تجزیه و تحلیل انرژی و هزینه فتوولتائیک نیمه شفاف در ساختمان های اداری

Solar energy conversion systems and daylighting schemes are important building energy strategies to produce clean energy, reduce the peak electrical and cooling demands and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a building component generating electricity via PV modules and allowing daylight entering into the interior spaces to facilitate daylighting designs. This paper studies the thermal and visual properties, energy performance and financial issue of such solar facades. Data measurements including solar irradiance, daylight illuminance and output power for a semi-transparent PV panel were undertaken. Using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. Case studies based on a generic reference office building were conducted to elaborate the energy and cooling requirements, and the cost implications when the PV facades together with the daylight-linked lighting controls were being used. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.

Hong Kong has no indigenous fuels and most of the imported energy products are fossil fuels which are mainly for electricity generation [1] and [2]. There are many immediate adverse effects to the environment such as greenhouse gases and pollutants emissions from the burning of fossil fuels [3]. Electricity conservations mean fossil fuel saved together with the likely pollutants and greenhouse gases reductions [4]. Renewable energy can play an important role in meeting the ultimate goal of replacing certain amount of fossil fuels. Recently, solar energy has been identified as an appropriate technology for wide-scale use in Hong Kong [5]. One of the promising applications of solar-based conversion systems is the installation of photovoltaic (PV) facilities that generate power without emitting pollutants and requiring no fuel. However, PV applications are not popular in local building developments. The barriers are mainly the high initial costs, the large installation spaces required and the low output power produced. In Hong Kong, most electricity is expended by building stocks and the commercial sectors account for 65% of the energy consumption [6]. The electricity used in commercial buildings is largely for creating a thermally and visually comfortable built-environment through air-conditioning and artificial lighting. Previous research work revealed that air-conditioning and electric lighting represent over two-thirds of total building electricity use [7]. Solar heat gain via fenestration contributes to a significant proportion of building envelope cooling load [8]. Daylighting has long been recognized as an important and useful strategy for visual comfort, and building energy efficiency and conservation [9] and [10]. People expect good natural lighting in their working places [11]. Energy savings resulting from daylighting mean not only low electric lighting and reduced peak electrical demands, but also reduced cooling loads and potential for smaller heating, ventilating and air-conditioning (HVAC) equipment size [12] and [13]. The initial, running and maintenance costs of a building due to a smaller HVAC plant capacity and peak electrical demand can be lowered. Renewable energy and energy conservation schemes would be an apposite building energy policy. Semi-transparent building integrated photovoltaic (BIPV) panels can provide electricity and apt to daylighting schemes that enhance visual comfort, reduce peak electrical and cooling demands, and conserve building energy expenditures [14] and [15]. Building integrated installation can offset construction costs. Such a PV system would be appropriate for air-conditioned office buildings. Life cycle assessment of PV facility is an essential process for justification [16] and [17]. This paper studies the semi-transparent BIPV systems used in an air-conditioned building with daylight-linked lighting controls. Technical data including daylight illuminance, solar irradiance and output power are recorded and analyzed. The performance of such PV panels is elaborated in terms of energy, environmental and economic aspects, and design implications are discussed.

Field measurements of a semi-transparent amorphous silicon PV module were conducted. Important parameters including the daylight illuminance, solar irradiance and the power generated were measured and presented. It was found that the mean measured visible light and solar irradiance transmittances were 11.7 and 11.4%, respectively, and the daily mean electricity conversion efficiency was 6.3%. Case studies based on a generic reference office building were carried out to elaborate the performance of such PV systems in terms of energy, environmental and economic issues. When semi-transparent PV panels together with the dimming controls were used, the annual building electricity saving of 1203 MWh and peak cooling load reduction of 450 kW were determined. In environmental point of view, the annual emissions of CO2, SO2, NOx and particulates could be reduced, respectively by 852, 2.62, 1.45 and 0.11 tons. In view of financial aspect, the simple monetary payback of just around 15 years was estimated if electricity tariff, chiller plant cost and CO2 trading were considered. The semi-transparent BIPV facades produce electricity, reduce solar heat gain and facilitate daylighting schemes that save lighting energy consumption and lower cooling requirements. Building integrated installation can offset construction costs. The findings can help architects and building professions estimate the likely benefits using such building schemes and contribute to the establishment of a renewable and sustainable energy policy target for providing a healthy environment.