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U.S. Government Identifies Best Solar Energy Zones

Solar panels of the 50-megawatt Silver State North photovoltaic solar project
The 50-megawatt Silver State North photovoltaic solar project in Clark County, Nevada—operated by the Canadian firm Enbridge, Inc.—was the first to be constructed on on land owned by the U.S. Bureau of Land Management. © Enbridge, Inc.

The federal government has identified 17 “zones” on public lands that are well suited to the development of utility-grade solar arrays.

October 23, 2012—The federal government announced last week that it has identified 17 solar energy zones located on the extensive public lands managed by the U.S. Department of the Interior’s Bureau of Land Management (BLM); the zones are located in the six southwestern states with the highest solar resource potential: California, Colorado, Nevada, Arizona, New Mexico, and Utah.

The program aligns with President Obama’s stated intentions to increase the nation’s reliance on renewable energy resources. During last week’s presidential debate he addressed the issue directly, stating, “We’ve got to control our own energy, you know, not only oil and natural gas—which we’ve been investing in—but also we’ve got to make sure we’re building the energy sources of the future, not just thinking about next year, but 10 years from now, 20 years from now. That’s why we’ve invested in solar and wind and biofuels, [and] energy-efficient cars.”

The recently identified solar energy zones, officially designated earlier this month by Secretary of the Interior Ken Salazar, were selected because they match a set of strict criteria developed by the BLM, explains geologist Ray Brady, a manager with the BLM National Renewable Energy Coordination Office, located in Washington, D.C.

The land within these zones is part of a structured program for permitting solar energy projects on public lands, according to the BLM. Private companies may lease land in order to build solar energy arrays that will feed into the transmission grid.

The Department of Energy’s National Renewable Energy Laboratory has mapped out the solar resource potential of the United States, using what is known as a “solar insolation value,” Brady explains. The value is computed by calculating the kilowatt hours, per square meter, per day, available in various regions. “So the first screening that we did was to identify those BLM public lands that have the highest solar insolation value, and the cutoff that we used was 6.5 kw hours per square meter per day,” Brady explains. The number was chosen as the appropriate cutoff point given the production capabilities of current technology and the size of the potential arrays that could be built within the zones, Brady says. “What we’re looking at is areas that have the highest potential to generate the greatest amount of electricity for utility-scale projects.”

The second criterion BLM used was slope: the terrain needed to have a slope of 5 percent or less. “The way that solar projects are built, they need fairly flat terrain,” Brady says. “And we did not want to identify solar development zones and encourage solar development in areas where they’re going to have to disturb a lot of ground with trying to make the ground flat.”

After the BLM considered these two major factors, it then examined where the sites had “conflicts” related to existing wildlife habitats, cultural resources, recreational uses, sensitive plant species, wetlands or other natural habitats, or wilderness values, Brady says. The result was a list of 24 potential solar energy zones, and these were opened up to a public comment period that invited responses and notifications of additional conflicts that the BLM had not previously identified. On the basis of the public comment period, the initially identified 24 solar energy zones—some 677,000 acres—were slashed to 17 zones and a total acreage of 285,000. “And that shows the value of public input,” Brady says.

Brady reiterates that solar power is an important component of the administration’s overall energy strategy. “Whenever you look at electrical generation and energy use in the United States, it is not wise energy policy to look at only one type of generation,” Brady says. By employing multiple means of energy generation the nation can eliminate the constraints introduced by cyclical drops in the availability of specific resources; droughts that affect the generation of hydropower, for example, or a lack of wind or sun that might affect the operation of wind or solar farms. “You have to have a mix of all these technologies to balance out your electrical needs [so] you can provide the best capacity to meet your load that you have in different areas for electrical demand,” Brady says.

Some researchers believe that it will be possible for the United States to become reliant on wind, water (hydropower), geothermal, and solar energy by 2030 (read “Global Reliance on Clean Energy Possible, Practical” on Civil Engineering online). But Brady does not believe that total reliance on just renewable sources will occur in the foreseeable future. “When you talk about clean energy, you need to define what clean energy is,” Brady says. “And clean energy does include nuclear. Clean energy does include natural gas. Clean energy does include ‘clean’ coal.”

Although there is widespread debate about how “clean” coal really is, Brady foresees a reliance on a variety of “clean” energy sources within the next 20 years. In such a scenario, the wealth of such domestic energy resources as natural gas and coal that the United States possesses means that energy costs could remain relatively inexpensive compared with those in European countries, for example, which do not have similar internal supplies, Brady says. “The U.S. is in a fortunate situation, because we do have a lot of domestic fossil fuel resources that can be utilized, but we also have significant renewable energy resources as well,” Brady says. “So I think the U.S. is in a better position [than other countries] to have a more balanced energy portfolio to support our energy needs.”

However, low costs are not guaranteed, and this makes it important to invest in new energy resources early so that that as the technologies improve and energy efficiencies increase, the costs will decrease, he says. “The price of electricity for wind is now very, very competitive with coal and natural gas generation,” Brady says. And “we’re starting to see a trend in solar energy as well.”

The BLM has been processing solar energy applications on public lands concurrently with its preparation of a solar energy zone environmental impact statement approved by Secretary Salazar last week. Five solar energy arrays are already being built on public lands, and one—Silver State North in Clark County, Nevada—is already in operation.


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