Thermal energy storage systems as a key technology in energy conservation

SUMMARYIn this experimental study, solar energy was stored daily using the volcanic material with the sensible heat technique. The external heat collection unit consisted of 27 m 2 of south-facing solar air collectors mounted at a 558 tilt angle. The dimensions of the packed-bed heat storage unit were 6 Â 2 Â 0.6 m deep. The packedbed heat storage unit was built under the soil. The heat storage unit was filled with 6480 kg of volcanic material. Energy and exergy analyses were applied in order to evaluate the system efficiency. During the charging periods, the average daily rates of thermal energy and exergy stored in the heat storage unit were 1242 and 36.33 W, respectively. Since the rate of exergy depends on the temperature of the heat transfer fluid and surrounding, the rate of exergy increased as the difference between the inlet and outlet temperatures of the heat transfer fluid increased during the charging periods. It was found that the average daily net energy and exergy efficiencies in the charging periods were 39.7 and 2.03%, respectively. The average daily net energy efficiency of the heat storage system remained nearly constant during the charging periods. The maximum energy and exergy efficiencies of the heat storage system were 52.9 and 4.9%, respectively.

Section: Introductionmentioning

confidence: 97%

Comparison of energy and exergy efficiencies of an underground solar thermal storage system

Öztürk

2004

“…They developed a general method for the preliminary solar collector design. Dincer (2002) suggested that exergy is more effective and more efficient tool for the performance analysis of thermal systems. Thus, in this paper energy and exergy analyses were applied for evaluating the efficiency of the packed-bed solar air heaters.…”

Section: Introductionmentioning

confidence: 99%

Exergy-based performance analysis of packed-bed solar air heaters

Öztürk

Demi̇rel

2004

SUMMARYThis paper presents an experimental investigation of the thermal performance of a solar air heater having its flow channel packed with Raschig rings. The packing improves the heat transfer from the plate to the air flow underneath. The dimensions of the heater are 0.9 m wide and 1.9 m long. The aluminium-based absorber plate was coated with ordinary black paint. The characteristic diameter of the Raschig rings, made of black polyvinyl chloride (PVC) tube, is 50 mm and the depth of the packed-bed in flow channel is 60 mm. Energy and exergy analyses were applied for evaluating the efficiency of the packed-bed solar air heater. The rate of heat recovered from the packed-bed solar air heater varied between 9.3 and 151.5 W m À2 , while the rate of thermal exergy recovered from the packed-bed solar air heater varied between 0.04 and 8.77 W m À2 during the charging period. The net energy efficiency varied from 2.05 to 33.78%, whereas the net exergy efficiency ranged from 0.01 to 2.16%. It was found that the average daily net energy and exergy efficiencies were 17.51 and 0.91%, respectively. The energy and exergy efficiencies of the packed-bed solar air heater increased as the outlet temperature of heat transfer fluid increased.

“…Laboratory grade paraffin waxes have been tried as PCMs for cool storage by Cho and Choi (2000), and He and Setterwall (2002). Dincer (2002) presented a detailed study on thermal energy storage (TES) systems. He discussed three major aspects of TES systems that includes economical aspects, energy conservation and environmental aspects.…”

Section: Introductionmentioning

confidence: 99%

Performance analysis on industrial refrigeration system integrated with encapsulated PCM-based cool thermal energy storage system

Cheralathan

Velraj

Renganarayanan

2007

SUMMARYCool thermal energy storage (CTES) is an advanced energy technology that has recently attracted increasing interest for industrial refrigeration applications such as process cooling, food preservation and building air conditioning systems. An experimental investigation on the performance of an industrial refrigeration system integrated with encapsulated phase change material (PCM)-based CTES system is carried out in the present work. In the experimental set-up a vertical storage tank is integrated with the evaporator of the vapour compression refrigeration system. Effect of the inlet temperature of heat transfer fluid (HTF) on the temperature variation of the PCM and the HTF in the storage tank and the performance parameters namely average rate of charging, energy stored, specific energy consumption (SEC) of the chiller with and without storage system are studied in detail. The effect of porosity variation in the storage tank is also studied. A 18C decrease in evaporator temperature results in about 3-4% increase in SEC and 18C decrease in condensing temperature leads to 2.25-3.25% decrease in SEC. The range of HTF inlet temperature and porosity values for optimum performance is reported.