Giant offshore turbines and monster underwater storage bags mooted

Published: 05/04/2010

Professor Seamus Garvey of Nottingham University with his “energy bags” concept. Zero-carbon, renewable energy which is cost-competitive with fossil-fuel-generated sources is surely the holy grail of the engineering world.

University of Nottingham spin-out company Nimrod Energy is aiming
to prove that, far from being just a pipe dream, one new form of green energy could be in widespread use within 15 years and at a fraction of the cost
of its nearest competitor.

The technology – Integrated Compressed Air Renewable Energy Systems (ICARES) – has been in development since 2006.

It is centered on a simple premise: using giant wind turbines to compress
and pump air into huge undersea “energy bags” anchored to the seabed –
or geological formations where deep water is not available.

The high-pressure air would be expanded in special turbo-generator sets
to provide electricity as required – not just when the wind is blowing. It would see vast floating offshore “energy farms” created off the coastline around the UK.

Professor Seamus Garvey, the brains behind the idea, said: “The UK has abundant offshore renewable energy resource – enough to supply all of our energy several times over.

We also have a strong internal energy market – worth well over £60 billion per year. We have an economy desperately in need of rebooting its manufacturing base and an engineering capability which is the finest in the world.

Without an initiative like this, the UK will spend vast amounts of money (several times £10 billion) abroad even before 2020 to buy offshore wind turbines, and much manufacturing activity will go abroad with that.

Worst of all, we will pay substantially higher prices for that equipment than we really need to, and the UK energy consumer is going to feel that with sharp rises in unit energy costs over the next 10 years.”

Over the past year, Prof. Garvey’s research has apparently shown that,
by taking offshore wind turbines to a scale never before imagined – 230 m (755ft) diameter is the baby of the family – and considering some radical redesigns,
the total amount of structural material per kilowatt of rated power can be slashed, effectively cutting costs by a factor of four or more.

He believes it is possible to store energy at costs well below £10,000
per megawatt hour – less than 20 % of pumped hydro energy, the cheapest competing technology.

Testing of scale-model prototype energy bags has already commenced.
A research project funded with 310,000 euros (about £280,000) from the EON International Research Initiative has already funded the development of analysis and design tools for the energy bags and will provide further prototype testing
in seawater leading to an energy storage product that will be ready for use
in energy systems by May 2011.

Prof. Garvey added: “This is a classic case of a little foresight leading
to technology becoming available exactly when the demand appears.

The signals have been out there for years that offshore wind turbines need
to grow much larger and that energy storage is going to become the key
to integrating large amounts of renewable energy into the UK and world electrical power systems”.

Text B

Gas-turbine engine

Most gas turbines operate on an open cycle in which air is taken from
the atmosphere, compressed in a centrifugal or axial-flow compressor and then fed into a combustion chamber. Here, fuel is added and burned at an essentially constant pressure with a portion of the air. Additional compressed air, which
is bypassed around the burning section and then mixed with the very hot combustion gases, is required to keep the combustion chamber exit (in effect,
the turbine inlet) temperature low enough to allow the turbine to operate continuously. If the unit is to produce shaft power, the combustion products (mostly air) are expanded in the turbine to atmospheric pressure. Most of the turbine output is required to operate the compressor; only the remainder is available
to supply shaft work to a generator, pump, or other device. In a jet engine
the turbine is designed to provide just enough output to drive the compressor
and auxiliary devices. The stream of gas then leaves the turbine at an intermediate pressure (above local atmospheric pressure) and is fed through a nozzle to produce thrust. A simplified scheme of a gas turbine engine is shown in the figure.

An idealized gas-turbine engine operating without any losses on this simple Brayton cycle is considered first. If, for example, air enters the compressor
at 15 °C and atmospheric pressure and is compressed to one megapascal, it then absorbs heat from the fuel at a constant pressure until the temperature reaches 1,100 °C prior to expansion through the turbine back to atmospheric pressure.
This idealized unit would require a turbine output of 1.68 kilowatts for each kilowatt of useful power with 0.68 kilowatt absorbed to drive the compressor.
The thermal efficiency of the unit (net work produced divided by energy added through the fuel) would be 48 percent.

