lot of power, even with airconditioning use.)
it would be even better to use metallic white paints on the roof; they have aluminium flakes embedded in the paint that reflects the radiation very effectively. So you get both: lower absorption and greater reflection. But unfortunately most of the commercial white paints look black in the IR range and that is sad.
Just seen 3 houses across from me have their roofs restored - in charcoal grey. Idiots. Where is Council stopping these practices?
@@elvirabarbour1444 your talking about the elected officials, they are bought and paid for by the fossil fuels industry. I would have thought anyone with three interconnected brain cells should have figured that out by now!
@@elvirabarbour1444 Yes!
Our bright white roof even on the hottest summer day can be walked on comfortably in bare feet at midday. Try that with a dark roof!
In the Queensland Wet Tropics white roofs end up grey due to algae which grows on them, then dies. Black Mountain near Cooktown, made of (black) granite boulders, illustrates this in nature.
Of course you would have to use distilled water, or the hydrogel would quickly turn into a block of salt and/or lime and need to be replaced frequently. It doesn't sound like either of these costs were factored into the calculation.
On the other hand you could bathe the condenser coils of a conventional AC unit with ground water or grey water at room temperature and still get a significant improvement in efficiency. Or evaporatively pre-cool it with the same fan that cools the condenser coils.
Since water with a low mineral content is expensive and necessarily produces a waste stream, it makes more sense to have a purge stream from the system. This will necessarily require the amount of water to go up, but not by too much. At least in the USA, the purge stream could be used for watering lawns or gardens.
My ground loop heat pump has a sytem to pull heat from the compressor and pre heat my domestic hot water. It produces 110 F heat all winter when the heat is on, not so much in the summer as we try to avoid AC.
@@robertstrader3267 Why do you try to avoid AC?
What you really need is something that just sprays water into a find mist then lets it drift down into a collection basin. with a drip-catcher screen above and a fan to circulate air. That will get you a very capable, low-cost evaporative cooling solution. It's so good, it's already commonplace. You don't see them in domestic AC - but they are on the roof of just about every sizable commercial or industrial building. It's the thing on the roof with the big fan.
@@vylbird8014 It seems to me that a fan would interfere with the 'drifting' of the mist.
Swamp coolers are a well known technology. They work great in arid locations but use a lot of water.
I only ring the bell on two UA-cam channels and this is one. well deserved
Thank you Daniel. I appreciate that :-)
Solar "chimneys" are pretty simple. Passively heating air above roof level in the "chimney" can draw air through the duct from the building below. This moves hot air out but needs a shady side from which to draw cooler air in, or one of these to cool the intake air passively as well.
This works well in dry regions, but I don't believe it translates to humid regions. Or even England, New England, Europe.
Evaporative cooling is popular in outback Australia though not in humid coastal areas where most of us live.
@@brad4013 I don't think Rusty is talking about evaporative cooling. This is a different technology.
@@brad4013 It's pretty good in areas of Cali where I lived, too. But too much humidity or temps over 100, like in the central valley of California, and it doesn't cool enough. When I lived in Arizona, people were putting in swamp cooler/refrigeration unit combo's. The swamp cooler was used until it got too hot. But on an older home, you had to replace the ducts to handle both. I don't remember why. But the newer homes had only refrigeration units at the time. Energy was cheaper then, though.
I have used aerogel blanket cut into strips to prevent thermal bridging in timber sole plates and ring beams when building with SIPs. It works well and is not expensive. I have built airtight buildings using passive ventilation with great success in a desert in Spain using this system.
@Ray Johnson Aerogel blanket looks like fibre glass insulation, but rigid. It is too expensive to use as a whole sheet, but very affordable if cut into strips. I have tested it in a SIP building in the Sahara Desert and in a lot of houses in a desert in Spain.
Not expensive?! What? Who is your supplier? It's ridiculously expensive wherever my clients try to source it (I'm an architect). It looked like being the wonder insulant that we were all seeking when it first came out commercially, but it is so fragile, and so damned expensive, that it has limited use on a building site.
