Photovoltaics

  • 30.2 Percent Efficiency – New Record for Silicon-based Multi-junction Solar Cell

    Wafer-bonded III-V / Si multi-junction solar cell with 30.2 percent efficiency. ©Fraunhofer ISE/A. Wekkeli

    Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with the Austrian company EV Group (EVG) have successfully manufactured a silicon-based multi-junction solar cell with two contacts and an efficiency exceeding the theoretical limit of silicon solar cells. For this achievement, the researchers used a “direct wafer bonding” process to transfer a few micrometers of III-V semiconductor material to silicon, a well-known process in the microelectronics industry. After plasma activation, the subcell surfaces are bonded together in vacuum by applying pressure. The atoms on the surface of the III-V subcell form bonds with the silicon atoms, creating a monolithic device.

  • Nanotechnology for energy materials: Electrodes like leaf veins

    SEM – model of a metallic nano-network with periodic arrangement ( left) and visual representation of a fractal pattern (right). Credit: M. Giersig/HZB

    Nano-sized metallic wires are attracting increasing attention as conductive elements for manufacturing transparent electrodes, which are employed in solar cells and touch screen panels. In addition to high electric conductivity, excellent optical transmittance is one of the important parameters for an electrode in photovoltaic applications.

  • Photovoltaics and Photosynthesis

    The agrophotovoltaics (APV) pilot plant located in Heggelbach near Lake Constance couples the production of electricity and food crops ©Fraunhofer ISE

    Pilot Plant at Lake Constance Combines Electricity and Crop Production

    In 1981, an article by Prof. Adolf Goetzberger titled "Potatoes under the Collector" was published in the German magazine “Sonnenenergie”. The article proposed a particularly favorable setup for solar energy systems in combination with agricultural land use. After smoldering on the backburner for a couple of years, the concept of agrophotovoltaics (APV), that is, the dual usage of land for crop and electricity production, was again taken up by researchers at Fraunhofer ISE in 2011.

  • Transporting more electricity through new lines

    Both the wires in the core and the aluminium zirconium wires in the jacket contribute to the tensile strength.  © 3M Deutschland GmbH

    The volume of electricity generated by wind energy and photovoltaic systems is increasing in the German power grid. This electricity has to be transported over long distances to urban areas and industrial centres. Newly developed high-temperature conductors now offer a way of increasing the maximum power capacity that can be transmitted through existing power lines. The BINE Projektinfo brochure entitled "The hotline in the grid" (13/2016) presents the new transmission lines. With a comparable conductor cross-section, these can almost double the transport capability of existing transmission lines.

  • Upgrade for Biogas

    Liquid energy reservoir: Prof. Josef Hofmann demonstrates how to extract ice-cold biomethane. This compound is a thousand times more energy rich than biogas. Hochschule Landshut

    Biogas facilities are important drivers for the energy transition, yet, for many operators, they are no longer profitable. Conversion to biomethane can make such facilities more flexible and energy efficient ─ as well as opening up new business segments to the operators. Researchers at the Landshut University of Applied Sciences and the Weihenstephan-Triesdorf University of Applied Sciences have developed just such a process. Germany is scheduled to be generating 55 to 60 per cent of its electrical power from renewable energy sources by 2025 – currently it is around a third. However, photovoltaic systems only achieve their full capacity during the day in summer, and wind energy plants are usually only viable in exposed areas. The power demand during the dark winter months outstrips the production capacity of renewable sources. To some extent, biogas plants can compensate for these fluctuations and help to secure power continuity.