Evans Water Engineers


+44 1566 782323 · www.evans-engineering.co.uk · email: sales@evans-engineering.co.uk

The REEF - an energy solution whose time has come

Now that the UK government is again considering tidal energy as a possible part of the energy mix due to the worries over imports of Russian oil and gas, I am including here the pictoral presentation that I worked on with Rupert Armstrong Evans of the REEF. This conceptual model was assessed by Atkins and Rolls Royce for the British Government in 2010 under the 'Severn Embryonic Technologies Scheme Concept design of a very low head dual generation tidal scheme for the Severn Estuary' (DNS159636) and the results showed that such a scheme if sited on the Aberthaw - Minhead Line across the Bristol Channel would generate 30.4TW(hrs) per year. To put this in perspective this is around 12% of all the energy currently generated in the UK each year, and slightly more than the energy expected to be generated by Hinkley Point C when it is completed - 30.2TWHrs/annum.

An added benefit of the REEF Scheme is its ability to actually hold back the tide and so to a limited extent store energy for when it is most needed by the grid, thus helping to reduce the need for gas fired generators to be switched on when sudden demand occurs. This is something that wind power for all its benefits cannot do.

Dr Brian Mathew



Renewable Energy for a Greener Future

Welcome to our web site. If you are new to waterpower, researching the subject or have a particular project in mind that you are looking to develop, I hope we will be able to provide the material and service you are looking for. This is a totally rebuilt web site with much more material including diagrams, photographs and video. I hope you will enjoy your visit and pass on your comments to us including suggestions about including other related material that you are looking for. If you have specific questions or would like to discuss a particular project in detail, I hope you will email or telephone us.

Waterpower - Renewable Energy for a Greener Future

Waterpower has been used for thousands of years, and for the last 200 years 'The Evans Family' have been building water-pumps of all shapes and sizes to move it, and for the last 35 years I have been designing and building water small water turbines to extract the power from it. The ever-increasing price of oil and growing concern about the future of our planet are now allowing us to pass on our years of experience while working on environment friendly projects in Britain and around the World.

Our main objective during the last thirty-five years, has been to promote the practical use of small scale waterpower (micro-hydro) as one of the environmentally compatible technologies that offer an alternative to nuclear power, and to promote rural development programs, which include training, and consultancy, and are becoming an increasingly important part of our work. Our experience is based the design of almost 1000 small hydro schemes and on the design and manufacture of over a hundred turbines for projects around the World.

Old watermills with their picturesque waterwheels that once ground our flour in Britain, and still do in many countries around the World, can now supply your home, business or farm with renewable green electricity or mechanical power. Attractive 'Feed-In Tariffs' may also enable you to 'power your home for free' or give you an environmentally friendly business at the bottom of your garden. You are not just building for your own needs but for your children and grand children, indeed I have equipment that was built by my great grandfather that was installed in 1864 and is still running continuously.

From 'Mill Stream' to 'Mountain Stream' we have captured energy, and from a few watts to almost 1 megawatt of output, for rice milling in India to farms in Scotland. Rather than produce a few standardised turbine that do not make full use of any site, we have developed a modular system where three quarters of a plant is made up from stock components and the remainder is tailored to the exact requirement. This gives you maximum output and efficiency but at a price that is no more than the mass-produced agricultural items that are finding their way into market place.

Water powerThe applications are very diverse, and include power for remote telemetry equipment, portable generating systems, battery charging, mine lighting and power recovery. Power recovery in pipeline systems, desalination and the chemical industry can give exceedingly short pay-back periods. We have build turbines from only 20mm in diameter running on liquid CO2 to the first tidal stream turbine at 3.5 metres in diameter. We even have turbines operating on hot caustic spring water and untreated sewage.

Special turbines have been included in the construction of models for training purposes either static for illustration purposes, or as fully working desk top units, complete with pump tank and generator. The explosion proof nature of water turbines makes them ideal for use in firefighting and dangerous environments and our ultra high-pressure water turbines are now operating from the sea-water injection systems on offshore oil and gas installations where they provide power for the automatic shutdown controls.

