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Solar energy explained

What is solar energy?

In simple terms, solar energy is energy that comes from the sun.

It’s one of the most plentiful sources of power known to man – and here on earth we’re lucky enough to have direct access to it. Just ask Tesla boss, inventor, space invader, and solar power engineer, Elon Musk. He says, “if it wasn’t for the sun, we’d be a frozen, dark ice ball’ and ‘the amount of energy that reaches us from the sun is tremendous. It’s the 99 percent-plus of all energy that Earth has.”

For centuries, we humans have been using the sun to help us grow crops, unwind on holiday, extract salt from seawater (the list goes on). And now – at last – we’ve learned to convert the sun’s energy into electricity by using solar photovoltaic (or solar PV) panels.

Of course, not all the sun’s energy is up for grabs anyway. Around 70% of the sunlight we receive is absorbed by the Earth and potentially useful for us – the rest is reflected back into space.

But that isn’t stopping us from harnessing solar energy in lots of different ways, from small solar panel installations on domestic roofs, to large-scale solar farms in fields and deserts.

What is the photovoltaic effect?

It’s the production of electricity between 2 separate materials. But when we’re referring to solar panels, we’re talking about the top and bottom layers of silicon in them – when both are exposed to light.

Oh, and so you know, the word photovoltaic derives from the Greek word phōs, meaning light, and the word volt, a unit of electricity.

Who discovered the photovoltaic effect?

Ingenious teenage scientist, Edmund Becquerel was the first to discover the photovoltaic effect, while tinkering with electrolytic cells in 1839. Aged just 19, Becquerel generated electricity by adding silver chloride to an acidic solution – creating voltage and current.

How do solar panels work?

A solar PV system is made up of several components, including:

  • Solar cells.

  • An inverter.

  • Generation meter.

Solar panels are made up of many solar ‘cells’. Each cell contains 2 wafer-thin layers of silicon, one on top of the another. The top layer has been treated so the atoms within it are unstable, with too many electrons. The bottom layer has been treated, but this time, so there are too few, with plenty of space for them to move around. The electrons want to move from the top layer to the bottom, but they can’t until the cells are exposed to sunlight.

Once sunlight hits the top layer of silicon, the electrons in there become ‘excited’ and start moving towards the bottom layer. Once all these electrons are moving together in the same direction, electricity is created. Boom. It’s then harnessed by two metal contacts, placed either side of the silicone, which creates a circuit.

How is solar energy stored?

Solar plants can now sap up the sun’s rays and store its energy in water, salt, or fluids – which is then later used to generate electricity, so solar power can work after dark. Bonus.

But you’ll have probably heard by now about battery storage systems that can be installed in the home. Today, lithium ion storage batteries are the most common – but there are more systems on the way.

Battery technology is now becoming so important, it’s part of the UK government’s Industrial Strategy, which sees the developers of renewable batteries receive funding. And it’s all being described as an energy revolution, no less.

How is solar energy converted into electricity?

As you’re probably aware, the electricity we use day-to-day is ‘alternating current’ (AC), whereas electricity created by solar power is known as ‘direct current’ (DC). So before solar energy can be used, or fed into a building, it needs to go through an inverter.

After this, the energy is made suitable for the home – ie. via a 240V plug socket – just like the power we get from an electric company.

How does solar energy enter the grid?

Any surplus solar energy that your solar panels produce can be sent back to the grid via an export meter (usually on the side of your house). Telegraph poles and the infrastructure in your local area will help it on its way. But anyone familiar with the acronym FIT will probably know all this...

For the benefit of those who don’t, the UK government introduced the Feed-in Tariff (FIT) scheme in 2010, to pay homeowners for the energy they produce. It’s a smart way of encouraging more renewable energy generation, and getting more people to become that bit closer towards energy self-sufficiency.

How efficient is solar energy?

*Fact to astonish your kids with alert* The earth can absorb more energy in one hour than the world uses in one year, according to former US Energy Secretary and Nobel Prize-winning physicist Steven Chu, so harnessing solar energy is something of a no-brainer!

Of course solar energy efficiency has improved over the years. The first ever silicon PV solar cell, created in 1955, could convert sunlight at 4% efficiency – yet solar cell developers have been increasing this number ever since.