@@MikeAG333 If you read what I said I only use aerogel as a gasket in the sole plate and ring beam to prevent thermal bridging. If you use space blanket it is not fragile, it has the same quality as fibre glass.
@@steverichmond7142 I did read what you read. You said it wasn't expensive.......but I'm telling you that you are factually incorrect: it is very expensive. Using a little bit of it only doesn't suddenly make it inexpensive.
"Space blanket" (so called "thinsulants"........multi-layered film composites, I presume you mean) can't be shown to work when tested in the normal way, so they have had to invent a test specifically. And they are almost never used properly, with a 25mm min void EACH SIDE, as required by the BBA and the manufacturers' literature, so they won't be working properly in practice either.
@@MikeAG333 Space blanket is a trade name. It is not multi-layered. You do not need 25mm each side... it's a detail in SIP construction. It has been fully certified by BBA. I come from the world of practical... I never use architects - they're all useless. I've built houses all over Europe and in many parts of the UK. They fully comply with building regs throughout Europe and UK. Airtight Building Technology came out of Canada. It has been taught in many colleges and universities.
If the aerogel is made of polyethylene, I would think that the UV in the sunlight would wreck it in a short time. All plastic degrades in the sun. I wonder what they’ve done about that?
Not only that but being a porous material, what about urban particulate material deposits over the surface of the aerogel? I assume it is a very delicate material, nearly impossible to clean using usual methods. UV is going to destroy it and if it doesn't, dust is going to clog it reducing overall efficiency. The general idea is pretty cool but needs to account for those issues.
The other problem is that most plastic is made from crude oil. Just like many other products that we use are also available because of crude oil and infact that computer or that television your watching is mostly made from crude oil . It is well known that there is over six hundred different products made from crude oil other than gas and diesel fuels or heating oil.
I have to agree here, aerogel is a problem.
@@joewilson2258 And that's why using oil for fuel is insane.
@@joewilson2258 polyethylene can be made from gas.
1:34 ...that's why I love your channel. You are asking the right questions. There are too many channels out there praising new technology and ideas which will never make it in the real practical world.
Yeah, that's something I like to think of as the "Popular Science Problem." Back in the 80s I used to read Popular Science magazine because it had lots of excited, sort of breathlessly written articles about the technologies that were going to save the world. It gave me an optimistic feeling about the future. But after reading it for years and seeing none of the technologies they talked about actually come out of the lab, I got tired of it and gave up on the magazine. That's the problem with futurism that doesn't take a balanced look at flaws and problems along with the promise of new ideas.
A question I am left with is what the role of the water actually is.
If evaporation is so negligible then so is the contribution to cooling.
@@Kevin_Street
Indeed.
It would be interesting to have a channel that look at _why_ promising ideas failed.
Maybe this could educate us all to be more skeptical of hype.
Placing solar panels over all my north facing roof (Australia) on both my house and shed dropped the temperature within the rooms directly under them. An unintentional BONUS!
IKR!
Thanks Dave again for your beautiful presentation. I guess its most effective on resource intensive single family homes?
Nice that you included the reference to the new book - looks excellent!
Yes, absolutely
How much are all these fancy stuffs going to cost? For majority of poor households in the hot regions, even a tiled roof house is a luxury. If you go to the equatorial poverty stricken regions, most common type of roofing is corrugated galvanised roof. Those are like tin cans, horribly hot in sunny days and freezing cold in rainy nights. But they are cheap, low maintenance and durable, just what the poor can only afford, just one more thing they have to endure, to have a shelter over their children heads.
@@madsam0320 Galvanised tin roofs are fine if there is a good insulation layer above the ceiling. Most also have a layer of insulation directly under the tin. They are good in hot climates because they lose their heat quickly at night. Clay or ceramic roof tiles do the opposite - they store heat and release it overnight. This is not what you want in a hot climate.
