Wind turbines scattered across a landscape of fields, tree plantations and a lake

Aerial view of a wind farm at Pen y Cymoedd in south Wales, UK. Wind-generated power in the UK increased by 83% between 2015 and 2020 to provide nearly a quarter of our electricity. It's also one of the fastest-growing renewable energy technologies globally. © Richard Whitcombe/ Shutterstock

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Renewable energy and its importance for tackling climate change

Replacing fossil fuel-reliant power stations with renewable energy sources, such as wind and solar, is a vital part of stabilising climate change and achieving net zero carbon emissions.

Professor Magda Titirici, Chair in Sustainable Energy Materials at Imperial College London, offers an introduction to renewable energy and the future of clean, green power in the UK.

What is renewable energy?

Renewable energy comes from sources that replenish naturally and continually within a human lifetime. Renewable energy is often called sustainable energy.

Major sources of renewable energy include solar, wind, hydroelectric, tidal, geothermal and biomass energy, which is derived from burning plant or animal matter and waste.

Switching our reliance on fossil fuels to renewable energy sources that produce lower or no greenhouse gas emissions is critically important in tackling the climate crisis.

Clean, green or renewable - what's the difference?

Clean energy doesn't produce any pollution once installed. Nor does green energy, which comes from natural sources such as the Sun and is produced without any major negative impacts on the environment. Renewable energy refers to sources that are constantly replenished.

While there is often overlap between these definitions and most renewable energy sources can also be considered clean and green, it's not always the case.

Nuclear energy doesn't release greenhouse gases into the atmosphere, so some people consider it to be clean - providing the radioactive waste is stored safely and doesn't escape into the environment. But the uranium energy source used in nuclear power plants isn't renewable.

Smoke and steam pouring out of power plant chimneys

A coal power plant emitting smoke, steam and carbon dioxide. Fossil fuels such as coal are non-renewable resources. Burning fossil fuels contributes to climate change by releasing greenhouse gases into the atmosphere. © Peter Gudella/ Shutterstock

What's the difference between renewable and non-renewable energy?

Non-renewable energy comes from natural resources such as coal, oil and natural gas that take billions of years to form, which is why we call them fossil fuels. They are present in finite amounts and will run out, as we are using them far more quickly than they form.

When will fossil fuels run out?

Research based on 2015 data predicts that coal stocks will last well into the next century, but oil and natural gas reserves (stocks that we know we can extract from) will run out in the late 2060s. However, scientific models suggest that if we are to limit global warming to 2°C - the target agreed at COP26 is 1.5°C - over 80% of coal, 50% of gas and 30% of oil reserves will need to be left untouched anyway.

When we extract fossil fuels from deep within the planet and burn them, we can generate electricity quite efficiently. But the process releases a lot of carbon dioxide (CO2) into the atmosphere, which contributes to the greenhouse effect, global warming and biodiversity loss.

Magda explains, 'Fossil fuels brought with them immense technological progress but using them releases CO2 into the atmosphere, which acts like a blanket, trapping heat that would otherwise escape into space and causing global warming.'

Did you know?

The energy sector is responsible for almost three-quarters of the emissions that have caused global temperatures to warm by 1.1°C since pre-industrial times. 

If we continue to use fossil fuels, the effect will only worsen.

Magda adds, 'If we want to live on this planet much longer than 2050 and keep temperature levels below the 1.5°C of warming agreed to by governments around the world, we need to make some radical changes right now. We need to move to technologies that will give us the same level and comfort of living but drastically cut our emissions and carbon footprint.'

Examples of renewable energy sources

The main types of renewable energy are wind, solar, hydroelectric, tidal, geothermal and biomass. Read on to discover the pros and cons of each of these renewable energy sources.

One of the main benefits of most renewable energy sources is that they don't release carbon dioxide or pollute the air when they are used to produce electricity or heat. Greenhouse gases are emitted during the lifetime of some of the technologies - for example, during their manufacture or construction - but overall emissions are significantly lower than for fossil fuels.

Whereas some countries lack direct access to fossil fuels and must rely on international sources, renewable energy often allows countries to supply their own energy needs, a big economic and political advantage.

  • Wind energy

    Rows of wind turbines sticking up out of the sea, with coastline visible in the distance

    An offshore wind farm in the North Sea off the UK coast. Wind energy is an important renewable resource for the UK. According to analysis by Imperial College London's Energy Institute, offshore wind turbines offer the best-value option for meeting the UK's target of delivering carbon neutral electricity by 2035. But the UK's current target for offshore wind electricity production - up to 50 gigawatts by 2030 - will need to be significantly increased to do so. © Riekelt Hakvoort/ Shutterstock

    Wind power converts wind - the movement of air - into stored power by turning turbines and converting mechanical energy into electricity. Wind farms can be built both on land and offshore. They work well wherever wind is strong and reliable.

    Advantages: Wind energy is a clean, green and renewable resource and turbines can be placed on farmland with minimal disruption. It has the lowest carbon footprint of all renewable energy sources.

