CLP project GmbH
Hauptmenü:
"Renewable energies already cover a significant amount of our energy demand. Due to weather conditions and seasonal changes, we are however far from a real planning reliability. The energy storage option and thus the programmability of the power production gives us the possibility to secure our energy supply in the long term without conventional power plants. "
Technologies
For several years now, we have strengthened our focus on the concentrating solar power sector.
Solar thermal systems also known as CSP plants (Concentrating Solar Power) absorb the direct radiation from the sun by reflecting its rays with special mirrors onto a receiver and generate thereby high temperature heat. The thermal energy collected this way can be converted into electrical energy by means of a thermodynamic conversion (eg. with a steam turbine).
There are a variety of different technologies to generate electricity from the heat of the sun's rays. The most important are the parabolic trough collectors, currently the most popular, and the solar tower system.
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The CSP technology absorbs the solar radiation through the use of reflective surfaces (parabolic mirrors) which follow the movement of the sun and concentrate the sun’s rays onto a receiver tube, which is located in the focal line of the parabolic mirror.
In this way, the heat transfer fluid (HTF), flowing on the inside of the receiver tubes is being heated up by the solar radiation. Depending on the temperatures that have to be reached, there are a variety of different HTFs:
- pressurized water for temperatures just above 100° C
- diathermic oils for temperatures up to 400° C
- mixture of molten salts (sodium and potassium) for temperatures until 550° C
A special feature of this technology, unlike other renewable energy methods, is the possibility to store the heated molten salts in insulated stainless steel tanks and the possibility of a programmable power supply. In other words, this technology is capable of adjusting the energy production to the consumers’ needs.
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Solar power plants with tower system
Solar power plants with the tower system consist essentially of a heliostat field, a tower with a solar receiver on its top as well as a thermodynamic process to generate electricity. The heliostat field is made of a variety of slightly curved mirrors that track the sun and reflect its rays onto the receiver.
Using the heat of the absorbed solar radiation a heat transfer fluid, located in the receiver, is heated up and its thermal energy is used in the following thermodynamic process to generate electricity.
In contrast to the parabolic trough technology with molten salts, an essential feature of the tower plants are the higher operating temperatures (from 600°C to over 1000°C) which can be reached by the strong concentration of the solar radiation onto the receiver, enabling thereby higher efficiencies in the downstream cycle, thus reducing electricity production costs.
These systems are also able to store the heat and generate electricity when most needed.
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Our projects
San Quirico (OR) - Sardinia
10,8 MW Solar power plant with parabolic trough collectors
San Quirico will be the first commercially operated plant of its kind
This plant is substantially different from the previously constructed thermodynamic power plants worldwide in the following points:
- In this plant a mixture of molten salts (60% NaNO3 and 40% KNO3) is used as thermal vector instead of diathermic oils. This vector, consisting of sodium and potassium nitrate, is stored in large tanks and can be used to operate the plant during the night and during bad weather periods. Another advantage of this vector is the ability to maintain the required temperature for a long time.
- A biomass plant with wood chips (approximately 10.5 MWth) functions as an additional back-up system providing the additionally required thermal energy during longer periods of bad weather and at night. Thus, a continuous supply of electricity for 20 hours per day can be guaranteed worldwide, even in latitudes with low direct normal irradiation "DNI".
- The biggest advantage of this system is the programmability of the power supply. The electricity can be delivered day and night, thus covering the peak of consumption, even in case of bad weather conditions during which wind power and photovoltaic systems can’t supply energy.
- Another great advantage is the achievement of the operating temperature. Molten salts are able to reach a temperature of 530°C whereas thermodynamic oils can only reach a maximum of 390°C. This increases significantly the performance of the turbine and thus its effectiveness.
- Molten salts aren’t considered pollutive or explosive, whereas diathermic oils are considered highly toxic and pose a high risk of explosion at temperatures over 390°C.
