Clean Water, Clean Power - the Case for Solar Floatovoltaics

By Emma Bailey

  Human-caused climate change is a very real and urgent threat to all life on this planet. The rapidly worsening issue of global warming requires an immediate switch to energy sources which generate far fewer emissions during production.  According to the stabilization wedge theory, we already have the means to get climate change “under control.” The theory surmises that we can and should use a variety of conservation and energy production methods, rather than rely on a single "silver bullet.” Implementing the recommendations of this theory, however, will call for new and ingenious approaches to all aspects of the power production cycle.


  In their piece, let's consider solar power, one of the leading alternative energy production methods. The sun produces vast amounts of energy and the technology for using it has existed for decades. On a small scale, using solar power simply involves putting solar panels on someone's roof. Large-scale solar projects or solar farms can be more difficult, because they require a lot of land which is not always easy to come by. Take for example Japan, an island nation with a large population. It doesn't have the space for a large solar farm on land -- but it could easily put one in the water.


  The solution to this problem: floatovoltaics or floating solar panels, such as those pioneered by the Far Niente winery in Napa Valley, California in 2009. One of the world’s first floatovoltaic systems consisted of 1,000 solar panels installed in an irrigation pond on their property to expand a solar farm they already had -- and all without using land that could go to growing grapes.


  A floatovoltaic is a photovoltaic system designed to float on the surface of a large body of water like a reservoir or sewage treatment pool that is typically hidden from view. It uses standard solar panels attached to a lattice which itself is attached to pontoons. The solar panels collect sunlight which they convert into direct current electricity that travels through transformers and is converted into alternating current electricity so it can be distributed by utilities. The floatovoltaic's full array is anchored by buoys and tie lines to keep it in place.


  Floatovoltaics also offer a number of benefits that terrestrial solar panels don't. First off, the water below them acts as a natural cooling system. Since solar panels absorb sunlight all day long, they can become very hot, which impairs their efficiency. A typical solar panel starts to lose efficiency once the temperature gets over 77° F, which is a problem in places like California, especially during the summer. According to one study, solar panels' efficiency improved by 8 to 10% if they were placed in water.


  The system can also help in slowing evaporation simply by covering the water, and thus reducing its exposure to sunlight. This fact alone makes floatovoltaics very attractive to arid or drought-stricken areas like California or Australia. Less sunlight hitting the water can also mean less algae growth. In addition, since the chosen ponds typically get little use, leasing them is not expensive, and the ponds are often near existing infrastructure which helps lower the cost of interconnection. The owners of the ponds can even make some money by selling the resulting clean energy back to the local energy providers. Putting floatovoltaics in a hydroelectric dam reservoir, is especially effective for it combines two methods of generating renewable energy which compensate for each other's weaknesses. The dam is vulnerable to droughts while the solar array is not, and the dam will keep working if a bunch of cloudy or rainy days keep the solar array from collecting energy.


  Other countries have installed floating solar arrays. A French company called Ciel et Terre has devised the Hydrelio system, a special technology for mounting floatovoltaics. It is currently working on a project at the Yamakura Dam in Japan that will be the world's largest floating solar array. An Australian company, Sunengy, has devised a concentrating photovoltaic (CPV) technology designed to work with hydroelectric dams and, it is working on a pilot project using the technology on a dam near Mumbai, India. A Swiss company called Novation is building "solar islands" that will use both solar panels and concentrating solar thermal (CST) technologies.


  In September 2014, the International Energy Agency stated that solar power could become the chief source of electricity by 2050. Solar arrays are expected to produce a global total of 61 gigawatts by the end of this year and 70 gigawatts by the end of next year. Japan is expected to install at least 12 gigawatts' worth of solar arrays, and most of those will most likely be floating arrays. Other island nations, like Singapore and Great Britain, will follow suit, as will any country or region wanting to hold onto arable land. As sea levels continue to rise, the promise of floatovoltaic panels will only increase.