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    utilization of solar energy utilization of solar energy Document Transcript

    • Utilization of Solar Energy by Non-conventional Methods L R Raviteja Krovvidi, (raviteza88@gmail.com) 6th semester, B.Tech, EEE. (09843557280) Jitesh Mathur, (jiteshmathur2006@vit.ac.in) 6th semester, B.Tech, EEE. (09944353256) VIT UNIVERSITY, VELLORE. --------------------------------------------------------------------------------------------------------------------- ABSTRACT: In this project study, various Solar technologies have been discussed which are feasible both technically and economically. Strictly speaking, the economics has to be improved a long way before mass commercialization of solar products can occur. Nevertheless, the time is ripe for alternate sources of energy before we destroy this planet or exhaust the fossil fuels. Preserving the ecology and environment is a moral imperative rather than an economic equation. Solar energy is one of key alternatives available for free of cost, which should be utilized effectively to reduce the human footprint on environment. CONTENTS: 1 INTRODUCTION 2 SOLAR AIR CONDITIONING & REFRIGERATION 2.1 DIRECT & THERMO-MECHANICAL 2.2 ABSORPTION & ADSORPTION AIR CONDITIONING / REFRIGERATION 2.3 HYBRID PHOTOVOLTAIC/THERMAL (PV/T) SYSTEMS 3 CONCLUSION REFERENCES
    • 1. INTRODUCTION tank storage. This eliminates the motor pump all together. Similarly all the wastes The implementation of solar materials of the house hold can be fermented technologies in daily life has become an to produce bio-gas which can supplement extreme need of the hour. Though cooking gas if not completely eliminate it. intermittent, solar energy cannot be discarded completely and it particularly suits 2 SOLAR AIR CONDITIONING & Indian climate where long and clear daylight REFRIGERATION is abundant. It can be implemented in almost all parts of India particularly in plateaus It is interesting to note that the same which have hot tropical climate throughout solar energy, which is stored as heat, can the year. also be used for air conditioning purposes. Solar air conditioning and refrigeration has a huge potential but relatively, a less exploited Any house in India generally has the area. In fact, utilizing solar energy for air following load requirements. conditioning drastically reduces the load on 1. Lighting the grid, especially in summer. It can be 2. Air conditioning (Heating & Cooling implemented at any scale, the bigger the depending on climate) better. The cost of installation is paid back 3. Refrigeration in a couple of years and moreover there are 4. Motor pump no electricity charges. Also maintenance is 5. TV etc. less compared to present vapour compression systems. There are many ways It is important to note that lighting, of implementing air conditioning through air conditioning and refrigeration account to solar energy. The following section more than 80% of the total load. discusses them in detail. Interestingly all these loads can be sufficed through solar power. In fact, by proper 2.1 DIRECT & THERMO- design of the house itself, these load MECHANICAL TYPE requirements can be minimized. Such designs are called passive solar designs. In In direct method, a solar photo- general, people discuss about solar energy in voltaic cell is coupled with dc motor which terms of the amount of heat or electricity runs the compressor of the AC. This generated from it. But the same solar energy generates cooling effect. But the inherent can also be used for cooling purposes by disadvantages like cost, vaable speed various advanced techniques like sorption compressors etc are unfavorable for this refrigeration. This greatly reduces the type. electricity demand on the grid and its In thermo-mechanical systems consequences. Also the availability of solar evacuated tube or parabolic collectors are power coincides with the load requirements coupled with Rankine or Sterling engine to in particular seasons. generate electricity, which can drive the It is always best to implement solar vapor compressor. Alternatively, a Sterling technologies in conjugation with other refrigerator (heat engine operated in reverse) renewable sources like wind, biomass etc for can also be designed which directly better operations. For example, a wind based produces cooling effect. This is also water pump can be implemented for water expensive and rather complicated.
