I moved this blog to another site.
(Japanese article is here.)
On July 6, 2014, I went to Smart Life Power Plant, a newly built solar sharing power plant in the town of Izunokuni, Shizuoka prefecture.
It takes about 3 hours to get there by train from my place in Tsukuba, Ibaraki prefecture. A small one-day trip.
I finally got off at a small station on Izuhakone railway line. The power plant should be 2.3 km from the station, so I decided go on foot. After some 30 minutes of walking, the power plant came into view:
I received materials at the registration desk and went in, and there I could see Mr. Iwahori from Hatsudenman - the company that constructed the plant - already absorbed in conversation with visitors. It's the group in the middle of the picture, standing on the border between rice field and taro potato field.
1. It's big!
2. It's not dark despite higher shading rate
The shading rate is 38 %, which is somewhat higher than recommended level in solar sharing (up to 32 %), but it didn't feel particularly dark. Obviously this is due to the fact that sunlight comes not only from above, but also from the sides. Rice and taro potatoes under the panels were growing well.
As for myself, I wouldn't raise the shading rate that high, but my frank impression was that the field was surprisingly bright even at shading rate as high as 38%.
Next we just have to wait for the harvest and see whether the yield is lower, and if yes, how much. (Ministry of Agriculture guidelines stipulate that the yield cannot drop by more than 20%)
The special feature of this power plant is that it is built over land that is registered as “farmland.” If you want to do solar sharing on farmland in Japan, you need permission from local agricultural committee. This is a substantial challenge to overcome.
This was the first time I saw solar panels generating electricity installed over a rice field. Solar sharing on a rice field is still rare in Japan.
It felt strange to see metal pipes (that support the construction) rise out of the water, because rice field is covered in water. Here’s how it looks like:
I hope the crops - both rice and taro potatoes - at the Smart Life Power Plant will keep doing well. From time to time I might ask Hatsudenman for an update!
Absolutely unrelated postscript:
This has absolutely nothing to do with the power plant I visited, but I can’t help not mentioning it. When I walked from the station to the site, I again realized how bad walkability in Japan is. At one point the sidewalk simply disappeared and I had to walk on the road along the cars. It could have been such a nice walk otherwise. In Japan car drivers are first-class citizens, pedestrians are second-class. It's not easy to get used to it. Japan would be so much nicer place to live were there more sidewalks around.
Nishigoya Solar Power Plant of Ken Matsuoka began operation on October 15, 2013. The opening ceremony was held soon after - on Sunday October 27.
It was the sunniest Sunday you could wish for an event at a solar power plant.
Matsuoka started his address with self-introduction: "I'm Ken Matsuoka, chief of Nishigoya Solar Power Plant."
He laughed and the audience too. "Power plant chief" was an exact description of his role in the project, and yet the words somehow sounded too big. Not many people can introduce themselves as power plant chiefs. Not many people know someone who'd be a power plant chief. I was proud to be one of them.
Among the guests there were family members and friends who volunteered their time to help build the plant, and also some VIPs - like the father of solar sharing Akira Nagashima and Japan's ex-prime minister Naoto Kan.
Here at the ceremony I heard for the first time the story of how it all began a year and a half ago:
By a series of coincidences, Ken Matsuoka happened to visit the Naoto Kan's office as a technical support for an interview. During the interview, Mr. Kan showed them materials on his desk: "Look at these amazing renewable energy projects."
On the desk, Matsuoka saw a photo of solar sharing. "I just found what I want to do," he allegedly murmured.
Next day he contacted Akira Nagashima.
About the plant:
Matsuoka's plant consists of 579 panels (100W/panel) installed on a metal frame at the height 3.5 meters over an area of about 1500 m2. The plant's capacity - maximum output to sell to electric utility - is 49.9 kW.
A special feature of Matsuoka's plant is a winch allowing to change the tilt of all 579 panels (more than 8 tons) at once. The device, according to Matsuoka, didn't cost more than 1 % of the total investment, but it could increase the output by about 5 % - that is a significant number over 20 years.
