Bifacial solar panels: more energy and more applications

Bifacial solar panels capture light not only from the front of the panel but also from the back. With double-sided solar panels (PV), we increase the electricity yield by about 10 to 20%. We are developing knowledge and technology for bifacial solar panels and a complete model that predicts energy yields.

Bifacial solar panels can reduce electricity costs enormously. For example, PV installations or projects produce the same amount of electricity on a smaller roof area. Also, fewer PV modules and system components are needed on the same base area, which leaves more light and rainfall available for ecology, for example.

Applications of bifacial solar panels

A bifacial PV panel generally consists of 60 or 72 solar cells. These solar cells have an almost identical metal grid at the front and back, with more than 95% of both sides available to capture light.

Bifacial panels are installed in standard PV power plants, but also in emerging market segments. Think of PV integrated into the infrastructure, such as in noise barriers. Or floating solar panels on open water or in combined hydro and aquaculture farms.

Another application is in combination with solar tracking systems, where you can virtually add up the additional yield of the solar tracking system and the bifacial panels. This last option also offers many possibilities to vary the irradiation under and between the panels. Ideal for agriculture or nature conservation.

Higher energy yield with bifacial solar panels

We design and develop bifacial modules that meet specific requirements, for example by reducing the amount of silver in the panels to optimise costs and performance under reduced light conditions. We are also working on the application of light-capturing materials to improve light coupling in and on modules. In addition, we are looking for solutions for cell and bypass diode positioning to take into account increased shading due to robust frames, for example in the case of noise barriers.

We have also developed a new bifacial solar panel with a white layer around the cells. These white, bifacial solar panels generate 5% more energy compared to partially transparent bifacial panels with only transparent glass and plastic layers around the cells. The yield of the white bifacial panels compared to single-sided panels depends on the location of the installation and can be about 10 to 20% higher.

bifacial-module-3
Bifacial modules capture light from all directions.
Transcription

2 bifacial solar modules, consisting of encapsulated solar cells between 2 glass panels. The tilted bifacial module receives direct sunlight on its front side and ground-reflected light, from the grass below the module, on its back side. The vertical bifacial modules can receive direct sunlight on either side depending on the position of the sun and will receive reflected light, from the grass below the modules, on both sides.

Predicting energy yield with BIGEYE

We developed BIGEYE in order to make an accurate prediction of the energy yield of a PV system with bifacial modules for all parties. This is a very advanced, and as far as we know the most complete, simulation model for a PV system. With BIGEYE, we can simulate the electricity output of PV systems with any configuration and at any location. With meteorological and environmental data, we calculate the electricity production per hour, day, month or year.

For PV installers, project developers, and system owners, it is very valuable to have a precise energy generation profile. This allows them to provide optimal connections to the local, national, and global electricity grid. In addition, BIGEYE helps to design PV systems in such a way that power generation better matches daily needs. For example, by increasing energy generation in the morning or afternoon.

Knowledge and technology

Our experts are working on various new cell concepts with the aim of increasing efficiency and simultaneously reducing manufacturing costs. One of the bifacial cell concepts we have developed is an industrial version of the so-called TOPCon solar cell. This cell has special intermediate layers on the back, consisting of a very thin oxide and polysilicon layer. This structure counteracts the losses on the surface. We developed this cell concept in collaboration with Tempress Systems, among others, under a TKI Urban Energy grant project and in several commercial projects. This technology has now been embraced by the industry and cell efficiencies of over 23% are being achieved in production.

In one of the latest bifacial cell concepts, very thin metal oxides are incorporated in the interface layers. These interface layers can be applied on both sides and have the same quality as those in the TOPCon cell, but they are much more transparent, allowing sunlight to enter the solar cell optimally. The bifacial performance of the solar cell can therefore be improved considerably, while production is potentially simpler and therefore cheaper. This concept is still under development in collaboration with Solmates, Levitech, Eindhoven University of Technology, and Delft University of Technology. We expect that with this technology, inexpensive solar cells can be produced with more than 25% efficiency.

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