Your choices so far:
1 Electricity; Electricity
| 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 | 1 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 | Local heating (ind. house) |
Electricity – un-threatened king of the energy carriers – is often supposed to be the main demand by the customer. The reason for this is that electricity is the most flexible of all energy carriers, it can be converted into heat, it can be used for cooling and it can be used for mechanical work.
In thermodynamic terminology, it is said that electricity has high exergy content, independent of the surrounding. Exergy is the kind of energy that can be converted, and since electricity can be converted it is obvious that the main part of the electrical energy is exergy. The remaining part of the energy is called anergy. The use, or the "consumption", of energy is really the successive loss of exergy through its transformation to anergy.
Using electrical energy is hence a simple thing: It can be used more or less for anything and in western and industrialised countries are the distribution grids expanded all the way out to individual houses with only few exceptions. Likewise, the distribution is simple: The electricity grid is there and what you need is to establish a connection point and connect your production unit.
Today, one may contract the delivery of different qualities of electricity. The contracting works
just like the bank system with its cash machines:
If you have a job and a salary, then your money is paid to a bank account by your employer and you can
withdraw the money from a cash machine almost anywhere. The bill you get from the cash machine has
– most likely – never even been touched by your employer, but it is still considered being
paid by the employer to you. This is achieved by regular balancing of all bank accounts between banks,
companies and individuals. These balances are done on a 24-h basis.
The same system applies to the electricity market:
If you have a contract for wind power, then your withdrawal (i.e. use) of electricity from the grid must
balance the input of windpower from your contractor. The balancing can be hourly, daily or any period
of time depending on federal and national law and on contract.
Because of this system it becomes meaningful to talk about the use of e.g. Danish wind power for e.g. the production of bacon in Spain or the use of solar-cell electricity from Cyprus for climate control in a hotel in northern Sweden.
Due to the unique features of electricity and the following difficulties to produce it, it should be produced only in processes best aimed for it and it should be used only in processes where the unique features are fully appreciated.
Electricity shall in the first instance be used for
- Mechanical work such as needed for lawn-mowing, pumping, fanning, compressing as well as evacuating or to run escalators, lifts and alike. In the longer run, this will also include transportation.
- Illumination.
- Operation of home electronics, computers, for communication devices and such.
- To obtain cryogenic/freezing as well as extremely high temperatures.
- For electrochemical operations such as electrolytic plating and alike.
- For operations and processes where the added value from the cleanliness, the simplicity and the precision of process control can be judged to override the thermodynamic arguments against it.
The last group includes such processes as home cooking. From a thermodynamic point of view cooking could just as well be done on wood stoves – but ...
Climate control using AC-units also falls within the last category and it does so because the district heating and cooling distribution systems in many cities and municipalities are still insufficient. However; once these grids are expanded, then should the AC-units be replaced by heat exchangers. For the house owners the system will still be just as clean, silent and easy-to-control, but from a societal point of view such a replacement will mean that electricity consuming devices are replaced by a system solution providing electricity production instead.
There are also a number of industrial processes in the last category where the use of electricity is not necessary from a process point of view and where the technical development during the last few decades already makes the replacement of electricity not only possible but advantageous and profitable and for the end-user there may well be reason to review the actual use of electricity in light of current development.
When the main aim of the energy supply is to deliver electricity to those customers that really need and fully appreciate it, then only large-scale production will be of interest and there will only be one energy carrier.
The technologies to be considered then become, in priority order: 1-hydroelectricity, 2-wind-power, 3-solid or digestible biomass in large-scale CHP or tri-generation plants. Solar cell electricity production is still too insignificant to be treated.