Your choices:
1 Comfortable indoor climate; 2 Biomass (solid); 3 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 |
| 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 | 3 Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
For any building outside such areas where district heating and cooling systems are feasible, 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. For cooling purposes in single-family houses and also in larger building there is no realistic alternative to the use of electricity-demanding compressor cooling.
For the use of renewable energy in combination with AC-units there is then only one alternative, and that is to provide at least part of the electricity need for the house by local, individual, generation.
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:
- First, the attainable electricity efficiency becomes low, 5-15%.
- Second, electricity will only be produced when the boiler is actually running.
Just assume an extremely cold day and the boiler running at 20 kW. With an electricity efficiency of 10%, the result would be 2 kW of electricity which will not even be enough to run the electric cooker. Also, during a summer day when the boiler is not running, the electricity production will be nil. The cost for the system will not be able to defend such a small added value.