Sola r AC                                       Solar Air Conditioning                            Guilt-free Comfort for S...
E                     xtensive air conditioning is    any air conditioning (cooling) system    heated (Stage 6 to 7) in th...
Sola r AC                                                                                                           fuel-s...
a number of advantages. These             offer a reasonable alternative to the       the long run. It is just a matter of...
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Solar Air Conditioning - Cooling India Journal, June 2011


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Solar Air Conditioning - Cooling India Journal, June 2011

  1. 1. Sola r AC Solar Air Conditioning Guilt-free Comfort for Summers Early summers usually bring a pleasant relief from the bone chilling winters, but come April & May, the summer heat starts taking its toll, both physically as well as mentally. And when it’s a tropical climate, as in most parts of India, the hot days can be all together stressful. The energy levels of individuals go down and so does their productivity. This is, when the modern day Air conditioning comes as a God Gift. A very large number of offices, laboratories, hotels, public buildings are nowadays fitted with air conditioning systems. Centralized Air conditioning Systems ensure cooling in every nook and corner of the working space. While this all sound hunky dory, its not. - Subhash Chandra Mathur and Sumit Mathur 72 June 2011Solar Air Conditioning (SAC).indd 72 6/10/2011 2:29:32 PM
  2. 2. E xtensive air conditioning is any air conditioning (cooling) system heated (Stage 6 to 7) in the Sola r AC synonymous to heavy power that uses solar power. A liquid or a countercurrent to the air inflow in consumption (and wastage) gaseous substance either the heat reclamation rotor. The leading to not just heavy accumulates on the surface of a exhaust air is further heated (Stage electricity bills but also the dreaded solid, porous substance (adsorption) 7 to 8) through external heat sources frequent power outages. The next or is taken up by a liquid or a solid (i.e. solar thermal system). Finally in step is of course DG sets, to bring substance (absorption for providing Stage 8 to 9 Sorption Rotor is the desired comfort indoors, while the necessary cooling). In some Regenerated through the desorption puffing out clouds of black smoke processes, supply air is directly of the bound water. with terribly high levels of sound conditioned i.e. treated in terms of pollution for the outside world and temperature and humidity. Open and Closed cycle Air the environment to endure. This thermally driven cooling and Conditioning Systems In the midst of saving ourselves air-conditioning process is at the Open-cycle systems are more from the fury of the nature, we are heart of every solar cooling system. beneficial in buildings with high inadvertently attacking the nature The main principle of Sorption humidity loads and high air exchange more & more, which keeps returning Assisted Air Conditioning is shown in rates. The installation of ducts for even more furiously every now and the graphic here. The solar energy is the supply air and the return air, as then. One of the biggest points of used to dehumidify the sorbent. well as a heat recovery unit is concern thus is the impending In Stage 1 to 2, Sorptive required. In this, the outside air is danger due to the rising world dehumidification of outside air takes dehumidified through sorption and is temperatures (Global warming!!). place with simultaneous rise in then brought to the desired So, what shall we do to survive and temperature through the freed temperature by heat recovery as survive with comfort? adsorption heat. Then the air is well as direct and indirect evaporative Let’s not forget we have an cooled in the heat reclamation rotor cooling. Usually dehumidifying is immense source of energy in the in the countercurrent to the exhaust achieved in a rotor containing the very Sun that we’re shielding air (stage 2 to 3). Air is further desiccant material silica gel or ourselves from. One answer is the cooled (Stage 3 to 4) through lithium chloride, but increasingly Generation of power using sun’s evaporation-humidification; Thus liquid desiccants (desiccant material: energy. It’s free and for now we can the air inflow to the building has a lithium chloride) are being tried. In safely assume, unlimited. Yes, solar lower temperature and less water these systems the solar heat is energy can light up our homes and vapour than the outside air. In Stage required for the regeneration of the cook our food. But can it also cool 4 to 5 Heating of the air takes place, absorption/adsorption unit. our houses? The answer again is and if necessary addition of water Closed-cycle desiccant yes. Solar air conditioning, a vapour. Then during Stage to 6 evaporative cooling systems are revolutionary and upcoming building’s exhaust air temperature is based on the processes of Adsorption technology, provides the answer. lowered through evaporative cooling (based on solid desiccants like silica Solar air conditioning refers to in the humidifier. This exhaust air is gel or Zeolites with water as refrigerant) or Absorption (where desiccants are liquid ex material pairs of lithium bromide as desiccant and water as refrigerant, or water as desiccant & ammonia as refrigerant, where sub Zero temperatures may be required). For cooling and acclimatizing of buildings, only solar-thermally driven processes are used. In actual practice, solar collectors are used to convert solar radiation to heat that is then fed into a thermally driven cooling process or into a direct air- conditioning process. Particularly in special applications, for example for cooling medicines in remote areas that are not connected to the grid, a photovoltaic generator transforms solar radiation to solar power that June 2011 73Solar Air Conditioning (SAC).indd 73 6/10/2011 2:29:33 PM
