Brennverdi

Brennverdi, or calorific value, is the amount of energy released when a given quantity of fuel is completely combusted. It is typically reported per unit mass (MJ/kg) or per unit volume (MJ/m³) and depends on the fuel’s chemical composition and physical state. The value is used in energy balances, sizing of boilers and engines, and in comparing different fuels.

Two common definitions are used in practice: higher heating value (HHV) and lower heating value (LHV). HHV includes the energy that can be recovered from condensing the water formed during combustion, while LHV excludes this latent heat. Depending on the context, one or the other may be applied in engineering calculations. In Norwegian energy literature, brennverdi is often used as a general term for the energy content, with HHV or LHV specified when needed.

Brennverdi varies with moisture content, hydrogen content, and impurities. For example, dry woody biomass typically has a caloific value in the range of roughly 15–20 MJ/kg, while fossil fuels such as coal and oil can range from about 20–45 MJ/kg depending on quality. Gaseous fuels like natural gas have energy content per volume in the tens of MJ per cubic meter, varying with composition and pressure. The exact value for a given fuel is determined under defined standard conditions.

Measurements and representations of brennverdi are used to calculate fuel consumption, efficiency, and emissions in energy systems. When comparing fuels, it is important to specify whether HHV or LHV is being used, as this affects perceived energy content and system performance.

See also: Calorific value, Higher heating value, Lower heating value, Net calorific value.