Concentrating Solar Power to be reborn in the Mojave

During the next months, work will begin on 3.24GW of large concentrating solar power (CSP) plants that have been approved by the California Energy Commission (CEC) and the U.S. Bureau of Land Management (BLM) since August 25, 2010.

Two more projects are in various stages of approval, and if approved at current capacities this will mean 3.64GW at 15 plants in eight projects.

Even if neither of these two additional plants meet final approval this will mean a nearly eight-fold increase in the United States’ CSP capacity, and a more than quadrupling of current global CSP capacities.


When completed, these projects will increase the United State's CSP capacity nearly eight-fold. Courtesy: Abengoa Solar
When completed, these projects will increase the United State’s CSP capacity nearly eight-fold. Courtesy: Abengoa Solar

These approvals were far from certain, and the process has been strongly impacted by a number of factors, most notably moves by the federal government to quickly develop renewable energy capacity.

How this happened bears a closer inspection. It is a complex story where technology, the environment and politics meet, with ramifications not only for the future of this technology, but lessons for other renewable energy development as well.


Initiation in the 1980s: Solar One and SEGS

In 1981, workers commissioned by the U.S. Department of Energy (DOE) began construction near the desert town of Daggett in California’s Mojave Desert, on a project that must have seemed at the time like the work of alien beings.

On 72,650 square meters of former agricultural land near a dry riverbed, workers erected 1,818 mirrors around a central steel tower much like an air traffic control tower. The mirrors reflected sunlight onto a receiver in the central tower, where it heated a fluid used to drive a turbine. The plant they created was based on simple principles, but such a project had never been attempted on this scale; when completed the Solar One plant had a 10MW capacity.

The Solar One plant, the first MW-scale CSP project, was in operation from 1982-1989. Courtesy: Southern California Edison
The Solar One plant, the first MW-scale CSP project, was in operation from 1982-1989. Courtesy: Southern California Edison

The DOE began a second project adjacent to this one in 1984, a 83,000 square meter field containing enormous curved mirrors used to concentrate light to heat a fluid and produce steam, which then drove a turbine. This plant, the collaboration of the DOE and Luz International (Israel), was the first of the Solar Energy Generating System, SEGS I, with an electricity generating capacity of 14MW.

Both plants represent the humble beginnings of a new commercial application of this technology, and a second form of solar electric power. In this case generation is not based on the electrical properties of semiconductors, but on the simple concentration of light and heating of fluids.

SEGS I was followed by eight other plants, jointly developed by Luz and the DOE in Southern California, and the nine plants together supplied 354MW of electricity generation capacity. However, after the completion of the final 80MW SEGS unit at Harper Lake in 1991, construction stopped. The plants continued to produce emissions-free electricity for California consumers; however no more large CSP plants were built in the state in the years and decades to come.


CSP after SEGS: Spanish leadership

However, in recent years other nations seeking to transition from fossil fuels have taken notice of the advantages of this technology. Spain, like Southern California, has large areas with intense, direct sunlight, ideal for CSP.

In 2001 Abengoa Solar SA (Seville, Spain) began construction on a similar plant to the Solar One, the Planta Solar 10, which would finally be commissioned in March 2007. Upon passage of revisions to the nation’s feed in tariff, a flood of CSP plants were proposed and constructed. In slightly over three years, Spain added 12 more CSP plants, to bring the nation to 482MW of CSP power in August 2010, out-pacing the United States’ capacity of 422MW. Spain is on track to continue this leadership, with 16 plants under construction, and dozens more proposed.

The example that Spain has set is being imitated around the world. India’s Jawaharlal Nehru National Solar Mission requires as many CSP plants as PV plants. Several nations in the Middle East and North Africa are either planning or constructing CSP plants, mostly hybrid natural gas/CSP units, and the Desertec Initiative has brought together a number of European companies in a bold plan to build large CSP plants in the Sahara Desert, transporting the electricity generated to Europe via high-voltage DC lines.

During this time, the United States built few CSP plants and only one above 5MW, the 64MW Nevada Solar One plant, with another hybrid plant with a 50MW solar field approved in July 2008. Though more than a dozen companies had proposed large-scale solar plants in the Mojave Desert near the Solar One and SEGS units, some of these applications had waited for years without reaching final regulatory hearings. On the surface, it looked as though this technology would spread across the world but languish in the nation that it was developed in, a victim of lack of will at the policymaking level.


