Abstract
The energy-saving potential of heat pump technology is widely recognized in the building sector. In retrofit applications, especially in old and historic buildings, it may be difficult to replace the existing distribution and high-temperature emission systems. Often, historical buildings, especially the listed ones, cannot be thermally insulated; this leads to high temperatures of the heat carrier fluid for heating. In these cases, the main limits are related, on the one hand, to the reaching of the required temperatures, and on the other hand, to the obtaining of good performance even at high temperatures. To address these problems, a suitable solution can be a two-stage heat pump. In this work, a novel concept of a two-stage heat pump is proposed, based on a transcritical cycle that uses the natural fluid R744 (carbon dioxide) with an ejector system. The second refrigerant present in the heat pump and used for the high-temperature stage is the R1234ze, which is an HFO (hydrofluoro-olefin) fluid. This work aims to present the effective energy performance based on real data obtained in operating conditions in a monitoring campaign. The heat pump prototype used in this application is part of the H2020 Cheap-GSHP project, which was concluded in 2019.
Highlights
The European Union (EU) set ambitious targets to fight the issue of climate change, to guarantee the security of supply and increase competitiveness in the energy sector
The configuration and monitored data for a novel cascade ground-source heat pumps (GSHP) developed within the H2020 Cheap-GSHP project, concluded in 2019, are presented
The heat pump, installed at the Technical Museum Nikola Tesla in Zagreb, uses CO2 and R1234ze as the working fluids in a transcritical cycle where the common expansion valve is replaced by the ejector technology and in the high-temperature cycle, respectively
Summary
The European Union (EU) set ambitious targets to fight the issue of climate change, to guarantee the security of supply and increase competitiveness in the energy sector. The building sector, responsible for about 40% of total EU energy consumption, is a great contributor to greenhouse gas (GHG) emissions [1]. When considering the household sector, the share of the European final energy consumption is around 26%, with about 80% due to heating, cooling, and domestic hot water production [2]. An important step to meet the goals of reducing GHG emissions and increasing the renewable energy sources (RES) share can be obtained by adopting technologies that do not employ fossil fuels for the heating and cooling of buildings.
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