Researchers from North Carolina State University found that greenhouses could become energy neutral with see-through solar panels to harvest energy. The solar panels gather energy from wavelengths of light that plants don’t use during photosynthesis. The transparent solar panels allow most of the photosynthetic band light to pass through and reach the plants while using other light waves to gather energy. Most energy use in greenhouses comes from heating and cooling.
The team used organic solar cells because they allowed researchers to tune the spectrum of light that the solar cells absorb. The team used a computational model to estimate how much energy a greenhouse could create with this method. They also used the model to find if the amount of energy produced would be enough to operate the greenhouse.
To test the model, it was tasked with estimating energy use for greenhouses growing tomatoes in Arizona, North Carolina and Wisconsin. The model calculated the energy load needed to maintain the optimal temperature range for tomato growth.
There is a trade-off between the amount of power solar cells can generate and the amount of light that the photosynthetic band allows to pass. If growers are willing to sacrifice larger amounts of photosynthetic growth, the more power they can generate. The solar cells used in this study can keep the greenhouses cool in the summer and warm in the winter.
The tradeoff is very small for most greenhouse operators, particularly in warm climates. In Arizona, greenhouses could become energy neutral while blocking only 10% of the photosynthetic band of light. If growers are willing to sacrifice some photosynthetic light, they could generate two times the amount of energy they need to operate. The impact of using some photosynthetic light on plants is small.
A paper on this study was published in Joule.