Research & innovation

Ολοκληρωμένη Έρευνα και Ανάπτυξη Συστημάτων Γεωθερμικών Αντλιών Θερμότητας θαλασσινού νερού σε κτιριακές εγκαταστάσεις

Integrated research and DevELopment of GeotheRmal seawater heAt puMps systems in building sector

The IDEOGRAM proposal concerns the investigation, analysis and evaluation of the possibilities of exploitation of shallow (normal) geothermal energy and specifically of open circuit Geothermal Heat Pumps (GHPs) with energy source seawater or shallow coastal aquifers. It concerns technological and applied research aimed at acquiring new knowledge and skills in investigation, analysis, evaluation, as well as in the design and implementation of innovative heating and air conditioning facilities for building facilities of different uses, referring to real applications. At the same time, the possibility of reducing the cost of the installations will be explored with the appropriate selection of innovative materials and machines or through the search for synergies, as well as through best installation practices.

It should be noted that there are three categories of utilization of Geothermal Energy: a) Geothermal Power Generation, b) The direct uses of geothermal energy which include spa therapy, agricultural applications, district heating, etc. and c) Geothermal Heat Pumps (GHPs), i.e. the utilization of the shallow geothermal (T<30°C) for heating/cooling-cooling. In addition, it is stated that the use of sea water in GHPs is indicated for medium and large-scale installations in cases where hydro wells have increased construction costs (rocky, sandy soils) or there is insufficient supply of fresh water for their operation (e.g. coastal, island areas), thus eliminating geological risk, i.e. the short-term risk of not finding an economically viable geothermal resource after drilling, as well as the long-term risk of natural depletion of the geothermal resource, making exploitation economically unprofitable.

GHPs are among the Renewable Energy Sources (RES) technologies and their use is accompanied by a great potential for saving energy and reducing greenhouse gas emissions. The energy savings that can be achieved by replacing conventional heating systems (using oil) with GHPs is up to 70%, while by replacing conventional cooling systems (air-cooled systems) it is up to 40%. The important advantage of the GHPs that use sea water is found in the use of the constant temperature property of sea water in the coastal areas of the Mediterranean, where the water temperature ranges from 16 - 22 °C. These facilities draw water from an underground or surface reservoir using boreholes or pipelines and usually an intermediate water/water heat exchanger interposed between the GHPs and the open circuit and impart or absorb energy to the system before the water returns to the reservoir.

The stability of the temperature of the sea water and its maintenance at the levels of the average annual value of the ambient air temperature contribute to the operation of the GHPs at high levels of efficiency. In cooling plants seawater acts as a cooling medium and replaces the water from the cooling towers, which in turn are replaced by a production well or pipeline and a seawater reintroduction well or pipeline.

The technology of exploiting the heat of sea water through GHPs is one of the innovative and promising technologies that can contribute to energy savings in the heating and air conditioning sectors, helping to achieve the goals of the Green Deal for a fair and prosperous society, based on a modern, efficient and competitive economy, which has as its main goal the emergence of Europe as the first climate-neutral continent.

The technology of exploiting the heat of sea water through GHPs is one of the innovative and promising technologies that can contribute to energy savings in the heating and air conditioning sectors, helping to achieve the goals of the Green Deal for a fair and prosperous society, based on a modern, efficient and competitive economy, which has as its main goal the emergence of Europe as the first climate-neutral continent.

The market of GHPs (closed and open circuit) in Greece started in the early 2000s showing a significant increase after the middle of it. Despite the economic crisis of the last decade, the growth of the GHPs sector remained positive. According to the published statistics (Ministry of Energy and Environment and CRES), the total installed capacity of GHPs facilities in 2017 was 148 MWth. It is very difficult to find the exact number of installed shallow geothermal systems, especially those in individual residences. However, it can be reasonably estimated that over 3300 GHPs units were operating in the country at the end of 2018, with a total installed capacity of 175 MWth.

The IDEOGRAM proposal concerns the research and development of a methodology for the study and application of seawater GHPs systems (including reservoirs such as lake and river) in different building installations to cover heating and air conditioning needs

The significant increase in the number of GHPs systems is due to several factors: the change of people's attitude towards "new" technology, the increased interest in heating and air conditioning in buildings, the rapid increase in oil prices and the simplification of licensing procedures for drilling. However, the consolidation of this technology and the increase of the share of these systems in the heating and air conditioning market of the building sector, directly depends on the successful operation of the existing applications and the reduction of the initial investment costs, especially after the financial crisis of recent years. It is obvious that the in-depth knowledge resulting from applied research, the existence of reliable design and/or optimization tools is a critical parameter for the implementation of not only efficient, but properly dimensioned, therefore economically competitive, seawater GHPs systems.

KRITON Energy collaborates with the Mechanical Design Laboratory of the Production & Management Engineering Department of the Demokriteon University of Thrace