First, let me apologize that this post is a bit long-winded. But, in an effort to head off extraneious and redundant input (good luck on that, huh?).....
Last summer a steam pipe under the streets of New York City burst. I was unaware of why there was live steam being piped around the city in the heat of summer. An internet search gave the answer. Several, actually. One was that the steam was used for facilities cooling.
It's always seemed counter-intuitive that the first step in removing heat is to add even more. For example, the flame in a gas refrigerator or the compressor in an air conditioner. But, I know the basic physics and it makes some sense. But, the secret is not the addition of heat, it's using the heat energy to create a thermal differential.
The modern home is essentially an insulated box. In the winter, the insulation keeps the heat that's generated by stoves, heaters, furnaces and mammals (people and pets) inside the living area. Pretty easy and logical. But, in the summer, the insulation is used to keep the heat out. Then, even more heat needs to be generated to power the air conditioner to cool it off.
Of course, the problem is that the sun beats indescriminately on the roof of the house and surrounding areas. There are some thermal gradients (shade under trees, ponds and pools, etc.) but, they are too generalized and too slight to be effectively utilized.
If a solar concentrator could be put...say...on the roof, it would serve two purposes. One is that it would shade part of the roof and the second is that it would concentrate the sunlight into a small area. We've all charred a piece of paper with a magnifying glass so this is readily understood. If a series of parabolic reflectors werre used, the area of the reflector would shade and the sun's light would concentrate onto a small target. If a series of fresnel lenses were used, again, it would effectively shade most of the roof while concentrating the light onto a small target.
That action does create a substantial thermal gradient. By passing a working fluid (coolant) throught the hot section, it would gain energy and then when brought to the cooler, shaded area, allowed to expand in a heat exchanger, you basically have a "gas refrigerator" without the gas flame. Then it needs only a low-power fan and ducting to distribute the cooled air into the home.
The amount of energy available is substantial. A rule-or-thumb is that strong, direct sunlight provides about 1kW per square meter. My house is about 1400 sq. feet and my garage is about another 600 sq. feet. Divide that by 27 (to stay in the English system) and cut that in half to give a conservative estimate (I'm somewhat more northern than the "hot belt" of the US) and, during the hot part of summer days, there's about 35 kW equivalency there.
My furnace is 20 kW and my wood stove....I can't even begin to convert. Bottom line is that even a small fraction of that 35 kW could be used to substantially cool my house (ie: covering only part of the roof with the apparatus and the inherent conversion inefficiency of it).
Complexity of the apparatus could be minimized by reducing or eliminating moving parts (sun tracking). It would only have to work during the hot part of the day. That would be late morning to mid afterneoon. The insulation in the home could hold the cool air in til the sun sets and things cool for the night. But, of course tracking could still be used, even in a simplified form (of which there are many possible options).
So, the true bottom line is...why isn't this commonly done?
Last summer a steam pipe under the streets of New York City burst. I was unaware of why there was live steam being piped around the city in the heat of summer. An internet search gave the answer. Several, actually. One was that the steam was used for facilities cooling.
It's always seemed counter-intuitive that the first step in removing heat is to add even more. For example, the flame in a gas refrigerator or the compressor in an air conditioner. But, I know the basic physics and it makes some sense. But, the secret is not the addition of heat, it's using the heat energy to create a thermal differential.
The modern home is essentially an insulated box. In the winter, the insulation keeps the heat that's generated by stoves, heaters, furnaces and mammals (people and pets) inside the living area. Pretty easy and logical. But, in the summer, the insulation is used to keep the heat out. Then, even more heat needs to be generated to power the air conditioner to cool it off.
Of course, the problem is that the sun beats indescriminately on the roof of the house and surrounding areas. There are some thermal gradients (shade under trees, ponds and pools, etc.) but, they are too generalized and too slight to be effectively utilized.
If a solar concentrator could be put...say...on the roof, it would serve two purposes. One is that it would shade part of the roof and the second is that it would concentrate the sunlight into a small area. We've all charred a piece of paper with a magnifying glass so this is readily understood. If a series of parabolic reflectors werre used, the area of the reflector would shade and the sun's light would concentrate onto a small target. If a series of fresnel lenses were used, again, it would effectively shade most of the roof while concentrating the light onto a small target.
That action does create a substantial thermal gradient. By passing a working fluid (coolant) throught the hot section, it would gain energy and then when brought to the cooler, shaded area, allowed to expand in a heat exchanger, you basically have a "gas refrigerator" without the gas flame. Then it needs only a low-power fan and ducting to distribute the cooled air into the home.
The amount of energy available is substantial. A rule-or-thumb is that strong, direct sunlight provides about 1kW per square meter. My house is about 1400 sq. feet and my garage is about another 600 sq. feet. Divide that by 27 (to stay in the English system) and cut that in half to give a conservative estimate (I'm somewhat more northern than the "hot belt" of the US) and, during the hot part of summer days, there's about 35 kW equivalency there.
My furnace is 20 kW and my wood stove....I can't even begin to convert. Bottom line is that even a small fraction of that 35 kW could be used to substantially cool my house (ie: covering only part of the roof with the apparatus and the inherent conversion inefficiency of it).
Complexity of the apparatus could be minimized by reducing or eliminating moving parts (sun tracking). It would only have to work during the hot part of the day. That would be late morning to mid afterneoon. The insulation in the home could hold the cool air in til the sun sets and things cool for the night. But, of course tracking could still be used, even in a simplified form (of which there are many possible options).
So, the true bottom line is...why isn't this commonly done?
