from pv magazine global
French PV system installer Sunbooster has developed a cooling technology for solar panels based on water. It claims its solution can ramp up the power generation of a PV installation by between 8% and 12% per year.
The solution consists of a set of pipes that can surround a rooftop PV system or ground-mounted plant. The pipes are used to spray a thin film of water onto the glass surface of the modules.
“The company had originally experimented with a water-vaporizing solution, but this produced thermal shocks for the PV system,” Sunbooster CEO Grégory Boutteau told pv magazine. “Furthermore, the drops produced by this cooling system had a negative impact on solar light absorption.”
Water flow
The company’s solution is a patented pipe with a number of very small holes, so special installation skills are required. Stored rainwater is pushed into a ramp at the edge of the panels. Water then flows onto the surface of the modules and immediately lowers the temperature.
“The materials used to build the pipes have been chosen based on their quality, reliability and durability,” Boutteau said, without providing additional details about the patented technology. “Pipes are UV-resistant and drilled with holes – their number and size are defined by our design and engineering office in respect of our patents.”
The water only spreads across the glass surface of the panels and does not touch any plastic parts, such as the backsheets or other components. “It can be considered in the same way as rain, and for this reason it does not affect the warranty of the modules,” Boutteau said.
The system is set in motion by a temperature sensor which triggers the water spread when ambient temperatures exceed 25 C. Although the water may have some influence on the modules’ light absorption, this is fully compensated by the increase in power yield that can be achieved by preventing temperatures from surpassing 30 C, Boutteau said.
The cooling systems collect the water from a rainwater tank. And after the water is used, it can be recycled, filtered, and stored again. “Our Sunbooster solution works in closed circuit and doesn’t need additional water,” Boutteau explained.
Cost considerations
The technology, which can be applied to PV systems and solar plants built at all kinds of tilted angles, currently costs almost $275,000/MW. But Sunbooster expects to more than halve that to between $110,000/MW and $165,000/MW within the next two years.
“We are now developing new partnerships with big players,” said Boutteau. “And this, combined with the economies of scale of large ground-mounted projects, will help us reduce our costs significantly.”
So far, the technology has only been adopted in projects backed by cost-offsetting incentives. However, the company claims that it has started to sharply lower the cost structure of its systems to support unsubsidized projects in the near future.
For a 10 MW PV plant, around 25 km in pipes would be needed, which complicates logistics and installation, Boutteau said. “But the system is easy to deploy with the necessary skills,” he added.
Sunbooster currently needs to send teams out to install its systems. However, the company plans to train partners who are capable of deploying its technologies at a global level, in line with its standards. “Our partners will be referenced in our network validated by an internal certificate delivered by Sunbooster,” Boutteau said.
He added that the adoption of a similar cooling system could increase the complexities of projects and the number of possible variables. “Installing our system in Spain or Germany is not exactly the same thing,” Boutteau stated. “Furthermore, there are many other water-related factors that must be taken into account, such as water vaporization rates, humidity and available water resources.”
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Very nice idea but patented technology? It’s PVC pipe with holes drilled in it, dripping over the panels into an aluminum gutter below. I’m geeked to try this on one of my two arrays to see how well it works. I’ve got an old portable pool pump to filter the water and a plug in thermostat to power it. Switching on using ambient temperature seems really simple. I wonder if a sensor on the panel taking surface temperature would be more accurate and perhaps save some energy by reducing unnecessary activation. The system could potentially run into the evening on warm summer days. Also I wonder if spreading the water across the panels more uniformly by using a surface tension reducer (such as a dishwasher water rinse aid) would increase or reduce the efficiency of the panels. If the goal is just to reduce the temperature, perhaps the resulting sheet of water wouldn’t cool the panels better but might filter or refract sunlight detrimentally….or not. Interesting possibilities. What do others think?
The things that solar salesmen don’t tell you. I live in Central Florida and my 18 kWh system only generates 60 to 65%. Using an inferred hear gun on any given summer day the panels are 110F at 3PM. With a los of -0.42/C that equates to additional loss of 18.5%. Panel are estimated at 77F to have 85% efficiency. 85-18.5= 66.5% efficiency. A system like what’s in this article could be worthwhile to try.