ELECTRICAL POWER GENERATION SYSTEMS

1. Gas-firedpowerplant
A gas-fired power plant or gas-fired power station or natural gas
power plant is a thermal power station which burns natural
gas to generate electricity. Natural gas power stations generates almost a
quarter of world electricity and a significant part of global greenhouse
gas emissions and thus global warming. However they can provide
seasonal dispatchable generation to balance variable renewable energy
where hydropower or interconnectors are not available.

2. A cogeneration plant in Berlin

3. Basic concepts: heat into mechanical energy into electrical
energy
A gas-fired power plant is a type of fossil fuel power station in which
chemical energy stored in natural gas, which is mainly methane, is
converted successively into: thermal energy, mechanical energy and,
finally, electrical energy. Although they cannot exceed the Carnot
cycle limit for conversion of heat energy into useful work the excess
heat may be used in cogeneration plants to heat buildings, produce hot
water, or to heat materials on an industrial scale.

4. Plant types
1.Simple cycle gas-turbine
2.Combined cycle gas-turbine (CCGT)
3.Reciprocating engine
Gateway Generating Station, a combined-cycle gas-fired power station in California.

5. Simple cycle gas-turbine
In a simple cycle gas-turbine, also known as open cycle gas-
turbine (OCGT), hot gas drives a gas turbine to generate
electricity. This type of plant is relatively cheap to build and
can start very quickly, but due to its lower efficiency is at
most is only run for a few hours a day as a peaking power
plant.

6. Combined cycle gas-turbine (CCGT)
CCGT power plants consist of simple cycle gas-turbines which use
the Brayton cycle, followed by a heat recovery steam generator and
a steam turbine which use the Rankine cycle. The most common
configuration is two gas-turbines supporting one steam turbine. They
are more efficient than simple cycle plants and can achieve efficiencies
up to 55% and dispatch times of around half an hour.

7. Reciprocating engine
Reciprocating internal combustion engines tend to be under
20MW, so much smaller than other types of natural gas-fired
electricity generator, and are typically used for emergency
power or to balance variable renewable energy such as wind
and solar.

8. Greenhouse gas emissions
Gas-fired power stations emit about 500g of Co 2 per kWh of electricity
generated. This is about half that of coal-fired power stations but in
general more than ten times that of nuclear power and renewable
energy. Life-cycle emissions generally show a similar pattern, unless
skewed by methane emissions such as from gas leaks.

9. Carbon capture
As of 2019 very few power plants have carbon capture and storage or carbon
capture and utilization.
Hydrogen
Gas-fired power plants can be modified to run on hydrogen[8] and according
to General Electric a more economically viable option than CCS would be to use
more and more hydrogen in the gas turbine fuel.[9] Hydrogen can at first be
created from natural gas through steam reforming, or by heating to precipitate
carbon, as a step towards a hydrogen economy, thus eventually reducing carbon
emissions.

10. Economics
New plants
Sometimes a new battery storage power station together with solar power or wind
power is cheaper in the long-term than building a new gas plant, as the gas plant
risks becoming a stranded asset.
Existing plants
As of 2019 a few gas-fired power plants are being retired because they are unable to
stop and start quickly enough. However, despite the falling cost of variable renewable
energy most existing gas-fired power plants remain profitable, especially in countries
without a carbon price, due to their dispatchable generation and because shale
gas and liquefied natural gas prices have fallen since they were built. Even in places
with a carbon price, such as the EU, existing gas-fired power stations remain
economically viable, partly due to increasing restrictions on coal-fired power because
of its pollution.