Isle of Eigg, Inner Hebrides, Scotland

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Eigg SunResidents of the Isle of Eigg now have 24 hour a day electricity powered by renewable energy. On 1st February 2008, the tiny Scottish island was connected to it's own mains electricity supply for the first time - "Eiggtricity" as it has been dubbed.  Wind & Sun engineers returned for the big “switch on” and celebrations.  The beginning of June saw a community celebration, in which the system was handed over from the contractors to Eigg's own electricity company 'Eigg Electric', who will be responsible for operation and maintenance.

2008 has seen the Hebridean isle of Eigg literally come out of the dark ages, with one of the greenest power schemes in the country, a £1.5m solar, wind and hydro generating station.  Eigg residents have gone from lacking a technology that defines the modern age, to possessing one that the rest of us are still struggling to develop. It is an inspiring example.

Batchedeigg SgurrArticles before the 'Switch on':

Articles about the 'Switch on':

About the Island

Batchedeigg HandoverThe Isle of Eigg, at 8km by 6km, is the second largest of The Small Isles 10 miles off the Western Coast of Scotland south of the Isle of Skye.

With 87 inhabitants, it is also the most populous. Eigg boasts a wide variety of coastal scenery, ranging from beaches and spectacular cliffs, to historic caves.

Eigg is best known as the island which became an emblem of the land reform movement when it was the first successful community buy-out. In 1997, after decades of mismanagement by absentee landlords, the island was bought by the Isle of Eigg Heritage Trust, a partnership between the residents of Eigg, the Highland Council, and the Scottish Wildlife Trust.

Visit for more information.

The Project

Batchedeigg Pvpanels1 JuneThe Isle of Eigg was not served by mains electricity, with most properties relying on ageing diesel generators for power. The Isle of Eigg Heritage Trust and Eigg Residents chose to pursue the installation of a mains type system to supply reliable and affordable electricity to all properties on the island.

Listen to the BBC audio link which describes the background to the electrification project (RealPlayer required).

The Isle of Eigg Electrification project is an attempt to develop a electricity supply for the island which is sustainable both environmentally and economically. The Isle of Eigg Heritage Trust formed a company, Eigg Electric Ltd, to procure and operate a mains-type electrical network system for the islanders, to provide an electrical supply similar to that enjoyed by people living on the mainland with the aims of the generation of predominantly renewable electricity and the supply of a reliable 24 hour electricity supply for all islanders. This scheme will provide encouragement for operators of other isolated off-grid systems to adopt these technologies, both in the UK and overseas. It will also demonstrate that high proportions of renewable energy can be accommodated within distribution networks, encouraging attempts to integrate increasing proportions of renewable energy into existing networks to help the UK achieve its CO2 reduction targets.

Batchedeigg Generators December 2007Various renewable sources distributed around the island have been incorporated to allow diversity of energy supply, - a 9.9kWp PV system, three hydro generation systems (6 kW, 6 kW & 100 kW)  and a 24 kW wind farm supported by standby diesel generation and batteries to guarantee continuous availability of power. There are currently 37 permanently occupied residential properties and 5 commercial properties on the island which will be connected using a high voltage three-phase distribution system. Load management will be used to ensure optimal use of the renewables.

Overall design of the complete system was by Econnect Ventures who have unique expertise in the design and operation of off-grid islanded networks containing high proportions of renewable energy, including the use of load management to optimise the utilisation of renewables.

Batchedeigg Hydro TurbineWind & Sun worked with Econnect Ventures and designed the battery inverter and PV systems.  Synergy Scotland managed the electrification project using Scottish Hydro Contracting as main contractors and Wind & Sun worked for them as specialist sub-contractors.

In January 2007 we undertook the installation of the PV array, battery store and Sunny Island inverters. Installation of the island grid was carried out by Scottish Hydro Contracting over the summer months, which involved the laying of several km of cables together with the associated transformers and switchgear as well as the updating and testing of the wiring to all the properties on the island.  G.G.Mackenzie Contractors Ltd undertook all the groundworks and laying of cables.

