1.1 Research Background and Examples of Plant Cultivation Systems Using Sustainable Energy
Shortly, the food crisis due to worldwide population growth and rising food prices is anticipated, and people will have to become more self-sufficient. Besides, the agricultural working population in Japan is dropping sharply and mostly consists of elderly people. Climate change also poses a threat to the cultivation of crops. A hydroponic system allows the effective use of sustainable energy, making it possible to grow plants without being significantly affected by the natural environment. Large hydroponic systems called plant factories have been developed in the past (Holz, et. al., 2015; Zhang, et. al., 2018; Kozai, 2013). Relatively small hydroponic systems for farmers have also been developed (George, et. al., 2017; Yoshiga, et. al., 2016; Palande, et. al., 2018). In any case, hydroponic systems are likely to be operated using sustainable energy in the future (Fathabadi, et. al., 2017; Rekioua, et. al., 2014; Yunez-Cano, et. al., 2016). Compact, low-cost, tabletop hydroponic systems have been developed to grow vegetables inside or outside homes (Yamaguchi, et. al., 2018). Self-sufficient energy systems that use sustainable energy sources such as solar power have also been designed.
In recent years, solar sharing, where plants are grown under solar panels, has also attracted attention (Sekiyama, et. al., 2019). Agrivoltaics (the combination of using land for agricultural and electric energy production via photovoltaics) is attracting worldwide interest as a solution to the recent increase in energy and food demand (Sekiyama, et. al., 2019; Nozu, 2018; Kamada, 2019). The first solar sharing system was proposed (Goetzberger, et. al., 1982), and various types of Agrivoltaic systems have been studied (Prannay, et. al., 2017; Othman, et. al., 2018). Photovoltaic power generation is also attracting attention as alternative energy that replaces fossil fuels (Scognamiglio, 2016; Dupraz, et. al., 2011; Dinesh, et. al., 2016).
From these studies, it is expected that the demand for plant cultivation systems that can utilize sustainable energy will increase regardless of scale. Systems that combine sustainable energy sources such as wind and solar power are expected.