@@JustHaveaThink
What caused the 10's of millions of deaths in the late 1870's from heat?
When the world was a fraction of what it is today?
I'm not going to say it WASN'T from global warming...
...It wasn't.
did you already buy a copy of the carbon almanac? there is even a kids version of it.
Thanks Dave - make sure you check out the advancements made on closed-loop geothermal - if they are right about what is possible (one company is named EAVOR) then I think it is a a solution that is comparable in its potential to wind or solar.
I had a black bitumen area around our pik nik table, we’d spray water in a fine mist on said area ,the cooling effect through evaporation was substantial. Just water needed !!!
The system also probably needs distilled water because otherwise the hydro-gel would get full of mineral deposits, and making distilled water is also energy intensive.
Would be interesting to couple it with a water-from-air MOF system or something like that. That would produce pure water daily, and likely enough that the system's water wouldn't need to be manually filled except in more extreme conditions.
It seems like various combinations of the properties of these substances would still have energy savings. There are always tradeoffs in cost and efficiencies but even a 10% efficiency increase at lower cost adds up when huge numbers are involved. Sometimes the ideal is unrealized because of cost but the just good enough hits all the price points and efficiency gains. Hopefully the ideas presented begins a new thought process that allows these alternative avenues to open up.
I thought this video was gonna be about adiabatic cooling (cooling by water evaporation but requiring constant flow of water) but you managed to take us down a new road entirely! Well done!
A note about future proliferation of AC units: in the Netherlands, all new houses require a heat pump and at least some solar panels at the moment. A few years from now, I believe in 2025, gas heaters will be phased out and will be replaced by (hybrid) heat pumps. From living in a modern heat pump equipped house with floor heating and solar panels I’ve experienced that 1) my electricity bill is net negative (and that includes charging my EV!), and 2) the house is cooled very well even during heat strokes. This all but eliminates the need for AC. So innovative housing design and targeted clever legislation will not only curb the future need for AC but yield significant financial gains for the home owners of the future.
While you are indeed required to install heat pumps in new building developments in the Netherlands, some municipalities actually prohibit the installation of new solar PV systems, to prevent grid overloading. So while the Dutch government is finally making some progress towards phasing out fossil fuels, there are still some significant hurdles to overcome. Having worked with several electrical installers, I can also quote them on saying that it's generally not a good idea to generate more power than you consume yourself, to prevent grid overloading. Hopefully the government will urge the grid operators to upgrade the entire electrical grid to allow for more erratic power generation from household PV systems, and invest in grid scale energy storage, but I fear that may take some time yet.
@@Leon_Schuit Household PV cells do not have to be connected to the grid.
@@Leon_Schuit
People could be running their freezers to lower temperatures in times with surplus energy or plan washing, dishwashing and charging of EVs according to the weather.
We have to change habits and let go of how stuff "used to be".
The firm True Energy in Denmark have an app that takes over the charging of your EV.
You just tell the app when you need your car and how much you need for an emergency. The firm sell load balancing to the supply companies and split the loot with you 50-50.
Note that a “heatwave” in the netherlands is 3days over 30’Celsius or 5 over 25. Which is like winter in other parts of the world…
@@tjeers3098 if that's winter to a place then that place only experiences summer
I haven't read all the comments, so maybe I'm being redundant, but in addition to the limiting aspect of the air gel cost the mineral scale build-up from water evaporation would also require considerable maintenance.
Evaporation cooling is reduced in areas that have high dew point temperature.
100% passive insulated houses, apartment buildings, public buildings and cities. Why not? Strawbale or ricebale walls for structure and insulation.
i don't know if it obvious enough or not, rebuilding building is not cheap, it most likely on the expensive side too...
Great post my friend. I really appreciate hearing about new developments in this area.
