Energy performance analytical review of semi-transparent photovoltaics glazing in the United Kingdom

This work reviews the recent achieved advancement in semi-transparent photovoltaics (STPV) glazing systems, which are considered as a possible solution to improve the thermal performance of buildings. A numerical model was developed utilising EnergyPlus to investigate the impact of integrating STPV glazing systems in the United Kingdom. The simulation investigated the overall energy consumption under different Window-to-Wall ratio (WWR) for south-oriented STPV glazing systems with different transparencies and materials. The results indicated that employing clear double-glazing in small glazing situation at WWR = 30% would reduce the overall energy consumption by (7.5–26) % depending on the implemented STPV glazing systems. Furthermore, applying STPV glazing system in large glazing (WWR ≥70%) would lead to a decrease in the overall energy performance by 40% compared with the conventional clear double-glazing systems. However, utilising STPV glazing systems in medium-sized glazing is dependent on the solar material that is used. The results indicated that employing a-Si STPV glazing system is inefficient when the glazing cover (30% < WWR <70%) comparing to the clear double-glazing system. This result is a consequence of to the thermal and optical characteristics of a-Si solar cells. These characteristics would eventually lead to a higher heating and lighting requirements

Quantifying of vision through polymer dispersed liquid crystal double-glazed window

The visual linking of a building’s occupants with the outside views is a basic property of windows. However, vision through windows is not yet a metricized factor. The previous research employs a human survey methods to assess the vision through conventional windows. The recently fabricated smart films add a changeable visual transparency feature to the windows. The varied operating transparency challenges the evaluation of vision. Therefore, surveying human preferences is no longer a feasible approach for smart windows. This paper proposes an image-processing-based approach to quantify the vision quality through smart windows. The proposed method was experimentally applied to a polymer dispersed liquid crystal (PDLC) double-glazed window. The system instantaneously determines the available contrast band of the scenes seen through the window. The system adjusts the excitation of the PDLC film to maintain a desired vision level within the determined vision band. A preferred vision ratio (PVR) is proposed to meet the requirements of occupant comfort. The impact of the PVR on vision quality, solar heat gain, and daylight performance was investigated experimentally. The results show that the system can determine the available vision comfort band during daytime considering different occupant requirements

State-of-the-Art Review on the Energy Performance of Semi-Transparent Building Integrated Photovoltaic across a Range of Different Climatic and Environmental Conditions

Semi-transparent Building Integrated Photovoltaics provide a fresh approach to the renewable energy sector, combining the potential of energy generation with aesthetically pleasing, multi-functional building components. Employing a range of technologies, they can be integrated into the envelope of the building in different ways, for instance, as a key element of the roofing or façade in urban areas. Energy performance, measured by their ability to produce electrical power, at the same time as delivering thermal and optical efficiencies, is not only impacted by the system properties, but also by a variety of climatic and environmental factors. The analytical framework laid out in this paper can be employed to critically analyse the most efficient solution for a specific location; however, it is not always possible to mitigate energy losses, using commercially available materials. For this reason, a brief overview of new concept devices is provided, outlining the way in which they mitigate energy losses and providing innovative solutions for a sustainable energy future

Thermal Loss Reduction Using a Ventilated Double-Glazed Window for Commercial Buildings in Average-Climate Environments

The power consumption of buildings is exacerbated in modern societies. The most effective load in buildings is heating and cooling systems. Numerous studies have been done on energy saving for buildings recently. Windows are one of the most thermal loads that cause the loss of heat from inside to outside a room during winter. This paper demonstrates an alternative insight into the use of double glazed windows in average climate environments. The proposed system uses an air inject system to impact the heat transfer properties of the window considering the trade-off between the heating load energy saving and air injection power consumption. The theoretical analysis showed a reduction of 52 % in the thermal loss of the window, in addition to a declination in the heat transfer coefficient of the window from 3.5 to 1.8 W/m2K. Consequently, an energy saving of 19 % in the heating capacity has been achieved

Optimisation of wasted air utilisation in thermal loss reduction in double-glazed windows of commercial buildings in cold regions

Ventilating of multi pane-glazed windows using wasted air of buildings is an effective technique to minimize heat loss through windows and save heating energy in cold regions. In low-scaled occupancy buildings with high WWR ratio, buildings supply a low flow rate of wasted air to windows ventilation systems, resulting in a declination in its thermal performance. Therefore, this study introduces methods of managing the utilisation of wasted air in windows ventilation to optimise the energy saving. Two methods have been implemented experimentally on a small-scaled room. The first method is a time-based division of air pump operation, an air pump ventilates multiple windows, one window at a time repetitively. The second method shares the available wasted air to multiple windows. The experimental results and mathematical heat transfer model have been employed to evaluate thermal performance of the system in different methods. The first method showed a best energy saving with a duty cycle of 50% for the air pump, and on/off operation every 10 s. An energy saving of 42.6% has been realized compared to the traditional double-glazed windows, and the heat transfer coefficient was declined from 3.82 to 2.8 W/m2 K. The second method showed an optimum thermal performance when the available flow rate of wasted air was shared with three double-glazed windows. An energy saving of 83.1% was achieved compared to the traditional double-glazed windows, and the heat transfer coefficient dropped from 3.82 to 2.36 W/m2 K

A unified global investigation on the spectral effects of soiling losses of PV glass substrates: preliminary results.

The present work reports on the initial results of an international collaboration aiming to investigate the spectral effects of soiling losses. Identical glass coupons have been exposed outdoors for eight weeks in different locations worldwide, and weekly direct and hemispherical transmittance (T%) measurements are compared. Maximum losses as high as 7% and 50% in hemispherical and direct transmittance, respectively, have been found during the 8-week outdoor exposure. At the end of the data collection, a preliminary analysis of the spectral impact of soiling has been performed. The results show that the blue end of the spectrum is more affected and that lower hemispherical T% correlate to larger area covered by particles

Modelling photovoltaic soiling losses through optical characterization

The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (IR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Ångström turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of PV modules from the particle size distribution and the cleanliness value

Thermal performance evaluation and energy saving potential of semi-transparent CdTe in Façade BIPV

Semi-transparent PV glazing are promising in Building Integrated Photovoltaic (BIPV) applications. They provide daylight control, energy saving and power generation. The selection of optimal Photovoltaic (PV) glazing requires the accounting for various factors such as location, orientation and glazing transparency. In this work, thermal performance of Cadmium telluride (CdTe) based semi-transparent PV glazing of different transparencies was evaluated in UK for South and South-West orientations. Thermal performance was analysed in terms of U-value, SHGC and cooling load. Results revealed that least transparency CdTe PV glazing can have U-values as low as 1.52 W/m2K. The use of least transparency PV glazing can reduce 96% of solar heat gains and 23.2% of cooling energy compared to conventional clear glazing when used in South-West orientation. The selection of optimum glazing was discussed taking into consideration occupants’ optical comfort and health