Isle of Eigg

About the island

View of Rum from Eigg

The Isle of Eigg, at 8km by 6km, is the second largest of The Small Isles 16km off the Western Coast of Scotland south of the Isle of Skye.

With just over 100 inhabitants, it is also the most populous. Eigg boasts a wide variety of coastal scenery, ranging from beaches and spectacular cliffs, to historic caves.

Once boasting a population of 500, the island was left with just 64 inhabitants before local residents completed their ambitious £1.5million purchase of the land in 1997, after decades of mismanagement by absentee landlords. Since then, the depopulation trend has been reversed, with Eigg now thriving and home to 105 residents, thanks in large part to the work of the Isle of Eigg Heritage Trust, (a partnership between the residents of Eigg, the Highland Council, and the Scottish Wildlife Trust) which was set up to drive through the deal. New homes have been built, tenants have been given security of tenure, and the island generates virtually 100% of its electricity using renewable energy.

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View of Rum from Eigg

Isle Of Eigg Electrification

The Sgurr - Isle of Eigg Unloading equipment on Eigg Transformer on Eigg Eigg switchgear Eigg Laig Hydro Turbine Eigg Hydro weir Eigg diesel generators Isle of Eigg Notice Boards

Prior to 2008 the Isle of Eigg was not served by mains electricity, with most properties relying on ageing diesel generators for power.

In 2008, the Isle of Eigg became almost totally independent from oil imports from the mainland and from fossil power sources by switching on a unique hybrid system. This pioneering Sunny Island system was designed & installed by Wind & Sun and enabled over 90% of the island’s power to be generated from renewables - ensuring 24 hours energy for the first time to all 46 households, 21 businesses and 6 community facilities on the island.

The Isle of Eigg Electrification project has provided an 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.

Various renewable sources distributed around the island were incorporated to allow diversity of energy supply, - solar PV , three hydro turbines (6 kW, 6 kW & 100 kW) and a 4 x 6kW wind turbines all supported by standby diesel generation and batteries to guarantee continuous availability of power. Properties on the island are connected using a 3.3 kV three-phase distribution system. Load management is used to ensure optimal use of the renewables. The battery/inverter system provides the basis for the island mini-grid together with system control. Wind & Sun worked with Econnect Ventures to design this alongside SMA and this became the world's first Sunny Island Multicluster system.

This scheme provides encouragement for operators of other isolated off-grid systems to adopt these technologies, both in the UK and overseas.
It also demonstrates 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.

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

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.

Scottish Hydro also installed the new 100kW water turbine, pipeline and weir.

Power was switched on to the island on 1st February 2008.

Residents of the Isle of Eigg now have 24 hour a day electricity powered by renewable energy and 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.

The Sgurr - Isle of Eigg Unloading equipment on Eigg Transformer on Eigg Eigg switchgear Eigg Laig Hydro Turbine Eigg Hydro weir Eigg diesel generators Isle of Eigg Notice Boards

The Battery & Inverter System

Eigg Sunny Island inverters Eigg Multicluster box Eigg batteries

The 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 is 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.

Eigg Sunny Island inverters Eigg Multicluster box Eigg batteries

The PV Array

First Eigg PV array front First Eigg PV array back

The main benefit of the PV array is 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.

The 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.

First Eigg PV array front First Eigg PV array back

Wind Turbines

Eigg wind turbines Eigg Windy Boy inverters

Four 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 give best output over winter months and have potential to work 24 hours per day.

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. Maintenance is carried out by the Eigg Electric team.

Eigg wind turbines Eigg Windy Boy inverters

Electricity Supply for Each Property

Eigg house supply

The 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 (Frequency Controlled Switches) are used to switch on background heaters to utilise surplus renewable energy in times when the battery store is full.

Eigg house supply

Expanding The System

This pioneering Sunny Island system installed in 2007 enabled over 90% of the island’s power to be generated from renewables. However, since then, Eigg has seen new properties being built, an increasing population and an increasing energy demand.

The modular nature of the Sunny Island system allows flexible upgrading of the power sources and loads.

2011 22kWp PV Extension

Eigg PV extension 2011 Installing PV on Eigg 2011 Ferry and PV on Eigg Eigg Solar PV inverters 2011

In May/June 2010 there was very little rain on Eigg, resulting in reduced hydro generation & increased diesel generator support. So a new 22 kWp PV array was proposed with this being installed in April 2011.

This had always been planned for in the original electricity scheme design but due to constraints of budget the funds available were spent on installing a larger hydro turbine. This made sense since the hydro could not be increased in size at a future date but PV’s because of their modular nature and the flexibility of the Sunny Island system could be added to very easily.

Eigg were successful in obtaining funding from the Nesta Big Green Challenge (a national competition with three finalists each receiving £300,000 to develop further their community-based carbon reduction schemes); and the Ashden Awards which are given to sustainable energy projects.

