Your choices so far:
1 Comfortable indoor climate; 2 Local cooling (ind house)
| 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) | District heating | Electricity |
| 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 | 2 Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
For buildings in densely populated municipalities, heating and cooling are or should be supplied by district heating and cooling systems. With modern insulation materials district heating systems may become economical once the annual heat load in a geographical area exceeds approximately 10 kWh/m2 and year. For any building outside such areas, the only alternative will be to organise the climate control system locally.
Todays' air-conditioning units will provide air-borne heating as well as cooling in one single unit and often such units will be found in the individual rooms in single-family houses. This is one major mode for individual house climate control.
For the use of renewable energy in combination with AC-units there is mainly one alternative, and that is to provide at least part of the electricity need for the house by local, individual, generation. This can be achieved by anaerobic digestion, by solar cells, a micro-hydropower installation or by a small wind turbine.
In the case of a geothermal heating system, though, there is one more option. That is to – on hot days – allow part of the water from the geothermal well to bypass the heat pump and instead pass a heat exchanger where the ventilation air is cooled down prior to being distributed through the house.
Theoretically local electricity production from solid biomass can be achieved by the use of micro-turbines, Stirling engines and a number of other technologies, all which have been thoroughly investigated during the last decades but they all suffer from the same fundamental weaknesses, together rendering local electricity production from solid biomass non-feasible:
- First, the attainable electricity efficiency becomes low, 5-15%.
- Second, electricity will only be produced when the boiler is actually running.
The use of absorption heat pumps for individual house cooling will increase the total fuel demand seen over the whole year and only in such cases that the total fuel consumption is irrelevant can this be recommended.