Assessing the Potential for Small Hydropower

Developments on Scottish Forestry Commission Land

Aims • Establish potential hydro resources across the NFE by estimating low flows

at remote, un-gauged sites using the Low Flow Study Reports (LFSR)

derived by the Institute of Hydrology

• Compare the viability of exploiting such schemes using a theoretical

feasibility scale called the Remote Hydro Exploitation (RHE) index –

incorporating accessibility, distance from grid and remoteness from

considerable demand

• Use short case studies to highlight specific issues with energy generation at

given locations and possible options for future utilisation

Mark Calderwood - 0806582 Case Study: Allt Daidh & Allt Dabhoch, Grula, Skye • Fast flowing waterfalls located in Glen Brittle Forest. A site visit to Allt Daidh

and consultation with ‘Hydrobot’ software enabled a more detailed analysis.

• Allt Daidh: RHE Index: 3.78: Estimated demand from Eynort & Grula = 62.5

MWh/yr, potential energy surplus ≈400MWh/yr.

Overview of Results

No. Name Location Grid Ref.Area

(km2)

Annual

Runoff (mm)

ADF

(m3/s)

Q30(30)

(m3/s)

Q30(365)

(m3/s)

Net Head

(m)

Power Rating

(kW)

Energy

(MWh/year

Total Distance

(Grid + Pop.) (km)Accessibility

RHE

Index

1 Allt DaidhGlen Brittle Forest,

Isle of Skye

NG 386

2671.50 2628 0.103 0.088 0.124 168 130.1 456 8.52 0.44 3.78

2 Allt DabhochGlen Brittle Forest,

Isle of Skye

NG 383

2342.42 2628 0.166 0.141 0.201 90 112.4 394 14.92 0.44 6.62

AKinlochan, Loch

Doilet

NM 819

6730.25 2581 0.0166 0.014 0.02 270 33.2 116 10.04 0.67 6.7

BKinlochan, Loch

Doilet

NM 819

6743.58 2581 0.237 0.229 0.326 50 101.2 355 10.04 0.67 6.7

CKinlochan, Loch

Doilet

NM 819

6752.72 2581 0.18 0.172 0.246 110 167 585 10.04 0.67 6.7

4Allt na

CaillicheLoch Ailsh

NC 325

1034.41 1994 0.213 0.208 0.243 90 165 578 34.32 0.44 15.1

5Allt

Scamodale

Glen Hurich, Loch

Shiel

NM 839

7353.55 3009 0.573 0.555 0.68 95 465.4 811 20.05 0.78 15.6

6 Coire an t-Sith Argyll Forest ParkNS 130

9003.29 2379 0.193 0.188 0.249 70 116.4 408 12.07 0.56 6.71

7 Allt Criche Ben DonichNN 207

0370.75 3019 0.06 0.059 0.073 105 54.6 191 1.64 0.44 0.73

8Allt Glas-

DhoireLoch Lochy

NN 235

9382.61 2693 0.186 0.163 0.234 130 187.2 656 8.43 0.89 7.49

9Allt Camas a

ChoirceLoch Sunart

NM 765

6137.44 2581 0.498 0.494 0.696 70 305.2 1070 5.6 0.56 3.14

10Srath a

Chraisg

River Tirry, Crask

Inn

NC 525

2447.14 1423 0.216 0.234 0.249 30 62 217 19.48 0.56 10.91

3Allt Coire

Chaillich

An Option for Remote Hydro: Hydrogen Generation • Requires a drive in the hydrogen economy, and economic challenges are

reinforced by the need to understand the logistics of the technology in terms

of distributing to locations where a considerable vehicle-fuel demand is held.

• ‘California Fuel Cell Partnership’ → ‘’vehicles typically carry around 4-6kg of

hydrogen gas at a time, and can get between 50-70 miles/kg’’ [1].

• In Glen Brittle Forest, an estimated potential surplus of 800 MWh/year of

combined energy is available to produce 20,000kg of hydrogen, (using

typical electrolyser efficiency: 40 kWh of electricity ≈ 1kg of hydrogen [2]).

