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Floating Solar - A Crazy Big Idea?


This is a crazy big idea. But how crazy?

In Japan, Kyocera is building a 13.5 MW floating solar PV plant on a reservoir behind the Yamakura Dam, east of Tokyo, in partnership with the French company Ciel & Terre. When completed in March 2016 it will cover 44.5 acres and power nearly 5,000 energy-conserving Japanese households.[1]

Note: This is not a BCSEA position — just a personal essay exploring a possible new approach. 

Land is in short supply in Japan, but open water is plentiful. Ciel & Terre’s Hydrelio platform is 100% recyclable, made from high-density polyethylene that can withstand ultraviolet rays and corrosion, and it will be located at the center of the reservoir away from the flora and fauna that live and feed around the edges.[2]

In terms of space, that’s 3.3 acres per megawatt, which compares very favorably to the NREL’s estimate for land-based solar at 8.3 acres per MW. [3]


Solar PV on BC’s Lakes and Reservoirs?

BC has plenty of lakes and reservoirs, so could we do the same here? Okanagan Lake covers 86,000 acres. If solar was installed on 10% of its surface, providing 2600 MW of capacity, it would generate 3,000 GWh a year, sufficient to power 270,000 households (or 500,000 future households using super-efficient lights and appliances). Swimming facilities and docks for boats could turn the array into a pleasurable public amenity. [4]

The calculation assumes a 12.5% capacity factor, which is low. Solar efficiency is determined by climate, temperature and technology, and solar efficiency is creeping up every year. Ciel & Terre report that their system has a higher efficiency due to the cooling effect of water on the panels, so the estimates here are all low-balls.

The Upper and Lower Arrow Lakes in the Kootenays are 230 km long, running from Revelstoke to Castlegar; the lakes were created in the 1960s when the Columbia River was dammed, raising the water level by 12 metres. If 10% of their 113,000 acres was covered with solar it could provide 11,000 MW of capacity, generating 12,000 GWh a year, enough for a million households.

Cowichan Lake on Vancouver Island covers 15,000 acres, so 10% solar coverage there would generate 550 GWh a year, sufficient for 50,000 households.

The Williston Reservoir behind BC Hydro’s WAC Bennett dam is far larger at 410,000 acres, so 10% solar coverage there would generate 13,500 GWh a year - the same as the dam itself.

What are the Ecological Impacts?

What about ecological impacts? A floating solar array would darken the water beneath, so fish might not hang out beneath it, but it would also cool the water, helping to offset the warming we are causing by our use of fossil fuels and discouraging algae growth. The arrays would also reduce evaporation, enabling more water to be stored.

What about the practical aspects? The floating panels can rise and fall, but the large flat area has a calming impact since it sucks the momentum out of any waves. In Japan, the panels are designed to be able to stand up to a typhoon. The angle of the panels is low, so they will not be caught by the wind. They have not yet been installed on lakes that freeze in winter, but if they were, it would need a platform that allowed ice to form underneath, lifting the solar array above it.

Crazy - or Not?

So is this crazy, or not? If you find yourself instinctively dismissing the idea, do at least first visit Ciel & Terre’s website at www.ciel-et-terre.net, and see the photographs and videos of installed systems. This is not a hypothetical proposal.

If you still doubt that it’s possible, check out the video from Mark Bennett, a fruit farmer in Berkshire, England who installed a Ciel & Terre 200 kW floating solar system on a 3-acre man-made lake. It took only a week to install the 800-panel system, and they needed no tools or heavy equipment. You just clip the platform’s plastic units together, attach the solar and float them out onto the water. In terms of installation speed per kW, it’s seven times faster than a rooftop installation. They wash the system twice a year using a brush and water from the lake.[5]


Mark paid £250,000 for his 200 kW system, or £1.25 per watt. That’s CAN $2.35 a watt, compared to the current BC price for installed solar PV of $3.50 to $4. His quick seven-year payback is helped by Britain’s feed-in tariff, which pays 18 cents/kWh.

Kyocera has not said how much the Japanese floating platform will cost. In Europe, thanks to market and labour efficiencies, land-based utility-scale solar costs $2.50 a watt, producing power at 8 cents/kWh (9 cents in cloudier Germany). By 2025 the cost of solar is expected to fall to between 4 and 6 cents, according to a 2015 report by the Fraunhofer Institute for Solar Energy Systems. [6] A major new study by the Berlin-based Agora Energiewende has forecast that by 2050 solar PV will cost less than 2 cents/kWh. [7]

More Summer Power = More Winter Storage

Solar produces power in the summer, but BC is blessed with great storage in the form of the very dams the solar could float on. BC Hydro’s dams are filled by rain, snowmelt and glacier-melt, mostly in the spring. In 2012, BC Hydro published a study that looked at the impact of the warming climate on water flows into its dams, and the modeling showed increased flows into the dams in the spring due to the warmer weather producing more rain and less snow, and decreased flows in summer, so an increase in summer power could contribute the grid’s overall performance.

