The present grid is designed to transmit electricity in a straight line, from producer to consumer. The implementation of renewable energy in commercial and domestic environments has, however, led to the emergence of another party who produce, consume and possibly sell their own energy – the prosumer. When the prosumer’s renewable energy is fed back into the grid – causing electricity to flow in the other direction from the one originally intended – high voltages and transformer overloads can occur in under-reinforced parts of the grid network as a result of grid bottlenecks.
To resolve this issue, logic would dictate that the new installations should be connected to a more robust part of the grid; limitations on the amount of power being fed into the grid at certain times should be imposed (known as ‘curtailment’); or reinforcements be made to the network itself, to allow it to accommodate the added power. However, it may not be practical to connect a new generator to a stronger part of the grid, curtailing the power being fed into the grid from renewable sources wastes that ‘excess’ energy, and reinforcement (by doubling the existing circuit along the feeder; adding a new transformer to an existing line; or building a whole new line) can prove expensive.
While “distribution grids can already take up significant amounts of PV electricity with little to no grid adjustments”, the growth of renewable energy relies on the ability of the energy distribution network to accommodate the energy being fed in from renewable energy sources. A lack of planning, or an underestimation of the expansion of that country’s renewable energy industry, can result in “sub-optimal situations in network operation… A forward-looking policy is needed to ensure that Europe’s decarbonisation strategies will be supported by a corresponding vision of grid evolution” Similarly, in the U.S., “investments must be made in grid and transmission infrastructure to account for an increasing share (up to 30%) of variable renewable power [by 2030].”
“The absence of long-term grid planning for integration of small systems leads to bottlenecks that otherwise might have been avoided if measures were taken beforehand.” As a result of this absence, management of the grid in its present state is becoming “more and more challenging for distribution system operators”
The urgency of expensive grid upgrades can, however, be delayed or minimised through the implementation of alternative solutions. Four of the most viable alternatives are: energy storage products (Distributed Energy Resources); Demand-Side Management (DSM); localised energy consumption (microgrids); and mixed energy installations.
Curtailment has been a route taken in various countries across Europe, and has been identified as a “growing concern”. Moreover, “utilities that are signing long-term contracts for wind and solar may want to consider who bears the curtailment risk during the lifetime of the contract”