TECHNOLOGY

To dam or not to dam

TERENCE DICKINSON September 20 1982
TECHNOLOGY

To dam or not to dam

TERENCE DICKINSON September 20 1982

To dam or not to dam

TECHNOLOGY

Waterwheels are almost as old as civilization. In 14 BC the Roman engineer Vitruvius described how they could provide laborsaving brute power, although he said there was not much incentive to build the devices because a team of slaves could always be pressed into service.

Now, colossal turbines—the descendants of waterwheels—swallow the flow of entire rivers as hydroelectric dams feed a substantial segment of the planet’s energy consumption.

But there are limits. Even in a country as endowed with mighty rivers and waterfalls as Canada, almost all of the

accessible hydroelectric sites outside of British Columbia have been dammed.

The problem now is how to trap the energy from those thousands of sites along such rivers as the Mackenzie and the St. Lawrence where the volume of flowing water carries impressive amounts of potential power but where a major dam is impractical because of low banks or shipping routes.

According to Dartmouth, N.S., aeronautical engineer Barry Davis, the answer is to combine the most modern principles of windmill and hydrofoil technology in a water mill. The result is “the turbodyne,” a water mill that resembles a cross between an inverted helicopter and an eggbeater. Davis’ first full-scale version, funded by the National Research Council, was lowered into the St. Lawrence late last month at Cornwall, Ont., for a year of tests.

“The project originated in 1978 when the NRC requested proposals for tapping river flow without dams,” says Davis. He reasoned that “eggbeater” powergenerating windmills, then at the experimental stage, could be applied to flowing water. From there the idea for a turbodyne, or vertical-axis water mill, was born. “We were impressed by Davis’ ideas,” says Bruce Pratte, senior research officer at the NRC’s hydraulics laboratory in Ottawa—and the official who commissioned Davis’ firm, Nova Energy Ltd., to build a full-scale test version.

One of the invention’s great virtues is its simplicity. Struts attach three 1.7-m blades to a central shaft suspended in the water from a pontoon raft which is then moored in position by massive anchors. River current forces the blades to turn the shaft at about 60 r.p.m. That, in turn, drives a generator on the raft to produce electric power. If the device continues to show promise, says Pratte, the NRC is prepared to go well beyond the $300,000 already invested by ordering test turbodynes with blades three or four times larger than those in the existing system.

Trials in tidal waters, the new frontier of Canadian hydroelectricity, are already scheduled for next year in southern British Columbia and the Bay of Fundy in the Maritimes. However, at this stage the turbodyne seems more likely to augment rather than displace the high-tech conventional turbines now designed to harness Fundy tides in conjunction with an Annapolis Basin dam. The first of at least 128 of the new 30-megawatt tide turbines will be tested in the basin next spring.

In contrast, the Cornwall test turbodyne, now hooked into the St. Lawrence Power Company’s grid, is generating up to six kilowatts of power, depending on the velocity of river water and the various gear ratios. That is enough power

tor tne total requirements of a typical home. If it proves successful after a year of experiments, similar turbodynes, located where the flow of water can be more effectively concentrated, could produce up to 50 kw. Hundreds of communities and camps in northern Canada, which are dependent on electricity generated by diesel motors fed by regular fuel airlifts, will be able to harness their local water systems instead. According to a report commissioned by the federal government, hydroelectric power could be introduced in an estimated 300 to 500 remote Canadian sites. Until Davis designs a larger series of units, generating more than 1,000 kw, however, turbodyne output will not become practical for large power company use.

Indeed, it may eventually be individuals who will benefit most from the turbodyne design. Small units retailing for about $2,000 per kilowatt are foreseeable for homeowners living next to small steady-flowing streams and rivers.

Australia, the United States and Britain are currently pioneering their own research on water mills. But Canada has the research lead. British engineers, working along the same lines, have installed a four-bladed unit similar to Davis’ on the White Nile in southern Sudan. Power from the system is used to pump irrigation water to surrounding croplands. And Pratte says his more advanced Canadian design has sparked interest from U.S. power authorities in western states that are examining alternatives to nuclear power.

Davis is not surprised at the wealth of attention. He has been at the forefront of aeronautics and hydrodynamics technology since 1959, when he came to Canada from Australia to work on the Avro Arrow jet fighter, scrapped by Prime Minister John Diefenbaker shortly afterward. He is confident his turbodyne will have a happier fate.

TERENCE DICKINSON in Cornwall.