In the developing world, and in remote rural areas in particular, micro-hydro is playing an increasingly important role. Simple and robust turbines are needed to drive agricultural machinery, and in many cases electricity is provided as a secondary service to the community. Reducing the pressure on local forests and the backbreaking task of carrying firewood over considerable distances is made possible by the provision of electric cooking and hot water.

Water powerThe new marine renewable energy industry was led by Evans technology. In the last 20 years we have built some of the pioneering devices for harnessing the waves, tidal streams and tidal range. The first tidal stream turbine that was the forerunner of all propeller devices, was designed and built here in our workshops and tested near Fort William in Scotland. Our latest system uses water at over 100 Bar pressure to convert energy from tidal or wave devices to electricity.

The Severn Tidal Reef Project is the focus of the largest tidal scheme proposal in the World, with an annual output that could exceed 15 Twh or around 5% of the UK electricity requirement. With over 600 turbines, each in excess of 15 metres in diameter, the project is truly staggering in its scale. It is somewhat surprising that a small family business should even get involved with such a proposal. If it is of interest, you may like to follow the link or go directly to www.severntidal.com

Our designs cover by far the most diverse of any manufacturer, partly because of a continuing family objective to give the customer exactly what they want. In my great grandfather's day this apparently extended to designing a horse-driven water pump for a particular farmers animal in Argentina! The 'Oil Crisis' has brought us many new enquiries from people concerned about the future cost of energy and the ultimate security of their energy and life-style, so we started to build a range of small water turbines for domestic and remote rural locations.


Water TurbineEVANS projects are classified by power output, physical features and the application or industry sector in which they are being installed.


Very small projects are typically installed for ‘Domestic’ purposes and are sometimes referred to as ‘Pico-hydro’ projects. These ‘Domestic Scale Projects’ have a nominal power output of up to 10 kW and typically supply one house in the UK and are not generally ‘grid connected’. Larger ‘Micro-hydro’ projects involve larger civil engineering works and tend therefore to be associated with farms, estates or small industries. As such the power requirement usually exceeds the supply from the hydro, particularly during the dryer summer months. An ‘import only’ or G83 limited export (16 amps/phase) may be considered. Exporting power is seldom economic at a small scale, particularly if there are other energy uses (such as oil or gas) that can be converted to run on electricity. The premium in addition to the ‘generation tariff’ for selling to the grid seldom covers the connection costs being asked by the electricity companies. Where the intention is to generate green electricity and export all or the bulk of the output we classify this as ‘Commercial’ and encompasses outputs from as little as 25kW up to about 1.5MW that is usually termed ‘Mini-Hydro’.


To set the general nature of the project we describe the sites as ‘Hillstream’ ‘Millstream’ ‘Openstream’ or ‘Industrial’. ‘Hillstream Projects’ usually require a small diversion weir, a long pipeline (penstock), a turbine house and an electrical transmission line that may be several hundred metres long. ‘Millstream Projects’ are those that either make use of existing old mill sites or use the same general design. The water is diverted from the main river into a ‘leat’ or canal that follows the contours and looses as little fall as possible. In some cases all or part of this run can be in low-pressure pipe, but is unusual on account of the high cost. A short steep penstock then carries the water to the turbine house. ‘Openstream Projects’ are those where the majority of the working head is achieved at or near to a weir. In most cases we are considering existing civil engineering structures or natural features such as a waterfall. Because the water flows are large, the turbines are generally installed within an ‘open flume’ or channel. There are many variations in possible layout, particularly if the plant has to be installed in an inaccessible or cramped location.


The use to which the power is or can be put is usually related to the design of equipment being installed. The power may be delivered as heat or as electricity. Only very small plants produce low voltage electricity for battery charging, most generated a single or three-phase AC output that is compatible with normal household and industrial equipment. An inverter system can be incorporated to make the supply constant and interconnect with the grid, but they are expensive, you loose efficiency and the risk of a breakdown is increased significantly. ‘Domestic Applications’ include all the normal household appliances, heating, cooking and hot water. The actual power output, the nature of the loads and the financial benefits will determine whether it is worth interconnecting the plant with the grid. The ‘Feed-in Tariffs’ in the UK are not dependent on being connected to or selling the electricity to the grid. Larger industrial projects will usually be grid connected because they may only supply a small part of the total load. Applications may also include mechanical end-uses such as grinding, pumping or powering tools.


