Modular Low Temperature Cycle Karlsruhe (MoNiKa)
The Institute of Thermal Energy Technology and Safety (ITES) install at the site of the Karlsruhe Institute of Technology Campus North (KIT-CN), a generic power plant circuit of a geothermal power plant. This cycle is modular, mobile and offers unique opportunities for the study of geothermal power generation and low-temperature electricity generation. The individual main components (pump, heat exchanger, turbine, etc.) are interchangeable and will be characterized in wide operating ranges. The interactions of the components with each other under consideration of site-specific boundary conditions are also part of the research work. In this way, the thermodynamically and economically optimization of both, the individual components and the cycle as a whole is one aim of the further work. The results of the research carried out on MoNiKa contribute to increasing the efficiency of power generation from low-enthalpy geothermal sources.
In addition to the optimization and characterization of the components, the generic ORC could also be used to investigate different working fluids and mixtures. A favored option is supercritical propane. Power plants with supercritical live steam parameters shows significantly higher efficiencies than comparable subcritical power plants. One reason for this is the lower exergy losses during the preheating and evaporation of the working fluid in the heat exchanger.
In order to carry out site independent investigations, the power plant circle is not connected to a thermal water circuit. Rather, a hot water boiler heat up the synthetic thermal water and fed it to the power plant. In this way, temperature and mass flow can be varied within wide limits. In addition, disruption of the investigations due to corrosion, scaling or site-specific water compositions can be eliminated.
The plant is planned and constructed in such a way that a change of location is possible with reasonable effort. Due to this mobility, site-specific investigations can be carried out at any time with the Monika facility.
At IKET simulation calculations with different codes for power plant simulation are used. Here, the operating parameters are varied and compared with each other for different working fluids. For verification of the simulation calculations, however, a direct comparison with a real power plant circle is required. This is not possible due to the lack of instrumentation at the existing systems. Therefore, no systematic variations in the power and temperature range are possible here. In addition to integral performance data, detailed local data are necessary for a reliable comparison with simulations in order to reliably understand the influences and interactions of the components correctly in the simulation.
The main source of income for the geothermal plant operators is the heat supply, in addition to power generation. Therefore is inevitably a coupling of heat and electricity production. This in turn requires the partial load operation of the power plant part. For this purpose, the behavior and cost-effectiveness of the components must be sufficiently well known in part-load and full-load operation as well as during load changes. These investigations are only possible to a very limited extent on commercially operating power plants.