National Grid ESO - solar panels in field
How do we generate electricity using solar?

Solar is an important part of the ESO’s ambition to run the grid carbon zero by 2025. But how does solar power work, how much does the UK produce and what happens to solar on a cloudy day?

How does solar power work?

Solar power works by converting energy from the sun into power. There are two forms of energy generated from the sun for our use – electricity and heat.

Both are generated through the use of solar panels, which range those found on rooftops of our homes and businesses to ‘solar farms’ stretching across acres of land.

Is solar power a clean energy source?

Yes, solar power is a renewable energy source. And it’s also limitless – as long as the sun shines, energy will be released.

And unlike the burning of fossil fuels, sunlight converts into power without creating harmful greenhouse gas emissions.

How is electricity from solar energy produced?

Solar panels are made out of photovoltaic cells (which is why generating electricity with solar panels is also called solar PV) that convert the sun’s energy into electricity.

Photovoltaic cells sit between layers of semi-conducting materials such as silicone. Layers have different electronic properties that energise when hit by photons from sunlight, creating an electric field. This is known as the photoelectric effect – which creates the current needed to produce electricity.

Did you know? “1839 – Edmond Becquerel discovered the photovoltaic effect, the first step towards solar power.”

Solar panels generate a direct current of electricity. This is then passed through an inverter to convert it into an alternating current, which is funnelled into the grid, or used by homes and businesses which have panels installed.

Why do new solar PV production records tend to happen in April or May rather than June, July or August?

There are two main reasons for this. First, solar panels work better when they are cool. The hotter a solar panel gets the higher its internal resistance. So for the same amount of sunshine a cool solar panel will produce more electricity than a hot one. April and May tend to be cooler than June or July.

Second, some solar panels are affected by shading. If there is a nearby tree casting a shadow onto the solar panels then this shadow would be bigger when all the leaves are fully developed. This means for the same amount of sunshine a solar panel in the shade of a tree will produce more electricity in April and it would in June.

This is why Solar PV records are more often set in April or May. Although this year may be an exception with particularly cloudy and wet weather in both April and May it may fall to June to be the month that will set the record this year.

Can solar power be generated on a cloudy day?

Yes, it just isn’t as efficient due to the lack of direct sunlight. The rate at which the panels generate electricity will vary depending on the amount of sunlight and the quality, size, number and location of panels in use.

And you may think the often-cloudy UK puts us way down the solar power generation league. In fact, the UK generates more solar power than some sunnier countries like France, and is in the top 10 worldwide of countries producing solar PV.

Where do solar farms fit in?

These are large scale installations where solar panels are used to harvest the sun’s power.

They’re different to rooftop solar systems in that they are designed for solar energy generation that feeds directly into the grid. Large solar farms can be built for one particular use – those built to power data centres for example.

So does the ESO have to forecast the weather?

Yes we do.  We have a team that looks after this so we can estimate how much renewable energy like solar or wind might be produced on any given day. We consider things like lightning strikes, in case it causes outages, and we even look at space weather, just in case there’s an incredible rare solar flare.

What role does solar power play in GB electricity?

The GB system is changing quickly and we’re seeing more renewable sources of electricity, such as wind and solar, come into the market.

In fact, you can see real time information on how GB’s electricity is being produced, including the % of solar generation, on our free Carbon Intensity app. Download the app from Google Play Store and The App Store

A complex set of processes are involved in keeping the power system stable and currently those processes, the foundations of the electricity system, rely to some extent on the intrinsic nature of traditional fossil-fuelled generation. But new technology means that as well as wind and solar farms providing power, they can also be used to manage key properties of electricity such as frequency and voltage.

By 2025, it’s our ambition to be able to operate the electricity system at zero carbon – without the need to burn fossil fuels to keep it stable.