Oh, and if you wonder how we measure efficiency in a solar panel, it all comes down to how many watts each cell in that panel produces. These are the types of PV cells currently available, along with their typical efficiency percentage:

  • Amorphous/thin film silicon (7%).

  • Hybrid silicon (18%).

  • Monocrystalline silicon (15%).

  • Polycrystalline (or multicrystalline) silicon (13%).

But these are some of the new types of uber-efficient cells – hopefully coming soon:

Perovskite (20%)

Being cheaper and more flexible than silicon, perovskite may just be a game-changer. It’s a mineral, first discovered on a Russian mountain in 1839, and now being used to develop solar PV cells. It has researchers excited as it’s already 20% efficient. And the diverse applications possible make it a major contender in the future.

CPV (44%)

Clocking 44.5% efficiency, are the new ‘concentrator’ photovoltaic (CPV) panels. These babies come equipped with lenses to concentrate sunlight on tiny cells measuring less than 1mm². The solar cells are made from materials based on – wait for it – gallium antimonide substrates (GaSb), usually found in infrared lasers.

Is solar energy more expensive than regular energy?

Not to generate, no (for that, it just needs sunlight). Although creating, transporting and installing the panels can be. But as more people embrace solar power, and the more capacity we have to sap it up, the more costs can come down.

The actual cost is always dictated by the market, and prices can vary throughout any given day. But the more investment solar energy gets, the cheaper it will become to produce – finally, being able to compete with fossil fuels. Recent studies from analysts, Lazard and the eia show increasingly reduced costs moving forward. Ultimately, the giant shift now underway will be cost-effective in the long term.

Solar panels can save you money by creating energy savings. If you use your solar energy in real time, while it’s being generated by the sun – like a spin cycle at midday, for example – it can draw electricity straight from your PV panels. If you use it at night, it will draw electricity from the national grid, and you’ll pay for it on your energy bills. So any electricity you use from your PV panels will reduce your energy costs. Win-win.

Can solar energy power the world?

It’s possible. But we’d need to make the leap away from fossil fuels first, which won’t be easy. Reports from the International Energy Agency (IEA) suggest solar could be the world’s largest source of electricity by 2050, ‘ahead of fossil fuels, wind, hydro and nuclear’.

Being taken up at this rate, a new and exciting era of solar power could be a reality – if the majority of us choose it.

Can solar energy work without sunlight?

The photovoltaic cells in solar panels don’t actually need direct sunlight to work; they can still produce some electricity when it’s cloudy.

The best bet is a south-facing roof though, with a pitch of 30-40 degrees. We’d advise against installing on a north facing roof, but you might find that an east or west-facing roof still works well – although expect to generate 25% less energy.

Are there any disadvantages to solar energy?

A few. Mainly in the creation of, and transition to, all this new technology. Producing solar power en masse poses 3 big challenges:

  • Cost (research, development, manufacture).

  • Space (we’re gonna need a bigger roof).

  • Storage (where do we stash all this energy?).

Building wind farms and large-scale solar plants means humongous upfront costs – because the current infrastructure is still set up for dirty old fossil fuels. Also, creating, transporting and installing solar panels, even on a smaller scale, pollutes to a certain degree at each stage of the process (as do most products). And then there’s real estate to be factored in, as in, where are these panels going to live exactly? Storing all that energy is costly too... All these things are having to be carefully considered in order to decarbonise the world.

Can I power my own home with solar energy?

You sure can – and there are two kinds of solar panels that can do it:

Solar thermal panels

These take energy from the sun and use it to heat water, which can then be used within your home for heating, or in baths, showers, washing machines or dishwashers. These panels can cut your heating bills, and reduce your carbon emissions – very useful.

Photovoltaic (PV) solar panels.

If you’re hoping to earn money from your solar panels, these are the ones you want. They create electricity you can use in real time to power appliances and light your home. You can then earn money back, by selling any surplus to the grid.

The majority of UK homes are suitable for solar. Just make sure your roof is strong enough to house the panels and allow enough space in your loft (or similar) to house the inverter. Getting a qualified installer to check your house before making any decision is a must.  

Want to learn more about types of renewable energy? Read our guide to biomass energy and biofuels.

If you're ready to join the green revolution, consider going solar today for a green-powered home and a green-powered planet.

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