Concentrated Solar Combined Cycle

Pintail Power’s patented Concentrated Solar Combined Cycle™ (CSCC) technology is similar to LSCC but uses heat from the CSP field rather than electricity to charge thermal energy storage. Many heat sources can be used because the CSCC technology upgrades the energy by using exhaust heat from a combustion turbine to superheat steam to a temperature higher than the heat source.

Industrial process heat from can stored and time-shifted or heat from cyclic or intermittent processes can be accumulated in storage until there is enough energy and the right market conditions to justify combining it with fuel to make electricity. This heat is far more valuable in combination with a combustion turbine using the technology, than in an inefficient Rankine cycle or in low-grade heating applications.

Concentrated Solar Power (CSP) is a source of intermittent heat that benefits from being upgraded by LSCC technology. Parabolic trough CSP heat sources at 400°C are often used with 90bar/390°C steam cycles that require moisture separator reheaters.  A simpler, more flexible, and more efficient steam cycle can be implemented by superheating steam to 470C and using a 70 bar or lower steam pressure. [A lower steam pressure improves storage utilization, by allowing more energy to be extracted per unit, because the cold tank storage temperature is lower.]

CSCC is superior to the Integrated Solar Combined Cycle (ISCC) because it maximizes heat addition from outside the heat recovery steam generator and maximizes the recovery of exhaust heat. The maximum solar electric fraction achieved with ISCC is 13.3% (Hassi R’mel), whereas an LSCC approach could achieve solar fractions about 3 times higher.

Even more important than solar power fraction is the fraction of energy attributed to solar energy as opposed to fuel. On an annual basis, an ISCC plant can deliver no more than several per cent of the energy from the total power plant – most of the energy is derived from gas. This is because there is limited benefit in integrating intermittent solar steam, because integration worsens performance when the solar steam is not available. Although an ISCC with storage could provide solar steam most of the time, the solar-derived power is an insignificant fraction.

CSCC technology on the other hand both increases the power output and makes better use of thermal energy than a typical CSP steam cycle. Taken together, CSCC increases the solar performance more than 10x compared to the best previous ISCC.

CSCC can be added to existing CSP plants to increase capacity and annual energy output, and by time-shifting solar thermal energy away from PV over-generation, increases its value dramatically. Thermal energy from any CSP source can be efficiency coupled, because CSCC accepts lower temperature heat that it subsequently upgrade. And because CSCC makes better use of thermal energy, the marginal cost of storage is cut in half or more.

The CSCC makes better use of the CSP resource to improve a project’s economics, which can be further enhanced, with the addition of electric heaters, to provide grid-connected storage of PV, wind or other resources.