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GROUND-MED (Advanced ground source heat pump systems for heating and cooling in a Mediterranean climate) is a project financed under the European Union’s Seventh Framework Programme (FP7) that aims to verify the sustainability of heat pump technology for heating and cooling of buildings in a Mediterranean climate and to demonstrate the next generation of geothermal heat pump (GSHP) systems for heating and cooling.
The six-year project, which started in 2009 with a budget of approximately EUR 7.25 million, was implemented by a consortium of 24 organisations from EU Member States at 8 demonstration sites in Southern Europeyear 1. The consortium includes a wide diversity of GSHP actors, such as research and educational institutes, heat pump manufacturers, and national and European industrial associations.
The scope of the GROUND-MED project was to develop, demonstrate and monitor advanced ground source heat pump (GSHP) systems with a seasonal performance factor (SPF) 2 higher than 5.0 (the average for GSHP currently installed in the EU is 3.5). The project, which was completed on 31 December 2014, comprised 25% research and 75% demonstration and dissemination activities and examined GSHP as an integrated system comprising a borehole heat exchanger (BHE) field, a water/water heat pump and an indoor heating/cooling system, with the objective of maximising the energy efficiency of the overall system.
While previous projects focused on improving the coefficient of performance (COP), with the GROUND-MED project the focus of technological development was on the SPF of the heat pump, which means that the capacity control of the heat pump played an important role. Different options were considered, including inverter-controlled compressors and tandem compressors. An additional gain in SPF was achieved by maintaining the heat exchangers in counter flow operation during both heating and cooling modes.
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Other system components were also considered, with a view to developing advanced fan-coil units with power consumption reduced by a factor of 4, improved air handling units with low primary energy use, as well as advanced heat storage nodules, which allow intraday storage of heat and cold at optimum temperatures for maximum energy efficiency. Further energy efficiency improvements were achieved by selecting water circulating pumps from among the energy class-A brands available from European manufacturers.
Special attention was also paid to the GSHP control system, with a view to regulating the temperature of both the BHE field and the water supply to the indoor system. This was done in order to force the system to operate with the lowest possible temperature difference (ΔT) across the heat pump, resulting in the maximum possible SPF. This was achieved by adjusting the water temperature proportionally to the heating or cooling load. In terms of heat pump efficiency, this operating temperature adjustment results in the COP improving from 4.5 to 5.9, which is equivalent to an SPF increase from 4.5 to 5.75. This, in turn, results in 20% less electricity consumption by the heat pump.
Last but not least, as the project targets regions with a Mediterranean climate, cooling is of extreme importance. This poses additional challenges for BHE design and sizing and sets high standards for the heat pump efficiency. While poorly designed GSHP systems can still operate fairly well in heating mode, albeit at the expense of energy efficiency, only the best heat pumps in terms of COP coupled to state-of-the-art BHEs can provide reliable and cost effective operation in cooling mode.
The GSHP technology developed within the framework of the project was applied in buildings at the eight demonstration sites, where advanced GSHP systems for heating and cooling were constructed. For technology evaluation purposes, four different SPF values were calculated considering electricity consumption at: the compressor; the compressor and external circulation pump; the compressor and both external and internal circulation pumps; and the compressor, all pumps, fan-coils and air handling units.
Technology tested as part of the GROUND-MED project includes new prototypes which have been integrated into the eight GSHP systems demonstrated and monitored at the sites. These include three heat pump prototypes from the Austrian manufacturer OCHSNER WP, which are advanced in terms their energy efficiency. The project also demonstrated two advanced heat pump prototypes from the Italian manufacturer HIREF, one with tandem compressors and another with an inverter compressor. The improved performance of these various prototypes resulted in energy savings of 35%.
Also demonstrated, and also producing energy savings of 35%, were three advanced heat pump prototypes from the French manufacturer CIAT with Eurovent class-A energy efficiency levels. Their main features of these pumps are their tandem compressors and water reversibility via four three-way valves. CIAT also provided an improved cold storage system, optimised for better efficiency, in addition to new advanced fan-coil unit prototypes. The latter are characterized by their low-temperature operation and by their extremely low electricity consumption (80% electricity savings).
The effective demonstration of these technologies was the first step towards their large scale market penetration. Successful implementation of the GROUND-MED project will result in increased support for these renewable energy technologies through EU and national funding programs, allowing them to effectively contribute to the EU’s 20/20/20 targets. The economic benefits of this research and demonstration work will be felt in the long term, when the technology and solutions developed through the project are replicated throughout the EU and international heating and cooling markets.
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1 Septèmes -les-Vallons, France; Oradea, Romania; Coimbra, Portugal; Benedikt, Slovenia; Valencia and Barcelona, Spain; Padova, Italy; and Athens, Greece.
2 This is defined as the ratio of useful energy delivered by a heat pump to the electricity consumed over a season.