Top Plants: El Dorado Energy’s Solar Facility, Boulder City, Nevada

Owner: Sempra Generation
Operator: First Solar Inc.

Sempra Generation has conjured up a market plan for producing merchant photovoltaic (PV) power that is inspired. Working with First Solar, Sempra has developed a finely tuned and standardized 1-MW PV power block that can be replicated as needed. Sempra built the modular PV plant on land adjacent to an existing gas-fired plant to shorten the development period, piggyback the power directly to the grid, and enable existing staff to manage the combined plants’ operation.

The sun-drenched Southwest’s great untapped renewable fuel is the sun. However free the energy from the sun might be, the historically enormous capital costs necessary to convert even a small amount of that energy into electricity more than balances the scales (See sidebar, "Solar Photovoltaic Development Costs.") To improve the economics, a developer has to think outside the conventional grid lines, as Sempra Generation (Sempra) has done in the Nevada desert.

Picking Winners

Sempra Generation, the unregulated, power plant – operating subsidiary of San Diego – based Sempra Energy, has developed a solar project that’s an exemplar for the power industry: the 10-MW El Dorado Energy solar facility (El Dorado), which shares its plant name with a gas-fired plant. The solar facility is the largest thin-film PV project in the U.S. and is located 40 miles south of Las Vegas, adjacent to Sempra Generation’s 480-MW gas-fired combined-cycle power plant. The combined plant sells its energy into the wholesale power markets of the Southwest (Figure 1).


1.    Desert denizens. Sempra’s El Dorado Energy consists of a 480-MW gas-fired combined-cycle plant and a 10-MW photovoltaic (PV) plant. The PV portion of the plant was designed in 1-MW blocks that terminate at one of the 10 small white buildings that contain the panel terminations, two inverters, and a transformer to produce electricity at 4,160 V. All the electricity produced by the plant is then terminated in the switchgear at the power plant. Courtesy: Sempra Generation

El Dorado is unique in that it takes advantage of the synergy possible between a PV project and a combined-cycle plant. Crystalline silicon panels (thin film), in general, cost more to make because silicon is expensive, but they also can convert sunlight into electricity at higher rates than competing PV technologies (Figure 2).


2.    One-man show. Only one member of the El Dorado Energy plant staff is assigned full-time PV system responsibility. Courtesy: Sempra Generation

Sempra picked First Solar to supply the PV system for El Dorado. First Solar, located in Tempe, Ariz., was selected because it could inexpensively supply its cadmium-telluride panels and because the company is rapidly expanding its factories in the U.S. and Malaysia to reduce costs. First Solar manufactured the solar modules and was the engineering, procurement, and construction (EPC) contractor for the project.

PV Projects Heat Up

El Dorado is Sempra Energy’s first solar power generation project but will likely not be its last. "This new solar project is another step in Sempra Generation’s long-range plan to emerge as a leading renewable-energy developer," said Michael W. Allman, president and CEO of Sempra Generation at the plant’s dedication. "The combination of Sempra Generation’s experience in developing power-generation projects in the region with First Solar’s expertise in advanced, thin-film photovoltaic solutions is a natural fit. We look forward to helping the region’s utilities meet state requirements calling for them to include solar, wind and other renewable energy sources in their power portfolios."

Michael Gallagher, vice president of asset management, is responsible for all of Sempra Generation’s fleet of fossil and renewable energy projects. Gallagher told POWER during a plant visit in late October that El Dorado was constructed in only six months. The installation of more than 167,000 solar modules on 80 acres of desert property began in July 2008 and was completed in December 2008. The property is also designated as a renewable energy zone and is leased from Boulder City. The new project’s entire 10-MW output has been contracted under a 20-year power purchase agreement with Pacific Gas and Electric. Although this arrangement seems out of the ordinary, PG&E submitted the best bid price when Sempra offered the merchant renewable energy for sale.

Gallagher did not wish to release the final construction cost of the project, but we can estimate the cost from other sources. The Energy Information Administration (EIA) estimates the cost to install a typical utility-scale PV plant at just over $6,000/kW, and a Lawrence Berkeley National Laboratory (LBNL) report includes a breakdown of installed cost estimates for the largest PV projects now operating in the U.S. The LBNL report notes that the installation cost of El Dorado was a rock-bottom $3.2/WDC, lowest of all the reported systems for the 12,600 kVDC system (10 MW nominal) by a margin of about 40%. If the LBNL estimates are good, then Sempra installed El Dorado for about $40 million, or $4,000/kW.

Gallagher did confirm that he expected El Dorado would finish the year with a capacity factor of 25%. Reasonable economic assumptions suggest that the plant should produce electricity for about $0.20/kWh, ignoring the system’s ongoing maintenance costs, although that number could not be confirmed.

