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Farmers Cultivate Crops and Solar Energy

Japan Next-Generation Farmers Cultivate Crops and Solar Energy

Junko Movellan, Correspondent
October 10, 2013

San Diego, Calif. -- Farmers in Japan can now generate solar electricity while growing crops on the same farmland. In April, the Ministry of Agriculture, Forestry and Fisheries (MAFF) approved installation of PV systems on existing, crop-producing farmland. Previously solar generation on farmland, productive or idle, was prohibited under the Agricultural Land Act.

This co-existence or double-generation is known as “Solar Sharing” in Japan. The concept was originally developed by Akira Nagashima in 2004, who was a retired agricultural machinery engineer who later studied biology and learned the “light saturation point.” The rate of photosynthesis increases as the irradiance level is increased; however at one point, any further increase in the amount of light that strikes the plant does not cause any increase to the rate of photosynthesis.

By knowing that too much sun won’t help further growth of plants, Nagashima came up with the idea to combine PV systems and farming. He devised and originally patented special structure, which is much like a pergola in a garden. He created a couple of testing fields with different shading rates and different crops. The structures he created are made of pipes and rows of PV panels, which are arranged with certain intervals to allow enough sunlight to hit the ground for photosynthesis (Figure 1).

Figure 1: Photo of Solar Sharing Field Test via Akira Nagashima

At first glance, the structure may seem to be rather “skimpy.” One of reasons is the MAFA requires that PV systems have a simple structure (without concrete footings) and should be easily dismantled. MAFA also requires that PV mounting structures must be designed and built to secure adequate sunlight for crops and space for agricultural machinery to be able to move around.

However, Nagashima said that the point of these guidelines are for farmers to remain “farming” and prevent farmers from fully converting productive farmland to solar facilities. Based on the tests conducted at his solar testing sites in Chiba Prefecture, he recommends about 32% shading rate for a farmland space to reach adequate growth of crops. In other words, there is twice as much empty space for each PV module installed. To ensure continuous farming, municipal agricultural committees require farmers to report annual amounts of cultivation and demand to take down the PV system from the land if the amount of crops cultivated on the solar shared farmland gets reduced by more than 20%, compared to the pre-PV installation.

Gage comment: If the 32% figure is correct, rows of solar PV panels using two 1.6m panels per metre would need to be at least 8.5m apart to avoid any noticeable reduction in growth of vegetables or crops below the panels. This assumes the panels are angled at the optimum (for the UK) slope of 35 degrees to the horizontal (hypotenuse 3.3m, height from ground or base support is 19m and horizontal length is 2.7m) – each row requires 2.7m + the spacing of 8.5m for 11.2m. This is similar to the spacing in most UK solarfarms when laid on flat ground. While this system may not be ideal for large exposed solarfarms (exposed to view and wind), it would be ideal for small fields where vegetables are grown or for allotments where the electricity generated could be used by nearby houses. An allotment size in the UK is 1/16th of an acre or 0.025 of a hectare (250 sq m).

“The solar sharing can re-activate the declining farming sector,” said Makoto Takazawa, the owner of the 34.4-kW Kazusatsurumai Solar Sharing Project (Figure 2) in Chiba Prefecture. This is the first project in the nation to take advantage of the FIT scheme. Farmers in Japan are facing serious issues such as reduction in farming revenues and subsequently lack of successors. Many small farmers are forced to get a second job to sustain their living. Takazawa learned the concept from Nagashima and found that the solar shared farming is a way to revitalize Japanese farmers, providing opportunities to increase income and contribute to the nation’s energy need.

Figure 2: Photo of the Kazusatsurumai Solar Sharing Project via Makoto Takazawa

Takazawa installed 348 PV panels on a small 750 square-meter of farmland. PV panels are installed on pipes, which are 3-meter high from the ground. Rows of PV panels are installed every 5 meters. Under the PV system, Takasawa’s father has been cultivating peanuts, yams, eggplants, cucumbers, tomatoes, and taros (Figure 3) and will cultivate cabbages during the winter. These vegetables are sold at a nearby street and consumed by his neighbors.

Gage’s comment: 750 sq m equates to three allotments each of 250 sq m. Each allotment could therefore provide the site for 1/3rd of Takazawa’s 34.4kWp for about 10kWp. In Cornwall, this should generate about 10,000 kWh per year for the allotment owner. With a current FIT of 13.5p/kWh and an assumption that 50% is exported at 4.64p/kWh, this will generate a revenue of £1,800 for each allotment owner. This would be increased if his/her string of solar PV panels could be fed to a house where the other 50% of the electricity generated could be used saving the daytime tariff of 18p/kWh for a further benefit of £900/yr.

