Test results from a 10 kW{sub t} solar/natural gas hybrid pool boiler receiver

Studies have shown that the ability to dispatch solar-electric energy conversion systems which utilize fossil fuel to augment solar energy has major economic benefits over systems utilizing solar energy only. For hybridization to be effective, the combustion system must be durable, low cost, produce a low level of emissions, and operate over a wide power range. Thermal energy must be delivered uniformly and reliably to the engine during varied operating conditions, such as intermittent cloud cover. A 10 kW, hybrid solar receiver using a natural gas burner to augment solar energy was built and tested. The objective was to demonstrate the concept of using a gas burner to supplement solar energy in providing a constant flow of heat to a heat engine under transient conditions of changing cloud cover with automatic control. In the approach pursued, a natural gas combustor is fitted to a pool boiler solar receiver. The burner delivers radiant heat directly to existing boiler surfaces with recovery of exhaust gas energy to achieve high overall efficiency at relatively low combustor temperatures with low emission. Stable boiling and good overall performance were demonstrated over a wide range of steady-state and transient operating conditions. The program objective was metmore » with on-sun tests conducted at the National Renewable Energy Laboratory (NREL) High Flux Solar Furnace test facility in Golden, Colorado, with constant power delivered to a thermal load at constant temperature over a wide range of solar insolation. In this paper, the basic principles and test hardware are presented and test results discussed.« less