Developer’s Report on Proposed Mytholm Works Hydro Power Station doesn’t compute

The MDA Report on Proposed Water Turbine Facilities at the Mytholm Works site seems to lack basic information about the potential of the proposed installation. I can see no figure for the water flow which would enter the turbine. Without this figure, it’s impossible to calculate the potential output of a hydro electricity generator.

This means that there is no evidence to support the Report’s claims about the amount of electricity the proposed installation would generate. These claims are also very unclear, with the Report giving different figures for the power output – either 120-140kW, or 375kW.

This also means that the claims about the financial viability of the proposed installation are unsubstantiated, because this depends on the amount of electricity generated.

The MDA Report also seems to gloss over the legal and financial problems associated with installing the 1.4km (1 mile) new pipeline to the power house. Section 2.3 says that the source of the water that would drive the turbine is 1 mile from the proposed power station, up Wragley Valley. (See downloadable map of existing water course course.) Section 2.4 says that there’s a collection weir across the stream at this point, together with the outfall, which has been sealed off but could easily be re-opened. Section 3.1 says the main supply duct (also known as a goyt, or leat) is in good order and needs very little attention. But the Report also says that at least 1.4km will need lining with a new pipe, to provide 80mm-100mm  of head (although they must mean 80metres-100 metres, not millimetres.) This proposed new pipeline would no doubt cross different landowners’ land.  1.4km of new pipeline, plus the cost of negotiating access and supply of water through many different landowners? A professional estimate is that this alone would add some £100k to the cost – and then there’s the risk that one landowner along the route of the leat says ‘no, you can’t put that pipe across or under my land’. That would scupper the whole project.

Claims about the amount of electricity the proposed microhydro installation would generate

There are no figures for the water flow

The MDA Proposed Water Turbine Report gives a figure for the head of water (variously  80-100mm in Section 3.1-  and 80 metres in Section 3.12), but I can’t find any figure  in the Report for the flow.

Without this figure for the flow of the Colden River from Wragley Valley, it’s not possible to calculate the amount of power the proposed turbine would generate.

This doesn’t stop the Report from claiming (section 1.3) “ Sufficient power could be provided to facilitate the entirety of the mill site, ie Supermarket and Hotel, and, in addition, the adjoining provision for the elderly in Mytholm Meadows.” Apart from not understanding what this means  (what  does “facilitate the entirety” actually mean?),  if this is a claim that the proposed micro-hydro turbine would generate all the electricity needed by the proposed supermarket and hotel and the Mytholm Meadows sheltered housing, where is the evidence to support it?

Section 1.9 in the Report states that “appointed consultants” carried out investigations and studies in order to “maximise the available facilities and produce the highest amount of electricity possible”. 1.10 states that these investigations included ascertaining the flow of water within the natural stream and “ the flow that could therefore be obtained through the existing culvert which leaves the stream at a higher level”

1.11 states that Water Management Services (Hydro) have been appointed to identify the water flow.

But the Report doesn’t contain either contact details for Water Management Services (Hydro), or their report on water flow. My internet search for a company called Water Management Services came up with nothing, so I wasn’t able to ask them for information. I have asked MDA for information, and am waiting for their reply.

Section 3.1 in the Report states that the 80mm-100mm head of water at the proposed turbine “is necessary to arrive at a power output of 100-120kW (a practically achievable figure).” ( As already noted, the millimetre unit must be incorrect, and section 3.12 says that the head of water is 80 metres over 1.4km of pipeline.)  But where is the flow figure that would substantiate the claim that the power output from this proposed installation would be 100-120kW? The clue might lie in the statement that this head of water is “necessary” to achieve this output – but it’s not sufficient: for that, you need an adequate water flow.

Why you need the figure for the water flow in order to calculate the turbine’s output

To measure the potential of a micro-hydro project you need to measure: a) the head of water – ie the height the water falls, measured from the point where the water will be taken from the river, to the turbine; b) the flow of water that would power the turbine.

Power from the Landscape website explains that the flow is

“ the volume of water which can be taken from the river and redirected through the turbine. It is usually measured in cubic metres per second but in small scale schemes, it is often measured in litres per second (where 1000 litres/second equals 1 cubic metre/second).

When taking water from a river, only a portion will be taken. This is so that the ecology and appearance of the river between the intake and outflow will not dramatically change. The amount of water left in the river is called the compensation flow. The Environment Agency will decide what this should be.”

The formula for roughly calculating maximum amount of power at a site is:

Power (Watts) = Head (metres) x Flow (litres per second) x 9.81kN/m3 (specific weight of water) x (in)efficiency.

A typical efficiency of a system is about 70% ‘water to wire’ and so the figure Head X Flow X 9.81nN/m3 should then be multiplied by this (0.7) to obtain the final power potential.)

How likely is it that this proposed hydro project could generate 100-120kW? 

Power From the Landscape website says,

“In the steep sided valleys of the South Pennine catchment area, most of the streams are high head, low flow — below 100 kW.”

The website also says,

“a system producing 1 Kw consistently over a year, would generate 7670 KWh a year. The average  house in the area consumes 4300 KWh of electricity a year.” 

The new micro-hydro generator that Bridge Mill (Innovation) is installing is around a 10kW system. Based on Power from the Landscape figures, and assuming that the proposed  Mytholm Works installation has around the same potential as the Bridge Mill generator, this means it would power around 18 households/year (7670/4300 x10).

A professional estimate is that the likely maximum output of the proposed Mytholm Works installation would be 20kW. This would power around 36 households/year – not to be sneezed at, but probably not enough to cover the costs of the installation.

How likely is it that the proposed installation could generate 375kW?

