January 24, 2006, Erlangen : The Siemens Industrial Solutions and Services (I&S) Group has received an order from HotRock Erdwärmekraftwerk Germersheim GmbH & Co. Objekt KG, Karlsruhe, to plan and build a turnkey geothermal power plant in Bellheim near Landau in the German state of Rhineland-Palatinate. The geothermal plant will work according to the Kalina principle. This enables heat to be converted into electrical energy with a considerably higher yield than is possible with conventional plants. The scope of supply and services covers the turbine generator set including the turbine, gearbox and generator, the Kalina heat-exchanger circuit, the cooling circuit, the entire electrical equipment and the control system, as well as constructing the control center building, power house and cooling tower basin. The geothermal power station is designed to have an output of 6.4 megawatts.

The small town of Bellheim is situated in the Upper Rhine Graben (rift), and therefore in the "hottest zone" - in geological terms - in Germany. Temperature gradients here can be over 50°C per 1000 meters. The bore hole in Bellheim, extending to a depth of almost 3000 meters, is expected to supply water at a temperature of 165°C. HotRock Erdwärmekraftwerk Germersheim, a company located in nearby Karlsruhe, has planned a project to build a 6.4-megawatt power station here. This corresponds to the power requirements of approximately 25,000 households. A coal-fired power station with the same output would emit some 29,000 metric tons of CO2 per year.

Siemens is responsible for the complete planning and construction of the above-ground components of the power plant. These include the evaporator-condenser circuit, the steam turbine with generator, and the cooling circuit, as well as all the automation and control systems. Siemens had already received orders for the pre-engineering and the production of time-critical components from HotRock during the previous year. The geothermal power plant at Bellheim will operate according to the Kalina principle, using a binary working fluid made up of water and ammonia. Compared with single-component fluids with a constant boiling point such as water or pentane, this mixture boils over a large temperature range at a given pressure. This makes it possible to achieve considerably greater thermal yield than with comparable processes - and hence generate power more efficiently.