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Whilst present buildings are still often energivorous systems, in the near future they will have to be converted to (or replaced by) zero energy buildings, also capable to export green energy (produced on-site by renewables) towards other buildings and/or users. Specifically, the paper focuses on the performance of naturally ventilated BIPV façade elements taking into account the total heat flow inside the building and the temperature of the building walls. 3 Building integrated photovoltaic collectors In the next few years, a further diffusion of PV collectors will be achieved by Building Integrated Photovoltaic (BIPV) devices, that will also overcome the unesthetic and functional issues of stand-alone and building-adjacent PV systems. 7 Building envelope technologies In order to reduce the heating and cooling energy demands of buildings and/or to improve the related comfort performance, different innovative envelope materials and/or design solutions for opaque and transparent building elements can be adopted. [Extracted from the article]

Abstract This paper presents a detailed exergetic and technoeconomic analysis of a Building Integrated PhotoVoltaic Thermal (BIPVT) system. BIPVT system, consisting of flat-plate PVT solar collectors, is integrated in the south facing façade of a non-residential high-rise building. BIPVT collectors produce: i) thermal energy for space heating purposes, by a radiant floor system; ii) Domestic Hot Water (DHW); iii) electricity. Electric air-to-water heat pumps/chillers and a condensing gas fired boiler are used as auxiliary systems for space heating/cooling and DHW, respectively. In addition, the system also includes an electricity storage system coupled to the BIPVTs in order to mitigate the effects of solar energy intermittency and to obtain a virtually grid-independent system. In order to compare the proposed BIPVT system to a conventional building, a reference building model, i.e. without BIPVTs, energy storage and radiant floor, is considered. Here, the space heating and cooling energy is supplied by air-to-water heat pumps (one for each floor), DHW is produced by a condensing boiler and electricity is supplied by the national grid. The comparison is performed for three thermal zones, well representative of the thermal behaviour of the whole building. In this paper, a detailed dynamic simulation model is developed by means of well-known tool TRNSYS 17, in order to predict the transient behaviour of BIPVT system. Energy and exergy balances are taken into account to determine, for the 1-year operation, the exergy destructions and exergetic efficiencies of each of the investigated components. The economic viability of the proposed system is also discussed and the resulted Simple Pay Back period is about 4 years. From the carried out exergy analysis, the average exergetic efficiency of electricity storage system is about 90%, whereas the condensing boiler one is close to 2% all year long. In addition, an exergy analysis on the proposed BIPVT system located in several European weather zones is also carried out, as well as a suitable exergy analysis is performed by varying the capacity of the electricity storage system. Such analyses aim to assess the weather condition and the size of electricity storage effects on the destroyed exergy and exergetic efficiency of BIPVT collectors and electricity storage, respectively. It resulted that, the highest destroyed exergy of BIPVT occurs in Larnaca (150 MWh/year) vs the lowest one in Belfast (87 MWh/year), whereas the BIPVT collectors exergetic efficiencies range from 8.4% for Larnaca to 8.8% for Belfast. Highlights • Exergy and thermoeconomic analysis of BIPVT - electricity storage system. • Assessment of exergy destruction and efficiencies of main system components. • Case study for a non-residential building in different European weather zones. • Analysis of heating, cooling, DHW and electricity production. • Assessment of exergetic, energy and economic enhancement vs. traditional systems. [ABSTRACT FROM AUTHOR]

This paper aims at optimizing the energy performance of an innovative integrated collector-storage solar water heater (ICSSWH) prototype. The system incorporates a high-vacuum gap, which significantly reduces convective thermal losses, and a serpentine absorber system coated with a low-E layer to minimize radiative thermal losses. The methodology is based on a detailed dynamic simulation model, implemented in the MatLab environment, suitable conceived to accurately predict the energy performance and economic profitability of the ICSSWH under various weather conditions and energy market prices. This approach aims to initially identify the most influential geometrical, thermophysical and optical parameters that impact the energy performance of the system through the assessment of different objective functions. After identifying the most influential parameters, the range of existence with the interval step for each variable is defined, and the optimization procedure is conducted to determine the optimal set of variables that maximize/minimize the selected objective functions. To demonstrate the effectiveness of the proposed methodology, a proof of concept was conducted to optimize the energy performance of novel ICSSWH by considering nineteen parameters with the aim of maximizing/minimizing three different objective functions. The results of this analysis yielded various sets of optimised parameters for the ICSSWH. Therefore, by implementing the set of optimised parameters into the dynamic simulation model, the energy performance of the optimised and non-optimised ICSSWH collectors was evaluated in 42 different weather zones and compared to a reference case scenario. [ABSTRACT FROM AUTHOR]

