Hydro Update

The Eskdale generator became accredited under the government’s Renewables Obligation scheme in July 2016, so is permitted to earn Feed-in Tariff payments for the electricity produced. In testing during a sustained period of medium water supply, all parts operated well and safety aspects were proved.

However, in quiet conditions a particular frequency within the basic sound generated by the motor could be clearly heard. To counter this, a housing, dubbed ‘the hen house’, was constructed over the generator and gearbox, the obviously suspect items. The hen house is substantially made from heavy timber, insulating board and conveyor belting. The idea was that materials of different densities would reduce the various frequencies being generated, as determined by recording software loaded onto mobile phones and iPads. We even loaded the interior of the ‘house’ with concrete bricks, and the supporting framework with a steel girder, and for some tests, enclosed the structure in carpeting, to see which materials might be most effective before settling on a final design.

Although the volume of sound was reduced considerably, the annoying frequency was still noticeable and resulted in complaints from people living nearby. The Trust is anxious to preserve and improve relations with its neighbours. We consulted the suppliers of the components, and looked at a similar installation elsewhere. Thanks to the further generosity of Marcus Worthington, now a patron of the Trust and the main sponsor of the project, a professional acoustics survey was carried out. This confirmed our own findings, and the engineers used their expertise to design a more effective solution.

We realised that noise produced mainly in the gearbox was being retransmitted from the framework supporting the generator. So it is proposed to build a solid concrete base and erect a double-leaf walled building around the generating components, with specified insulating materials in critical locations. Significant modifications to the layout of the generator and structural supports will be necessary to link them with this new structure.

A site meeting has been arranged in early March with the National Park Authority planning department, to explore issues relating to the design and appearance of such a structure. A planning application will then be prepared. Approval and construction will take several months.

The Trust has decided that the generator should not be operated until the noise problem is resolved. The delay is disappointing to the trusts and individuals who contributed to the cost of the project, the engineers who installed the components, and the volunteers who have put in so much work to see the project realised. The treasurer has also had to revise his budgetary forecast, as no income is currently being generated from the sale of electricity. However, this is a necessary postponement and we remain confident of success once the problem has been overcome.
The National Trust has announced proposals for a larger, turbine-driven hydro project, further up the Whillan Beck. So far as we know, this will have no effect on our project.

Len Watson