Unit 7. Tidal Energy

PARTI

• Read and translate the text below.

Over the past three decades the feasibility of using ocean tides t< generate electric power has been investigated at many sites.

Results suggest that the potential for economic development is small Of the approximately 22,000 TWh per year dissipated by the tides, 200 TWh is now considered economically recoverable and less than 0.6 TWh is produced by existing plants.

Six areas account for well over half of the potentially developabld energy:

The headwaters of the Bay of Fundy (Canada);

The Severn estuary (United Kingdom);

The Gulf of St. Malo (France);

The south-east coast of China; I

and Russian coasts bordering the White Sea and Sea of Okhotsk.

Other potentially feasible sites include the Mersey estuary and small­er sites bordering the Irish Sea and Bristol Channel (United Kingdom), the Gulf of Kachch (India), the west coast of Korea, the north-west] coast of Australia, Cook Inlet (Alaska) and the Gulf of San Jose (Ar-j gentina).

By far the largest tidal plant in service is Ranee (France), with a capacity of 240 MWand an annual output exceeding 500 GWh. Oth­ers include the 20 MW Annapolis plant in Canada, several small units¹ in China with total capacity of about 5 MW and a 400 kW experimen­tal unit near Murmansk in Russia.

Most designs, existing or proposed, have opted for a single tidal ba­sin to create hydraulic heads and propeller turbines to extract energy therefrom. Linked and paired basins have also been considered. Inno­vative approaches have included extraction of energy directly from tide races using a variety of prime movers.

The main obstacle to development is economic. Capital costs are high in relation to output: a consequence of the low and variable heads available at even the best sites. Heads available at the turbine vary throughout each tidal cycle, averaging less than 70% of the maximum. As a result, installed capacity is underutilized, typical capacity factors tending to fall in the range 0.23 to 0.37. Low heads imply that civil as well as mechanical engineering components must be large in compar­ison to output. For such reasons, tidal plants are likely to be practica­ble only where energy is concentrated by large tides and where physi­cal features permit construction of tidal basins at low cost.

Significant capital-cost reductions through improved design and construction techniques have been achieved over the past three decades. In China a somewhat different approach has been taken: tidal plants have been built as part of broader schemes of resource utilization — typically land reclamation or aquaculture.

In a world increasingly sensitive to environmental factors, tidal plants must avoid unacceptable impacts. Tidal power is non-polluting and in this respect superior to thermal generation. Beyond that, it is difficult to generalize. No serious long-term impacts are known to have been caused by the Ranee tidal power plant, but large developments in the Bay of Fundy would, it has been predicted, perturb the tidal re­gime, with impacts on New England shorelines.

In recent years, commercial acceptance of combined-cycle genera­tion based on combustion turbines has reduced the potential econom­ic and environmental costs of meeting future capacity and energy de­mands through thermal plants wherever natural gas is available at competitive prices. This has tended to increase the economic bias against tidal power.

Mother development with adverse implications for tidal power is the trend in many countries to adopt market pricing of electric energy ^and dispense with regulatory pricing. This in almost every case entails competition in the generation function. Under such conditions, com­petitors will be under strong compulsion to choose plant types having the shortest construction times and the lowest unit capital costs.

Such factors render construction of new tidal generation capacity unlikely during the near future, unless strong incentives such as emis­sion caps or carbon taxes are imposed.

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50 Section I. Power Engineeri:

Unit 7. Tidal Energy

VOCABULARY

feasibility осуществимость, выпол- obstacle препятствие

нимость to imply подразумевать

to investigate исследовать to predict предсказывать

estuary дельта, устье реки to perturb нарушать

to exceed превышать bias наклон, уклон

therefrom оттуда to dispense распределять

to extract извлекать to entail влечь за собой, вызывать

innovative approach новаторский to render изменить состояние чегс
подход либо

EXERCISES

1. Give the Russian equivalents to the following English word combinations fron
the text: 1

— ocean tides

— the largest tidal plant

— annual output J

— a single tidal basin

— innovative approaches

— tide races

— mechanical engineering components

— design and construction techniques

— tidal basins

— combined-cycle generation combustion turbines

— energy demands

— new tidal generation capacity

2. Find in the text the English equivalents to the following Russian word combinations:

— экономически возместимый I

— потенциально возможные площадки станций I

— быстрое приливо-отливное течение

— малый и переменные напоры

— капитальные затраты

— усовершенствованные методы проектирования и строитель-1 ства

— выработка с комбинированным циклом

3. Translate the following sentences paying attention to the difference in form and trans­
lation between Participle I and Participle II.

a) Of the approximately 22,000 TWh per year dissipated by the tides, 200 TWh is now considered economically recoverable and less than 0.6 TWh is produced by existing plants.

b) Most designs, existing or proposed, have opted for a single tidal basin to create hydraulic heads and propeller turbines to extract energy therefrom.

c) Linked and paired basins have also been considered.

d) As a result, installed capacity is underutilized, typical capacity factors tending to fall in the range 0.23 to 0.37.

e) In recent years, commercial acceptance of combined-cycle gen­eration based on combustion turbines has reduced the potential economic and environmental costs of meeting future capacity and energy demands.

f) Under such conditions, competitors will be under strong com­
pulsion to choose plant types having the shortest construction
times and the lowest unit capital costs.

4. Read the text above and make up a list of the key words and topic sentences.

5. Read the text and say whether the statements are true or false according to the text.

a) Results suggest that the potential for economic development is large.

b) Five areas account for well over half of the potentially develop­able energy.

c) By far the largest tidal plant in service is Ranee (France), with a capacity of 240 MW and an annual output exceeding 500 GWh.

d) Linked and paired basins have not been considered.

e) The main obstacle to development is economic.

0 Heads available at the turbine vary throughout each tidal cycle, averaging less than 70% of the maximum.

g) Tidal power is polluting and in this respect not superior to ther­
mal generation.

^b«Find the passages in the text where the following ideas are expressed. Translate the passages into Russian.

^a) The feasibility of using ocean tides to generate electric power has been investigated at many sites.

Section I. Power Engineering

b) Innovative approaches have included extraction of energy directljj from tide races using a variety of prime movers.

c) Commercial acceptance of combined-cycle generation based on combustion turbines has reduced the potential economic and en-| vironmental costs.

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