Swedish research team "Growing broccoli under translucent panels... the weight of flower buds is similar to that of open field"

Swedish research team "Growing broccoli under translucent panels... the weight of flower buds is similar to that of open field"

(Seoul = Yonhap News) Reporter Jooyoung Lee = The number of solar power complexes is rapidly increasing around the world due to policies to expand new and renewable energy. Is it possible to grow crops efficiently under this rapidly increasing number of solar panels?

In an experiment growing broccoli under magenta translucent solar panels that selectively pass light of the wavelength necessary for photosynthesis, results were obtained that broccoli production could be maintained at the level of outdoor cultivation even with reduced sunlight while generating electricity.

Dr. Sylvia Maru's team at Malardalen University in Sweden announced on the 3rd in the scientific journal Cell Reports Physical Science that they had confirmed the possibility of producing electricity while securing a yield similar to that of outdoor cultivation by growing broccoli under magenta translucent cadmium telluride (CdTe) solar panels.

Dr. Maru said, "Solar panels use part of the incoming sunlight to produce electricity, while some of the light passes through to crops growing below. In the future, we will investigate whether we can use sunlight more efficiently by allocating different parts of the solar spectrum to crop growth and electricity production respectively."

Recently, as solar power generation has increased due to policies to expand new and renewable energy to respond to climate change, how to efficiently use the land needed for food production and solar power generation has become an important task.

As a countermeasure to this, agricultural solar power generation, which combines power generation and crop cultivation, is being studied, but existing agricultural solar power has the limitation of reducing agricultural productivity by reducing the light reaching the crops due to opaque panels.

To solve this problem, the research team manufactured a solar panel with magenta translucency taking into account blue and red light. Photosynthesis in plants mainly uses light of 400 to 700 nanometers, and chlorophyll absorbs a relatively large amount of blue and red light.

The research team produced magenta translucent panels with photosynthetic effective radiation transmittance of 13.2% (transparency 50%) and 19.2% (transparency 70%). Next, we installed a solar power system with two panels each measuring 20 m2, grew broccoli under them, and compared this with open field cultivation.

As a result, broccoli grown in the open field matured 79 days after transplanting, but broccoli under two solar panels matured only after 104 days, delaying harvest by 25 days.

However, the weight of flower buds at harvest was 168.5g on average on the 70% transparency panel and 173.7g on the 50% transparency panel, which was not statistically significantly different from the 187.6g of open field cultivation. In particular, broccoli under solar panels received much less light than in the open field, but its light use efficiency was found to be much higher than in the open field. The radiant energy use efficiency (RUE) was 4.5 times that of the open field for the 50% transparent panel and 2.8 times that for the 70% transparent panel.

In addition, it is estimated that solar power generation will be generated at the same time as broccoli cultivation, and that the 50% transparent magenta CdTe panel will be able to produce approximately 447.6 kilowatt hours (kWh) of electricity during the cultivation period. The photoelectric conversion efficiency, which converts sunlight into electricity, was 7.2%.

The research team explained that if the area was expanded to 1 ha and assuming that 40% of the total area could not be cultivated due to solar structures, etc., the land use efficiency was calculated and the land equivalent ratio (LER) was found to be 1.18.

This means that land use efficiency can theoretically increase by about 18% if agriculture and solar power generation are produced together on one land rather than each on separate lands.

The research team said that this study was a proof of concept conducted during one growing season in central Sweden, and that the results cannot be directly applied to other climates and crops. For actual application, additional verification is needed in various climates, crops, and various growing periods and systems.