Power generation??

[John120/240]

Isn't steam one of the most efficient methods to produce power? (Next to

falling water; Hoover Dam) So when you hear of of power plants burning

natural gas or fuel oil, are they heating water to make steam? Or do they

run a engine with said fuel to turn a turbine?

 

[hurk27]

Isn't steam one of the most efficient methods to produce power? (Next to

falling water; Hoover Dam) So when you hear of of power plants burning

natural gas or fuel oil, are they heating water to make steam? Or do they

run a engine with said fuel to turn a turbine?

I have heard of a few peeker plants that use a large diesel or natural gas engine similar to the ones on a ship for peek times, but for the most part the fuel is burned to make steam, the most efficient way to make steam is Geo thermal, then nuclear, coal, then natural gas, then your low grade fuels like bunker C then diesel.

From what I heard, theres a lot of research into bio fuels also that will also start coming into the picture.

A turbine is what the steam drives to turn the generator, so if an engine was used, it would turn the generator directly

 

[gar]

101129-2225 EST

John120/240:

Steam, or any other current method loosely described as a heat engine is not a very efficient means to convert chemical or other heat source into electrical energy. A long time ago the conversion efficiency was maybe 5% or less. Over the last hundred years by developing means to get a larger difference between the input temperature and the output temperature the efficiency has moved toward the 30 to 40 % range. Hard to make steam hotter than in today's large steam plants. Making the exhaust a lot lower is not very feasible. This temperature difference is what determines conversion efficiency. You study this in a thermodynamics course.

On the other hand you can convert mechanical energy rather efficiently into electrical energy. On large machines well into the mid 90% range.

Also when using the word efficiency you need to understand its meaning. In the last 50 years the efficiency of a gasoline internal combustion engine has not increased by 200%, but the popular press and politicians might lead you in this direction. The fact that a small light weight car can get 100 MPG vs a large truck at 5 MPG does not mean that engine efficiency has improved, but rather you are comparing apples with oranges, grossly different weights. In fact the truck engine might be more efficient than the small car engine. The big truck and its trailer with load might be 60,000 # and the small car 700 #.

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[cadpoint]

Heard a radio show where a teacher stated that power wise hydralic is the best pound per pound delievier of power in a closed system.

Which includes whales talking in the ocean, and or internet potential.

Most of our utilities system used to create power take a two part application to create power.

 

[randy263]

You don't need steam to drive a turbine. Water flow can spin a turbine directly, or expanding gas from combustion, as in a turbine (jet) engine. Turbine engines are used to generate power, without steam.

Steam is just a convenient way to convert heat into rotary motion, which is easy to convert to electrical power.

 

[randy263]

101129-2225 EST
A long time ago the conversion efficiency was maybe 5% or less. Over the last hundred years by developing means to get a larger difference between the input temperature and the output temperature the efficiency has moved toward the 30 to 40 % range.

You have to take efficiency in context. In many engines the maximum theoretical efficiency is on the order of 30-40%, so if you achieve those efficiencies, you have an ideal (i.e. perfect) engine. Of course a perfect engine is not possible, but those efficiencies are very close.

 

[kingpb]

Gas turbines running on natural gas are much more efficient than using a boiler and steam turbine.

The gas turbine alone GE Frame 7 machine is in the low 40's percent range, whereas the boiler and steam turbine cycle is in the 30's percent range, plus the gas turbine stack output is much, much cleaner. Keep in mind the boiler efficiency itself is in the 80's percent, but you have to look at the whole cycle.

When you combine the gas turbine with a steam turbine the efficiency of the cycle goes up to around 60%. This is accomplished by using the heat output of the gas turbine, passing it through a heat recovery steam generator (HRSG) to make steam then sending it through a steam turbine.

The popularity of the combine cycle gas turbine projects in recent past put a strain on the natural gas supply and gas prices shot through the roof. Many projects were canceled and plants already built became peaking plants, and were only used to meet peak demands, when buying power on the spot market made it economically feasible to operate them.

Currently, the gas turbine market is coming back due to the long-term projection that gas prices are stable and the green energy folks are pushing so hard for cleaner technology that coal projects have essentially disappeared.

 

[mivey]

Well said kingpb

 

[John120/240]

Thank You all. It's educational & interesting