Why Solar Hybrid?
Solar Thermal plants generate roughly 25-30% of the total kWh’s they could generate if they were able to operate 24 hours a day, 365 days of the year. Costly thermal storage or a separate fossil fuel usually a natural gas boiler with an efficiency of 33-37% is needed at other times to meet utility demand or PPA requirements. It make more economic sense to add solar components to an efficient fossil fuel plant than fossil fuel components to solar. A Gas Turbine Combined Cycle has an efficiency of 56% and can be integrated with solar in a more efficient manner than ramping up and down a separate inefficient natural gas boiler.
Biomass is considered a renewable energy fuel and in Europe and other areas considered carbon neutral. Carbon is sequestered in the vegetative matter during growth and released when combusted. Additional carbon isn't released into the environment such a coal and natural gas. A fully integrated solar/biomass hybrid will conserve renewable biomass fuel during the day and reduce the facility's carbon footprint by 25-30%. As the sun sets, the renewable biomass boiler ramps up.
Why a Solar Hybrid Retrofit?
With growth in demand flat or even negative in many areas, utilities currently have no need to build totally new power plants. The US Energy Information Agency reports a 3.6% decline in electrical demand for 2009. Adding solar to an existing power plant can help the utility meet Renewable Portfolio Standards and gain valuable operating experience with Solar Thermal.
Why a Solar Direct Steam Generation Hybrid?
Conventional CSP Trough solar power stations use a synthetic Heat Transfer Fluid with an operating temperature limitation of 400C and poses risks of hazardous spills, difficulty with VOC emissions permitting and requires proper handling and disposal. Direct Steam Generation directly from water offers a simple cycle design with fewer parasitic, heat exchanger and pumping loses and easily integrated with existing or planned solar hybrid power stations.
Technology is available to add 17-33% Solar Steam to a Combined Cycle Power Station with minimal capital costs. A very simple Direct Steam thermodynamic concept produces an additional 17-33% of renewable solar steam with a retrofit of only solar superheater collectors. Since the flow is always in a vapor phase, difficulties experienced with a two-phase water/steam flow (boiling water) in a horizontal absorber tube are eliminated.
A Solid Choice
Utility managers seeking to add carbon-reduced firm electricity generation can now look to Solar hybrid technology as a viable choice. Decades of experience have proven CSP Solar technology and recent advances in Direct Steam Generation are reducing its cost.