Cheers Gef :-)
In poorer places one can also build cob houses. They are self heat regulating. Food and drinking water can also be stored in porous low fired clay cabinets outside. While this will not deep freeze, it certainly will keep your veggies fresh a lot longer. Cooling towers using evaporation cooling are over two thousand years old. There are indeed many approaches to cooling that have been around for a long, long time and do not need more technology than pumping water. Growing wine grapes over patios also greatly reduces heat and the same applies to many vining plants. That doubles the benefit to include getting food on top of cooling.
The Carbon Almanac is great! I recommend keeping a copy in your bathroom, so you can have something to read in small bites, rather than mindlessly scrolling your phone.
What worried me was you saying that the aerogel layer is very fragile. If it is exposed to air, and maybe walked on, can it withstand this?
and the price of areogel.... I think buying a pv and ac is cheaper+you have electricity
Another issue is that they use water. The water would have to be distilled so that salts don't accumulate in the panel and this might not be readily available.
Hard water would tend to accumulate solid deposits in the pores of the hydrogel.
@@Kevin_Street That's basically what Pete said.
I'm glad to know this technology is under development. I can see there may be applications where it could be practical. A downside that wasn't mentioned has to to with the most expensive component that the researchers have employed. That is the polyethylene aerogel. Nearly transparent polyethylene is notorious for its limited-time usefulness in direct sunlight. The UV rays breakdown the chemical structure making it brittle and finally turning it into a powder. Other alternative substitutes are likely to also be expensive. So the initial demonstrations and tests may not reveal another side to this story.
As usual, an excellent way to spend time. Thank you very much. You're an absolute star!
BTW, UA-cam didn't present me with this video today though I've been subscribed for a couple of years. I had to search it out manually. I remember you've had problems with this before and I just wanted to let you know it's happening again.
I had to do the same. I surmise the algorithm doesn't like the frequency at which he produces content. Quantity rewarded more than quality 😑
I don't think you really understood how this one worked tbh. To my eye it looks like the evaporative side of things is just a side hustle to the main way it works and shouldn't be focused on without a solid understanding of radiative cooling. The primary idea is that the aerogel layer forms an 'anti-greenhouse', that lets the IR radiation from the water gel layer below out, while also keeping the atmospheric glow out (sunlight is let through, but reflected back out). This 'primary mode' is cool but isn't that novel, which is why the paper doesn't dwell on it much. It is standard radiative cooling. Where this is novel is the construction. In particular it does away with any attempt at making a 'closed' system, which is where evaporation comes in. The construction is considerably simplified by the fact that water gel is both the radiator and the heat exchange fluid, while even a barrier to keep it in is unnecessary. As water evaporates it actually augments the cooling, so is a feature rather than a bug. Humidity tends to be higher at night than during the day, so this effect makes it function better when it wants to function best.
This is really cool and I am glad you showcased it, but I'm afraid I don't think you met your usual standard here (50% will be below average :P). Nighthawk in light has a good video on cooling paint, that also explains why pore size control is so critical to these sorts of things. Might be worth revisiting this, as it is super cool.
Thank you, I appreciate if you review, solar thermal adsorption, absorption, and amonia chillers. They are already in commercial use. And they use solar heat.
Thanks so much for another very informative video!
You're welcome!
Great video! Keep them coming.
Thank you so much, very easy to digest....
Mold and freezing will be issues as well as impact resistance for aero gel. Nobody puts that stuff outside. Should be an organic one anyway. There's hundreds of kinds.
Thirsty insects. Imagine all the micro-poops a swarm full of thirsty gnats would take. There is a paint that does the same thing. Knock off DIY version is doable. Tech Ingredients . Any dust or bad weather and it is ruined.
One problem with evaporating water is that you would need demineralise it which is energy intensive. Otherwise within few years your device will be clogged by boiler stone.
.. unless you're using rainwater.
The paper talks about keeping a cooler (e.g. Yeti) a little bit colder (i.e. 10c). It barely uses any water because it isn't doing much cooling. The solar cooler's competition is an ice block in a well-insulated cooler or a Peltier cooler powered by a solar panel.
