Monday, October 11, 2010

An Energy Revolution: Micro-Hydro Power

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Pat Downey lives in the tiny little town of Hofmeyer, South Africa. This little town on the edge of the great Karoo Desert seems like an unlikely place for one of Africa's most innovative water engineers to live. There is a small general store, a gas station where you have to wake up the attendant, and surprisingly, a lot of rushing water in the Fish River, used to irrigate the dry farmland scattered around the desert hills.

Downey is a gentle, unassuming man, with the language of an inventor and a slightly stooped gate. Since the 1970s he has been pioneering technology that generates electrical power from small water-driven turbines. These turbines do not need a dam to build up water pressure, but rather they divert a small part of a river and harvest electricity from the kinetic energy generated by a small drop in height.

Water is a storehouse of kinetic energy. The hydrological cycle that lifts water out of the oceans and off the land through evaporation is run on solar energy. The sun heats the water and the air, evaporation occurs and the kinetic energy from this process is stored in the water. Then the water, full of energy, falls on distant mountains high up, and runs down rivers to the sea, all the while giving up that energy as splashing waterfalls and crashing rapids. Every gorgeous waterfall is a massive release of stored kinetic energy.

For a large-scale hydro-electric dam, those gorgeous waterfalls are flooded by a big lake, the stored water is backed up into a stunning gorge that will forever be lost to admiring eyes. Not so with micro-hydro systems like the ones Downey makes.

These smalls systems divert a small amount of water around the waterfall. Generally less than 1% of the total flow. The water falls through a pipe, spins a small turbine, and is dropped into the little pool at the base of the waterfall. For an average sized river like the Fish, a little fifteen foot (4m) drop can generate enough electrical power for fifty low-cost houses.

Small hydro systems like this can survive floods, they have a very small impact on the environment, they never silt up, and they can operate for as long as they are maintained, unlike massive dams which fill up with sediment and become useless over the years.

So why are they not more widespread?
Electricity in South Africa has been kept at an artificially low price for decades. The country sought to spur investment and growth with electricity subsidies to farmers and towns. Downey tried to sell these systems, but their initial cost was just too high. That has changed now. The national electrical grid has had to become profitable, and to do that they have had to raise prices by a whopping 140% in the last three years.

Correspondingly the demand for his systems has gone through the roof. At today's prices, the systems pay for themselves in three to four years. Today he cannot keep up with all the orders, "the emails just come flooding in, we can't keep up!" He explains in his wavering excited voice.

For a man who struggled and worked for years in obscurity, waiting for just this moment, he is clearly enjoying every moment of it.

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