UPGRADING WATERMILLS IN INDIA

The Business Model Report for this Watermills project is now available. Please click here to download the report (PDF, 659KB)


Introduction

This web-site presents the technical details of two low-cost micro-hydro systems implemented in the Indian Himalayas to upgrade traditional watermills under a project funded by the UK Department for International Development (DfID). The new systems are used for agro-processing and local electricity generation.

Traditional wooden watermills have been used in the Himalayas for several centuries, but are crude and inefficient and are now falling into disuse: diesel mills have reduced their market and owners have descended to the plains to seek more lucrative employment.

Two levels of upgrade have been developed:

- The New-Gharat: a basic upgrade to the traditional watermill so as to maximise the milling output and compete effectively with the diesel mills.

- The Open-Crossflow: a low-cost crossflow turbine to develop at least 5kW for operating a range of agro-processing machinery, plus generate electricity.

Both turbines have been designed as simple, robust agricultural machines. They are manufactured in India and can be maintained by local technicians. They have been developed by IT Power in collaboration with Evans Engineering of the UK and transferred to a local manufacturer, Gita Pumps in Saharanpur. Local assistance was provided by HESCO and the Chamoli Watermill Association.

The design drawings for both machines are available as a free PDF download from this site, by going to the individual pages describing the new-gharat and the open-crossflow.

The New Gharat

Traditional wooden watermills ('gharats') consist of a steep open-shute bringing water to strike the flat wooden paddles of the runner. They operate off 2-6m head, developing typically 0.3kW at 100 rpm. There are believed to be up to 200,000 mills in the Indian Himalayas, a further 25,000 in Nepal, and many more in Pakistan, China, Afghanistan, Myanmar and parts of Turkey. This indigenous technology is built and maintained by the miller himself using local materials but is limited to outputs in the range 5-10 kg of flour per hour.

The new system replaces the wooden waterwheel with a cast steel runner mounted on a steel shaft. The new runner fits under the existing mill-house and can use the same mill-stones. The shaft is mounted on a ball bearing at the bottom and a runs in a wooden bearing inserted into the bottom mill-stone.


The traditional wooden runner is less than 20% efficient. The design objective was to develop a runner which can exceed 50% efficiency, but also have a geometry suitable either for casting, or low-cost welded fabrication. Furthermore, this design of runner is suitable for converting to a horizontal axis layout at a later date. The new runner is an outward flow design - the water strikes the inside edge of the blades and escapes tangentially. The new runner is smaller and faster running than the traditional gharat, with speeds in the range 200-250rpm.

The jet of water can be provided either by the traditional wooden shute, or by a PVC pipe with a nozzle. The shute is less efficient, so needs more water to get the same output.

These modifications increase the grinding rate to between 15 and 30 kg per hour.

The improved gharat costs about Rs.15000 ($300) for all components and including some civil works. If the old wooden shute is used, the cost for only replacing the runner is around Rs. 6000 ($130).

Although the old mill-stones can be used, it is important that they are 'dressed' by cutting a pattern of grooves in both stones. This allows the stones to mill efficiently using the greater power provided by the new runner, otherwise they may get hot and damage the flour, or even break.

The design drawings of the New-Gharat are available as a PDF file by clicking the link below.

Download the New-Gharat Design Pack (New Gharat.PDF 320KB)

The Open-Crossflow

The crossflow installations take the next technical step in expanding the use of hydropower for agro-processing. They also provide sufficient power and speed to run a generator. A site which is suitable for installing a crossflow needs to have more than 5m of head and at least 100 litres/second of flow available for most of the year. This is typically double the maximum flow used by a gharat, so a larger channel is required to bring the water to the turbine.

Well-established crossflow turbine technology has been adapted to produce a low cost solution for meeting the needs of the millers. Key elements of the design have been to install the turbine outside the mill building, not to encase the runner, and run all machines off a single drive pulley.

The 'overhung' layout allows the wet components to be kept outside the mill building, with the bearings inside. Running the end-use equipment off the main shaft (so avoiding countershafts) is intended to keep the system compact, cheaper and safer to operate.

In the systems installed to date, the 24-blade runner has been cast in iron as a single-piece casting. This approach is possibly unique in the history of crossflow manufacturing. A single casting is seen as the best way of avoiding fatigue-cracking at the blade roots - the traditional weakpoint of crossflows. This method also lends itself to mass-production, and guarantees a consistent quality of runner construction. However, the runner can also be fabricated if preferred.


The design drawings of the Open-Crossflow are available as a PDF file by clicking the link below.

Download the Open-Crossflow Design Pack (Open-Crossflow.PDF 541KB)