Building integrated photovoltaic (BIPV) systems may be catalyzers of sustainable, near-zero energy buildings. To maximize the benefits of employing BIPV, it is important to integrate them properly into the grid of the building. The discussion on AC versus DC distribution for microgrid and nanogrid backbones is currently revisited as the level of penetration of renewable sources, electric vehicles and DC loads is constantly increasing. This paper tackles this question and provides guidelines using a validated simulation framework. The study compares DC (48 V and 380 V) and AC (230 V/50 Hz) topologies integrated into a ten-story office building with façade-integrated BIPV. Annual simulations are carried out for five locations with different climatic conditions and comparisons are made in terms of system- and component-level efficiency, system losses, self-sufficiency, self-consumption and CO2 emission. The analysis shows that the DC topologies perform better than the AC one, especially for the locations with high solar energy yield compared to the cooling and heating loads. Further, a parametric analysis is performed to determine the optimal sizing of the building grid components, DC and AC alike. Finally, different scenarios of battery energy storage system capacity are examined in order to test the sensitivity of the performed analysis. ... Read more

European legislation on building performance and energy efficiency pushes the shift towards minimizing the environmental footprint of buildings. Building-integrated photovoltaics (BIPV) is a promising technology that can accelerate the transition to energy-neutral buildings. Quantifying the potential of BIPV is crucial and one means of obtaining those results is through simulation. The state-of-the-art tools offer either thermal or electrical specialization; in particular, balance of system components (BOS) such as power converters have not been studied in detail within the building simulations BIPV domain. In this paper, a multi-physics model of a BIPV integrated DC/DC converter is developed in the Modelica language, taking into account the thermal and electrical couplings inherent to power electronic systems. The model has been validated using representative outdoor BIPV measurements and a DC/DC converter prototype. It has been found that the proposed model provides reasonable accuracy and outperforms an equivalent power conditioning model in TRNSYS. To demonstrate the model’s functionality, two case studies are performed. First, the temperature-dependence of the converter’s efficiency and losses is quantified and analyzed and, second, the prominent contributors to the converter losses are identified and discussed. ... Read more

Building-Integrated Photovoltaics (BIPV) replace traditional building elements with power generating elements through the use of solar cells. One of the targets for this technology is to place the module-level power converter into the photovoltaic module's frame to achieve an integrated system. Temperature is the most influential parameter for a converter's reliability, its damage caused on the components needs to be studied in detail. In this paper, a reliability comparison based on a four-day mission profile has been made in order to assess the most reliable frame position for this converter to be placed in as all of them possess a different temperature profile. The results show that placing the converter in the lateral bottom of the frame is significantly more reliable than the mid or top position. In addition, a lifetime analysis is performed on the converter's dc-link capacitor in order to demonstrate the required methodology. In future work, this can be extended towards other sensitive components when appropriate lifetime models become available. These lifetime estimations can then be combined to achieve an overall BIPV system lifetime assessment. ... Read more