Pre- feasibility Study Micro-Hydro Scheme

PRE - FEASIBILITY STUDY

DEVELOPMENT OF HYDRO SCHEME ON COED GWERN STREAM

Client: CAT Holdings Plc Consultant: Nick Jeffries, Engineer

Nick Jeffries, REBE Module 3 Hydro 2 | P a g e

CONTENTS Page EXECUTIVE SUMMARY……………………………………………………… 4 1. INTRODUCTION……………………………………………………………. 6 2. REPORT STRUCTURE…………………………………………………….. 6 3. SITE DESCRIPTION………………………………………………………… 6 4. SURVEY DATA ……………………………………………………………...10

Topographical survey Hydrological survey

5. SYSTEM DESIGN……………………………………………………………. 11

Civil Works Electro-mechanical Equipment Grid Connection

6. SYSTEM OPTIONS…………………………………………………………. 13

Methodology Summary of Turbine Options Optimising the system Turbine Choice Pre-fabricated options

7. COSTS v. REVENUE…………………………………………………………19

Revenue System Costs

Errors How payback period may be reduced

8. CONCLUSIONS……………………………………………………………… 24 9. RECOMMENDATIONS……………………………………………………… 24 BIBLIOGRAPHY APPENDICES

A - Topographical and Hydrological Survey Data B - Typical Run-of the River Arrangements C - Detailed Spreadsheets D - Expected Feed in Tariffs E - Performance Envelopes for Different Turbine Types F - Efficiencies of turbines at partial flows G – Performance of Cross Flow Turbines at partial flow


List of Figures, Tables and Photos Site Location Plan Photo 1 – Typical section of stream with natural cascades and underlying bedrock Photo 2 – Single Phase and three phase grid connection near to proposed site Figure 1 – Basic Layout of Civils Structures Figure 2 – Process to determine power/energy output for different systems Figure 3a – Energy v. flow at different pipe diameters Figure 3b – Power v. flow at different pipe diameters Figure 4 – Energy Output v Flow from Hydra and Low Flow Data Table 1 – Key Characteristics of Coed Gwern Stream Table 2 – Flow Data for Coed Gwern Stream Table 3 – Small v Large Turbine – Pros and Cons Table 4 – Typical Design flows v CFs for micro-hydro-systems Table 5 – Power, annual energy output, penstock diameters and design flows Table 6 – Optimization of system for max annual energy output Table 7 – Specific Speeds including approx. runner diameter for impulse turbines Table 8 – Comparison of energy output from Francis and Cross Flow Table 9 – Annual Revenue - ROCs v Feed-In Tariff Table 10 – Annual Revenue for different penstock diameters Table 11 – Estimated Costs for different system options Table 12 – Costs v benefits for choosing bigger systems


EXECUTIVE SUMMARY The site proposed by the Client for the possible development of a hydro scheme, to generate annual cash revenue through sales of energy to the National Grid, is attractive from the very outset. This is due to the Client’s ownership of the land adjacent to the stream, the good vehicle access via a parallel gravel track and through the close proximity of a grid connection. The attractiveness of the potential scheme is further enhanced after a brief desk study and site investigation reveals:

• Good height difference (head) head difference – more than 10m • Constant flow – average 200l/s • Solid bedrock - i.e. good foundation for Civils works. • Likely low ecological concerns • Imminent introduction of feed in tariff incentives

The characteristics and topography of the site would suit a run-of-the river scheme. This would comprise several structures that divert water from the main stream (while maintaining a compensation flow), remove any debris, convey water to the turbine, and return water back to the stream. The engineering works would include: intake and weir, forebay structure with debris screen, penstock pipe and the powerhouse containing a turbine, generator and control systems. Finally a tailrace that returns the diverted flow to the stream. To export the power generated to the local grid – an inverter will convert the DC to AC current, and a buried/overhead cable connection will convey the energy to the grid. Based on the measured head, distance between intake and powerhouse, annual variations in flow and the choice of penstock pipe – it is possible to generate a matrix of power and energy outputs. As the Client wants to maximize annual revenue we can then optimum to suit this governing criterion. Optimization of system for max annual energy output

Pipe Diameter (mm)

Peak Power (kW)

Annual Energy Output (kWh)

Annual revenue

250 4.1 19058 £4,383

300 6.3 24353 £5,601

350 9.3 27876 £6,412

400 10.1 30393 £6,990 Turbine choice can be assisted by considering that the stream discharges approximately 80% of its annual volume during a 4 month ‘spatey’ period. Therefore it is easy to see that for maximum energy output - high efficiency turbines are preferable over turbines that maintain output over a large range of flow.


An estimate of costs reveals a range of capital outlays between £40, 000 – 80,000, from the smallest to the largest options. Pipe costs represent between 36 – 51% of the four options considered. Running costs have been estimated as between 1.5 – 2.5%of capital costs - giving payback periods between 12.5 and 14 years. These costs and revenues represent an idea of the scale and time duration of the investment. In the detail design stage, these will be firmed up as more accurate data on flow variations and construction costs is collected. A number of ways in which the cost/revenue situation could be improved have been suggested including – specifying cheaper materials and equipment, client labour force used to undertake some of the work, scheduling of maintenance in summer, limit output to avoid potential grid connection cost issues, use of recycled materials or materials from other CAT sites, use students and volunteers from nearby CAT to design, install and supervise works. If the Client decides to proceed with the project, then flow monitoring should begin immediately. EA, DNO and adjacent landowners should also be contacted at first opportunity, to identify any potential issues.