August 2010: Change comes to California

However, starting in the late summer of 2010 everything changed. On August 25, 2010, the California Energy Commission, which regulates concentrating solar power plants in the state, granted final approval to 250MW Beacon Solar Energy Project. The CEC has gone on to approve six other large projects for a total of 3.49MW, with a final one under consideration through a “priority” process. The U.S. Department of the Interior has approved four CSP projects, which join two solar photovoltaic (PV) projects as the first solar plants to be approved on public lands.

Among the plants receiving approval from the two agencies are two enormous projects totaling 1.37GW that utilize a form of heat engine called a Stirling Engine, by far the largest application of this technology to date. In just three months, the United States is poised to again become the world leader in CSP, and to dramatically expand the technology.


The breakthrough and the role of the American Recovery and Reinvestment Act

Engineers, technicians, businessmen and economists tend to see energy technologies in terms of cost per watt, output capacities, capital costs, and other quantitative data. While all of these are important, the far less tangible arena of policy is often the deciding factor in whether or not, at the end of the day, renewable energy plants are built. The development of CSP is no exception. It is generally agreed that the greatest single factor in the regulatory breakthrough represented by the approval of these CSP plants was the American Recovery and Reinvestment Act of 2009 (ARRA), President Obama’s “stimulus package”.

U.S. President Barack Obama's stimulus package provided USD$23 billion to renewable energy industries. Courtesy:
U.S. President Barack Obama’s stimulus package provided USD$23 billion to renewable energy industries. Courtesy:

The stimulus package was the first bill passed during the Obama Administration, at a time when the President was still riding high from his successful election. The stimulus was also aggressive, leveraging USD$787 billion of public funds in an effort to revive the flagging U.S. economy. And while only a portion of those funds were spent on renewable energy projects, the USD$23 billion the stimulus dedicated to renewable energy may be the most profound legacy of the legislation.

However sheer numbers alone do not tell the whole story. Solar advocates including the Solar Energy Industries Association repeatedly cite section 1603 of the ARRA as critical to the industry, which allowed solar developers to apply for an existing 30% solar tax credit as a grant. This grant provides critical assistance at a time when tax equity funding has largely dried up as a result of the recession, and this funding is considered vital for the viability of these eight large projects.

The section 1603 grant comes with an important caveat. As this legislation was meant to spur short-term economic growth, the funds must be used quickly, and all projects receiving ARRA funding must begin construction by December 31, 2010. As a large number of the CSP plants were eligible to apply for stimulus funds, this caveat of the ARRA created a situation that could bring tens of billions of dollars in economic activity to California in the middle of a recession – but only if projects were approved in time to begin construction by this date. These facts were not lost on either the leadership of the California Energy Commission (CEC), or California Governor Arnold Schwarzenegger.

However, the approval of plants through multiple regulatory processes, which in many cases involved not only the CEC, but the U.S. Bureau of Land Management, the Fish and Wildlife Service and the U.S. Department of Fish and game, was hardly a simple task, even under these circumstances.


Inter-governmental cooperation

During the years that projects like the Ivanpah Project slowly worked their way through the CEC, for an outside observer it would seem that little was happening. However, while project plans appeared to be collecting dust, regulators and government officials at both the state and the federal level were making plans to deal with complicated approval processes and unfamiliar technologies. Ultimately, this process of inter-governmental cooperation was critical to speeding the approval process to allow these plants to qualify for ARRA funds.

“We faced the challenge of moving faster with bigger projects and in a situation where both the energy commission and in most of our cases BLM had to make a decision,” California Energy Commission Chair Karen Douglas told Solar Server. “What we did differently is pretty simple – we coordinated very very tightly with the federal agencies, at the staff level.”

Commissioner Douglas traces this co-operation back to a 2007 memorandum of understanding between the U.S. Bureau of Land Management (BLM), which manages certain kinds of public lands in the U.S. under the Department of the Interior (DOI), and the CEC. She says this memorandum, inspired by the Ivanpah proposal, began to formalize the work between the two agencies and divided the labor of reviewing applications.

