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Solar thermal hybrids to augment generation from natural gas and coal

Two technology demonstration projects will demonstrate how power utilities can add solar thermal facilities to their fossil-fuelled power plants, and reduce emissions and fuel costs as a result.

The Electric Power Research Institute (EPRI) says both projects involve adding steam generated by a solar thermal field to a conventional steam cycle, to create a ‘solar hybrid’ plant. One demonstration will be hosted by Tri-State Generation & Transmission Association at its 245 MW coal-fired Escalante generating station in Prewitt (New Mexico) while the other will be hosted by NV Energy at its 1102 MW gas-powered Lenzie facility near Las Vegas.

“Solar thermal hybrid applications have the potential to be an important, low-cost option for adding solar power to the generation fleet, allowing utilities to meet renewable energy regulatory targets, reduce plant emissions, and lower fuel costs,” explains EPRI.

The hybrid solar thermal system will inject solar-generated steam into the steam cycle of the fossil plants, and the approach solves the intermittency challenge of integrating solar power onto the grid without compromising the reliability of supply.

Data collected from the solar thermal hybrid projects will be provided to the industry and the general public by EPRI and the plant owners / operators through collaboratives created to support the host sites in selecting the integration design. They will conduct independent plant performance monitoring, evaluation and economic assessments of their planned projects.

“These projects will seek to demonstrate a near-term and cost-effective way to use solar energy at commercial scale,” says Carolyn Shockley of EPRI. “This is a key step along the road toward taking full advantage of technologies to lower the industry’s carbon footprint.”

The demonstrations will be conducted in conjunction with construction of new solar thermal facilities, and EPRI will provide support through all phases. It will rely on its expertise in solar technologies, including two studies on solar-augmented steam cycles that were completed last year. EPRI holds two patents in solar steam cycle optimisation.

The collaborative will help select solar thermal designs that can achieve the desired cost and performance targets, while maintaining the availability and reliability of the existing plant; develop plans for the hybrid plant performance evaluation and testing; and then carry out performance monitoring and evaluation, component testing, economic assessment, and reporting of operating parameters during plant commissioning.

EPRI is supporting 9 industry technology demonstrations as part of its efforts to develop a ‘full portfolio’ of technology approaches needed to make substantial CO2 emissions reductions while minimising economic impacts. Its analyses found that deployment of a full portfolio of advanced technologies (including carbon sequestration) could reduce US electric sector CO2 emissions by 2030 to pre-1990 levels. EPRI currently is working on a global analysis to show similar energy mix changes and significant economic impacts.

“Tri-State is investing in leading research in a number of innovative renewable energy technologies that bring value to our member cooperatives,” explains Ken Anderson of Tri-State. “We are intrigued with the positive results of EPRI’s solar augmentation study that was conducted at our Escalante generating station, and we are extremely interested in further exploring the practical application of this breakthrough technology that could further advance the efficiencies at one of our existing facilities.”

“We are excited about the possibility of integrating solar steam into one of our conventional natural gas fuelled power stations,” adds Tom Fair of NV Energy. “We anticipate this could be a great way to increase our use of solar energy, reduce overall emissions and maximise the use of our existing assets.”

Based in Denver, Tri-State is a wholesale electric power supplier owned by the 44 electric cooperatives that it serves. It generates and transmits electricity to its member systems over a 250,000 square-mile service territory in Colorado, Nebraska, New Mexico and Wyoming.

Headquartered in Las Vegas, NV Energy is a holding company with Nevada Power Company and Sierra Pacific Power Company as its major subsidiaries. Serving a combined service territory of 54,500 square miles, it provides energy services and products to 2.4 million citizens of Nevada and 40 million tourists a year.

EPRI conducts research and development on generation and consumption of electricity. Its members represent 90% of the power capacity in the United States, and international participation extends to 40 countries.

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Comments

hussainaa said

16 January 2010
As energy costs continue to rise worldwide, innovators desire to seek out new technologies to meet the rising demand for sustainable energy. Finding an inexpensive and reliable source of energy is a challenge in many developed and developing countries. Advanced technologies, mass production, economies of scale and improved operation will together enable a reduction in the cost of solar electricity to a level competitive with other power sources within the next 10 to 15 years. However, The performance of concentric solar plants depends not only on the energy demand, but also on meteorological conditions, and of course, on its design [1,2]. The availability of solar power is restricted by the natural fluctuations of the energy source. At a first glance, this seems to limit severely the possibility of generating high-revenue peak-load power as well as low-cost base load power. But the mentioned drawbacks can be reduced by two technical solutions: The first solution is the hybridization of the solar power plants with fossil backup systems. In this case, fuel is used as additive energy source to complete the desired energy output of the plant. Only the hybrid concepts offer high power availability for base load and for peak load operation, which makes them the most suitable for utility application. The second solution is the integration of energy storage systems into the solar plant . In combination with an augmented solar collector field, storage allows an increase in annual solar operating hours and compensates short time fluctuations in the solar energy input.
In addition to that Integrated Solar Combined Cycle power Plants (ISCCP) with their capability of thermal energy storage and of solar/fossil hybrid operation can provide firm capacity and thus are a key element for grid stabilization and power security in such a well-balanced electricity mix. the ISCCP will allow for a flexible transition from the present Combined Cycle Power Plants based on fossil fuels to a future plants based to a large extend on solar energy . Being one of the most effective technologies in terms of technical, economic and environmental sustainability [1,2]. For the case study (ISCCP with annual share of solar thermal power generation 42.2 %) the economical effect amount 187.9 ton fuel / year for each MW design thermal energy of parabolic solar collector array [1]. The corresponding decrease in exhaust gases emission (nitrogen oxides (NOx) 294 kg/MW.year, carbon dioxides (CO2) 679.9 ton/MW.year).

1. Hussain Alrobaei,2006, Integrated Gas Turbine Solar Power Plant/ The Energy Central Network/ energycentral.com/centers/knowledge/whitepapers.
2. Hussain Alrobaei , 2007, Novel Integrated Gas Turbine Solar Cogeneration Power Plant/DEC, Halkidiki, Greece ,22–25 April 2007.

robtemery@msn.com said

12 January 2010
It is amazing what a big organization and hype can do for you. A Biomass/Solar hybrid was developed and marketed by Bethel Energy and LP Daniel Engineers for years. Bethel 3 & 4 is now San Joaquin Solar 1 & 2. CCI Energy (now defunct) was offering a solar/combined cycle years ago and one was to Nevada Power. I suggested to EPRI about utilizing solar direct steam technology as a fossil hybrid. I am glad to see we still have people in this country with original ideas..

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