1. INTRODUCTION CAT Holdings Ltd (“the Client”) has recently purchased an area of land in mid-Wales which it plans to develop into a Survival Training venue in preparation for Energy Armageddon. The Client has appointed Nick Jeffries (“the Consultant”) to assess the potential of developing a hydro scheme on a stream which runs through their site. The Client’s wish is that the scheme can generate annual cash revenue that will contribute to the future running costs for the Survival Centre. The desired outcome of this pre-feasibility study is

• to state whether such a scheme is viable or advisable • to describe its main features • to estimate potential revenue and anticipated capital and running costs

The result should be that the Client has enough information on which to base a decision whether to develop a micro hydro scheme.

2. REPORT STRUCTURE The report starts by presenting the results of an initial desk study and site visit carried out by the Consultant. The purpose of this first assessment was to decide quickly whether it was worth proceeding to the more in depth pre-feasibility study i.e. if there were any technical or policy constraints which could fundamentally affect the viability of the scheme. The next section looks in detail at the physical characteristics of the site, particularly its hydrology and topography - important in determining the available flow and head for the future scheme as they are the key parameters for calculating potential energy output. Any likely abstraction limitations set by the local planning authorities will be considered here. Having defined the site - the report will go on to describe the structural components of a micro-hydro scheme and look at various options based on different turbines types and other system components. Each of these options will be analysed to produce estimated annual revenue. Costs will then be estimated by considering capital outlay for installation as well as the anticipated running costs. This information will be presented as a table of cost v revenue for each option – that will show the scale of required investment and the approximate payback period. The report will finish by recommending the next steps in the development of the scheme.


3. SITE DESCRIPTION The site is located in a forest near to the A487 above the village of Penterperthog near Machynnleth. The stream flows approximately NW – SE down the steep sides of the River Dyfi Valley collecting run-off from its mostly forested catchment. The key characteristics of the stream are set out in Table 1. The section of stream between the proposed intake and powerhouse varies in width between 1.5 – 3 m and ‘funnels’ through the forest 2 – 5 m below the level of the access tracks. The length of this section is about 200m and the fall about 10m. There are a number of natural rock cascades (see photo1) which reveal solid underlying bedrock. The SW side of the stream is generally steeper sided, however along much of it there is a natural shelf which could be used to support the future penstock. Ownership of the project site is on the SW side by the Client and NE side by the Forestry Commission. Access to the site is via forestry track which runs on both sides along the entire section proposed for the scheme. A National Grid overhead power supply cable is located along the A487 about 200-300m below the proposed powerhouse location.

Table 1 – Coed Gwern Stream Key Characteristics Stream Name Coed Gwern Stream Length 3 – 3.5km Fall ~ 1 in 10 Terrain Pine forest Catchment Area 3 km2 Rainfall (approx) 2300mm (from Wallingford - Hydra) Runoff (approx) 1500mm Annual mean flow ~200l/s Total Annual run-off ~5 million cubic metres

Source: OS maps, initial walkover survey and data from an initial Hydra1 model. Assuming design flow is 50% annual mean, the power output would be 10kW. On this basis as well as the favourable access and grid connection - the Consultant has recommended that the Client proceed to a pre-feasibility study. Environmental The stream runs through land in the SW corner of the Dyfi Forest. The flora is typically pines, other trees, ferns, lichens and mosses (see photo 1). The land is managed on both sides by the forestry commission for timber production. The stream is fast flowing and emanates from run off 3km upstream, and does not seem to have any significant aquatic fauna. All in all the section of stream appear to be of low ecological value and therefore unlikely to produce any significant issue in an Environmental Assessment, beyond the standard requirement of maintaining a base flow throughout the year.

1 Hydra is a flow modeling software from CEH Wallingford.

Site Location Plan

Forestry Commission Land

Proposed

Single Phase G id C ti

Client’s Land

Proposed

Intake

Penstock

Powerhouse

3 – Phase Grid Connection

Grid Connection

SiteAccess

SITE LOCATION PLAN


Photo 1 – Typical section of stream with natural cascades and underlying bedrock

Photo 2 – Single Phase and three phase grid connection near to proposed site


4. SURVEY DATA 4.1 Topographical survey A topographical was carried out on the 21st September by the Consultant’s survey team. The results have been included in Appendix A1. The survey was closed with an agreement of 0.2%, within the allowable 1% error. Based on these results, a static head = 10.2m will be used for the initial design.

4.2 Hydrological survey A hydrological survey was undertaken to understand the flow regime of the stream, and enable an appropriate design flow to be selected for the scheme. If the Client decides to go ahead with the project, flow monitoring will be recommended to allow more precise measurements to be collected. For the survey – three approaches were taken:

• Hydra modeling in the Consultant’s office using OS Map Data • Flow data2 for the nearby Dyfi River was scaled down to the project

catchment area. • A Low Flow survey was commissioned from CEH Wallingford.

Having compared the data available, in particular the methodology and correlation with Hydra, Low Flow data was selected as the basis of the energy output analysis (see Appendix A2).