BC’s peak power needs are in winter, so the summer solar could allow the dams to remain fuller, providing greater capacity in winter. Alternatively, it could allow the discharge of more water to the benefit of the downstream fish, a hot topic in the Columbia River basin.

What about jobs? The International Renewable Energy Agency estimates 18 job-years per MW during installation and 0.3 job-years per MW for operation and maintenance. [8] If the number for a utility-scale floating solar project was 7 times fewer due to the speed of installation, at 2.5 job-years per MW, the installation of 11,000 MW of solar on the Arrow Lakes spread over 11 years would create 2,500 full-time jobs in the West Kootenays for 11 years, and 1,000 to 3,000 permanent jobs doing operations and maintenance.

Floating Solar for Russia? China? 

Floating solar. Who would have thought it? As a climate-geek, I worry about a country such as Russia, with its economy shoulder-deep in fossil fuels. Lake Baikal, north of Mongolia, has a surface area of 7.8 million acres. 10% solar coverage would generate 258,000 GWh a year, a quarter of the electricity Russians use each year. It would need a special platform design to keep the solar operating when the lake freezes over in winter, and a massive new electrical distribution network, but Russia’s got plenty of good engineers. [9]

Then there’s China, pouring out the greenhouse gas emissions thanks in part to all the goods it manufactures for us. China has lakes that total 27,000 square kilometres in area, and China generates 1.95 million GWh of electricity a year by burning coal. 30% solar coverage on their lakes would allow 600,000 MW of solar PV, generating 736,000 GWh a year, potentially substituting for a third of their coal-fired power. [10]

So let’s get totally hypothetical, to show how this works.

For China, floating solar on the East China Sea over 40,000 sq km (200 x 200) would meet China’s entire annual demand.  Japan could meet its annual demand from 11,000 sq km (105 x 105) on the Sea of Japan (see map). This is purely hypothetical, since the grid needs power 12 months a year, not just in summer. So now let’s add deep ocean wind turbines for winter power … but that’s another story. [11]

You can do the math for any country using this formula: 1 square kilometre of water (247 acres) allows 75 MW of floating solar, which will generate 82 GWh of electricity a year. And some say our civilization can’t survive without fossil fuels?

Call me crazy, but I find it fascinating.


See also: India Plans World’s Largest Floating Solar Power Project (50 MW)​


[1] Solar Panels Floating on Water Will Power Japan's Homes. National Geographic, January 2015. http://news.nationalgeographic.com/news/energy/2015/01/150116-floating-solar-power-japan-yamakura/

Kyocera and Century Tokyo Leasing to Develop 13.4MW Floating Solar Power Plant on Reservoir in Chiba Prefecture, Japan. http://global.kyocera.com/news/2014/1205_dfsp.html

[2] Ciel & Terre: http://www.ciel-et-terre.net/ Videos:  http://www.ciel-et-terre.net/media-center/

[3] Calculating Solar Energy's Land-Use Footprint. Renewable Energy World, 2013. www.renewableenergyworld.com/rea/news/article/2013/08/calculating-solar-energys-land-use-footprint

[4] Average household electricity use in BC is 11,000 kWh a year. A future super-efficient household might use half of that. When calculating solar yields I have assumed a 12.5% capacity factor. The formula to turn MW into GWh is (eg) 10 MW x 24 x 365 x 12.5% = 10,950 MWh = 10.95 GWh a year.

[5] First floating solar farm built in UK. Guardian, September 2014. http://www.theguardian.com/environment/2014/sep/29/first-floating-solar-farm-built-in-uk

Hydrelio© Floating Solar System at Sheeplands Farm, UK - Interview with Mark Bennett. YouTube video. https://www.youtube.com/watch?v=z2CliTWQorg

Des centrales solaires flottantes. Ciel et Terre. YouTube Video (French) https://www.youtube.com/watch?v=l1DcUoTMsU4

[6] Solar Energy emerging as cheapest power source in many parts of the world. February 2015.  http://www.agora-energiewende.org/topics/optimisation-of-the-overall-system/detail-view/article/solar-energy-emerging-as-cheapest-power-source-in-many-parts-of-the-world/

[7] Solar at 2c/kWh – the cheapest source of electricity. REnew Economy, February 2015. http://reneweconomy.com.au/2015/solar-2ckwh-cheapest-source-electricity-47282

[8] Renewable Energy and Jobs. IRENA, December 2013, page 42. http://www.irena.org/rejobs.pdf

Workforce Challenges and Opportunities In The Solar Photovoltaic Industry in Toronto. Sheyda Saneinejad, City of Toronto. https://www1.toronto.ca/static_files/economic_development_and_culture/docs/Sectors_Reports/solarpv_challengesopportunities.pdf

[9] Electricity use country by country: http://en.wikipedia.org/wiki/Electric_energy_consumption

[10] China has 14% solar capacity factor. Lakes of China: http://en.wikipedia.org/wiki/List_of_lakes_of_China

[11] Floating Wind Turbines Set to Conquer Deep Ocean. Scientific American, Jan 2, 2012. http://www.scientificamerican.com/article/floating-wind-turbines-conquer-deep-ocean/