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60 70 80 90 100

Allt Daidh FDC for 30-day and 365-day Durations

Pe

rce

nta

ge o

f A

vera

ge D

isch

arge

Percentage of Time Discharge Exceeded

0.103

Dis

char

ge (

m3/s

)

0.88

0.124

Q'P'(30)

Q'P'(365)

Conclusions • The LFSR allow useful short-term estimations of flow profiles, however

data becomes varied and unreliable as durations extrapolated

• The RHE Index method can be applied to many analysed schemes

across the NFE, and could provide an interlinked dataset that relates

magnitudes of energy with viability for exploitation

• A substantial drive in emerging technologies that involve energy storage

such as the hydrogen industry is required to fully utilise the great

potential of hydropower left ‘stranded’ across the NFE

1. Gardner, D. (2009). Hydrogen Production from Renewables. Available online at:

http://www.renewableenergyfocus.com/view/3157/hydrogen-production-from-renewables/

[Last Accessed: 24/8/14]

2. California Fuel Cell Partnership. (2013). What Do You Need to Know About Hydrogen and

Fuel Cell Electric Vehicles?

• Expanding the scheme: Incorporating Allt Dabhoch: RHE Index: 6.62,

• Additional potential energy generation ≈ 400 MWh.

Methodology 10 watercourses were identified, and the LFSR enabled design flows to be

calculated – taken as 30th percentile flows (commonly used within industry)

over 30-day durations; (Q30(30)). Q95(10) is initially derived as a starting

reference point, and is dependent on Base Flow Index (BFI), Average Annual

Rainfall (SAAR) and the proportion of a catchment area covered by a body of

stagnant water (FALOCH). Calculated from;

𝑸𝟗𝟓 𝟏𝟎 [%𝑨𝑫𝑭] = 𝟖. 𝟖𝟏 𝑩𝑭𝑰 + 𝟎. 𝟎𝟐𝟒𝟖 𝑺𝑨𝑨𝑹 − 𝟐. 𝟒 𝑭𝑨𝑳𝑶𝑪𝑯 − 𝟐. 𝟔𝟔

Average discharge (ADF) is dependent on estimations of both catchment area

and annual runoff, which is itself obtained using evaporation totals and SAAR;

𝑨𝑫𝑭 = 𝟑. 𝟏𝟕𝟏 𝒙𝟏𝟎−𝟑 𝒙 𝑨𝑹𝑬𝑨 𝒙 𝑨𝒏𝒏𝒖𝒂𝒍 𝑹𝒖𝒏𝒐𝒇𝒇

Q95(10) is converted to absolute units, and Flow Duration Curves are

formulated by firstly adjusting Q95 to a desired duration (Q95(D)), and

furthermore plotted for any percentile; Q’P’(D), using various type curves and

multiplying factors.

Flow profiles over 30 and 365 days were derived, the latter formulated to

highlight the limitations in extrapolating the estimation method over a longer

time period. SAAR and Annual Runoff highly influence the estimation

procedure - More water entering model = higher fluctuations in predictions,

especially at higher percentile flows (i.e. Q95). This results in a scenario

where Q95(365) values are often found to exceed ADF totals, results which

should be completely unattainable. Power and energy magnitudes for a given

site are obtained using Q30(30) flows and OS mapping resources that allow

head levels to be determined.

The theoretical RHE index allows the utilisation of a resource to be assigned a

degree of difficulty using the following equation;

𝑹𝑯𝑬 𝑰𝒏𝒅𝒆𝒙 = 𝑫𝒊𝒔𝒕. 𝒕𝒐 𝟑𝟑𝒌𝑽 𝒍𝒊𝒏𝒆 + 𝑫𝒊𝒔𝒕. 𝒕𝒐 𝒑𝒐𝒑𝒖𝒍𝒂𝒕𝒊𝒐𝒏 𝒙 𝑨𝒄𝒄𝒆𝒔𝒔𝒊𝒃𝒊𝒍𝒊𝒕𝒚

Where accessibility is given as a fractional value between 0.33 and 1, based

on a potential schemes score out of 9 from the following table:

Very good communications to site - A or B road running close nearby 1

Average roads leading to site, single track wide at best, a distance from A or B road and may require some alteration 2

No connecting roads suitable for vehicle transport to site, completely isolated scheme 3

Clear paths extending to essential access points at different heights of scheme 1

Some paths around construction site though extension work would be needed 2

Very few paths, considerable construction work required prior to development being deemed feasible 3

Landscape gently sloping, construction and any electrical wiring can be built to cover rural landscape with little issue 1

Mediocre terrain - some difficulties in construction and navigation but feasible to build scheme 2

Extremely steep topography making construction and navigation around site difficult, any electrical wiring must follow roads 3

/9

Connecting

Roads

Total

Forestry paths to

essential points

of scheme

Surrounding

terrain