Design Criteria

We chose to constrain ourselves to the following criteria when designing our ghatta-powered battery charger.

1. All parts must be readily purchasable in Kathmandu.

We felt that, for a product to be sustainable, we could not import parts ourselves. Using only what is available in Nepal turned out to be our most constraining criteria.

2. Total cost should be about US$50.

By keeping the cost down, the product becomes accessible to individual entrepreneurs with no subsidy required. Unfortunately this is one of the few (if any) alternative energy projects with this criteria. The longstanding mindset within alternative energy communities is that heavily subsidizing (and in many cases donating) even small (<300 W) electrification projects is the only viable means of rural electrification. We feel this attitude has created dependencies whose negative consequences extend far beyond the scope of this paper. Our goal is for entrepreneurs to take full ownership of and responsibility for their charging station.

3. Battery charger should be capable of recharging car batteries.

Large lead-acid batteries, such as car batteries seemed the most likely type of battery that will be used to power lights or small appliances. A system capable of charging a car battery is also able to charge all smaller rechargeable batteries as well. (6V, D, AA)

4. Battery charger system must be unobtrusive and impermanent.

Permanently altering the ghatta could seriously slow the rate of adoption by ghatta owners. They may be hesitant to install anything that alters a proven technology that has worked for centuries. In order to assuage these concerns, the ghatta most look and operate exactly as it always has during grinding operation.

5. Battery charger removal/installation should be rapid and simple.

The ghatta owner should be readily able to switch between grinding mode and battery charging mode. Difficult installation or removal of the device could seriously impair use of the charger.

6. System needs to be easy to operate.

Educating the ghatta owner on how to use a battery charger will be a challenge in and of itself. The mechanics of operation should be as straight forward as possible.

In all aspects of the design, we stressed simplicity in achieving our criteria. We did not seek to optimize the power, but reasoned that the simplest design would be most easily manufactured, least expensive, and most readily adopted by the ghatta owners.