Evaluation of the environmental sustainability of a micro CHP system fueled by low-temperature geothermal and solar energy

Abstract In this paper we evaluate the environmental sustainability of a small combined heat and power (CHP) plant operating through an Organic Rankine Cycle (ORC). The heat sources of the system are from geothermal energy at low temperature (90–95 °C) and solar energy. The designed system uses a solar field composed only of evacuated, non-concentrating solar collectors, and work is produced by a single turbine of 50 kW. The project addresses an area of Tuscany, but it could be reproduced in areas where geothermal energy is extensively developed. Therefore, the aim is to exploit existing wells that are either unfit for high-enthalpy technology, abandoned or never fully developed. Furthermore, this project aims to aid in downsizing the geothermal technology in order to reduce the environmental impact and better tailor the production system to the local demand of combined electric and thermal energy. The environmental impact assessment was performed through a Life Cycle Analysis and an Exergy Life Cycle Analysis. According to our findings the reservoir is suitable for a long-term exploitation of the designed system, however, the sustainability and the energy return of this latter is edged by the surface of the heat exchanger and the limited running hours due to the solar plant. Therefore, in order to be comparable to other renewable resources or geothermal systems, the system needs to develop existing wells, previously abandoned.

[1]  George Papadakis,et al.  Simulation and economic analysis of a CPV/thermal system coupled with an organic Rankine cycle for increased power generation , 2011 .

[2]  Andreas Schuster,et al.  Energetic and economic investigation of Organic Rankine Cycle applications , 2009 .

[3]  Saffa Riffat,et al.  Development of small-scale and micro-scale biomass-fuelled CHP systems – A literature review , 2009 .

[4]  Sergio Ulgiati,et al.  Emergy evaluations and environmental loading of electricity production systems , 2002 .

[5]  Martin Kaltschmitt,et al.  Life cycle assessment of geothermal binary power plants using enhanced low-temperature reservoirs , 2010 .

[6]  François Maréchal,et al.  Environomic optimal configurations of geothermal energy conversion systems: Application to the future construction of Enhanced Geothermal Systems in Switzerland , 2012 .

[7]  William D'haeseleer,et al.  Comparison of Thermodynamic Cycles for Power Production from Low-Temperature Geothermal Heat Sources , 2013 .

[8]  Mingtian Xu,et al.  Thermodynamic analysis of waste heat power generation system , 2010 .

[9]  M. Beccali,et al.  LCA of a solar heating and cooling system equipped with a small water–ammonia absorption chiller , 2012 .

[10]  Rene Cornelissen,et al.  Thermodynamics and sustainable development , 1997 .

[11]  Farid Chejne,et al.  A technical, economical and market review of organic Rankine cycles for the conversion of low-grade heat for power generation , 2012 .

[12]  Pierluigi Mancarella,et al.  Emission characterization and evaluation of natural gas-fueled cogeneration microturbines and internal combustion engines , 2008 .

[13]  George Tsatsaronis,et al.  Exergy-aided cost minimization , 1997 .

[14]  Philipp Blum,et al.  Review on life cycle environmental effects of geothermal power generation , 2013 .

[15]  Svend Bram,et al.  An LCA based indicator for evaluation of alternative energy routes , 2011 .

[16]  Guo Tao,et al.  Performance comparison and parametric optimization of subcritical Organic Rankine Cycle (ORC) and transcritical power cycle system for low-temperature geothermal power generation , 2011 .

[17]  Minggao Ouyang,et al.  Study of working fluid selection of organic Rankine cycle (ORC) for engine waste heat recovery , 2011 .

[18]  Ennio Macchi,et al.  Technical and economical analysis of a solar–geothermal hybrid plant based on an Organic Rankine Cycle , 2011 .

[19]  Isabelle Blanc,et al.  Environmental analysis of practical design options for enhanced geothermal systems (EGS) through life-cycle assessment , 2013 .

[20]  Ruggero Bertani,et al.  World geothermal power generation in the period 2001–2005 , 2005 .

[21]  Daniele Fiaschi,et al.  Thermodynamic analysis of two micro CHP systems operating with geothermal and solar energy , 2012 .

[22]  Rene Cornelissen,et al.  The value of the exergetic life cycle assessment besides the LCA , 2002 .

[23]  Ruzhu Wang,et al.  COMBINED COOLING, HEATING AND POWER: A REVIEW , 2006 .

[24]  Chiara Galletti,et al.  Modelling and experimental validation of H2S emissions in geothermal power plants , 2002 .

[25]  D. Sánchez,et al.  Alternative ORC bottoming cycles FOR combined cycle power plants , 2009 .

[26]  Martin Pehnt,et al.  Dynamic life cycle assessment (LCA) of renewable energy technologies , 2006 .

[27]  Behdad Moghtaderi,et al.  An in-depth assessment of hybrid solar–geothermal power generation , 2013 .

[28]  François Maréchal,et al.  Defining optimal configurations of geothermal systems using process design and process integration techniques , 2011 .

[29]  Ronald DiPippo,et al.  Second Law assessment of binary plants generating power from low-temperature geothermal fluids , 2004 .

[30]  Hong Guang Zhang,et al.  Performance analysis of a novel system combining a dual loop organic Rankine cycle (ORC) with a gasoline engine , 2012 .

[31]  Paolo Iora,et al.  Bottoming micro-Rankine cycles for micro-gas turbines , 2007 .

[32]  Steven K. Firth,et al.  Life-cycle assessment of a 100% solar fraction thermal supply to a European apartment building using water-based sensible heat storage , 2011 .

[33]  Ruggero Bertani,et al.  Geothermal power generation in the world 2005–2010 update report , 2012 .

[34]  Michael Wang,et al.  Life-cycle analysis results for geothermal systems in comparison to other power systems: Part II. , 2012 .

[35]  Valerio Lo Brano,et al.  Life cycle assessment of a solar thermal collector , 2005 .

[36]  Martin Pehnt,et al.  Environmental impacts of distributed energy systems—The case of micro cogeneration , 2008 .

[37]  Carlo Cardellini,et al.  Carbon dioxide degassing and thermal energy release in the Monte Amiata volcanic-geothermal area (Italy) , 2009 .