IGSHPA Technical/Research Conference and Expo Denver March 14-16, 2017 Properties of different ethyl alcohol based secondary fluids used for GSHP in Europe and USA Monika Ignatowicz, Åke Melinder, Björn Palm ABSTRACT The extensive use of ground source heat pumps (GSHP) for heating and cooling purposes has made Sweden the European leader in geothermal energy utilization, in terms of the installed capacity, as well as extracted thermal energy. The commercially available ethyl alcohol based fluids in Sweden are distributed as 88 - 95 wt-% ethyl alcohol concentrate, including up to 12 wt-% of denaturing agents in form of propyl alcohol (8 to 10 wt-%) and n- butyl alcohol (2 wt-%). In Switzerland the commercial ethyl alcohol products contain 2 vol-% methyl ethyl ketone and 0.5 vol-% methyl isobutyl ketone, whereas in Finland commercial products contain up to 1.8 vol-% methyl ethyl ketone and 2.7 vol-% methyl isobutyl ketone. In North America the most common denaturing agents for ethyl alcohol based secondary fluid are methyl alcohol (methanol) (3.76 - 10 wt-%) and pine needle oil (up to 0.5 vol-%). The chemical character of these denaturing agents can in different ways affect the thermophysical properties. Thus, the aim of this paper was to investigate the thermophysical properties of different commercially available alcohol blends in Europe and United States. The results showed that the commercial product commonly used in Sweden (EA18 + PA1.6 + BA0.4) has the best thermophysical properties among different ethyl alcohol based products found in Europe when taking into consideration all thermophysical properties. Pure MA20 poses better thermophysical properties than EA18+MA2 and the lowest viscosity among all investigated alcohol blends. MA20 has as well good properties but special care needs to be taken due to high toxicity of methyl alcohol. Moreover, EA18+MA2 does not have good thermophysical properties compared to other ethyl alcohol blends and products containing small amounts of propyl and butyl alcohol or ketones are more recommended instead. INTRODUCTION Atnics et al., 2016 has reported that the total number of ground source heat pump (GSHP) installed in Europe exceeds 1.7 million units. Sweden among other European countries is the leader in geothermal energy utilization in terms of the installed capacity and extracted thermal energy (Gehlin et al., 2016). It is estimated that there are about 500 000 small and 500 large ground source heat pumps (Acuña et al., 2015). According to the statistics there are around two million single-family houses in Sweden and around 20 - 25 % of these houses are heated by GSHPs. The dominant type of GSHP systems are shallow low temperature systems ranging from 5 to 10 kW that provide about 23 TWh of heating and cooling. The total installed heating and cooling capacity in Sweden is estimated to be 6.8 GW. The typical Swedish setup consists of one or several vertical borehole heat exchangers (BHE) having a depth between 120 and 300 m (Gehlin et al., 2016). In many countries the space around the U-pipe in the borehole is filled with grout to prevent water and contaminants migration along the vertical borehole (Gustafsson et al., 2010). Swedish guidelines allow for ungrouted, groundwater filled BHE. Moreover, the market for larger shallow GSHP systems for both residential and non-residential buildings has been expanding over the last years (Gehlin et al., 2016). Ethyl alcohol based secondary fluid is one of the most common secondary fluids in Sweden for GSHP application recommended by the Geological Survey of Sweden (SGU) and the Swedish Environmental Protection Agency due to Monika Ignatowicz (monika.ignatowicz@energy.kth.se) is a PhD student, Åke Melinder (ake.melinder@energy.kth.se) is a doctor and Björn Palm (bjorn.palm@energy.kth.se) is a professor at the Department of Energy Technology, KTH Royal Institute of Technology, Stockholm, Sweden.