Energy and Availability Transport Losses in a Point-Focus Solar Concentrator Field

This paper presents the results of an experimental study of the losses in transporting thermal energy from a field of 114 point-focus solar collectors to a central thermal energy conversion system at the Solar Total Energy Project (STEP), Shenandoah, Georgia. Conduction and convection heat losses from the collector field piping and solar collector receivers and radiant energy losses from the solar collector receivers were measured. At normal operating conditions the steady state heat losses per unit of collector aperture area are 130 W/m² (41 Btu/hr-ft²). The thermal mass of the collector field was found to be 3.92 kWh/°C (7,440 Btu/°F), which implies that 17 percent of the energy collected on a typical day is used to warm the field piping to its operating temperature. The loss of availability from the collectors and the field piping shows that only 21 percent of the available solar energy falling on the collector field is delivered to the power cycle for conversion into electricity.