Table 2: Flow Data for Coed Gwern Stream

% Exceedance Flow m3/s

Q5 5% 0.666 Q10 10% 0.466 Q20 20% 0.287 Q30 30% 0.202 Q40 40% 0.149 Q50 50% 0.114 Q60 60% 0.087 Q70 70% 0.065 Q80 80% 0.045 Q90 90% 0.03 Q95 95% 0.023 Q99 99% 0.014

Note: Q95 – the flow that the EA will likely require to be kept in the stream for ecological and aesthetic reasons.

2 http://www.nwl.ac.uk/ih/nrfa/webdata/064001/g.html

Basin Area: 3.199km2

Base‐Flow Index: 0.44 Annual Mean Flow: 0.198m3/s Q95: 0.023 m3/s Data source: CEH Wallingford


5. SYSTEM DESIGN Small hydro schemes can be divided into 2 categories: impoundment (i.e. with dam) or run-of the-river. For this project –there is no natural lake, the valley shape is steep, narrow and forested –so an impoundment structure would be inappropriate. Run-of-the-river systems have a number of possible arrangements (see Appendix B). Those that could be considered in this scheme are: (a) open channel, (b) combined channel/penstock or (c) penstock only. Channels are normally only suitable for countries where labour is cheap compared to pipe costs, or for a particular combination of topography, river alignment and terrain. For this project the most appropriate system would be for a penstock only – fed by an intake/diversion structure and piping water directly to the powerhouse.

5.1 Civil Works Civils works are those structures required to divert water from the main stream (while maintaining a compensation flow), remove any debris, convey water to the turbine, and return water back to the stream:

• Intake and weir – controls the amount of water taken from the stream • Forebay structure and screen – removes debris and delivers water to the

penstock • Penstock – pipe that conveys water to the turbine. Needs to be able to

withstand the pressure of the water plus an allowance for ‘surge’ pressure. • Powerhouse – contains the turbine, generator and control systems • Tailrace – returns the water to the river

Figure 1 – Basic Layout of Civils Structures Source: http://www.energyhimalaya.com/sources/images/


5.2 Electro-mechanical Equipment A turbine and generator convert the energy of the flowing water into electricity. The equipment will be located in the powerhouse. The shaft speed of the turbine should be 1500 or 3000RPM to match the frequency of the grid frequency (50 Hz). If it does not, then there will be a requirement for a gearbox or for a belt drive between the turbine and generator. Turbine types are discussed in section 6.4. Generators can be either the more expensive synchronous type or for small systems the cheaper asynchronous or induction type. The powerhouse will also contain electrical wiring, a control system, and potentially an inverter (see next section) and transformer to match the electricity output to the frequency and voltage of the grid. 5.3 Grid Connection The nearest grid location appears to be a single phase line on the main road serving the buildings at the entrance to the site. There is also a 3-phase power line on the other side of the Dyfi River (see Site Location Plan and Photo 2). There will need to be either an overhead or buried cable connecting the powerhouse to the nearest junction box of the grid. If a synchronous generator is used a grid tie inverters (or synchronous inverters) will need to be included to convert DC to AC current and synchronise output allowing it to feed into the grid. If an inductor generator is specified (more likely) then either an electronic soft start or mechanical drive will be required to get the generator up to synchronization speed and then a DC-AC inverter to allow a connection. Before the initial connection, assuming the system output is below 16A/phase3, an approval process will need to be undertaken by the DNO to check it conforms to the G83/1 Regulations.

3 Equivalent to approximately 11kW output for 400V 3-Phase generator.


6. SYSTEM OPTIONS The sizing of a micro-hydro system will be determined mainly by the Client’s intended end use for the electricity generated. For a standalone system where electricity is used only in local buildings or processes, a smaller turbine may be selected that provides a steady supply for a longer period of the year, whereas for a grid connected system where all of the electricity is exported, a different system may be specified. Table 3 sets out the advantages and disadvantages at the extremes of each site’s potential generation range. Table 3 – Comparison of Small v Large Turbine

Turbine Size (kW)

(proportional to max possible

output)

Advantages Disadvantages

Large

-More efficient -Peak output higher -In seasonal countries output may match demand curve -Greater overall electricity output

- More expensive -Lower capacity factor4 -Longer periods of non-generation

Small

-Good for standalone systems -Provides a more consistent supply of electricity -Cheaper -Higher capacity factor

-Less efficient - Requirement for ballast resistor or other way of dumping energy

For this project the Client has stated that the intention is to sell all the energy produced to the local grid to gain as much cash revenue as possible. Therefore the governing factor for turbine sizing will be:

Maximize total annual energy (kWh) output 6.1 Methodology The selection of the correct turbine size is carried out using an iterative process (see fig 2) that calculates power (kW) output and the corresponding energy outputs (kWh) for a range of design flows. The scope of the analysis is expanded by considering different pipe diameters (D) for particular flows. Varying D will change the working head, H, driving the design flow – thereby changing the power and energy output. The result is a matrix of maximum turbine power output, annual energy production and pipe diameter which enables revenue and system costs to be estimated thus allowing the cost-benefits of different systems to be compared (see Appendix C).

4 Capacity Factor = [Energy Generated/yr (kWh/yr)]/[Installed Capacity (kW) x 8760]


Figure 2 – Process to determine power/energy output for different systems

If we adopt the British Hydro Association’s guideline5: “ for a good return on investment on micro-hydro systems aim for a capacity factor (CF) of 50 – 70%” This corresponds approximately to the design flows shown in table 4: Table 4 – Typical Design flows v CFs for micro-hydro-systems

DESIGN FLOW (Qo) CF Q mean 40% 0.75 Q mean 50% 0.5 Q mean 60% 0.33 Q mean 70%

source: BHA We can now begin to calculate power and energy outputs.

