8

I ask this question all the time.

I am living in Southeast Asia & the temperature there is always 30-32 C in almost every day of the year. So, houses in Southeast Asia normally are pretty hot. However, people there tried many way to make their home cooler.

For example, if you come to Southeast Asian countries, you often see "Roof Turbine Vents" (http://www.askthebuilder.com/roof-turbine-vents/) installed on top of the roof. The wind will make the turbine spin, and when it is spinning it will withdraw the hot air out of the roof. It is not a complete solution but the house is less hot if it uses Roof Turbine Vents than if it does not.

In addition, they also install the solar panel on top of the roof to get the hot water, and generally the Solar Hot Water system is quite effective as it can give the hot water all the time without spending any cent for electricity bill.

Now, come back to the cooling system. Even my house got a Roof Turbine Vents installed on top, we still have to use electricity air conditioner to cool the rooms, which cost a lot of energy bill. Also, for electricity air conditioner, we can only afford to cool a few rooms like the bed room. If I walk out the bed room then it is very hot.

So my question is:

Can we build a very effective cooling system for house or apartment using solar or wind power?

For example, we can install a cooling system on top of the roof. The cooling system can use the solar power from the sun, and then somehow use that energy to cool entirely the roof.

Or, for example, when building a house, instead of making the brick walls like the traditional house, we can use the wall that made of a lot of tiny hot-to-cold material. When the hot sun light triggers the wall, the tiny hot-to-cold material on the wall will convert hot energy to cold energy or something like that to cool off entirely the house.

I believe that the technical issue is not too difficult but it is just too expensive to build.

  • 1
    I see some conflicts with a home ideally facing south (northern hemisphere) for optimal solar power, but that also means the home may retain more heat throughout the day. – Sun Dec 4 '14 at 21:06
7

A common thing to do is use the cooler temperature of the ground to reduce the temperature of your home.

  1. If building a new home, you can simply build it into a hillside or completely underground. For Example, this house is built into the hillside and one of the key features is that it is covered with grass (vegetation) which will significantly reduce the temperature of your roof, along with the lower temperature of the ground, your house will be cooler than you could make it with an air conditioner, and it's free.
  2. But more likely, you are not building a new house and need something to help cool an existing house. This can be done by using some of the same concepts, just in a different way. Try running a couple hundred feet of tubing about 5 feet underground, throughout your yard where one end is outside and the other end is inside. The heat rising inside your home will cause air to be brought in through the tube which will be cooled by the ground. Simple, free, cool air.

You can check out this site for some other ideas as well. Good info throughout this site.

  • i don't like the solution 1 cos need sun light for my house – Tom Dec 2 '14 at 15:43
  • Your new home answer made me think of this: Before refrigeration became widely available in Korea, some people would store 50 gallon clay containers three feet in the ground. It served the purpose of having a lower consistent temperature during summer, but also kept the food from freezing over during winter. – Sun Dec 4 '14 at 21:09
5

I'm assuming that you are in part of the world that has a monsoon.

During the dry season, the evaporation of water can make a significant temperature difference. Google "Swamp cooler" or "evaporative cooler"

During the rainy season, your humidity tends to be absolute. Evaporation doesn't help much.

Much depends on how cold it gets at night. If nights are cooler, then you can circulate water over a very shallow pond (1/8" thick) It will cool to ambient temperature quickly. The cooler water can be stored until the hot part of the day.

Such a supply of cooler water can be used to make a conventional air conditioner more efficient.


You can reduce the heating by painting both roof and walls with titanium dioxide paint. TiO2 is a common paint pigment. It is black in IR so is a good radiator, but white in visible so it's a bad absorber.

  • Emissivity is a two-way street. Being "black" in IR might means it is a good "radiator", true, but that would also make it a good "absorber" — so they cancel each other out. The reality is that high-tech "cool paints" that are factory-applied to metal sheeting only achieve solar reflectivity ratings around the 75% mark. Thats expensive roofing made under ideal circumstances. Specialist paint that's bought in a tin and slopped on with a brush would be lucky to reach 60%. Regular white paint with UV stabilisers can get to 50%. In most cases it only makes sense to use normal white paint. – Tim Nov 10 '18 at 3:23
  • @Tim Correct, but there is little far IR in solar radiation due to the greenhouse effect. – Sherwood Botsford Nov 10 '18 at 14:38
  • 1
    Err, no. ~53% of all solar energy that reaches the ground is IR, ~42% is visible, and ~5% is UV. – Tim Nov 10 '18 at 14:59
4

It's funny you should ask this now, since I was just at a resort hotel that does exactly this.

There's a trick though. The entirety of its architecture was dedicated to the task. There wasn't any fancy technology involved in cooling the place, it was just cooler. Part of the way that the building accomplishes this is by having hallways on the outside of the hotel that are open to the outside. These hallways were about 12-14 feet wide, with large, north-facing window openings. As these hallways were pretty open to the weather, the floor covering used was tile instead of carpet (which they used throughout the entire hotel), and there were drains in the exterior wall at floor level. This hotel had actually weathered a Category 3 hurricane about 18 months ago, and while they had to replace a lot of glass, the floor only needed a few tiles replaced.

The ceilings were also appropriately high, allowing hot air to accumulate much higher than person-level, if it were ever to stagnate. The day I arrived though, this was certainly not a problem, as a windstorm generating some 50km/h winds was making the 30C heat feel more like about 17C. After the storm had passed though, the ease with which air circulated still kept the place quite cool, as a constant breeze was moving through the whole structure the entire time.

2

Yes you can construct a Solar portable air cooler. I have constructed this as a final year sem project and I got a good grade for it. Things needed:

  • A thermally Insulated box (hard thermocol)
  • A fan ( 3.5 W, 6V )
  • Solar Panel ( 8V )
  • Lead Acid Battery ( 4.5 Ah)
  • Signal Conditioning Circuit
  • PVC pipe
  • Ice

Construction :

  • The fan and the PVC pipe are mounted on the upper surface of a thermally insulated box ( made of thermocol )
  • The voltage output from the solar panel is connected to a charge controller to regulate the voltage input to the battery
  • The lead acid battery is charged and gives supply to the fan
  • The fan blows in air through the ice compartment
  • While the new air enters the compartment, it displaces the air that is cooled in the cooling compartment.
  • The displaced air ( cold ) flows out and cools the surroundings
  • This causes temperature drop in the surroundings, and thus acts as an air cooler
  • This is a simple battery charge controller that can be used in situations where the input voltage varies widely. Typically a solar panel’s output is dependent upon the amount of sunlight that falls on it. This, of course, varies from morning to evening.

Working Of Circuit Diagram :

  • Here the dotted box marked X is a simple voltage regulator that gives an output voltage of about 7 Volts – the 5K preset has to be adjusted to achieve this. The input voltage from the solar panel is assumed to vary from about 8 Volts to about 11 Volts. The charging current is about 05A. The “discharged” battery voltage should be about 5.5 Volts. The dotted box marked Y is a simple circuit that prevents over charging. This is done by sensing the battery voltage – when this crosses about 6.5 volts (adjusted by t 10K preset) Q4 turns on thereby diverting the drive from Q1-Q2 Q5 and Q6 are diode connected transistors (two silicon diodes, such as 1N4848/1N4001 can also be used in their place) that provides a reference voltage of about1.3 Volts.
  • Connect the solar panel to the input (or a voltage source of about say 9 Volts)
  • Adjust the 5K preset so that the output voltage is about 7 Volts.
  • Move the 10K preset slider to ground

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