Solar energy

New silicon PV and thin film PV material and device developments

While the average user might only be acquainted with standard Silicon-based solar cell technology, the field of photovoltaics is in continuous evolution. Cells based on new thin-film absorber materials, like perovskites or CIGS, are approaching conversion efficiencies of Si cells at potentially lower cost and with more flexible sizing.

Understanding the material and device properties of these new perovskite solar cells is crucial to develop the processes that enable the realisation of devices with highest performance. This is why EnergyVille demonstrates these new materials and device architectures not only on small lab-scale devices but also on large area (30x30cm²) modules, and even full integration in final applications like buildings, vehicles and infrastructure.

High efficiency PV cell and module technology

To harvest as much energy as possible, EnergyVille is looking into various ways to improve the efficiency of PV-cells and module technologies. Bifacial crystalline silicon PV modules have recently gained a lot of interest because they can accept light from both sides in this way increasing the energy yield of the modules.  EnergyVille takes these highly efficient bifacial cells as a starting point and combines them with optimised cell metallisation techniques and multi-wire interconnection technologies. This has resulted in a record-setting efficiency of 23.2% using bifacial n-PERT solar cells..

Building further on these evolutions, we have developed the concept of woven interconnection sheets by weaving encapsulant ribbons and metal wires into one fabric. This concept saves on materials and eliminates multiple process steps while it can still be run on industry-standard laminators, which are all significant advantages. Hence, this interconnection technology is a valuable new building block for our work in building and vehicle integrated PV.

Tandem cells

By combining two (or more) different solar cells with carefully selected material properties on top of each other in so-called tandem configuration, we can convert a wider part of the light spectrum into electrical energy. In this way we surpass the physical limitations of single solar cells. E.g. by combining a perovskite top cell on a silicon bottom cells, EnergyVille aim at reaching +30% tandem energy conversion efficiency which is larger than the theoretical maximum of about 28% of silicon solar cells.

At EnergyVille we explore different material combinations, processes and contacting configurations (2-terminal, 4-terminal tandems) towards realising large area (e.g. M2 size and up to 30cm x 30cm), stable and reliable tandem devices.

Integration of PV in building façades, vehicles and infrastructure

Bringing the energy source closer to the place of consumption and its integration into the built environment helps facilitating the sustainable energy transition by providing distributed generation. Doing so, EnergyVille explores the integration of PV into building façades, vehicles and other applications. This requires a close collaboration between experts on PV, architecture, building physics, and electrical engineering. Application-defined requirements drive the EnergyVille research in module converters and electronics, PV materials, PV cell and module technology, reliability testing, and energy yield simulation. Through large-scale demonstration projects we validate these technology and simulation results in real-life conditions.

Aesthetics and bespoke dimensions are a must in building-integrated PV (BIPV). EnergyVille works on the integration of PV in prefabricated elements, e.g. for curtain wall façades, and the implementation into planning tools to facilitate the design and manufacturing. We research aesthetic and reliable interconnection technology that enables mass customisation. We envisage a module assembly tool which, based on the input of architectural software, automatically assembles custom-made modules. Our multi-wire cell interconnection technology can flexibly adapt to module dimensions and will facilitate the implementation of Industry 4.0 principles.

Both for integration into buildings and vehicles, we also explore adapting the PV module’s shapes and dimensions in the EnergyVille labs. Here, non-uniform and dynamically varying illumination calls for novel module technologies that enable efficient energy harvesting under various conditions. By combining reconfigurable module topology with the multi-wire interconnection technology, EnergyVille aims to bring about a paradigm shift for the next generation of PV modules.

PV cell and module analysis and performance optimisation

Since PV modules are applied in a variety of ways, assessment of their performance beyond testing under standard laboratory conditions is required. This has been largely recognised by the industry preparing novel IEC standards. We are closely involved in this process, and it is based on these insights that we have selected our tools.

EnergyVille has a first of a kind large area module tester using LED lighting in which we can simultaneously illuminate the front and back-side of full size PV modules. Spectral and light intensity variations can be resolved to fully mimic varying outdoor conditions. We also have outdoor measurement sites in rack and façade configuration, complementing our indoor measurement capabilities. In these systems we can measure PV module power with high precision and at very small time intervals. Combining this with extensive meteorological measurements, our research in BIPV, reliability and energy yield simulation and forecasting is excellently equipped.