California Governor Arnold Schwarzenegger has been a key supporter of developing large-scale CSP projects. Courtesy: Office of California Governor Arnold Schwarzenegger
California Governor Arnold Schwarzenegger has been a key supporter of developing large-scale CSP projects. Courtesy: Office of California Governor Arnold Schwarzenegger

California Governor Schwarzenegger’s office was also paying close attention to these large projects, poised as they are to both help the state meet its greenhouse gas goals and bring significant economic development to the desert. In 2008 Governor Schwarzenegger issued an executive order calling on the CEC, the BLM, the Department of Fish and Game and the Fish and Wildlife Service to form the Renewable Energy Action Team (REAT), to coordinate approval processes. CEC Chair Douglas says that the REAT has met every two weeks for about two years at the staff level, addressing issues that staff has encountered with projects, including issues of process. Additionally, Douglas says that the REAT has created a forum for developers, where they could get feedback from the agencies.

The final agreement to tie together the collaborative process came in October 2009, after the passage of the ARRA, when U.S. Interior Secretary Salazar and California Governor Schwarzenegger signed an MOU which confirmed the earlier REAT partnership, and under which the agencies identified CSP projects which they felt they could resolve the regulatory issues with in time to qualify for stimulus funding. The new agreement also dedicated staff from both offices to work specifically on approval of these plants. An additional efficiency created by the new agreement was the combing of documents, so that only one application was needed for the environmental review phase at both agencies.

Finally, CEC Chair Douglas cites a directive signed by Interior Secretary Salazar establishing renewable energy development as a top priority for the DOI, coordinating efforts within the BLM to focus on environmental impact reviews from the plants.

In addition to cooperation, the process of moving these projects through the regulatory process has also involved intense work and strict deadlines. “Where we might have thought it reasonable to give parties a week or ten days to produce briefs, we might have required them to turn them around in three days,” notes CEC Chair Douglas. “We expanded the workday for staff, for applicants, and also unfortunately for intervenors, who I think struggled with the tight timelines.”

CEC Chair Douglas notes that with the strong commitment to achieve this goal came plentiful overtime. “It was not uncommon for us to have hearings late into the night,” she recalls. “We have literally thousands of hours of overtime that staff worked. 1 AM was a fairly common cutoff for hearings, we actually had one hearing go until 4:30 in the morning.”



Conforming to California environmental law

To understand why the approval of these plants represented such a massive effort by the BLM and the CEC, it is necessary to understand the complex legal and regulatory frameworks that applicants had to navigate. Foremost among these are California’s environmental laws, which are considered to be among the strongest in the nation.

Sources close to the process note that chief among the laws that companies had to navigate was the California Environmental Quality Act (CEQA), which was passed in 1970, directly following the passage of the National Environmental Policy Act (NEPA) at the federal level. Both laws require governmental bodies to study environmental impacts before taking major actions (including approving power plants), however CEQA is considered far more strict.

To add to this difficulty, a number of the plants proposing projects – including Tessera Solar North America Inc. (Houston, Texas, U.S.), Abengoa and Solar Millennium LLC (Berkeley, California, U.S.) – are either European companies or the U.S. subsidiaries of European companies. Sources Solar Server spoke to noted that this created additional difficulties in navigating U.S environmental law.

Finally, five of the eight plants in the fast track process – the Blythe, Calico, Genesis, Imperial Valley, and Ivanpah projects – are proposed for public land managed by the BLM, meaning that they must seek approval from the agency and conform to federal requirements.


Endangered species

A major challenge for plant developers was the presence of species identified by the U.S. federal government as “endangered” or “threatened”, under the 1973 Endangered Species Act. The presence of such species means an additional regulatory process through the U.S. Fish and Wildlife Service. Desert Tortoises, a species listed as “threatened” in the Mojave, have been found in at least two of the sites for these plants, and some plant designs have been scaled back as a result of the discovery of Tortoises, including the Calico Solar Project, which was scaled back from 850MW to 663.5MW to reduce impacts on wildlife habitat.


The thorny issue of water usage

The use of the limited water found in desert environments has long been a serious environmental issue in California, and presents specific challenges for CSP. The technology is ideal for areas with constant, direct, intense sunlight, which means arid climates where water use is always an issue. CSP plants use water in several ways; as steam to run turbines, to wash the mirrors and often in the cooling process. Here plant design can be a factor, and both “wet” and “dry” cooling designs for CSP plants have been developed, with the latter using an estimated 95% less water in some designs.