We could see the effect of the winch at the ceremony.
On October 23, 2013, I met Akira Nagashima at his Solar Sharing Trial Site (ソーラーシェアリング実証試験場) in Chiba prefecture.
Akira Nagashima, the inventor of solar sharing, is a celebrity in the community of solar sharing enthusiasts.
There are two plants on his trial site, both connected to public grid. Each has an output of about 4.5 kilowatts. There are many solar sharing projects in Japan, but this site is special because it's the first one. All others are imitations of this one.
Plant No. 1 (一号機) is installed above the garden. On the picture you can see peanuts, carrot, leek, taro and a row of unindentified leaves growing under the panels. Nagashima is standing on the side.
Plant No. 2 （2号機） is installed above a parking lot. Nagashima is standing below with a customized module that just arrived from manufacturer.
It still feels strange to call this kind of solar installation a power plant. For too long time we used to think of power plants as big unsightly buildings somewhere faraway.
Definition: Power plant is a complex of structures and equipment for generating electric energy from another source of energy.
Solar panels on the pictures above generate electricity from sun - they are legitimate power plants.
Monstrous appearance we expect from power plants is, luckily, optional. Solar sharing plants so far unticked this option - they're neither big nor ugly nor remote.
The idea of solar sharing first popped up in Nagashima's mind 10 years ago - in late 2003. Nagashima, now 70, was then studying law at Keio University in Tokyo (yes, at the age of 60). Nagashima got a biology textbook in his law course.
Why would one need a biology book in a law course?
Good question. I forgot to ask.
In that biology book, Nagashima came across the concept of light saturation point.
Light saturation point: Plants need sun to perform photosynthesis. We tend to believe that the more sunshine plants get the better, but this is not true for most plants. The reason is that most plants have a light saturation point - the amount of light intensity beyond which photosynthesis rate doesn't increase. All light beyond this saturation point is not only useless, but can even be stressful to the plant (for example causing overheating and water evaporation)
The concept of light saturation point led to Nagashima's eureka moment: If plants don't need all sunshine they're getting, why don't we use the excessive rays for power generation? Instead of laying solar moduls directly on the ground, we can put them a few meters higher and with spaces in between, so that plants below can still get their share of sun and keep growing.
The idea was out there and the time was ready for the next step: work out details and give it a real, tangible shape.
And a name.
Solar Sharing Trial Site was established in May 2010. Plant No. 1 started operation in August 2010 and plant No. 2 in April 2011. This was the only solar sharing project in Japan at that time.
How much can solar sharing contribute to Japan’s energy self-sufficiency?
There are two basic indicators to describe the potential of an energy source:
1. Installed capacity
2. Estimated annual energy production
1. Installed capacity
Installed capacity (発電設備容量) is the maximum amount of electricity that can be produced by a facility at a given time. It is measured in watts （or kilowatts or megawatts...).
Example: If you install ten solar panels on your roof, each panel with 100 watt nameplate capacity, then the installed capacity of your roof-top solar plant will be 10 x 100 = 1000 watts, or 1kilowatt. Under perfect conditions (full sunshine, the right angle), your panels can produce maximum of 1000 watts of electricity.
If solar sharing was adopted on 15 % of Japan’s farmland (4,549,000 ha in 2012) at a shading rate 25%, the total installed capacity would be as much as 270 million kilowatts.
270 million kilowatts is a lot of electricity. It is more than the peak demand in Japan in 2012 , which was about 156 million kilowatts. Peak demand in today's Japan occurs on very hot summer days when everyone turns on air-conditioning (Only In Hokkaido and Tohoku the peak demand occurs in winter due to heating).
As hot summer days are also sunny days when solar panels work at their maximum, solar sharing could greatly contribute to energy supply in the summer peak demand.