    Disadvantages: Like any infrastructure, there is an upfront establishment cost and ongoing maintenance fees. These are even higher if wind farms are built offshore. Turbines have a reputation for being noisy and poorly sited wind farms can be dangerous to some wildlife - for instance, if they're placed in the migration paths of birds or bats.

    How loud is a wind turbine?

    At 300 metres from a dwelling, wind turbines have a sound pressure of 43 decibels, which is between the volume of a refrigerator and an air conditioner.

  • Solar energy

    Solar panels in a field

    An array of solar panels in a field in Chippenham, UK. Solar energy is a renewable resource, and the Sun provides more energy than we'll ever use. If we could capture it all, an hour of sunlight would meet the world's energy needs for a year. © Alexey Fedorenko/ Shutterstock

    Solar power captures energy (radiation) from the Sun and converts it into electricity, which is then fed into a power grid or stored for later use. Although places near the equator receive the most solar energy, solar panels can generate electricity anywhere that gets sunlight.

    Advantages: Solar energy is renewable, clean, increasingly efficient and has low maintenance costs. Once established, it can dramatically reduce the price of generating electricity.

    Disadvantages: Setting up a solar array is costly and there are expenses involved with energy storage. Solar panels can take up more land than some other types of renewable energy and performance depends on the availability of sunlight. The mining and processing of minerals needed to make the panels can pollute and damage the environment.

    Did you know?

    China is currently leading the world in solar energy production, with roughly 35% of the global market.

  • Hydroelectric energy

    Water is held back by a huge wall creating a large lake, surrounded by tree-covered hills

    Although hydroelectric energy is renewable, it is not always considered green, as building large-scale dams can negatively impact the environment. Nepean Dam in Australia, shown here, was included in a study that showed dams are causing problems for platypuses by creating a barrier between populations. © Greg Brave/ Shutterstock

    Hydroelectric power uses the flow of water, often from rivers and lakes controlled by a dam, to turn turbines and power generators, creating electricity. Hydropower works best for regions with reliable rainfall and large, natural water reservoirs.

    Hydropower currently produces more electricity than all other renewable energy sources combined and provides around 17% of the world's energy.

    Advantages: Hydroelectricity is dependable and renewable for as long as there is rainfall or flowing water. Reservoirs can offer additional benefits, such as providing drinking water, irrigation and recreational opportunities, including swimming or boating.

    Disadvantages: Hydropower plants take up a lot of room and aren't suited to all climates. They are susceptible to drought. Creating artificial water reservoirs can harm biodiversity in natural water systems by limiting the inflow of nutrients and blocking the journey of migratory fish populations. These reservoirs can also release methane - a type of greenhouse gas - as vegetation in the flooded area decomposes. Large amounts of cement are used to construct dams. The manufacture of this material produces large amounts of carbon dioxide.

  • Tidal energy

    Aerial view of a tidal power plant that has been integrated with a bridge

    Renewable tidal energy is produced by the natural rise and fall of the sea. However, tidal power plants can change the local biodiversity. This one on the River Rance in Brittany, France, not only led to the local extinction of a fish called plaice but to an increase in the number of cuttlefish, which now thrive there. © Francois BOIZOT/ Shutterstock

    Tidal energy uses the continual movement of ocean tides to generate power. Turbines in the water turn a generator, creating electricity.

    Advantages: Tidal energy is renewable, generates no carbon emissions and can produce a lot of energy very reliably.

    Disadvantages: Offshore infrastructure is expensive to set up and maintain and there are a limited number of appropriate sites for tidal power plants around the world. They can also damage marine environments and impact local plants and animals.

  • Geothermal energy

    Lots of chimneys and steam

    A geothermal power plant in Iceland harnesses this renewable energy source. © Peter Gudella/ Shutterstock

    Geothermal power uses underground reservoirs of hot water or steam created by the heat of Earth's core to generate electricity. It works best in regions near tectonic plate boundaries.

    Advantages: Geothermal energy is highly reliable and has a consistent power output. It also has a relatively small footprint on the land.

    Disadvantages: Drilling geothermal wells is expensive and can affect the stability of surrounding land. It must be monitored carefully to minimise environmental impact. There is also a risk of releasing greenhouse gases trapped under Earth's surface.  

  • Biomass energy

    Several large round storage containers on a site with buildings and lorries

    A biogas plant producing renewable energy from biomass in the Czech Republic. © Kletr/ Shutterstock

    Biomass energy comes from burning plants, plant by-products or waste. Examples include ethanol (from corn or sugarcane), biodiesel (made from vegetable oils, used cooking oils and animal fats), green diesel (derived from algae, sustainable wood crops or sawdust) and biogas (derived from animal manure and other waste).