CEC Chair Douglas notes that all but two of the plants approved used dry-cooling designs, with one plant switching from wet-cooling to dry-cooling. Douglas notes that the two plants that use wet-cooling systems both are on private land and have dedicated water resources.


Other factors including visual aesthetics and flash floods

In addition to these environmental concerns, the CEC was tasked with considering other resources, such as visual and cultural resources, with impacts upon the austere aesthetics of the seemingly “untouched” desert considered a factor. In most cases, plants were found to have impacts on visual resources, and the CEC says that such impacts were at times cumulative.

“There were better sites and worse sites,” says CEC Chair Douglas, noting that a number of issues were site-specific. “It’s cultural resources, it’s drainage; some projects might not have had such serious biological or cultural issues, but might have had to totally reconfigure in order to avoid the danger of being swept away by flash floods that happen once every decade or even more often than that.”


Mitigation, or moving tortoises

In many cases, regulatory agencies had three choice: to deny the plants, to over-ride the impacts, or to require some form of mitigation. Mitigation procedures included altering plant designs, reducing plant scales, and requiring developers to purchase additional land for habitat for threatened or endangered species.

Officials close to the process note that in some cases, it has been difficult to find suitable areas to purchase for full biological mitigation.

For some impacts, there simply was no mitigation possible. “The energy commission did not override many impacts, and we don’t have a history of overriding many impacts as being un-mitigable, but in the fuller cases, we did have projects with a fairly substantial list of over-rides,” notes CEC Chair Douglas.

At least two projects were reduced in scale to accommodate for desert tortoises, which is on the federal list of threatened or endangered species.

Courtesy: BrightSource Energy
Courtesy: BrightSource Energy

One prime example of mitigation procedures has been the purchase of land to accommodate for impact on federally listed species. In the largest of the projects, the Blythe Solar Energy Project, developer Solar Millennium has been ordered to purchase 32 square kilometers of habitat for desert tortoises, western burrowing owls, bighorn sheep and Mojave fringe-toed lizards.

BrightSource Energy’s design for the Ivanpah project will allow vegetation to co-exist on the site.

In some cases, whether or not mitigation was required, environmental concerns led to innovative designs being utilized. BrightSource Energy notes that their Ivanpah plants will use a field of heliostats (mirrors) that are mounted on poles driven directly into the ground, instead of sitting on concrete pads. The company says this design removes the need for grading the site and allows for vegetation to be less disturbed.


Solar for base-load and on-demand power; thousands of new jobs

By virtue of their scale, these plants will have significant impacts on electricity generation, the solar industry and the economy of the areas in which they are built, both during construction and when operational. One very significant aspect of CSP that differentiates it from both solar photovoltaics (PV) and wind power is that it does not necessarily represent the same variability in power output. While electricity storage remains a costly venture, CSP plants offer two alternatives: backup natural gas generation and thermal storage, both of which can be implemented at much lower expense than battery storage systems. Thermal storage technologies usually store heat in the form of molten salt, which can be released on demand.

The addition of either of these options can give CSP plants the ability to run for much longer periods of time – often sixteen or eighteen hours a day instead of six. They also give the ability for generation to be turned on and off. The ability to supply “baseload” and “on-demand” power put CSP plants in a competitive position with forms of “traditional” generation, such as fossil fuel and nuclear generation, and these plants can replace coal and natural gas plants in a way that PV presently cannot. These factors are particularly important as California moves towards meeting its goal of 33% renewable energy generation by 2020.

While only one of the plants being considered – the 150MW Rice Solar Project – currently is incorporating a molten salt storage system, parabolic trough and solar tower CSP plants can be retrofitted with molten salt storage. The Ivanpah plants use backup natural gas generation, both for start-up and for times when cloud cover limits plant output.


Stirling engines to hit the big time

Another interesting detail is that these approvals represent a breakthrough for large-scale application of Stirling Engine technology. Stirling engines are heat engines, and Stirling systems typically use large parabolic mirrors to concentrate sunlight onto a working fluid in these engines. As such, they remove the need for the large turbines and central power blocks used in other kinds of CSP designs. Stirling Engine developers also note that this design also uses far less water than other CSP designs, as water is only used for the washing of mirrors, and not in the generation process.

