SolarReserve submits application to build two concentrated solar power towers

SolarReserve filed a 1041 application with Saguache County on November 8 for two, 100 mega-watt Concentrating Solar Thermal Generating facilities to be located in the southern part of the county. According to a site characteristics study for the concentrated solar energy project done by Worley Parsons, “The SSEP will be constructed as two 100 MW units with each unit containing a circular solar array field containing heliostats, power block, administration/warehouse buildings, evaporation ponds and associated linear facilities (transmission lines, access roads etc).”

The SSEP will be located in unincorporated Saguache County, Colorado, situated west of State Highway 17, south and east of State Highway 285 and north of State Highway 112. Access to the site is off Country Road G, which is located north of the site.

The concentrating solar power projects will be what are commonly known as “Power Towers”, each with a tower 656 feet high filed with a concentrated solution of molten salts, composed primarily of sodium and potassium nitrates, which will absorb heat and store it for use in generating electricity.

The Project is based on concentrating solar-thermal power (CSP) generation technology that concentrates the sun’s rays, heating a working fluid (a molten salt) that captures and stores the heat. Heat is used separately to create steam to drive a conventional turbine-generator to produce electricity.

Included is “a generalized process diagram of the ‘central receiver’ power tower concentrating solar energy technology. The proposed concentrating solar power technology uses heliostats (tracking mirrors) arranged in a roughly circular array around a central tower to focus sunlight onto a thermal receiver at the top of the tower. Molten salt is heated to over 1,000 degrees Fahrenheit as it passes through the receiver and into a “hot” storage tank for later use. To generate electricity, the molten salt is circulated through a series of heat exchangers that convert water into high-pressure superheated steam. When the useful heat has been extracted, the molten salt is returned to the ‘cold’ storage tank and then to the receiver in a continuous cycle from sunrise to sunset.

“The superheated steam is used to power a highly efficient Rankine-cycle steam-turbine/generator to produce electricity in a manner that is similar to any other conventional utility-scale steam-turbine generator. The exhaust steam from the turbine is condensed and returned via feedwater pumps to the heat exchangers, where the high-pressure superheated steam is generated again in a closed-loop cycle. A small amount of the water in the steam cycle is purged to avoid buildup of concentrated impurities within the system. The turbine exhaust is cooled with an air cooled condenser, eliminating the water consumption associated with the typical wet-evaporative cooling process.”

The proposed project, which would be located on approximately 4000 acres, may be done in two phases, each with a power tower and roughly 1500 acres of heliostats. The project would be sited along the existing 230 kV power line that runs north/south through the Valley. According to an appendix submitted after the application, there is currently sufficient power line capacity to handle one of the 100 MW arrays. SolarReserve has faith that additional transmission capacity will be added to support the other 100 MW project.

One stipulation that the Saguache County Commissioners have put on this, and other solar projects, is that they must have a power purchase agreement before they can build. That means that some power company is willing to guarantee that they will buy the power. According to the submitted proposal, “The Project Applicant does not yet have an executed power purchase agreement with an electric utility, and is actively pursuing one. The power output of the Project will enter the grid at a new switchyard along the existing 230 kV line that bisects the site, and will supply the region and elsewhere depending on current demand. It is anticipated that 200 MW of electrical generation relative to utilities’ other power resources is such that the Project Applicant does not expect the supply from this Project to affect the general commodity pricing or overall market functionality of the electricity industry. However, the unique attributes of molten salt storage may lead to new, innovative, and cost-effective power plant operational strategies.” This raises another question about whether the project could meet the needs of the Valley should the transmission line across Poncha Pass become inoperable, although the application does not expressly say so.