Solar initiative in Africa has rotating dishes to follow the sun

Solar initiative in Africa has rotating dishes to follow the sun
Credit: Ripasso

Writers in Inhabitat and The Guardian are both looking at a solar system and asking the same question: Could this be the world's most efficient solar system? They are talking about a solar electric project in South Africa, located in the Kalahari Desert. Colin Payne, in Inhabitat, said the intense South African sun is made use of by the Swedish company, Ripasso Energy.

The company is using what Payne described as a "small-scale solar concentrator system." That system converts 34 percent of the sun energy into electricity, going straight into the grid, said Payne. He said that is twice as much as traditional solar systems.

Jeffrey Barbee of The Guardian also touched on that point, noting how 34 percent of the sun's energy hitting the mirrors was converted directly to grid-available electric power, in contrast to about half that for standard . "Traditional photovoltaic panels are able to turn about 23 percent of the that strikes them into electricity, but this is cut to around 15 percent before it is usable by the grid."

The test site is in the Northern Cape province, said The Guardian.

The system design involves massive dishes that rotate to follow the sun. Interestingly, they constantly adjust themselves to capture the maximum amount of solar energy possible. They rotate slowly; Barbee described "light clicks and taps" filling the still desert air as they make their adjustments.

The Guardian said, "Independent tests by IT Power in the UK confirm that a single Ripasso dish can generate 75 to 85 megawatt hours of electricity a year - enough to power 24 typical UK homes." The same amount of electricity made by burning coal, the report added, would mean the release of roughly 81 metric tons of CO2 into the atmosphere. (In 2014, IT Power was commissioned by Ripasso to conduct an independent performance assessment of their solar energy system.)

Matthew Humphries, senior editor for Geek.com, described how the CSP system works: A parabolic mirror is combined with a Stirling engine. The mirror dish, he said, looks like a typical satellite dish, but its job is to focus the sun's energy on a "tiny hot point' which drives the Stirling engine.

The hot point powers the engine, and electricity is produced. The project is modeled on this Stirling engine, which is noted for high efficiency compared to steam engines, quiet operation, and its ability to use almost any heat source. Humphries said the Stirling engine is a closed-cycle regenerative heat engine. The engine uses an enclosed gas to drive pistons and turn a flywheel.

It is named after a Scottish minister Robert Stirling, who worked on the invention as an alternative to the steam engine.

This electricity-generating system, which uses no water to produce the , is being tested; The Guardian reported that Ripasso is "on the verge of building its first commercial installation."

Ripasso Energy App. Master Thesis in Interaction Design, Chalmers University of Technology Spring 2014. Christian Fransson

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May 17, 2015
It's the cost per watt that matters, not the efficiency

May 17, 2015
They may be more efficient, but they look large, complicated and very expensive compared to a large area of PV.

JRi
May 17, 2015
Lots of moving parts. Wear and tear maybe a problem.

May 17, 2015
What a bunch of netagrons!

Yeah, . . and they are in the desert with blowing silica, but they are another iteration of our progress in ridding ourselves of dirty fuels. It is a good test. And it looks, smells, and sounds much better than a coal plant.

May 17, 2015
But you can't hear the "light clicks and taps" of the stepper motors over the noise of the sterling engine. They were trying to install hundreds of these things in a nice little valley in Colorado until the noise created by these things was discovered. There are videos on YouTube.

I assume the article's author had no idea about the noise and the quote is intended by the developer to hide the deficiency of the product. Sure you can add mufflers, but that would lower efficiency.

May 17, 2015
Ever hear the draft fans of a coal plant?

May 17, 2015
The following may be tried in uninhabited deserts: (May be it is dangerous or will drive people crazy).
Just make Fans of Windmills with Solar Panels!
If it is not a desert, try Algal ponds to hold fans.

May 17, 2015
How do they protect those shiny mirror from sand storms?

May 17, 2015
somebody should write a ode to part time power.

♫when the lights go out in The Sudan

♫in the jungle the mighty jungle the lights went out tonight

May 17, 2015
It is a true eco-friendly solar system, rotating dishes/parabolic mirrors, much more efficient to cook birds with the power of sun from any direction, preventing them from breathing out more and more CO2 into the atmosphere.

May 17, 2015
I think the most interesting part of the whole article was the use of the Sterling Engine. There have not been a lot of commercial uses of this engine to date.

May 18, 2015
Lots of energy... no where to store it.

May 18, 2015
Lots of energy... no where to store it.
There are lots of power dams in South Africa; that is potential energy storage. Reservoirs do not have a constant source of water; river flow varies from season to seasons and also depend on precipitation which varies from year to year. When there are complementary energy sources, like solar or wind, you reduce the demand on that storage. That is a very effective way to manage reservoirs.

May 18, 2015
The efficiency should be counted against the land area used. I can see a lot of sunlit sand that is doing nothing, so the true efficiency would be lower, and if the block of land was covered by PV cells it may make more power. Still it is an impressive achievement.

May 18, 2015
I AM DIVIDING IT INTO 2 PARTS: PART I
Great. Rotating Dishes to make Free Dishes! Just Set up a Fish pond nearby to feed them the falling birds. The Video Camera should indicate the times when the birds were felled to keep the food clean. A small Restaurant, may be! Big Fish Business Indeed! As long as they are not in the path of Mass Bird Migration, it should be O.K. There must be a way to alert to the number of Bird hits to automatically stop the Rotations. Too Much Ecology. When Science Surpasses Human Brain, Stupidity Starts; Where is the Need to hold onto Carnivores on the Planet?...Including Infectious Pets EXCEPT IN THE ZOOS?

May 18, 2015
ADDENDA: PART II (Calif. house cat sends 3 people to hospital - The feline named Khat suddenly attacks 3 members of the family, who all had serious wounds. Firefighters had to throw a blanket on the animal to get him into a cage. BY JOEL LANDAU Sunday, April 20, 2014, 10:47 AM The Roseville, Calif., nydailynews- A California family was hospitalized after an attack caused by their house cat. Family said their small cat caused wounds to the owner's mother, her sister and her 10-year-old brother). It may be true that lack of Big carnivores means More Herbivores. Who Cares for harmful Carnivores? In this day & age, with Guns, CCTV Cameras, Better Traps & Trucks....FINALLY EXTREMELY IMPORTANT BIOFUEL PLANTS, Piece of Cake to deal with the resulting mess. Gadgets (Eg., P.C, Smartfone) should replace Substandard ANIMALS (Don't leave those even for Substandard People). Too Much ECOLGY. Curb it appropriately!

May 18, 2015
ADDENDA: PART II (Calif. house cat sends 3 people to hospital - The feline named Khat suddenly attacks 3 members of the family, who all had serious wounds. Firefighters had to throw a blanket on the animal to get him into a cage.
So, They wanted to Waste Time & Resources? They want to Shoot People on some pretext or Other? But, You cannot kill a DIRTY, Savage Cat? What kind of Fools in whose midst one has to live, WoW!

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