The total benefit per allotment plot owner would then increase to £2,700 per year RPI linked for 20 years. As this is tax free, for a basic rate taxpayer (20%) when grossed up this would be worth £3,375 in Year 1. 10kWp of solar PV with the ground-mountings shown above might cost £12,000 per allotment for a Year 1 ROI for a basic rate taxpayer of 28% with a payback within four years. If the electricity cannot be used, the grossed up benefit for a basic rate taxpayer would be £2,250 in Year 1 for an ROI of 18% and payback if inflation runs at 3% pa in less than five years.

The cost of the system producing 35,000 kWh annually cost Takazawa about ¥12.6 million ($126,000). Having secured the first available FIT rate of ¥42/kWh for 2 years, he will earn ¥1.6 million (~$16,000) annually while only making ¥100,000 (~$1,000) annually from farming. Like him, “Countryside has a potential to create clean energy, thereby stimulating local economy. I hope this (the FIT revenue) will attract young people to come back to the countryside,” said Takizawa.

Figure 3: Photo of the Kazusatsurumai Solar Sharing Project via Makoto Takazawa

In Aichi Prefecture, Tsuboi has designed and self-built a 50-kW system over the growing citrus trees. About 600 PV panels are installed over 7.7 acres of the farmland are mounted on 5-meter high steel pipes. The type of citrus he is growing is called Dekobon, a Japanese hybrid of mandarin and orange. Since Dekobons are harvested under the PV system, he is selling them under the name “Solarbon.” Like many other farmers, Tsuboi also has another job besides farming. This year, he expects the PV system to bring ¥2.5 million (~$25,000) as an additional income.

Many have questioned stability and durability of the PV structure for solar shared family. Nagashima stated that his systems, which are made of thin pipes without concrete footings, even withstood strong winds and earthquakes during the Fukushima Tsunami disasters in 2011. These systems are extremely lightweight and installation of PV panels are spaced out, allowing air to flow through between the panels. This will eliminate concern that the panels will receive wind load and be blown away, therefore, reducing the need for complicated and expensive mounting hardware.

Nagashima suggests solar-shared farming for ranches in the U.S. He pointed out a few benefits of PV systems over grass on pasture: the PV system can provide shade for cattle or sheep to rest underneath and because of higher soil moisture level, the shading will reduce irrigation expenses.

For Japan, it will require about 2.5 million acres of land to supply Japan’s total electricity with PV. Under the solar shared family, it will take about 7 million acres of farmland to supply the same amount of electricity. Japan currently has over 11.3 million acres of available farmland. “Before the Industrial Revolutions, farmers provided both crops and energy (firewood and charcoal) to the society. The solar-shared farming makes again for farmers to provide two important products from nature and will revitalize the farming sector,” Nagashima stated.

Gage’s comment: The coalition government is under pressure from a vociferous minority to ban the deployment of ground-mounted solar PV on farmland on the grounds that it might take land away from food production. We already know that sheep thrive in solar farms where if the spacing is adequate. This paper shows there is no loss of CV in the grass. Indeed, farmers tell me that the micro-climate within a solar farm where there is less wind-chill, frost and dew results in better grass growth than before the solar panels were installed.

My proposal to use this system for market gardening and village allotments, especially where there are houses nearby that could make use of the electricity generated, needs to be given support. Increasing the annual RPI linked yield of a single allotment plot measuring 25m x 10m by a grossed up amount in Year 1 of £3,375 will not only go some way to alleviate rural poverty but also encourage villages to find suitable sites for allotments. More vegetables will be grown locally, food miles reduced and, best of all, community spirit will be invigorated as there is no better place to get to know your neighbours than sharing an allotment.

Truro Diocese owns over 2,500 acres of glebe land most of which is scattered amongst Cornwall's 208 rural parishes. There are long waiting lists for sites in allotments, but not many villages have allotments. This proposal could greatly increase demand for land to be taken out of grazing and converted to village allotments. The glebe was land that used to belong to the village incumbent priest and hence is nearly always close to the vicarage/rectory and therefore close to the village itself - ideal for an allotment.

The diocese would increase its rent from its glebe while enabling parishioners to benefit not just from growing their own vegetables but also from the renewable energy that they can generate at the same time. At £100 rent per 250 sq m plot, the rent would jump from about £100 per acre of grazing to £1,600 per acre. If five acres per rural parish could be made over, this would amount to about 1,000 acres and increase the rent from the diocesan glebe by £1.5 million per year. Five acres would be sufficient for 100 plots per village. Harvest festival will no longer just be a celebration by the parish farmers but by the entire community as it used to be when a village turned out to help with the harvest.

Each 250 sq m allotment plot should be able to generate 10,000 kWh per year sufficient across a year for three median households. 20,000 plots across Cornwall would generate 20,000 MWh per year sufficient for about 60,000 homes or 24% of Cornwall's 250,000 households.

Parishes should include provision for an allotment or allotments in their community plans.

Gage Williams