Beginner’s guide to Solar PV
E financial incentives for home electricity generation may not be as attractive as they once were – but it still makes sense to install technology that captures the sun’s energy. Emily Brooks explains the basics
Could installing photovoltaic panels be a cost-effective route to slashing your utility bills? Emily Brooks finds out
Thanks to a mixture of government incentives and falling technology prices, demand for solar photovoltaics (PV) boomed over the last decade. The generous Feed-in Tariffs may have gone (more about this overleaf) and a VAT hike on the products themselves (from 5% to 20%) comes in on 1st October this year – yet the allure of this renewable option is still strong, especially when combined with battery storage.
Despite uncertainty over new tariffs and VAT rates, this is an area of growth and change – not just with more aesthetically pleasing products coming to the market, but the tech industry working to improve panels’ efficiency.
A typical setup
Solar photovoltaic panels transform the sun’s energy into electricity, which is then converted from a DC current to an AC current via an inverter, to make it suitable for household use. According to the Energy Saving Trust, the average domestic solar PV system is 4kwp (kilowatt peak – the amount it will generate when working optimally) and costs about £6,200. A system like this generates around 4,200 kilowatt hours (kwh) of electricity a year in the south of England, or approximately 3,400kwh in Scotland.
Making the most of it
Certain conditions optimise efficiency. “Roof direction plays a key role in the amount of daily sunlight available. Facing south is typically best, but while this will generate the most output, an east/west split array can give you a more even spread of energy generation across the day, giving you a better chance of using more of it,” says Steve Springett, chief product officer at Tonik Energy, which supplies renewable energy as well as selling and installing PV panels and battery storage. “The angle of the roof will also play an important part: a 40° pitch is usually optimal. It’s also crucial to ensure there is no shading from nearby buildings, trees or other objects.”
If you’re building a home from scratch, then you can make allowances for the above in your architectural brief. “Considering solar when you’re in the early design phase makes a lot of sense, as you can make sure your solar electric panels are orientated and fitted as efficiently as possible,” says Steve. “There’s also an opportunity to save relative to retrofitting solar panels. Scaffolding and mobilisation make up the majority of the installation cost – the panels themselves are relatively affordable. So it’s a great opportunity to get value for money.”
Although photovoltaic panels only supply electricity, you can use them to heat hot water, too, via a product such as Immersun or Marlec’s Solar iboost, which intelligently diverts the excess electricity to an immersion heater.
The different systems
Photovoltaic panels can be mounted on the roof (easier for retrofitting), integrated within it (great for new builds), or used freestanding (a good option if your roof isn’t ideally orientated, or for listed properties). “From an aesthetic point of view, people like the panels to be as discreet as possible,” says Yen Dai, sales director at Environment Logic, who explains that the majority of self builders opt
for an in-roof system. Price-wise, he says they’re now about the same as stick-on panels, as installers have realised that in-roof is just as quick to put in. However, it does depend on the system – most products sit inside generic trays, but some companies (such as Viridian) make bespoke trays and panels that can only be used with one another, which work out as slightly more expensive.
As for the installation procedure for in-roof, “the roofer would felt and batten as if they were going to slate or tile the whole thing, then lay the eaves course plus one or two rows of tiles,” says Yen. “Then, the PV installer lays the in-roof trays, drops the panels in and fits the side flashing. The roofer then comes back to finish the tiling, which goes across the flashing to prevent water ingress.”
There are helpful new products coming through, such as Easy Roof’s extension to its tray system that will now allow Velux windows to directly abut in-roof PV installations.
Solar tiles are an interesting alternative to panels, having the advantage that they are virtually invisible, and can even pass muster in conservation areas. This comes at a greater cost, though – perhaps 50% more than a panel system. Some products are designed to work with traditional tiles, such as Gb-sol’s solar slates (as the name suggests, they are compatible with standard slates). New to the market is the same company’s collaboration with recycled plastic tile manufacturer Envirotile: together they’re making both solar and non-solar versions of the same tile.
Alternatively, PV panels can be ground-mounted in a sunny spot. New products that move to track the sun’s path can deliver an efficiency advantage over static systems. Heliomotion, winner of a Build It award last year for Best New Home Technology Product, says that its Gps-driven system can deliver 30-60% more energy per year than roof panels with the same dimensions.
Battery storage
Solar PV’S drawback is that, for many households, there’s a mismatch between when electricity is generated and when it’s needed. “Normally, you’re using energy in the morning and late afternoon/evening, but you generate it from 9-10am until late afternoon, when most people are away from home. So all you are doing is providing energy to the grid, which is not very useful, because it is cheaper to use what you have produced on site,” explains Ulrich Setzermann of Lumenaza, a software company for the renewable energy market. Adding a battery storage unit to your setup allows you to save that excess energy for later, and manufacturers include Tesla and Sonnen.
Although a battery will make the most of your solar PV panels, cost (from around £1,700-£4,000 depending on capacity) should be weighed against payback time. It will be most beneficial if you use all your electricity outside of daylight hours, for example for charging a car overnight.