Renewable Electricity Generation and Battery Storage [Better Homes and Buildings]

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We can generate 50% of electricity needs from solar and potentially take ourselves off grid in using a mixture of systems. This is an incredible resource for an individual household and for the country to decarbonise the grid.

Here you will learn about solar photovoltaic panels and wind energy, as well as battery storage.

A few terms which are useful in reading this section:

kWp: Renewable electricity systems are spoken about in kilowatt peak, referred to herein as kWp. This is the amount of energy a system can generate in perfect conditions over a single hour.

kWh: This refers to the kilowatt-hour - the measure of energy which we are charged for by electricity or gas suppliers, which is also used to determine the amount of energy a system may generate within a period. It is also used to determine how much a battery system may store. Unfortunately, you will never be paid as much for a kilowatt-hour generated from your own renewable system as you will be paying to an energy supplier for such a measure. This is a frustrating imperfection in the system!

Photovoltaics: Solar Panels

Photovoltaic (PV) panels are by far the most common method of domestic scale renewable electricity generation. They can generate 50% of the electrical needs of a household, whilst cutting bills and generating electricity to the value of £450 a year.

They are relatively simple to install, however, the position and angle of the panels needed to achieve optimum sunlight is a key consideration. PV panels will generate most of their energy in summer, but will still generate in winter and will also generate on cloudy days, albeit at a lower output.

Annual Benefits of Solar Panels

A typical PV array would be between 2 and 4 kWp (with a single solar panel generating between 0.27 and 0.4kWp). A 4kWp system can generate around 3,800 kWh of electricity a year (UK average) and it will save around 1,500 kg of carbon dioxide per year.

Savings on the electricity bill by producing your own power (rather than buying power from the grid) is roughly £250 per annum. This figure will vary according to location and how much energy you actually use at home during daylight hours.

Pay Back Periods

Since the closure of the FIT (feed in tariff) a new export mechanism has come into force from January 2020 called the SEG (Smart Export Guarantee). This will likely pay around 5p per kWh. Thus a 4kWp system is likely to generate in the region of £200 per year SEG. A 4kWp system costs around £6,200 to install (including VAT at 5%). A £6,200 installation cost will pay for itself within 12-15 years.

Photovoltaic systems are coming down in price quickly and often overdeliver, so it is worthwhile exploring options. Some members of our community have managed to see their investments in solar pay back within 8-9 years, as panels have delivered above expectations.

Wind Turbines

Wind turbines use blades to capture energy when they are forced into motion by the wind. This motion drives a turbine which generates electricity, and the more wind there is, resultantly the more electricity there is being produced.

There are a number of small wind solutions available to homeowners. These are either pole mounted, which are 5-6kWp, or building mounted systems which are 1-2kWp.

Pole mounted systems cost between £9,000 and £30,000 for installation, but can generate up to 9,000kWh a year, annually saving 3.4t CO2. Building mounted systems are less efficient.

There are useful resources on the Energy Savings Trust on How to Measure Wind Speed and Choosing a site and getting planning permissions.

Energy Management

Managing energy as part of a renewable energy system can make a very big difference to the pay back of these systems. This is due to the difference in price which you as a consumer pay for electricity and what you as a supplier get paid by selling your electricity into the grid. If you are able to use more of the electricity you generate, then the value derived from your system is maximised.

Monitoring your energy usage in line with generating renewable energy can make a big difference and as a result you may wish to wash clothes or use a dishwasher during high output periods. You may also want to use your renewable electricity to heat your home, meaning that storage heaters or heat pumps may draw in energy during peak production periods.

It is also possible to store renewable energy through battery storage or even through electric vehicles, with the potential to then sell this energy back to the grid.

Battery Storage

Most Solar PV systems result in around 50% of energy being exported. By installing a battery you will use 80-90% of the energy created. Using the example above of a 4kWh system, you can use around £500 worth of the energy generated, meaning the pay back from selling energy would come to you more slowly and for a period closer to 12 years.You would also have to install a battery, which carries additional cost.

There are numerous battery storage providers. Getting a battery that suits the usage of your house is important. Most houses do not use more than 2.5kWh a day, therefore a battery does not need to be much larger than that requirement. The cost of installing a battery is between £4,000 and £7,500, with most only having a 10 year product warranty.

In most cases this makes installing a battery uneconomic. However, with battery storage costs falling, this is something worthwhile exploring when getting a quote for home renewable energy systems.