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The Sacramento Municipal Utility District (SMUD), under the Concentrating Solar Power (CSP) Heat Integration for Baseload Renewable Energy Development (HIBRED) program, is demonstrating a hybrid CSP solar energy system that takes advantage of an existing electrical generator for its power block and transmission interconnection.

Approach

SMUD is integrating a high-temperature CSP generation plant together with its Consumnes Power Plant (CPP)—a modern, natural gas-fired, combined-cycle baseload power plant—to produce solar-derived electricity. The 500-MWe CPP consists of two gas turbines feeding a steam Rankine bottoming cycle that operates at 1,052°F (567°C) and 1,811 psia steam. As a baseload power generating facility operating 24 hours a day, CPP is scheduled by SMUD grid operators to run at a specified, constant, achievable output over a block of time ranging from several hours to a full day. Because hot weather coincides with SMUD's peak customer demand, CSP integration provides additional "firm" capacity by increasing the CPP scheduled power generation capacity, with zero added emissions.

The specific technical objective of this project is to extend the on-peak delivery of the CPP power plant using stored thermal energy for a net minimum reliable increase of >10 MWe solar generating capacity. The initial project concept uses 1,050°F (565°C) as the key integration temperature between CSP and the matching operational inlet temperature for the high-pressure turbine. The specific economic objective of the CSP HIBRED integration is to accelerate a pathway to the deployment of practical advanced CSP hybrid systems that can achieve a levelized cost of energy (LCOE) of $0.10/kWh (in real 2013 dollars) or lower by 2016 without subsidy.

Innovation

Current applications of CSP-fossil hybrid plants operate at modest temperatures of approximately 400°C. This project integrates CSP solar thermal energy at working temperatures that match the operational inlet temperature for the high-pressure turbine at 565°C, which results in better solar-to-electric conversion efficiency. This integration leverages the existing the power block components and transmission interconnection switchgear. The proposed technology utilizes the inherent CSP advantage of integrated molten salt thermal energy storage. The operational flexibility of this system accommodates the broad seasonal and diurnal range of the solar resource, increasing practical utilization even in uncertain solar conditions. Furthermore, the system minimizes operational transients affecting the 500 MWe combined-cycle power plant. The net value of the CSP hybrid system to CPP includes:

  • A lower cost and lower risk alternative to a stand-alone solar CSP configuration
  • Improved plant capacity
  • Increased plant efficiency
  • Reduced environmental impact
  • Greater facility productivity

Learn about other DOE competitive awards for concentrating solar power research that are in progress.