Your choices:
1 Process heat/steam (50 - 150 °C); 2 Biomass (solid); 3 District cooling
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| Biomass (digestible sludge) | 3 District cooling | Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| 2 Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | Fuel: Gaseous | 1 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 concept of district cooling is to distribute, through under-ground pipes, cold water to the individual buildings. The cold water is then used in a heat exchanger in the building, providing a cooling of the ventilation air and thus replacing the electricity demanding compressor heat pump (the AC-unit) by a plate heat exchanger. As the cold water passes through one building after another is will successively be warmed from its starting temperature (say 5 °C) to a level when it no longer useful for efficient cooling (say 15 °C) and it is then returned to the central cooling unit, cooled to 5 °C and then circulated again.
The most attractive way to produce district cooling is to integrate the production of cold water with the production of hot water and electricity and thus to use the cooling need as a basis for new electricity production. This can all be achieved by the use of absorption heat pumps in a tri-generation plant. District cooling can thus be produced in district heating CHP plants using solid biomass as their main resource.
Obviously, the use of district cooling for process purposes is only an alternative if the plant is within reach of the district cooling network.
Outsourcing the energy production may also be advantageous from other aspects. The full responsibility for the energy supply is then handed over to a central, large-scale, production plant with 24-hour manning and professional personnel. Thus, the risk for breakages or un-planned stoppages is minimised. The price paid is, of course, a fixed fee.