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Generating power from solar panels might seem like an obvious choice in sunnier climes, but in the UK, where much of the summer season is rainy and overcast, how effective can a solar PV system be?

What many people don’t realise is that solar panels can continue to work even with a small amount of light, making solar power an effective option for British homeowners. 

 

How many people have solar panels in the UK?

The cost of solar panels has decreased considerably over the last decade making it a more accessible option for homeowners around the country. Coupled with incentives and grants offered by the government in recent years, and the fact that solar panels can potentially add value to a home, there’s been a rise in homeowners and businesses choosing solar power as their primary method of energy generation. 

As of the end of 2020, there were 1,048,328 sites in the UK with solar panels, and the UK remains a leader in its efforts to move away from fossil fuels. In fact, according to data from the International Renewable Energy Agency (IRENA), as of 2021, the UK sat in 11th place for renewable energy generation.

However, more can still be done, particularly when we look to other European countries, such as Spain, Italy and Germany who all rank higher than the UK for renewable power.

 

How does a solar PV system work?

A solar PV panel comprises numerous photovoltaic cells which are made from layers of semiconducting material. Silicon is the material most commonly used, though new innovations suggest that a crystal material known as perovskite could be even more powerful.

When sunlight hits this material, it creates a flow of electricity. But these cells don’t need direct sunlight in order to work. They still produce electricity on cloudy days, it’s simply that they’ll produce more on a sunnier day.

A solar PV system works most effectively when positioned on a south-facing roof to maximise sunlight, but they can still work well on east and west-facing roofs too. In strong sunlight, each panel can generate around 355W of energy, and most systems contain around 15 panels. Since solar panels generate direct current (DC) electricity, and household appliances use alternating current (AC), an inverter converts the electricity so it can be used in the home or exported to the grid. 

 

Solar panel efficiency

When we talk about solar panel efficiency, we’re referring to how effective the panels are at converting sunlight into power. This figure is represented as a percentage and for most residential installations in the UK, solar PV systems average around 15-20% efficiency. This may seem like a low amount but a 4kW solar PV system can generate enough power to significantly reduce utility bills and carbon emissions for the property. 

The percentage of solar panel efficiency is calculated under standard test conditions (STC) which are a cell temperature of 25oC, solar irradiance of 1000W/m2 and air mass of 1.5. This is then divided by the total solar panel area in meters. Of course, solar panel systems don’t work under these controlled conditions every day, and there are many factors that can influence how efficiently a panel works. 

 

Several factors influence the efficiency of a solar panel

There are a few factors that you need to consider when assessing solar panel efficiency. Shading can have a big impact, and even as little as 10% of a panel being shaded can halve the efficiency.

A reputable installer will carry out an assessment of the exterior of your property prior to the installation taking place to identify any obstructions that may cause issues, such as overhanging trees or chimneys. The position of the panels can also have an impact. As previously mentioned, south-facing roofs are the most efficient while east and west-facing roofs still work but at a lower output. 

The pitch or angle of your roof needs to be considered as it affects how many hours of sunlight the panels will receive over the course of the day. For the best efficiency, a pitch of between 30-45 degrees is optimal. And while you want your solar panels to collect energy from the sun, panels that get too hot can actually decrease in efficiency although the UK rarely sees temperatures hot enough for this to be an issue. 

Finally, keeping the panels clean can help enhance how effective your panels are, since they can absorb more sunlight when there’s little to no dirt, dust or debris on the surface.

Solar panels are designed to be low maintenance and they should last up to 25 years, needing nothing more than an occasional clean and servicing to check they’re working optimally. The inverter will last around 10 years before needing to be replaced.

 

Choosing the right type of solar panel 

The type of solar panel you choose for your PV system can influence how effective they are and the amount of electricity they generate. There are three types of solar panel cells to choose from, depending on budget and size. 

  1. Monocrystalline solar panels are the most efficient, as the cells of these panels are formed from a single piece of silicon. While these are the most effective types of solar panel, they’re also the most expensive. This style of solar panel has cells made from single pure crystals of silicon which are covered with a glass sheet and framed together. Monocrystalline solar panels appear black because of how the light interacts with the silicon crystal. 
  2. Polycrystalline solar cells are composed of fragments of silicon crystals, melted together and then cut into wafers. Because of how this type of solar panel is formed, there are spaces between them and therefore not as much silicon available to convert solar energy. This makes them slightly less efficient when compared to monocrystalline panels, but they are typically larger and more affordable to compensate for this. This type of solar panel has a bluish hue as the light reflects off the fragments in a different way than it does with a pure monocrystalline wafer. 
  3. Finally, thin film solar cells are thinner layers of silicon layered on top of electrical components. While they are cheaper and lighter than the other types of solar panel, they are less efficient too. Your budget and the amount of space you have available on your roof will impact the type of panel you can install, but it’s worth noting that while you may save money choosing polycrystalline or thin film panels, the performance rate is likely to be lower. Monocrystalline and polycrystalline solar panels can reach higher efficiencies of around 20% and 15-17% respectively, while thin film cells are closer to 11%. 

 

Homes in the UK can still benefit from solar

Solar panels work well in the UK, just as they do elsewhere in the world. Despite being a common thought, it’s a misconception that you need to live somewhere with continual, year-round sunshine in order to benefit from solar energy. In fact, whether you live in a sunnier part of the UK or in a location where cloudy skies are a common occurrence, you can still generate electricity through a solar panel system. 

The UK receives more sunlight than its reputation would have you believe, and actually receives a similar amount of solar energy as some areas in France and Spain which have a more Mediterranean climate.

Likewise, the UK gets a comparable amount of sunlight as Germany who is one of the largest markets for photovoltaic panels in the world. This means that you don’t need to be in a tropical climate in order to generate solar power, as solar PVs use light, not heat, to produce electricity. 

Another factor that can be a concern for property owners is the high winds found in the UK. But this can actually be an advantage for domestic solar panels, adding a cooling effect to the panels which can increase their efficiency rather than serving as a detrimental concern.

The contributing factors that influence the effectiveness of solar panels are more focused on the type of panel you choose, where it’s positioned and how well those panels are maintained. By optimising your panels to maximise efficiency, homeowners in the UK can benefit from solar-generated power just as effectively as other countries around the world.

 

What does the future of solar power look like?

Both the affordability and the efficiency of solar panels have improved in the past few decades in the UK, and the government has been incentivising renewable power in British homes through grants to bring costs down.

With energy prices rising and becoming unmanageable for so many homeowners, there’s likely to be an even bigger push for renewable energy and increases in EPC requirements, particularly in new build properties in the future.

As researchers find new and more innovative ways to improve the efficiency rate of photovoltaics, more of us can make the most of solar power and other renewable energy solutions. 

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