Solar Absorption Cooling System Assisted with Geothermal Heat Exchange Technology for Energy Efficient Buildings /

Abstract

This paper presents a study on 3 TON capacity solar absorption cooling system designed and simulated on TRNSYS software. The case study is a lecture room in USPCAS-E, at NUST University Islamabad, Pakistan that is simulated on TRNBuild which is a plugin to TRNSYS. The real parameter of the lecture room are modified with an inclusion of an insulation material to the original specs of buildings envelop in order to reduce the cooling load lecture room. The cooling technology based on renewable that is used to reduce the room heat is absorption chiller which involves both hot water cycle and cold water cycle in order to generate chilled water cycle. In the second system solar water heater are used for generating hot water cycle and cooling tower is used for generating cold water cycle. In the third system solar water heaters are used for generating hot water cycle but geothermal heat exchange system is used for cold water cycle of the chiller. The lecture room is also simulated for cooling using conventional 3 TON AC system. The results of all the different models were collected for parameters such as energy consumed, carbon footprint generated, payback period etc. The result show that cooling load of modified lecture room, when envelop is modified with insulation, decreased to 3 TON from 3.5 TON. The results also indicate that an optimum working Solar Absorption Cooling system for a 3 TON system could be designed using 8m2 of collector area of solar water heater, having 0.4m3 of storage tank volume. The geothermal heat exchange system uses HDPE (high density polyethylene) pipe with a diameter of 2 inches and length 100 meters having horizontal assembly underground. This is enough to exchange heat with the soil in order to maintain thermal comfort temperature zone in lecture room. The results show that using conventional AC system uses 8,735 MJ of energy in order to operate far a whole summer season. The CO2 emission is up to 1.62 ton/yr. The results show that SAC system with cooling tower uses 4,728 MJ of energy to operate for lecture room cooling with CO2 emissions being 0.86 ton/yr, Payback period 12.7yrs. The SAC system using GHX system uses 1,929 MJ of energy to operate. The payback period decreases to 9.7 years with reduction in CO2 emissions to 0.35 ton/yr only. The COP of the system was calculated to be 0.71 in summers and solar fraction of 0.96.