The Imperial Valley Solar Project and Calico Solar Project will use Stirling engine technology. Courtesy: U.S. Department of the Interior
The Imperial Valley Solar Project and Calico Solar Project will use Stirling engine technology. Courtesy: U.S. Department of the Interior

Developer Tessera Solar (Dublin, Ireland) states that its SunCatcher system, developed by sister company Stirling Energy Systems (Scottsdale, Arizona, U.S.), currently has the world’s highest efficiency of any technology for converting thermal energy from the sun into electricity. However, a disadvantage of this system is that as power is converted at the units, these plants can not take advantage of molten-salt storage systems.

The largest operational Stirling Engine plant in the United States is the 1.5MW Maricopa Solar Project by Tessera Solar. However, the two projects approved by the CEC, the 709MW Imperial Valley Solar Project, and the 663.5MW Calico Solar Project, together will add 1.37GW of Stirling Engine CSP, manifesting this technology at a scale which has never before been seen.


Impacts on California’s economy

With the possible exception of Hawaii, California is the state in the nation closest to making activist and author Van Jones’ “green jobs” vision a reality. A significant impact of the development of these plants will be an influx of money and jobs to rural areas in Southern California, and this has been cited as a major factor behind California Governor Schwarzenegger’s push to have these plants developed.

Development of these plants will involve the creation of thousands of construction jobs. Courtesy: Solar Millennium AG
Development of these plants will involve the creation of thousands of construction jobs. Courtesy: Solar Millennium AG

While exact numbers of jobs are hard to pinpoint, the Department of the Interior states that the four projects it has approved – the Blythe, Calico, Imperial Valley and Ivanpah projects – together will create  over 3,000 construction jobs. These four projects are also poised to secure USD$5.66 billion in loan guarantees from the federal government.

During this decade, Concentrating solar power systems (CSP), which focus the light of the sun to generate power, could emerge as the most widely used solar technology in the planet.1 CSP has several distinct advantages that make it the most practical solar technology for many applications: it can be produced at a lower cost per kWh and has more efficient storage options than photovoltaics (PV), it has better economies of scale and wider uses than small-scale solar hot water, and CSP plants can take advantage of existing components and manufacturing processes as they utilize many technologies similar to those used by fossil fuel generation plants.

Concentrating Solar Power: CSP also holds the greatest potential to deliver power and, in many cases, drinking water to those in the developing world who have limited access to both.
Concentrating Solar Power: CSP also holds the greatest potential to deliver power and, in many cases, drinking water to those in the developing world who have limited access to both.

The United States and Spain currently lead the world in both planned and operational CSP. Global development of these technologies is uneven, and, like other solar technologies, is more driven by policies and economics than by solar potential. However, CSP also holds the greatest potential to deliver power and, in many cases, drinking water to those in the developing world who have limited access to both. The solar report on provides an overview on technologies and market development worldwide.

CSP has distinct geographical limitations; even in best case scenarios these technologies will likely not be supplying power to Swedes or Canadians in the foreseeable future. However, for many areas in a large belt encompassing the tropics and some temperate climates, where a large portion of the earth’s inhabitants live, CSP offers an affordable, practical and renewable form of electricity production that can represent a dramatic reduction in greenhouse gas emissions compared to conventional fossil fuel generation.

The scale of concentrated solar is set to increase dramatically as projects in the planning and construction stage come online. More than 800MW of CSP plants are currently operational, and this number will likely reach 1GW around 2011, however in the United States and Spain alone 17GW of plants are planned or under construction.2

Courtesy ACCIONA Energy S.A.; Bell Independent Power
Courtesy ACCIONA Energy S.A.; Bell Independent Power

What is CSP?

CSP is a term for technologies that concentrate the sun’s rays, and can be used for systems that either direct these rays onto photovoltaic solar cells (CPV) or heat a fluid, which is then used to generate electricity via conventional turbines, stored for later use, or used to supply heat for industrial processes. The first kind, where light is concentrated onto a photovoltaic surface is called concentrating photovoltaics (CPV). CSP often refers specifically to systems which heat fluids (which can also be called concentrated solar thermal), and this report uses the term CSP to refer only to these technologies.

