Hydroelectricity

Hydroelectricity is obtained from the ENERGY contained in falling water; it is a renewable, comparatively nonpolluting energy source and Canada's largest source of ELECTRIC-POWER GENERATION. In N America in the 1850s the energy content of moving water was exploited through the use of small-capacity waterwheels and turbines for the direct drive of machinery, for example, in gristmills and sawmills. By the 1860s many hundreds of turbines, ranging up to 1000 HP capacity, were manufactured annually in the US and by the early 1870s the production of at least one Canadian factory was averaging about 20 machines per year. Hydroelectricity was introduced in the 1880s, soon after Thomas Edison began manufacturing direct-current (DC) electric generators, which were initially belt driven by steam engines. It was not long before enterprising mill owners began to install generators of up to 10-12 kW capacity, with belt drives from existing mill turbines, to provide electric lighting in the mills and adjacent premises.

The manifest advantages of electric lighting spawned a ready and increasing market for such service. Where waterpower was close at hand, turbines were installed for the express purpose of driving electric generators for lighting service, initially provided during evening hours only. By the late 1880s generation of electricity by waterpower had become well established. Early use of hydroelectric generation was limited by the capacity of the generating station, which was governed by the waterpower resource (streamflow and net height of fall), or by the electric-lighting load near the station. Beyond a few kilometres, the resistance loss inherent in the transmission of direct-current electricity became excessive. Copper conductors large enough to ensure satisfactory service over longer distances were prohibitively expensive.

High-voltage alternating current (AC) transmission, made possible by the development of commercially viable transformers in the 1890s, permitted transmission of ELECTRIC POWER over significant distances without excessive loss, and made possible the development of more remote hydroelectric sites. For example, in 1896 hydroelectric power was transmitted approximately 32 km from NIAGARA FALLS to Buffalo, NY, at 11,000 volts (then considered a phenomenally high level). The possibility of long-distance transmission encouraged great increases in the capacity of hydroelectric-generating equipment: by the early 1900s, 5000-HP directly coupled turbine-generator sets were being produced. For comparison, hydroelectric turbine-generator units of over 600,000-HP capacity are now in service.

Beginning in the early 1900s, there was rapid growth in the development of hydroelectric-power sites and progressive increases in transmission-voltage levels. More remote sites were exploited and transmission lines were extended to supply the gradual but strong growth in demand for electric power. In 1903 electric power was transmitted to Montréal from a hydro station at Shawinigan, Qué, via a 135 km long, 50,000 volt transmission line; by 1910 ONTARIO HYDRO was transmitting hydroelectric power from Niagara Falls at 110 000 volts.

By 1900 a total of 133,000 kW of hydroelectric-generating capacity had been installed in Canada. Most of this capacity was in Québec and Ontario, where attractive hydroelectric-power sites were found reasonably near urban centres; there were some smaller developments in the Maritimes, Alberta and BC. In the next 10 years, major hydro-generating stations were established in all provinces except for PEI and Saskatchewan and, in 1910, a hydro development was constructed by a gold-mining company in the Yukon. By the early 1950s, hydro facilities were serving both northern territories. Hydroelectric generation was not developed in Saskatchewan until the early 1960s, when the S Saskatchewan R Development provided control and regulation of the province's major river system.

Growth of hydroelectric generation in Canada continued at a modest rate until the mid-1920s, followed by 10 years of more intensive development, then at a much slower rate through WWII. After 1945, there was a sharp increase in hydro-and thermal-power installations to meet the progressive growth in demand. This growth, which in some provinces exceeded 10% annually, did not slacken until the mid-1970s, when the impact of the international energy crisis of 1973 on economic activity led to a decline in the annual growth rate of electric-power consumption.

In the years 1920 to 1950, hydroelectric stations accounted for over 90% of Canada's total generating capacity. Hydro's share of this capacity declined after 1950, dipping to under 60% in 1976. The decline occurred because fossil-fuel-fired thermal-generating stations then offered a cost-competitive alternative, and because few good hydro sites remained near major population centres and the cost of transmission substantially increased the cost of more remote facilities. However, the cost of competing sources of electricity, principally NUCLEAR POWER and thermal stations burning coal, oil and natural gas, has risen substantially since 1973. In 1998, approximately 61% of electrical generation was from hydroelectric sources, 27% from conventional thermal generation and 12% from nuclear generation.

Because most hydroelectric installations have been sized to extract the maximum amount of energy available at the power site, based on historical data of average annual streamflow, many stations are able to operate at full output for 70-100% of the time; most other utility systems have annual load factors (rates of average to peak demand) of 50-60%. Consequently, in 1981 approximately 76% of the consumption and 69% of the production of electrical energy in Canada was generated by hydroelectric stations that contained only about 59% of Canada's total electrical-generating capacity.

Waterpower resources basically depend on topography and climate, and development of such energy sources is related to the magnitude and proximity of load centres and to the availability and price of competing energy sources such as coal. The development of hydroelectric power and its share of the total electrical production in Canada varies considerably from province to province. Practically all hydroelectric-power sites in Canada that are reasonably close to load centres have been developed, as have several of the more remote large-scale sites. However, a significant amount of hydroelectric potential remains untapped, chiefly in northern Québec, Manitoba and BC, and in Labrador and the YT. Although this potential is far from existing or foreseeable load centres, much of it may well be developed over the next 2 or 3 decades. The main drawbacks of conventional, large-scale hydroelectric power are the initial high capital cost, the long construction period and the environmental effects of flooding. These factors are offset by the long life and low operating costs of hydro facilities. Interest in smaller-scale or "micro-hydro" projects has revived recently.

Factors that influence the viability of technically feasible hydro sites are almost exclusively economic. Hence, development of such sites would require significant decline in construction and financing costs, greatly enhanced costs of competing energy supply from other sources, development of markets for large amounts of power within reasonable proximity of such remote sites, or prices that would support the cost of transmission to southern markets. Development of the 35,000-40,000 MW of theoretical capacity which is considered not technically feasible is restricted primarily by environmental constraints. Of the 100,000 MW of technically feasible potential, 10-15% is made up of comparatively small-scale sites of less than 50 MW capacity. Most large-scale sites would exceed 500 MW capacity; several would exceed 1000 MW, and at least 2 sites in each of Québec and BC are approximately 3000 MW capacity. The foregoing estimates are mostly preliminary assessments on the basis of map studies with minimal actual site inspection; more comprehensive studies and economic analysis will be required to confirm or reject many of these potential sites on technical or economic grounds.

These estimates of hydroelectric potential do not include the long-recognized but still undeveloped TIDAL power potential of the Bay of Fundy in NS, a major source of low-head hydro power adjacent to populated areas of NS and NB. Like river-based hydro, tidal power is a natural hydraulic source that can be converted directly to mechanical and electrical energy by means of a turbine. However, tidal power is very expensive to develop, and the cyclical nature of the energy makes it less useful than river-based hydro.

Author E.W. HUMPHRYS

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