Stand-alone power system

Off-grid, off-grid, self-sufficient off-grid systems are fixed or mobile equipment, devices or local area networks to the power supply, which can be realized without access to a nationwide public grid. They are used where the connection to the mains is not possible or economical. Its operation is called island operation.

Although each system, which is fed on their own with energy, is in island mode, you do not use this term in the supply system of transport. With these but can, like in systems with network connection temporarily isolated operation occur when an auxiliary power source for longer standstill of the motor or a power failure is present ( nuclear power plant, hotel in a developing country ).

In areas with dense, reliable electricity grid, as in most of Europe, island systems are mostly technical devices with low power consumption, where a wiring would be more burdensome than the natural supply about with solar modules. Examples include parking meters, fences or toll - control bridges.

Power sources

Units with combustion engine

For higher current requirement also petrol engines (including biogas - powered) generators are usually coupled with diesel engines, rarely used, provide the country-specific mains voltages. Diesel generators or fixed diesel power plants are not particularly long-lived ( 1 to 2 years until the engine - overhaul) and have even at high utilization less efficient (about 30 %) than coal power plants. Examples of this are next to secluded little settlements and major events with high power requirements, or even remote stations. When fire brigade, and the Bundeswehr also diesel generators are used.

In order to guarantee a supply of which is designed for AC line voltage devices, a reasonably constant frequency of 50 or 60 Hertz is also necessary for stand-alone systems. This is achieved by the speed control of the generator or DC power sources ( solar panels, batteries ) by inverter.

Diesel engines are distinguished from, for example, gas turbines by a fluctuating less with the generated power efficiency.

Renewable Energies

The rising cost of fuel ( including transportation, about the refuge, about navaids or in Antarctica) and falling asset prices can renewable energy sources are more economical. The choice depends on the offer - water power for some mountain cabin, wave energy for the navaid, wind generator for the yacht, solar panels for the RV - and the power requirements: In the MW range, a wind turbine is significantly cheaper than a photovoltaic system. The bridging of low-profit phases succeed with batteries only briefly or at low power requirement, otherwise a combination of internal combustion engines in question, possibly fueled by biogas. Then it is called a hybrid system.

Consumer side, the acquisition of more economical devices be useful that can directly utilize the battery voltage of the isolated network if necessary. Sometimes it is possible to simply bypass a power supply, such as a notebook, remove duplicate losses only in the inverter, then the power supply to avoid. Electric heat is usually not useful.

For the supply of remote unmanned weather stations, beacons and for some spacecraft isotope batteries are used. Often these are used simultaneously for heating. They have a low efficiency, but a decades- long maintenance-free operation. The installed electrical services range from a few to a few hundred watts.