A garden of flowers that produce- rather than consume-
energy sounds unreal, but that is the concept behind AORA's innovative solar
plant. An odd, bright yellow tulip-shaped tower rises above the dry strip
mountains of Andalucia in Southern Spain.
Surrounded by a sea of solar panels reflecting the sun’s light, this
tower is a gas turbine solar thermal station launched by an Israeli company,
AORA Solar in the Platforma Solara de Almeria solar research and development
park.
AORA, a pioneer of distributed solar thermal technology (DST) based in Israel, set up their first solar "garden" in Kibbutz Samar in the south of Israel in 2009 on a 2300sq metersplot of land. Since it was first switched on four years ago, the plant of yellow tulips has been generating 100kw of power per hour for the grid. But that was only the beginning. Its next plant is located about 35 kilometres from the waterfront city of Almeria in the town of Tabernas.
The new technology developed by the company
encompasses of 52 heliostat solar panels that move along with the sun,
reflecting the sunlight to be collected by a solar receiver. In front of the
group of solar panels, is a 35-meter tulip shaped tower with a solar receiver
and a gas turbine that captures the incoming sunlight transmitted by the
panels. Facing each tulip from the ground are 50 solar panels that focus the
sun's rays into the "bulb" of the flower made of solar receivers,
where the air is heated to nearly 1,000 degrees Celsius. Fitted inside the
"bulb" are 100kw gas turbines that turn thermal energy into electric
energy.
In a single hour, each flower tower is able to
generate 100 kilowatts of electricity and 170 kilowatts of heat energy as a
byproduct. The heat energy can be used for other purposes like desalination and
cooling.
AORA's solar system can operate in various locations
and conditions "as long as it's not too hot and humid", says CEO Zev
Rosenzweig. Unlike other solar power plants that use steam or oil when
transferring energy from solar radiation to the turbine, AORA's smart system
uses pressurized hot air. A compressor pressurizes the air by volume (e.g. one
cubic meter). The amount of energy that can be transferred by the reflected
solar heat depends on the mass of the air that is compressed and sent to the
solar receiver. When the air is hot, its density decreases and after
compression, the volume contains less mass. As a result, the energy transfer to
the turbine is lower than when the air is cool. Furthermore, the tulip tower is
supported by a small diesel fuel tank, which serves as a backup during cloudy
weather and nighttime, enabling it to work round the clock even in
unpredictable weather.
To overcome this weather condition, a very fine water
mist (in amounts much smaller than other solar systems) is sprayed into the air
ahead of intake. When the mist evaporates, it takes the energy out of the air
and leaves it more dense. However, if the relative humidity of the ambient air
is too high, like in Dubai, where it can reach 98%, the system simply doesn't
have enough "material" to work with. But these conditions are rare
and are, therefore, not a setback for AORA's expansion plans.
AORA chief technology officer Pinchas Doron said that
soon there would be much more “power flower” facility towers throughout Spain
and around the world. The company will continue to strive to increase the heat
output by adding an absorption chiller to the system, which will convert the
hot air to cool air.
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