A proposal for a new 400 megawatt solar thermal power plant has been submitted to the California Energy Commission. To be known as the Ivanpah Solar Electric Generating System (ISEGS), the facility will be built 4.5 miles southwest of the town of Primm, Nevada and just to the west of Ivanpah Dry Lake in Southern California’s Mojave Desert.

The company behind the prject is BrightSource Energy who, through their wholly owned subsidiary Luz II, are responsible for product development, engineering and solar field supply. At this stage a long term power purchase agreement is still being negotiated, with the likely partner to be Pacific Gas & Electric Co.

The new solar energy facility will actually consist of 3 concentrating solar thermal power plants that are each based on Distributed Power Tower (DPT) and heliostat mirror technology. Construction will be carried out in a phased approach with two 100 megawatt phases (known as Ivanpah 1 and Ivanpah 2) and a 200 MW phase (Ivanpah 3). Each of the 100MW sites would take up around 850 acres and would consist of 3 tower receivers and arrays; the 200 MW site would take up around 1,600 acres and would consist of 4 tower receivers and arrays.

Following an anticipated licensing process by the California Energy Commission, construction would not be expected to begin until early 2009, with a completion date by the end of 2012. The first 100MW plant would expect to begin commercial operations in the 4th quarter 2010, the second 100MW is expected to be ready by the end of 2011 and the final 200MW will complete the project in 2012.

How the Ivanpah Solar Electric Generating System Will Generate Electricity

DPT technology will be utilised in the harnessing of concentrated solar thermal energy emanating off heliostat mirrors arranged in asymmetrical arcs around the towers. Each mirror tracks the sun throughout the day and measures 7.2 feet high by 10.5 feet high giving a reflecting surface area of 75.6 square feet. At this stage it is unclear how many heliostat mirrors will comprise the entire power plant.

Courtesy BrightSource Energy

The receiver, which is a radiant forced circulation steam boiler located at the top of the DPT, will convert water to superheated steam at temperatures up to 565 degrees C. The pressurised steam will then power a Rankine-cycle reheat steam turbine with excess passing to a reheat tower adjacent to the turbine. Additional heliostats will be located around the perimeter focusing on the reheat tower, which will allow a prolonged generation period when the sun is not shining.

Each power plant will also include a partial-load natural gas fired steam boiler to assist the plant in coming up to operating temperature more quickly in the morning. These boilers will also be used during transient cloudy periods to maintain the turbine on-line and ready to use.

Ivanpah 1, 2 and 3 would then be interconnected to the Southern California Edison (SCE) grid with a substation between the Ivanpah 1 and 2 project sites. The existing 115 kV transmission from the El Dorado substation would have to be replaced with a double circuit 220 kV line that would be connected to the new substation.

Expected Electricity Production

The projections are that ISEGS will have the capability to produce enough electricity to power 250,000 homes per year and will avoid over 500,000 tons of carbon dioxide emissions each year.

California Energy Commission Status Report

On 21 March, 2008 the California Energy Commission in partnership with the Bureau of Land Management (BLM) issued the first status report on the progress made in processing the application for the Ivanpah project.

The report identifies a few “technical issues” such as data requirements that were not supplied by BrightSource for things such as an air emission offset package, land use issues and impacts on public lands and compliance with both NEPA and CEQA.

The report also states : “BLM has evaluated the applicant’s conceptual site design drawings and is concerned that the on-site check dams and diversion berms will not adequately address erosion control for the site, nor will these limited erosion control measures protect adjoining public lands.”

A long list of pending data requests are also highlighted with the final statement warning that the commission staff cannot maintain the original schedule as a result. This could be the first sign that, should the project be allowed to go ahead, the projected completion dates may not be met.

Update April 3, 2008

Brightsource Energy Inc signed the purchase power agreement (PPA) with California’s Pacific Gas and Electric Company (PG&E) for the project. The first 3 contracts cover a tital of 500MW with an additional 2 options signed for another 400MW.

With the signing of the PPA, BrightSource is now obligated to obtain the financing to build the solar power station. Luz II will be launching a commercial pilot plant in Dimona in the Negev Desert in a few weeks.