Penny J Carruthers
Carruthers Renewables Ltd.1, Abertay University2
World Water Congress XV, International Water Resources Association (IWRA), Edinburgh, Scotland, 25 -- 29 March 2015. Evaluating the viability of developing existing weirs to generate electricity. P. J. Carruthers1, D. R. Carruthers1, W. Harvey2, A. M. Duffy2, R. Wade2, W. Harvey2. 1 Carruthers Renewables Ltd, Balcassie, Kirkton of Mailer Road, Perth, PH2 0SS; email: email@example.com; firstname.lastname@example.org 2 Abertay University, Urban Water Technology Centre, School of Science Engineering and Technology, Kydd Building, Bell St, Dundee, DD1 1HG; PH (+44) 1383 308112; FAX (+44) 1383 308117; email: email@example.com; firstname.lastname@example.org Key Words: Small hydropower; modern waterwheel; abandoned weirs and mills; Scotland, UK and Europe; balanced ecology, environmental and recreational uses. Topic Area: Water Allocation among Competing Uses and Users. Water for Energy. ABSTRACT Reinventing The Wheel: the Waterwheel Introduction: In 2008 undeveloped micro-hydro, site capacity < 100kW, in Scotland accounted for an estimated 93MW (Nick Forrest Associates Ltd, et al., 2008). Development of these sites has been slow and patchy due to their uneconomical nature. A large focus has already been given to heads of less than 3m as this has the greatest potential, e.g. the HYLOW project (HYLOW, 2007), and the Venturi enhanced turbine (VerdEng Renewable Energy, 2014). A smaller yet significant number of sites are above 3m but below the height at which conventional turbines become economical. A large proportion of the uneconomical sites are abandoned weirs, commonly in an urban setting. As the cost of electricity increases and the cost of hardware decreases, a growing number of these intermediate sites are becoming viable. Issues regarding extraction of water from the riverbed and the subsequent effects on the environment and ecology make many of these sites undevelopable if turbines or Archimedes Screws are used. Therefore any restoration, and/or development of weirs and any proposed method of harnessing their energy must address the particular issues surrounding weirs, above and beyond the merely economical (Restor Hydro, 2014). If an environmentally acceptable and economic method can be found, a significant amount of green energy could be generated. In particular such developments will generate at night, with production rising in winter when more electricity is needed to replace the electricity from photo-voltaic arrays. Typically, turbine designs dominate the marketplace and run-of-the-river micro-hydro systems incorporate a new breed of micro-hydro systems: * Archimedes Screw, which is a revived and reversed technology and is more environmentally friendly than the other solutions apart from the waterwheel. This system benefits from having a fish pass built alongside the Screw. * Crossflow Turbine: an impulse turbine where the water flows over the upper rotor blades, producing a torque on the rotor, then through the centre of the rotor and back across the low rotor blades producing more torque on the rotor. Most of the power is extracted by the upper blades (roughly 75%) and the remaining 25% by the lower blades * Kaplan Turbine: basically a propeller with adjustable blades inside a tube. It is an axial-flow turbine, which means that the flow direction does not change as it crosses the rotor. Suitable for large scale operations with higher flow rates, it was discounted on cost of installation. Method: By applying modern hydrological theory it is possible to improve efficiency. In particular identifying the most appropriate wheel type, using the best technological information on the state of the art in water wheels (Muller, 1899) (Muller & Wolter, 2004). It would not be necessary to remove the water's kinetic energy before harnessing the potential energy, as is normal with turbines. Resulting from this analysis, a prototype wheel has been designed and built. A series of tests will be carried out, by the authors, on the prototype to validate the accuracy of the benefits predicted by theory. This year the first attempt to identify and record these sites in the UK has occurred with the Restor Project, a European Small Hydropower Association (ESHA) initiative. This project identifies the location and outline characteristics of historic sites with potential for hydropower generation, distributed throughout the European Union. This general