History

Solar sharing was proposed in 2003 by Akira Nagashima, who turned his attention to the fact that most plants do not need all sunshine they receive in an open field. Plant photosynthesis depends on light – increased amount of light leads to higher photosynthesis rate – but only to a certain point. The amount of light beyond this saturation point not only doesn’t contribute to photosynthesis, but can even be harmful.

Based on this fact, Nagashima devised a system where solar panels use the excessive sunlight for energy generation while crops are cultivated below them. Nagashima applied for a patent in 2004 and made the technology freely available in 2005 (Patent publication No. 2005-277038).

Many trial projects have been launched since then, especially in the past two years. After the March 2011 East Japan earthquake and tsunami , followed by meltdowns at Fukushima Daiichi Nuclear Power Plant, Japan revised its energy policy and introduced feed-in tariff system to promote diffusion of renewable energy. Electric power companies now must buy energy from renewable sources for fixed prices.

On March 31, 2013, Ministry of Agriculture, Forestry and Fisheries issued a guideline, acknowledging solar sharing system and setting rules for farmers who want to introduce it on land registered as agricultural. This was the first time that Japanese government recognized the already existing technology.