5 Pg. 10 Mini Hydro Guide, BHA


6.2 Summary of Turbine Options Table 5 below is a summary of the key outputs from the analysis (for detailed spreadsheets Appendix 3). The highlighted values are the maximum annual revenue for each pipe diameter at the specified flow.

Table 5 – Power, annual energy output, penstock diameters and design flows

Design Flow (%

Qmean) 100% 75% 50% 33%

Pipe Diameter

(mm)

Max Power (kW)

Annual Output (kWh)

Max Power (kW)

Annual Output (kWh)

Max Power (kW)

Annual Output (kWh)

Max Power (kW)

Annual Output (kWh)

250 0.0 0 0.1 160 4.0 14706 3.9 17735

280 0.5 1244 4.9 13636 5.6 20459 4.4 19955

300 4.8 10912 6.8 18889 6.2 22702 4.6 20821

350 10.4 23782 9.3 25884 7.0 25688 4.9 21973

400 12.8 29338 10.4 28903 7.4 26976 5.0 22470 Notes: 1. An abstraction regime limited turbine flow to 50% above Q95. This is more rigorous, than typical limits of 25% to ADF, and 50% above ADF. 2. The pipe diameters selected were those sizes commonly available from pipe suppliers 3. Assumed partial flow efficiency – 75% - in later calculations this is further refined to match established performance curves. 6.3 Optimising the system If we plot the relationship between annual energy output (figure 3a) and peak power output (figure 3b) against flow for each of the pipe diameters, we see that maximum annual energy is actually achieved at the optimum flow conditions shown in Table 6. Table 6 – Optimization of system for max annual energy output:

Pipe Diameter

(mm)

Optimum Flow

(cumecs) % QMean Peak

Power (kW) Net Head

(m)

250 0.063 32% 3.9 8.08

300 0.09 45% 5.8 8.55

350 0.132 67% 8.7 8.65

400 0.132 67% 9.5 9.43


Figure 3a – Energy v. flow at different pipe diameters

Energy Output v Flow

0

5000

10000

15000

20000

25000

30000

35000

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45Flow (cumecs)

Annu

al E

nerg

y (k

Wh)

Figure 3b – Power v. flow at different pipe diameters

Power v Flow

0

2

4

6

8

10

12

14

16

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45Flow (cumecs)

Pow

er (k

W)

400mm 350mm 300mm 250mm

An interesting and useful result from this optimization stage is that in most cases, as annual energy output reaches its maximum value, peak power output has reduced. The corollary of this is a smaller turbine (less cost) and larger output (more revenue).

9.5kW 8.7kW 5.8kW 3.9kW


6.4 Turbine Choice The type of turbine is based on a number of factors but can be narrowed down by considering the available head in the system:

• Low head sites – Francis, Propeller, Kaplan • Low - Medium head – Crossflow, Banki • High head – Pelton, Turgo

The precise selection of turbine within the overall design is an important step to realizing the optimum potential from the scheme. To assist in this process graphical tools can be used such as the performance envelope (see Appendix E); or a conceptual quantity called ‘specific speed’, Ns , that is a function of turbine shaft speed (RPM), power output and head:

Ns = 1.2 RPM √kW H1.25

For Ns = 12 - 30 Pelton; 20 - 70 Turgo; 20 - 80 Crossflow; 80 - 400 Francis; 340 - 1000 Propellor and Kaplan.

Table 7 – Specific Speeds including approx. runner diameter for impulse turbines

Pipe Diameter (mm)

Shaft Speed (RPM)

400 600 800 1000 1500

250 70 104 139 174 261

300 79 119 158 198 297

350 97 146 194 243 364

400 92 138 184 230 344

Approx. Runner Diameter (mm) 280 186 140 112 75

The results suggest either a Francis or Crossflow turbine, however there are significant overlaps between different turbine types and therefore other factors need to be considered to refine the choice, such as:

• Cost • Availability • Flow variability • Performance of turbine at variable flow rates

Crossflow turbines are accepted as cheaper to fabricate due to their comparatively simpler structure. Although their efficiency at peak output is lower than other turbine types, they have a better performance over a range of flow conditions compared (see


Appendix G). Francis turbines have a higher efficiency in the 60 – 100% Design flow region, but their performance drops off sharply below 50% design flow. If we apply the efficiencies from the efficiency v. flow graphs (appendix F) to the design data for the optimum conditions (table 6), we can compare outputs from Francis and Cross Flow turbines: Table 8 – Comparison of Outputs from Francis and Cross Flow

Francis Crossflow % Difference

400mm kWh 30393 29877 1.7% kW 10.1 9.0

350mm kWh 27876 27404 1.7% kW 9.3 8.3

300mm kWh 24353 22794 6.4% kW 6.3 5.5

250mm kWh 19058 17976 5.7% kW 4.1 3.7

As water flow corresponds to power (kW) and volume discharged corresponds to energy output (kWh), then knowing that our stream discharges approximately 80% of its annual volume during a 4 month ‘spatey’ (high flow) period of the year – it is easy to see that for maximum energy output - high efficiency at higher flow is more important than maintaining output at lower flows. 6.5 ‘Off the shelf’ options A number of manufacturers have responded to the increase in demand for micro- turbines by producing a number of low cost, modular, off the shelf systems using standardized parts for fabrication. Examples of such systems include Toshiba ‘E-Kids’6 and The Ossberger Turbine7. The advantages claimed are:

• Flexible application • Rapid assembly • Simple installation • Lower construction costs • Reduced O and M costs

These are fairly innovative systems, which in the case of Toshiba may still not be competitive in the European market as they are only assembled in Japan. However if demand in Europe continues to increase, it may mean that these systems become viable when the project reaches detail design stage.

