Quality indicators for district heating networks

District heating networks are very common energy systems all over the world but only few studies have been carried out to assess their performances through quality indicators. These indicators express district heating performances through different points of view. Four ones are developed in this study: energy sources, efficiencies, heat delivering equipments characteristics and environmental efficiency as a sum up.
First, the only energy indicator generally used is the primary energy factor (PEF), which quantifies the primary energy use of a device. However it does not give a complete insight of the whole energy use of district heating networks. Two other parameters have to be stated for this purpose: primary energy efficiency and the energy share.
Second, district heating efficiencies are generally not been taken into account unless sometimes the only amount of heat losses. A first indicator is defined to quantify networks heat losses relatively to the amount of heat delivered to customers. To take heat plant efficiencies into account, a more global indicator is defined. Its definition is close to a seasonal efficiency and it permits comparisons with other heating systems.
Third, indicators have been defined for heat plants equipments. Their aim is to permit stakeholders to check networks management of district heating companies. Two indicators are defined: one measures subscripted power relatively to network length and the other one represents the fictitious number of plants working hours while maximum plants power was delivered all the year.
Finally, environmental efficiency is stated. This analysis can include different aspects: green house gas emissions, water use and other pollutants emissions. For both design and management of district heating networks, an indicator representing CO2 emissions appears to be the most suitable one. Expressed relatively to delivered energy, it can be seen as a sum up of previous indicators because result of bad performances increases these emissions.
In this paper, these eight indicators are defined and their use is highlighted by a comparison of four different Finnish district heating networks.