Focused on exploration of new materials and technologies, we ensure that both industrial and small research samples can be measured in all our characterisation tools. Our cell and material and reliability characterisation research is supported by vast variety of opto-electrical characterisation tools (e.g. spectral response, reflectivity mapping, spectroscopy, high-resolution electroluminescence imaging) and material analysis tools (e.g. optical and electron microscopy, cross-section preparation tool, adhesion tester). Combining this broad set of characterisation capabilities together with the insights of our specialists enable us to understand the root causes of PV module performance reduction or failure and devise routes for performance optimisation.

PV module reliability, recycling and re-use

In reducing the levelised cost of electricity, lowering the degradation rate and preventing premature failures of PV modules are as equally important as efficiency. ‘Design for reliability’ is the foundation of various research activities performed at EnergyVille in the field of PV module reliability.

EnergyVille conducts in-depth reliability testing of the next generation of PV module materials and technologies. While we are applying standard accelerated test methods, our work goes beyond,  establishing new tests and supporting the development of new standards. We design targeted reliability studies to investigate the weak points of the materials or technologies. By combining opto-electrical characterisation with destructive material analysis, we are able to uncover the underlying failure modes.

• EnergyVille has various climate chambers for accelerated reliability testing such as thermal cycling, humidity and damp-heat tests. We can also combine these tests with UV illumination.
• For PV module aesthetics, colour stability is important. EnergyVille has the equipment and experience to determine colour stability and various across a module and between different modules.
• We have a lot of experience in carrying out and analysing various degradation mechanisms like e.g. PID (potential induced degradation), LID (light induced degradation), LeTID (Light and elevated temperature degradation), ...

PV module reliability also plays a crucial role in reducing the ecological footprint of PV. One element is technology design and material selection for improved recycling and elimination of toxic materials. Through prolongation of the operational lifetime and refurbishing or reuse of PV modules, we aim to further lower the environmental impact of PV panels.

PV power converters (including modelling, testing and reliability)

In particular in building-integrated photovoltaics (BIPV), not all PV modules may generate the same power, voltage or current, owing to partial shading, reflections, and differences in sizing or orientation. To maximise the energy production in these circumstances, EnergyVille works on the development of customary electronic solutions that can adapt to a specific application. Novel module and converter technologies that enable efficient energy harvesting in non-uniform and dynamically varying conditions need to be optimised jointly. Therefore, we conduct research on power converters, which is linked to the work on DC buses and micro-/nanogrids. One of the most innovative but also challenging solutions is based on the idea of changing the electrical interconnection between the PV cells in real time as the PV module adapts to its environment. We propose a reconfigurable smart PV (RSPV) module concept that considerably increases energy harvesting in non-optimal conditions. This module integrates switches and intra-module converters into its own volume in order to make the self-reconfiguration possible.

Both for standard and reconfigurable PV modules, module level and intra-module converters must be compact for integration and must match the stringent reliability requirements. This asks for reliability testing and understanding of potential failures beyond the current standard metrics and measurements. We aim to not only measure failure rate but also degradation rates of such novel converter designs. For this we use accelerated synthetic mission profiles.

PV energy yield metrology, simulation & forecasting

When it comes to solar energy, optimal energy yield is key. The energy performance of PV modules is measured indoors under standard testing conditions. However, in reality, outdoor conditions vary and deviate significantly from these defined conditions. To analyse the gap between indoor and outdoor performance and to determine the optimal yield for PV panels in a given situation, EnergyVille has developed both indoor and outdoor testing setups and an accurate energy yield simulation model.

Our metrology techniques provide high-accuracy energy  measurements in correlation with meteorological parameters, and advanced data analysis for the interpretation of causes and effects.

EnergyVille’s energy yield simulation model is a scenario-based software which accurately simulates the expected daily energy yield of solar cells and solar modules under varying meteorological and irradiation conditions using available historic weather data. The model combines optical, thermal and electrical parameters to provide detailed insight on thermal variations in the solar module. The model integrates the effect of these variations, resulting in a significantly better accuracy than commercially available software packages for energy yield estimation.  The simulation model is ideally suited to determine accurately the energy yield performance of new types of PV technology (e.g. bifacial PV plants) and in special conditions (e.g. floating PV, agri-PV, in BIPV, on trackers, on non-flat terrain, ...).

Furthermore, we are developing another modelling environment for the integration of PV into building envelopes, taking into account the thermal and electrical performances and mutual influences.

Simulation of the highly variable PV power generation in combination with battery storage and load management, taking into account grid conditions, is conducted in order to optimise system configurations for a range of applications, in order to obtain high degrees of self-sufficiency and self-consumption of the generated energy. This links the work on PV generation to the topics of battery system development, energy management and grid integration.