Research on the feasibility of placing transparent solar panels on the roof of greenhouses shows that the application is still limited. Inno-Agro reached this conclusion after their research was conducted. There are however other possible locations for the placement of the panels, among which are technical and processing areas, corridors and sales buffers, as Joël van Staalduinen writes in 'Kas als Energiebron'.
The application of (transparent) solar panels on greenhouse roofs needs to provide added value for the company. If the only added value is the generating of sustainable energy, the roof of the shed will be supplied with regular solar panels first, after which the technical rooms and corridors will follow.
Save on the screen cloths or outdoor screens
Applying the solar panels above a sales buffer, sorting system or processing area can provide the needed added value. Besides keeping out the light, warmth is also kept out and because of that, the investment that would be made when buying screen cloths or outdoor screens is no longer needed.
When applying to the roof of a greenhouse, lighting becomes a necessity for growing in the winter. The disadvantage of the solar panels is that they remain on the roof year-round and thus don’t provide flexibility when it comes to light transmission — something the screens do provide.
Specific situation
The different PV-technologies (photovoltaic) and mounting systems all have their pros and cons, that can make or break the application of the panels in particular situations. Genuine transparent panels are still quite expensive per m² and provide a relatively low financial return. Because of this, they do not form much of a competition yet.
Glass/glass crystalline panels are used by many greenhouse builders and are a good option for new buildings to have.
The efficiency and the price/kWh is very fair compared to standard panels because the most volume and development takes place in these. However, in all cases, the greenhouse construction is burdened more, which can have constructive consequences.
Flexible panels
The flexibility of flexible panels is not only due to the material they are made of, but also their applicability. The panels are light in terms of weight, can be ordered customized to fit, after which they can easily be placed on and have a very favorable price/kWh. This makes flexible panels a fascinating technique to be used in the near future. Besides the roof of the greenhouses, they can also be placed on heat storage tanks and sandwich panels.
Measuring panels in follow-up research
According to the researchers, it is still impossible to reach a general conclusion. There are many company-specific variables that influence the feasibility. The final report offers some guidelines for deciding whether (transparent) solar panels are an exciting option in a given situation and clarifies specific key points that need to be kept in mind throughout the process.
In a follow-up project, the Wageningen University & Research business unit Greenhouse Horticulture measures the light transmittance and insulation value of a variety of materials. Based on those measurements, the effects on production, energy usage and -yield are determined for several example crops with as its goal to determine the feasibility for the Dutch greenhouse horticulture.