EVANS hydro plants are classified as
bespoke, modular, water-motor, fish-friendly or agricultural series.


Bespoke Plants are those with a power output over 50 kW and those of an unusual or innovative design.


Modular Plants have been developed over the last 35 years by us to cover the widest possible range of sites, application and operator skills. They can be adapted on site to cater for inaccuracies or changes in site information or operating conditions, not possible with direct drive layouts.


Water-Motor Plants are intended to replace electric motors in specific industrial or low-cost applications. The units are basic but have a number of optional extras so that they can be upgraded at a later date if required.


Fish-Friendly Plants are intended as an environmentally benign alternative to a conventional low-head turbine and fish screen. The application is confined to low falls and include a number of devices including overshot water wheels, true Archimedes screw (not hydrodynamic pumps as turbines) Noira and our ‘Fishglide Turbine’


Basic Plants for operating agricultural processing equipment, irrigation pumps and generators have been supplied by us to many countries. These units have slightly lower efficiencies but can be manufactured locally in rural workshops. The plants are often of an ‘open design’ with the ‘wet-end’ outside the ‘mill building’ as with most water wheels.

EVANS water turbines are classified by
plant series, shaft orientation, case type, rotation, type/size and build.


Outlined above, this gives the general information or the specific power output.


Described as ‘V’ vertical, ‘H’ horizontal, ‘A’ angled.


Pelton and Turgo Impulse turbines generally have square sided cases (S) whilst propeller and Armstrong turbines have circular cases (C). The very low head projects of the ‘Openstream’ series are defined as open (O).


This is described as looking at the drive end of the output shaft. This is designated (A) for anti-clockwise and (C) for clockwise. This is fairly clear for most turbines but confusion can occur with double ended shafts and where the drive exits the case opposite the water inlet with a reaction turbine or where the pipe-work is non standard.


The type of turbine is determined by the site conditions and the operating system for the plant. At the highest heads up around 200 metres we use low specific speed ‘Pelton Turbines’. The lower heads down to 20 metres still use Pelton and ‘Turgo Impulse Turbines’ but with higher specific speeds. Heads between 20 and 6 metres are covered by our own ‘Armstrong’ axial-flow impulse or ‘Cross-Flow’ turbines. Below 6 metres we use ‘Cased Propeller and Kaplan Turbines’. At the very lowest heads we use ‘Open-Flume Propeller and Fishglide Turbines’.


Our general design policy is to ‘keep it simple’ and what you have left you ‘build it to last’. Surprisingly there is often little difference in cost between a cheap plastic or mild steel component and a stainless steel one, so we only use stainless steel fastenings even on our cheapest agricultural turbines. Most of the smaller turbine runners and nozzles are ‘investment castings’, so there is no point is using anything other than stainless steel. Castings are much stronger than fabrications, so why pay more for an inferior product. We are happy to supply you with a basic turbine and help you upgrade it at a later date with control systems, if your initial budget is limited.

We also make the associated equipment including screeners, sluices, valves and controls systems. Innovative technology and our work with Developing Countries have won us several International Awards and the dissemination of this technology and its local manufacture is now an important activity.

Our aim is to build quality equipment, mainly in stainless steel that is the same price as mild steel alternatives and with efficiencies and design lives that is significantly better than our competitors. We lead the field in small turbine designs and with innovations such as 'electronic load governing' that are now used around the world. We plan to continue for the next 200 years with many more innovations and products that will still be serving your grandchildren.

Rupert Armstrong Evans

Managing Director

The information on this Web Site, covers our main areas of experience, together with background information that I hope will be of interest to you. Should you wish to publish or use this information elsewhere, an acknowledgement and link would be appreciated.