Your choices so far:
1 Comfortable indoor climate; 2 Local heating (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 | Local cooling (ind. house) | Transport |
| Residual oils/fats etc | 2 Local heating (ind. house) |
Due to the ongoing climate change, the summer need of electricity for cooling purposes is expected to rise significantly during the next few decades, calling not only for an increase in electricity production but also for electricity-saving measures.
For buildings in densely populated municipalities, heating and cooling are or should be supplied by district heating and cooling systems and co-produced with electricity. 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 used in Europe today. For individual house cooling outside district cooling areas, alternatives are few. But for heating purposes, the electricity-consuming AC-units should as far as possible be replaced by modern installations.
For sufficiently big farms, one alternative is the use of anaerobic digestion in combination with individual CHP production using internal combustion engines. Such systems may provide not only the main part of the annual heating needs but also a significant amount of the electricity, including what is needed for cooling.
For the use of solid biomass for local heat production there will be two main alternatives, pellet firing or wood-log firing.
Pellet firing systems for domestic use in single-family houses generally fall into two different categories, namely
- Burners to be mounted in hot-water boilers
- Self-contained stoves for air heating, containing combustion chamber, burner and day storage tank assembled. For some units the day tank might be separate while quite often all the parts are assembled in one physical unit
Both are commercially available as off-the-shelf units. The reliability with the commercial systems is high and the need for maintenance is low.
The most modern wood-log boilers are designed for downwards combustion and lined with ceramics. In these, the gases from the coldest log will pass down, through the bed of already burning and glowing material, so that the gas is maintained at a high temperature throughout combustion, leading to very low emissions of hydrocarbons. These boilers are also designed for batch firing, so that a specific load of logs are input, ignited and allowed to burn out completely. Hence a modern boiler saves a lot of manual work since it does not require a continuous feed as did the old boilers.
In case the building is equipped with geothermal heating, then the system needs only a minor modification: On hot days, when cooling is desired, allow the water emerging from the well to enter a heat exchanger through which the outdoor air for ventilation is taken. The outdoor air may then be cooled down before being distributed in the house and the water pumped down into the well may be heated to a temperature close to the outdoor temperature.
For a larger building the system would basically stay the same but there would be a need for multiple geothermal wells.
Water and wind – resources that should be used only to produce electricity – should not be considered for space heating production in the first instance.