Cool your home with zero electricity costs!

[@human_isomer]

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.

[@human_isomer]

@Daniel Meyers what is the specific IR wavelength of sunlight?

[@user-wy4mp9ts3u]

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.

[@Leap6]

Now it has become a habit to eagerly wait for the week's episodes. Love it

[@JustHaveaThink]

Delighted to hear it :-)

[@Dysiode]

Absolutely agree! It's so great to have a little bite sized piece of positive AND informative news

[@jakubjakub8494]

@@JustHaveaThink nice technology but I got it cheaper, it's called hybrid offgrid PV with AC unit on load phase 😀

[@kayakMike1000]

@@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.

[@mondotv4216]

@@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.

[@richardgreen7225]

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.

[@FutureSystem738]

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.)

[@janami-dharmam]

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.

[@elvirabarbour1444]

Just seen 3 houses across from me have their roofs restored - in charcoal grey. Idiots. Where is Council stopping these practices?

[@carlpodrecca5177]

@@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!

[@FutureSystem738]

@@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!

[@treefarm3288]

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.

[@tristanschreiber5279]

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!

[@JustHaveaThink]

Yes, absolutely

[@madsam0320]

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.

[@VanillaMacaron551]

@@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.

[@glidercoach]

@@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.

[@acquisitium]

did you already buy a copy of the carbon almanac? there is even a kids version of it.

[@AttilaTheHun333333]

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.

[@Kevin_Street]

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.

[@madshorn5826]

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.

[@madshorn5826]

@@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.

[@kevinmcdonough9097]

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.

[@steverichmond7142]

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.

[@steverichmond7142]

@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.

[@MikeAG333]

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.

[@steverichmond7142]

@@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.

[@MikeAG333]

@@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.

[@steverichmond7142]

@@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.

[@IDann1]

I only ring the bell on two KZbin channels and this is one. well deserved

[@JustHaveaThink]

Thank you Daniel. I appreciate that :-)

[@GordieGii]

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.

[@richdobbs6595]

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.

[@robertstrader3267]

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.

[@GordieGii]

@@robertstrader3267 Why do you try to avoid AC?

[@vylbird8014]

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.

[@GordieGii]

@@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.

[@agsystems8220]

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.

[@rocklover7437]

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

[@jimurrata6785]

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.

[@VerifyTheTruth]

@@jimurrata6785 The Ancient Persians Used Cooling Towers, Even Kept Ice.

[@robertstrader3267]

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.

[@oldtimefarmboy617]

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.

[@BeyondMillennium]

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.

[@randalarmfield9848]

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!

[@willm5814]

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.

[@royharkins7066]

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 !!!

[@kaboozle]

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.

[@Leon_Schuit]

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.

[@dirhuebor2429]

@@Leon_Schuit Household PV cells do not have to be connected to the grid.

[@madshorn5826]

@@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.

[@tjeers3098]

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…

[@nathanlevesque7812]

@@tjeers3098 if that's winter to a place then that place only experiences summer

[@RustyWalker]

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.

[@az55544]

This works well in dry regions, but I don't believe it translates to humid regions. Or even England, New England, Europe.

[@brad4013]

Evaporative cooling is popular in outback Australia though not in humid coastal areas where most of us live.

[@VanillaMacaron551]

@@brad4013 I don't think Rusty is talking about evaporative cooling. This is a different technology.

[@GoodBoyOskie]

@@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.

[@paulw7404]

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!

[@VanillaMacaron551]

IKR!

[@weylguy]

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.

[@youtubewatcher4603]

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.

[@davestagner]

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.

[@OAK-808]

As usual, an excellent way to spend time. Thank you very much. You're an absolute star! BTW, KZbin 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.

[@youmakeitreal]

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 😑

[@zeideerskine3462]

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.

[@pomodorino1766]

Thanks so much for another very informative video!

[@JustHaveaThink]

You're welcome!

[@joedennehy386]

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

[@coolfusion1420]

Another great video. Thanks for keeping us informed about important technologies that might same human civilization.

[@JustHaveaThink]

Glad you enjoyed it

[@vernonbrechin4207]

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.

[@anthonycarbone3826]

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.

[@gefginn3699]

Great post my friend. I really appreciate hearing about new developments in this area.

