After emailing all of the Carbon Neutral Islands Community Development Officers named in the November Island Updates with a copy and paste of my blog post “ISLAY: Carbon Neutral Island” I got an email reply from Shona MacLeod, CNI CDO and author of the Community Climate Action Plan for Barra & Vatersay, which was nice.
Installing 3 × 3.45MW wind turbines at the top of the hills, capacity factors of up to 70% are possible (see Global Wind Atlas) but only 48% CF is needed to yield 43.5 GWh per year of electricity – equivalent to the estimated total energy use of the island.
Wind, solar, storage and back-up system designer
Row E configuration text page.Peak Demand Power: 7.67 MW
Daily Usage of Energy: 115 MWh
Wind Power Capacity: 10.3 MW
Wind Capacity Factor: 48%
Wind energy per day (average): 119 MWh (~ 43.5 GWh/year)
Storage Energy Capacity: 110 MWh
Back-up power: 3.07 MW
OR
Row D configuration text page
Peak Demand Power: 6.27 MW
Daily Usage of Energy: 94.1 MWh
Wind Power Capacity: 10.3 MW
Wind Capacity Factor: 48%
Wind energy per day (average): 119 MWh (~ 43.5 GWh/year)
Storage Energy Capacity: 105 MWh
Back-up power: 2.19 MW (using only the legacy Barra Power Station 2.5MW generator preferably with biodiesel fuel)
Grid system components specification
- 3 × 3.45MW wind turbines – Vestas V117-3.45 MW with three-phase generator and HV transformer for 11kV transmission or similar.
- Turbine options: High Wind Operation, Condition Monitoring System, Service Personnel Lift, Fire Suppression, Aviation Lights, Aviation Markings on the Blades, Nacelle Hatch for Air Inlet.
- Turbines sited on the tops of hills, building new roads where necessary to get cranes and components on site for turbine erection and connection
- 120MWh / 8MW for 15 hours – Row E (or 119MWh / 7MW for 17 hours – Row D) pumped hydro storage scheme (possibly using Loch Uisge as an upper reservoir?). Spinning reserve operation for grid inertia support and off-grid frequency stability.
- 11kV new wind farm and island legacy power transmission lines
District and domestic power & heat
- choose options to suit according to preference
- heat pumps
- solar panels
- green hydrogen electrolysis & fuel cells
- legacy boilers / fireplaces burning biomass / biofuels
- thermal energy storage
- batteries
See Local Energy Plan for Barra and Vatersay & Carbon Neutral Islands – Barra Facebook
“2.1.1 Existing Local Generation
A Community wind turbine, operated by Coimhearsnachd Bharraidh agus Bhatarsaidh (Barra & Vatersay Community) Ltd (CBaB), has been in operation since May 2014. The single turbine is located in the North West of Barra with a rated output of 900 kW.” – Local Energy Plan, 2018
“The average annual production over the period 2016–22 was 3.3GWh, meaning that the turbine operates at a full output 41% of the year, on average.” – Community Climate Action Plan, 2023
Barra’s legacy 900kW Enercon wind turbine is underpowered by a factor of 11.5 and under-energy by a factor of 13.1. It would take 13 of those legacy small wind turbines to power, heat and transport the island. That’s not far too many but a neater solution would be for the Scottish and UK Governments to invest in three modern 3.45MW turbines and the pumped hydro scheme capacity I have advised here.
This solution would allow Barra & Vatersay to end its fossil fuel use.
Installation
The turbines should be purchased and installed individually in the order shown with time given between each installation to allow the island’s energy consumers to increase electrical demand to take advantage of the new turbine.
Leave turbine 3, to be installed on Beinn Tangabhal, for last, to retain the option of installing a much larger turbine as the final one until the time when a definitive assessment of the island’s ultimate electricity demand can be made.
Carbon Neutral Islands
I’d welcome any of the other Carbon Neutral Islands Project people getting in touch with me for free advice – Community Energy Scotland and the islands of Barra & Vatersay, Cumbrae, Hoy & Walls, Islay, Raasay and Yell.
Scottish Scientist 
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