Modular Design Simplifies Development

One of Sempra’s goals in constructing El Dorado was to gain experience with the design and operation of a "small" PV project before moving ahead with plans for larger systems (see sidebar). Sempra’s market plan, however, is much different from those of merchant plant developers chasing opportunities who, more often than not, end up with little to show for the effort. Instead, Sempra envisions that PV projects can be successful and economic to operate if they are constructed adjacent to existing power facilities.

Many synergies can be enjoyed by colocating PV projects with existing plants. El Dorado Energy Plant Manager Kevin Gillespie pointed out that by leveraging their highly qualified and experienced combined-cycle plant operating and maintenance staff, they have reduced the PV plant’s operating costs and improved reliability. Leveraging the plant’s transmission interconnection also gives the PV plant a significant economic advantage over other merchant plant developers in time and cost.

Gallagher also pointed out that by modularizing the plant’s design into 1-MW blocks, Sempra is able to quickly capture and transfer lessons learned to the design and construction of future projects.

In my opinion, Sempra has quickly established perhaps the most rational development program for PV technology development in the U.S. and is on the road to positioning itself as preeminent PV system developer. Gallagher was quick to note that when El Dorado was conceived, there were another 13 PV projects in the NV Energy queue looking for an interconnection agreement. (El Dorado is in the NV Energy service territory, so the plant’s physical interconnection is to NV Energy’s grid.) A year later, all 13 of those projects had been delayed or abandoned; only El Dorado was actually built.

At El Dorado, all the energy produced by the PV field connects directly to the main 4,160-kW bus of the adjacent combined-cycle plant and the plant switchyard. Additionally, the combined-cycle plant’s distributed control system is completely integrated with the PV plant (Figure 3). A single technician manages all aspects of the PV plant, while First Solar provides maintenance and remote monitoring as part of its ongoing support contract. In addition, other technicians have been cross-trained to operate the PV plant.


3.    Tightly knit system. The combined-cycle plant control room staff can monitor the performance of the entire PV plant on a single monitor. This monitor reports that the PV system was producing 9,585 kW when the photo was taken. The remainder of the screens report on the performance and control the 2 x 1 combined-cycle plant. Source: POWER

Building on Success

After one year of successful operation, and with only minor adjustments required on the plant’s design, Sempra is pushing ahead with collecting the necessary approvals from state agencies and obtaining a power purchase agreement to construct a 50-MW expansion of El Dorado. If the regulatory hurdles are cleared this year, the new plant could be up and running by late 2010.

The El Dorado expansion, tentatively called Copper Mountain Solar, will continue to use the tried-and-true 1-MW PV power block design with almost a million PV panels. When completed, the 60-MW integrated PV project may be the largest of its type in the world. First Solar will also provide the panels and EPC services for the expansion project.

Sempra is also proposing the development of Mesquite Solar, a PV plant that would be located adjacent to its 1,250-MW Mesquite combined-cycle plant located in the desert west of Phoenix (a POWER 2004 Top Plant). When fully developed, that project will produce up to 400 MW of PV power. Mesquite Solar was described by Allman as a project that would be developed at the rate of 50 to 100 MW per year, with construction tentatively scheduled to begin in early 2010. Mesquite Solar would build on the knowledge and experience gleaned from El Dorado, although Sempra is also looking at the possibility of integrating some concentrating solar power into the project.

4.    Weather-challenged. During the winter months, the PV systems have little sunlight with which to make electricity. To the right is one of the plant’s 10 power control stations, which contain the inverters and switchgear for enough PV panels to produce 1 MW—when the sun is shining. In the background is the air condenser for the El Dorado Energy gas-fired combined-cycle plant. Courtesy: Sempra Generation

As at El Dorado, the Mesquite Solar project will use existing transmission infrastructure that is sufficient to absorb the additional solar power produced by the project and ship it to electricity markets in Arizona and/or California. Given that the project will be built on land already owned by Sempra, the land is properly zoned, and the project requires no water to operate, Sempra only requires local development permits, which are faster to obtain than state and federal land-use permits that are now holding up other solar energy projects across the Southwest. Once again, the critical path for the project is the signing of one or more power purchase agreements. Given the pressure on California utilities to meet that state’s 33% renewable portfolio standard by 2020, I suspect that contracts for that power will soon be signed.

First Solar recently announced that by year’s end it would have the capacity to produce more than one gigawatt worth of modules per year. First Solar was also the first company to reduce its solar panel manufacturing costs to less than a dollar per watt — a goal reached for production during the fourth quarter of 2008. At that cost, solar power begins to become increasingly competitive with conventional sources of electricity.

—Dr. Robert Peltier, PE is POWER’s editor-in-chief.