SUSTAINABLE OVERTON
working as a community to combat climate change
THE ENERGY TOOLKIT
09. THE POST-FIT MODEL PLAN - WHAT MAKES A VIABLE SITE?
Our initial aim for Community Energy was to look at installing solar panels on community buildings to help them become zero-carbon. These types of buildings had been served well under the Feed in Tariff (FiIT) subsidy scheme and we initially believed that it would work ‘post-FiIT’.
​
Now that the FiIT no longer exists, we need a new business model. The FiT used to pay you for every unit of generation, and helped create a return on investment to pay for the capital cost of the expensive equipment. The price of solar has now reduced and without FiIT you need to have an inexpensive and well-sized system producing enough power for the building where it is located. There is more flexibility when fitting solar PV to a residential dwelling as a judgement can be made on the length of the payback (between 10 and 20 years depending on your usage and cost of system).
​
The solar opportunity
​
Only 5% of UK buildings currently have solar PV, representing a huge potential. Post FiT, you are now looking for buildings that use lots of energy – such as large refrigeration users, some agricultural operations (grain store, dairy perhaps), data centres, care homes, golf clubs, hospices, food production sites, community hospitals/trusts, large scale welding operations, maybe large auto workshops, sites with continuous pumping. The ideal model is that you use all or most of the electricity generated. Another option is a private wire, which is where one building with a great roof but not much requirement for power is next to a large electricity user – so you sell it to them, e.g. water processing plants, mobile phone/TV masts.
​
Grid constraints
​
Is there a grid connection nearby? A substation? Is there at least a basic 3 phase connection to the grid? There is only a certain capacity at various points. It is possible to look at a map of the UK, and see what the capacity currently looks like. Scottish and Southern Energy Networks (SSEN) is our provider. There are tools and maps available via their website here.
​
HOW DOES A COMMUNITY SOLAR PROJECT WORK?
For community funded projects, buildings require the correct size of roof (or ground space) to cost effectively install solar PV with the building using about 90% of the power. However, a project that can sell 70% of its energy, or possibly even 50% in some cases, to an ‘off-taker’ will make a decent return. With the growth of PPAs (Power Purchase Agreements) larger scale solar PV can still make a return. The airspace above the roof of the building is leased by the community energy company (normally for a peppercorn rent) and the solar PV systems are often installed free of charge (i.e. we raise the capital for installation). The company then sells the power to the building owner. The building gets a green cheaper source of power and the community energy company uses the income to cover its costs and contribute to a community benefit fund with what is left over.
​
Community energy companies can raise funds for installing and operating solar on buildings but only if it is feasible.
​
Unfortunately, none of ourthe community buildings proved to be viable as they did not use sufficient electricity, and in some cases the roofs needed to be replaced or were not made of material that could support the solar PV. As all the building owners/tenants were very keen on this idea, we are hoping that we can find some way of decarbonising them in the future. Fortunately, we found many other commercial buildings in the area which had a consistently large power use and a big enough roof to support this.
LEARNING POINT
WHAT MAKES A VIABLE POST-FIT MODEL?
Key requirements for a Post-FiT model:
​
-
South-facing, but could also potentially work on west or east facing – not north.
-
260-270m2 of roof top for 50kW to be viable.
-
Sloped roof is best, but can also work on a flat roof. 20-40% pitch is ideal.
-
It should be in good condition - and to remain so for the duration of the project.
-
Not overshadowed by trees of buildings.
-
Ideally built post-2000.
-
No asbestos – it is too dangerous. This was used up to 1999, so many roofs are made of this.
-
Ideally no skylights or other roof plant, e.g. air conditioning, but this could be worked around.
-
Buildings that use sufficient electricity (approx. 70-90%) of the electricity generated.
-
Ideally not listed, or conservation area.
-
No flood risks.
-
No heritage risk, e.g. not near ancient monuments.
-
No ecological risk e.g. not near SSSI.
-
Not near AoNB or National Park.
-
Good access to site.
-
No footpaths.
-
Generation matched to load, i.e. most generation used on site.
-
A good price for selling the power via a PPA (Power Purchase Agreement).
-
A long-term PPA (5+ years) – the longer the better. A 20-year PPA is possible.
-
A low price, well designed and installed system.
-
An understanding of the risks, e.g. don’t assume that there will always be inflation and that electricity prices will always go up. That is very dangerous.
There are new models that are being developed, such as ‘sleeving’. A building with a large roof space but low electricity use can set up an arrangement with an electricity company to sell power to a third party (who is a big user), or for battery storage (when the technology is better/more cost effective).
​
It is challenging to make a post-FiIT model work, but there are solutions – partnering with local councils if they have access to enough property or with housing associations where solar PV can be included as part of the planning process. Our best solution was to partner with large farms that used a consistently large amount of electricity – e.g. for refrigeration. Buildings used for food factories, chilling, or other industrial plants, printers, utilities, hotels, care homes, or hospitals could all be viable.
​
To assess the potential energy usage of the site, 12 months of electricity bills needs to be acquired, preferably showing half hour data if possible. A 5-acre farm (1.5 MW) is viable. A small rooftop is too. An 11kV connection is more than adequate for many solar PV installations. However, the assessment must be more than just on the capital costs of installing the system. A 25-year cashflow projection will be required to understand the costs and revenues over the life of the project.
​
Key requirements:
​
-
South-facing or flat roof.
-
Other roof plant, e.g. air conditioning.
-
No flood risks.
-
No heritage risk, e.g. not near ancient monuments.
-
No ecological risk e.g. not near SSSI
-
Not near AoNB or National Park
-
Good access to sire
-
No footpaths
​
For buildings you should also include:
-
Roof age – needs to have a long remaining life.
-
Other roof plant, e.g. air conditioning.
-
Roof condition needs to be relatively good.
-
Roof structure
-
Roof orientation – east- and west-facing roofs can be used.
-
East-west facing panels can be an excellent solution on flat roofs.
-
Access to roof.
-
Type of roof – sheet metal roofs are much better than tiled roofs.
-
Roof pitch – pitched roofs are better than flat roofs
A ground/field solar site (solar farm) can be most productive. The area should be sufficiently large and have proximity to power lines. This is likely to take longer to negotiate than rooftop solar, especially if it is a prominent position. Landowners also need to decide whether this is the best use of land. We were excited about these opportunities, but decided to start off with a roof-mounted solar PV project, and look at ground-mounted solar over a longer timeframe to give us time to build up experience.
For a solar farm to be viable:
-
It needs to be a minimum of 30 acres/12 hectares.
-
Near 33kV/121kV power lines and/or substation.
-
Not be overlooked.
-
Situated on land of grade 3b or below.