First hybrid solar/coal plant operating

Hybrid Coal-Solar Power uses parabolic trough mirrors, CSP receiver tubes, and heat exchangers to preheat boiler feedwater, cutting coal use, emissions, and fuel costs while supporting utility clean energy strategies.

The project was developed by Xcel Energy in conjunction with Abengoa Solar, which developed the solar parabolic trough technology that concentrates solar energy to produce heat.

The demonstration project, which explores solar integration with coal plants at scale, is expected to cut the use of coal at the power plant by around two or three percent, and could be scaled up to cut it by 10 percent.

The system works through a series of parabolic trough solar collectors made of glass mirrors, a common approach in retrofitting power plants with solar technology projects today. On sunny days the mirrors concentrate the solar radiation onto a line of receiver tubes filled with a heat transfer fluid mineral oil. The solar energy heats the circulating oil to about 300°C 575°F. The heated oil is then fed to a heat exchanger where the heat is transferred to water to heat it to around 200°C 407°F before it enters the boiler.

As demonstrated by a Chilean coal-solar project, having hotter water entering the boiler means less coal is needed to heat it and produce the steam that turns the turbine to generate electricity.

Vice president of Xcel Energy, and chief supply officer, Kent Larson, said in a press release that if the project meets expectations it may help “move the use of solar energy one step closer to being a potential technology for improving the environmental performance of coal-fired power plants.”

CEO of Abengoa Solar, Santiage Seage, said the company believed the solar-coal combination would provide a cost-effective way of delivering solar energy.

Xcel Energy’s ICT Program is aimed at developing, commercializing and deploying new technologies for electricity generation, energy storage, and so on, to support the company’s clean energy strategy, aligning with Xcel's shift toward solar across its fleet. Xcel Energy is a major utility company in the U.S., servicing 3.3 million electricity customers and 1.8 million natural gas customers.

Other companies are also developing or evaluating hybrid power generation plants to see if the combination can provide environmental benefits at a commercially viable cost. For example a group or companies have joined with the Electric Power Research Institute to study the feasibility of hybrid coal-solar plants in North Carolina and New Mexico, while in Florida NextEra Energy is developing a hybrid solar-natural gas plant.

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