Your choices:
1 District cooling; 2 Process heat; 3 Biomass (solid)
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| Biomass (digestible sludge) | 1 District cooling | Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| 3 Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | Fuel: Gaseous | 2 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) |
Unless free cooling is available, district cooling systems are feasible only on conjunction with district heating systems. Since the customers will demand the system to deliver with extremely high demands on reliability, the system must be based on a resource that is not variable in time. Thus – though the system may well incorporate solar heating panels and a number of other sources, the base supply must be cheap and available in large amounts.
Also, district cooling production is never a stand-alone process, unless again free cooling is at hand. To take full advantage of the district cooling system, tri-generation should be applied and this, in turn, demands that the production plant is "big" – at the very least some 15 MW thermal or preferably bigger. This effectively excludes fermentable or digestible biomass as the main resources though they may well be integrated in the system together with solar heating panels or other supplementary resources.
Thus the basis should be solid biomass.