Energy from the sun gives us free, renewable electricity, and benefits the environment. That’s why nearly 1.4 million households in the UK have so far installed solar panels. You may be wondering, though, whether it’s worth going solar in this country – hardly renowned for its sunny weather.
You’ll find out here whether solar panels work effectively without direct sunlight. We’ll also explain other important considerations about switching to solar to make sure it’s the right call for you.
How Solar Panels Work
Solar photovoltaic (PV) panels generate electricity by capturing energy from the sun. This is why they’re typically installed on roofs. Solar cells in the panels absorb miniscule packets of electromagnetic energy called photons – blips of energy waves that travel at the speed of light.
This stimulates the release of electric charges (electrons) that create a direct current (DC) of electricity. A solar inverter turns this into AC (alternating current), which we need to run our homes.
The Photovoltaic Effect
Solar panels rely on the photovoltaic principle. This is a phenomenon in physics and chemistry. A semiconducting material, such as silicon cells in solar panels, produces an electric current when exposed to sunlight.
Solar panels achieve optimal performance in direct sunlight. But they only need daylight – not direct sunlight – to generate electricity. In other words, your solar panels will work from sunrise to sunset, all year long.
Solar Panels, Direct Sunlight And Indirect Sunlight
When there’s no cloud cover, light from the sun has an uninterrupted path to the Earth surface. This direct sunlight is perfect for solar panels. However, solar energy is still available in indirect sunlight (diffused) on cloudy days. Clouds block some of the sun’s rays, but not all.
Solar panels produce electricity mainly from infrared energy and visible light. But they also make use of ultraviolet (UV) light. Around 90 percent of the sun’s UV light penetrates through clouds.
This is why sunscreen is still recommended on cloudy days to guard against skin cancer. It’s also why solar panels continue to function in indirect sunlight.
Peak Sun Hours
Peak sunlight hours are key to how much power your solar panels will produce in a day. The UK gets an average four to five hours of sunlight a day. About half of these are peak sun hours.
Peak sunlight hours are essentially the times when sun intensity is around 1,000 watts (W) a square metre. They vary from region to region. Solar energy systems typically have six to 12 solar panels, each producing around 400-450W of energy in peak sunlight.
How Does The Weather Affect Solar Panels?
While solar panels don’t need direct sunlight, their productivity is affected by overall weather conditions. And the UK gets a broad mix of weather. Long known for cold, cloudy, rainy days, we’re now starting to see more heatwaves (more on this later).
Solar panel output may fluctuate because of the weather but it only stops solar panels from working if it prevents access to sunlight – heavy snowfall, for example.
Solar panels produce more power on sunny days. They will, however, continue to work in overcast weather, and throughout the changing seasons. As long as there’s sun, they have a source of energy to draw from. Solar power generation dips by about 25 percent during the winter months of December and January, with fewer hours of sunlight.
Solar Panel Performance On Rainy Days
Solar panels continue to generate power during rainy weather but the reduced sunlight may lower efficiency.
They can also withstand hailstorms. However, large hailstones may cause damage such as chipping. This can usually be repaired by a professional to save the cost of replacing the panel.
Conversely, rain can also benefit a solar installation. Solar panels are designed to be self-cleaning. They have a protective coating that prevents water droplets from adhering to the surface of the panel. Rainfall, therefore, washes dirt off the panels so they get optimal sunlight.
Solar Panel Performance In Overcast Weather
Solar panels perform fairly well in the weaker sunlight of cloudy weather. The sun doesn’t suddenly stop working when clouds appear.
Low clouds that block sunlight can reduce solar panel efficiency by 10-20 percent. However, clouds higher in the sky can enhance sunlight absorption. Water in the clouds acts as a lens to reflect more sunlight onto the panels.
Solar Panel Performance In Fog
As an island, Britain sees occasional localised fog in certain areas as warm air from the sea meets cold land, with coastal areas getting more foggy days. Solar panels continue to capture the sun’s energy in foggy conditions. Sufficient visible light and ultraviolet and infrared rays penetrate through the haze.
Power capacity will be down slightly but not as much as in cloudy weather. And fog usually dissipates throughout the day.
Solar Panel Performance In Heatwaves
Weather experts at the UK Met Office say sizzling summer heatwaves are now 30 times more likely because of climate change.
