1. Conversion of natural gas energy from **kWh** to **MJ**

By definition, power is the rate of doing work, i.e. consumed energy per unit time.

In terms of units of measurement, the following applies:

1 W = 1 J/s

1 kW = 1000 W = 1000 J/s

1 kWh = 1000 J

If we consider the fact that 1 h = 3600 s (60 min x 60 s), i.e. 1 s = 1/3600 h, it follows that

1 kWh / 3600 = 1000 J

1 kWh = 1000 x 3600 J

1 kWh = 3600000 J

Considering that 1 MJ = 1000000 J = 10

2. Conversion of natural gas volume from

Physical properties of natural gas depend on pressure, temperature and density of gas. For natural gas, the following general (ideal) gas equation applies:

p - gas pressure (Pa), 1 Pa = 1 N/m

V- gas volume (m

m – gas mass (kg)

R – individual gas (or gas mixture) constant (J/kgK)

T – gas temperature (K), ϑ - gas temperature (°C), ϑ (°C) = T (K) – 273.15

Concept of “

In its composition, natural gas is a mixture of the following gases:

According to definition,

For the purposes of measuring the calorific value of natural gas in the process of supply of this energy source, one uses the lower heating value (LHV) as the reference value. The state-owned company Plinacro d.o.o., as the gas transmission system operator in the Republic of Croatia (TSO), is legally obligated to measure the calorific value of gas in the transmission system. In the distribution area of Gradska plinara Zagreb d.o.o. (DSO), this is done at three locations: Zabok Pressure Reduction and Metering Station (gas imported from Slovenia coming from interconnector Rogatec), Zagreb West Pressure Reduction and Metering Station (gas coming from the Adriatic and from Slovenia) and Zagreb East Pressure Reduction and Metering Station (gas coming from gas fields in Eastern Croatia and imported gas coming from Hungary from interconnector Donji Miholjac). Natural gas from all sources is mixed in the pipes of the transmission system. By regulating the flow rate and pressure in the transmission system, the TSO regulates the quantity of natural gas coming from individual directions, and in doing so it affects the final calorific value of gas at metering points.

For the purposes of calculating the consumed volume of natural gas for a specific accounting period from

3. Conversion of natural gas volume from

Compressed natural gas (CNG) is sold in kilos (HRK/kg). Natural gas density is measured in kg/Sm