6 http://www.tic.toshiba.com.au/product_brochures_and_reference_lists/ekids.pdf 7 http://www.ossberger.de/cms/en/hydro/the-ossberger-turbine/


7. COSTS v. REVENUE (for detailed calculations refer to Appendix C) 7.1 Revenue The potential revenue from generating renewable energy is set to increase significantly as the new feed-in tariff (FIT) incentive scheme is due to come into effect in April 2010, replacing the existing ROC8 scheme. FITs oblige utility companies to pay a premium rate set by the government, for each kWh produced by RE systems. The rate is significantly above the market rate for conventional power generation (see Appendix D – for provisional rates). The effect on potential revenues for a range of annual kWh outputs is set out in Table 9 based on a FIT rate of 17p/kWh compared to the existing ROC system that pays 2 ROCs for every MWh of electricity. ROCs currently sell at about £45/ROC (ref: http://www.nfpa.co.uk/ auctionprices.html). At these rates the potential increase in revenue amounts to 53%. Table 9 – Annual Revenue ROCs v Feed-In Tariff

REVENUE

kWh/year ROCs Value

Feed-in Tariff

(17p/kWh) Electricity (6p/kWh) ROC FIT

10000 £900 £1,700 £600 £1,500 £2,300 20000 £1,800 £3,400 £1,200 £3,000 £4,600 40000 £3,600 £6,800 £2,400 £6,000 £9,200 80000 £7,200 £13,600 £4,800 £12,000 £18,400

100000 £9,000 £17,000 £6,000 £15,000 £23,000 If we apply FIT to Table 6, we can generate a table of annual revenue for our optimum conditions: Table 10 –Annual Revenue for different penstock diameters

Pipe Diameter (mm)

Peak Power (kW)

Annual Energy Output (kWh)

Annual revenue

250 4.1 19058 £4,383

300 6.3 24353 £5,601

350 9.3 27876 £6,412

400 10.1 30393 £6,990 Assumptions

1. 4% reduction on final output for breakdown or maintenance days 2. Turbine efficiency at peak output – 90% Francis; 80% Cross flow 3. Partial flow efficiencies – see table in Appendix G

8 Renewable Obligation Certificate


4. Gear box/belt drive efficiency – 97% 5. Generator efficiency – 95% 6. Grid tie inverter efficiency – 95% (from Fronius – see Appendix E)

7.2 System Costs v. Revenue In order to analyse the financial viability of a hydro scheme it is necessary to compare revenue to costs. Costs can be divided into:

• Capital costs • Running Costs • Annual revenue

At the pre-feasibility stage it is difficult to ascribe precise costs to all elements of the design and operation. However it is possible to start building up a first estimate - by costing some key items accurately, comparing to similar completed projects and using established industry guidelines. This will at least enable options to be compared and the scale of required investment to be understood:

Table 11 –Cost for different system options

Peak Power Output (kW) 4.1 6.8 9.3 10.1

Pipe Diameter 250mm 300mm 350mm 400mm

CAPITAL %

Capital C1 Planning Design £5,000 £5,000 £5,000 £5,000 C2 Management and Finance £1,500 £1,500 £1,500 £1,500 C3 215m pressure water pipe £15,171 £23,753 £30,506 £38,246 C4 Other Civil Works £8,000 £8,000 £10,000 £10,000 C5 Electro- Mechanical £4,152 £6,886 £9,006 £9,781 C6 Distribution of Electricity £4,000 £4,000 £4,000 £4,000 C7 Contingency 10% £3,782 £4,914 £6,001 £6,853 £41,605 £54,053 £66,013 £75,379 RUNNING R1 Insurance 0.5% £208.02 £270.27 £330.07 £376.90 R2 Annual Inspection Fixed £150.00 £150.00 £150.00 £150.00 R3 Maintenance Fixed £300.00 £300.00 £300.00 £300.00 R4 Rates 0.4% £166.42 £216.21 £264.05 £301.52 R5 Administration Fixed £55.00 £55.00 £55.00 £55.00 Cost per year £879 £991 £1,099 £1,183 REVENUE Expected annual revenue £4,164 £5,321 £6,091 £6,640.87 Less Running Costs £3,285 £4,330 £4,992 £5,457 Pay back (yrs) 12.7 12.5 13.2 13.8


Assumptions 1. C1, C2, C6 and R2, R3 and R5 – assumed to be the same for all options. 2. C3 – Class B U-PVC pipe from - http://www.epco-plastics.com/ 3. C5 includes Turbo-generatorset (http://www.swithenbanks.co.uk/); grid tie

inverter (http://www.brightgreenenergy.co.uk/fronius_inverters.asp) and an allowance for control systems.

