The Sparse Grid

‘Sparse grid’ is a term that DistGen has coined to describe a particular set of circumstances applying to the electrical distribution grid in a particular place . It relates mainly to the supply constraints imposed by the physical transmission capacity of the grid between the nearest significant generating capacity and a particular group of consumers but also includes other operational aspects such as metering and control infrastructure.

According to our definition, the grid is ‘sparse’ where implementation of significant new generation capacity is constrained by the grid’s capabilities at that location. At the sparse end of the spectrum, islands represent the archetypal situation where no connection between the island and a large generating capacity exists – all electricity therefore has to be generated locally using whatever technology makes economic and technical sense. As one might expect there is a growing recognition among island communities that local renewable generation is the only economically viable route for future electricity generation. Perhaps surprisingly, however, even in heavily populated industrialised countries where one might expect a dense grid, there are large numbers of sparse grid locations.

There are three possible responses to the sparse grid situation: implement no new generation capacity, upgrade the grid to cope with the new capacity or implement a solution that operates within the limitations imposed. The first response fails to satisfy any new demand that has arisen and therefore condemns the consumers in that area to constrained supply. Upgrading the grid to overcome the sparse grid limitations is a viable solution but the required investments can be prohibitively expensive and generally only make sense for very large implementations e.g. utility scale wind farms where the grid upgrade costs can be amortised over a big generating capacity.

DistGen’s sparse grid solution, the Distributed Wind Farm, is based on the third response, the delivery of a ‘Goldilocks’ sized solution – just right, big enough but not too big. Big enough means that it is capable of supplying enough of the local demand to obviate a grid upgrade. Not too big means that the additional capacity is within the capacity of the local grid to handle.