Abstract
The main research objective of this paper was to compare exergy performance of three different heat pump (HP)-based systems and one natural gas (NG)-based system for the production of heating and cooling energy in a single-house dwelling. The study considered systems based on: 1. A NG and auxiliary cooling unit; 2. Solely HP, 3. HP with additional seasonal heat storage (SHS) and a solar thermal collector (STC); 4. HP with SHS, a STC and a grey water (GW) recovery unit. The assessment of exergy efficiencies for each case was based on the transient systems simulation program TRNSYS, which was used for the simulation of energy use for space heating and cooling of the building, sanitary hot water production, and the thermal response of the seasonal heat storage and solar thermal system. The results show that an enormous waste of exergy is observed by the system based on an NG boiler (with annual overall exergy efficiency of 0.11) in comparison to the most efficient systems, based on HP water–water with a seasonal heat storage and solar thermal collector with the efficiency of 0.47. The same system with an added GW unit exhibits lower water temperatures, resulting in the exergy efficiency of 0.43. The other three systems, based on air–, water–, and ground–water HPs, show significantly lower annual source water temperatures (10.9, 11.0, 11.0, respectively) compared to systems with SHS and SHS + GW, with temperatures of 28.8 and 19.3 K, respectively.
Highlights
The reducing of energy consumption and the lowering of greenhouse gas emissions play an important role in the sustainable development of future society
The results show that an enormous waste of exergy is observed by the system based on an natural gas (NG) boiler in comparison to the most efficient systems, based on heat pump (HP) water–water with a seasonal heat storage and solar thermal collector with the efficiency of 0.47
The first system is based on a NG boiler for heating purposes, while the cooling energy is provided by an additional air–air vapor-compression cooling device
Summary
The reducing of energy consumption and the lowering of greenhouse gas emissions play an important role in the sustainable development of future society. The measures taken so far to achieve the energy and environmental targets by 2030 and 2050 are showing positive results but are not yet ambitious enough or sufficiently effective. Energy consumption for heating and cooling in buildings and industry accounts for almost half of total energy consumption in all sectors [1]. The heating and cooling sector has a huge potential to reduce primary energy consumption and achieve sustainable development objectives. The share of renewable energy sources (RES) for heating and cooling can be increased by using solar heat directly for heating or cooling as “free cooling”, but to a limited extent due to geographical and climatic conditions. Potential fluctuations can be compensated by different types of electrical energy storage, e.g., electrochemical energy storage (batteries)
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