4. C1, C4, C6, C7 have been estimated and scaled according to size o f scheme. 5. Overall running costs – guided by industry norm of 1-2% of capital cost/year for

running costs. 6. Insurance and Rates percentages – adapted from DTI, 1999

The above economic analysis, which is a fairly cautious, straight-line payback calculation, has been carried out to demonstrate the basic ‘attractiveness’ of the scheme. The Client now has a better appreciation of the scale of investment and the duration involved to recoup this investment. By way of validating our estimates – the Consultant is aware of a similar (9.5 kW) scheme9 in Northern Ireland on a site which had particular special structural cost issues that cost £78, 000 to install and commission. If time and scale is acceptable to the Client, then the next project stage should include a more sophisticated analysis that incorporates accurate costs based on actual quotations and measured drawings as well as the application of discount and bank interest rates. Table 9 shows the kind of data that may be considered in such an analysis. Table 12 – Costs v benefits for choosing bigger systems

4.1kW 6.8kW 9.3kW 10.1kW

Pipe costs as % of overall costs 36% 44% 46% 51%

Revenue as % of capital costs 10.0% 9.8% 9.2% 8.8%

Increase in capital cost from cheapest option - £12,448 £24,408 £33,774

expressed as % - 29.9% 45.2% 51.2%

Increase in revenue compared to cheapest

option - £1,157 £1,927 £2,477

expressed as % - 27.8% 46.3% 59.5%

9 Designed and constructed by NewMills Hydro, Carrickfergus, N.I. Cost and size of scheme provided by Managing Director of New Mills Terry MacGuire during phone conversation on Fri 27th Nov.


7.3 Errors Flow Annual energy output is sensitive to small changes in the variables used to calculate it and also in the way the data is presented. This is illustrated when comparing the effect of using flow data from Low Flow model compared to Hydra model when calculating energy. Both sets of data are presented as a series of stepped increments (see Appendix A2), the difference being that more steps have been included in the Hydra data set. For each data set a different optimum flow and overall energy output is returned:

Hydra Low Flow Difference Optimum Flow 0.140 0.132 6.1% Annual Energy Output(kWh) 31522 30622 2.9%

Fig 4 presents this graphically: Figure 4 – Energy Output v Flow from Hydra and Low Flow Data

This result is more surprising if one considers the overall volume discharged from the Hydra model is 0.11% less than the Low Flow model i.e. less potential energy is

Comparison of Energy Output v Flow for Hydra and Low Flow

0

5000

10000

15000

20000

25000

30000

35000

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Flow (cumecs)

Ann

ual E

nerg

y (k

Wh)

400mm 250mm 400mm Hydra 250mm Hydra

250mm

400mm


generated. The issue highlights the need for accurate flow monitoring during the project development period. Pipe Length The pipe length was estimated using a distance measuring wheel along the proposed penstock route which is steep, forested and difficult to access. Pipe costs are significant in the overall costing of the project (250mm - £70/m; 400mm - £180/m), so establishing accurately the length of pipe will be an important part of the next design stage. 7.3 How payback period may be reduced The cost/revenue figures presented in section 7.2 are quite cautious; there are several ways in which the situation could be improved:

• Pipe costs based on information available at this time. Cheaper pipes may be available.

• As land is private with no vehicle loading, penstock pipe could be laid partly above ground thereby reducing excavation/backfilling costs.

• If plant and labour is available Client can potentially undertake following works (with supervision): intake works, installation of penstock pipe, construction of powerhouse and tailrace

• Calculations include 4% downtime for maintenance i.e. 15 days. If maintenance is carried out in low flow period this will have only small effect on energy output.

• Limit output to ~3.7kW (Single phase) and ~11 kW (3 phase) i.e. less than 16A/phase, thereby avoid potential grid connection cost issues.

• Specification of inductor generator over synchronous generator – will be cheaper and will not require expensive grid tie inverter

• Use of recycled materials or materials from other CAT sites • Use students and volunteers from nearby CAT to design, install and

supervise works.


8. CONCLUSIONS

The site has several characteristics that point favourably to the development of a micro-hydro scheme:

• Site owned by Client • Easy access for construction • Proximity to grid connection • Likely low ecological concerns • Reasonable head difference with constant flow. • Solid bedrock allows for good foundation for Civils works.

The situation is further enhanced by the expected introduction of the feed-in tariffs in April 2010 which will create an even more economically sound case for developing the project. The estimate of potential revenue from electricity sales against estimated costs for four different systems suggests a payback period of 12.5 – 14 years for an investment between £40,000 - 80, 0000. This does not include an allowance for discount rates.

9. RECOMMENDATIONS

In order to develop the scheme further the following actions are recommended:

• Start collecting accurate flow data. If a measuring weir is used, this can be incorporated into final design of intake works

• Determine size of investment available • Think clearly how you would like energy to be used in the future – if

eventually energy is to be used on site this will effect the final design • Contact Environmental Agency to establish any potential ecological

constraints • Contact DNO to advise of plans • Contact Forestry Commission


Bibliography

1. British Hydro Association (BHA), A Guide to UK Mini-Hydro Developments Version 1.2, Jan 2005.

2. T.Kirk (1999), Small Scale hydro-power in UK. CIWEM, Water and Environmental Journal. Vol 13. Issue 3. Pages 207 – 212.

