Utility-scale Power Tower Solar Systems: Performance Acceptance Test Guidelines

Abstract

Prior to commercial operation, large solar systems in utility-size power plants need to pass performance acceptance tests conducted by the engineering, procurement, and construction (EPC) contractor or owners. In lieu of the present absence of ASME or other international test codes developed for this purpose, the NREL undertook the development of interim Guidelines to provide recommendations for test procedures that can yield results of a high level of accuracy consistent with good engineering knowledge and practice. The Guidelines contained here follow the general approach of the earlier NREL report on parabolic trough collector fields, but in this case are specifically written for power tower solar systems composed of a heliostat (reflector) field directing the sun's rays to a receiver (heat exchanger) on a high central tower. The working fluid in the tower receiver can be molten salt, water/steam, air, CO2, or other suitable fluids, each with its own particular attributes.The fundamental differences between acceptance of a solar power plant and a conventional fossil-fired plant are the inherently transient nature of the energy source and the necessity to use a performance projection model in the acceptance process. Two primary types of test runs are to be conducted. The first – the Short-Duration Steady-State Thermal Power Test (Power Test) – measures the thermal power output of the solar system under clear-sky conditions over a short period, during which thermal equilibrium and stable steady-state conditions exist, and compares the measured results to performance model projections for those conditions. The second test type – the Long-Duration Production (or Reliability) Test (Production Test)– is a continuous multi-day energy test that gathers multiple detailed daily thermal energy outputs and compares the results to projections from a performance model. Both clear-sky and partly cloudy conditions are acceptable. Additionally, the functionality of the solar system should be observed with regard to such items as daily startup, normal operation, standby and shutdown.