Possible Alternatives

Two alternatives exist which may help make the proposal more palatable to many residents. Both alternatives cost more on a capital cost basis than SPEN’s initial proposal but Ofgem and SPEN [1] recognise that transmission operators may have to consider the socio-economic impacts of their network reinforcements at an early stage and each network operator is given an allowance to reduce the visual impact in National Parks and Areas of Natural Outstanding Beauty – to be considered on a case by case basis. Such funding, for which the customer inevitably pays, applies to this project through an allowance based on the consumer’s willingness to pay.

The present proposal calls for a new 275kV OHL from Auchencrosh to Newton Stewart and a 400kV OHL from Newton Stewart to Harker with 132kV spurs at Glenlee to Kendoon and Tongland; thus effectively creating a west-east conduit or arterial collector network to transfer excess energy from the region to where the demand exists and provide a 500MW 2-way connection with Northern Ireland.

The 400kv OHL has been sized to accommodate about 700MW of consented renewables as well as the Moyle Interconnector [24] so there will be times when, because of the disposition of renewable generation in the region and when energy is flowing to Northern Ireland, the network between Harker and Newton Stewart will be lightly loaded and other times when generating capacity flows in the opposite direction the load on the network will increase.

If the generating capacity remains limited to that consented on the 18 June 2015 then this opens up the first alternative which provides SPEN with some flexibility and many residents the opportunity for improving the visual impact and reducing economic loss. This is predicated on the fact that Glenluce and Kendoon will see the largest increase in renewable generation over the next five years or so, to over 400MW and 200MW respectively with other areas to the east of the region remaining more or less as they are today.

The first part of this proposal is the establishment of a sub-sea HVDC link of around 1,000MW capacity between Auchencrosh and some convenient point on the Lancashire coast such as Heysham. The choice of Auchencrosh, although further north and west of alternative landing points in the area, avoids environmentally sensitive regions and the need for additional infrastructure is overcome as Zone 1 is planned to receive a new 275kV network between Newton Stewart and Auchencrosh. Additionally, Auchencrosh already has a sub-sea cable which forms the Moyle Interconnector so the addition of a second HVDC converter station in this region should minimise any additional environmental impact over alternative sites.

The advantage of this proposal is that electricity flow to Northern Ireland can be taken from generation in the west of the region while flow from Northern Ireland and any excess generation in the region can go directly south through the sub-sea link to centres of demand thereby reducing transmission losses. This leaves the proposed west-east transmission network less heavily loaded to the point where it may be possible to downgrade from a 400kV super-grid to a 132kV network between Newton Stewart and Harker having between 350-500MW capacity. At 132kV, pylons are lighter, smaller and cheaper as is the rest of the infrastructure, leading to less visual impact. Furthermore, at this voltage there is greater flexibility to accommodate undergrounding as the cost escalation factor approaches unity [25] compared to the equivalent cost of a 400kV OHL network.

The second alternative retains the proposed west-east super-grid as a collector and transmission network for all the renewable generation in the region as well as providing a 2-way connection to the Moyle Interconnector. The difference, however, is that sections of the network may be undergrounded to avoid sensitive areas.

The following section estimates the additional cost of these alternatives and arrives at an annual figure per consumer that allows SPEN to recover these extra costs as well as earn a reasonable return on their investment.

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