No major new technologies are needed for the current construction of tidal power plants, however, it may pay off to foster development and research the interface of a central’s output with national grids, calculate a sound estimate of its economic interest, design and site proper implanting, and of course environmental effect and sustainability (Frau 1993).
The regularity from year to year of tidal power (less than 5% variation) is one of its main advantages. Co-lateral advantages are proper to a site: the dam can accommodate rail or road traffic, provide navigation improvements, cheap electricity a virtually inexhaustible supply of energy; it can constitute a send off for un – or poorly-exploited regions and is pollution free—though not entirely environmentally benign.
Though capital costs are high—but already reduced by one third by dispensing with cofferdams—the plant’s useful life is two to three times longer than that of thermal or nuclear plants. Low-head water power could be converted to compressed air power, and smaller and cheaper high speed air turbo-generators would then produce electrical power.
As an example, for Bay of Fundy projects the benefits of a tidal plant due to fuel cost savings would exceed by far capital and operating costs; the best ratio of benefit to cost was estimated, ten years ago at 2.6 or 3. Compared to alternate energy sources, the benefits to the market areas for tidal power were found similar to nuclear, and superior to coal. These market areas cover the Maritimes, New England and New York; Quebec, a natural customer for such power, will not become a patron because it has too much hydropower available. The Canadian Board that conducted the study on the basis of un-re-timed output of single effect plants concluded that tidal power is economically viable. The simulation was carried out for a period spanning 1995-2015 with generation, loads and prices assumed to remain stable beyond 2015. The role of tidal energy would be to reduce the amounts needed of the most expensive fuel consumed in the market area.
Looked over in this estimation is the site of the plant, the huge compensation paid to farmers for their land and strikes that plagued construction.
The tidal power plant has no related fuel cost and thus once capital cost is recovered, cheaper electricity becomes available. A break-even level is reached at the time a same age nuclear facility or thermal plant has to be replaced. The tidal power plant offers other “dividends” because, contrary to coal-fired plants, it is free from sulfur dioxide and carbon dioxide pollution, acid rain generation, water pollution, oil spills, waste products treatment, and decommissioning expenses.
Development of low-pressure air turbine technology, on an industrial scale, was urged already some time ago to strengthen hydro-pneumatic power plants’ competitiveness (Baker and Wishart 1986, Cave and Evans 1986).
The electricity production costs calculations sometimes favor the tidal plant, or are said to be about the same as those of conventional or nuclear plants, while the conventional stations are CO2-polluters. Capital costs remain high for a tidal power plant but the longevity of the tidal plant is given at 75 years compared to 25 for a fossil fuel thermal central and between 30 and perhaps 40 years for a nuclear one.
Economic evaluation is made for construction costs per kW and generation costs, this being annual cost/annual electricity generated. The latter can be reduced by increasing annual electricity generated and/or by reducing costs of equipment, dam construction (not applicable for tide current schemes).
If E represents the annual electricity generated, expressed in GWh, A is the surface area of the basin expressed in km, H the tidal range in m, and K a coefficient varying between 0.3 and 0.5, then
K = KAH2
Annual costs are estimated to be 10-15% of the costs of total construction. No other costs are to be added in the ase of tidal power, but for thermal power, the costs of fuel (coal, oil, etc) must be.
Generation costs vary considerably from one country to another in function of a. o. social conditions; comparisons are thence all but meaningless. In Japan oil, gas and nuclear stations produce electricity at the lowest price with coal costing slightly more; tidal power would cost 3-4 times more, making it, currently, unattractive. Critics of tidal electricity generation labeled the Canadian Annapolis-Royal “an expensive undertaking”.
Fig. 9.1 Environmental assessment and impact of tidal power projects