Smart grid will allow small renewables connections sooner – but there’s a catch

Small scale renewables projects will be able to feed in to Shetland’s electricity network under the new smart grid currently being developed – so long as the operators accept that there may be times when it cannot cope with the extra power.

At present the system, which receives power from the Lerwick Power Station, Sullom Voe Power Station and the Burradale windfarm, cannot handle additional power due to technical constraints. This means that, for example, public halls outside which turbines are built cannot benefit from extra revenue from feed-in tariffs.

However, according to documents published as part of the consultation process into the Northern Isles New Energy Solutions (NINES) project, which it is hoped will make the grid more flexible, network operator Scottish Hydro Electric Power Distribution (SHEPD) will soon offer dates for connection to the grid.

SHEPD states: “Given its geographic characteristics, Shetland has the potential to exploit renewable generation sources, particularly wind. There is interest in connecting this renewable generation to the Shetland distribution system. However, this generation cannot connect to the current system due to the underyling constraints. Connecting more renewable generation, which is intermittent, would exacerbate these problems.

“Under the NINES project, SHEPD will establish an active network management capability which will seek to offer renewable developers an earlier connection date. In return, they will be required to give their agreement to being constrained when the system cannot accommodate their generation. However, potential demand flexibility from other NINES project [developments] should reduce this constraint by providing demand when there is renewable resource available.”

At the heart of the NINES project, details of which emerged in November last year, is Britain’s largest battery, a one MegaWatt (MW) device being installed next to the Lerwick Power Station to help stabilise fluctuations in demand and supply.

SHEPD estimates that the battery can accommodate the connection of up to 400 KiloWatt (kW) of new small scale renewable generation. “As SHEPD gains a greater understanding of the battery’s operational performance, it is envisaged that further renewables can be connected as confidence in the system … increases. Once commissioned, it will be the largest battery in use anywhere on the GB network.”

On the demand side, SHEPD has teamed up with the SIC and Hjaltland Housing Association to install advanced storage heating and water heating in around 750 Hjaltland homes. The new storage and water heaters have been designed to use a more flexible electrical charging set-up based upon demand, weather forecasts and availability of renewables, again hopefully to reduce fluctuations. If successful, a further 250 homes across Shetland may also receive these devices.

In addition, Shetland Heat Energy and Power (Sheap), which operates the Lerwick district heating scheme, intends to extend the scheme by installing a 4MW electrical boiler which will be linked to a new 130MWh thermal store. “The new boiler and thermal store will provide the capacity to extend the over subscribed district heating scheme and will also substantially reduce the current scheme’s reliance on oil.” Power from the boiler and thermal store will come from a new 6.9MW windfarm at Gremista.

A new system to monitor the system’s behaviour and ongoing assessment of customers’ habits will be further components.

NINES is a precursor to the replacement of the diesel-fired Lerwick Power Station, the oldest part of which dates from 1953, the newest from 1983, and which repeatedly breaches emissions limits.

A new power station will have to be built regardless of whether the Viking Energy windfarm receives the go-ahead and a cable is laid to the mainland for the export of power because, according to SHEPD, the cable can only be guaranteed to operate with 98.5 per cent reliability. According to the documents the Sullom Voe power station will also need to be refurbished or replaced.

SHEPD is optimistic that as a result of NINES the new station will be able to have a peak capacity some 20MW lower than the existing 67MW, meaning it may cost £323 million instead of £408 million. However, the company insists that until NINES is fully operational this is only a provisional assessment.

SHEPD must produce a plan for the Shetland grid for electricity regulator Ofgem by 31st January 2013 and the consultation remains open until 5th September this year.