Your choices:
1 District cooling; 2 Biomass (solid); 3 Comfortable indoor climate
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| Biomass (digestible sludge) | 1 District cooling | 3 Comfortable indoor climate |
| Biomass (fermentable sludge) | 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) |
District cooling is distributed by the aid of cold water. The idea with cooling to provide a comfortable indoor climate is then to "collect" surplus heat energy from all the rooms in the building and to put that surplus heat into the cold water.
Unlike the internal distribution of heat in a building, where hot water is either produced in a local boiler or via a heat exchanger connected to a district heating system and the hot water is distributed to the individual rooms and given the chance to heat up the room through radiators, floor heating or other systems, cooling cannot be achieved in the same way. It will simply not work to distribute cold water through the heating radiators and to trust that to give a comfortable and controllable indoor climate.
Instead, what is needed for a district cooling system to work is that the individual building is provided with a forced ventilation system. The inlet air to the building shall then be cooled by the cold district-cooling water via a heat exchanger prior to being distributed to the individual rooms. This requirement puts a limit to the usefulness of district cooling systems when it comes to single-family houses while it poses no restriction to the use in apartment houses, office buildings and alike.
The practical difference when the central climate control system in – for example – a school is replaced by district cooling is that the main, central, air-conditioning unit is replaced by a heat exchanger. For a complete climate control system, 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 cooling as compared to individual cooling 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.
To the customer it makes no difference how the cooling is actually produced.