ANALYSIS OF THE ACCURACY OF USING SOLAR TANK ENERGY FACTOR FOR ESTIMATING SAVINGS IN FIELDED SOLAR HOT WATER SYSTEMS

摘要

Utility rebates for solar hot water (SHW) systems are often based on SRCC OG300 savings ratings. Some utilities want to verify the accuracy of these ratings based on field measurements. However, energy savings - the amount of electricity and/or gas offset by the SHW system - cannot be measured directly. Savings are frequently estimated based on equations that use the solar tank's energy factors along with measures of the energy in the solar loop, the solar tank's electric element, and/or the load. We used the TRNSYS model and a SHW testbed to investigate the accuracy of these estimation methods. We modeled two popular SHW systems and computed annual energy savings from these simulations using the OG300 methodology. We applied three popular savings estimation equations to estimate savings and compared them to those measured from the simulations. Similarly, we used a testbed to run short term simulations and compared the measured savings with estimates. Our results suggest that the most accurate savings estimations are based on measured load and electric element energy rather than the energy in the solar loop. Keywords: solar water heaters, energy factor, draw profile, energy savings, installation rebates, utility, monitoring.