With the steady rise in temperature and living standards, people around the world prefer to use air conditioners. Air conditioners (ACs) have conquered both commercial and residential places across the world today.
An air conditioner works on the basic principle of reducing ambient air temperature. Along with some mechanical techniques, air conditioners have developed so far from the conventional ones. The major components of an air conditioner are: evaporator, condenser, expansion valve and compressor. A refrigerant gas is commonly used for cooling, whereas a thermostat is employed to monitor and regulate the temperature. Atmospheric air is passed over evaporator coils containing the refrigerant, which help in absorbing the heat from the air and cools it. The compressor pressurizes the refrigerant and also leads to phase transition along with the condenser. This cycle continues till the indoor is cooled.
While air conditioners offer us an ideal indoor climate, they have a major drawback. They are the most energy-intensive electrical appliance we use at home or office. Due to their enormous energy consumption, they are quite expensive to operate and are not eco-friendly, since they emit greenhouse gases. However, air conditioning is necessary in extreme hot climates and congested indoors. Fortunately, solar-powered air conditioning offers an innovative eco-friendly solution to this problem.
As the name implies, a solar powered AC utilizes power from solar energy to serve the same purpose, but without any environmental costs. Solar powered AC, which is easy enough to replace the conventional type, offers three main benefits: cooling, heating and heating of water. Due to its obvious benefits, many companies have come up with different technologies to offer commercial products.
A solar powered AC can work on four different principles. Based on the location and usage, we can opt for the appropriate technology:
- Solar thermal cooling – This system uses Heliostats, which are highly curved mirrors lined up to attract the sunlight. These mirrors will reflect the sunlight to a pipe containing water. Due to the heat, water turns to steam, which will turn the turbine to generate electricity, and in turn drive the air conditioner.
- Photovoltaic Conversion – In this method, photovoltaic cells help in converting sunlight to electricity, which will directly power up the air conditioner.
- Adsorption & Absorption System – This device works on the basis of vaporizing water at a low pressure (say 10 mbar). With such a cool water production, the incoming air can be cooled and expelled. This device is powered up by thermo-chemical process of sorption. During winter, this adsorption machine can act as a heat pump. This is an eco-friendly AC which can be used in both commercial and non-commercial purposes.
- Cooling with desiccants – In this type of solar powered AC, Desiccants such as Sodium Chloride, Lithium Chloride are used (hygroscopic materials that attract water). This process combines dehumidification and evaporative cooling. According to atmospheric conditions, different solutions containing solid and liquid desiccants are placed in the cooling system.
These types are commonly found in Germany. The image displayed to right is of senior engineer of National Energy Renewable Laboratory, checking the desiccant air conditioner.
In terms of power source, solar powered ACs can be categorized into two types: Hybrid and Pure Solar. The table below compares the two types:
|Hybrid Solar Powered A/C||Pure Solar Powered A/C|
|Uses both solar and electric energy||Uses only solar energy|
|Not designed not for off-grid use||Designed for off grid use|
|Requires AC power||Does not require AC power|
|No battery required||Battery is required|
|Mostly used in urban areas||Used in remote areas lacking electrical power supply|
A solar powered air conditioner has a solar panel to convert the sunlight to electricity. This power enables the equipment to run the compressor. The heat generated through the solar panels can also heat up the water, which reduces the cost of heating water.
Australia has an inspiringly simple technology to offer in the solar powered AC segment. Australia’s national science agency, CSIRO, has invented a new solar air conditioning system which offers 50% reduction in carbon emissions which is generated by heating, air conditioning the rooms and heating up water. In CSIRO’s plant, a solar panel is erected to heat up the water, which can be used for domestic purposes and a fraction of its heat is sent to the AC.
The AC has two compartments: The first compartment will either have a vent to draw in the outside air or a heat exchanger to heat the air. This is similar to a car radiator. The second compartment will also draw in the air and through an attached dessicant wheel; the moisture will be removed to produce dry air. This dry air when passed through a rapid cooler gets cooled. During winter, rapid cooler shall not be used, so that the dry air will heat up the rooms.
A few companies in India such as Arka Technologies, VSM Solar, Headway Solar, Suryashakti Systems, Flareum Technologies, Gadhia Solar Energy Systems are promoting their solar powered AC products. Recently, Gadhia Solar has established India’s largest solar-based air conditioning plant using 100 parabolic mirror dishes in a 160 bed hospital, Muni Seva Ashram, Gujarat. The plant’s success has helped the hospital save 1 ton of wood consumption every day.
Many organizations are coming forward in India with various solar projects to make the nation eco-friendly. One such initiative is of Indian Railways and IIT-M. They are planning to launch solar powered A/C train coaches in nearby future. Solar energy can be studied in detail and solar powered devices can be encouraged by the government through various initiatives for better renewable energy consumption. With the launch of solar powered A/C’s not only green house gases will be reduced but also will improve sustainable development.