collection of information only adds to the urgency of any research into the area, before any ill-advised installations take place that extract only the small portion of the energy that is easily accessed, and/or have a larger impact on the environment than necessary. Using this information, without regard to costs, the current possible hydropower solutions will be analysed, including: Archimedes Screw; cross flow turbine; Kaplan turbine; Pelton wheel and the waterwheel. The study will identify whether it is correct that for maximum energy generation with the lowest impact on the weir and river health, waterwheels are better than or equal to every other technology in all of the identified criteria. Results: This paper outlines the, * stakeholders in our river system and their competing views and needs (SEPA, 2008) * geomorphological, hydraulic, social, amenity, historic, ecological and environmental issues regarding often historic and picturesque weirs (Rickard, et al., 2003) * effects on the surrounding physical environment of the current techniques used to harness small hydropower, and compares these with the effect of a waterwheel installation * effects on the aesthetics of the current techniques used to harness small hydropower, and compares these with the aesthetics of a waterwheel, in particular of the optimised wheel shape, including the associated civil engineering works * benefits and problems of partially, or fully, restoring the original mill ponds * general and specific ecological status of rivers (SEPA) * specific issues attached to highly modified urban waterways * general and specific flow data of rivers (CEH) * current techniques used to harness small hydropower Graphs will be drawn showing the efficiency of the new wheel over a range of flows, and of wheel speeds. Although waterwheels give the image of a massive wooden wheel set in a river where the upstream water is channelled to the slowly turning wheel vanes, the first hydroelectric ventures, e.g. at Niagara Falls, New York, used the rotational energy of wheels and a direct-current (D.C.) dynamo to produce local lighting. The waterwheel under investigation is anticipated to be: * Environmentally friendly * More efficient than previous designs * Less expensive than similar capacity turbine based systems * Stand-alone system requiring minimum maintenance * Visually acceptable to stakeholders * An apt reminder of the industrial heritage of our modified waterways If the tests on the prototype wheel are successful, a full cost/benefit analysis will becarried out for the entire anticipated life of an installation on a typical small urban river flowing about 5m3/s at annual peak. By way of example, the Net Present Value (NPV) at a 10% rate of return, reflecting both estimated income and costs, will be calculated and presented. An improved waterwheel option will be considered alongside equivalent analyses for the "best of the rest" in hydropower. Conclusion and Discussion: The economic and environmental viability of a hydropower installation using the new wheel type will be summarised. Recommendations for further research and development to advance this technology will be made. Bibliography CEH, n.d. Centre for Ecology and Hydrology. [Online] Available at: http://www.ceh.ac.uk [Accessed 2014]. HYLOW, 2007. development of hydro power converter for very low head differences. [Online] Available at: http://www.hylow.eu/ [Accessed 2014]. Muller, G. & Wolter, C., 2004. The breastshot waterwheel: design and model tests. 157(Engineering Sustainability), pp. 1-9. Muller, W., 1899. Eisernen Wasserrader. 1st ed. Leipzig: Verlag Von Veit & Comp. Nick Forrest Associates Ltd, The Scottish Institute of Sustainable Technology (SISTech), Black & Veatch Ltd, 2008. Scottish Hydropower Resource Study, Final Report, Edinburgh: Forum for Renewable Energy Development Scotland. Restor Hydro, 2014. Restor Hydro. [Online] Available at: http://www.restor-hydro.eu [Accessed 2014]. Rickard, C., Day, R. & Purseglove, J., 2003. River Weirs Â– Good Practice Guide, Bristol: Enviromental Agency. SEPA, 2008. SEPA's consultation on its regulatory method for handling applications likely to result in significant adverse impacts on the water environment, Stirling: SEPA. SEPA, n.d. RBMP Interactive Map. [Online] Available at: http://gis.sepa.org.uk/rbmp/ [Accessed 2014]. VerdEng Renewable Energy, 2014. Venturi-enhanced turbine technology. Glasgow, British Htdropower Association.