  3. 3. Sola r AC fuel-saver for conventional air- conditioning. In such a case free cooling directly through the heat rejection unit might be an option in the cooler seasons. Heat rejection rate greatly affects the performance and efficiency of the chiller. In most systems the waste heat is released into the environment by dry coolers or wet Graphic: Comparison of open-cycle and closed-cycle cooling systems cooling towers. The former are suitable for moderate climate zones then drives a refrigeration process that only occasionally have high o usually in the form of a compression outside temperatures (>30 C). Wet chiller. There have been considerable cooling towers have the advantage developments in the field of solar- that cooling water temperatures assisted heating and cooling and below ambient temperature can be world over this technology is being obtained. However, it only works if rapidly tried and adopted. the relative high humidity allows for evaporative cooling. In regions with a shortage of water it is also Photo : Solar Powered AC house unsuitable. In addition, some countries have imposed strict parabolic dishes (Scheffler type) by hygiene regulations on wet cooling the Indian company Gadhia Solar towers which make the operation of Energy Systems (GSES), each small systems economically unviable. 12.5 m2 in size now supply the It is essential to be aware of the already existing 100-ton air- fact that boundary conditions other conditioning system of the 160-bed than the nominal conditions, can Photo: Climatisation of a building hospital at Muni Seva Ashram. negatively affect the performance of of the University of Sevilla the cooling machine. If the system is Performance of Solar Air not designed for the nominal Chiller: Double-stage BROAD Conditioning operation point, the relevant BZH 15 IX, China. Source of power: While designing a SAC system & operating data must be requested 352 m2 linear-concentrated Fresnel for judging its performance the key from the manufacturer. Then, for collectors (Mirrox, Germany). Heat points to observe are Load Profile, example, a dry reverse cycle chiller rejection: Cooling tower. Cooling: Outside temperatures & humidity. can also be used in warm climates if cold distribution through a central The decision whether solar the solar thermal system is adapted ventilation system. (Photo source: cooling is sensible at all is influenced accordingly. Mirrox GmbH). strongly by the load profile. Solar Utilization of efficient EC motors irradiation and cooling demand must in the SAC set up helps to reduce be correlated, since the use of fossil the energy consumption. To further fuels for the operation of the chiller reduce electricity consumption, is disadvantageous from a primary these should be controlled according energy point of view and should be to operating conditions and cooling avoided. demand. Depending on respective Photo : Solar Powered Air In order to achieve the highest local conditions, waste heat can also conditioned house possible degree of utilization, be rejected of in other ways e.g. applications that also require heat through boreholes, swimming pools Recently, Solar thermal World for heating water or for the heating or ground water. Ideally the heat Magazine reported that India’s latest system outside the cooling season can be used in other places. and probably largest solar thermal must be explored. Thus, residential based air-conditioning system went buildings & small office buildings are Advantages of Solar Air operational at Muni Seva Ashram most suitable. If cooling is required Conditioning (MSA) in Goraj, situated in the throughout the year (process cold, In comparison to conventional, Vadodara district of Gujarat state in server rooms) the solar cooling electrically driven compression western India. A total of 100 system can be used merely as a cooling technology, solar cooling has 74 June 2011Solar Air Conditioning (SAC).indd 74 6/10/2011 2:29:34 PM
  4. 4. a number of advantages. These offer a reasonable alternative to the the long run. It is just a matter of Sola r AC systems are most useful when the conventional ACs. In addition to time when this technology would be sun shines the strongest in summers. drastically reducing or even mass produced, bringing down The machines generally utilize eliminating current air conditioning costs to affordable levels for the environment friendly refrigerants, bill, in many regions, one can common man. And then, the days leading to lower green house gas receive a huge cash rebate as well that pose the maximum cooling emissions. In most cases, water is as a tax credit by powering his air requirements shall be the very utilized which compared to conditioner with solar air same days when maximum energy refrigerants used in compression conditioning systems. As of now, could be extracted from sun while cooling machines has no greenhouse the capital investments are high but pocketing all the resulting benefits. potential. Significant power savings the system can justify its worth in The choice would really be ours! can result from the fact that these systems merely require auxiliary ❁ energy for the operation of pumps, Subhash Chandra Mathur, with four decades of experience in thermal heat rejection etc, if the systems are and renewable power generation and distribution, is an expert in designed correctly. In addition to Government liaising, Strategic Planning and Project Execution. Under cooling, the solar collector system the aegis of Bureau of Energy Efficiency and United Nations Industrial can also provide thermal energy for Development Organization, his organization, Samarpit International domestic hot water preparation and Group (SIG) works extensively in Energy Conservation, Carbon heating support which leads to a Management, Climate Change and Sustainable Development. SIG also further reduction of emissions. SACs helps a wide spectrum of industries in developing cutting edge strategic are also ideal for hotels, business solutions, to succeed in a highly competitive environment. supermarkets, schools, factories, ❁ Sumit Mathur is an energy sector enthusiast. He has been actively and large office premises etc. involved with both conventional and renewable power systems and is Furthermore, noise emissions are a prolific writer. significantly lower since the machines work without compressors. Solar based AC systems thus can June 2011 75Solar Air Conditioning (SAC).indd 75 6/10/2011 2:29:35 PM