Solar contribution to building energy saving

Abstract

Fossil fuels, the main energy resource in many countries, are being gradually depleted. The burning of fossil fuels is the largest source of carbon dioxide, which is one of the greenhouse gases causing global warming and climate change. The danger to the global environmental posed by the burning of fossil fuels has led to the search for renewable and sustainable sources of energy. Direct solar radiation is considered to be one of the best prospective sources of sustainable energy. The objectives of this research are to identify the operational performance and electricity benefits of the widely used building-integrated photovoltaic system; to predict the photovoltaic energy generation; and to analyse and predict the daylighting and energy performance in atrium spaces. To achieve these objectives, a series of studies that measured the contributions of solar power to building energy savings were conducted in an institutional building with a building-integrated photovoltaic (BIPV) system used to generate electricity and an atrium designed for daylight harvesting. In the first study, which examined the operational performance and electricity benefits of the BIPV system, the financial, energy and environmental issues were evaluated in terms of, respectively, monetary, energy and greenhousegas payback periods. As the system's technical information collected under standard test conditions may never occur in practice, field measurement is the most accurate method of obtaining reliable data and determining the performance of various designs under actual operating environments. The payback periods calculated on the basis of this study's results suggested that grid-connected BIPV systems are promising renewable energy applications. The second study used the intelligent approach to generate a real-time prediction and a short-term forecast of the energy generated by the photovoltaic (PV) system. It was possible to predict the energy generated by the PV system using only the dry-bulb temperature, solar elevation angle, solar azimuth angle and solar radiation. The confidence intervals under different predictions overlapped with each other, suggesting that one single set of designated input parameters could predict real-time and up-to-20-minute lapse outputs within 95% confidence intervals. Facility managers could use this result to help them with management, scheduling and dispatching operations in power systems. The third study analysed and predicted the daylighting and energy performance in atrium spaces that used daylight-linked lighting controls. It estimated the cost, energy and environmental savings related to various daylight illuminances. The results support the assertion that installing daylight-linked lighting controls in day-lit corridors could produce remarkable energy savings. These field measurement findings could provide much-needed information for building professionals, building owners and building operators who are striving to develop their energy conservation strategies and management schemes. Finally, an extended empirical study of lighting-energy consumption on the lower atrium floors was conducted. The results showed that the energy generated by the PV system is enough to provide lighting energy for the whole atrium, thereby achieving a self-sustained lighting energy atrium. This evaluation shows how, with a relatively small area of solar modules, the self-sustained lighting energy atrium concept, even for deep atrium, is feasible. This series of empirical studies demonstrate the contribution of solar power to building-energy savings through a combination of electricity generation and atrium designs that focused on daylight harvesting. The results confidently demonstrate that solar energy, the most abundant and easily harnessed energy resource, can alleviate the over-dependence on fossil fuel use and mitigate greenhouse gas emissions. A summary of the key findings, the research limitations and our recommendations for future research conclude the thesis.

Date of Award	2 Oct 2013
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Wai Ming LEE (Supervisor)