Israel-made solar energy cells produce power while keeping land farmable

Hebrew University of Jerusalem researchers develop selective solar energy cells that produce green electricity while allowing agricultural cultivation of the ground below.

 The transparent red square is a newly created solar cell that lets light access plants while storing excess any energy for use as electricity. (photo credit: Prof. Lioz Etgar)
The transparent red square is a newly created solar cell that lets light access plants while storing excess any energy for use as electricity.
(photo credit: Prof. Lioz Etgar)

Fields, greenhouses and orchards are devoted to farming, yet photovoltaic (PV) cells need their own land to produce electricity from the sun. It was thought that the two couldn’t mix.

Now, a collaboration between Prof. Haim Rabinowitch of the Smith Faculty of Agriculture, Food and Environment and Prof. Lioz Etgar of the Institute of Chemistry at the Hebrew University of Jerusalem, has produced a prototype for a new PV cell. The new cell’s efficiency has been technologically proven and its performance stands to dramatically change the rules of the game regarding solar energy and agricultural production.

The innovative solar cell is designed to fully cover agricultural areas including greenhouses, orchards, fields and water bodies while simultaneously generating green electricity and agricultural production, without interruption of natural habitats under the PV panels, without using up natural resources, and without harming the environment.

Can this help reduce the price of energy in Israel?

According to the team, this innovation will reduce the cost of energy in Israel by 75%. In fact, they believe that covering half of the greenhouses in Israel with these new cells would result in green electricity production exceeding Israel’s national target for 2050.

The new solar cells are based on crystals of perovskite, a calcium titanium oxide mineral that was first discovered in 1839 and is relatively easy to process with cheap and easily obtainable materials.

  A 55-MEGAWATT solar power plant in Israel's south.  (credit: MOSHE SHAI/FLASH90) A 55-MEGAWATT solar power plant in Israel's south. (credit: MOSHE SHAI/FLASH90)

A chemical substitution makes the solar cells transparent to the most efficient area of the light spectrum that drives photosynthesis. A great part of the rest of the light energy is transformed into electricity.

“For years, it has been obvious that most light energy in agricultural greenhouses is wasted, as plants use only a fraction of the sunlight energy, while the rest is radiated back into the atmosphere. In greenhouses, it becomes heat energy, that growers need to get rid of during most months of the year.”

Prof. Lioz Etgar

“For years, it has been obvious that most light energy in agricultural greenhouses is wasted, as plants use only a fraction of the sunlight energy, while the rest is radiated back into the atmosphere,” Etgar explained. “In greenhouses, it becomes heat energy that growers need to get rid of during most months of the year. Our solution maximizes the production of solar electricity on agricultural land by up to 300%.”

The new cells are expected to have much lower production costs than silicon-based photovoltaic cells. They will likely also significantly improve cultivation conditions in greenhouses by reducing heat, lowering greenhouse gas emissions and evapotranspiration, saving water and protecting crops from weather damage.

ALL EXISTING technologies for the generation of green power on agricultural lands deploy silicon-based photovoltaic cells that are either fully opaque or only partially transparent to most of the light spectrum or laid in alternative arrays. This results in lower efficiency of power generation and concomitantly reduced agricultural production.

Rabinowitch added, “This new development, which can be installed over any agricultural lands and any bodies of water, will make it possible to fully replace the roofs of most agricultural greenhouses, reduce heat levels and evapotranspiration in orchards and fields, and impairment of many fresh-water and coastal marine ecosystems on which rafts or islands of solar cells are installed.”

Calculations based on current data indicate that the use of these new cells will lower agricultural costs and increase agricultural income and profitability. This is nothing less than a revolution, the researchers declared.

“Israel has a total of around 90,000 dunams [approximately 35 square miles] of greenhouses. Covering half of the greenhouse roofs with the new solar cells will provide a quantity of green electricity that enables Israel to exceed its 2050 national targets for green electricity production and carbon emission reduction. To give a greater idea of the economic potential of this development, the Mediterranean basin alone holds around two million dunams (770 sq.mi.) of greenhouses.

A study published in 2018 in the UN’s Global Food Security report showed that the value of vegetable cultivation comprises around 30% of the overall value of all crops, or around $1.85 billion. The process of photosynthesis with which all crops are grown uses about 10% of the total available light energy from the sun. Thus, it was only a matter of time before groundbreaking creative research would come up with a far more efficient solution for the combined production of electricity and agricultural produce, utilizing the remaining 90% of solar energy that is not used in photosynthesis.

The idea developed by Rabinowitch and Etgar and their research colleagues was assessed by the Israel Innovation Authority, which provided a generous research grant. The proven results of this research were promoted by the Hebrew University’s technology-transfer company Yissum and formed the basis for partnership with the Red Solar Flower initiative led by Dr. Shai Danziger and Ilan Sharon. The successful research project to develop the solar cells, along with the Yissum-Red Solar Flower partnership, were recently awarded first place in the Energy Tech Challenge, led by the Digital SolarEdge company, as part of the Climate Solutions Prize organized by Start-Up Nation Central.