I'm guessing it would not provide any noticeable cooling to a house; the paper's authors don't even claim that it may useful for cooling a home. I would suggest to just have a well-insulated, light colored, roof; and then toss on some solar panels for good measure.
Yr finding alot of new tech that i cant wait to see released to the public. Great Job sniffing it all out!
I particularly like the desalination platforms you mentioned in a newer post. Great thinking world over!
thanks, your work is most informative..
Great video, Dave, and a brilliant idea
Great video and thanks for the information.
Aerogel is an amazing insulator, it’s the best performing insulation on earth by a long shot, apart from maybe only vacuums. Ramping up the demand for aerogel to drop its price would have many other great benefits in the building industry
Passive solar homes would be nice to see covered here
You can always use solar heat to make distilled water
Thank you David
Wow, this is epic. This could really be a game changer
Sounds good, combine with better insulation and reflective siding/roofing to maximize the cooling.
@@Anonymoose66G Never heard of window algae.
Barium Sulfate paint formulations @Stanford which offer radiative infrared cooling …requiring sufficient surface area.
These calm, collected and informative vids are fantastic!
pretty sure the Aeorgel will foul due to particulate ingress after all your open to the air to let the water vapour out... so then you have a system with higher maintenance with possible ongoing costs
You restore my hope sir! Thank you.
Glad to hear it!
Slightly OT, but... perhaps a video on smart construction. There are far too many homes built without basements. Sometimes because of the soil conditions, sometimes due to flood risk. But, for those places where you can, you should. My home has a basement and on those really hot days, it's a wonderfully cool place of refuge. Not to mention the extra living space you gain. The cost / benefit is firmly into the benefit range in most areas.
Very interesting idea. As soon as I heard aerogel I thought this can't be cheap... thank you for sharing
This could be viable, It would be great if they could set up a large geothermal sinks for whole blocks of buildings to use for the heat pump/ AC units, as well as set up living roofs to reduce heat absorbing from buildings.
How about pumping the hot air through pipes, in a large tank of sand (A recent storage idea), or just dig a hole and fill it with sand. Pump air through at night to extract heat if required.
Well it’s easier to use liquids for heat transfer since it uses less energy per joule of energy. But you could probably store lots and lots of energy in sand if there’s a good way to yank it back out again maybe to heat a turbine or something.
Saw an interesting vid yesterday about Supercomputers. The relevance is it mentioned a Finnish design called Lumi which intended to be powered by Hydropower. Then rather than an overly complex cooling system for the rig, the idea is to export the heat from it into the local heating grid! 'District heating' and 'District cooling' systems are great ideas all round really!
Thanks for sharing your thoughts and experiences! 👍✌️🇬🇧
My pleasure!
This is cool! In terms of application, I think one promising area is for datacenters and server farms. These produce a LOT of heat and have to offset them with pretty aggressive cooling for the proper functioning of the equipment. In fact, between 30-55% of the cost of running a datacenter is typically spent on cooling the equipment! Suggests a major business incentive to invest in a high upfront cost (aerogel) for ongoing electricity-less cooling. And there's physical space to install and transport necessary water.
Servers don't need to be kept as cool as you'd need to for food preservation and air conditioning for human comfort. While a lot of servers keep their room temps around 55-72 F, the servers themselves don't NEED to be that cool. They could also directly use liquid cooling for the equipment, rather than using chilled water to power the air conditioning to cool the room to cool the servers. Might even exceed 10C cooling, depending on the site and application. Plus, servers usually have ample real estate to house a large system of this nature and the necessary water tanks.
The MIT paper ended up using 10mm/1cm thick aerogel. One paper last year estimated 1 square meter of 3cm thick aerogel would cost $7.20. It gets exponentially more expensive as it gets thicker (harder to dry), which means it should be even cheaper to do 10mm (increasing the thickness didn't necessarily improve things that much). Obviously, you'd still need to combine it with active cooling, but this seems like one promising avenue they could explore.
