One of the most interesting presentations at this year’s Solar Energy U.K. show that concluded Thursday in Birmingham was about the “Sunshine Tarriff” project in the South West England county of Cornwall.
Tamar Bourne, of the South West Renewable Energy Agency (Regen SW), an independent, non-profit organization, told the audience that grid capacity in South West England is currently exceeded, prohibiting the expansion of renewable energies. “In the last six months, we found that any connection for distributed generation will face a delay between three to six years,” Bourne said.
The community of Wadebridge and surrounding villages in Cornwall, however, have organized the Wadebridge Renewable Energy Network (WREN), which is making strides in promoting renewable energy in the area, Bourne explained. The network’s more than a thousand members are rolling out many micro-installations, mainly solar PV, and the area is among the country’s top destinations for solar PV installations.
WREN is seeking to make it operating region go 100% green and is looking to build a large-scale solar PV farm. The network’s members initially decided to build a 5 MW ground-mounted project, found the site and the funds, but due to the grid’s thermal and voltage constraints in their area, they were told to reduce their plans down to about 500 kW. They changed the business model and tried again, only to have the distributed grid operator of their area tell them they could only go ahead with a 100 kW farm, and eventually that they could not proceed with it at all due to grid constraints. The uphill effort has taken the community about four years and £15,000 to £20,000 in consultancy and other planning fees.
Offset connection: The trial
The only solution to the problem would be to change the relationship between power generation and consumption. Thus, the community is now trying to shift the power demand pattern and incentivize daytime power consumption so that the generated power from the solar farm is consumed when generated and not needed to be exported via the grid.
The traditional way of connecting a PV farm to the grid is via timed connection, said Matthew Watson, an engineer at local DNO Western Power Distribution. In this case, PV power generation is often curtailed due to power constraints. Eventually, if the curtailment is very frequent, the business case for the project is not viable.
The alternative to this is the so-called “offset connection,” whereby PV power generation in the distribution grid is only curtailed when it’s not offset. In other words, “if you can absorb extra generation locally then there will be no net effect on constraints at higher voltage levels,” Watson said. Hence, the idea for a “sunshine tariff” that incentivizes customers to use more electricity during daytime.