A large-scale parabolic trough is one type of technology used for concentrating solar power. Photo courtesy of NREL.
In a major speech last week, Secretary of Energy Steven Chu declared that the United States is in the midst of a “Sputnik moment for clean energy development,” and that now is the time to win the clean tech race with China. He cited accelerating innovation as one of the key ways to ensure that we meet our country’s energy goals and be the world’s leader in clean energy.
Read more in our renewable energy series:
- Wise planning will aid blueprint for national approach to solar energy
- Renewable energy on our public lands: Let's get it right
- Shaping Renewable Energy: How we can minimize the environmental impacts
- Guiding solar to the best places
- Using biology and science to guide development
- Technology will drive America’s race to a clean energy future
So what does Secretary Chu’s commitment to technology innovation mean for renewable energy on our public lands? It turns out that impacts from solar energy on lands and wildlife are somewhat dependent on the technology used, and so innovation is important to minimizing those impacts. According to research conducted for The Wilderness Society by a team of student researchers at the University of Michigan’s School of Natural Resources and the Environment (SNRE), “the type and severity of the potential impacts that solar development may have on an ecosystem are also influenced by technology type.”
We’ve pulled together a primer on solar technology types. There are two main solar technologies: photovoltaic (PV), which turns sunlight into power through a chemical process, and concentrating solar power (CSP), also referred to as solar thermal, which focus sunlight to create heat and then electricity. There are a few different types of CSP technologies, such as parabolic trough, dish/engine, and power tower.
Difference in water use is an excellent example of how different solar technologies can have varying environmental impacts. Water is used in solar energy production in two ways, the first being to wash dust off of PV panels or CSP mirrors to maintain their efficiency. Many CSP projects also use water to cool and re-condense steam, much like conventional power plants do. One important exception for CSP projects is dish/sterling technology that does not use water for cooling. PV projects also do not require water for cooling.
Water requirements for cooling are much greater than those for simply washing mirrors or panels. However, there is also a great range within cooling requirements, with facilities that employ fully “wet” cooled systems using the most water, “dry” cooled systems (that use air to cool, like your car radiator) using the least, and “hybrid” systems that employ both wet and dry cooling using moderate levels of water. The tradeoff for using dry or hybrid cooling systems is a decrease in efficiency and increase in land requirements to produce the same amount of power.
Land use is another important way that technology can minimize impacts. Because they must track the sun for as long as possible during the day, all solar farms require land to be graded nearly flat. Some technologies require less grading, such as the dish/engine and power towers that require grading to only 6%, versus parabolic trough that requires about 3% slope. As the SNRE authors point out, “Although this may seem like a minor difference, a slight change in the pitch of the land can result in the need to grade a considerably larger portion of the project site.”
The SNRE study also looked at land use efficiency for different technology types, although it is important to remember that this analysis was based on a very small sample of only 13 projects. Nevertheless, it demonstrates that the proposed technology matters in terms of land required to generate the same amount of power.
The Department of the Interior will be addressing this issue and more in its plan for solar development on public lands, expected to be published on or around December 17, 2010. Unfortunately, the BLM’s current process for reviewing applications for solar energy permits does not include a way to prioritize more efficient project proposals. TWS will be asking for your help in calling BLM’s attention to ensuring the agency making smart use of our public lands by accounting for the role technologies can play in minimizing solar’s impact on lands.
"Let's seize this opportunity," Chu said last week. "We can't afford not to." We could hardly agree more. With the ongoing development of the Solar PEIS, we now have the chance to shape solar energy policy on our public lands for years, even decades to come.