NORCHARD DRIFT is the site of old mine works in the Forest of Dean at OS grid reference SO 6280 0430. The Norchard Drain is the outlet for the water from the mine into the River Lyd, and is on the site of the Dean Forest Railway's Norchard Drift station. The site has been surveyed in order to assess the feasibility of using this water supply to generate renewable electricity using micro hydropower. The flow of water has never been known to run dry and is virtually free of debris.
1. Norchard Drift Outfall
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A full site survey and feasibility study has been conducted by experienced micro hydro engineers from Renewable Heat and Power Ltd. This study estimated the potential for hydro electric power generation and provided a feasible installation design which has been tailored to the site.

The hydro electric project which has been proposed will generate around 55,000 kWh per year with a peak power output of 8.2 kW. The site is unique as it uses water collected in an abandoned drift mine. The advantages of using such a site for micro hydro generation are listed below:

  • The old mine works act as a natural reservoir providing highly dependable flows throughout the year enabling the annual energy capture to be higher those obtainable at comparable sites.
  • The flow from the mine is virtually free from debris therefore reducing operation and maintenance costs.
  • The absence of aquatic life in the outfall avoids the need for fish ladders and a reserve flow which is normally required for run-of-river projects. This simplifies the Environment Agency licensing requirements.
  • The intake and turbine will be located entirely on the outfall from the mine and will have no effect on the hydrology of the River Lyd.
  • The unique nature of the mine outfall and the unusual feature of utilizing an existing underground reservoir will ensure that this project is interesting to hydro power experts, schools, colleges and the public alike.
  • The scheme is located at the Dean Forest Railway which is a popular tourist attraction for the Forest of Dean area. The turbine installation would be visible to all visitors as they enter the site and display boards will be used to provide information on power generation from micro hydro, community renewable energy initiatives and climate change issues.
  • There is a 415V three-phase connection point within 30 metres of the proposed generator installation, were the power generated could be exported to the grid.

A new plastic penstock pipe will convey the water from an intake close to the entrance of the old mine works underneath the station platform. The pipe will be laid inside the existing concrete culvert and connect to the turbine approximately 60 metres further downstream at the drain outlet next to the River Lyd. The design flow rate of the system is 350 litres per second with a net head at the turbine of 3.9 metres. A surge pipe next to the turbine house will enable excess flow to be discharged into the river and prevent an increase in flood risk from water backing-up in the mine works.

The hydro system will be part of an overall sustainable energy strategy for the railway. A 3.96kW PV system is planned for the south facing restoration shed roof and an energy efficiency audit will be undertaken of all the railway buildings. All staff will be briefed on the renewable energy systems and energy efficiency to ensure that good practice is continued and that questions from the public can be answered.