Section 3.11 states that the proposed installation at the Mytholm Works site would generate around 1500mWh/year – enough energy to power 300 houses or the proposed supermarket and hotel, the Mytholm Meadows sheltered housing and possibly the school. But it doesn’t provide the figures that would support this estimate.

Section 3.11 follows on from an outline of the performance of the same kind of installation at the Logan Gill site in Cumbria. 3.12 then states that the proposed Mytholm Works installation would generate 350kW- 400kW. It seems that this estimate may simply be extrapolated from the Logan Gill site – rather than based on figures for the actual flow at the Mytholm Works site.

The Logan Gill microhydro installation apparently generates 450kW, but it has a flow of 600litres/second – almost double the Qmean flow in Colden Water.

Since Colden Water doesn’t have a flow of at least 600litres/second (after taking account of Environment Agency restrictions on the amount of water that the proposed installation may abstract), there’s no chance the proposed Mytholm Works micro-hydro installation could generate 375kW.

Section 6.4 also says “output at 375 kW total”.

In conclusion, the Report seems unclear about what the proposed installation’s power output would be – mentioning variously:

  • “a power output of 100-120kW (a practically achievable figure)” (section 3.1)
  • “350-400kW” (section 3.12) and “375kW” (section 6.4)

Which is it? And what flows are each figure based on? And why are they different?

Financial viability

a) capital costs

1.12 states that “grants…are available for such community projects”  There are two things I don’t understand about this:

  • the Department of Energy and Climate Change website says there are no government grants for community micro-hydro installations – although I’ve found that a few EnergyShare grants are available via competitions.
  •  How would the proposed Mytholm Works microhydro scheme be a community scheme? This requires that the installation would be owned by the community and that the income generated after capital and running costs were met would be used for community benefit. There is no suggestion in the planning application as far as I can see, to set up a Mytholm Works micro-hydro scheme as a community renewable project.

What arrangements does MDA envisage to transfer ownership to a community organisation and on what basis would it sell or donate the site/existing resources that remain there to the community organisation? Has MDA ascertained whether there is any community interest in setting up a community micro-hydro project on the site?

Steve Welsh, a community hydro builder whom EnergyRoyd contacted, says,

“In our professional opinion, the estimates of productivity are too high, the estimates of cost are too low and the development costs of the scheme haven’t been considered. In addition, the report underestimates the very real practical and legal issues of opening up the stretch of leat required to feed water to the generator. In our opinion the leat will be a considerable challenge to open up and will need pipework, which in itself will mean that the existing landowners along the one mile stretch of leat would all need to give their individual permission to have the leat restored. Without due consideration of this issue, the scheme is a complete non-starter.”

It’s worth noting too that this site doesn’t seem to be included in the Power from the Landscape sites for developing micro-hydro installations in the area, which presumably means that it offers little potential for hydro electricity generation.

Finally, the estimate of cost (£725k) assumes a cost of £7,250 per kW installed at the 100kW capacity. Given the issues they’ll have with lining the leat (and the Report apparently omits any extra cost for the 1.4km new pipeline), they should add a good £100k onto that, quite apart from legal fees for arranging the access and permission to lay pipework and then have it carry water through it. This means that the cost will be far higher than the Report estimates.

For purposes of comparison, the capital cost of the Logan Gill micro-hydro scheme  that the Report refers to was £1.5million. The Logan Gill installation also involved laying a long pipeline to carry water downhill from a weir to the turbine (in this case 1km – not quite as long as the proposed 1.4km pipeline for the Mytholm Works proposed micro- hydro power station)

b) Feed in Tariffs income

Page 11 of the Report,  section 4.2 on Feed In Tariffs,  says “Up to 41.3 kilowatt/hour depending on the system adopted”.

What does this mean? Is this a typo for 41.3 pence/kWh? If so, where does that figure come from?

Ofgem’s tariff tables show that the current FIT for microhydro stations with total installed capacity greater than 15kW but not exceeding 100kW is 19.6 p/kWh. For installed capacity greater than 100kW but less than 500kW, the FIT is 15.5p/kWh

4.8 says the FIT is 11.5p/kWh. This is different from the Ofgem figures.

6.8 Says “Total income from exported energy £150K-£200K.”

Without having a reliable figure for the flow, in order to calculate a realistic figure for the installation’s power output, it’s not possible to calculate the income from the Feed In Tariff. This means there’s no reliable indication that the proposed scheme would be financially viable.

The Environment Agency says the Report contains “insufficient information” to satisfy National Planning Policy Framework requirements

The Environment Agency comments:

“Hydropower schemes can be complex and need to be designed and managed carefully to ensure that they include appropriate measures to protect the local environment and avoid unacceptable impacts.

Government policy on minimising impacts on biodiversity set out in the National Planning Policy Framework (NPPF) paragraph 118, requires local planning authorities to aim to conserve and enhance biodiversity when determining planning applications. We do not consider that this has been adequately demonstrated in the present application for the reasons set out below.


At present we consider that insufficient information has been submitted to satisfy the requirements of the NPPF.

If the hydro power element of this application is critical to the Local Planning authority’s acceptance of the overall scheme, we would strongly recommend that pre-permit application discussions are initiated with us to determine whether it is likely that a sustainable hydro-scheme can be implemented in this location. We can confirm that at this stage we have not been involved in any pre-application discussion with the applicant about this scheme and would welcome the opportunity for further discussion.

(Disclaimer: Although I’m using information from the Power from the Landscape website, about how to measure the potential output of a microhydro scheme, Power from the Landscape is not in any way involved in this discussion.)

Updated 30 November to include the developers’ map of the existing water course from Colden River to the Mytholm Works site.

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