Windmill wings from bamboo

Bamboo

Because of its high growth rate and easy processing, bamboo is a promising renewable resource. Bamboo’s good mechanical properties, low costs, abundant availability in developing countries and potential use in a multitude of applications show the potential of this versatile resource.

Bamboo can be woven into mats, which are very flexible. Bamboo mats can be fixed in a mould and glued together to remain in that shape. With this technique, one may construct geometrically complex structures: in one piece, at low cost, low weight and with yet very good mechanical properties.

The art of weaving mats is simple and is performed by various rural communities. The resins that could be used to fix the mats in a shape, are phenol formaldehyde (which is currently used for making moulded trays from bamboo mats) and the more environmental friendly epoxy resin.

Windmill

Windmills produce mechnical power, which can be converted into electricity, or used directly; for instance for pumping water.

At the end of 2009, 2% of the world’s electricity was generated by windmills. Almost all windmills are centralised in wind harvesting parks. Urban wind mills are contrary to this, a decentralised source of energy.

Urban areas are generally less rich in wind than rural areas. The Kotwalia community and other bamboo craftsmen are living in the rural parts of India. Less than 50% of the rural households in India have access to electricity, so there is a huge potential to supply wind energy for rural areas.

The horizontal axis wind turbine has the highest efficiency. Simplicity is essential to make this product successful. Most windmills are very high-tech products, which is in contrast with the need to keep the product (or at least the wings) as simple as possible to be able to get the wings produced by tribal craftsmen.

The Dutch polders are since 1929 decorated with Bosman windmills. The simple and functional design is very similar to classic American windmills and windmills currently built in rural areas in developing countries. The Bosman windmills have a life expectancy of 25 years, but most last over 40 years. The design of the windmill didn’t change much between 1929 and now and has gone through the test of time. The output of the windmill is approximately 500W at a nominal windspeed of 10 m/s, which is enough to power a dektop PC and two light bulbs.

Production

A first prototype is made with the vacuum injection method. The prototype is curently being tested in the Netherlands. The production of the wings by tribal craftsmen will be slightly different from the production of the prototype, due to limited access to capital and the difficulty of maintenance of complex tools in tribal areas.

As resin, the craftsmen can switch from phenolic resin to the less toxic epoxy which is used for the prototype. The price of epoxy is comparable to the price of phenolic resins.

A low-tech production technique is hand lay-up moulding of several layers of mats on a flat mould. The plates will stay flexible for a few days and can be fixed on a rod from bamboo, which should get a preservative treatment.