DOMESTIC WATER TURBINES
"PICOHYDRO"
With nominal outputs up to 5 kW, these units have been specifically designed for simple low cost projects, often in remote rural locations. Unlike other mass-produced units that fit only a limited range of sites, Evans "PICO" Turbines are of modular construction, so that they can be adapted quickly and easily to fit a far wider range of site and application. The units can be installed vertically or horizontally and have a number of different runners to cater for a wide range of site conditions. Turbines that are directly connected to the generator have to be matched closely to the site on which they are to be installed
The shaft sealing system incorporates an air-gap, a feature often omitted in low cost units with dire consequences. Water will always leak past lip-seals, so if it can pass directly into the bearing, the first you may know of it will be a catastrophic failure of the drive end bearing, and possibly generator as well. We fit brushless synchronous generators that are well insulated and able to withstand accidental over-speeds. Protection against dangerous 'over-voltages' associated with over-speed conditions is also standard. Few of these features are ever found on imported Far Eastern products.
Very small units with a nominal output up to about 1000 watts (Nanohydro units) are designed to provide lighting for individual dwellings in rural areas of Developing Countries and employ high efficiency permanent magnet or totally enclosed brushless generators producing 24 volts DC. We manufacture them in small batches to keep the cost of a typical 1000watt unit below two thousand pounds.
Agricultural units also fall into the category of "PICO" have many applications from water pumping, to rice-milling. If electricity is generated at all, it is usually as a secondary activity to the commercial enterprise and may well be carried on at night when the mill processes stop. This group of turbines is designed for low cost manufacture in developing countries using as much locally available material as possible. They also have an application for low cost installations in the developed world where a small amount of power is required at an economic price.
GALLERY
"Kapido" (VSO PE 1/6/300)
Illustrated is an economical solution where there is plenty of fall and you only require a modest amount of power. This unit is installed on a water supply scheme with over 200 metres of fall. It is also provided with a failsafe deflector system that shuts the turbine down in the event of a fault. The pelton wheel runner is mounted directly on the alternator shaft. This is a 240volt single-phase unit. This was the prototype of the popular 'Peltric' unit sold in Nepal.
"Grampian" (HSB PE 2/20/166)
There are many options for horizontal shaft high head turbines, including direct drive and turbines where the runner is mounted directly on the generator shaft. Illustrated is a model that is suitable for driving a range of different machinery including a generator. Runners of various types and specific speed as well as a number of governing options are available.
"Occid" (HSO RFI 1/1/300)
This is a pair of 'ultra high pressure' turbines directly coupled to 24volt explosion proof (ATEX) brushless alternators. They operate from seawater at 100 Bar and are used to provide power to the control systems on remote offshore gas and oil platforms. The case and CNC machined runner is made from stainless steel. Other applications include mining and marine renewable energy.
"Hay" (HXF 400/400)
Formally these units were designed around cross-flow layouts, but have now been superseded by our own cast axial-flow impulse turbine for reasons of durability and efficiency. Where a customer particularly wants a cross-flow design, these are supplied with cast stainless steel runners as standard.
"Brice" (VPRO 250)
These turbines are employed in multiple turbine installations or where the available water flow is substantially constant. Variation in flow is catered for by operating different turbines in combination, and in some cases running the turbines at variable speed. In simple installations the latter is achieved mechanically rather than electronically.
"New Gharat"
These traditional Indian watermills are of simple construction and have several very useful features. The water flow is self-regulating by virtue of the open entry flume. Our improved versions have better bearings, much higher efficiency and capacity and allow the operator to stop and start the turbine without closing the sluice. Various runner profiles have been developed to optimise the performance for particular applications that can even include power recovery from untreated wastewater.
"Evans Gharat"
Developed by myself in collaboration with local partners under the 'GEF Hilly-Hydro Programme', these are now manufactured in quantity to replace the traditional wooden watermills found throughout the Himalayas. They have about three times the output of the traditional mill, and the cost is typically covered by twelve months of enhanced revenues. Further developments promise to increase both the efficiency and output significantly, and without increasing costs.
"JOSHI" (HXFO 250/200)
Developed as part of the 'GEF Hilly-Hydro Programme' in India, these turbines are complimentary to the Gharats but more powerful. The fully cast runner illustrated, is situated outside the watermill in much the same fashion as a waterwheel, while the rugged roller bearings are fitted inside the building in the dry. The extra strength required for the 'overhung design' is more than compensated for by added reliability and convenience.
"WAVE" (HXF 400/100)
Especially designed for the power take off from a 'wave energy system' this is manufactured entirely in stainless steel because it operates on salt water. The runner, like most of our other small turbine runners is an investment casting. Our cast runners overcome the very common fault with most cross-flow turbines relating to blade failures due to fatigue.
"ZIMBA" (HSD PE 1/6/400)
This particular site has a head of over 200 metres and it was necessary to keep the RPM down to 1500. There is also an alternator attached to the turbine that provides electricity and the governing function. Where a totally mechanical system is required a number of governing methods may be used to keep the speed within safe limits.
"CUILLIN" (HSD PE 1/10/100)
Illustrated here is a simple single jet Pelton turbine that is directly connected to, but not overhung from the alternator shaft. The case has a removable top cover for easy maintenance and the whole unit has been hot-dip galvanised.
"SHORING" (HSB PE 2/30/240)
A comparison between a high head two jet Pelton turbine operating from about 30 metres and a basic cross-flow turbine operating from 6 metres. Both give a power output between three and four kW. Although we can build you this kind of turbine layout, it will be cheaper to use one of our standard vertical shaft units, unless the requirement is to drive other horizontal shaft machinery.
"CORK" (HSO PE 3/20/166)
This turbine uses three jets and the runner is overhung from the alternator. My preference for these hydraulic conditions would be to use a 'Turgo' or high specific speed Pelton (Pegasus) with two jets. The selection criteria include ease of maintenance and it isn't physically possible to get under (via the tailrace) these small units and removing the generator is a lot of work just to inspect the runner or jets.
A group of vertical shaft Pelton turbines
These range from 2 kW on the right to 25 kW on the left. Such turbines are simple and efficient but careful attention needs to be paid to the bearing layout to carry the vertical thrust and to the sealing of the bottom bearing in particular. An air gap is present between the water side and the bearing seal, so that any leakage of water does not pass into the bearing.
Illustrated above is a selection of the sub 5kW plants that we have built over the years. There are many other combinations that we can be supply to match your specific requirements, so we would be delighted to hear from you. The array of designs may appear a little daunting, but all you have to do is tell me about your site and what you want and I will do the rest.
Our aim is to supply quality turbines, mainly in stainless steel that are the same price as mild steel alternatives and with efficiencies and design lives that are 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