**10. Conclusions**

of lower temperature. A larger fraction of fuel energy can yield high-quality electricity in‐

Electricity is widely used for purposes there district heating or cooling could be used in‐ stead. Electric heating is used extensively in Norway (Fig. 5) but also in several other coun‐ tries. Electricity is also generally used for air conditioning. Switching from electric heating or cooling to district heating or cooling naturally reduces the electricity consumption but if the district energy comes from a CHP plant the switching may also enable a larger electricity production there and less other electricity production is needed, which often is coal-fired condensing power plants. Thus, such energy-carrier switching influences the power system twofold through reduced demand and changed generation, which can lower fuel consump‐ tion and carbon-dioxide emissions. In Sweden, the use of district heating could be increased

by 25% if all electric heating in non-rural areas was replaced by district heating [14].

Seen from an exergy point of view, electricity should not be used for heating purposes. This is particularly obvious if electricity is generated with low efficiency and with fuels that are both costly and not environmentally friendly. On the other hand, it could be more difficult to argue against using electricity if the power is generated through hydropower with low production cost and without emissions. This is also one of the main reasons for the rather high share of electricity in some of the heat markets shown in Fig. 5. There are different rea‐ sons why there is a widespread use of electricity-based heating in some places but a shift to

**Figure 5.** Nordic heat market (Source: Norsk Bioenergiforening (NoBio)

stead of low-quality heat.

14 Sustainable Energy - Recent Studies

**9. Useful electricity use**

District heating is a comprehensive concept for heat supply from fuel through heat produc‐ tion and distribution to consumers. District heating systems are valuable assets, which ena‐ ble efficient resource utilisation.

The main advantages with district heating are low primary energy demand due to high en‐ ergy efficiency, high security of supply through utilisation of domestic renewable energy re‐ sources, if available, as well as small carbon-dioxide emissions thanks to low fossil fuel use and the high conversion efficiency.

District heating enables utilisation of energy resources that are difficult to use in single buildings and that otherwise may be wasted, such as industrial surplus heat, municipal waste and heat from generation of electricity in combined heat and power plants.

Incineration of waste with heat recovery to district heating may be used at very low cost. Surplus heat from industries can, instead of being wasted to air or water, be utilised in dis‐ trict-heating systems. District heating also gives opportunity for cogeneration of power and heat with high efficiency. District heating, thus, enables profitable heat supply with less en‐ vironmental impact.

District cooling from, for example, absorption-cooling devices saves electricity and may in‐ crease power production in CHP plants. To efficiently utilise biomass for energy purposes, it could be supplied to poly-generation plants where it yields, heat, steam, electricity, cooling and automotive fuel.

The use of, for example, biomass fuel decreases the dependency on imported fossil fuels. Ef‐ ficient plants need less fuel, which decreases the vulnerability of energy supply. Global warming and better houses reduce heat demand. Using district heating for additional pur‐ poses enables increased utilisation of energy resources that otherwise may be wasted.
