Collector performance indices

Various performance characteristics are used to assess and compare solar thermal systems. The most important ones are the “solar fraction” (SF), the “specific solar energy yield” (SE), and the “solar system efficiency” (SN). The following sections discuss these indices.

To ensure that the reference quantities and energy flows can be clearly assigned, the essential parameters are entered in accordance with their definition and their “position within the system” (Figure 3.2). When selecting the proper components of a large solar hot water thermal system it is best to use analytical modeling tools such as f-Chart or TRNSYS. These computer programs can estimate annual energy collected, storage and heat exchanger effects, system heat losses, etc. Refer to Section 3.3.2 for information regarding these modeling tools.