Power From The Sun, Floating On Top Of Sewage

Floating solar panels offer a lot of benefits, but no one wants to ruin our lakes with them. But there are huge pools of less beautiful water all over the world, ripe for having a solar array floated on top of them. Just hold your nose.

Solar power has a problem. Despite shattering efficiency records and slashing prices, placing new solar farms can be expensive, and often comes into conflict with people who don’t want land taken up with huge solar arrays. With global solar capacity growing 40% to 27 GW in 2011, developers are looking for new sites to deploy their panels.

One area of unused real estate? Water. Not oceans or lakes, but bodies of water that most people probably don’t even know exist: the vast expanses of wastewater ponds, sewage treatment pools, dams, and reservoirs that sit unused around the world.

Solaris, an Israeli startup, is building floating solar grids made from flexible plastic, fiberglass, and silicon solar cells that generate about 200 kw each. Water’s advantages are unmatched anywhere on land: no shade, low (or no) environmental impact, and perfectly flat with no competing uses. For a desert nation such as Israel, Solaris estimates it could hit the country’s renewable energy target itself—10% to 20% renewable energy by 2020—just by covering the country’s 400 wastewater reservoirs with its floating grids.

Solaris hit upon its technology by tackling the solar power challenge from a different angle: how to reduce heat on concentrated panels. Concentrated solar panels use curved mirrors to focus the sun at strengths 20 times that of a normal cell. Although they are highly efficient, and drastically reduce the area covered with silicon, these cells heat up fast. By designing floating panels, Solaris realized it could offer myriad benefits for power production, including a cooling system that relies on the evaporative cooling of the water beneath the panel.

So far, Solaris has installed its first prototype on a reservoir in Provence, France (results are due in June 2012 according to GE) while the company works with the Israeli water authority Mekorot to install floating grids within Israel itself.

If successful at scale, Solaris could change the cost equation for solar electricity in many places around the world. Sunlight is already out competing fossil fuels in some locations by delivering cheaper power, a concept known as grid parity that we reported on last month. Imagine what slicing the cost of siting new solar arrays—as much as one third of the final price tag—could do?

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  • Emily Kumpel

    Cool idea, though there are other considerations before saying that these water surfaces - including wastewater ponds - have "no competing uses".  UV from sunlight on the surface of a wastewater pond plays an important role in disinfecting pathogens; covering up the surface may have a negative effect the treatment performance in wastewater ponds. Dams and surface water reservoirs may be a habitat for wildlife. On the other hand, covering reservoirs that store chlorinated water may be an advantage in other cases  (http://articles.latimes.com/20....  The surfaces of these water bodies are not necessarily underutilized space, but the surface can play an important role through its interactions with the surrounding environment.