Debunking the Myths Behind Concentrating Solar Power With Micro-CSP

(3BL Media/Justmeans) -- Most people think that concentrating solar thermal (CSP) power plants must be large and expensive. Systems are generally based on very large steam turbines with a high overhead cost that can only be amortized over large scale production rates (typically 50-100MW, or more). This amount of power requires thousands of reflectors spread out over a large area. That means it will most likely be sited in some remote area, far from where the power will be used, thereby subject to significant transmission losses.

Aora Solar has developed a different kind of CSP technology that breaks out of this mold.

“Our strategy,” says Zev Rosenzweig, Aora Solar’s CEO and Founder, “is to create CSP that is capable of distributed generation. We take the plant to the user, rather than taking the electricity to the user.”

He calls their system, “micro-CSP technology.”

It is based on a micro gas turbine with a capacity of 100kW, and a compact heliostat (tracking mirror) field, with the heliostats close to the tower. This field directs intensified sunlight on to the solar receiver which is located at the top of the tower. The operating fluid is compressed air, which is heated to 1000 degrees C, and then expanded through a gas turbine.

It’s a hybrid system that can be set to automatically burn biogas or other fuels to heat the air when the sun isn’t shining or if the sunlight isn’t strong enough. This results in a system that can produce renewable power around the clock, 24 hours a day and can continue to produce power even if the sun doesn’t come out for several days in a row.

Rosenzweig considers these systems more nimble than conventional CSP plants, which he refers to as "dinosaurs." Aora's target market is isolated, off-grid villages in developing countries.

“One small plant can easily serve the needs of an entire village on a micro-grid in a manner more cost-effective than individual household PV, without bringing in power from a distant power grid.”

The government of Ethiopia recently signed a memorandum of understanding for several plants after visiting Aora’s demonstration plant in Almeria, Spain. A typical village there, requires around 68 kW, well within the capacity of Aora’s system which seems to be a good fit. Additional units could be added fairly easily.

The compact solar field takes up only about 2,700 square meters, which is about two-thirds an acre. It consists of 45-50 heliostats using parabolic mirrors. These mirrors lose less energy because they are close to the tower. This results in a lower amount of glass per MW, compared to the larger CSP plants.

A Visit to Shams-1: Abu Dhabi's Unique Solar CSP Hybrid Power Plant

(3BL Media/Justmeans) - One of the first questions I asked upon arriving in Abu Dhabi, a very modern city in a very oil-rich country, with a very progressive stance towards renewables, was, why? Besides the obvious fact that unlike some other people, they recognize the fact that their oil won't last forever, and they want to participate in energy after it runs out. But there's something else, too. They would like to see an orderly transition that allows them to steward their resource to make as much out of it as they can.

A great example of that is the Shams-1 hybrid solar power plant, which is located 120 km southwest of Abu Dhabi.
Shams is a joint venture between Masdar of the UAE, which contributed 60%, Total, of France, (20%), and Abengoa Solar of Spain (20%).

This unique plant uses a combination of concentrating solar power (CSP) and natural gas which adds a bit to the cost, but gives it some unique capabilities, including the ability to produce power anytime at all, even at night.

During ordinary operation, the parabolic mirrors, of which there are over 258,000, that cover an area of roughly 2.5 square kilometers, track the sun and focus its rays on a pipe containing an oil-based heat transfer fluid (HTF), which heats it to around 400 degrees Celsius. The heated fluid is then used to boil water, the result of which is used to drive a fairly conventional steam turbine.Natural gas can produce up to 50% of the plant's rated capacity, though under full sun, it contributes only 18% of the energy input. This is done by superheating the HTF to 530 Celsius, a point at which the turbine runs more efficiently. This combination produces 100 MW, enough to supply 20,000 homes here. The power is being supplied to the Abu Dhabi Electric Company through a 25 year power purchase agreement.

Shape of Things to Come? Huge Concentrating Solar Plant Opens in Mojave Desert.

They say that enough sunshine falls on the Earth in one hour, to meet the demands of the whole planet for a year. But how much area is needed to collect what we need? If we divide the area of the earth (196 million square miles) by the number of hours in a year (8,760), we end up with around 22,500 square miles, a little less than the size of West Virginia.

 The massive Ivanpah concentrating solar thermal power—also called concentrating solar power (CSP)—plant stretches out over five square miles, the largest of its kind in the world, has opened in the Mojave Desert, at a site 45 miles southwest of Las Vegas. The plant, which consists of 350,000 tiltable tracking mirrors, each the size of a garage door, can produce 392 megawatts, enough power to run 140,000 homes. The mirrors are focused on three towers, forty stories tall, each containing a boiler. The steam produced from the concentrated sunlight then drives a turbine-generator, much like the steam from a coal-fired plant would. The three-tower system is more space-efficient than a single tower, requiring 25% less land. The plant is also unique in that it uses far less water than other similar plants. The $2.2 billion complex is jointly owned by NRG Energy, Google, and Oakland-based BrightSource Energy. The plant will sell power to PG&E Corp. and Edison International under a 25-year contract.

Throughout its history, response to the project has teetered on the line between the desire for clean, renewable energy, and the desire to preserve open land. In 2012, the government stepped in to designate 17 "solar energy zones" in areas identified as being less wildlife-sensitive and having fewer natural resources. The zones include about 450 square miles in six states—California, Nevada, Arizona, Utah, Colorado and New Mexico.

Despite these precautions, government documents show that dozens of dead birds from sparrows to hawks have been found on the site, some of them with melted feathers. The suspected causes of death include collisions with mirrors and scorching. In November alone, 11 dead birds were found, including two with singed feathers. This was enough for the ever-skeptical Wall Street Journal to refer to the plant as a “$2.2 billion bird-scorching project.”

The bird problem is potentially serious enough to forestall a similar project near the Joshua Tree National Park because of the impact it might have on golden eagles and other protected species.

While the successful commissioning of the plant certainly bodes well for the future of solar energy in America, the question of whether we will be seeing lots more plants like this one is a little harder to answer. Besides the bird issue, which is currently undergoing further study, there is another issue that could effect more decision makers: cost.

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