After an abortive trip in February (when strong winds meant the ferry failed to make the last 100m to the pier on Eigg!) Wind & Sun installed the new PV system in March 2011 in snow with help from the Eigg Electric team! The new PV system was sited adjacent to the existing arrays and consisted of

126 x BP Solar BP4180 180Wp PV modules, connected to 3 x SMC-7000HV inverters and mounted on three Schletter PVMax-3 ground mounting frame.

Eigg PV extension 2011 Installing PV on Eigg 2011 Ferry and PV on Eigg Eigg Solar PV inverters 2011

2013 22.5kWp PV Extension

Installing PV frames on Eigg 2013 Installing PV Eigg 2013 PV Array Eigg 2013 Setting up inverters on Eigg 2013

Following the success of the previous upgrade, the islanders decided to add more PV’s which Wind & Sun installed in July 2013 – bringing the total PV contribution on Eigg to just over 50kWp.

The new 22.5kWp PV array used 90 x REC Solar REC 250PE 250Wp PV modules connected to 3 x SMC-7000HV inverters. The PV arrays are mounted on Schletter PVMax ground mounting frames.

Successfully Powering The Island

The life for the people has changed dramatically. They now can enjoy the luxury of modern living by using almost only renewable power sources. This unique system is entirely stand-alone and almost all the energy is made locally.

The system has now been running almost seamlessly for over 5 years and has proved that large scale off-grid applications are possible and that photovoltaic power can give an extremely productive valuable contribution, even in the north of Scotland.

Although the island population and loads are constantly increasing, the integration of new power sources such as additional PV has enabled sufficient renewable power to be provided to this growing community. Further steps to upgrade the system are under consideration.

In addition to the availability of 24hr power one of the greatest benefits is the reduction in diesel used to generate electricity. Fuel consumption has been reduced from 51,000 litres to 7,800 litres per year. This is a total saving of 85 %. Depending on the household or business, costs are between 25 % and 40 % now compared to before the electrification scheme. In addition, they no longer have noise or maintenance issues.

The extra PV array reduces this fuel consumption further increasing reliability and reducing costs even more.

Installing PV frames on Eigg 2013 Installing PV Eigg 2013 PV Array Eigg 2013 Setting up inverters on Eigg 2013

2019 MultiCluster Box and Battery Inverter System Upgrade

New MC Box Eigg 2019 New SI inverters 2019

As the island developed it was realised that further battery storage and Sunny Island inverter power would be required in future so it was decided to upgrade the system's central battery inverter system.

The original system had used an SMA MultiCluster MC-Box 12 (for use with 12 x Sunny Island inverters) - so this was replaced with a new MC-Box 36. At the same time an extra new cluster of 3 x SI-8.0H-12 6kW Sunny Island inverters and an additional battery bank was fitted.

The new MC-Box 36 was then successfuly commissioned with the existing 4 x clusters of Sunny Island SI-5048 5kW inverters and the new Sunny Island Cluster.

The monitoring system was also upgraded from the existing Sunny Webbox to new Sunny Data Manager.

New MC Box Eigg 2019 New SI inverters 2019

2022 - Extra 96.8kWp Ground Mount and 21.1kWp Roof Mounted PV

To further reduce the island's carbon footprint and to take advantage of the potential offered by the new MC-Box the original power control building was extended to double the size of the battery room and provide a new space to fit further Sunny Island inverters. At the same time funding was obtained for the addition of extra PV systems.

Contractors based on Eigg first made the concrete footings required for the ground mount frames over winter in difficult conditions with consistent rain and boggy ground conditions. All the equipment needed was shipped to the island, then after a bumpy journey to the island on the Spanish John landing craft (due to ferry cancellation because of stormy weather) Wind & Sun installed the PV systems with help from our good friends Solar Kinetics and ProFit Energy.

The additional PV consisted of two components:

a) Ground Mounted alongside existing PV arrays on the hillside above the power building

Five South Facing 9.36kWp arrays each consisting of 2 x Schletter PVMax ground mounting frames with 22 x REC Solar REC-440AA 440Wp PV modules on each connected to SMA STP-20000TL 20kW inverters.

b) Roof Mounted on the Eigg Electic power control building

One East and one West Facing 10.56kWp array each consisting of 24 x REC Solar REC-440AA 440Wp PV modules connected together to a SMA STP-20000TL 20kW inverter.

2022 - 2023 Extra Clusters of Sunny Island Inverters and Increased Battery Storage

Eigg’s population has increased by 70% since 1997 to 110 strong and visitor numbers have more than doubled in the past 10 years to 11,000 per annum. The increasing number of households and businesses has meant that the 78kW Sunny Island inverter capacity would soon be limited in meeting the needs and demands of Eigg’s growing population. Planned development of the An Lamrhig pier centre with improved tearoom, shop, offices and workshops would further increase power demand.