Installed capacity, while an important indicator, can be a bit tricky though. No power plant generates electricity at maximum installed capacity all the time - either due to maintenance needs or lack of demand or - especially in case of renewables - because of the lack of “fuel”. The fuel for solar power is the sun. Solar panels on your roof produce nothing at night, and little on cloudy days.
That's why we need the second indicator:
2. Estimated annual energy production
Annual energy production （年間可能発電電力量）shows how much electricity over a given period of time the facility can actually produce. The measurement unit is kilowatt hour.
Estimated annual energy production is calculated as:
installed capacity x capacity factor x 365 days x 24 hours
Capacity factor (設備利用率) is the ratio of the actual output over a period of time to the potential maximum output. If ten solar panels on your roof produced electricity only for six sunny hours on a day, their capacity factor for that day would be 25% (6hours/24hours*100). (A bit simplified.)
Capacity factor differs for each type of energy. It is typically high and stable for nuclear and thermal plants – as much as 70 to 90 %, but lower for renewables because they depend on the availability of sun or wind or water.
Actual capacity factor of solar panel installations in Japan in 2012 (average of 12 months from April 2012 to March 2013) was 15%.
Taking into account this capacity factor, how much energy could solar panels installed on 15% of Japan's farmland actually produce? The answer is: as much as 358 million megawatt hours of electricity yearly. This is about 40 % of Japan’s total electricity demand in 2012. Not so bad.
Who knows what Japan's energy infrastructure will look like in ten years. Solar sharing might be a vital part of it.
Tsukuba is a city about 60 km northeast of Tokyo. One of the solar sharing pioneers Ken Matsuoka launched his project there in fall 2012.
He installed 579 solar panels on a metal frame over land area of about 1500m2.
The construction - from clearing the land and building metal frame to setting panels and cables, all based on Matsuoka's design and done DIY way - took him almost a year. Everything got ready in September 2013.
As of today October 14, 2013, the site is on a test run. Actual selling of electricity to the grid is scheduled to start tomorrow – on October 15, 2013.
Matsuoka will sell maximum of 49.9 kW to Tokyo Electric Power Company for the fixed price of 42 JPY/kWh, guaranteed for 20 years.
Matsuoka also introduced manual tilting system to regulate the amount of light that can reach either the panels or the ground. He can now turn panels with a total weight of more than 8 tons using a single winch. Shading rate is 25.5 % (at panel tilt 0°). The purpose of tilting is not necessarily to maximize power generation output but quite the contrary, it can be used to provide more sunshine to crops when necessary, e.g. at critical growth stages like budding.
Matsuoka adjusting panel tilt:
Matsuoka is not a professional farmer but he does have experience growing his own food. He is now producing soybeans, tomatoes, eggplants and other crops for personal consumption under the panels. The site is registered as miscellaneous land - meaning Matsuoka has to pay higher taxes compared to agricultural land, but he has more freedom to choose how to use the land, what to grow and at what quantities. When we spoke last time, Matsuoka was envisioning a rice field on one part of the land, and a community garden on another. Both are great ideas because there are few on-site trials of growing rice under solar panels, and a community garden with many people coming and growing their vegetables just sounds good. Let's see what will eventually become reality.
The best thing about solar sharing is that building and running a power plant is not anymore something that only big power companies can do. Both technologically and financially, the hurdle is now low enough so that almost anyone can build their own small solar power plant and grow food below it. This will undoubtedly change our way of thinking about electricity.
Link to Ken Matsuoka's blog (Japanese):
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.
Why is solar sharing so revolutionary?
An oft-cited drawback of solar power generation is the requirement of a vast surface area. If solar panels are to produce the amount of electricity comparable with nuclear or thermal power plants, the rooftops alone will not suffice. All over the world, low quality land as well as farmland has been used for large scale solar power development.
However, paving agricultural land with solar panels has drawn criticism for curtailing food production potential and destroying agro-ecological landscapes and biodiversity.
The prevalent mindset has been that on one piece of land we can have either agriculture or solar panels, but not both. Solar sharing, in which solar panels are installed above the field with crops, overturn this mindset.