Solar Heating and Cooling?
Solar Heating and Cooling?
Solar reports say industry is booming, with falling prices and heavy Chinese manufacturing
As it waits for Congress to decide whether to extend a key government incentive program, the solar industry revealed several reports on industry performance so far this year -– and the numbers are looking healthy. The Solar Energy Industries Assn.,…
How does solar cooling and solar heating work?
Solar heating is easy, simply focus sunlight onto a pipe with water in it and the water in the tube heats. A solar collector uses many pipes inside a panel to gather as much heat from the sun as possible when in sunlight. There is a temperature control so you only circulate water through the collector when the collector is warmer than the tank. If you have flow when the collector is cooler than the tank, the tank will lose heat through the collector, which defeats the purpose. Use a small pump to circulate the water into a large insulated tank and the whole tank heats. Then, use a separate pipe to circulate water from the insulated tank into your rooms where you have a simple radiator which transfers heat into the room. By controlling how much water goes through the radiator in your rooms, you control how warm the rooms get. The key is the huge tank which has to be very well insulated so it does not lose heat to the environment around the tank.
Solar cooling is different, and much harder. There is no way to use sunlight directly to provide cooling as there is for heating. However, it CAN be done. Use an electrical solar panel to generate electricity. Use batteries to store the power for when the sun goes down. Then use the battery to provide the power to run a coling unit. Compared to heating, cooling is inefficient and wastes a lot of the power available from the sun by turning the electrical energy into mechanical energy. The pumping process of a cooling unit is a horrible waste of energy to the environment. A compressor heats the gas that is compressed. You can see this for yourself by using a tire pump. Pump up a tire and the pump itself gets hot. The compressed gas is then cooled in a condenser section and liquefies. The liquid is then piped into an evaporator section where it cools the place where the evaporator is located as the liquefied gas “boils” and absorbs heat. Think refrigerator. There is a section outside which is the condenser and an evaporator section inside. In essence, the refrigerator is a heat pump. It uses the gas as the transfer medium. Air conditioning does the same for a house as your refrigerator does for the tiny box inside.
Now for the really cool, but prohibitively expensive way to do cooling, a Peltier junction. A thermocouple is two dissimilar metals pressed together. When heated, this junction generates a few millivolts. Put enough of these in series and parallel and you can generate electricity directly from heat. This is what powers the Voyager spacecraft which were launched in 1978 (did famous flybys of Jupiter, Saturn and Neptune and sent back LIVE pictures over a 5 year tour.) and are about 10 billion miles away and STILL sending back data. The thermopile surrounds a radioactive source that as it decays, generates heat. The thermopile then takes the heat and makes the power that is still running these spacecraft today. Solar panels used in spacecraft near Earth will not work very well past about Mars, so the nuclear heat source was the only way to power the Voyager craft. Anyway, if you place alternate junctions on either side of an insulator and then apply power to a thermopile, the junction on ONE side get hot and the junctions on the other side get COLD. Now, if you use a solar electrical panel, batteries and a Peltier junction, you CAN cool directly using an intermediate electrical circuit , but it is only good for small things, like the CPU in your computer. You can’t make one big enough to cool a house and the amount of power it would consume would be more than you can collect, AND the cost of the materials would break the bank. But it IS pretty cool that the junctions that convert heat into electricity will get cold when you apply power in the absence of a heat source.
Geo-Solar Hybrid Heating and Cooling Syst
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April 25th, 2010 at 7:33 am
Well, it’s "Big Daddy Sun" glaring at you that is making your house hot. Your cheapest and most cost-effective ways of reducing your AC needs are actually pretty low-tech.
Start by reflecting back as much sun as you can before it ever gets inside to heat up the house. Cover bedroom windows with aluminum foil, shiny side out. You can either cut corregated cardboard to fit the windows and cover the cardboard so that you can easily place and remove the "sunshades" or you can apply the foil directly to the windows and then cut fine lacy patterns in the foil with an exacto knife to let in a little light and throw fancy patterns around the room. Just this idea alone will reduce your room temperatures significantly.
Next look in your attic. Chances are in Nevada you have only about 6" of insulation. Go down to Lowes or Home Depot and buy yourself enough bags of loose insulation to give you at least 12" – 16" of insulation. Spread it out over the existing insulation taking care not to block the air vents in the soffits (the part of the roof that hangs outside of your walls). Ideally, the soffits should be made of perforated aluminum panels that provide "continuous" ventilation.
Now look up. That hot air needs to get out of your attic. Some houses have a continuous vent along the peak of the roof. If yours does not, go back to Home Depot and get yourself at least two "turbine" ventilators. These babies work with the slightest breeze and pull the hot air up and out of the attic. There are some electric, thermostatically controlled fans available for this purpose and they work well in applications where there just isn’t enough breeze during the hot parts of the day.
You can also help protect your home from the heat by planting some fast growing trees on the south and west sides of the house and by planting vines that will grow up the walls of the house. Lush green plants can cool your home by 15 degrees because they cool the house not only by providing shade, but by using up heat to evaporate soil moisture, thereby actually removing heat from the air around your house walls.
Indoor houseplants can also have the same effect.
Now, a little "heat management". Since you’re in the desert, I assume it cools down between midnight and 6 am. At that time, get windows open on opposite sides of the house to cool the place down. First thing in the morning though, shut those windows and draw the shades. Keep your cool air in.
Check around your doors that the weather stripping is in good shape and replace it if it is not. That precious cool air will escape if it can.
By the way, that added insulation in your attic will help to keep your heating costs down in winter as well.
Using these techniques we are able to avoid use of the AC most of the time except on the hottest and most humid summer days in SW Florida.
Good luck
April 25th, 2010 at 7:33 am
http://www.cogeneration.net/Solar_Heating_And_Cooling.htm
The cost if installation would be something of concern, but the benifits could be great.