The Best Source of Energy from Sunlight: Concentrated Solar Power (CSP)


An aerial shot of Ivanpah.

Ivanpah aerial shot. Credit: The Economist 3/13/2014.

If mankind is going to begin slowing alarming climatic developments, advanced industrial countries must implement construction of Concentrated Solar Power (CSP) systems worldwide – immediately. Along with wind, geothermal and hydro power, utility-scale CSP systems are the most advanced and least-destructive of the viable answers to mitigate damaging climate trends.
Concentrated Solar Power energy, and Electrical Co-generation (the subject of a forthcoming essay) need to be part of a greater U.S. (and world) strategy of environmental sustainability.
These development agendas should be as serious and important as were the race to the moon and Space Programs initiated by the U.S. and the U.S.S.R. during the 1950s and ’60s. Indeed, it is crucial to begin them now.
And rarely has there been a more opportune time. Interest rates are at an eighty-year low. Unemployment and underemployment in thirty advanced countries are at their highest levels since the 1930s. Infrastructure in the U.S. is in the worse shape in sixty years. Youth and minority unemployment are above twenty five percent worldwide.
Industrial countries have come together to create responses to serious worldwide crises before – with the Marshall Plan most recently – and World War II before that. There are no shortages of excellent ideas. One is for an infrastructure bank. Peter Ortzag, former Director of the Office of Management of the Budget, said it distinctly:

“Wouldn’t it be great if we could design an efficient way to channel tax subsidies to state and local governments to invest in infrastructure? Turns out we already have: the Build America Bonds program, which was a huge success in 2009 and 2010, but then expired. Despite no credible argument against it, a divided Congress refuses to reinstate the program.”

An infrastructure bank issues bonds for capital to use for public investment – and in the process creates a large amount of employment. There are few better uses for public funds than constructing large numbers of Concentrated Solar Power plants beginning immediately. An infrastructure bank is the means.
The world needs Concentrated Solar Power (CSP) systems now. They are the most-efficient, utility-scale, renewable-energy-producing technologies known. The U.S. and countries throughout the world must seize this opportunity.
What are Concentrated Solar Power (CSP) systems? Let’s visit the newest one.
Fifty miles south of Las Vegas, near Ivanpah, California, where Interstate 15 crosses the California-Nevada state line, a vast expanse of mirrors reflect the rays of the desert sun onto boilers mounted on three highly visible towers. The Ivanpah Concentrated Solar Power (CSP) or solar-thermal plant opened in February, 2014, and is the largest of its kind in the world. Fully ramped up, it will deliver an average of 377 megawatts (MW) of power, enough for 140,000 homes in southern California.
The Ivanpah CSP plant is one of the latest examples of the use of modern technology to harness renewable energy from the sun’s heat and light. Overall, carbon dioxide emissions are reduced there by more than 400,000 tons annually from not burning fossil fuels. With that benefit, it reduces effects on the natural environment. This is accomplished through land-use efficiency by way of a low-impact mirror (heliostat) layout, which allows the solar field to follow the natural land contours and avoid key vegetation areas.
Stretching over more than five square miles of the Mojave Desert, Ivanpah uses 173,500 dual-mirror arrangements the size of garage doors to concentrate sunlight onto superheated receivers. Power is produced when the heat generated ultimately drives steam turbines connected to electrical generators. The latter process, the “Rankine cycle,” is similar to that used in standard coal- or gas-fired power plants. At a total cost of about $2.18 billion, the project required almost four years and thousands of workers assembling millions of parts to complete.
Concentrated Solar Power plants are far superior to parabolic troughsand photo voltaics, the other two principle solar generating systems, because of their greater efficiency. They are more than twice as efficient as troughs and four times as efficient as photo voltaics. Despite their poor performance for term paper writing service, photo voltaics are being pushed relentlessly by the private sector. As a result, they are securing prime sites and diverting scarce government money and investment capital from utility-scale Concentrated Solar Power plants. This is a severe travesty.
How to Produce Electrical Energy from the Sun
Maximum efficiency is the goal of any electrical power plant, whether hydroelectric, nuclear, gas, oil, coal, wind, geo-thermal or bio-mass. But it is especially true of solar energy because it has such a minimal effect on the environment. And the payoff in CO2 not created and fossil fuels not mined, processed, transported and burned is enormous.
With the exceptions of hydroelectric, photo voltaic and wind power, heat generation and capture are the objectives of any power plant – the higher the heat, the better. High temperatures make energy extraction more efficient because more watt-hours of energy are stored per unit of fluid.
Once high heat is produced, it must be transported, stored, and transferred with minimal loss, ultimately to a heat exchanger containing liquids that conventional generators can utilize. The latest CSP plants achieve these aims in several state-of-the-art ways. First is through the design of the mirrors – heliostats.

Ivanpah power tower - in operation.

