After Gutenberg

Solel and FPL Energy operate in the Mojave Desert in Southern California the 354 MW, SEGS (Solar Energy Generating Systems). Not only the largest operational solar thermal energy system, but also the largest solar power system of any kind, SEGS is a trough system.

From Renewable Energy Access we learn that “harnessing the sun’s energy falling on just 6,000 square kilometers of desert in North Africa would supply energy equivalent to the entire oil production of the Middle East of 9 billion barrels a year.”

The German Aerospace Center made this estimate based upon the power generated by solar thermal electric power plants “of between 50 and 200 MW in size in different locations across North Africa.”

The study calculated that solar thermal power plants could supply 68 percent of North Africa’s as well as Europe’s electricity by 2050. Cables to transmit electricity from North Africa to Europe have already been built under the sea.

Who knows, staff at the center might even appreciate the United Arab Emirates using the billions acquired for their oil to develop new, renewable energy sources.

Solel Diagram

In any case, such a report comes at a time when significant development of CSP (Concentrating Solar Power) is underway in Spain. As previously noted, SyV (Sacyr-Vallehermoso), one of the largest Spanish infrastructure corporations, is undertaking three solar power plants in Spain with a total capacity of 150 MW and a total overall investment of $890 million. An estimated $500 million will go to the supplier of the technology. Solel parabolic trough thermal technology has been responsible for continuous production of utility scale power in California’s Mojave Desert over the last twenty years.

The RE article used the German proposal as a way to mention Flabeg, “a German-based manufacturer of parabolic trough mirrors for solar thermal power plants. The company recently developed a mirror that can reflect 93 percent of the sun’s rays.” Flaberg wants to sell high precision mirrors, which can concentrate the solar power onto an absorber tube with a diameter of 70 mm or less, in the solar thermal power plant market arising in Spain and North Africa.

The company is set to deliver 210,000 of the high precision mirrors to the 50 megawatt (MW) solar thermal power plant Andasol II, in Spain—the biggest in Europe—by the end of June 2008… Flabeg has already equipped the 50 MW Andasol I solar thermal plant with 210,000 RP 3 mirrors.

Flaberg is using the precision of their reflectors as a selling point. The author of the article, Jane Burgermeister, states that one of these 50 MW solar power plants can generate an estimated, “5 million kilowatt-hours more of electricity for every extra 1 percent of sunlight that is collected by solar mirrors.” (One would assume that estimate is based upon the expected lifespan of the installation.)

RE commentator E.V.R. Sastry notes that the extremely transparent, white type of glass improves the overall reflectivity of the mirror since the light first must pass through the glass. As the light then is reflected by a coating on the back of the glass sheet and passes back through the glass, the shape of the reflector focuses the reflected light on the collector.

Parabolic troughs that concentrate solar radiation onto evacuated tube collectors are commonly used for utility-scale solar thermal electric power plants. The collector tube is enclosed by glass and the space within the tube is maintained at a permanent vacuum, thereby reducing conductive heat loss at high temperature.

Optical characteristics are critical to design, manufacturing, operation and maintenance of the solar field, particularly when required to build a utility-scale solar thermal electric power plant. There is a trade-off because of cost. (See 2007 National Renewable Energy Laboratory report on estimations of material costs. The report compared polished aluminum, thin mirrored glass and silvered polymer film coated aluminum, all of which can make use of recycled materials.) Not only must developers consider reflective ability, but also congruency with design of the support structure and durability over the expected life of the facility. Some prefer metal reflectors because of their lower cost.

Vinod Khosla, an advocate for and investor in solar thermal electric power, has noted that “worldwide, the electric power industry creates 40 percent of total carbon emissions, and electricity use is rapidly growing.” Large-scale, affordable sources of clean power are needed “to meet the dual challenges of economic growth and carbon constraints.” Khosla also has advocated for development of the interconnected electricity system between regions, power brokers, etc. Sophistication in power generation needs to be equaled by elegance in distribution for CSP to be effective.

Arid, semi-desert areas of the world, where there has been the most development of utility grade thermal solar electric power, include Spain, Israel and the Southwestern United States. The Trans-Mediterranean Renewable Energy Cooperation proposes that concentrating solar thermal power stations in the Middle East and North Africa could export electricity to Europe

RE commentator Hussain Alrobaei reminds its readers that MENA (the Middle East and North Africa) is one of the principle regions around the globe that benefits from a higher solar radiance.

There will be a significant market for producing solar electricity under the ideal meteorological conditions in the sunbelt countries of the MENA and transferring part of this electricity to Europe. As proposed recently by the Trans-Mediterranean Renewable Energy Cooperation, concentrating solar thermal power stations in MENA could be used for export electricity to Europe as well as for providing regional freshwater from combined thermal desalination of sea water [1,2]. The electricity produced in CSP plants can be used for domestic needs and export, as well as for additional desalination of sea water through reverse osmosis (RO), if required. The design of such combined solar power and desalination plants can be flexibly adapted to any required size and need. CSP plants can be designed from 5 MW to several 100 MW capacity [3]. Therefore, in the future European mix of energy sources for power generation, CSP can serve to cover base load, intermediate load or peaking load and even to compensate the fluctuations of PV and wind power.

References
1. Hussain Alrobaei , 2007, Novel Integrated Gas Turbine Solar Cogeneration Power Plant/DEC, Halkidiki, Greece ,22–25 April 2007.

2. Hussain Alrobaei , 2006 , Repowering and Modification of Grid Connected Reverse Osmosis Desalination Plants/CIERTA 2006 , Exposiciones y Congresos – Roquetas de Mar (Almería).

3. Hussain Alrobaei,2006, Integrated Gas Turbine Solar Power Plant/ The Energy Central Network/ energycentral.com/centers/knowledge/whitepapers.