Just metres from the company's extensive stoneworks, Forest of Dean Stone is celebrating the switch on of its micro hydro generation turbine. Harnessing the power of the River Lyd, the turbine installation will produce around 50,000 kW hours of electricity over a 12 month period, over a third of the company's usage.
Using a Crossflow Turbine type SH 3.033/6g, from leading turbine manufacturer, Ossberger, Forest of Dean Stone will generate around 12 kW of power per second: at maximum flow rate, 200 litres of water passes over and through the guide vanes per second.
The stoneworks houses all of the companies cutting equipment and consumes in the region of 180,000 kWh per annum. This is on a fixed contract from N Power at 9.4p per unit/kW, equivalent to an annual electricity bill of £18,000.
The electricity generated by the hydro turbine is fed into the distribution network of the stoneworks and what isn't consumed on site is ultimately, exported to the national grid. Managing director, Nick Horton, estimates that the nett contribution to the company, when the Feed In Tariff has been added to the 9.4p, will be in the region of £15,000 per annum, "...in simple terms we get around 83% of our electricity free, this is not only index linked but underwritten by the Government for the next 20 years," said Nick.
Forest of Dean Stone is situated next to the historic lakes at Cannop ponds, constructed in 1753 to drive the largest water wheel in Europe, powering the local ironworks a mile downstream. The ironworks and wheel have since been dismantled but evidence remains and it is the romance of this, combined with a personal drive to harness hydro power, which drove Nick to first approach his fellow board of directors with the hydro scheme. Having fallen at the first hurdle, six years prior, when looking to introduce a turbine into the Mill Race at his home in Somerset, Nick remained undeterred and it soon became apparent that the eight metre head and structure of the Cannop ponds exit spillway was just too good an opportunity to miss.
Nick continued: "Having realised the possibility of reintroducing hydro power to the stoneworks we needed to ensure that it was feasible and realistic, long-term. Initial feasibility studies were completed by a local micro hydro generation consultant whom analysed the flow data of the River Lyd, producing a computer model which concluded that the scheme would be viable. This information was extremely useful but we needed far more to meet the very stringent demands of the planning and environmental bodies. So, after numerous telephone calls, lots of hard work and more research and deliberation we commissioned renowned turbine manufacturer, Ossberger to produce a working system."
The installation wasn't without its challenges, with the snowfall and plummeting temperatures of December 2010 causing inevitable delays. Yet, only a few weeks behind schedule, Power-on Day arrived, complete with a full 12kW of generation at the point of switch on.
"Over the next few months we will be continuing to reap and certify the rewards of the installation including measurement of our carbon footprint and applying for BREEAM certification," concluded Nick. "Later in the spring we will also be holding an official launch event for our key partners, industry bodies and customers."