Curious to see how this all turns out anyway!
I enjoy watching so many of you JHAT videos! xD
Thank you
Excellent report, thank you!
I would love to see more hydro and cooling projects employed all over the world.
Awesome as always dave, think im gonna take a look see at that book also, cheers 👍
Cheers Rob :-)
Question: How efficient is this cooling system in high humidity?
very poor.
Thank you.
“Allo, and welcome to Just have a Think.” …. Easily the best thing about Mondays!
Yes, little inconvenience of reality… those of us on the other side of the planet, have to wait until Mondays for your weekly instalment… Thanks, Dave, for another thought provoking video
Two things:
1) What size do the pores need to be to be efficient enough to make the internal temperature bearable and not the most efficient?
2) Could their be a way to use the cooling effect to run a sterling engine and generate power?
It's all in the MIT document that you read ( I would Think, because unlike you I haven't even bothered to read it).
well done, as always.
But evaporative cooling only works in dry environments (places where there isn't much water). It doesn't work in high humidity as the air is already mostly or fully saturated.
You can use heat differentials to generate sound and you can use sound to generate heat differentials. Some of the most efficient coolers are such thermoacoustic systems.
I've always wondered if it's possible to build a fully mechanical solar AC with this. It probably is much less expensive than PV+AC, because solar thermal is so much more efficient.
Very promising, thanks. Just have a think, given that you are aware of the urban heat island, have a look at where the record breaking heat was recorded in the UK. No only urban but in close proximity to airports. Thinking, all the time
Small caveat about the latent heat @ 3:50. If you're thinking of a food calorie, it's 600 cal/kg, or 0.6 cal/g
When people talk about calories they usually mean kilocalories. Grab a nearby food item and you will see the k before cal. 600 calories per g is correct. Regular calories are so seldom used that calorie has become shorthand for kcal, but when not talking about food directly it makes sense to use it correctly. 600 kilocalories per kg would sound weird, hence 600 cal/g.
@@agsystems8220 Yeah. Unfortunately, its not written, just spoken. Because 1000 calorie = 1 Calorie. I've no idea how the English language invented this nonsense, but well...
The latent heat of vaporization of water is 540 cal/g. I don't know where they get 600 from. It's either a very lazy rounding error or is due to the temperature at which the evaporation occurs. (540 cal/g is at the bp of water.) At any rate, Dave is NOT talking about Nutritional Calories aka 1000 "real" calories. Capital C = nutritional, small c = physics.
Name a MIT Innovation that has floundered beyond academia. Unqualified quips reflect only a unrefined persona.
This makes me wonder if a less efficient substitute, such as felted wool, could be a reasonable substitute for the Aerogel.
The news article said it cannot, because other materials allow ambient heat to enter from the top layer and heat up the water that is evaporating underneath, thus negating the cooling effect. The aerogel is excellent at blocking sunlight and insulate from the heat of ambient air such that the evaporating water underneath it remains very cold.
I don't think he did a particularly good job of explaining how it works. I think the idea is that the pores in the aerogel scatter light below a certain wavelength but allow light in the 'atmospheric window' through. The aerogel forms a radiative 'anti greenhouse', letting heat radiate away while keeping most sunlight out. The evaporation side of it is just a secondary effect. The point is that the construction is extremely simple instead of lots of pipes, and even the fact that it 'leaks' as water evaporates away is not a problem, as that actually augments the cooling. Being able to fall back on evaporative cooling when it is cloudy (which largely closes the atmospheric window) is an extremely useful second mode, rather than a problem.
The gel layer is the layer that radiates and holds the heat exchange fluid, but it is the specially designed aerogel that is actually doing the interesting work of creating the anti-greenhouse.
Where it gets very weird is what it does in high humidity environments. If the wet layer is designed to be colder than the surroundings, and water vapour can permeate the top layer, then the gel layer will actually pull in water! During the heat of the day it will evaporate water, increasing cooling, while at night it may draw in water, potentially even recovering some that it lost.