[@JustHaveaThink]

Cheers Gef :-)

[@faica]

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.

[@realvanman1]

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?

[@alessandropinto5204]

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.

[@joewilson2258]

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.

[@MarkGoldfain]

I have to agree here, aerogel is a problem.

[@genesmith4019]

@@joewilson2258 And that's why using oil for fuel is insane.

[@jeffp3999]

@@joewilson2258 polyethylene can be made from gas.

[@callyman]

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!

[@traian2041]

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.

[@NirvanaFan5000]

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.

[@rollinswitch]

Sounds good, combine with better insulation and reflective siding/roofing to maximize the cooling.

[@rollinswitch]

@@Anonymoose66G Never heard of window algae.

[@stumckhall]

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

[@Cyrribrae]

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!

[@PedroRafael]

Very interesting idea. As soon as I heard aerogel I thought this can't be cheap... thank you for sharing

[@MD.ImNoScientician]

Excellent report, thank you! I would love to see more hydro and cooling projects employed all over the world.

[@simongigney2138]

Wow, this is epic. This could really be a game changer

[@glike2]

Passive solar homes would be nice to see covered here

[@yaumatijordan9157]

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

[@silvergreylion]

1. Take a black oven tray, usually used for something like pizza or lasagna, and put it outside in the sun, on a level surface. 2. Take a liter of rainwater, and pour it into the tray. 3. Measure the temperature of the water as the sun causes it to slowly evaporate. The temperature will creep down to a few degrees Celsius, if you've done it correctly. This is because black objects absorb most of the sunlight and heat up, but water is extremely efficient at absorbing heat, and the heated water molecules will easily jump through the very thin layer of water, and evaporate at the surface, cooling the water much more than if there was a much thicker layer of water.

[@Tclack]

Thank you for bringing attention to fantastic novel ideas like this all the time. I'm really excited about the prospect of actually removing eat from the earth system. Like most radical ideas, it's so conceptually simple and brings a "why didn't I think of that" moment. This is the perfect embodiment of that

[@islandmonusvi]

Barium Sulfate paint formulations @Stanford which offer radiative infrared cooling …requiring sufficient surface area.

[@keacoq]

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?

[@faustinpippin9208]

and the price of areogel.... I think buying a pv and ac is cheaper+you have electricity

[@petewright4640]

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.

[@Kevin_Street]

Hard water would tend to accumulate solid deposits in the pores of the hydrogel.

[@incognitotorpedo42]

@@Kevin_Street That's basically what Pete said.

[@DavidM2002]

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.

[@stevesmith-sb2df]

Evaporation cooling is reduced in areas that have high dew point temperature.

[@alencaru]

I believe reflective white paints (reflect heat back to the space) are closer to common folks than other technologies around.

[@grindupBaker]

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.

[@rdragonsheridan]

Name a MIT Innovation that has floundered beyond academia. Unqualified quips reflect only a unrefined persona.

[@Kevin_Street]

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.

[@vylbird8014]

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.

[@JustHaveaThink]

Cheers Kevin :-)

[@EarthCreature.]

I love a good glimpse into a proper future. Thanks

[@JustHaveaThink]

Glad you enjoyed it!

[@electricAB]

“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

[@martingorbush2944]

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.

[@silvergreylion]

.. unless you're using rainwater.

[@lnwolf41]

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.

[@kitemanmusic]

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.

[@KarryKarryKarry]

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.

[@TheHorseshoePartyUK]

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!

[@napalmholocaust9093]

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.

[@bikingcat3283]

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.

[@gordybishop2375]

You can always use solar heat to make distilled water

[@virginiagerardi2056]

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.

[@Gabrong]

could use it really much.. there was 30-31 C inside our flat this summer

[@smegscreations]

Thank you so much, very easy to digest....

[@jarrodhockley]

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

[@colleenforrest7936]

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?

[@grindupBaker]

It's all in the MIT document that you read ( I would Think, because unlike you I haven't even bothered to read it).

[@brpawankumariyengar4227]

Awesome … As I am from India ….concept is very appealing. 🤩

[@jaredleemease]

Thank you David

[@luimackjohnson302]

Splendid now that's nifty & Smart! Thank you for sharing this. Greetings from Kambaramba villages,Sepik River, Papua New Guinea.

[@geraldfrost4710]

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.