    • 2.2 ABSORPTION & ADSORPTION AIR CONDITIONING / REFRIGERATION Sorption air conditioning is the most promising of all the air conditioning techniques available at present. Not only it is simple in design, it is also economical. These systems work on the principle of adsorption. Sorption refrigeration uses physical or chemical attraction between a pair of substances to produce refrigeration effect. A sorption system has a unique capability of transforming thermal energy directly into cooling power. Among the pair of substances, the substance with lower boiling temperature is called sorbate and the other is called sorbent. The sorbate plays the role of refrigerant. Absorption refers to a sorption process where a liquid or solid sorbent absorbs refrigerant molecules into its inside and changes physically and/or chemically in the process. Adsorption, on the other hand, involves a solid sorbent that attracts refrigerant molecules onto its surface by physical or chemical force and does not change its form in the process. refrigerant vapour from the evaporator rejecting the sorption heat Qa to ambient. In WORKING: The component where sorption the evaporator, the liquefied refrigerant from takes place is denoted as absorber and the the condenser evaporates removing the heat one where desorption takes place is denoted Qe from the cooling load. as generator. The generator receives heat Qg The working heat is supplied from from the solar collector to regenerate the the collectors. The water or working fluid sorbent that has absorbed the refrigerant in gains the solar energy and supplies it to the the absorber. The refrigerant vapour adsorber. So the cooling capacity actually generated in this process condenses in the depends on the amount of energy collected. condenser rejecting the condensation heat Absorption refrigeration has been Qc to ambient. The regenerated sorbent most frequently adopted for solar from the generator is sent back to the refrigeration. It requires very low or no absorber, where the sorbent absorbs the electric input and, for the same capacity, the physical dimensions of an absorption machine are smaller than those for adsorption machines due to the high heat
    • transfer coefficient of the absorbent. areas where the grid extension is difficult Besides, the fluidity of the absorbent gives and not economical. Such system greater flexibility in realizing a more incorporates a combination of one or several compact and/or efficient machine. renewable energy sources such as solar photovoltaic, wind energy, micro-hydro and Adsorption refrigeration can be may be conventional generators for backup. safely used as a normal refrigerator, water Photovoltaic directly convert solar radiation chiller, ice maker etc. With necessary into electricity with peak efficiency in the structural modifications, an air conditioner range of 9–12%, depending on specific solar can also be designed on the same principles. cell type. More than 80% of the solar Many prototypes are already available in radiation falling on photovoltaic cells is not laboratory scale and are successfully converted to electricity, but either reflected operated. Though they may not be as or converted to thermal energy. This leads to powerful as vapor compressor counter parts an increase in the PV cell’s working and their COPs are less compared to the temperature and consequently, a drop of latter, their major advantage lies in the fact electricity conversion efficiency. that they don’t use any or in some cases very less(10-50W) of electricity. So homes can be cooled in summer without any excess electricity bills. A prototype water chiller based on adsorption and heat pipes is shown below. This can be successfully implemented as a water chiller providing chilled water at 14- 17C. In view of this, hybrid photovoltaic and thermal (PV/T) systems are introduced to simultaneously generate electricity and thermal power. Hybrid PV/T is a combination panel that converts solar energy into both electrical and thermal energy. In 2.3 HYBRID PV/T system applications the production of PHOTOVOLTAIC/THERMAL (PV/T) electricity is the main priority, therefore it is SYSTEMS necessary to operate the PV modules at low temperature, the carrier of thermal energy Hybrid energy system is an excellent associated with the PV module may be solution for electrification of remote rural either air or water.
