RENEWABLE ENERGY
Welding of a cold-formed shell course with two longitudinal welds, wall thickness 180mm
at the same time, storable energy for the decarbonisation of industry has in recent years resulted in exponential growth of this mode of energy generation, however. CSP power plants can be operated cost- effectively only in high-sunlight regions with a high level of direct solar insolation, such as the sunbelt, located close to the
equator, however. Parabolic-trough power plants have been tested for the longest period of time and are also the most widely used type: their trough-shaped mirror collimates the incident sunlight on to an absorber tube at their caustic curve. Here, the concentrated solar radiation is converted to heat which is then yielded to the thermal oil flowing as the working fluid through the absorber tube. Molten salt is used to store the heat. CSP solar towers are surrounded by a large array of mirrors (known as “heliostats”), which automatically track the position of the sun. Tese heliostats reflect the sunlight on to a central receiver located at the top in the tower. Unlike the arrangement in the parabolic-trough system, in a CSP solar tower molten salt flows through the receiver, with the result that salt is, simultaneously, the heat-transfer fluid and the storage medium. Te use of molten salt as a working fluid permits higher temperatures, with the consequence that solar towers have a higher efficiency, and thus a higher cost-effectiveness, than the parabolic-trough plant. In both system types, the molten salt heated up by the concentrated solar energy is routed from the heat-storage tank to a steam-generating system for the production of electricity. Here, superheated steam is produced at high pressure and used to drive steam turbines which, via a generator, produce
electricity in the power- plant unit. Te solar heat not required during daytime is stored using the molten salt in the heat- storage tank and converted to electricity only in the evening or during the night.
A view of the molten-salt test receiver
700MWTH RECEIVER FOR REFERENCE PLANT Te central components of a CSP power plant take the form of the collector system – in other words, the mirrors, as the energy- collecting system – and the receiver (in the case of a tower) or the absorber (in the
case of a parabolic trough) as the energy- conversion system. Te energy-collecting system charges the storage unit, while it discharges the energy-conversion system either simultaneously or after a delay. Also necessary are thermal oil or molten salt, as the working fluid, molten salt as the heat-storage fluid, a hot-salt tank, a cold-salt tank, salt pumps and the steam generators and steam turbines required as further components of the energy- conversion system. A project consortium consisting of German industrial companies – including MAN Energy Solutions – and the DLR has developed in a case study a CSP reference power plant of the current maximum technologically conceivable size. Tis maximum size is determined by the quantity of radiated heat which actually reaches a receiver of a diameter of 20m from mirrors located at a distance of 1km. Te reference power plant takes the form of a 250m high solar tower with a 700MWth receiver, a heat-storage tank and a cold- storage tank each filled with 53,000 tonnes of molten salt, and a 200MWe power-plant unit. Te molten-salt receiver designed for this purpose by MAN Energy Solutions is equivalent in its conception to a prototype already tested at Jülich. Te reference plant with its 700MWth receiver permits full- load operation for 12 hours from sundown to sunrise. Two 200MWe power-plant units are planned for a “peaker” variant, i.e. for demand-orientated use at times of peak loads.
Heavy plates showing fully automatically milled edges
8,600t bending machine for shaping shell courses for Fischer-Tropsch reactor
JÜLICH PROTOTYPE HAS HIGHER SALT TEMPERATURES MAN Energy Solutions has developed a molten-salt receiver suitable for
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