3. DTI, 1999 - New and Renewable Energy: Prospects in the UK for the 21st Century: Supporting Analysis, - http://www.berr.gov.uk/files/file21102.pdf

4. Boyle, G (2004) – Renewable Energy – Power for a Sustainable Future. Second Edition. Oxford Press.


Appendix A – Topographical and Hydrological Survey Data A1 -Levels

UP SURVEY DOWN SURVEY Forward Back Height Forward Back Height 3.98 0.1825 3.7975 2.91 0.31 2.6

3.8375 0.1375 3.7 3.51 0.325 3.185 3.702 0.375 3.327 1.2325 3.842 ‐2.6095 3.925 0.55 3.375 0.0325 3.98 ‐3.9475 3.315 1.415 1.9 0.0325 3.918 ‐3.8855 0.125 3.715 ‐3.59 0.17 2.8275 ‐2.6575

0.735 2.91 ‐2.175 1.26 2.77 ‐1.51

1.328 2.814 ‐1.486 TOTAL 10.3345 10.311

A2 - Low Flow and Hydra Stream Data

Low Flow Hydra

% Exceedance

Flow m3/s Volume m3 %

Exceedance Flow m3/s Volume m3

‐ ‐ 2.0% 0.8 504576 ‐ ‐ 3.0% 0.7 220752 5% 0.666 1050149 5.0% 0.58 365818 10% 0.466 734789 10.1% 0.41 659418 ‐ ‐ 15.0% 0.33 509937

20% 0.287 905083 20.0% 0.26 409968 30% 0.202 637027 29.1% 0.2 573955 40% 0.149 469886 39.7% 0.15 501422 50% 0.114 359510 50.0% 0.11 357303 60% 0.087 274363 60.3% 0.09 292339 70% 0.065 204984 70.9% 0.07 233997 80% 0.045 141912 80.0% 0.05 143489 90% 0.03 94608 89.9% 0.03 93662 95% 0.023 36266 95.0% 0.02 32167 ‐ ‐ 97.0% 0.02 12614 ‐ ‐ 98.0% 0.02 6307

99% 0.014 17660 99.0% 0.01 3154

Total 4926239 Total 4920877

Difference ‐0.11%


Appendix B – Typical Run-of the River Arrangements


Appendix C – Detailed Spreadsheets

Energy Output Estimation, 350mm, 75% Qmean

Catchment area 3.199 sq.km Design Turbine Flow 0.149 cumecsAnnual mean Flow 0.198 cumecs Min turbine flow (% of max flow) 10%Pipe diameter 350 mm Min. turbine flow 0.015 cumecsPipe length (m) 215 mStatic Head (m) 10.3 mHead Loss(Pipes/Fittings) 1.85 mNet head (m) 8.26 m

% Exceedance Flow m3/sFlow ‐ Q95 (m3/sec)

50% above Q95

Turbine Flow (cumecs)

Compensation Flow (cumecs)

Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.149 0.518 9.3 408210% 0.466 0.443 0.222 0.149 0.318 9.3 408220% 0.287 0.264 0.132 0.132 0.155 7.4 647930% 0.202 0.179 0.090 0.090 0.113 5.0 439340% 0.149 0.126 0.063 0.063 0.086 3.5 309250% 0.114 0.091 0.046 0.046 0.069 2.5 223360% 0.087 0.064 0.032 0.032 0.055 1.8 157170% 0.065 0.042 0.021 0.021 0.044 1.2 103180% 0.045 0.022 0.011 0.000 0.045 0.0 090% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0

TOTAL 26962 kWh/yrBreakdown/maintenance (‐4%) 25884 kWh/yr

Q95 (m3/sec) 0.023 Price/kWh £0.06Qmean (m3/sec) 0.198 Feed in tariff £0.17

Average Gross £5,953Efficiency max partial flowTurbine 84% 75%Gear Box 97%Generator 95%

0.75 x Qmean



% Exceedance Flow m3/sFlow ‐ Q95 (m3/sec) 50% above Q95



Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.099 0.567 6.2 271010% 0.466 0.443 0.222 0.099 0.367 6.2 271020% 0.287 0.264 0.132 0.099 0.188 6.2 542030% 0.202 0.179 0.090 0.090 0.113 5.0 437540% 0.149 0.126 0.063 0.063 0.086 3.5 308050% 0.114 0.091 0.046 0.046 0.069 2.5 222460% 0.087 0.064 0.032 0.032 0.055 1.8 156470% 0.065 0.042 0.021 0.021 0.044 1.2 102780% 0.045 0.022 0.011 0.011 0.034 0.6 53890% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0




0.5 x Qmean


Catchment area 3.199 sq.km Design Turbine Flow 0.065 cumecsAnnual mean Flow 0.198 mm Min turbine flow (% of max flow) 10%Pipe diameter 250 mm Min. turbine flow 0.007 cumecsPipe length (m) 215 mStatic Head (m) 10.3 mHead Loss(Pipes/Fittings) 2.13 mNet head (m) 7.96 m




Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.065 0.601 3.9 172010% 0.466 0.443 0.222 0.065 0.401 3.9 172020% 0.287 0.264 0.132 0.065 0.222 3.9 344030% 0.202 0.179 0.090 0.065 0.137 3.9 344040% 0.149 0.126 0.063 0.063 0.086 3.4 297750% 0.114 0.091 0.046 0.046 0.069 2.5 215060% 0.087 0.064 0.032 0.032 0.055 1.7 151270% 0.065 0.042 0.021 0.021 0.044 1.1 99280% 0.045 0.022 0.011 0.011 0.034 0.6 52090% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0



