Classification of Solar Domestic Hot Water Systems
Abstract
For commercial reasons it is becoming more and more necessary to have an effective way of classifying solar domestic hot water systems. Customers need a quick advice before shopping and impartial information printed on a label may help. Two indexes are defined, the energy factor and the figure of merit, that can serve this purpose. The energy factor is the rate between the volume of hot water produced in one year and the auxiliary heat needed, (L/kWh), calculated when the daily extraction is 2/3 of the storage volume, (2Vs/3), and the temperature is TDN = 60°C. The figure of merit is the ratio of the energy factor to a theoretical reference yield; in turn, ratio of the total annual volume of hot water produced, at TDN = 60o, to its content in sensible heat. A Transient System Simulation program (TRNSYS) model and new software, (ISO), have been developed on the guidelines of the International Standard ISO 9459-2, as simulation software on which they can be calculated. The draw-back of such procedures result from observing that the values obtained are site-dependent. An alternative classification way is presented, based on a non-dimensional number that is totally site-independent.
Keywords
Solar domestic hot water systems, International standards, Solar systems classification.