Renewable energy is created from natural resources that are unlimited or continually replenished, such as the sun, wind and water.
Renewable electricity involves no fossil fuels in its creation and produces zero carbon dioxide emissions when it is generated.
42% of the electricity in the National Grid comes from renewable sources, according to government figures for September 2023.
Types of renewable energy
Wind and solar account for a large proportion of renewable electricity generation in the UK, but hydroelectricity and bioenergy contribute as well.
Nuclear power is a low-carbon power source too, though it's not renewable.
Some sources of renewable power are intermittent, meaning they are only available in certain conditions such as when the wind is blowing or the sun is shining.
Wind power is the second-largest source of electricity in the UK and the most efficient renewable form of energy. It produced 21% of the electricity generated in the UK in the second quarter of 2023, according to government figures from the Department for Energy Security and Net Zero (DESNZ).
When wind spins the propeller-like blades of a wind turbine, it turns a shaft inside the turbine. A generator then converts the kinetic energy of the shaft turning into electrical energy.
Wind turbines don’t need much wind to turn them - a gentle breeze (around three to five metres per second) is sufficient.
In the second quarter of 2023, the generation of electricity from wind power was down 16% on the year prior despite an increase in capacity for both offshore and onshore windfarms, due to unusually low average wind speeds.
More of our wind power comes from offshore windfarms than onshore wind farms, and that gap is extending year on year. In March 2023, the government increased its ambition for offshore wind deployment to 50GW by 2030. For context, the UK currently has 13.9 GW of offshore wind fully commissioned.
Solar energy
Over 8% of electricity generated in the UK in the second quarter of 2023 came from solar photovoltaic (also known as solar PV) systems, an increase from around 6% in 2022.
Solar panels use PV cells to convert the sun’s energy into electricity. The panels can generate electricity as long as it’s light, but the stronger the sunlight, the better they will work.
Hydroelectricity, alongside wind and solar power output fell in the second quarter of 2023, despite an increase in solar output thanks to increased capacity and more sun hours. This was due to less favourable weather conditions for wind and hydro generation.
Hydropower includes:
Run-of-river - Water in a river or canal is channelled continuously to spin a turbine
Storage - Water is stored in a reservoir using a dam, and released to spin a turbine and generate electricity
Pumped storage - Water is cycled between an upper and lower reservoir using pumps powered by surplus energy from the system. Water is released into the lower reservoir to generate electricity.
All of these involve water spinning a turbine to activate a generator and produce electricity.
Wave and tidal systems use currents or the power of waves to generate electricity from seawater.
Bioenergy and landfill gas are the source of a third of our renewable energy although they’re lesser-known sources classed as renewable by the government. Bioenergy includes generation from:
Anaerobic digestion
Animal biomass
Energy from waste
Plant biomass
Sewage gas.
Bioenergy isn’t as efficient a renewable source as hydro, wind, wave and solar. Much of the energy content of the fuel is lost in the process of burning it to generate electricity.
Anaerobic digestion
This breaks down organic matter without oxygen. The organic matter is often food waste or animal waste and is broken down in sealed tanks, producing biogas.
Biogas is then used as fuel in a combined heat and power unit to generate electricity and heat.
Biomass energy
Biomass energy involves burning wood, plants and other organic matter (including manure and household waste) to create steam, which spins turbines and generates electricity.
It can be considered renewable if the plants or other organic materials burned are from a sustainable source and are replaced, removing carbon dioxide from the atmosphere and storing it. Some biomass plants have carbon capture and storage technology to stop carbon released during burning from being released into the air.
Some big generators, including Drax, have converted coal power stations to biomass and burn wood pellets.
There are concerns about the sustainability of wood biomass, however. It releases greenhouse gases when burnt, which can sometimes be higher than burning gas or coal, depending on the type of biomass burnt and where it comes from, according to UK government research.
In 2021, the UK imported around 9 million tonnes of wood pellets for renewable energy production, with over 75% coming from the US or Canada. Transporting this has associated emissions.
Energy from waste
Energy generated from waste usually takes residual waste (what’s leftover after recycling) and turns it into energy, including electricity.
There are various ways to do this, but burning it is most common. The government considers it partly renewable because only energy generated from biodegradable materials (such as food, paper and wood) is renewable. Burning oil-based products, such as plastics, is not.
Plants must clean up any waste gases before releasing them to meet pollution limits.
Landfill gas
This is produced as organic material rots, is mainly methane and carbon dioxide.
This can be collected and used to turn turbines to generate electricity.
Sewage sludge
Sewage sludgecan be used to generate electricity (and heat), too.
The sludge is treated using thermal hydrolysis to increase the amount of methane it can produce. Then it is broken down by anaerobic digestion, producing biogas.
Geothermal energy
Geothermal energy is a source of renewable energy due to its low environmental impact.
It is created using heat from the earth's core, which is continually produced. Geothermal energy comes from heat generated during the original formation of the planet and the radioactive decay of materials. The energy is stored in rocks and fluids in the centre of the earth.
Wells that are around a mile deep or more are drilled into underground reservoirs to tap into the geothermal resources.
Geothermal energy is constantly available because heat is continuously produced inside the earth.
It can be used for bathing, to heat buildings, and to generate electricity.
What is the best type of renewable energy?
Figuring out the best source of renewable energy will depend on which one is right for you and your household's energy use.
The best type also comes down to which factors you prioritise, which could be your budget, energy efficiency or reducing your energy bills, so there's a lot to consider.
Some types of technology have specific requirements for installation. For example, solar photovoltaic (PV) and solar thermal systems will depend on the way your roof faces, solar thermal, heat pumps and biomass require space inside and outside your property, while hydropower systems require a nearby stream or river.
Once you've narrowed down the technologies that are suitable for your property, you can then rank them based on how well they would perform for your needs. The Energy Saving Trust recommends you consider the following questions:
Are you hoping to replace your current heating system?
Are you looking to save energy and make your home more sustainable, or looking for which technology could save you the most money?
Should the system provide all your energy needs, or will it work in support with another?
If you need to replace your boiler or central heating system, this is an opportunity to move away from a fossil fuel heating system like a gas boiler. Should your priority be to save carbon dioxide, consider a heat pump, a large wind turbine or large solar PV system.
If you live in an isolated rural property with no mains electricity, you may get the most reliable off-grid supply from hydro or from a mixture of wind and solar PV.
You should also weigh up the products that are available, their costs, the size of systems and any special requirements for installation before reaching out to installation providers.
Renewable energy is a way for consumers to up their green credentials as they do not directly produce any pollution. Renewables will not run out, can reduce environmental waste and tend to have lower maintenance requirements.
Plus most energy generators, such as wind turbines or hydroelectric power stations are pricey to set up but cheap to run.
Renewables are being heavily incentivised for companies and members of the public by the UK government too. It revealed its Contracts for Difference (CfD) scheme in September 2021 to encourage investment in low-carbon electricity.
This is open to projects operating in Great Britain and, for this fifth allocation round (AR5), comes with £227 million worth of investment to developers of projects with high upfront costs and long lifetimes with protection from volatile wholesale prices. and comes with £227 million worth of investment to. The government said the CfD scheme will ensure consumers don’t pay increased costs when electricity prices are high.
As for consumers, the government introduced the Boiler Upgrade Scheme in May 2022, offering grants of up to £7,500 towards the cost of replacing your traditional boiler with a low-carbon heating system such as a heat pump.
But renewables have high upfront costs and can be intermittent, with sources such as wind turbines and solar cells rely heavily on the weather. For instance, if it is not a windy day, wind turbines will not turn, and if it is not sunny, solar cells will not produce much electricity.