[@kpogatchnik]

Great video! Keep them coming.

[@chaitanyabhatraju]

I enjoy watching so many of you JHAT videos! xD

[@howdy832]

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

[@agsystems8220]

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.

[@Sekir80]

@@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...

[@incognitotorpedo42]

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.

[@kenbellchambers4577]

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.

[@DrSmooth2000]

Sprays where?

[@kenbellchambers4577]

@@DrSmooth2000 It sprays into another coiled tube which lines the freezer compartment of the fridge and has lower pressure. As the high-pressure gas is expanding by being sprayed through a nozzle, it absorbs heat. The gas goes round and round the system exactly like a compressor-driven fridge except it uses the heat from burning kerosene to pressurise the gas instead.

[@ashoakwillow]

Interesting video thanks Dave, and amusing that you feel the need to be diplomatic towards viewers who cannot, or willnot, accept what science has revealed. Thanks also for the links to similar similar sites, and the 'transcript' with accurate time links.

[@kimlibera663]

I am testifying on this technology this week.

[@jonathangold2087]

Sounds like some promising new technology, you we’re describing here. I suspect there are many existing off the shelf technologies that could also be applied to this problem, and yield some innovative and cost effective solutions to the problem of cooling our interior living spaces, during the warmer months. Thanks for keeping us well informed as to some of the new technologies being applied to help reduce the enormous costs of indoor cooling.

[@richteffekt]

I guess I'll be looking into making some primitive diy knock off to cool the southern facing part of my flat next summer. Will give update then.

[@richteffekt]

Wondering how to replace the aerogel...

[@grindupBaker]

@@richteffekt Yes people can look at you funny in Home Despot you try to buy a barrel of aerogel.

[@stephenlabarre7890]

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)

[@lawrenceleske3470]

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.

[@philholman8520]

Thanks for sharing your thoughts and experiences! 👍✌️🇬🇧

[@JustHaveaThink]

My pleasure!

[@mhkatal4774]

That was the greatest informative speech which I don't get at all ,😁

[@livingladolcevita7318]

Thanks Dave, sounds a bit like the fridge my sister once had many years ago, this was a large block of chalk with a dish shape in the top which one filled with water until it could hold no more. The resultant evaporation would keep contents cool for some time.

[@fvrrljr]

i'm trying hard to picture this, is it a old refrigerator or like you said block of chalk with a dish shape "hole" carved on top where you filled it with water. i tried googling no results will keep trying. yeah it caught my attention

[@livingladolcevita7318]

@@fvrrljr If you can imagine a cube of chalk, 18 inches(46cm approx) cubed with middle hollowed out and a basic door fitted to cover hole and a dish shaped hollow sculpted out on the top. Fill the top with water until it is saturated. The evaporation keeps things cool. Not seen one since mind you

[@fvrrljr]

@@livingladolcevita7318 Nice, Thank You very appreciated 👍 by any chance would you know what it would be called or the scientific term ? someone out there might 👍

[@froggarana]

@@fvrrljr scientific term ? porous pot, seriously , here in UK before refrigerators people would put their milk bottles in a big clay unglazed flower pot standing in a dish of water, and throw a wet cloth over it. indoors a 'fridge ' was a five sided cube box made of porous material like plaster of paris, sixth side a door, an indentation in the top of the box is where you put the water in hot dry countries they use a pot in pot , known as zeer

[@fvrrljr]

@@froggarana Thank you good looking out. it's been 3 months ago that i googled many ways to find what was being described and found it

[@dirhuebor2429]

Integrating this tech into home roofing would be a game changer.

[@silvergreylion]

It can be done much more easily, and much cheaper: Take a black metal tray, put it completely level, and have either a system for keeping a very thin layer of water in it, or something to spray a very fine mist on it. Water evaporates much more easily, when the layer is very thin, so the cooling effect is greatly enhanced. Be sure to use rainwater, to avoid build-up of residue. Run water pipes under the tray, and you can have cooling wherever you want. This is a very little-known thin-layer effect, which is probably also the base principle of the device in the video.

[@mawizard6341]

So if you're in a desert, they invented a new swamp cooler.

[@Clip7heApex]

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.

[@kevintdickson]

You could buy them in the 80s, Brand name Arkla. They sucked

[@wallaceanature2788]

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.

