Renewable energy explained

What is renewable energy?

Renewable energy is a bit of a misnomer – you can only change energy or use energy – it can’t be created or destroyed. Renewable energy is a term used to describe energy derived from resources which are naturally replenished during a human timescale. Renewable energy sources include solar power, wind, water, the sea, and geothermal from underground.

What is the alternative energy?

Alternative energy is just another way of describing renewable energy. Solar power converts the energy from the sun’s light into electrical power. Wind power, wave power and tidal power all harness the kinetic energy of these natural phenomena and convert it into electricity. Hydro power converts the potential energy of water running downhill into electrical power. Geothermal, ground source and air source heat pumps all use the heat energy contained in the air around us and the ground we walk on, concentrate it and store it for later use.

What is green energy?

Green energy is also another name for renewable energy, sustainable energy or alternative energy. Green has become a bit of a catch-all word to describe anything with an environmentally sensitive approach. Hence, the Green Party, green movement, green lifestyle, green energy – such as our Green plan.

Green energy would usually include green electricity and green thermal, but may also include green gas, bio-gas or bio-methane.

What is solar power?

Solar power comes from the sun. It’s captured using photovoltaic (PV) panels and solar thermal panels. Solar panels convert the sun’s energy into electricity which can be used immediately to power your household appliances, stored in batteries to use later, or converted into heat and stored in a hot water tank for example.

While these technologies are relatively new, humans have been using stored solar energy to heat and cook with for thousands of years. One of the most efficient solar energy storage plants is just that – the tree. Solar energy is converted in the tree’s leaves and combined with carbon dioxide (CO2) and other elements to be stored as wood, which is then released when that wood is burned. Coal and oil use the same stored energy, but the wood, plant and other organic matter is converted over millions of years into coal, gas and oil. When people talk about carbon emissions from burning fossil fuels, they principally mean this carbon dioxide. The challenge is that the carbon which the plants captured over millions of years and stored as fossil fuels is being released over a very short timescale which puts pressure on the environment. 

Solar thermal or solar hot water captures the sun’s energy and converts it into heat which can then be concentrated in a hot water tank for use later.

What is green gas?

Green gas is methane produced and captured from the composting of organic matter – usually waste.

Unlike the compost heap you might have at home, bio-gas is produced by different microbes in a closed system which keeps the air out. This is called an anaerobic digester (AD).

The microbes digest the organic matter that’s put into the AD, and produce bio-gas as a by-product. This bio-gas is mainly methane – the same gas as North Sea gas which you burn in your boiler or gas hob at home. At the end of the digestion, the matter that’s left can be used as a rich fertiliser and spread on the land by farmers. In fact, anaerobic digester systems are often built on farms as a more productive and sustainable way of handling farm waste and slurry from cattle. The benefits to the farmer can be substantial: a better, less smelly, more neighbour-friendly method of dealing with slurry, income from feeding the bio-methane into the grid or using it to power a combined heat and power unit (CHP), the feed in tariff (FiT) income from electricity generated being fed into the grid, cost savings from the reduced need to purchase commercial fertilisers and income from selling excess fertiliser to other farms.

How do heat pumps work?

Renewable ground and air source heat pumps work just like the fridge in your kitchen, only inside out. If you’ve ever felt the air at the back of your fridge you’ll know it’s often quite warm. This is because the fridge’s compressor mechanism enables it to take warmth from inside the fridge and releases it into the room. So, in practice, the small space inside the fridge cools down a lot and the large room it’s in warms up a tiny bit. Now, if you reverse this concept, you can see how you could take a little heat from the air outdoors (even when it’s quite chilly) and use that heat to warm up the space inside your home.

What is a CHP?

A combined heat and power unit (CHP) is a large electricity generator, usually gas turbine powered. CHPs range in sizes from a little larger than a domestic gas boiler in your home to the size of a bus station. They are increasingly being used in new housing or business park developments as they are significantly more efficient and less polluting than having individual boilers in every home or unit.