There are four main CSP designs currently in use at the utility scale: parabolic troughs, tower systems, parabolic dishes and linear (Fresnel) troughs. Parabolic troughs currently account for over 90% of the generation capacity in installed CSP, however many in the solar industry speculate that tower systems will become more widely used than parabolic troughs in the future.

1. Types of CSP systems

Parabolic troughs

Parabolic trough systems consist of rows of curved mirrors that concentrate the sun’s rays onto a central tube containing the fluid to be heated. The mirrors utilize a tracking system to follow the sun, typically rotating on one north-south axis. The sunlight on the mirrors is concentrated 70-100 times and the fluids are heated to temperatures as high as 400 degrees Celsius. Many of these systems use synthetic thermal oil, which is used to create super-heated steam to run turbines.

(left) The 64 MW Nevada Solar One installation in the US state of Nevada is an example of a parabolic trough system. Courtesy: SCHOTT AG - (right) Solar tower plant by eSolar. Courtesy: Ferrostaal AG
(left) The 64 MW Nevada Solar One installation in the US state of Nevada is an example of a parabolic trough system. Courtesy: SCHOTT AG – (right) Solar tower plant by eSolar. Courtesy: Ferrostaal AG

Solar Tower systems

Tower systems use a field of heliostats (large mirrors with sun-tracking capabilities) focused on a single point in a tower to heat a fluid. Tower systems concentrate sunlight 600-1000 times to heat transfer fluids including molten salts, water, air and other gases from 800 to over 1000 degrees Celsius.

If pressurized gas or air is used as the transfer media, it can be used to directly replace natural gas in conventional gas/steam combined cycle turbine. The 11MW Planta Solar 10 (PS10) and 20MW PS20 towers near Seville, Spain are tower systems.

"SunCatcher" dish stirling engines. Courtesy: CPS Energy
“SunCatcher” dish stirling engines. Courtesy: CPS Energy

Dish engines

Dish engines use parabolic dishes to concentrate sunlight onto a receiver in the focal point of the dish, heating a fluid which then runs a turbine or sterling engine. These technologies typically heat fluids to 750 degrees Celsius.

Linear (Fresnel) troughs

Linear troughs operate similar to parabolic troughs, except that the mirrors used are flat and much of the hardware is simpler. These systems cost less than parabolic trough systems, but are less efficient.

Hybrid systems

Many of the CSP systems in place combine their CSP operation with a natural gas combined cycle turbine to generate power when the sun is not shining. An example of a hybrid system is NextEra Energy Resources’ SEGS plants in California’s Mojave Desert, which utilize a natural gas backup system.


Solar company Sopogy (Honolulu, Hawaii, US) has developed a microCSP system that utilizes technology similar to parabolic trough systems, only on a smaller scale. Sopogy’s SopaNova system has a capacity of 3kW for electricity and hot water production, and is advertised for both on-grid and off-grid applications. In December of 2009, a 2MW plant using Sopogy microCSP units opened in Hawaii.

Left: microCSP system by Sopogy.Right: The world's first MicroCSP plant Holaniku at Keahole Point, Hawaii, Courtesy Sopogy
Left: microCSP system by Sopogy.Right: The world’s first MicroCSP plant Holaniku at Keahole Point, Hawaii, Courtesy Sopogy

2. Technical issues


A major advantage of CSP is easier, more efficient storage than PV systems allow. With adequate storage and/or hybrid backup systems CSP plants can provide both base-load and dispatchable (on demand) power, like conventional fossil fuel plants.3

Power storage for CPS systems typically takes the form of storing heat for later use, as opposed to some PV systems which use battery backup systems to store electric charge. While this solution is typically more cost-effective, there is no one-size fits all solution for thermal storage for the different systems, and solar thermal storage systems must be designed with the type of fluid, operating temperature and pressure, and other factors considered. Many operational systems currently directly store heat using the steam generated or indirectly store heat via molten salt.

Courtesy: Solar Millennium AG
Courtesy: Solar Millennium AG

Systems using concrete and other mediums to indirectly store heat are also in development. For parabolic trough systems, molten salt stands out as a superior heat storage medium, and the Andasol parabolic trough plant in Spain uses molten salt as a storage medium.

