“Cold Tube” cooling system uses half the energy of an air conditioner

&gt; The notoriously bad energy efficiency of air conditioners<p>Air conditioners are actually pretty fantastically efficient for what they do. The problem with air conditioners is that there&#x27;s <i>no</i> way to move a ton of heat without using a lot of energy. So, they do use a lot, but they make the most of it.<p>What&#x27;s truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air right back out into the environment.

The author doesn&#x27;t really explain it well because his explanation breaks some physics laws, so it doesn&#x27;t &quot;suck&quot; your body heat away.<p>Instead, it lowers the amount of heat radiating onto you from your environment by replacing hot walls with cold walls, which will lower the temperature of your skin.<p>It&#x27;s efficient specifically because it <i>doesn&#x27;t</i> cool by convection (like every other cooler). This allows the designers to insulate it so they only have to offset temperature gained by incoming heat radiation when keeping it cool. That also means it won&#x27;t cool the air, just the objects near it.

An idea I was told about relatively recently that kind of blew my mind:<p>- Space is cold (~3K)<p>- The atmosphere is really quite transparent in the wavelegth 8-13 μm<p>- If one can construct an optical filter (e.g. grating) which is highly reflective except for a bandpass at 8-13μm, it is possible to reflect most solar energy but still &quot;see&quot; the cold of deep space<p>- It&#x27;s possible to build a box with sufficiently low thermal conduction, and this &#x27;magic mirror&#x27; on top, to effectively refrigerate its contents by radiation to space. This uses no power, and works in direct sunlight [^1].<p>So weird, probably not very practical (what about cloudy days?), but very cool!<p>[^1] in fact, if you put it in the shade then it would warm up because it could no longer radiate to space.

This sounds pretty neat, but their description of cold things sucking thermal radiation doesn&#x27;t jive with my freshman-physics understanding of thermodynamics. AFAICT they&#x27;ve got cold water circulating in a moisture-repellent membrane, so they&#x27;re able to absorb heat by chilling the water in the pipes instead of fussing with the humidity in the air like most AC does. So it sounds like trading inefficiency of standard AC units for an inefficient thermal interface -- you need to stand next to it to feel cooled?

I saw a very promising AC technology at CES in january that people may find interesting: <a href="https:&#x2F;&#x2F;www.oxicool.com&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.oxicool.com&#x2F;</a><p>I don&#x27;t have the material science or chemistry background to know how effective it is, but I hope everything they claim holds water, it sounds pretty good.<p>There&#x27;s also a DIY water based AC with pipes and a cheap pump you can find widely on the internet, but I haven&#x27;t done it yet. Here&#x27;s an example <a href="https:&#x2F;&#x2F;www.instructables.com&#x2F;id&#x2F;Hollis-homemade-AC&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.instructables.com&#x2F;id&#x2F;Hollis-homemade-AC&#x2F;</a> ... In the comments one poster suggested a toilet tank as a reservoir, that sounds promising.

This is just a regular hydronic radiant system which is very efficient because it doesn’t need to heat the air. The thing is, hydronic systems have been around for 70 years or more but they typically are not used for cooling because of the humidity issues that arise which are damaging to the building. So this can only be implemented in buildings with materials resistant to water damage. Hydronic radiant systems are the best around it terms of heating efficiency but very expensive to install. This article seems like hype and bs.

Not sure why they are researching the mechanism, these systems are commonly installed in Germany and known as &quot;Kühldecke&quot; (cooling ceiling).<p><a href="https:&#x2F;&#x2F;de.wikipedia.org&#x2F;wiki&#x2F;K%C3%BChldecke" rel="nofollow">https:&#x2F;&#x2F;de.wikipedia.org&#x2F;wiki&#x2F;K%C3%BChldecke</a>

I&#x27;m not an expert, if one is available please comment.<p>Human perception of temperature is mostly based on 5 things: Ambient air temperature, Radiant Heat (infrared radiation), humidity, direct conduction of heat, and air movement.<p>It seems like this addresses Radiant Heat. Another way to address this is to add more insulation, install low-emissivity windows, plant shade trees in your yard.<p>Half of my house feels much warmer in the afternoon because it lacks shade. I used a thermometer to see the difference between the ambient air temperature in the two halves; the hot side was only 2 degrees F hotter. I don&#x27;t have an IR thermometer, but I imagine that the walls in the hot side are at least 10 degrees F hotter.

I wonder how costly it is to fill your walls entirely with water pipes.<p>Also, one currently ensures there is a stud or lack of electrical when putting nails in a wall. I guess you gotta hang things up differently.

This is pretty neat. It lets you (somewhat) decouple the temperature and humidity of the air from how cool it feels to be in the room, by only removing <i>radiative</i> heat coming from inside the room. You could choose to exchange air with the outside more rapidly without losing efficiency because you aren&#x27;t putting as much energy into conditioning the air itself. I wonder if there are any infrared-transparent wall paints.

Circulating fan uses tenth the energy of an air conditioner.<p>The Revenge of the Circulating Fan <a href="https:&#x2F;&#x2F;www.lowtechmagazine.com&#x2F;2014&#x2F;09&#x2F;circulating-fans-air-conditioning.html" rel="nofollow">https:&#x2F;&#x2F;www.lowtechmagazine.com&#x2F;2014&#x2F;09&#x2F;circulating-fans-air...</a>

This is just a geothermal unit with the evaporator built around the load and instead of air to air transfer through convection it is air to air transfer through radiation... nothing but smoke and mirrors. The problem with efficiency and A&#x2F;C is the excess heat generated by the compression element of the Refrigeration Cycle. The closest thing to 100% efficiency is achieved through absorption chillers that utilize an internal chemical reaction based off of external heat to produce compression through a metered system... neat idea though. Heating systems that utilize the same process are different though - you can achieve greater than 100% efficiency with the use of flash gas bypass designs that will say for example produce 1.5 tons of heat in a 1 ton system.

This sounds expensive to install. For it to work as well as regular AC, wouldn&#x27;t this have to be built into basically all the walls in your home?

This sounds promising. I wonder if such can be implemented in small dwellings.

Description seems like a thing from a science fiction.

This sounds like they reinvented a swamp cooler. Am I missing something?

Pretty cool<p>(sorry)

&gt; .. as a person stands next to or beneath the panel, the body heat radiates towards the chilled panels to create a cooling sensation ..<p>I&#x27;m not sure that is an accurate description of the physics. Maybe the air next to the panel is cooler, accounting for the cooling sensation.