With demand for renewable technology continuing to soar, Dan Redfern, Head of Marketing Communications at Marley, outlines the key considerations for a successful solar PV array specification.
The long-anticipated publication of the Future Homes Standard (FHS) is imminent, and it will set out that all new homes built from 2027 will need to incorporate solar PV on the roofscape. For architects and specifiers, this will mean they will need to consider the implementation of solar PV at the outset of any new build project.
There are a number of factors that should influence solar array specification for new build developments, including building regulations, site location, orientation, roof design/shape and integration with other renewable technologies. And as demand for solar is expected to grow exponentially post-FHS, architects and specifiers need to be aware of how these factors influence solar PV’s long-term energy-generating performance.
Here are some key considerations to support a successful solar PV array specification on new build projects:
1. Be pitch aware
The best pitch or angle of roof slope for solar arrays is anywhere between 30° and 45°in the northern hemisphere, but the specific pitch for any project will depend on the exact latitude. Therefore, the optimum angle for solar PV arrays on a site in Scotland will be different from a site on the south coast of England, for example.
2. Capture sunlight through optimised orientation
In the UK, the best orientation for solar arrays is south-facing, as this maximises the panels’ exposure to sunlight throughout the day. However, while south-facing panels provide the highest energy generation, they aren’t the only option. Depending on shading factors, solar PV systems on east-and west-facing roofs can also generate significant energy. In fact, having panels on east- and west-facing roofs can be very beneficial, as they will capture the sun throughout the whole day, generating power as the sun rises in the east and sets in the west.
3. Keep out of the shade
Shading can have a significant effect on the actual on-site performance of a solar array. As such, careful assessment of shading from neighbouring buildings, trees or roof projections, such as dormer roofs or chimney sacks, should be accounted for during the specification process. The Microgeneration Certification Scheme (MCS) solar PV installation standard highlights the importance of establishing a shading factor (SF) for an array. The shading factor is used, along with pitch and orientation data, to determine the expected annual output of the solar array in kWh.
Shading can be a particular issue for flat roof specifications, where gaps need to be left between rows of solar panels. However, on pitched roofs, the solar panels are all fixed on the same plane, in line with the slope of the roof. Therefore, they don’t cast a shadow on neighbouring panels and are placed close together to maximise available roof space and power generation.
Taking an integrated approach
Current regulations, and the anticipated FHS, encourage specifiers to take a holistic and integrated approach to deliver modern homes that are net zero ready. Low carbon technologies are increasingly linked together to maximise the ability to reduce carbon emissions and lower a dwelling’s energy demand.
The specification of solar batteries, to store excess energy, in conjunction with solar arrays was incorporated into the changes to the Government-approved Standard Assessment Procedure (SAP) 10.2, allowing their benefits to be recognised by current building regulations. This can be extremely beneficial in the case of a complicated roof design incorporating hips, valleys or dormer projections, or where the roof size isn’t sufficient to reach the kWp needed with solar panels alone.
As well as storing energy generated by solar arrays, solar batteries can also be charged using off-peak electricity supplied at a lower cost by the grid. The stored electricity can then be used the next day to help power the home in the normal way, or for additional electricity needs, such as charging an electric vehicle. As an additional feature, many solar batteries can also supply a property with power during a power outage.
Another way to utilise the power generated from solar arrays is through a solar PV inverter. This technology converts the direct current (DC) that the solar panel produce to alternating current (AC) for use in the home or for exporting to the grid. The specification and integration of a solar array, with complementary renewable technologies, presents the opportunity to architects to deliver modern, sustainable, low energy homes that comply with evolving regulations. It also adds appeal for modern homeowners. This is backed up by research from Legal and General that showed buyers will pay up to a 20% premium for an energy efficient low carbon home.
For more information, visit Marley’s website.