Explaining tricky energy terms

It has been noted on several occasions that there seems to be some confusion in regard to relevant energy terms, for example when graphs and statistics are compared. Therefore it makes sense to explain same of the most often referred-to terms.

Primary energy describes the primary energy content of raw wood, crude oil or coal. Units usually are Joule and toe (tonnes of oil equivalent).

Primary energy consumption thus means its use directly at the source or more often crude energy that has not yet been transformed into useful energy such as heat or electricity. No conversion or distribution losses are considered in a value termed primary energy.

Secondary energy is primary energy after calculating subsistence and conversion and describes the secondary energy available at the system boundary of a power plant. For conventional electricity generation without heat extractions, only one-third of primary energy is actually converted into electricity and two-thirds are lost as waste heat. Distribution losses are still not included in secondary energy values.

Final energy is the useful, secondary energy available to the final user, for example heat (hot water) for a radiator or electricity from the plug at home.

Final energy consumption therefore includes all energy supplied to to final user and includes all sectors, such as households, industries, agriculture….Distribution losses are included.
Units: Final energy consumption is often measured in thousand tonnes of oil equivalent (ktoe).

Gross inland consumption is the total energy demand   satisfied and describes all inland energy consumption within the boundaries of national territory, including consumption by the energy sector (=primary energy), all types of losses and  all final energy consumed  (primary production + recovered products+ net imports + variations of stocks – bunkers).

Electricity produced is the amount of produced electric power, usually expressed in kWh (kilowatt hours). The difference between all electricity generated (=secondary energy) and the amount consumed as final energy is attributed to transmission/distribution losses.

Demand is also measured in kWh and is often tried to be predicted by electricity suppliers as to run their power station accordingly. Demand side management focuses on the idea that whatever doesn’t have to be use at peak times (morning and evening highs) should be programmed to run at a later time (a washing machine). This would reduce peak loads often supplied by peak load boilers running on more expensive and less sustainable fuel.

Installed capacity is the what a power station’s generator can produce in at any instance if it runs optimally. Its unit is Watt. So if the total windpower capacity installed in an area was 100 MW at most this wind farm could produce 100 MW * 24 hours/day * 365 days/year = 766.500 MWh p.a. (766.500.000 kWh) in theory. In reality it might have a 10% of that output of only 76.650 MWh p.a. (76.650.000 kWh) because (wind-) conditions often make it impossible to run at full power. Some goes for a thermal power plant with heat extraction that might not exploit its full installed capacity because the demand for heat simply isn’t there throughout the year.

I guess here are some of the trickiest ones explained but there might be another blog to clear up a few more such issues.

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