Solar Air Conditioning
Does solar air conditioning really meet the requirements for today’s “Green Energy” demand; and is it ready to be implemented? Solar air conditioning is any air conditioning system that uses solar power. This can be achieved through passive solar, solar thermal energy conversion and photovoltaic conversion (sunlight to electricity) methods. >Passive solar does not use thermal energy to create a cold environment or drive any direct cooling processes.
Is implemented by using Cool roofs, that are roofs that can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the building) and high thermal emittance (the ability to radiate absorbed, or non-reflected solar energy), and green roofs or living roofs, which are roofs of buildings that are partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems.
Specifying the word “green” refers to environmentalism and not the color green, as with green roof tiles or roof shingles), using the mechanisms of heat transfer: heat conduction, convective heat transfer, and thermal radiation. >Solar thermal energy conversion is implemented mostly in commercial and industrial applications and is encountered in two different types such are: a- Solar open-loop A/C; using air passing over solid desiccants (like silica gel or zeolite) to remove moisture from the air to allow an efficient evaporative cooling cycle.
The desiccant is then regenerated by using solar thermal energy to dehumidify, in a cost-effective, low-energy-consumption, continuously repeating this cycle. A photovoltaic system can power a low-energy air circulation fan, and a motor to slowly rotate a large disk filled with desiccant, as well as to run ventilation systems to minimize energy loss. For heating porpoises, air is passed through an “enthalpy wheel” (often using silica gel) to reduce the cost of heating ventilated air in the winter by transferring heat from the warm inside air being exhausted to the fresh (but cold) supply air.
For liquid type applications, a desiccant like calcium chloride can be mixed with water to create an attractive recirculating waterfall, that dehumidifies a room using solar thermal energy to regenerate the liquid, and a PV-powered low-rate water pump. b- Solar closed-loop absorption and adsorption cooling; the solar air conditioner and solar heater is powered by solar energy collected in the evacuated tube solar thermal panels . The thermal energy collected is then delivered to the solar powered chiller using a Corn Glycol (antifreeze) solution and a system of pipes, pumps, and controls.
In the winter, even at below freezing temperatures outside, our evacuated tube solar thermal collectors still produce an abundance of heat. The system can be designed so that this heat is then transferred into your building, either reducing or nearly eliminating the operation of your existing heating system. This means free solar air conditioning in the summer, and free heating in the cold season. The following are common technologies in use for solar thermal closed-loop air conditioning. – Absorption: NH3/H2O or Ammonia/Water
Absorption: Water/Lithium Bromide – Absorption: Water/Lithium Chloride – Adsorption: Water/Silica Gel or Water/Zeolite – Adsorption: Methanol/Activated Carbon > Photovoltaic conversion; These type (sun to electricity) consist of PV (Photo-Voltaic) cells providing electrical energy to run a vapor compression system, mainly for residential porpoises, is also implemented to aid power to some of the components (circulating pumps, fans, ionizers, compressors, etc. ) used in the commercial and industrial systems mentioned before.