Abstract
This work presents an energy, exergy, and environmental evaluation of a novel compound PV/T (photovoltaic thermal) waste heat driven ejector-heat pump system for simultaneous data center cooling and waste heat recovery for district heating networks. The system uses PV/T waste heat with an evaporative-condenser as a driving force for an ejector while exploiting the generated electric power to operate the heat pump compressor and pumps. The vapor compression system assessed several environmentally friendly strategies. The study compares eleven lower global warming potential (GWP) refrigerants from different ASHRAE safety groups (R450A, R513A, R515A, R515B, R516A, R152a, R444A, R1234ze(E), R1234yf, R290, and R1243zf) with the hydrofluorocarbon (HFC) R134a. The results prove that the system presents a remarkable overall performance enhancement for all investigated refrigerants in both modes. Regarding the energy analysis, the cooling coefficient of performance (COPC) enhancement ranges from 15% to 54% compared with a traditional R134a heat pump. The most pronounced COPC enhancement is caused by R515B (a 54% COPC enhancement and 49% heating COP enhancement), followed by R515A and R1234ze(E). Concerning the exergy analysis, R515B shows the lowest exergy destruction, with the highest exergy efficiency than all investigated refrigerants.
Highlights
The world needs to cut greenhouse gas emissions in half by 2030 and work towards carbon neutrality by 2050 to avoid major disasters (GlobalABC/International Energy Agency (IEA)/UNEP, 2020)
The system using R515B has a cient of performance (COPC) improvement of 54%, followed by R515A and R1234ze(E), with 53% Fig. 7.a, in heating mode, the system using R515B shows a COPH enhancement by 49%, close to R515A and R1234ze(E), with 48%, Fig. 7.b
We proposed a novel simultaneous data center cooling system with waste heat utilisation for a district heating system
Summary
The world needs to cut greenhouse gas emissions in half by 2030 and work towards carbon neutrality by 2050 to avoid major disasters (GlobalABC/IEA/UNEP, 2020). The International Energy Agency (IEA) has proposed a pathway for a sustainable development scenario, focuses on reducing electricity dependence by increasing renewable energy sources usage, enhancing energy efficiency, and recovering waste heat (IEA, World Energy Outlook 2019, IEA, Paris, 2019); (OECD /IEA 2018). In this way, electricity decarbonisation represents around 30% of the emissions re ductions needed (GlobalABC/IEA/UNEP, 2020). Focusing on refrigeration, heating, ventilation, and air-conditioning (RHVAC) systems, the Kigali Amendment to the Montreal protocol star ted the global hydrofluorocarbon (HFC) consumption phase-down in 2019.
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