Your choices:
1 Comfortable indoor climate; 2 Biomass (solid); 3 District heating
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| Biomass (digestible sludge) | District cooling | 1 Comfortable indoor climate |
| Biomass (fermentable sludge) | 3 District heating | Electricity |
| 2 Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | Fuel: Gaseous | Process heat/steam (50 - 150 °C) |
| Sunshine | Fuel: Liquid | Process heat (150 - 1000 °C) |
| Water | Fuel: Solid | Process heat (> 1000 °C) |
| Wind | Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
The preferred fuel in large-scale district heating plants is solid biomass of some quality that is easily available in the region and that can be stored without excessive risks.
District heating is distributed by the aid of hot (>100 °C) or warm (<100 °C) water.
The internal distribution of heat in a building with a central heating system is often done so that warm water is produced in a local boiler and the warm water is distributed to the individual rooms and given the chance to heat up the room through radiators, floor heating or other systems.
In buildings without central heating systems the heat is instead distributed using warm air as the distribution medium. However, there will still be a need for hot-water production for tap-water and for hygiene.
The practical difference when the central AC-unit in – for example – a school or an office building is replaced by district cooling and heating is that the main, central, air-conditioning unit is replaced by a heat exchanger. For a complete climate control, the heat exchanger may need three circuits: one supplied with district cooling, one for heating of the ventilation air and one for the production of tap water, the latter two both connected to a district heating system.
For the customer one main advantage with district heating and cooling as compared to individual climate control is that the responsibility is handed over to a central, large-scale, production plant with 24-hour manning and professional personnel. Thus, the risk for breakages and the risk that the central AC-unit must suddenly be replaced at a high cost is minimised. The price paid is, of course, a fixed fee.