Ivanpah power tower - in operation. Credit: Ralph L. Cates 2/17/14.

The heliostats at the Ivanpah plant include mirrors mounted on support structures which continuously focus available sunlight onto three 2,200-ton boilers, about 450 feet in the air with aircraft warning lights.
A single controlling computer is programmed with the latitude and longitude of each heliostat’s position on the earth, and the time and date. The computer keeps the reflective surfaces of the mirrors adjusted to half of the angle between the sun and the stationary boilers. Control signals are sent to shoe-box-sized stepper motors, which constantly align the mirrors. The single computer is a major advantage, allowing CSP systems to be built on sloping or irregular ground. Mirrors can be relatively flat, and plumbing is concentrated in the tower and storage tanks.
Concentrated Solar Power systems with their arrays of dual-axis tracking heliostats concentrate sunlight onto central boilers containing a fluid deposit, molten salts having been proven to be the most effective and low-cost. Within the boiler, the focused light typically heats the salts to over 1,000°F (538°C) which are then piped into thermal storage tanks where it may be stored for up to a week at 98-percent efficiency. A heat exchanger inside the storage tank eventually circulates another liquid (usually a chemical solution similar to radiator fluid) throughout a secondary loop to a generator where it flashes to steam. The steam drives a standard turbine to generate electricity. Expelled steam then has to be cooled and re-liquefied before recycling back to the heat exchanger in a closed loop.
The high operating temperatures permit the plant to use high-temperature dry heat exchangers for cooling the turbine effluent, reducing the plant’s water use – critical in deserts where large CSP plants are practical. These sub-systems allow the latest multi-stage turbine generating systems to achieve fifty percent or more thermal efficiencies, compared to thirty – forty two percent for the best gas-fired plants.
With current technology, storage of heat costs less and is more efficient than storage of electricity using batteries, another distinct advantage of CSP over photo voltaic systems. The molten-salt tanks allow the plant to continue to produce electricity day or night, or after days of overcast weather. If the site has predictable solar radiation, then the plant becomes a reliable source of continuous base-load power for utilities.
Reliability can be improved further, if need be, by installing a back-up system that uses fossil energy, say, in areas that experience more frequent cloud cover. The resulting hybrid system can be designed to work with the CSP plant, which decreases some costs and renders the entire installation more utility-friendly. Solar-gas and wind-gas hybrid power plants connected to a common grid would give year-round and round-the-clock generating ability, and keep costly generating systems producing continuously.
With reliability, unused desert, and no pollution or fuel costs, the obstacles for large deployment of Concentrated Solar Power are cost, aesthetics and land use for the necessary connection to power distribution lines. Although only a small percentage of deserts are necessary to meet global electricity demand, large areas must be covered with mirrors to obtain a significant amount of energy.
There are five principles guide engineers of CSP plants: heat gain, transfer, storage, transport, and insulation.
Research is done continuously on long-storage liquids and superior insulations. Insulation is vital to the transport conduits, as well as to storage tanks. Good insulation prevents heat loss, and therefore energy loss, and increases system efficiency.
Of the variety of fluids tested, including water, molten salts (sodium nitrate, potassium nitrate and calcium nitrate) were found to be the most efficient, cost effective, and practical for the CSP system’s towers and storage tanks. They are liquid at atmospheric pressure, they store thermal energy efficiently lke here, their operating temperatures are compatible with today’s high-pressure and high-temperature steam turbines, and they are non-flammable and non-toxic. In addition, experience with them is widespread as the chemicals and metals industries use them as heat-transport fluids as well.
The optimum salts mixture melts at 220 °C (430 °F) and is kept liquid at 290 °C (550 °F) in the storage tanks. At Ivanpah, three tanks thirtyfeet tall and eightyfeet in diameter for the three 100 Megawatt turbines would provide four hours of backup and allows de-coupling power production from the collection and storage. Insulated tanks can store molten salts for up to a week.
A map of the Southwest depicting potential energy.

The maroon areas produce 8-kilowatts-per-sq-meter-per-day of potential energy. Credit: National Geographic.

Concentrated Solar Power with efficient storage tanks has the potential of displacing both coal- and natural gas-fired power plants.
According to National Geographic Magazine, optimal irradiance of sunlight is 8,000 watt-hours dissertation help per square meter per day in the most favorable western sites. Local irradiance near Ivanpah averages about 7,400 watt-hours per square meter per day.
One heliostat at Ivanpah has a total of 14.05 square meters from two reflecting mirror-surfaces. Total plant reflecting surface for the 173,500 heliostats equals 2,437,144 square meters. (A square mile contains 2,560,000 square meters.)
Two of Ivanpah's three towers visible in operation.

Two of Ivanpah's three towers visible in operation. Credit: Sharon Cates 2/17/14.

