Land is precious, so where large scale ground based solar is needed, we should require that its “dual-use”. This includes combining energy production with infrastructure, agriculture, biodiversity or, at the very least, the improvement of soil health.
The top priority is for the majority of UK buildings and infrastructure to have PV. This maximises transmission efficiency, reduces the demand on National Grid, optimises the use of land and encourages the occupants to optimise their use of PV.
However where ground mounted PV installations are a necessary part of decarbonising the UK’s electricity supply, these must either be on land that’s managed for dual use: ie Energy and Infrastructure, Energy and Agriculture, or Energy and Habitats.
Dual agricultural and energy use, known as Agro-voltaics (also agri-voltaics)
Agro-voltaics[i][ii][iii]is a relatively new combination of agriculture (typically vegetable growing , sheep or poultry) and ground mounted solar panels. It is being used in USA, Japan, China, South Korea, India, Malaysia, Vietnam, Austria, Italy and France, while the UKRI is already funding innovation[iv] in agro-voltaics in Cambridgeshire.
A variety of approaches are being used. These are very site specific, but typically, they benefit agriculture (because some shading by the panels reduces crop overheating and water use) while the efficiency of the panels is improved by up to 10% because cooling induced by transpiration by the crops improves PV efficiency. To enable this the panels are typically at a wider spacing than normal and may be mounted higher than normal in order to allow workforce and machinery to move underneath. Although solar output maybe slightly lower, overall productivity can be improved[v].
Research suggests that for success, agro-voltaic projects need to have agriculture at their heart.
Cambridgeshire is the UK’s most important region for growing vegetables, but productivity is under threat:
The East of England is the hottest and driest part of the UK. Cambridge has already seen the highest UK temperatures (38.7C in 2019), water supplies are already dangerously depleted, and soils are degrading. Climate change will make this worse, so innovative approaches are important.
We suspect Solar Farm operators are unlikely to embrace an agro-voltaic approach unless it is made a legally binding obligation. Where the land quality permits it, we would like to see this made a requirement of planning permission, along with evidence of the involvement of a skilled and engaged farmer.
This would promote UK focussed innovation in this nationally important area.
Improving Biodiversity, natural habitats, soil health, carbon sequestration and woodland
In most solar farms, the biodiversity benefits go no further than nice pictures of wild-flowers on the website, while on-site, plant growth is vigorously supressed with herbicides, mowing and even gravel. However, organisations such as Wiltshire Wildlife Trusts and RSPB are showing what can be done, when the project has biodiversity enhancement at its heart [vi] [vii] [viii]
Taking land out of intensive agriculture for a period offers a substantial opportunity to rebuild soil health, sequester carbon, increase biodiversity and improve natural habitats. Although we are not experts in biodiversity, where the land is not suitable for agrovoltaics we would like to see a legally binding obligation on solar farm operators to significantly improve biodiversity and habitats, where the land is appropriate for this.
Cambridgeshire is the least wooded county in the country[ix], so thick hedges and appropriate height trees should be planted round the edges of the scheme and in areas not used by the panels. This will help improve biodiversity, sequester carbon and reduce the visual impact of the huge scheme on the local community.
Experience shows that although most local solar farms have over-promised and under-delivered on habitat creation, these approaches yield good results when done with conservation at heart.