Investigation of a novel solar photovltaic/micro-channel loop- heat-pipe heat and power system

Yu, Min

Abstract

To tackle the crisis of climate change, increasing the use of renewable energy and enhancing the efficiency of the energy systems are crucial to creating more sustainable and inclusive communities and resilience. This research aims to develop a novel, high efficiency, low cost, and building integrate-able PV/micro-channel loop heat pipe system which can make effective use of solar energy for space heating, hot water and power generation and thus remove certain barriers remaining within the existing Photovoltaic/Thermal (PV/T) technologies. The new PV/T system has a number of unique features (1) a novel loop-heat-pipe (LHP) with micro-channel evaporator and co-axial triple-pipe heat exchanger as the condenser enabling a higher heat transport capacity compared to the latest existing LHP; (2) upper liquid header creating the continuous liquid film on the inner wall of the LHP evaporator which prevents the liquid ‘dry-out’ phenomena occurring; (3) liquid/vapour separator assembled on the liquid header making clear separation of the vapour and liquid which prevents the entrainment effect of the LHP and enhances the heat transfer capacity of the LHP; (4) combination of a micro-channel LHP evaporator with the PV module using a special lamination approach creating a reliable, building integrate-able PV/T panel with a higher overall solar efficiency than existing PV/T panels.
This study investigated the proposed novel solar PV/MCLHP heat and power system through a critical literature review, preliminary design, theoretical analysis using fractal theory, computation modelling, prototype design and construction, indoor (laboratory-controlled) and outdoor (real weather conditions) testing, simulation models validation, and energy saving and socio-economic performance analysis.
For the proposed system, firstly the impact of the fractal geometrical parameters of the wick on the heat transport capacity of the MCLHP was investigated, finding that the capillary limit is the governing limit and the fractal theory is thought to be an ideal method to address the impact of an irregular porous wick on the heat transfer performance of a MC-LHP. A lower inlet water temperature, a higher water flow rate, a higher ambient temperature, and a larger height difference between the condenser and the evaporator can help increase the solar thermal efficiency of the system. Under a range of testing conditions with the refrigerant charge ratio of 30%, a peak solar thermal efficiency (i.e., 71.7%) happened at solar radiation of 561W/m2, inlet water temperature of 18°C, water flow rate of 0.17m3/h, ambient temperature of 30°C, and height difference of 1.3m. This set of parametrical data is therefore regarded as the optimal operational condition of the PV/MCLHP system. Under these specific operational conditions and the real weather solar radiation, the solar thermal efficiency of the system was in the range 25.2% to 62.2%, while the solar electrical efficiency of the PV panel varied from 15.6% to 18.3%. Compared to the existing PV/T and BIPV/T systems, the new PV/MCLHP system achieved 17.2% and 33.3% higher overall solar efficiency. The prototype PV/MCLHP heat and power system would be best suited for the use in a subtropical climatic region, such as Hong Kong. This system has a cost payback period of around 5 years and the life-cycle net cost saving of nearly £3970 in China compared to a conventional gas boiler, while compared to a conventional electric water heater, the cost payback period and the life-cycle net cost saving of this proposed system are 5.6 years and £2220 respectively. Further, the relevant CO2 emissions reduction are 456.7kg and 1751.3kg in Hong Kong.
The research results are expected to configure feasible solutions for future solar PV/T technologies and develop a new solar-driven heating and power system. The main technologies may significantly lead to a wider deployment of the renewable solar systems in buildings and contributing to significant fossil fuel energy saving and carbon emission reduction on the global scale

Citation

Yu, M. (2021). Investigation of a novel solar photovltaic/micro-channel loop- heat-pipe heat and power system. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4251471

• Thesis Type: Thesis
• Deposit Date: Mar 27, 2023
• Publicly Available Date: Jul 10, 2023
• Keywords: Energy & Environment Institute
• Public URL: https://hull-repository.worktribe.com/output/4251471
• Additional Information: Energy and Envrionment Institute, The University of Hull
• Award Date: 2021-01