CAJ: Advanced infrastructure megaprojects - Desertec #5 (How?)

 Desertec

How?

The Desertec concept applies all kinds of renewable sources, though solar power has a special role because of its tremendous intensity. “Within six hours, deserts receive more energy from the sun than humankind consumes within a year.” If we take a 300x300 km2 piece of desert land, equipped with solar collectors, it would generate 18.000 TWh per year and thus enough energy to provide the world demands of electric energy of the year 2005. For the EU-MENA region less than half of it, a total surface of 120x120 km2 would be needed.

The basic idea is producing solar and wind power and transmitting it via high-voltage direct current (HVDC) to the areas in question. In order to store the energy collected at day, molten salt heat storage tanks can be used, which is an ideal complement to the fluctuating energy. With this method, the energy could also be used during the night. In order to heat the power plants, water is needed, which can be acquired by sea water desalination (which produces the molten salt).

There are various possible sources of renewable energy:

• Concentrated solar power (CSP)

CSP plants

Mirrors or lenses capture a large amount of sunlight and concentrate it onto a small area. Solar radiation intensity is then concentrated by several 100 times and very high temperature (more than 1000 °C) is generated. After the concentrated light is converted to heat, it drives a heat engine (e.g. a steam turbine) connected to an electrical power generator, thus electrical power is produced.

An attractive advantage of this technology is that hybridization is possible, meaning that solar fields can be combined with fossil fuel hybrid plants, so the energy supply is continuous.

Parabolic trough-based CSP plant

DESALINATION

The cooling of these plants is a technical challenge, so proper water supply is needed. The sea water is used for this purpose, and by evaporation fresh water is generated from it at the same time. The salt as a byproduct can be further used. Molten salt is a possible tool for thermal energy storage to keep the collected thermal energy. Besides, it can also be used to generate electricity in bad weather or at night.

Apart from this, desalination plants require high temperature fluids and electricity, both of which are easily available in the frames of the Desertec concept. The deployment of these eco-friendly desalination systems is a perfect way to secure fresh water supply.

• Photovoltaics

Photovoltaics (PV) generate electrical power by converting solar radiation into direct current electricity using semiconductors. Solar panels are composed of a number of solar cells containing a photovoltaic material and this type of solar panel also uses silicon, which can be found in the desert.

• Wind energy

Certain parts of the MENA-region have a high wind potential, so the installation of wind farms complements that of solar panels. Wind turbines produce electricity by wind turning the blades, which connects to a generator, which produces electricity.

• High-voltage direct current (HVDC)

High Voltage DC (HVDC) technology is an economical method of power transmission over very long distances. For the Desertec concept it is an extremelyadvantageous method, as for long-distance transmission HVDC suffers lower electrical losses than alternating current (AC) transmission (the electric losses are only about 4-5% per 1,000 km of line).

Further posts on topic: Introduction, What? When?, Where?, Why?, Who?