Solar Air Conditioning

Be careful as the "spin" on many products is far less than actual performance and efficiency.

I have investigated solar powered absorption HVAC units and my objections are the excessively high purchase & installation costs along with the very large footprint of the required equipment.

In most of the locations that I am currently assigned to determine viability of solar HVAC and solar electrical power for replacement of the existing systems, we simply do not have enough room at the sites to accommodate all of the required equipment.

It may be possible to go vertical with the collectors and solve that part of the footprint issue however the pumps, electrical switchgear, inverters and associated hardware still present some very high hurdles to overcome.

So far I have not been successful in finding any Solar Companies that can meet our needs and stay within our limited installation space.

I am hoping the equipment efficiency will soon improve to the point that will reduce the physical size of the footprint requirements and that the cost will start going down as more and more Solar systems are installed.

I do not think I will hold my breath while I wait.

There was this recent thread:

http://cr4.globalspec.com/thread/101281/Solar-assisted-Air-Conditioning

"Any brilliant inputs?"

No.

hi lyn! its been quite awhile now.

I have been toying with the idea of a natural gas fired, two-stage compressor-absorption system. Here in the hot humid south most of the electric bill is for air conditioning, and in summer NG is very cheap.

Instead purchasing electricity to spin a compressor, the 1^st stage is a small NG engine to mechanically spin the compressor. However small engines are notoriously inefficient with most of the BTU's going out the exhaust.

The 2^nd stage would be a small absorption system heated by the engine exhaust. You could add a small generator to power the air handler fan or other ancillary equipment. Would be cost effective for off-grid houses.

http://library.automationdirect.com/gas-turbine-repurposed-with-plcs-issue-24-2012/

Cool generator idea but about 10x the capacity, cost and complexity. For my prototype I was going to source the complete AC system and alternator from a van or bus, and fit the matching pulley onto the NG engine.

For the 2^nd stage I was going to source the absorption system from a NG refrigerator.

Absorption mechanisms in fridges do not extract much heat. These small fridges also have high R insulation to reduce the heat inflow.

Car air conditioners consume 20-25 HP of mechanical energy to create about 5 tonnes of cooling (rated as ice made in 24 hours). A small home fridge = 0.1 to 0.2 tonnes

http://www.kylesconverter.com/power/horsepower-to-tons-of-ait-conditioning

Automotive units typically lose 10-15% of contained refrigerant per year - depends on hours of use and speed and dust in the air. They are not sealed.

Ideally a sealed unit with a magnetic coupling should be used, or an entirely electrical sealed unit (which would require a 25 HP generator + 25 HP compressor and battery system to boot (and it would fill the boot).

It has been easy to use the engine power and a corporate decision to avoid sealed units because the car makers use air conditioning support and maintenance as important cash cows for the dealers in the summer.

It is certainly possible to accumulate the heat in a heated fluid tank(melted salts??).

Ideally for absorption you would need to boost the temperature of the collected/stored heat by a parabolic mirror that concentrated the heat and tracked the sun. You would get 100% of the heat, versus only 20% by electrical conversion. However, absorption units are not very efficient. So insulate your house very very well.

If you need 5 tons of air conditioning = about 19,000 watts = 15 square meters of intercepted sunlight ~~ 1400 W/square meter +/- times the inefficiency of absorption units of 20% means you actually need 75 square meters = wars with neighbours. Hell. my neighbours would have the smaller 5 meter one

so a 4 of 5 meter steered parabolic dish would be enough, with stored salt heat stored

Excellent, full azimuth and rotary control, and with an adjustable interfocal mirror(with variable F/L) can readily deal with any neighbours...

The transition from coal, oil, and gas to wind, solar, and geothermal energy is well under way. For instance, by 2020 renewable energy should account for 20% of the European Union's final energy consumption. To meet this common target, each Member State of the union needs to increase its production and use of renewable energy in electricity, heating, cooling and transport. In GCC countries solar energy is one of the potential candidates still to be explored. Various techniques to use solar energy for cooling purpose is under study. Of the various solar air conditioning alternatives the absorption system appears to be one of the most promising methods]. Absorption refrigeration research has got enough attention during recent years, specially its potential applications in waste heat recovery, solar energy utilization etc. It is reported that absorption cooling seems to have a promising market potential and commercial units are already available in the market. It is also reported in some literatures that the double/triple -effect vapour absorption system is the preferred option to improve the COP and compare it with the conventional AC systems.

it's been quite hot nowadays in the tropics. Heat on the ceiling of houses during peak hours have the potential to be recovered, instead of heating the inner space why not convert it to cooling it.

It's the same with the concept of this automatic tinting car window. Cool!

There must be an easy way or another way doing it -affordable and cheap. That's an innovation.

Where is the gradient with which to exploit a Carnot engine?

Heat, Heat, everywhere, the very boards did shrink,

and not a gradient in sight, it's harder than you think\\with apologoes to Coleridge...

Similarly with bimetallics, etc.

and the humidity = so high, you would have a hard time making an evaporative cold plate.

If you focus the sunlight, the temperature of the exposed parts will be much considerably hotter than local ambient temperature, every time the sun comes out.