Learn More about Renewable Energy
Renewable Energy comes from sources that are not permanently depleted by their use – in other words, they are naturally renewed. This means that we can extract energy from such sources, convert it into a more useful form such as electricity or heat, and still be confident that there will be energy left for future generations to use. What’s more, all forms of renewable energy are low carbon, are they do not require burning fossil fuels to generate the electricity or heat. As a result, renewable energy has a much lower impact on the main causes of climate change.
What are the main sources of Renewable Energy?
There are seven main sources of renewable energy:
- Energy from running water
- Energy from the wind
- Energy from the sea (tides and waves)
- Energy from the sun, used directly
- Energy from growing plants
- Energy from near the ground’s surface
- Energy from deep underground
Energy from running water is known as hydro-electric power. Rainfall naturally fills reservoirs or lakes that are dammed, and then water passes through turbines to generate electricity. This is a reliable way of generating large amounts of electricity, but can only be used in a few places – it is difficult to build new large hydro schemes, partly because large schemes may need to flood valleys. Smaller schemes are possible, including generating power from old mill ponds or using existing weirs on rivers.
We are probably all familiar with energy from the wind as the UK has become one of Europe’s leading countries for wind turbines. These are an excellent way of creating electricity but, as a rule of thumb, doubling the size of the turbine increases the power output by a factor of four. As a result, micro wind turbines on buildings are not very effective and it is better to buy wind energy generated from large turbines, such as that supplied through the Green Energy Supply Certification Scheme. As many people are concerned about the visual impact of large turbines in the windiest parts of the country, an increasing number are being built offshore, where there less disturbance.
The other offshore renewable energy sources are wind and waves using techniques with exotic names such as snakes, ducks, buoys and oscillating columns. Although these have a huge potential to generate large amounts of energy for the UK, at the moment most schemes are still at a pilot stage, and some of the early test schemes were destroyed by the sheer force of the ocean. Experts think that this may be a major part of UK energy resource by 2030, but it’s not currently able to provide much electricity for the grid.
It is possible to directly convert the sun’s energy to electricity, using photovoltaic cells (commonly called PV). Although this is probably the best way to generate electricity at home, the cells are still rather expensive and cannot compete with other forms of renewable electricity without needing significant subsidies or feed-in tariffs. There are a few “solar farms” with large arrays of PV cells, but these work best in sunnier countries than Britain. The sun’s energy can also be used to warm water in solar thermal panels, and these are a good way to gut down on your domestic hot water costs.
The sun’s energy can also be trapped on the surface in a number of ways, and indirectly used to provide energy. The easiest way is simply by growing plants, and then using the energy stored in those plants (known as biomass) to provide heat or electricity. There are a number of plants that can be specially grown for biomass in the UK, including coppiced trees like willow or poplar, and annual crops such as switchgrass or miscanthus (elephant grass). Biomass can also be produced from waste wood, such as compressed sawdust. In most cases the crops have to be processed to produce wood chips or pellets and can be burned for heat or electricity, often in a combined heat and power plant. Although CO2, the main gas responsible for global climate change, is given off during combustion, it is broadly matched by CO2 captured by the plants during their growing phase.
A less well known form of capturing the sun’s heat is through collecting solar energy stored in the ground (or a body of water), using a heat pump. This is an excellent way of heating larger homes, but cannot be used to generate electricity. This is different from geothermal energy, which is not strictly renewable but almost limitless in quantity, where steam can be raised to drive turbines generating electricity by passing it through hot rocks heated from the earth’s core. This is only practicable in a few places where hot rocks are reactively close to the surface.
Why don’t we only use Renewable Energy?
You may be thinking that if renewable energy is both plentiful and clean, why do we not use it all of the time? The difficulty with many forms of renewable energy is that is it is less concentrated that dirtier forms of energy such as oil, coal or nuclear power, and so often costs more to convert into electricity or heat than burning fossil fuels. (If all external costs are included, most forms of renewable energy are cheaper than nuclear power.) And although the sun and the wind could readily provide all the UK’s needs, there have to be ways of storing it for use on quiet nights (such as pumping water up into reservoirs) and these too can add to its cost.
Which forms are Renewable Energy are available in the Green Energy Scheme?
Each member of the Green Energy Supply Certification Scheme can tell you about the mix of renewable energy in their electricity supply. But most of the energy will come from a either wind or hydro, with smaller amounts of biomass.
Members of the Scheme also have to invest in additional measures, and some of these are through investment in green funds or purchasing carbon offsets. Green Funds typically invest in smaller community-scale renewable energy schemes in the UK, including providing biomass boilers or ground source heat pumps for schools and PV or solar water panels for community buildings. Carbon offset schemes work internationally, and typically support wind projects or the provision of efficient cooking stoves in Africa that not only lower CO2 emissions but also improve air quality.