Closed-meshed energy measurement in the gas network

A system comprising:

• a flow sensor receiving a gas or gas mixture flow through a flow tube of the flow sensor, wherein a flow velocity, volumetric or mass flow are determined and a temperature (T) and a pressure (p) of the gas or gas mixture are detected;
• an ultrasonic sensor determining a sound velocity (cs) of the gas or the gas mixture, wherein a density (r) of the gas or the gas mixture is correlated from the sound velocity (cs) or is calculated with the pressure and the sound velocity (cs);
• a microthermal sensor positioned in an area without flow of the gas or the gas mixture at the microthermal sensor, wherein the flow through the microthermal sensor is not proportional to the flow through the flow sensor, wherein a thermal conductivity (λ) of the gas or the gas mixture at one or more temperatures is determined with the microthermal sensor, and wherein a thermal diffusivity (α) of the gas or the gas mixture at one or more temperatures is determined with the microthermal sensor;
• and
• a processor connected to the microthermal sensor to calculate an energy of the gas or the gas mixture based on a calorific value, the temperature, and a volume or mass flow, wherein specific quantities for gas quality in relation to the calorific value of the gas or the gas mixture is correlated from the density (r), the thermal conductivity (λ), and the thermal diffusivity (α) of the gas or the gas mixture.