Your choices:
1 Electricity; 2 Biomass (digestible sludge); 3 Process heat
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| 2 Biomass (digestible sludge) | District cooling | Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| Biomass (solid) | 1 Electricity | 3 Process cooling (< 0 °C) |
| Geothermal | Fuel: Gaseous | 3 Process heat/steam (50 - 150 °C) |
| Sunshine | Fuel: Liquid | 3 Process heat (150 - 1000 °C) |
| Water | Fuel: Solid | 3 Process heat (> 1000 °C) |
| Wind | Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
Electricity, because of its unique content of exergy (100% for all practical purposes) can be used to produce any temperature ranging from cryogenic to more than 3000 °C (in plasma torches). The flexibility is (should be) reflected in the price for electricity as compared to other, less flexible, energy carriers. Hence electricity should be used only for such processes where the uniqie features are fully appreciated. The way the electricity has been produced does not affect its properties as an energy carrier.
Keeping these restrictions in mind it still be possible to find a small manufacturer willing to contract locally produced electricity for environmental marketing reasons. The advantage for the company will then be that any claim that the electricity used is truly a local produce will have a high credibility.
The usability of electricity in industrial processes includes all temperatures:
- Freezing temperatures at process industries, such as a food processing industry, must be produced locally, on-site. This is not necessarily the same as to say that the production of freezing temperatures must be seen as an isolated or stand-alone process, but a system perspective must be adopted.
- 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.
- 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.
- Temperatures ranging from 150 to some 1000 °C are common in many types of industries like asphalt works, metal manufacturing and heat treatment, metal casting, glazing of ceramics end numerous others. CHP-plants and hot water boilers for the production of district heating, district cooling and electricity also fall into this category.
- For temperatures exceeding 1000 °C, such as glass melting, steel reheating for rolling, the burning of ceramics, building brick, cement and household stoneware alike, fossil fuel firing and electricity are the major sources of energy supply today. The drawback with electricity for some of these high-temperature processes is the absence of a hot gas which is often used to attain temperature uniformity. With electricity as the energy carrier, such gas (if needed) must be produced or provided by external means.