A guide to renewable energy systems
How to choose the right system for your home and maximise the benefits
Sunshine and warmth from the air or ground is constantly renewed. By tapping into these resources we can reduce our carbon footprints and cut the running costs of appliances, heating and hot water. Solar panels are the best-known method of renewable energy systems. Solar thermal systems produce hot water and photovoltaics (PV) generate electricity.
But as a result of the drive to encourage the adoption of low-carbon heating as a replacement for gas boilers, the awareness of heat pumps is rapidly catching up. These work by channelling and concentrating the warmth stored in the ground or in the air, operating much like a fridge in reverse, extracting the heat from the outdoors and expelling it into the home.
When it comes to solar panels, PVs are the most versatile. The electricity generated can directly power appliances, heat water in a tank or be stored in a battery. As electricity is currently the costliest form of energy, PVs can help to cut energy bills. Especially if you are able to time your greatest demand for power, to take advantage of the brightest daylight hours.
Solar thermal panels are great at delivering hot water, and they make economic sense if you have high demand. Fitting panels on a south-facing roof is best as it will receive the most heat, which is stored in a tank until it’s required. But for PVs, east- or west-facing roofs may produce as much power at the times you need it. Get a specialist engineer to carry out heat demand calculations to help you decide on the options.
Air and ground power
Heat pumps are suitable for pretty much any well-insulated house – which should include any new self-build. Because they tap into an abundance of renewable energy, you get two or three units of heat for each unit of electricity used to run the pump, so the running costs are on a par with gas. Plus, the proportion of renewable electricity supply in the national grid means the carbon footprint of a pump is much lower than a gas boiler’s.
An air-source heat pump (ASHP) is cheaper and simpler to install in most homes than a ground-source heat pump (GSHP). The latter uses a buried coil to collect heat from under the ground. GSHPs are more efficient, especially for big projects, but are more expensive to install, requiring either extensive groundworks or a deep borehole.
If your home is off the gas grid, installing a heat pump is a good choice. This is because fuel alternatives such as liquefied petroleum gas (LPG), oil or biomass are more expensive, more polluting or both – and all are high carbon.
The government has said no gas boilers should go into new homes in England from 2025; in Scotland the date is 2024. Both administrations are pushing for heat pumps to be widely adopted. By completing a self-build with an electrically powered cooker such as an induction model, you can avoid the connection fee and the standing charges for gas altogether.
The trouble with wood
Wood heating can be classed as renewable as it ultimately derives from the sun’s energy. But biomass fuel such as wood is falling out of favour for two important reasons. Firstly, although timber is renewable, it is not low carbon. There is an urgent need to capture and store carbon dioxide in our forests and soils. Burning wood releases that carbon dioxide back into the atmosphere, the opposite of carbon storage.
Secondly, there is increasing evidence that the smoke from stoves – even low-pollution ones – is harmful to health. This includes the people using the stove and everyone nearby. In London, for example, up to one third of the particulate pollution in the air comes not from diesel engines, but from burning wood. The government has already started to bring in restrictions on solid fuel burning. Many campaigners are also lobbying for these to be tightened, which could make wood-burning stoves unusable one day.
Get the right help
All renewable technologies need specialist design and installation – particularly if you plan to claim government support. Ensure your system and your installer are certified under the Micro-generation Certification Scheme (MCS), see mcscertified.com for details.