Words and expressions:

gas-turbine engine – газотурбинный двигатель

axial-flow compressor – компрессор осевого потока

combustion chamber – камера сгорания

burning section – секция сгорания

turbine output – мощность турбины

jet engine – реактивный двигатель

auxiliary devices – вспомогательные устройства

constant pressure – постоянное давление

thermal efficiency – тепловая эффективность

Exercise 1

Ответьте на следующие вопросы:

1. How do most gas turbines operate?

2. Is fuel added and burned at an essentially constant pressure in gas turbine engines?

3. Is compressed air bypassed around the burning section used to keep
the combustion chamber at quite low temperatures?

4. Is most of the turbine output required to operate the compressor?

5. Is in a jet engine the turbine designed to provide enough output drive
the compressor only?

7. Does stream of gas leave the turbine at an intermediate pressure?

8. What output would require the idealized turbine for each kilowatt
of useful power?

9. What is thermal efficiency of the idealized turbine unit?

Exercise 2

Заполните пропуски недостающими по смыслу словами, используя текст:

1. Gas turbine engines mostly operate on an … … in which air is taken from the atmosphere.

2. In gas turbines fuel is compressed in a centrifugal or axial-flow …
and then fed into a … chamber.

3. In gas turbines, fuel is added and burned at a … pressure with a portion
of the air.

4. If it is needed to produce shaft power, the … products are expanded
in the turbine to atmospheric pressure.

5. Most of the turbine output is required to operate the … .

6. In a jet engine the turbine is designed to provide just enough output
to drive the … and … devices.

7. In gas turbines stream of gas leaves the turbine at an …. pressure.

8. An idealized gas-turbine engine operates without any … .

Exercise 3

Соответствуют ли данные предложения содержанию текста?

1. Most gas turbines operate on an closed cycle in which air is taken from the atmosphere.

2. In gas turbines fuel is added and burned at a constant pressure with
a portion of the air.

3. Very hot combustion gases are cooled by additional compressed air.

4. Most of the turbine power is required to operate the compressor.

5. In a jet engine the turbine is designed to provide output to drive
the compressor and auxiliary devices.

6. The stream of gas in gas turbines leaves the turbine at an intermediate pressure and fed through a nozzle to produce thrust.

7. In idealized gas-turbine engine absorbs heat from the fuel at a constant pressure until the temperature reaches 1,100 °C.

8. The thermal efficiency of the gas turbines would be 48 percent.

Exercise 4

Используя текст, составьте высказывания с данными словами
и выражениями:

open-cycle gas-turbine engine; combustion chamber; constant pressure; burning section; combustion gases; turbine inlet; combustion products; atmospheric pressure; generator; auxiliary devices; intermediate pressure;
local atmospheric pressure; turbine output.

Exercise 5

Кратко передайте содержание каждого абзаца.

Exercise 6

Выделите пять основных идей текста.

Exercise 7

Составьте предложения, используя данные выражения:

axial-flow compressor; to bypass around; burning section; temperature low enough; to operate continuously; shaft power; to operate the compressor;
jet engine; to drive the compressor; stream of gas; atmospheric pressure; to absorb heat; constant pressure.

Exercise 8

Переведите на русский язык следующие предложения:

1. Gas-turbine engines operate on an open cycle in which air is taken
from the atmosphere.

2. Fuel is added and burned at constant pressure.

3. Additional compressed air is mixed with the very hot combustion gases.

4. The combustion products are expanded in the turbine.

5. The turbine output is required to operate the compressor.

6. In a jet engine the turbine is designed to provide enough output to drive the compressor and auxiliary devices.

7. The stream of gas leaves the turbine at an intermediate pressure.

8. Air enters the compressor at 15 °C and atmospheric pressure is compressed to one megapascal.

9. The thermal efficiency of this unit is only 48 percent.

Exercise 9