A discussion on performance parameters for solar-aided absorption cooling systems

Abstract

The overall performance of solar-aided heat pumps or air conditioners may be evaluated by first law based efficiency (i.e. COP), or second law based exergy-efficiency (effectiveness). However, it is usually desirable to separately investigate the contribution of solar energy. For this purpose, a parameter called the Fraction of Non-purchased Energy and defined as the ratio of solar originated (i.e. non-purchased) heat input to the total energy input is often used. While this ratio is satisfactory for a heating mode, it does not have a clear meaning during the cooling mode. This is because the value of this ratio could be high, either because solar energy is used effectively or possibly wastefully. Therefore, another parameter must also be defined and used to show how effectively the solar energy is used by the system. The ratio proposed for this purpose is to be named the Solar Performance Coefficient (SPC) and is defined as: SPC=1−( Q aux Q load ) where Q aux is the total auxiliary energy input, including pump works, and Q load is the cooling provided by the system.