Innovative concentrated solar micro organic Rankine cycle plant system for residential buildings

Abstract

Reducing the energy consumption in the building sector, as well as its associated CO2 emissions, is one of the main environmental concerns at worldwide level. In developed countries, the building sector means 41% of the total energy consumption and 40% of the total greenhouse gases emissions. To improve the energy efficiency of residential buildings, several energy strategies were carried out in European countries to encourage the development of active energy saving systems; such as the solar thermal energy. The presented study is in the frame of the Innova MicroSolar European project, which is sponsored by the European Union’s Horizon 2020 research and innovation programme. The main goal of this project is to develop an innovative concentrated solar heat and power system for residential buildings, which supplies 2-kWelec and 18-kWth. This technology includes a concentrated solar system, a high performance micro organic Rankine cycle (ORC) turbine, and an enhanced latent heat thermal energy storage (LHTES). The solar system is based on linear Fresnel mirrors which are considerably easier and cheaper to manufacture than their parabolic equals. Also, the mirrors are led by a sun tracking mechanism so they are always focusing the absorber tubes, heating up to 295ºC the heat transfer fluid (HTF) flow. The total area of the real scale prototype solar field is 140 square metres, which could provide from 80 to 15 kWth. The micro ORC technology is equipped with a high speed permanent magnet AC alternator able to supply 2.3 kWel. The ORC block has to be fed with 22 kWth. Finally, the TES tank consists of two main blocks, the PCM tank and the enhanced heat sink. Both blocks are connected between them by reversible heat pipes as heat carrier. The storage is designed to supply 25 kWth during four working hours. The whole system will supply 60% of the total building energy demand, reducing the energy cost up to 20%, as well as the greenhouse gases emissions when comparing against the best renewable energy technologies available on the market. This study shows the first experiments of the whole systems. The HTF (Therminol 62) is heated up to 270ºC with the solar field, then the HTF is lead to the ORC evaporator and the organic fluid (cyclopenthane) evaporates and runs the turbine. The TES tank is charged when the solar field reaches maximum power levels. Once the solar production cannot run the ORC, the solar field is bypassed and the TES tank successfully becomes the main energy supplier.

The research leading to these results has received funding from the European Union´s Horizon 2020 Research & Innovation Programme under Grant Agreement 723596 with reference name Innova MicroSolar. This work was partially funded by Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER)). José Miguel Maldonado would like to thank the Spanish Government for his research fellowship (BES-2016-076554). Alvaro de Gracia has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 712949 (TECNIOspring PLUS) and from the Agency for Business Competitiveness of the Government of Catalonia. The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREiA (2017 SGR 1537). GREiA is a certified agent TECNIO in the category of technology developers from the Government of Catalonia.