Efficiency of Base Load Power Plants

[bgm]

interested in efficiency metrics with regard to our base-load infrastructure... this information is not readily available. I think that renewable stuff has its place only after we make the most of our base plants with load shifting. The base plants exist, and they waste energy. I simply do not know how much and a practicing NE would know.

 

[CWatters]

I think that renewable stuff has its place only after we make the most of our base plants with load shifting.

What do you mean by "make the most of"?

Reliability of supply is important but many would argue cost is equally important.

 

[anorlunda]

he base plants exist, and they waste energy.

What are you talking about? Assertions of fact like that should be accompanied by a link to an acceptable source.

 

[Windadct]

Typical Combined cycle plants are getting around 60% efficiency today.

This efficiency is not really the same as an efficiency of a PV panel, as this is relating to max conversion of solar energy, that we are "receiving" anyway.

For a fossil fuel plant - it is the percentage of conversion of the total energy in the consumable, and the byproduct and waste heat are only a concern when running. Also worth noting, the Fossil fuel conversion rate does not include the effort of obtaining and delivering the fuel... though I suspect this is a small part of the overall system efficiency, it does add considerable to the other impacts.

 

[russ_watters]

interested in efficiency metrics with regard to our base-load infrastructure... this information is not readily available.

It will take some effort, but much of this information is available from the EIA website. Note though that "efficiency" may not be a meaningful consideration for low or no fuel cost power. So you may need to refine what you are looking to know.

 

[CWatters]

Efficiency is useful when comparing one power station with another if they both burn the same fuel, but it isn't a particularly useful factor when they are burning different fuels. Things like the cost per MWh or the C02 output per MWh are more important.

Anyway the info is out there..

https://en.wikipedia.org/wiki/Fossil_fuel_power_station

Typical thermal efficiency for utility-scale electrical generators is around 37% for coal and oil-fired plants[3], and 56 – 60% (LEV) for combined-cycle gas-fired plants.

https://energyeducation.ca/encyclopedia/Nuclear_power_plant

Typical nuclear power plants achieve efficiencies around 33-37%, comparable to fossil fueled power plants. Higher temperature and more modern designs like the Generation IV nuclear reactors could potentially reach above 45% efficiency.[6]

In the UK offshore wind became cheaper than new coal plant about a year ago. Onshore wind is cheaper but faces much greater public resistance.

https://www.carbonbrief.org/analysis-uk-auction-offshore-wind-cheaper-than-new-gas

Two offshore wind schemes won contracts at record-lows of £57.50 per megawatt hour (MWh). This puts them among the cheapest new sources of electricity generation in the UK, joining onshore wind and solar, with all three cheaper than new gas, according to government projections.

 

[gmax137]

The power company guys typically quote "heat rate" figures, Btu/MWe -- how much heat energy divided by electric power out. This is just thermal efficiency is disguise. A lower number means better thermal efficiency. A modern gas turbine plant might be 7500 Btu/MWe; older ones or coal fired units are higher, like 8500 maybe. Most nuclear units make saturated steam so their heat rate is closer to 10,000 Btu/MWe. As mentioned, there's more to the story than this one parameter. Fuel cost (in $$) is obviously important.

I'm not sure this is what you meant, though. When you mention load shifting, that's a different matter.

... only after we make the most of our base plants with load shifting. The base plants exist, and they waste energy.

The "base plants" are the ones that run all the time. Their aggregate output is (or should be) just below the daily minimum load on the system. In the old days, the power company would decide which units to base load (they picked the ones that were cheapest to run). Today the politicians decide which to run (by making the taxpayers pay extra for the power from the "pet" plants).

 

[jim hardy]

Heat Rate is BTU/KWh , energy /energy
not BTU/MWe which is energy/power

gmax's numbers are reasonable.

My Nuke plant ran around 10,800, once when visiting at Indian Point i saw 10,400 .

My utility bought a natural gas combined cycle (gas turbine with heat recovery boiler) that had an advertised heat rate of 6,000 . But i never got to see whether it actually made that.

The BTU to KWh conversion is between 3413 to 3412 depending what source you cite.
Sp 100% efficiency would be heat rate of ~3413
and actual efficiency would be 3413/(heat rate)
so a heat rate of 10,000 is efficiency of 3413/10,000 X100 = 34.13%
and that combined cycle heat rate of 6,000 would be 3413/6,000 = 56.8%. That's fabulous !

The reason we use heat rate instead of efficiency is simple- it comes from the old method of measurement.
We track fuel input to the boiler - barrels of oil, tons of coal, cubic feet of natural gas, whatever we're burning that day
and multiply that by the heat content of that fuel as measured by sampling it and sending to our lab
and that gives us the day's heat input.
We also track KWh from the meters on the panel - they're similar to the one on your house
dividing the heat in by kwh out gives us heat rate .

Before computers this was done longhand on paper .
and that's why the old fashioned unit .

My fossil units ran in the 8,000's. That was before emission controls , 10.000 is more typical nowadays.

https://www.statista.com/statistics/186397/average-operating-heat-rates-by-source-in-the-us/
2016 statistics :

 

[gmax137]

Btu/MWe

Heat Rate is BTU/KWh , energy /energy
not BTU/MWe which is energy/power

thanks old jim, you are of course quite right! Sorry for the brainfart.

The BTU to KWh conversion is between 3413 to 3412 depending what source you cite.

The reason for the different conversion factors comes down to there being different "Btu" definitions. They are all "heat to raise one pound of water one degree F" but they vary in what the initial temperature is taken to be, 39F, 59F, 60F, etc. Since the specific heat of water varies with temperature, so too does the Btu, and hence we see 3412, 3413, 3412.14, etc. Btu/KW-hr. In the old days this didn't matter much since slide rules generally run 3 significant figures.