Thermodynamic cycles in geothermal energy

How geothermal heat is transformed in order to be used in turbines producing electricity? Thanks to “thermodynamic cycles”. They are the set of various thermodynamic processes, which are based on the “law of conservation of energy”. It tells us that energy is isolated system and its amount remains constant; energy cannot be created or destroyed, just turned from one type into another. In other words, geothermal heat, thanks to thermodynamic cycles, can be turned into other types of energy used in steam turbines. Have a brief look on it:

Thermodynamic cycle is about turning heat into work (we mean physical term of „work“) under concrete pressure, temperature and other physical factors. In ideal case, transforming heat into work as well as work into heat, can be described like zero sum game. So, if there would not had been any losses (it means ideal case), the whole amount of energy in form of geothermal heat would have been transformed into the same amount of work and later on electricity. In reality, effectiveness varies regarding the concrete type of used thermodynamic cycle.

On field of geothermal energy, there are used several types of thermodynamic cycles - e.g. Kalina cycle, Organic Rankine Cycle (ORC) and other - or their combinations. The use of concrete type of cycle depends on quality of reservoir, the pressure, water temperature and many other factors. As we mentioned above, every transformation of one type of energy into another is accompanied with losses. In this regard, optimization of geothermal energy production process is necessary in order to minimize those losses.

Optimization means the most appropriate combination of thermodynamic cycles and the most appropriate setting of other physical parameters. If you are interested in the most used thermodynamic cycles in geothermal energy, next articles on this blog will be dedicated to this topic. We will also bring concrete case studies – description of some geothermal wells and facilities in Europe.