Increasing the inverter and storage system aims to tackle these pressures to improve opportunities for Eigg’s residents, its economy and environment allowing full benefit to be obtained from the recently expanded PV system

The upgrade of the system on the neighbouring Isle of Rum to use lithium-ion batteries(see here) resulted in their old Sunny Island inverters becoming available, so these were shipped to Eigg for re-use.

These three clusters each of 3 x SI-5048 were then installed in the extended power control building along with three new Rolls battery banks.

The installation was completed in time for the June 12th 25th anniversary celebration of the community buyout of the island.

Following on from this two more clusters (one of 3 x SMA Sunny Island SI-5048 and one of 3 x SMA Sunny Island SI-8.0H inverters) and two further battery banks were added in February 2023.

This brings total Sunny Island Battery inverter power to 156 kW (10 x 3 phase clusters) and total battery storage of approx. 530 kWh to 50% DOD.

2024 Upgrading Sunny Island Inverters and Increased Battery Store

Since 2007, Eigg Electric has operated the low carbon off-grid power system using hydro power, wind generation and solar PV plus battery energy storage and back-up diesel generators to supply its population and visitors. This has gradually been expanded, to increase the robustness and capacity of the system, as the population has grown from ~65 people in 2007 to 110 people now and as electrical demand has grown. Diesel use has been reduced to an average < 17% of the time.

Eigg Electric are now moving towards the next stage of development with plans to expand to meet Zero Carbon targets by 2030 enabling residents to install electric space heating, electric cooking and charging of electric vehicles in order to transition away from fossil fuels.

As one of the first steps it was decided to expand the battery energy storage system to accommodate the additional demand and generation by upgrading the existing Sunny Island system to its maximum limit .

Funding was oibtained under the Scottish Government's Community and Renewable Energy Scheme (CARES) to support this, underpinned by an in-depth feasibility study.

The Sunny Island inverter system (using SI-5048 inverters) had been running 24 hours/day every day since 2008 and although still working it was decided to replace them with the latest models (SI-8.0H-13 inverters), together with replacing some of the oldest batteries and to add two more clusters to the system.

This brings the inverter power up to the maximum that can be accommodated by the Multicluster Box 36 with **total Sunny Island Battery inverter power of 216 kW **(12 x 3 phase 18kW clusters) and total battery storage of approx. 714 kWh to 50% DOD.

Despite cancellations to the ferry to the island Wind & Sun completed this in time for the official opening of the revamped community and visitor hub 'An Laimrig' , held at the end of April.

As part of this we joined the Eigg Electric team in showing the power scheme to groups of visitors including Scottish Government representatives, funders and the press.

New community and visitor centre symbolises ‘amazing progress’ being made by Eigg

After 1997’s community buyout, the first flagship project on Eigg was the community and visitor centre An Laimhrig - Gaelic for "safe harbour" - which is located at the island's ferry pier. Over the last 10 years this has undergone a £3m phased redevelopment to improve services for the growing community and rising visitor numbers.

The redeveloped centre includes a larger grocery shop, a much bigger café and bar with amazing views, a craft shop and a base for Eigg Adventures. The first floor houses offices, hot-desking facilities and a meeting room.

In addition, an old agricultural building – the Green Shed – has been repurposed to provide office and workshop space for local businesses and the coastguard. A new biomass heating system has also been installed using Eigg’s locally produced wood fuel, and the improvements to the island’s electricity and sewage infrastructure has future-proofed the development.

Completing the scheme is Taigh Nighe (Wash House) with public toilets, showers and laundry facilities.

The new development supports 17 businesses or organisations and 29 island jobs.

Many small island businesses and contractors were involved in the project. It was led by Rebecca Long, development manager for the heritage trust. She said: “None of us under-estimated the challenges of delivering such a significant project on a remote island like Eigg. “Everybody understood the vision of employing as many local people as possible, ensuring much of the project’s funding stayed on the island.” She added: “The lasting legacy of the project goes beyond the physical community assets created and includes new skills, confidence and capacity to take on future projects.”

The official opening ceremony was performed by the oldest and youngest residents on Eigg – Peggy Kirk (92) and nine-month-old Edith Merrick, supported by her mum Anna.

Ailsa Raeburn, chair of the Isle of Eigg Heritage Trust, said: “The opening by Peggy and Edith is a nod to the amazing progress the Eigg community has made since its buyout in 1997 and to the future. “Eigg is bucking the trend of depopulation with the population having doubled since 1997 and a growing number of young people returning to or choosing to settle here. Having a fantastic facility like An Laimhrig will ensure we can keep on serving our community and visitors alike for the next 25 years.”

Wind & Sun have been privileged to have been part of this story over almost 20 years and look forward to the next chapter.

Eigg Videos

Great news item from the BBC about the award winning integrated renewable energy grid.

See here

The Scottish Island Surviving Only On Renewable Energy.

See here

Eigg Electric - video from 2009

See here

Ashden Awards video from 2010

See: here

60 Minutes film 2017

See here

Arte TV video 2023

See: here