U-light (Ultra Lightweight PV Modules and Their Applications in Innovative PV Systems Achieving Lowest LCOE)

  • Funding call: SOLAR-ERA.NET Transnational Calls PV2 and CSP2 within the EU Framework Programme FP7 for Research and Innovation
  • Support code: SOLARERANET2-090
  • Amount of funding: € 788,752.00
  • Duration: 11/2015 to 10/2018
  • Consortium: ISC Konstanz (coordinator), Zurich University of Applied Sciences (Switzerland), Polymer Competence Center Leoben (Austria), ISOVOLTAIC (Austria) 


The price of PV modules has dramatically declined over the last couple of years and the price of a PV system is nowadays dominated by the corresponding Balance of System (BOS) costs. For the further dissemination of photovoltaic power, it is thus necessary to reduce the lowest levelised cost of energy (LCOE) by reducing the cost of the system components, keeping the system’s lifetime at least constant and maximising the system’s energy yield. In order to achieve lowest LCOE values, it is necessary to lower the cost of the BOS while achieving the highest possible energy yields per installed power.

The U-light project addresses key steps for reducing the LCOE by reducing the cost of material and the cost of installation and construction, enhancing the module’s efficiency, developing light-weight PV modules with reduced bills of material, enhanced energy yield per nominal power and easy-to-install features.

The PV modules to be developed shall be designed in such a way that the predicted lifetime should be at least equal to the lifetime achieved by state-of-the-art PV modules. Furthermore, the PV modules’ light-weight design will open up various new markets involving building-integrated photovoltaics (BIPV) applications, such as parking roofs and greenhouses.

The U-light project will examine two options for light-weight modules:

  • light-weight modules based on solar glass with thicknesses below 2 mm, aiming at 1 mm and less, with lifetimes approaching forty years in a European environment, and

  • light-weight modules using glass-fibre reinforced plastic (GRP) as glass replacement in combination with applications where damage due to hail and wind can be avoided. 

Both options will include the development of highly transmissive encapsulation and highly reflective back-sheet materials with significantly decreased lamination cycle times and strongly reduced thickness to further impact the module weight.


The U-light project aims to develop new light-weight, high-efficiency and long-lifetime modules with regard to lowest cost for integration into PV systems, achieving lowest values of levelised cost of energy. The development will focus on thin, strong, low-cost solar glass and the use of compositions (mineral or organic) like glass-fibre reinforced plastic (GRP). Besides weight reduction, key goals of this project are long-term durability, failure probability, and high energy harvest.

A strong emphasis is put on the development of novel kinds of thin glass and encapsulants with highest light transmissivity and low UV cut-off as well as the development of back-sheet materials with a 20% (abs.) higher reflectivity compared to state-of-the-art products. These developments will make it possible to achieve lowest cell-to-module losses. With the new back-sheet materials, the consortium aims to reach reflectivities above 90%, while the new encapsulants should allow for a UV cut-off below 320 nm and an outstanding transparency in the wavelength range from 400 to 1000 nm.

Furthermore, additional cost savings should be achieved by reducing the lamination time of the respective encapsulant materials to less than 10 minutes since the lamination step in particular is the bottle neck preventing lower cycle times in production. The cost reduction potential resulting from reduced module weight in combination with bifaciality will open up new applications, for example greenhouses and parking roofs. For these applications, alternative concepts, such as the use of GRP as an alternative to glass, are evaluated as part of the project.

Cell development will be based on the latest generation of ISC Konstanz’s highest-efficiency solar cells, for example the bifacial BISON cell or the back-contact ZEBRA cell. A focus is set on developing ZEBRA solar cells with intrinsic bypass diodes, which is possible without any additional costs. This will allow for the production of solar modules without bypass diodes and lead to a price reduction on the module level and, more importantly, an increase of product lifetime since failing diodes can thus be avoided – and with them one of the main defects of solar modules in the field.