The Potential for Achieving Zero-Carbon Electricity Generation to Meet Demand in The

Shetland Islands

John McClatchey BSc PhD MBA FRMetS

Senior Research Fellow, Environmental Research Institute (ERI)

Castle Street, Thurso, KW14 7JD

Total Area of Shetland: 1,468 square kilometres (567 square miles)

Number of islands: 100+

Number of inhabited islands: 15

Population 23,240

Edinburgh 477 km (SSW)London 957 km (SbW)

Shetland Islands Council 2013 Shetland in Statistics 2013.

Figure 1 The Shetland Islands

Table 1. Shetland Islands Electricity Generation 2001/02 2010/11 2011/12 2012/13

Total generated (MWh) 230,600 217,740 203,551 214,185

Maximum demand (MW) 45.2 46.7 44.9 44.7

Maximum demand >=40 MW fewer than 46 hours in any tear (<0.6% of the time).

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Table 2. Renewable Energy Projects in Shetland by Type and Ownership

Total Installed Capacity in kWCommercial Community Household Public Total

Wind 3,783 410 175 12 4,380Solar – 19 98 6 123Hydro – 12 3 – 15District Heating – 10,000 – – 10,000Biomass 255 800 130 – 1,185

Total 4,038 11,241 406 18 15,703

Source: Shetland Islands Council Shetland in Statistics 2013

Proposed developments:

Viking Wind Farm 370 MW

Tidal power Bluemell Sound 30-40 MW

Aegir Wave Power 10 MW (off southwest coast)

SMART GRIDS

Scottish and Southern Energy, in Partnership with Hjaltland housing association, are undertaking Northern Isles New Energy Solutions (NINES), which plans to bring a smart-electricity grid system to Shetland.

NINES is trialling a 1 MW battery to manage fluctuations in supply and demand to make the best use of generation and electricity network assets.

Storage will be important and the amount required will be addressed later.

Source: http://www.vikingenergy.co.uk/downloads/Press%20release%20-20consulation%20srt.pdf

Figure 2 The proposed Viking Wind Farm

Figure 3 Photo impression looking east over Aith Source: http://www.vikingenergy.co.uk/draft_images.asp

Figure 4 Photo impression looking SE from Busta to Waddersty and Voe Source: http://www.vikingenergy.co.uk/draft_images.asp

Hourly demand for 1981-2010 was estimated using regression based on median hourly demand each month and various meteorological data.

[adjusted r2 value = 89.0%] (For details of regression see notes.)

Table 3. Estimated demand against actual demand 2008-2012

  Mean StDev Minimum Median Maximum

Actual demand (MW) 24.7 5.99 11.1 24.2 50.6

Estimated demand (MW) 24.7 5.65 10.9 24.2 41

Differences actual - estimated (MW) 0.01 1.98 -12.4 -0.1 11.8

Figure 5. Estimated capacity factor for Viking Wind Farm over 1981-2010

The climatology of renewable generation (whether wind, wave or solar) is vital in terms of estimating required storage. Modelled wind output (using WAsP) is shown below. Note average UK capacity factor 25-30% - Viking Wind Farm 48%.

Wind farm size (MW)

370 100 80 70

Maximum continuous deficit period (hours) 105 188 218 218

Amount of maximum single deficit (MWh) 2242 5520 5684 5760

Maximum length of 75% of deficits (hrs) 8 12 12 13

Maximum amount of 75% of deficits (MWh) 125 179 193 207

It is important to consider the magnitude of the likely deficits between demand and renewable generation.

Table 4. Individual periods of deficit (demand > output)

  100% storage efficiency 50% storage efficiency

Wind farm size (MW) 370 70 370 70

Median deficit (MWh) 20 386 31 13248

Mean Deficits (MWh) 120 1083 145 24224

Deficits: 75% less than (MWh) 135 1404 173 41757

Deficits: 90% less than (MWh) 336 3146 410 64270

Maximum deficit (MWh) 3781 14499 3924 75782

While individual deficits are important, accumulated deficits can develop that are larger. This is important when considering the amount of storage that might be required. The efficiency of storage also needs to be considered.

Table 5. Size of accumulated deficits (MWh) and storage required to meet deficit

What difference can smart grids make?

Using just wind power the saving using a smart grid may be limited as there are periods of zero output.

For example there is only a small improvement assuming a 20% smart grid saving when demand > wind farm output

Table 6. Demand met from Shetland wind farm output (1981 – 2010)

A B Improvement (B – A)Farm size (MW) 370 70 370 70 370 70Demand met (%) 79.4 54.4 81.4 59.1 2.5% 8%Unmet demand (%) 20.6 45.6 18.6 40.9

A output – demand

B as A but assuming 20% demand saving by smart grid when demand > output

Conclusions

Deficits using solely wind power are too large and lengthy for a smart grid to cope.

More reliable renewables can help e.g. tidal power and with a range of renewable generation smart grids can be useful. However, tidal and wave can reduce but not eliminate deficits.

Storage is vital, for example:

1. A 1 MW battery storage is being installed as part of the smart grid scheme.

2. Compressed Air Energy Storage (CAES) in underwater bags.

3. In addition, electric cars have storage of about 33 kWh with full batteries.

Cars In Shetland, if all electric, could provide 115 MWh of storage using a maximum of 25% of fully charged batteries when using a charging system with a smart grid.

4. Hydrogen could be produced by electrolysis and stored to be used as an alternative fuel (the PURE Energy Centre already does this in Shetland http://pureenergycentre.com/)

Figure 6. Looking NNE across Scalloway to Burradale 3.68 MW wind farm