Overview of California Effective Area Metric
Effective Area (Ae) is a metric developed to allow the performance of common types of liquid heating solar thermal collectors to be compared using a single value. It assumes climate conditions associated with the U.S. State of California.
Effective area normalizes the area associated with solar thermal collectors to account for differences in the geometry and overall efficiency of different collector models. For example, it accounts for the spacing between individual evacuated tubes and the non-symmetrical geometry of tubular collectors. It uses the collector’s efficiency equation expands it to account for off-peak performance where the sunlight strikes the collector at an angle. Click here for more details on the calculations used to generate effective area.
The metric is used by some programs in California to set incentives and rebates for certain types of solar water heating systems. Effective area is available for all flat plate glazed and tubular solar water heating collectors certified under the OG-100 program using the ICC-SRCC Effective Area Calculator.
The effective area metric concept was developed by Jeff Thornton of Thermal Energy System Specialists, LLC (TESS) in 2020. Its correlation with annual energy savings for various types of solar water heating systems was the subject of several studies published by ICC-SRCC and TESS in 2021 and 2022.