From steam to sector integration
1st generation
The main characteristic of the first generation DH system was the transportation of heat with steam at temperatures reaching up to 200°C. The consumer groups were to some extent small urban industries that used steam in their processes and large heat consumers such as hospitals and big residential building complexes. The high heat content resulting in low mass flows was one of the main drivers for maintaining/applying this technology that was a normal way to design new DH systems until 1930.
2nd generation
The main characteristic of the 2nd generation DH system is that the heat is transported by pressurized superheated water at temperatures above 100°C. This is a significant difference compared to the 1st generation DH systems, where steam is used to transport the heat.
This generation enabled energy-efficient waste heat utilization from power plants, transitioning them into combined heat and power (CHP) plants. By using the waste heat from power plants, fossil fuel consumption was reduced by 50% compared to separate production of heat and power, as was done in the first generation.
The main driver for the development of the 2nd generation DH system was increased operational safety, increased efficiency of both the heat distribution and operation of heat plants and the possibility of using a wider variety of heat sources than the 1st generation.
3rd generation
The 3rd generation DH system brought about the material and labor lean components applied combined with generally lower temperatures (below 100°C).
The main benefit of the third generation DH system compared to the 2nd generation DH system is the increased energy efficiency due to lower operating temperatures and the reduced investment and operation costs due to more prefabrication, pre-assembly, and pre-insulation at the factory. Also, the fuel mix has been altered by feeding in greener and renewable sources, resulting in lower emissions.
4th generation
Following the 3rd generation, a new development path is characterized by transforming the energy system towards a sustainable and interconnected energy system. This system is based on a high share of fluctuating renewable sources for heating and cooling, smart integration of the energy sectors and at the same time reduced specific building energy consumption as well as supply and return temperatures.
