PV Integration and DC Networks

Duration /
2014–2017

Funding /
Commission for Technology and Innovation (KTI)

A/S Team /
J. Hofer, Z. Nagy, A. Schlueter

In Swiss buildings, heating, ventilating and air-​conditioning accounts for roughly 40% of the overall energy demand. Therefore, the goals of the ’Energy Strategy 2050’ and the Swiss climate strategy can only be met if buildings become much more energy-​efficient compared to the current situation and if the remaining demand can primarily be met by renewable energies.

The vision of SCCER Future Energy Efficient Buildings & Districts (FEEB&D) is to enable the reduction of the overall energy demand of the Swiss building stock by a factor of five during the next cycle of building renewal by renovation or replacement without compromising on functionality, comfort or cost. The realization of this vision depends on solutions at different levels, which likewise determined the structure of the project:

Work Package 1 – Building Envelope

Work Package 2 – Building Energy Management

Work Package 3 – Urban Decentralized Energy Systems

Work Package 4 – Market Diffusion and Implementation Technologies

These interdisciplinary tasks were performed by research groups at EMPA, ETH Zurich (ETHZ-​BP, ETHZ-​IFA, ETHZ-​A/S, ETHZ-​SUSTEC), EPFL (EPFL-​LESO), University of Geneva, and Universities of Applied Sciences (HSLU, FHNW) in close collaboration with industrial partners in building materials, building control, energy planning and energy supply as well as public authorities such as cities and cantonal authorities.

Our contributions within WP2 Building Energy Management focused on novel approaches, toolsets and applications in the field of building systems integrated photovoltaics (BSIPV) using high-​efficiency thin-​film CIGS (copper indium gallium selenide) photovoltaic modules in conjunction with building-​scale direct current (DC) power grids and storage to optimally harness solar electricity. Using the DC output of PV systems directly in a building is a promising way of increasing the efficiency of the overall system as AC/DC power conversion losses can be avoided.
 
Due to the low weight, thinness and the possibility to adapt to non-​standard shapes, flexible thin-​film PV modules offer new opportunities for BSIPV. A key challenge for the successful application of high-​efficiency CIGS-​based systems in a building context is the occurrence of partial shading of PV cells that strongly influences efficiency and may cause overheating, and thus highly constrains design options. Successful integration into building surfaces and systems can contribute to both the economic success of this type of thin-​film PV and to the increase of electricity generated from renewable sources necessary for the transition of the energy system.

Selected Publications /
1 / J. Hofer, A. Groenewolt, P. Jayathissa, Z. Nagy, A. Schlueter. "Parametric Analysis and Systems Design of Dynamic Photovoltaic Shading Modules," in: Energy Science & Engineering, Volume 4, Issue 2 (2016): 134–152. DOI Research Collection
2 / J. Hofer, B. Svetozarevic, Z. Nagy, A. Schlueter. "DC Building Network and Storage for BIPV Integration," Paper presented at the CISBAT 2015, Lausanne, Switzerland, 9.-11. September 2015. Research Collection
3 / D. Rossi, Z. Nagy, A. Schlueter. "Soft Robotics for Architects: Integrating Soft Robotics Education in an Architectural Context," in: Soft Robotics 1.2 (2014): 147-​153. DOI Research Collection