The answer is conservation through better house design.
It saddens me to see the current crop of residential housing developments. Most are designed for their asthetic appeal to consumers that are more intertested in granite countertops and three car garages than R-values, roof lines or site orientations. While residential solar is not necessarily the only option for clean energy production, most homes on the market do not include a solar option. Home builders should consider structural orientaion, roof lines, tree locations and other design features that would facilitate the installation of rooftop solar (PV or not) at the time of construction or with consideration of future additions. For many people, ground mounted solar is not an option.
What's frustrating is the fact that these structures will be around for generations. Our kids' kids will live in these houses, never acheiving an efficiency or comfort level they desire because of the initial inefficient design. Sure, a gigawatt solar array could be installed (not really) powering a 100-ton air conditioning system (another exageration), but... why?
The best method for saving energy is not needing it in the first place. Energy conservation through better design reduces the need to purchase and install large A/C equipment. This translates to less complexity and repair, lower initial purchase and ongoing costs and more consistent comfort (if designed properly).
While all construction methods and materials have issues, they can be worked out if the desire is there. Look at lighting where current LED bulbs use a tenth or their incandescent counterparts. A TENTH! This took only one generation to accomplish. Or how about batteries? They have becone lighter, smaller and can be charged 1000's of times. With renewables and EVs being the driving force, more advances in battery chemistry are just around the corner.
The lessons here? Money moves mountains. We need to reward developers pushing the envelope. Codes need to be updated or 'stretched' to allow for thinking 'on the other side' of the box. Housing construction is like a hot air balloon; there's a delay between firing up the burner and seeing a change of direction. Inefficient, energy guzzling houses will still be around long after we die. QUIT BUILDING THEM!
Conserve first! You don't have to live like a caveman to live efficiently. And, you don't have to break the bank either. While it may cost a little more up front, an efficient home will have better resale value. And if you plan on staying put, the cost savings will mean a lot when you're financially strapped.
Let's not forget about residential water collection and usage. (we'll save that discussion for another day)
Here in Australia we have been experiencing massive rain events for 3 years in our summers and winters due to 3 years of La Nina. Europe appears to have stolen our hot dry.
Not here in WA😕
Though some more rain would be nice, at least we haven't had terrible flooding. Going by the northern hemisphere I am dreading the summer we may be due this year
@@emceeboogieboots1608 My apologies for being EastCoastist . Yes hard to generalise about Australia but BOM stats show in general our summers and winters have been very wet
Another great video. Thanks for keeping us informed about important technologies that might same human civilization.
Glad you enjoyed it
I love a good glimpse into a proper future. Thanks
Glad you enjoyed it!
could use it really much.. there was 30-31 C inside our flat this summer
I live in a subtropical climate in Australia it has been freezing, not literally but it does not feel like a subtropical climate any longer
Thanks La Niña and all your cloud cover!
It should be possible to provide cooling with solar collectors producing hot water coupled with storage tanks and air-conditioning units using the absorption principle - I believe some models using this idea are already available now.
This is very exciting news. I work for an organic farm and historic site where we are just embarking on new MEPS systems for our sustainable future and alternative energy sources are on the top of the list.
I used an ancient kerosene fridge for a few years. They burn kerosene with a little cylindrical wick. The hot gasses flow up a tube/chimney which is surrounded by an ammonia filled outer cylinder. The heat causes the ammonia to expand, build up pressure, then spray as an aerosol in order to act as a heat absorber or refrigerant. A gas fridge does the same. Low grade heat from a water heating solar panel should be able to use very hot water to do the job of cooling by this sort of approach. Low grade heat, in general, is an immense and often overlooked resource.
Thank you for the new video! It isn't Sunday without Just Have A Think.
Infrared radiation is the ultimate cooling. Like you said it isn't moving heat from one part of the air to another, it actually beams it back into space. Problem solved. Too bad it isn't super efficient, but if it was I guess that would be another problem because we'd freeze every night. Deserts are a good example of a climate dominated by radiative heating and cooling.
