Gholamalipour, M; (2006) Detailed PV cladding design for office refurbishments. Doctoral thesis , UCL (University College London).

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Abstract

A great concern for those aiming to reduce energy consumption in UK buildings to achieve Kyoto agreement targets should be the growing trend in installing air-conditioning in refurbishment office buildings. This study takes this challenge into account and presents an innovative cladding design for office refurbishment. The design incorporates photovoltaic power, solar control, day lighting, night ventilation and mechanical ventilation with heat recovery driven by photovoltaic power. By careful design the goal is to maximize the use of solar radiation and consequently maximize the PV energy output, maximize the use of daylight which is followed by a great decrease in electrical lighting consumption and reduce unwanted solar gains and possible glare to such an extent that mechanical heating and cooling is not significantly required to maintain comfort condition. The innovative cladding is designed for a typical assumed office module in London. Important components of the innovative south facing cladding design are photovoltaic panels, fan including heat recovery and window with openable parts at different levels. A careful design procedure determines the optimum tilts, length, positions and shape (louvered or not) of PV panel integrated into cladding as well as percentage of glazing area. Analysis recommends that in order to maximize PV energy output, the angle of the PV cell should be flexible changing according to solar irradiation (i.e. 22.5 , 45 and 67.5 ). Considering PV self shading, PV 1.60 m long generates the maximum energy output among other proposed options. Simulations indicate two positions for PV (during winter and summertime) and propose 3louvred PV panels 0.53 m long instead of a 1.60 m one. Software simulations indicate that integrating this innovative cladding design, comfortable condition is provided with far less energy consumption compared to air-conditioned offices. The results show that during the heating period, there are 50 hours per year when internal temperature is less than 21 C, so if occupants are prepared to accept 50 hours in a year with temperature below 21 C (e.g. by wearing more clothes), then no heating is required. If this is not the case, in order to omit entirely the need for central heating, it is proposed to use a 3 kW electric heater to provide comfort conditions. Therefore, heating consumption for this office will be 1.88 kWh/(m2.yr). Regarding cooling requirements, it is found that due to internal gains, overheating occurs in this office, but considering that there are only 193 hours per year when external temperature goes above 25 C, it is proposed to pre-cool the incoming air when external temperature is lower than 25 C, and when external temperature is higher than 25 C then higher fan speeds can provide extra air movement and comfort can be achieved on hot days. As ventilation consumption (i.e. 0.88 kWh/(m2.yr)) is calculated when fan is working on its highest speed (i.e. 203 l/s, 27W), the high fan speed for cooling during hot days does not increase energy consumption. In conclusion, this PV cladding design dose not only contribute to saving of energy for heating, cooling and ventilation compared to conventional new office facades, but also for lighting. A high degree of daylight use is enabled so that lighting energy consumption is only 6.27 kWh/(m2.yr). This study also compares the PV cladding design with a conventional office refurbishment option (i.e. new cladding with HVAC) regarding their cost and environmental impacts. Pollution created during manufacture is considered in terms of embodied energy and associated carbon emission. It is found that the PV panels of cladding module have a carbon payback time of 3.20 years. Implementing this innovative PV cladding design as the refurbishment option instead of the conventional system results in undiscounted saving of 377.71 and 450.08 £/m2 without and with grant respectively during 30 years (i.e. system life time). Considering the energy price increase at its current rate (i.e. 10%), discounted saving of 377.71 and 450.08 £/m (excluding and including grant respectively) can be achieved during 30 years. Also, this innovative cladding results in 97% decrease in annual C02 emission related to heating, cooling and ventilation compared to that of a conventional one. As the analysis shows, a big advantage of this cladding system is that there is entirely no need for any HVAC systems, therefore this innovative cladding design can reduce capital cost and minimize office energy consumption as well as C02 emissions.

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