Your choices so far:
1 Process heat/steam (50 - 150 °C)
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| Biomass (digestible sludge) | District cooling | Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| 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) |
Many industrial processes, like food manufacturing, washing and several biotechnological and/or chemical processes require only modest temperatures like 0-150 °C. In very many cases will the companies themselves have their internal energy supply system, often centred around one or two small hot-water or steam boilers producing a heat carrier (hot water or steam) that is distributed around the production site. The customer demands now treated are industrial demands and only large-scale processes will be of interest.
Cooling and refrigerating temperatures can be produced basically in two different ways, by absorption cooling where the main energy supply is heat and only minor amounts of electricity are needed, or by compressor cooling machines where all the help energy is supplied as electricity.
From a thermodynamic point of view, the production of temperatures lower than ambient is complicated and requires exergy. The exergy can be supplied either as relatively small amounts of electricity in compressor cooling machines or via proportionally larger amounts of low-exergy energy carriers such as hot water in absorption cooling machines. From a system point of view, the supply of relatively smaller amounts of electricity may always seem the better alternative but in such cases when thermal energy is locally available close to the cooling/freezing needs, other solutions should be considered.
In case there is a need of chilling, say temperatures in the range 5-15 °C, then district cooling may well be used to supply the service. If available, this would always be the preferred way.
To obtain heating temperatures in the range up to 150 °C, only minor amounts of exergy are needed and the energy carrier should be chosen accordingly. Steam, hot oil, superheated water as well as low-quality (i.e. not upgraded) fuels like raw biogas can all be considered. Obviously, environmental constraints must be put on the use of low-quality fuels so that the outdoor air quality does not suffer.
For these temperatures, if available, district heating should be chosen.
District heating is distributed by the aid of hot water or, in some cases, steam. Most common is the distribution of hot water but if there is a demand for higher temperatures with one or more major customers, then steam distribution will be an alternative.
Obviously, electricity can be used also to provide low temperatures (up to 150 °C) and it is sometimes the preferred choice since it is simple to control, for example in bakeries, but from a thermodynamic perspective this is not optimal. If electricity is used, then it should originate from hydropower, from wind power or from a solid-biomass-fired CHP or tri-generation plant.
Another option is direct fuel firing using gaseous or liquid fuel. Both gaseous and liquid fuel can be produced from renewables, but the liquid fuel qualities, ethanol and FAME, will mainly find their market with the transport sector where the willingness to pay is the highest. Hence the liquid fuels will be excluded here. For gaseous fuel, the prerequisite from the end-user will be that the fuel is readily available and hence only such qualities that are made available through the European gas grid will be of interest. So this is upgraded biogas from anaerobic digestion.
Solid fuel firing could of course be used but will suffer from a complicated and expensive handling, so though this could well be motivated from a thermodynamical standpoint it is not feasible in practice.
In case the availability of the process heat is not an issue, then concentrating solar devices could be used – but assuming an industrial process with the corresponding demands on availability, this is not an alternative.
Hence the energy carrier should be selected with respect to the energy service desired but electricity is often the preferred choice because it is easy to control and it is clean at the end user. If the electricity was also produced in a hydropower station, NB a hydropower station where thorough environmental concerns have been taken, then the environmental impact through the whole production chain is minimised.