Geothermal energy is a renewable form of energy originating in the heat that is naturally present in the deepest layers of the Earth (the average geothermal gradient in the Earth's crust is approximately 3 °C for every 100 metres towards the centre). This energy resource can be exploited by drilling deep wells and conveying the hot fluids (water and/or steam) trapped in the subsoil to the surface. Geothermal plants convert the heat of these "geofluids" into electrical energy, which can be combined with the production of heat for urban heating and various other "direct" uses, such as in greenhouse cultivation or in thermal spas (in these cases, we are talking about cogeneration or coproduction).
Although it accounts for less than 1% of today’s world electricity production, geothermal is the renewable energy source with the greatest potential on Earth, together with solar energy, and it is the only one available 24 hours a day, 7 days a week, all year round, regardless of sun, wind, waves and tides. The exploitation of this resource, which is extensively available particularly at low and medium temperatures (up to approximately 180 °C / 356 °F), is therefore a promising frontier in terms of clean energy and responsible innovation. It is clearly a field in which Turboden intends to promote its versatile ORC technology and know-how.
Advantages of ORC plants in Geothermal Applications
Binary power plants feature many advantages:
- They are the best technical and economical choice, for a wide range of resources / boundary conditions
- They have a definite thermodynamic advantage, in terms of power production, compared to the conventional flashed steam cycles, for resources at moderate temperatures (up to 150-180 °C) and can be used for electricity generation with low-temperature resources (close to 90-100 °C), which would not be feasible with flash steam
- Turbine has no contact with aggressive geothermal fluid, that is confined inside the tubes of the heat exchangers (a wide spectrum of materials can be employed case by case)
- They are environmentally more acceptable than any other kind of geothermal power plant because the geothermal fluid can be segregated throughout the whole process. In this way the release of gases or other substances to the environment can be prevented, thus virtually eliminating pollution problem
- A wide selection of working fluids can be employed in order to optimize the thermodynamics of the ORC with variable geothermal heat resource
- Air cooled condensers can be employed as a further reduction of visual impact and water usage
- They reduce the problems associated with scaling fluids: carbonate scale can be prevented by installing down-well pumps, while silica scale is minimized avoiding concentration of geothermal fluid caused by flashing
After the construction of the first plants in Italy and Africa in the early Nineties, Turboden completed a 1,000 kWel plant in Austria. We have also recently built a 1,500 kWel plant in Soultz-sous-Forets (France)), the first EGS (Engineered Geothermal System) plant in Europe. The water, injected under pressure, reaches deep impermeable rocks fractured by the drilling where it is heated at 180°.
In Q4 2012 Turboden started up the first supercritical ORC plant in Europe, a 500 kW prototype with hybrid direct cooling, and tested its flexibility with highly variable heat input.
Turboden has made plant performance optimization a key point to surpass its competitors and has thus won a tight competition achieving the award of tenders for the design, construction and start-up of 3 geothermal ORC plants in Bavaria (5+ MW each). These plants have been successfully commissioned and started-up in Q1 2013. Geothermal water at 140 °C is pumped from a depth of approximately 4000 metres. These plants are air-cooled and carefully integrated into the rural context and prepared to supply heat to the existing district heating network.
You can find a detailed list of our geothermal units in the References section.
Is it suitable for you?
Geothermal ORC enables the exploitation of low and medium temperature (from 100°C to 200°C) geothermal reservoirs. Since geothermal sources are regular and continuous, the output is completely predictable. Indicatively a power output of at least 500 kWel should be reached to have a cost-effective plant. Target clients include the owners of licences for the exploiting of geothermal reservoirs and all the energy utilities and private investment companies.Back to top