Solar Cooling

Cooling is also an issue for CSP. CSP systems are typically cooled using either water or air. The use of water to cool systems can put additional stresses on desert environments, where may CSP facilities are located. However, using air to cool systems means higher investment costs and 5-10% lower efficiencies.

3. The state of CSP worldwide

Courtesy DLR
Courtesy DLR

90% of operational CSP plants are located in the United States and Spain.4 The American Southwest has greater potential and the United States has a slightly larger total installed capacity, however on a per capita basis Spain produces far more power with CSP than the United States. Spain has ten operational CSP plants between 1 and 50MW.5

Much of the concentrated solar power currently in use in the United States was built between 1986 and 1992, in a series of plants in California’s Mojave Desert, the Solar Energy Generating Systems (SEGS), which total 354 megawatts. The United States did not put another CSP plant online until the 64MW Nevada Solar One plant in 2007.

Solar thermal experimental and demonstration power plant in Jülich. The technology for the core of the facility, the receiver, was developed and patented by the German Aerospace Center, DLR, together with the Jülich Solar Institute, provided scientific guidance and support for the planning, design and operation of the power plant.

Australia, France, Germany6 and Israel have all completed CSP systems, however none of these is larger than 2 MW. Germany does not receive enough of the right kind of sunlight to make it suitable for large-scale development of these technologies. CSP plants are under construction in Algeria, Egypt, Italy and Morocco, and of course in Spain. In both Spain and the United States a large number of CSP plants have been proposed.

4. Geography and CSP

CSP systems require different and more specific qualities of sunlight than PV systems. CSP requires Direct Normal Irradiation, which means light that is not scattered by cloud cover, fumes or dust. The best sites are in the tropics and at high altitudes. Many areas in temperate climes which are considered suitable for PV are less suitable for CSP technologies. Sites that considered suitable get 2,000 kWh/year of direct sunlight; optimal sites get more than 2,800 kWh/year.7

The Southwestern United States, Mexico, Australia, Spain, Iran, India, Pakistan, Chile, Argentina, Brazil, as well as most nations in the Middle East and much of the continent of Africa all have areas of strong potential for CSP. Some of the best locations for CSP are in the deserts of Northern Chile, South Africa, Egypt, Libya and Western Australia.8

5. Cost

Costs of CSP production vary according to the solar resource where the plant is located, and levelized electricity costs for currently operational parabolic trough systems range from USD$0.17 – 0.25/kWh, though proponents claim costs can be as low as USD$0.15 in places with very good solar radiation.  As with other solar technologies, the vast majority of the costs are materials and construction, and investment costs range from USD$4.20 – 8.40 per watt, depending on the solar resource and the size of the storage options.9

Costs are expected to decrease 2-5% per year due to innovation in systems and components, improvement of production technology, increase of the overall efficiency, enlargement of operation hours, bigger power blocks, decrease in the O&M costs, learning curve in construction and economies of scale.10

6. Uses of CSP

CSP is typically used to generate electricity, however the heat generated by CSP can also be used for sterilization and for heating and absorption chilling.

Water desalination is one potential use of CSP that has been widely studied. Globally 1.2 billion people live in communities that do not have regular access to clean water. Until now, desalination has been an energy intensive and prohibitively expensive way to meet those needs, however many nations are looking at solar technologies to bring down these costs. Saudi Arabia’s King Abdulaziz City of Science and Technology and IBM are currently pursuing a pilot water desalination project using CPV, and in 2007 the German Aerospace Center published a study on using CSP to desalinate water either using the electricity or the process steam in combined generation.11

The National Renewable Energy Laboratory (NREL) and the German Aerospace Center, DLR, are cooperating on CSP research. Courtesy DLR/Markus Steur.
The National Renewable Energy Laboratory (NREL) and the German Aerospace Center, DLR, are cooperating on CSP research. Courtesy DLR/Markus Steur.

7. Future of CSP


While Spain has an enormous number of CSP plants planned, many of those plants may not be eligible to participate in the nation’s feed-in tariff upon completion, due to caps imposed after an unsustainable expansion of all kinds of solar projects following the increase in Spain’s feed-in tariff in 2007 to EUR$0.18/kWh for solar PV projects between 100kW and 50MW.12The tariff for solar thermal projects had already been increased in 2004.

The latest figures from Spanish solar thermal industry association Protermo Solar show 15 solar thermal plants under construction for a total of 668MW with an additional 35 proposed plants between 8 and 50 MW.