    Advantages: Abundant and cheaply produced, biomass energy is a novel use of waste product and leftover crops. It creates less emissions than burning fossil fuels and having carbon capture in place can stop carbon dioxide entering the atmosphere. Biofuels are also considered relatively easy and inexpensive to implement, as they are compatible with existing agriculture and waste processing and used in existing petrol and diesel vehicles.

    Disadvantages: Generating biofuels requires land and water so growing demand for them could lead to deforestation and biodiversity loss. Burning biomass emits carbon dioxide unless carbon capture is implemented.

    Did you know?

    Ethanol-powered vehicles create up to 86% less greenhouse gas emissions than petrol vehicles, and crops that are grown to produce biomass absorb carbon dioxide.

Can renewable energy replace fossil fuels in the UK?

In 2020, 42% of the UK's electricity came from renewable energy. A quarter of the UK's electricity was produced by wind power, which is the highest proportion of any G20 country and more than four times the global average. Statistics on UK energy trends reveal that from April to June 2022, nearly 39% of the UK's electricity came from renewable energy, slightly more than during the same period in 2021, but down from 45.5% between January and March 2022 when it was unusually sunny and wind speeds were high.

'There has been good news in recent years in terms of progress on renewables,' says Magda, 'but in my opinion, the UK is still lagging behind. It is not so strong yet for truly sustainable technologies. It needs storage and conversion.'

Magda believes that wind (particularly offshore), solar, green hydrogen and rapid innovation in battery storage will be key to the UK reaching net zero by 2050.

She explains, 'The UK is a really windy place, so wind is the perfect renewable energy technology. By 2035 wind and solar should provide 75-90% of total UK electricity to bring emissions down significantly.'

'It has already been shown that it's feasible to produce 90% of the UK's electricity from wind and solar combined. The tech is there and it's becoming more efficient and affordable each year.'

'Offshore wind capacity will also help produce green hydrogen, another crucial part of the UK decarbonisation path.'

What is green hydrogen?

Green hydrogen is a fuel created using renewable energy in a process known as electrolysis. When green hydrogen is burned to produce energy, it releases water.

It's predicted that the UK will need 100 terawatt-hours of green hydrogen by 2035.

What is a terawatt-hour?

A terawatt-hour is a unit of measurement that's large enough to describe the annual electricity needs of entire countries. For scale, one terawatt-hour is equivalent to burning 588,441 barrels of oil.

The future of renewable energy in the UK

Magda believes the UK is at a very critical point in its sustainable technologies journey.

'Everything will depend on what happens this year and next. We need to see radical changes, investment, subsidies and support to reach our target of net zero by 2050.'

'It would cost less than 1% of GDP to get to net zero by 2050 but the advantages would be immense: new jobs, a sustainable economy and a healthy and resilient society.'

Logo featuring a yellow car, power cable and socket painted onto tarmac

An empty electric vehicle charging point © Tony Skerl/ Shutterstock

Challenges and opportunities for renewable energy in the UK

One of the biggest challenges the UK is facing right now is battery storage and access to materials like cobalt and lithium, which are needed to produce lithium-ion batteries at scale.

Why are batteries important for renewable energy?

Batteries help make renewable energy supply reliable and portable - such as in the case of electric vehicles.

Batteries are an important part of our transition to renewable technologies, as they allow energy to be stored and released as needed. For example, solar panels generate energy during the day, and batteries make it possible to store and use that electricity at night.

Currently, just a few countries are responsible for most of the world's production of lithium.

According to Magda, the UK lacks access to the supply chain needed for Li-ion batteries. 'As a result, she adds, 'Johnson Matthey, which is a major company driving battery innovations in the UK, announced they would stop lithium battery research because they are unable to secure a path to raw materials and be competitive on the international market.'

Museum researchers are investigating whether it would be possible to develop a more sustainable, domestic supply chain by extracting lithium from UK rocks. They made a key breakthrough in 2021 when they produced battery-grade lithium chemicals from UK rocks for the first time.

According to Professor Richard Herrington, Head of Earth Sciences at the Museum, 'An increased, reliable supply of lithium is critical if we are to meet the rising demand for electric cars and provide a dependable supply of energy from renewable sources. The next generation of batteries that don't require lithium may still be three to five years away from being ready for public use.'

However, Magda is optimistic that the UK could lead in emerging battery technologies. 'I think the UK has an amazing opportunity to pioneer the next generation of batteries,' she says.

Innovative models already under development at The Faraday Institution include:

  • Sodium-ion batteries, which are based on waste-derived anodes and critical metal-free cathodes, provide almost the same performance as lithium-ion batteries at half the cost.
  • Lithium-sulphur batteries with 10 times the energy density of lithium-ion batteries make more efficient use of limited materials and eliminate metals from the cathode by using sulphur instead.

Magda adds, 'We need to focus on the areas where the UK has the potential to lead. The UK has such a big tradition in new materials and discoveries, we could move to completely new technologies both for batteries and hydrogen production.'

'There are a lot of challenges, but if we're investing in it, we could be future leaders and even solve one of the most difficult challenges in decarbonisation: flight.'