The Ivanpah CSP plant generates an average of 377 megawatts of electricity for the 2,751 available daylight hours over a year, or 1,037,000 megawatt-hours of total generated electrical energy – enough for 140,000 homes. (A large, modern nuclear plant may produce more than 9,000,000 megawatt-hours of total electrical energy per year. Hoover Dam presently can produce twice as much, but continuous drought conditions threaten to cut that amount).
The Ivanpah facility created some 1,000 jobs at the peak of construction, eighty-six permanent jobs, and total economic benefits of three billion dollars. The jobs were mostly for Las Vegas, the electricity for San Francisco. As mentioned, total cost of the project was about $2.18 billion.
Concentrating arrays of heliostats are superior in overall efficiency to other solar power generating systems. Far less efficient are parabolic troughs – long troughs of semi-circular mirrors with their reflected light focused on central tubes containing an oil or other liquid medium conveyed to a collector tank containing the heat exchanger. These are only forty- forty five percent as efficient as CSP systems with a similar amount of terrain covered.
A photograph of Solar 1 in Las Vegas.

Solar 1: Las Vegas., NV - 64 MW from parabolic troughs (Note truck).

Photo voltaic (semi-conductor) systems are even worse for utility-scale energy production. These are the flat panel arrays seen on roofs, yards and alongside highways. Tracking systems for them, when used, are less efficient, cumbersome, and add considerable cost. The most efficient photo voltaic systems for desert areas convert up to twenty eight percent of the light into Direct Current (DC) electricity. But to accomplish this, semi-conductors must be cooled, which uses part of the energy produced. The conversion from DC to alternating current (AC) to connect to utilities uses expensive conversion equipment and is prone to heat-loss, damage, and outages. Semi-conductors sometimes fail and drag down the circuit they are incorporated into. They are extra sensitive to diminished sunlight and cloud-cover patches. As with mirrors, the collection units must be kept clean for optimum output.
Photo voltaics work well on residential roofs, high-rise office buildings, mountain top and roadside battery chargers, and medium and small field arrays. They are very important for the renewable-energy mix. But promoting them for utility-sized installations is public fraud; a waste of scarce investment capital as well as government funds. It diminishes the amount of capital available for CSP generating systems.
For space vehicles, the situation is different. Outer-space photo voltaics use magnification and concentration of sunlight to approach forty five percent light-to-electrical energy efficiency. They don’t require cooling, face the sun continuously and use more sophisticated semi-conductors.
Solar-energy-producing parabolic troughs and photo voltaic systems are being promoted and installed on prime solar sites that could have and should have been used for CSP technology. In the press, Concentrated Solar Power systems are frequently denigrated, while photo voltaics are promoted and installed relatively unchallenged. With limited amounts of public capital available, why is it being wasted on less efficient systems? Major suspects: the oil, gas, coal, utilities nexus with their friends in government. Also, photo-voltaic manufacturers and patent holders.
Nellis Air Force Base Las Vegas, NV. Agua Caliente 290 MW Thin Film Photovoltaic Solar Power Plant.

Nellis Air Force Base Las Vegas, NV. Agua Caliente 290 MW Thin Film Photovoltaic Solar Power Plant. Credit: (2) Wikipedia.

If Franklin D. Roosevelt or Dwight D. Eisenhower were president now, with threatening and disastrous climate change occurring, high unemployment, and low interest rates, they would embark on massive building programs, the likes of which the world hasn’t seen since 1941-1945. After all, Roosevelt persuaded the Ford family to build the largest factory in the world, “Willow Run,” to mass produce the B-24 Liberator bombers. The family saw the giant, four-engine aircraft for the first time in January, 1941, and by June, 1944 they were producing one an hour!
Shortly after the end of the Korean War, in 1954, the Eisenhower Administration became alarmed at the rapid slowdown of the economy. His economic advisors worried that the country would again slip into depression. Eisenhower orchestrated the design and construction of the Interstate Highway System and a canal in New York state – public, government endeavors to create work over several years.
Faced with today’s serious problems, President Roosevelt, or President Eisenhower, men who didn’t avoid big ideas, would be building 500 Ivanpahs in all the dry areas of the western states. And they would promote Concentrated Solar Power systems worldwide – over photo-voltaics, parabolic trough systems, or fracking and offshore deep drilling for oil and gas. Immediately.

Ralph and Sharon Cates live east of San Diego. A retired associate professor with a background in engineering and construction, Mr. Cates worked in the Marshall Islands on the early Warning System; Iran on a copper mine; and Dubai on oil and gas projects for Saudi Arabia (ARAMCO), Egypt, Kuwait, and India. He was a major stockholder in Dynatech Electric, which focused on instrumentation, and power and electrical co-generation projects. He finished his career as an engineer for Shasta Electric, which specialized in water treatment and wastewater treatment plants for LA Power & Water, Lake Mead, and Clark County, Las Vegas, as well as SCADA (Supervisory Control and Data Acquisition) systems using fiber optics.

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