California’s Mojave Desert

Currently the most promising location for CSP is the Mojave Desert in California. California has multiple policies to encourage solar development, not the least of which is the state’s renewable portfolio standard, which sets a mandate for utilities to get 33% of their electricity from renewable sources by 2020.

Currently the California Energy Commission and the US Bureau of Land Management, which manages public lands, have received applications for 12 CSP and hybrid CSP/natural gas projects in Southern California. If all these plants are built, they will add 4.8GW of CSP. Among these 12 proposed projects is the Ivanpah Solar Power facility, which will consist of three separate solar tower projects to total 392 MW.13

The Mediterranean and North Africa (MENA)

While the vast majority of Europe outside Spain has little potential for CSP, solar plant developer Nur Energie has submitted applications for two 50MW projects on the Greek islands of Crete and Rhodes.

Several North African and Middle East nations are also pursuing CSP, but at a rate much slower than Spain and California. In 2004 Algeria became the first OECD nation to pass a feed-in tariff. Algeria is developing a hybrid combined cycle gas turbine and CSP plant at Hassi R ?mel, with 25MW of CSP. Morocco is also constructing a project that includes 20MW of CSP as part of a larger hybrid plant.14  The Kingdom of Jordan was making steps towards a 100MW CSP project in 2008 and 2009, but declined a funding offer in January 2010, stating concerns about repaying the large debt that would be incurred.15

Among North African Nations, Egypt is closest to developing a CSP plant. In Flagsol GmbH (Cologne, Germany) and Orascom Construction Industries (Cairo, Egypt) completed construction of the troughs and lines for a 150MW combined parabolic trough CSP and natural gas plant at Kuraymat, 100 miles south of Cairo.

The Desertec Initiative

Perhaps one of the most ambitious plans for concentrated solar power is the Desertec Initiative. In 2008 the Desertec Foundation was created to advance a plan to generate power in the Sahara Desert with CSP, PV and wind farms and transmit much of this power to Europe via high-voltage DC lines. The plan aims to provide 15% to 20% of Europe’s electricity this way.16

TRANS-CSP MENA energy mix for energy supply and climate protection. Courtesy: Trans-Mediterranean Renewable Energy Cooperation (TREC)
TRANS-CSP MENA energy mix for energy supply and climate protection. Courtesy: Trans-Mediterranean Renewable Energy Cooperation (TREC)

In 2009 twelve European and North African companies and utilities joined forces to create the Desertec Industrial Initiative (Dii). Desertec singles out CSP’s ability to provide base-load power as a key element of the plan, and states that in North Africa and the Middle East, CSP is “the only source that can really cope with rapidly growing electricity consumption”.17

Nur Energie has proposed a project in Tunisia for ten 20MW CSP plants to supply power as part of this initiative. Under Nur Energie’s proposal, HVDC lines would carry this power to Rome, Italy.18

1 IPEA, Global Market Outlook Until 2013, (2009)
2Greenpeace, ESTELA, Solar PACES, >Concentrating Solar Power Global Outlook 2009, p.7
3 Greenpeace, ESTELA, Solar PACES, Concentrating Solar Power Global Outlook 2009, p.32
4 International Energy Agency, Renewable Energy Essentials: Concentrating Solar Power, (2009) (pamphlet)
5 Protermo Solar map of solar installations (2010):
6 Renewable Energy World March 12, 2009:
7 Breyer, Christian and Knies, Gerhard, Global Energy Supply Potential of Concentrating Solar Power, (2009), p. 2
8 Breyer, Christian and Knies, Gerhard (2009), p. 2
9 International Energy Agency, Renewable Energy Essentials: Concentrating Solar Power, (2009) (pamphlet), Greenpeace, ESTELA, Solar PACES, Concentrating Solar Power Global Outlook 2009, p.13
10 ESTELA, Solar Power from the Sun Belt, (2009) p. 20
11German Aerospace Center, Concentrating Solar Power for Seawater Desalination
13 California Energy Administration website:
15 The Jordan Times, January 6, 2010:
16 Desertec website,
17 Desertec Foundation, Clean Power from Deserts, 2009, p. 31
18 Nur Energie brochure, available on the Nur Energie website,

By Christian Roselund,