In this paper a novel Concentrating Photovoltaic/Thermal Glazing system (CoPVTG), developed at the Centre for Sustainable Technologies of the University of Ulster (Belfast, UK), and exploiting concentration technology, is presented and investigated. The innovative device consists in two glazed panels of which the external one is moulded to form several lenses that concentrate the solar radiation onto photovoltaic cells lines. Thanks to the specific behaviour of these lenses, the solar radiation is capable to reach the indoor environment during the winter months (when it's more useful), while it ends onto the photovoltaic cells during the summer months (reducing the solar gains while also providing electricity to the building). To increase the electricity production, a forced air flux can be created inside the glazed cavity to reduce the PhotoVoltaic cells temperature, and the obtained hot air can be exploited for diverse purposes. Finally, such device is conceived to be integrated into existing windows framing to boost its adoption in new or refurbishment construction. With the intention of studying the device under a wide range of boundary and working conditions, a dynamic simulation tool was developed in MATLAB environment and validated trough experimentally gathered data. With this tool it is possible to investigate the performance of the novel device integrated into several buildings. Specifically, a case study analysis was performed by considering an office building located in five different localities. From the conducted analyses, interesting results and design criteria are obtained. Specifically, the CoPVTG adoption returns higher electricity yield vs. standard semi-transparent window, ranging between 54 and 84% in case of cold and hot weather zones, respectively. In term of overall economic performance, the adoption co CoPVTG allow for a HVAC system running cost reduction, for the investigated case study, ranging from 20 to almost 100% depending on the considered weather zone. • Novel building integrated concentrating photovoltaic thermal glazing system. • Modelling and dynamic simulation of smart building facades for energy efficiency. • Analysis of photovoltaic yield of concentrating and standard solar windows. • Analysis of passive effects of building integrated PV/T glazing systems. [ABSTRACT FROM AUTHOR]

This paper focuses on a novel energy management approach, namely Building to Vehicle to Building, in which electric vehicles act as vector devices for renewable energy exchanges among buildings. The main goal behind this concept is to benefit from the potentiality of electric vehicles toward the achievement of the zero-energy target extended to a buildings cluster level, by exploiting renewable generation on- and off-site. To this aim, a dynamic simulation tool is developed to assess the energy and economic performance of the proposed V2B2 scheme applied to a cluster of multiple users made of non-residential buildings and electric vehicles with bidirectional charging, used as a back-up power supply for increasing self-consumption of energy produced on-site by PV panels integrated in one of the buildings, to be also exploited off-site by other users. A case study analysis is conducted for a sample cluster of 3 building sand 3 electric vehicles, located in a Mediterranean city (Naples, Italy) with the aim at conducting the proof of concept. Simulation results show that the proposed V2B2 scheme enhances the match between the on-site renewable generation and the whole system demand, i.e. buildings and electric vehicles' needs, by reducing the grid operation and boosting the system economic convenience. The proposed energy management scheme represents an example of novel aggregator energy and business model which will play a crucial role in the next generation of smart cities and communities. • Building to Vehicle to Building concept for multiple users and electric vehicles. • Development of a dynamic simulation tool for the energy and economic analysis. • Increasing the share of self-consumed PV production at a virtual micro-grid level. • Electricity delivered from the grid reduced up to 11.4% and economic saving of 8.1%. [ABSTRACT FROM AUTHOR]

An advanced mathematical model capable of simulating the energy performance of an innovative Integrated Collector Storage Solar Water Heater (ICSSWHs) is presented. Usually, ICSSWH devices available in the market are typically simple and low-cost, combining solar heat collection and storage functions in one unified vessel. However, they exhibit higher heat loss characteristics when compared to standard solar collector systems, with a subsequent reduction in energy performance during night-time and non-collecting hours. An innovative ICSSWH prototype was developed at the Centre for Sustainable Technologies (CST) at Ulster University using a patented, innovative thermal diode feature, attained by incorporating a liquid-vapour phase change material (PCM) and very low pressures. In order to fully investigate the energy performance of the proposed prototype, a suitably dynamic simulation model has been developed and validated in MatLab environment. All modelled temperatures are ±1 °C from the respective experimental measurements. The developed model has been used to evaluate the ICSSWH energy performance by varying several pivotal parameters (physical features and materials) in order to produce an optimised device. • A novel thermal diode feature is achieved by incorporating a liquid-vapour PCM in a multi-vessel solar water heater. • Dynamic simulation analysis is used to characterise a thermal diode feature in a novel ICSSWH unit. • MatLab environment was used to develop to model the novel thermal diode operation, validated using experimental data. • All modelled temperatures show good agreement with the experimental measurements. • Thermal diode ICSSWHs can produce higher temperatures than simpler ICS units. [ABSTRACT FROM AUTHOR]