Solar farms that work at night, in the rain and self-clean? Yes, it exists. Find out.
With the worldwide roll-out of solar, raising the efficiency of energy conversion isn’t just about the materials science of PV cells. Solar farms could soon play a vital role in the energy system 24 hours a day, after a breakthrough trial proved they can even help balance the grid at night.

Scientists have tested panels that keep producing power even when the sun goes down.
”A low-cost thermoelectric generator works using the temperature difference between the cooling solar panels and the surrounding air. Next, friction generated by raindrops landing on and running off solar panels can create electricity using a triboelectric nanogenerator. Finally, automated robots trundle across acres of panels to clean them of the dust, water, sand and moss accumulating on the surface: dirty panels can reduce the output of solar panels by as much as 85%.”
Douglas Broom, from World Economic Forum
Traditionally solar panels, or photovoltaic cells, have suffered from the effects of changeable seasons and the fact that they don’t work at night and this is a problem scientists around the world have been wrestling with, and some are now developing innovative ways to overcome the issue.

1. Solar power in the dark
Who said solar farms don’t work under the stars?
An original study was conducted at Stanford University where a research team added a thermoelectric generator – a device that produces currents from temperature differences – to one of these particular solar panels.
They work by using the heat or infrared light radiated from the surface of the solar panel into space on clear nights.
The panels were built using easily available components and the team says they offer the potential to provide a continuous reliable power source for the estimated 750 million people around the world who lack access to electricity at night.

2. Rain-powered solar panels
Heavy clouds and rain can make them less effective, but scientists from Soochow University in China believe they have solved this problem by taken the friction generated by raindrops landing on and running off solar panels, and used this to create electricity.
They placed a transparent layer containing a triboelectric nanogenerator (TENG) over a conventional solar panel. The TENG converts motion – in this case the impact of raindrops – into energy.
As well as boosting power output on rainy days, the friction-powered panels can also produce electricity at night if it rains.

3. Robot cleaners for solar farms
Just as cloud and rain can block out the light to solar panels, so too can dust and dirt.
In fact, research shows that dust, water, sand and moss accumulating on the surface can reduce the output of solar panels by as much as 85%.
Powered by an on-board solar panel, autonomous dry cleaning robots work at night to limit disruption to the panels. Using microfibre cloths and jets of air, one year of their use has saved enough water to meet the needs of 220,800 people.
The robot cleaners’ performance is monitored by artificial intelligence software that plans preventative maintenance to avoid breakdowns.

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