Related material: the project, press coverage and the collaborators behind the technology.
What the crop sees
Plants do not use the solar spectrum evenly. Photosynthesis draws mostly on the blue and red bands, leaving other wavelengths comparatively idle from the plant's point of view. That unevenness is the opening semi-transparent photovoltaics work in.
A cell tuned to absorb where the crop is least sensitive takes energy the plant was not going to use. The result is not free — some loss is unavoidable — but it is far smaller than the shading an opaque panel of the same area would cast.
Light, split two ways
Every square metre of greenhouse roof receives more solar energy than the crop beneath it can use. Photosynthesis draws mainly on the blue and red bands; a large part of the spectrum passes through and warms the structure without feeding anything. Semi-transparent photovoltaics work in that gap.
The design question is where to draw the line. Absorb too much and the plants notice; absorb too little and the electrical yield does not repay the glass. The answer differs by crop and by latitude, which is why installations are specified per project rather than sold as a single product.