Average Gross £4,078Efficiency max partial flowTurbine 84% 75%Generator 95%Grid tie inverter 97%

0.5 x Qmean

Energy Output Estimation, 400mm, Qmean



50% above Q95



Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.198 0.468 12.8 560310% 0.466 0.443 0.222 0.198 0.268 12.8 560320% 0.287 0.264 0.132 0.132 0.155 7.6 667030% 0.202 0.179 0.090 0.090 0.113 5.2 452340% 0.149 0.126 0.063 0.063 0.086 3.6 318450% 0.114 0.091 0.046 0.046 0.069 2.6 229960% 0.087 0.064 0.032 0.032 0.055 1.8 161770% 0.065 0.042 0.021 0.021 0.044 1.2 106180% 0.045 0.022 0.011 0.000 0.045 0.0 090% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0

TOTAL 30560 kWh/yrQ95 (m3/sec) 0.023 Breakdown/maintenance (‐4%) 29338 kWh/yrQmean (m3/sec) 0.198 Price/kWh £0.06

Feed in tariff £0.17Efficiency max partial flow Average Gross £6,748Turbine 84% 75%Gear Box 97%Generator 95%

Q mean

Energy Output Estimation, 350mm Optimum



50% above Q95



Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.132 0.534 8.7 379810% 0.466 0.443 0.222 0.132 0.334 8.7 379820% 0.287 0.264 0.132 0.132 0.155 8.7 759530% 0.202 0.179 0.090 0.090 0.113 5.2 459840% 0.149 0.126 0.063 0.063 0.086 3.7 323750% 0.114 0.091 0.046 0.046 0.069 2.7 233860% 0.087 0.064 0.032 0.032 0.055 1.9 164470% 0.065 0.042 0.021 0.021 0.044 1.2 107980% 0.045 0.022 0.011 0.000 0.045 0.0 090% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0




Q mean




50% above Q95



Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.090 0.576 5.8 256110% 0.466 0.443 0.222 0.090 0.376 5.8 256120% 0.287 0.264 0.132 0.090 0.197 5.8 512130% 0.202 0.179 0.090 0.090 0.113 5.2 454740% 0.149 0.126 0.063 0.063 0.086 3.7 320150% 0.114 0.091 0.046 0.046 0.069 2.6 231260% 0.087 0.064 0.032 0.032 0.055 1.9 162670% 0.065 0.042 0.021 0.021 0.044 1.2 106780% 0.045 0.022 0.011 0.011 0.034 0.6 55990% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0




Q mean


Catchment area 3.199 sq.km Design Turbine Flow 0.063 cumecsAnnual mean Flow 0.198 mm Min turbine flow (% of max flow) 10%Pipe diameter 250 mm Min. turbine flow 0.006 cumecsPipe length (m) 215 mStatic Head (m) 10.3 mHead Loss(Pipes/Fittings) 2.02 mNet head (m) 8.08 m




Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.063 0.603 3.9 169410% 0.466 0.443 0.222 0.063 0.403 3.9 169420% 0.287 0.264 0.132 0.063 0.224 3.9 338730% 0.202 0.179 0.090 0.063 0.139 3.9 338740% 0.149 0.126 0.063 0.063 0.086 3.9 338750% 0.114 0.091 0.046 0.046 0.069 2.5 218460% 0.087 0.064 0.032 0.032 0.055 1.8 153670% 0.065 0.042 0.021 0.021 0.044 1.2 100880% 0.045 0.022 0.011 0.011 0.034 0.6 52890% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0



Average Gross £4,153Efficiency max partial flowTurbine 84% 75%Generator 95%Grid tie inverter 97%

0.5 x Qmean




50% above Q95



Power Output (kW)

Power output (kWh)

5% 0.666 0.643 0.322 0.132 0.534 9.5 414110% 0.466 0.443 0.222 0.132 0.334 9.5 414120% 0.287 0.264 0.132 0.132 0.155 9.5 828130% 0.202 0.179 0.090 0.090 0.113 5.7 501340% 0.149 0.126 0.063 0.063 0.086 4.0 352950% 0.114 0.091 0.046 0.046 0.069 2.9 254960% 0.087 0.064 0.032 0.032 0.055 2.0 179270% 0.065 0.042 0.021 0.021 0.044 1.3 117680% 0.045 0.022 0.011 0.000 0.045 0.0 090% 0.03 0.007 0.004 0.000 0.030 0.0 095% 0.023 0.000 0.000 0.000 0.023 0.0 099% 0.014 0.000 0.000 0.000 0.014 0.0 0




Q mean


Appendix E – Performance Envelopes for Different Turbine Types

Figure 3 – Performance envelope for different turbines

Source: DBERR Report 2004 and BHA 2008


Appendix F – Efficiencies of turbines at partial flows Source: Kirk, 1999 Table of partial flow efficiencies - derived from above graph

Qmax/Qo Francis Crossflow 100% 90% 80% 90% 90% 82% 80% 90% 83% 70% 89% 85% 60% 86% 85% 50% 84% 854% 40% 80% 84% 30% 73% 80% 20% 62% 70% 18% 0% 65% 10% 0% 30%


Appendix G – Performance of Cross Flow Turbines at partial flow Source: http://www.ossberger.de/cms/en/hydro/the-ossberger-turbine/

Documents

Pre- feasibility Study Micro-Hydro Scheme