| Title | Geothermal ORC plant case study in Italy: Castelnuovo Pilot Project – Design and technical features |
|---|---|
| Authors | Vaccaro, M; Batini, F; Stolzuoli, M; Bianchi, S; Pizzoli, R; Lisi, S |
| Year | 2016 |
| Conference | European Geothermal Congress |
| Keywords | Geothermal ORC plant, Castelnuovo Val di Cecina, Pilot plant, Landscape integration, NCG, reinjection, High enthaphy geothermal reservoir |
| Abstract | The case study illustrated in this paper is a geothermal ORC power plant, currently designed to be installed in Castelnuovo Val di Cecina (province of Pisa, Italy). The project will be executed by Magma Energy Italia. The power plant will install a turboexpander manufactured by GE Oil&Gas Nuovo Pignone, Florence (Italy). The solution has been studied to create an innovative “closed loop” power plant, achieved by integrating a binary cycle power plant with a suitable plant infrastructure, respecting the principle of a safe, clean and environmentally integrated system. This goal is achievable through the combined implementation of the points listed here: Closed loop; Use of non-toxic and non-flammable substances; Total reinjection of fluids and non-condensable gases in the same geological formations from which they are extracted; Adopting an ORC working fluid cooling methodology (air cooler condenser) with no water consumption; Placing the power plant near the production wells and creating the reinjection well on the same drilling pad, avoiding the construction of new pipelines needed to transport fluids to a different site. This particular ORC application is an innovative case study. The working fluid is R245fa, which is not flammable, and it has a null ODP (Ozone Depletion Potential). The plant is fed by geothermal steam at about 14 bar. Usually in the majority of the geothermal ORC plants, the primary energy source is a liquid (geothermal hot brine, pressurized water). Having a steam condensation in the main heat exchanger is an innovative aspect that characterizes this geothermal project. The main heat exchanger is a geothermal steam condenser, which is used to evaporate and superheat the R245fa. Heat transfer occurs with presence of Non-Condensable Gases (NCG), this adds an additional element of novelty to the project. In order to maximize the sustainability of this project, total reinjection is performed. Both geothermal condensate and Non-Condensable Gases (NCG) are reinjected through a well. In the paper the optimization of the cycle parameters is treated. The geothermal condensate water, after the heat transfer to the working fluid, is also available for direct use too, being delivered to the return gathering system at about 90 °C. NCG are collected and pressurised in order to be re-injected. A particular aspect of this case study is the landscape and environmental integration with the surroundings. The paper describes the devices and precautions elaborated in order to minimize the visual impact and harmonize the plant penetration in the surrounding environment. A sustainability analysis and description of the plant is also performed in the paper. |