[@VanillaMacaron551]

Ancient people used techniques that we know about but rarely use today.

[@H2ON_MEA]

Thank you.

[@atmoo3447]

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

[@VanillaMacaron551]

Thanks La Niña and all your cloud cover!

[@DrSmooth2000]

Better now?

[@rapauli]

Right, let's manufacture and deploy 5 billion of these in the next few years. Great idea. Get on it.

[@blue_beephang-glider5417]

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 😁

[@froggarana]

what is typical relative humidity in the summer where you live?

[@drhaese]

Many thanks for presenting another exciting development. Though, I am genuinely concerned about new ideas relying again on non-degradable polymers which will later end up in our oceans.

[@silvergreylion]

There's a much simpler way. Use a black metal tray, and either have a system to keep a very thin layer of water in it, or spraying it with a very fine mist. The very thin layer allows the water to evaporate much quicker, cooling the tray much more. The water used does need to be rainwater, to not leave a residue. Run (other) water pipes under the tray, and you can have cooling anywhere you want. This is a very little-known thin-layer effect, which is probably also the base principe for the device in the video.

[@TheVigilantStewards]

Man, I would love to see this come about. I have looked into earth tubes for cooling and passive cooling tower designs, we are building in East Africa and it would be lovely to have a electric free solution for cooling! Thank you for sharing, and please do followup on this - I would love to see an innovation here to bring this to market

[@acquisitium]

i believe there is a dutch youtube woman who has an episode how iraq used to cool its cities(3000 years ago)

[@TheVigilantStewards]

@@acquisitium I think I've seen that it was either aqueducts with earth cooled drafts or towers that drew the hot air up that they used right?

[@acquisitium]

@@TheVigilantStewards i dont know if it was this specific video kzbin.info/www/bejne/f6XVaXxjr8yYpsU but its from her channel.

[@TheVigilantStewards]

@@acquisitium Yup, that's the one I saw with the ancient air conditioner - Yazd... also saw a roman underground earth tube video with subterranean aqueduct drawing cool air

[@acquisitium]

@@TheVigilantStewards amazing how simple and clever the solution he?

[@OperationDarkside]

I recently had the idea to combine special solar panels with heatpumps for very cold areas of the world, where the solar cells are optimized for very cold temperatures and are actively cooled by the output of the heatpump. The latter could be a stirling cycle heatpump as it reaches even lower output temperatures and therefore increase solar panel efficiency. I imagine such solar cell material still needs to be discovered, but it would make living in those areas much more affordable.

[@grindupBaker]

Patent it quick !

[@OperationDarkside]

@@grindupBaker Naa. All the shit I do is open-source. Including this idea. I can't attach licenses to comments, but this would be really hard to patent. Copyright or something similar maybe.

[@claudegarneau666]

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.

[@youtubewatcher4603]

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.

[@danielmadar9938]

Thank you

[@acccardone7679]

Unglazed pottery that is shaped correctly will do the same job as this gel, without needing crazy technology. In fact, there are buildings from thousands of years ago that used this method.

[@Energy-Americas]

Interesting, but the condenser fan is not the main use of electricity in an Air Conditioner. And the trend is towards heat pumps, where the "condenser" also acts as an evaporator, which doesn't need or want cooling. The more complete solution is solar-driven absorption cooling. In that technology, we eliminate the compressor, which IS THE MAIN draw of electricity in an AC. Also, we eliminate HFCs, which cause global warming. So, let's get a full solution, not a half-baked one, albeit from the geniuses at MIT. Advanced Solar Lab at UC Merced has tested and proven the tech I talked about.

[@bryanlarsen7562]

Another straight forward solution is just solar powered air conditioning. Air conditioning isn't usually necessary when it's not sunny, and an air conditioner that runs directly on solar DC can avoid some conversion losses.

[@michaelpeterson4406]

You restore my hope sir! Thank you.

[@JustHaveaThink]

Glad to hear it!

[@pittuk6500]

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.

[@tedphillips2501]

Early refrigerators required one to light a fire which boiled the ammonia refrigerant. Solar energy could be focused to achieve the same result without needing water or combustion.

[@GoCoyote]

Like many ideas, there is a huge gap (or valley of death) in between the idea and the reality of cost, production, and acceptance.