Liquid-based Photovoltaic/Thermal Cogeneration for Real Building Application

Hong Kong, a modern sub-tropical city, has a great potential of applying solar energy in hot water and electricity co-generation. Most buildings here are provided with conventional gas/electrical water heaters for services hot-water supply. According to the energy end-use data (1996-2006) published by the Hong Kong Government, direct hot water production consumes about 4% of the total energy use in the city, and 20% when considering only the domestic sector. Energy wastage has raised the environmental concerns of the general public, no less than the deteriorating air pollution, urban heat island effect, greenhouse gas emission and health risk issues. Since 2005, the Hong Kong Government has been targeting at 2012, with 1-2% of the territory-wide energy use from renewable energy sources.On the other hand, direct electricity generation from photovoltaic (PV) is more expensive than conventional power generation. The situation is expected to remain for some years. Without government subsidies, the PV initiative of the commercial sector relies heavily on the social responsibility and/or the intangible income sources of the properties developers. By integrating PV modules with solar water heating collectors, the increased energy yield per unit collector area is able to shorten the economical payback period to less than 1/4 of the plain PV application. Such photovoltaic/water-heating (PVW) cogeneration is found to be much promising than the separate side-by-side installations of PV modules and solar thermal collectors from energy conversion, space utilization, and aesthetic points of view.An escalating number of research activities on PVW has been reported in the last few years. But so far the literatures were reporting the numerical or experimental findings, with inadequate coverage on real plant operation and system reliability. The international research community has placed real project demonstration with longer-term monitoring as a current strategic need of the technology. With the previous research funding, the research team analyzed the PV/Thermal opportunities in their region and introduced an innovative PVW product with good marketing potential. In meeting the current needs, the objectives of this project are thus:To implement a PVW system for real building application at City University of HK campus;To analyze the field measured data from energy saving, sustainability, reliability and finance aspect, as compared to the conventional or alternative design options in Hong Kong;To generate a full report on the practical difficulties and optimization opportunities in relation to its real building application in subtropical climate.