    • A hybrid PV/T has many heat pump (PV-SAHP) is shown in the applications apart from electricity figure below. A PV-SAHP is mainly generation. They include water and space composed of four major components: PV heating, agricultural crop drying and green evaporator, variable-frequency compressor, houses. water-cooled condenser, and electronic If a PV/T collector is directly expansion valve.Apart from supplementing coupled to a solar heat pump, better cooling the compressor of the heat pump through effect can be achieved. Such a compound thermal energy, this system drives its own system is named a photovoltaic solar compressor from PV panels, thus assisted heat pump (PV-SAHP). In this eliminating the need for external supply. arrangement, the PV/T collector also serves For increasing the efficiency of solar as the evaporator of a Rankine refrigeration photo-voltaic system, we can design a system and is therefore called a ‘‘PV simple photovoltaic tracking system. The evaporator”. While some of the solar energy designed PV solar tracking system offers (the shortwave portion) received at the PV low wind resistance compared to other evaporator is directly converted to designs and it is an efficient energy- electricity, most of the energy is absorbed by conversion system. It may be used in rural the refrigerant as latent heat and the and remote areas as a power source for low- remaining portion is lost to the ambient. The power applications such as cathodic evaporator cooling effect lowers the solar protection systems and domestic power cell working temperature and improves the requirements. Cost analysis of the proposed photovoltaic efficiency. At the same time, PV solar tracking system shows that it is the evaporator pressure and temperature are either cheaper or at least comparable to any elevated because of the solar absorption, and other power generation system for low- consequently the COP of the system is power applications. increased. A hybrid photo voltaic solar assisted
    • 3. CONCLUSION REFERENCES 1) Solar refrigeration options – a state-of-the-art A comprehensive study for the review implementation of solar technologies has D.S. Kima, C.A. Infante Ferreirab, Arsenal Research, been done. Some of the technologies are Sustainable Energy Systems, Giefinggasse 2, 1210 mature while some are still nascent. Vienna, Austria .Delft University of Technology, Nevertheless, solar energy –a low heat Engineering Thermodynamics, Leeghwaterstraat 44, 2628 CA Delft, The Netherlands. source- has a huge potential in small scale International journal of refrigeration (2008) applications. A brief summary of the study 2) Efficient adsorption refrigerators integrated is presented in the next few lines. with heat pipes R.Z. Wang, Institute of Refrigeration and 1) Sorption Air Conditioning and Cryogenics, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200030, Refrigeration which utilizes solar energy China. (in the form of hot water) can resolve the Applied Thermal Engineering (2008) refrigeration and AC needs of a home with 3) Performance evaluation of a hybrid no or very little electricity. photovoltaic thermal (PV/T) system A.S. Joshi a,b,1, A. Tiwari , G.N. Tiwari , I. Dincer , B.V. Reddy. Centre for Energy Studies, Indian 2) Solar Photo Voltaic can supplement the Institute of Technology-Delhi, Hauz Khas, New electricity demand of house but may not be Delhi 110016, India. efficient. A Hybrid Photo Voltaic/Thermal Faculty of Engineering and Applied Science, (PV/T) not only produces electricity, but University of Ontario Institute of Technology also doubles up as a thermal collector (UOIT), Oshawa, Ontario, Canada L1H 7K4. 4) Performance analysis of a photovoltaic heat thereby increasing the overall efficiency and pump reducing the energy payback period. Ji Jie a,*, Liu Keliang a, Chow Tin-tai b, Pei Gang a, As we observe carefully, it is He Wei a, He Hanfeng a obvious that utilization of solar energy a Department of Thermal Science and Energy mostly depends on how efficiently we Engineering, University of Science and Technology of China,Jinzhai Road 96#, Hefei City, People’s harness solar radiation. It involves Republic of China implantation of efficient collectors with low b Division of Building Science and Technology, City radiation losses. Also selection of collectors University of Hong Kong, Tat Chee Avenue, depends on load requirements and economic Kowloon,Hong Kong SAR, People’s Republic of factors. The larger the loads, the more China. 6) Performance analysis of photovoltaic systems: efficient the collector should be as operating A review temperatures are high. The more efficient Anand S. Joshi, Ibrahim Dincer *, Bale V. Reddy. the collector, the more expensive it is. So a Faculty of Engineering and Applied Science, careful study is quintessential before University of Ontario Institute of Technology, 2000 implementing any of these solar techniques. Simcoe Street North, Oshawa, ON L1H 7K4, Canada Renewable and Sustainable Energy Reviews.