Focused Practice

I. Answer the following questions:

1. How many ocean energy sources are there?

2. Where can a cliff-mounted oscillating water column be used?

3. When is air forced up a funnel that drives a “Wells” counter-rotating turbine?

4. When is the air sucked back down into the turbine?

5. How is the Wells turbine designed?

6. When can tidal energy be harnessed?

7. What does OTEC exploit?

8. How many types of OTEC systems are there?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: Three types of OTEC systems

Unit 43 Grammar: Non-finite Forms of the Verb Word List:

1. pressure reducing station	станция, уменьшающая давление пара
2. high-pressure steam	пар высокого давления
3. low-pressure steam	пар низкого давления
4. cogeneration	совместное производство тепловой и электрической энергии
5. feedwater pump	питательный насос
6. turbine chiller	охладитель турбины
7. low-pressure header	камера низкого давления
8. to throttle	дросселировать, уменьшать
9. irreversibility	необратимость
10. by-product	промежуточный или побочный продукт
11. by-product power generation	выработка сопутствующей электрической энергии
12. to encounter	встречаться, сталкиваться
13. steam plant	парогенератор
14. peak	пиковая нагрузка
15. an increased reducing station throughput	увеличенная пропускная способность понижающих станций
16. demand	потребность
17. absorber	поглотитель

At pressure reducing stations

An industrial or central plant is often designed to utilize both high- and low-pressure steam. Maintaining a balance between high- and low-pressure steam requirements is critical to obtaining optimal performance from the plant as a whole. Feedwater pumps, turbine chillers and other equipment with high-pressure requirements must be carefully matched to low-pressure demands of absorption chillers, hot water heaters, etc. (This assumes that the steam flows through the high-pressure machinery to a low-pressure header for further use.)

If high-pressure needs are less than low-pressure requirements, then there must be a pressure reducing station (PRS) to throttle the steam from high to low pressure. The result of the throttling is so-called “lost work.” The lost work is the consequence of thermodynamic second law limitations and introduction of irreversibilities into the system. This throttling process in a PRS is a candidate for the use of cogeneration techniques.

Cogeneration is defined by Electric Power Research Institute (EPRI) as the simultaneous production of electricity and useful thermal energy in significant quantities from a common energy source.

The idea of cogeneration can be extended further. Rather than using heat energy which is a by-product of electrical generation, electricity can be generated as a by-product of steam generated for process purposes. This is called “by-product power generation.” This is the particular situation encountered with a PRS in a steam plant.

Lost work which results from utilizing the PRS can be recovered if a work-producing device, such as a turbine, is installed in parallel with the PRS. The turbine could be utilized to pump fluids, generate electricity, or perform other work functions.

The University of South Florida Central Plant was analyzed for PRS cogeneration. The reducing stations operate at their peak during the winter when there is a relatively high demand for heating and a minimal need for cooling. Consequently, the need for low-pressure steam for the hot water heat exchangers produces an increased reducing station throughput. During the summer, the large, non-condensing turbine chiller creates a high demand for high-pressure steam which translates directly into a large amount of available low-pressure steam for the hot water exchangers and absorbers and small need for the reducing station.