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solar absorption chillersAir conditioning makes up bulk of the power usage, especially in tropical countries where the sun is shining almost throughout the year and the humidity levels are high. It makes a perfect sense to use solar heat to cool homes, business and factories. Many air-conditioning systems are commercially available using simple roof top PV solar panels to generate electric power to run an electric window air-conditioners. This system uses commercially available solar panels and window air-conditioners and uses solar power to generate electricity to run the compressor and the blower in the air-con unit. This system requires large storage battery to store adequate electricity to run your air-conditioners for specified period. Otherwise it requires a large area of solar panels to meet the demand. The efficiency of such systems can be improved using DC operated compressors and fans. However, renewable energy such as solar is still expensive to run air-conditioners because of high initial investment cost, though it may be economical in the long run as the cost of solar panels and accessories slowly come down over a time. Moreover such systems are limited to small air condition capacities.

solar chillers-typical apacitiessolar absorption chillerFor large air-conditioning requirements such as business and factories, we need a system that uses solar heat directly to air-condition the premises with higher efficiency and thermal storage capabilities. Designing such a system is not very difficult because most of the components necessary to install such systems are readily available. One can install an air-conditioning system based on 100% solar thermal heat with molten salt thermal storage. Alternatively, a hybrid system can be installed based on solar heat without a thermal storage but using   city gas supply. Many countries use gas for heating during winter seasons but do not use gas during summer. These countries can use a hybrid (solar-gas) system to air-condition their premises and avoid peak electric usage during summer seasons thereby avoiding electrical black-outs. The advantage with such system is they can also be used for heating the premises during winter season. With changing climate due to global warming many warm countries like India also experiences cold temperatures during winter season. For example New Delhi in India has experienced a sharp drop in temperature up to 15-20c during winter from earlier winters.

Solar cooling systems to date have used waste heat gas absorption chiller heaters, which utilize the waste heat from cogeneration systems (CGS) for the cold water. However, these chiller heaters with their established technologies are devices designed for the effective use stable CGS high-temperature waste heat, so they cannot accommodate the preferential use of solar heat when solar hot water temperatures suddenly change from large variations in the heat collector temperatures due to changes in the weather. The new solar absorption chiller heaters are now specially designed for the effective use of low-temperature solar heat to address this problem and improve the energy conservation effect from solar cooling system. Hot water at less than 90C can be used for such systems and typical chillers with their rated specification are shown in the figures.solar trough

The efficiency of the system can be vastly improved by using parabolic solar concentrators, up to 27 times higher than ordinary flat plate solar collectors resulting in conversion efficiency up to 85% in heating and cooling. By selecting a natural refrigerant such as R717 we can save the environment from ozone depletion. Such systems offer flexibility to use exhaust heat, natural gas along with solar thermal storage up to 220C (phase transition temperature).The system offers an attractive return on investment, electricity savings and Carbon pollution reduction. The system can be designed from 5TR up to 200TR refrigeration capacity for 100% solar and up to 1000TR for a solar-gas hybrid systems. The solar thermal system with molten salt storage is versatile in its application because the same system can be designed for heating or cooling or on-site power generation for continuous applications.

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Renewable Hydrogen is the key that can offer us energy independence in the twenty-first century. Fossil fuel usage will still continue for some more time because the world has already invested massively on fossil fuel infrastructures. The stacks are too high for them to switch over to renewable over night. It is the Mother Nature who provided us coal, oil and gas all these years using her manufacturing process under the earth over millions of years. But we human beings exceeded her tolerance limit by emitting greenhouse emission by our rapid growth in population and industrialisation.We failed to discover an alternate fuel in time and continued with an age-old technology with all its inefficiencies. Inefficiencies breed pollution. We were keen to use the heat of combustion by burning a fossil fuel to generate electricity or drive our cars, but paid no attention to the gases released during such combustion. We learnt Thermodynamics and the relationship between heat and work, but failed to understand the consequences of gases of combustion and its impact on our environment.

There are two issues involved in burning a fossil fuel to generate electricity. The heat of combustion is an exothermic reaction and we get a certain amount of heat. Then we convert this heat energy into electrical energy and the overall efficiency of such conversion is about thirty-five percent. Only thirty-five percent of the heat input energy becomes electrical energy and the remaining sixty-five percent heat along with gases of combustion are released into atmosphere. Of course part of this heat is recovered in a commercial plant, but the bulk of heat is released into the atmosphere as greenhouse gases. We failed to understand the potential of Hydrogen even though we used Hydrocarbon for several decades. We even discovered Urea, the fertilizer that caused ‘green revolution’ in agriculture, using the same Hydrogen present in the Hydrocarbon feedstock. It is time for us to make best use of a fossil fuel to its most potential when we burn each kilogram of fuel. We should burn coal not just with air but also with steam so that we can generate Hydrogen rich gas that can run a gas turbine in a combined cycle or run our cars on roads. Such a conversion will lead to a substantial increase in energy efficiency as well as in greenhouse gas emission reduction. Governments in industrialized countries should make it a mandatory to convert all their power plants to syngas generation as described above. They should also discourage new plants using fossil fuels with punitive power tariffs and encourage renewable energy projects with higher tariffs. Governments can also impose similar tariffs for transportation depending upon the fuel used such as fossil fuel or Hydrogen.

Governments should encourage renewable energy projects such as solar and wind   to generate Hydrogen from water as centralized power plants and distribute DC (direct current) by rural electrification. If the country side is electrified using this system then, agriculture, business and industries can thrive in rural areas. Direct current (DC) distribution net work can be installed in rural areas and encourage people to use energy-efficient appliances such as Direct current air-conditioners with energy star ratings and tariffs. Governments can bring about these changes by adopting a ‘carrot and stick ‘policy to encourage renewable and discourage fossil fuels.

Solar energy is the key from which all other forms of energy emanate such as wind, geothermal and ocean thermal energy conversion system.  It is of paramount importance to increase the efficiency of renewable systems and improve energy efficiencies of appliances we use. It is simpler to use LED bulbs using a Direct current generated by Renewable Hydrogen. It is once again the Mother Nature that can come to the rescue of human beings through solar, wind and water to generate clean energy for the twenty-first century.

Energy generation and distribution is no longer a business or revenue issue but a moral and ethical issue for Governments. It is only people who can bring about such sweeping changes by electing the right Government who can care for the environment. The future generation will judge us only based on what kind of environment we leave them behind.

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