The Ivanpah Solar Electric Generating System in California (US), the world’s largest solar power plant, is a concentrating solar power (CSP) complex that uses more than 300,000 mirrors to generate electricity. On 19 May when a small fire shut down a generating tower the mainstream press jumped on the news with headlines announcing something similar to a meltdown at a nuclear power plant. This negative publicity is the perfect opportunity to explain what CSP is, its advantages as well as its challenges and the ultimate role it will play in our renewable energy future.
Concentrating solar energy is not a new concept—in fact it goes back at least 2300 hundred years when the ancient Greeks used mirrors to concentrate the sun’s rays. Today there are four types of CSP technology: Parabolic trough and linear Fresnel systems focus sunlight onto a linear receiver. And dish/engine and power tower both focus sunlight to a point. All of these technologies involve converting sunlight into thermal energy for use in a heat-driven engine. A single CSP plant can generate enough power for 100,000 homes or more, making it a serious player of the utility-scale energy market.
Fire at Ivanpah
After an investigation, NRG spokesperson David Knox reported that “the Ivanpah Unit 3 fire on May 19 was caused by the heliostats (mirrors) being locked in place in preparation for a maintenance activity (maintenance mode) causing the solar flux to briefly move over a portion of the boiler tower. The mirrors were unlocked and moved to remove the solar flux from the tower. We have put in place new safeguards that will prevent this from happening again.” The mirrors are designed to focus sunlight on boilers at the top of three 459-foot power towers, and those boilers create steam that drives turbines, which produce electricity.
Heliostats at Ivanpah. Photo by Gilles Mingasson/Getty Images for Bechtel
Knox added that, “The damage to Unit 3 was primarily limited to the aluminum covering of the insulation around pipes, as well as wiring and some valves which can be repaired relatively easily. We anticipate having the unit back online within three weeks.” Knox recently informed Solar Novus that the unit is back online and that all three are now operating.
Details on the plant
Ivanpah is a 392 megawatt (MW) CSP power tower plant that sits on approximately 3500 acres of land in California, just miles from the Nevada border. It was constructed in three phases between 2010 and 2013 and created more than 2600 jobs for construction workers and support staff. It uses BrightSource Energy’s LPT solar thermal technology that uses 173,500 heliostates, each with two mirrors that focus the power of the sun on the boilers at the top of three towers. The electricity generated is enough to serve more than 140,000 homes in California during peak hours of the day. Output of the plant will reduce carbon dioxide emissions by more than 400,000 tons a year. Customers for the electricity include PG&E and Southern California Edison. Partners include NRG, Google, Bechtel Corporation and the Department of Energy.
- Under production–An article in the Wall Street Journal entitled “Ivanpah Solar Plant May Be Forced to Shut Down,” said that in 2014 the portion of the solar plant that supplies PG&E generated 45% of what the state commission expected, which rose to 68% in 2015. PG&E is asking the California Public Utilities Commission for permission to overlook the shortfall and to give the plant another year, according to the article. Mark Mehos, Program Manager of Concentrating Solar Power at National Renewable Energy Laboratory (NREL) said that while he can’t comment on what the original commitment was he said that, given the relative immaturity of towers at this scale, it wouldn’t be uncommon for a CSP plant to take several years to come to full production capacity.
- High cost–What some consider another downside to CSP is the fact that it’s more expensive than solar PV, and becoming more so as PV prices drop. Mehos pointed out that it’s not a direct comparison. “We don’t expect CSP to hit price points that PV can hit now or in the future. Certainly it doesn’t need to.” Because CSP is dispatchable, meaning that the energy source can be used as needed, and PV is intermittent, there is an inherent value associated with CSP that is not there with PV. CSP is dispatchable because it uses thermal energy storage (TES). Thermal energy storage offers the ability to store the sun’s heat for use when the sun isn’t shining. By incorporating thermal energy storage systems, the cost of power from a CSP plant can actually be reduced and can provide solar power on demand — even when it’s cloudy or at night. To accurately compare CSP to PV costs, NREL compared both CPS-TES with PV-plus-battery. The finding was today CSP with storage is lower cost than PV-plus battery. In addition, prices of some CSP components are dropping, Mehos noted, pointing out that in 2015 the price of heliostats had dropped 35%. Of course all of this could change, as both PV and CSP component costs come down, utility-scale batteries technologies improve and costs come down, etc.
- Bird kill- This is a downside that CSP shares with the wind, nuclear, oil & gas and coal industries. According to the March Wall Street Journal article, more than 2000 wild birds died during a six-month period in 2015. Roughly half were found singed or burned, likely from flying through the areas of intense heat between the mirrors and the power towers. The loss of birds is certainly unfortunate but is not limited to CPV plants. Environmental groups also lambast wind energy for bird kills. And then there’s the nuclear, oil & gas as well as coal industries. An article in US News & World Report, “Pecking Order: Energy’s Toll on Birds,” indicates that at least 5 times as many birds are killed in oil fields as by wind turbines.
Avian Mortality by Energy Source
Solar, low estimate 1000
Solar, high estimate 28,000
Wind, low estimate 140,000
Wind, high estimate 328,000
Oil & Gas, low estimate 500,000
Oil & Gas, high estimate 1,000,000
Source: US New & World Report, 22 August, 2014
The future of CSP
There are currently more than 90 concentrating solar power plants successfully generating utility-scale energy around the world, proving the viability and safety of the technology. (See “Concentrating Solar Power Projects with Operational Plants” ) Nearly 20 plants are under construction and 10 currently in development.
Dubai is currently operating a CSP plant, the second phase of which will make it the largest plant in the world. At a planned 5000MW by 2030, the Ivanpah plant will pale in comparison. In Spain the market for CSP was driven by a strong FiT program, and now the country has 50 operating CSP plants, predominantly using parabolic trough technology.
According to NREL’s “On the Path to SunShot: Advancing Concentrating Solar Power Technology, Performance, and Dispatchability,” Spain is the only country where CSP is “visible” in its national energy statistics, with nearly 2% of its annual electricity coming from CSP plans. Other strong markets for CSP include the Middle East and North Africa (MENA), South Africa, Chile, Australia, China and India. CSP is certainly not without its challenges, but CSP with thermal energy storage (CSP-TES) is highly dispatchable and offers many benefits to the grid, not the least of which is its ability to ramp rapidly as well as provide frim capacity, which is the ability to provide power when it is needed most. This is even more important as renewables such as photovoltaics and wind are added to the grid—both of which are variable. As fossil fuel generating technologies are taken out of use, a combination of an “all of the above” approach with renewables—including CSP-TES—will ensure system reliability while meeting peak demand.
Written by Anne Fischer, Managing Editor, Solar Novus Today