District heating is generally regarded as an environment friendly method of heat production and distribution. Heat is usually produced at a combined heat and power plant or a heat plant and then distributed in distribution networks using pipes to houses, industries, commercial buildings, apartment buildings etc.
The total amount energy delivered to a building is measured for billing purposes by the supplier of district heating using a heat meter. Heat meters can also be installed and used for energy measurement in heating systems similar to district heating substations. Heat energy meters or heat meters can generally be divided into two types. Flow rate dependent energy meters and constant sampling frequency meters. It is known how to measure and calculate total energy usage and the total power usage (P), in a heating system such as a district heating substation using different types of heat meters, where the heat meter uses the measurements from the temperature sensors and the flow meter, to calculate and integrate the total energy usage and total power usage (P).
Conventional heat meters do not measure how much of the total energy has been used for heating the building or how much of the energy has been used for heating tap water.
To give building owners and others an increased possibility to study and change the energy consumption behaviour, separate measurement of hot water energy consumption and energy usage for building heating is needed. Studies show that separate measurement of hot water usage make people change their behaviour and save energy. The experience in Denmark is that for blocks of flats that had only one meter per building, the installment of individual meters for every apartment resulted in reduced energy consumption.
An example of a previous known district heating substation is given in DE 3,533,160, which relates to a control arrangement for a central consumer unit connected to a district heating system, with a flow measuring device, temperature transmitters for measuring the supply temperature (Ts) and return temperature (Tr). And further an integrating device for calculating and integrating consumed thermal energy as well as a variable, flow-regulating valve for regulating the flow of district heating water through the central consumer unit.
In the majority of commercial arrangements it is the owner of the building who owns the district heating substation and the supplier of district heating who owns the heat meter. The heat meter owned by district heating suppliers are usually only used for billing purposes.
In order to separately measure energy usage for tap water heating and building heating using known heat meter technology, two heat meters would be needed complete with flow meters and temperature sensors. One of several ways to accomplish this with conventional heat meters would be to use one heat meter for measuring energy usage for building heating and one for measuring energy usage for tap water heating and then adding the measurements together in order to get the total energy used etc. Additional measuring devices, heat meter and their installment is costly. Because of this separate measurement as described above is not practical using conventional heat meters.