The highest temperature in the country to date was recorded in July 2022 in Lincolnshire. The mercury hit 40.3C. 2023 saw the hottest June since the Met Office started collecting data in 1884.
Today’s solar panels can function when their temperature is in the range of -40C to +85C. They’re highly unlikely to ever get this cold or this hot, even in the coldest countries or the hottest countries.
If solar panels ever reached 85C, they would still work at 80 percent of their maximum power. But they produce slightly less electricity over 25C, so there is an optimal operating window for most.
In a UK heatwave, the temperature is typically 25C or higher. Solar panels get warmer than the ambient air temperature, so power output declines to some extent. But even if a solar panel reaches 50C, it will still operate at 92 percent of its peak output capability.
Do Solar Panels Work In The Shade?
It’s not only overcast weather that lowers solar panel efficiency. Anything that blocks sunlight from the panels can reduce power production, including shade.
Shade can reduce electricity generation by around half unless steps are taken to lessen its impact.
There are basically two types of shading:
- Temporary (or dynamic) shading – shadows cast by moving clouds.
- Permanent (or static) shading – from nearby trees, buildings, chimneys, or satellite dishes.
Installing solar panels where light is unobstructed avoids permanent shading. But it’s not always practical. Solar panel shading issues can often be overcome by a well-designed installation and measures such as trimming trees.
Some solar panel systems incorporate DC power optimisers to minimise the impact of shading. If one panel is in the shade, it won’t affect the performance of the others.
Do Solar Panels Work If It Snows?
Contrary to some misconceptions, solar panels rely on daylight to function effectively – not heat or direct sunlight. This means they can power homes in subzero temperatures.
Moderate snowfall won’t stop solar panels from doing their job. Light can penetrate through two to three inches of snow (five to eight centimetres). And snow tends to slide off solar panels because they’re installed at an angle. However, melting snow can get into the solar panel system if it has sustained damage because of poor maintenance.
In some cases, snow, like rain, can actually be good for solar panels. This is down to the albedo effect – solar radiation reflected off the roof surface, which can boost solar panel efficiency, especially with double-sided (bifacial) models.
How Solar Power Combats Climate Change
As we’ve seen, heatwaves are on the increase. But that’s by no means the only effect of global climate change. It’s resulting in other types of extreme weather including heavy downpours. It’s also sparking wildfires, melting ice caps, threatening wildlife, and spreading deadly diseases such as malaria.
Burning fossil fuels – coal, oil, and natural gas – is the main cause of climate change. It accounts for more than three-quarters of all greenhouse gas emissions. It’s also responsible for nearly 90 per cent of the carbon dioxide that’s tipping the greenhouse effect out of balance as more heat from the sun becomes trapped in the atmosphere.
Solar power combats climate change by decreasing use of fossil fuels, which reduces carbon emissions and other greenhouse gases. It’s one of the cleanest sources of renewable energy available and, unlike fossil fuels, will never run out (at least not for another 10 billion years).
Solar power has minimal carbon footprint. It produces only 0.8 kilograms of carbon dioxide for each kilowatt hour of electricity it generates. And a single solar panel typically saves more than 900 kg of CO2 a year.
How To Optimise Solar Output
Going solar is a significant investment but it saves money by reducing reliance on mains electricity from the grid. Getting the most from your solar panels will ensure you get the full financial benefits and see a return on your investment faster.
Measures you can take to do this include:
- Choose solar panels with high energy efficiency. Monocrystalline solar panels have the highest efficiency, up to 24 percent. They also work better in low levels of sunlight than other types of solar cells.
- Hire an experienced solar installer. They’ll know how to install your solar panels so they get optimal sun exposure.
- Keep your solar panels free from buildups of dirt and debris.
- Schedule professional maintenance checks and an annual service.
- Consider solar battery storage.
Final Thoughts On Solar Panels And Sunlight
Solar panels cut household electricity bills by up to 50-70 percent and work best in direct sunlight. But they also produce power without it.
If you can see natural light outside, your solar panels will be capturing energy from the sun. And you’ll continue getting free electricity no matter what challenges the UK climate may present, as long as the weather doesn’t stop the panels accessing light.
If you’d like to know more about solar panels, national renewable energy experts Effective Home can help.
Call 0333 003 0703 (local rates) or get in touch online.
