Concentrating solar power (CSP) systems utilize solar energy to drive a thermal power cycle for the generation of electricity. A key advantage of certain CSP systems, in particular parabolic troughs and power towers, is their ability to incorporate thermal energy storage. Thermal energy storage (TES) is often less expensive than electrochemical storage and allows CSP plants to dispatch power as needed, for example, to cover evening demand or other demand peaks. Current CSP plants typically use oil, molten salt, or steam to transfer solar energy from a solar energy collection field, tower, or other apparatus to the power generation block. Commonly used heat transfer fluids have properties that can limit plant performance; for example, the Carnot efficiency is significantly limited by the upper temperatures of synthetic oil (390 °C) and molten salt (565 °C) heat transfer fluids while direct steam generation requires complex controls and allows for limited thermal storage capacity.
Unlike other CSP systems, inexpensive, ubiquitous sand-like solid particles can be stable at temperatures beyond 1000 °C and can drive high efficiency thermal power cycles for high solar-to-electricity conversion efficiency. The National Renewable Energy Laboratory’s (NREL’s) patented designs enable low-cost, high-performance CSP systems with large-scale energy storage to serve as a dispatchable power generator with a high capacity factor.
Engineers at NREL have developed systems and methods to achieve high thermal performance. (1) One CSP system has a temperature range that can enable multiple power-generation cycles. The system leverages circulating fluidized bed boilers to drive hot gas-solid two-phase flow through a boiler or heat exchanger to heat working fluids. (2) Another method uses reversible redox reactions in a closed-loop system that consists of a high-temperature, high-performance receiver to perform a reduction reaction and a fluidized-bed heat changer for an oxidization reaction. The product of the reduction reaction is stored in a silo in chemical energy form. When supplied to a fluidized-bed heat exchanger, the product releases heat through an oxidization process. (3) CSP power cycle systems including steam, s-CO2, and proven high-efficiency pressurized fluidized-bed gas turbine combined cycle systems (GTCC). The particle-CSP system can be an independent thermal subsystem and integrated with any power-tower solar field.
A near-blackbody enclosed particle receiver is a critical component of the CSP thermal system. Operating at >800 ˚C with reduced thermal losses and with materials that can tolerate >1,000˚C, NREL’s receiver mitigates the issues of salt freezing and stability. Moreover, a novel CSP planar-cavity and cooled-flare particle receiver design addresses the need for a high temperature, specular-reflective material for flux spreading. A planar-cavity configuration for flux distribution matches the solar heat collection with the particle flow and introduces a variety of particle receivers that use the near-blackbody principle adapted to available materials and easy manufacturing methods.
Applications and Industries
To learn more about Improved Concentrating Solar Power Systems, please contact Erin Beaumont at:
ROI 11-92, 12-40, 14-72
Applications and Industries include
- Power generation
- Concentrated solar power (CSP)
- Energy storage.
- Simplified systems’ designs
- Low system cost by inexpensive, stable solid particles
- Reduced installation, maintenance, and operation costs
- Increased efficiency with the high-temperature-driven advanced power cycles