This idea from MIT is rather elegant, since it doesn't require electricity. That could be a very big deal. Using it to cool more traditional AC units is clever in a way that seems almost perverse at first (Yo bro, I put an air conditioner in your air conditioner. Now it works great!), but it makes sense if there's no additional electricity needed. The need for water could be a problem in really hot and dry countries like Saudi Arabia, but wouldn't be as big a deal in humid places like India.
It's too bad aerogel is so expensive, because that stuff is a wonder material. If we could make it in mass quantities and use it as insulation we probably wouldn't need cooling solutions at all. Or at least not as much.
The only potentially practical infrared cooling products are aimed at increasing the efficiency of standard AC systems. Just one degree reduction in water temperature after the cooling unit will translate into a substantial power saving.
Cheers Kevin :-)
I believe reflective white paints (reflect heat back to the space) are closer to common folks than other technologies around.
yes to cool Earth and cool things below a canopy but not much for a well-insulated house. Sure if the house is poorly insulated but otherwise the white is only very useful as window blinds.
RE: aerogel. Many cities, such as Las Vegas, have very high levels of dissolved solids, which will fairly quickly plug the matrix, as they do our water faucets/sprayers.
Put a Planetary Air Conditioner on your roof. Simple and effective. Mine provides enough cooling to stop 250 tons of ice from melting per year. It cost less than $200, and it's been working for seven years.
Awesome … As I am from India ….concept is very appealing. 🤩
Thanks for your great ideas , long ago our houses were made of mud , and they were cool in summer and hot enough in winter because the mud is insulate for hot and cool weather , but now we can not use mud , we need to modify the building material so that it is an insulated and still strong , or we need to cover our building with some kind of covering that protect the building from heat in summer and cold in winter
Maybe interesting to summarise all the existing technologies for passive cooling that are in application in architecture around the warmer parts of the world. Still amazes me why such important features are often ignored by architects and housing contractors, such that concrete boxes (that act more as solar ovens) are being built - which necessitate even more AC retrofitting.
Ancient people used techniques that we know about but rarely use today.
I hope masses and masses are inspired by you!
I Think the previous bloke who inspired Masses was a hard act to follow.
I feel that this technology is complicated and costly. I focused on insulating, increasing overhangs reducing sunlight from entering the windows during the hottest time of the day and argon efficient windows.
Yes. The article only speculated on using this tech to keep a cooler a little cooler. This "solar cooler" does not make sense for a home.
Thanks!
Thanks for your support. Much appreciated 😀
No earthworms since spring no fly larvae in trash all summer
Very few birds or flying bugs past decade
NW GA
Splendid now that's nifty & Smart! Thank you for sharing this. Greetings from Kambaramba villages,Sepik River, Papua New Guinea.
That was the greatest informative speech which I don't get at all ,😁
One of the mildest summers here in the East coast of the US that i can recall ... I'm worried the climate is coolong down.
The water supply could be set up like a toilet tank with a household water supply that's regulated by a refill valve to reduce nearly all maintenance.
We built a Solar-Passive house 23 years back in Australia. This is just simple thinking using normal building methods, Windows to the equator shaded by grape vines in summer with thermal mass floor and wall to the pole (South in our case). No hearing is required in winter daylight. Sumner 35 degree C days (95F) the house is 26C (78F) inside. Almost perfect but just a bit warm. This Solar Cooling would finish the picture. P.S. I often wonder how much money I saved not heating or cooling the house for that time? The construction was at zero extra cost as the builder was just told to build that plan 😁
what is typical relative humidity in the summer where you live?
There are fridge freezers used in caravans that run on gas. Burn gas to provide heat to make something cold. The Einstein fridge. I always wondered if they could make an air conditioner that ran on solar heat.
You could buy them in the 80s,
Brand name Arkla.
They sucked
That got a sub, thanks for the video.