Batchedeigg Laig Hydro WeirScottish Hydro also installed the new 100kW water turbine, pipeline and weir.

The inverter system and diesel back-ups were commissioned by Wind & Sun in December, allowing electricity to be available throughout the island backbone just before Christmas.

The integration of the hydro generation, the wind turbine installation and the monitoring followed shortly after.  Power was switched onto the island on 1st February 2008.  

The Battery & Inverter System

Batchedeigg Sunny Islands December 2007The main battery inverters are the heart of the system and provide a reference grid to which all loads and generation is connected. They control the system voltage and frequency, and manage the balance between loads and generation by controlling the power into and out of the batteries.

Additional system control will be provided by load management at times of high renewable generation.

Twelve Sunny Island SI-5048 5kW inverters are used connected in four three phase clusters to give a total output rating of 60kW.

A MultiCluster Box MC-Box-12 is used to combine the cabling from each of the Sunny Island inverters and provides contactors for the connection to the island grid and the back-up generator.

Each cluster is connected to a 48V 2242 Ah (C10) battery bank consisting of 24 Rolls Solar RB 4KS25PS batteries fitted with Hydrocaps to reduce maintenance.

Total energy storage is approx. 212kWh to 50% DOD.

Batchedeigg Multicluster Box OpenImage1Image2









The PV Array

Batchedeigg Pvpanels JuneThe main benefit of the PV array will occur during the summer months when its output is high, complementing the lower output that is expected from the hydro generation and the wind turbines (due to low summer rainfall and low summer windspeeds). Because of the uncertainty regarding the load profile and the intermittency of the renewable sources, diesel generation will provide backup power to ensure a reliable supply for the island is maintained.


Batchedeigg PanelsbackThe PV array is located close to the power house which houses the batteries, inverters and standby diesel generators. It consists of 60 BP Solar BP3165S PV modules mounted on an aluminium ground mount support frame. They are wired in six series strings of 10 modules with three pairs of strings each connected to an SMA Sunny Boy SB-3000 inverter.

The PV array is connected to the low voltage side of the AC network via these grid-connect inverters. This will allow the PV output to feed the island loads directly. Surplus output is stored in the batteries.

A new 22 kWp PV array was added in April 2011 to increase generation over the summer months.

Read more

Wind Turbines

Batchedwind Turbines On EiggFour Proven 6kW wind turbines on 15m towers each connected to SMA Windy Boy WB-6000A inverters are sited at the Southern end of the island where the best wind exposure is obtained.

These were installed by Energy Renewed Ltd a local Proven installer based in Aberdeen who were well placed to deal with the logistics of getting the equipment to the island and the construction there.






A Sunny WebBox is used to monitor the Sunny Island & PV system allowing performance to be recorded and viewed remotely over the internet.

Eigg Sunnyportal

Graph showing power output of PV array, diesel generator power and power of each Sunny Island master inverter. NB This was for days with little hydro and wind power.

Eigg Sunnyportal Battery

Graph showing battery state of charge for each of the clusters for the same days as above. Work on monitoring is on-going and we will have a live link to the Sunny Portal webpage soon!

Electricity Supply for Each Property

Batchedeigg HousemetersThe new grid electricity supply connects every property on the island.  Households are limited to 5kW and businesses 10kW.  Electricity is purchased using pre-payment cards and every property has a wireless 'Owl' energy monitor so people can see how much electricity they are using.

Nearly every light bulb on the island is low energy and the islanders are well used to energy conservation and understand much more about energy than on the mainland.

Some properties used to have their own small power system (generator and inverter etc...) and have a change-over switch so they can switch over from Eigg Electric to their own private supply if required. In the community buildings (Tea Room, Community Hall and Churches) plug-in load controllers (DILC's) are used to switch on background heaters to utilise surplus renewable energy in times when the battery store is full.

Carbon Savings

There are considerable carbon savings to be gained with the installation of the mains type system. The proposed PV array will save at least 10 tonnes of CO2 per year (based on DTI figures of 0.43kg/kWh).

Batchedeigg BeachviewEigg Sun