A number of alternative options for the provision of back up supply exist, including:
- Dual feed supplies
- Gas fired generators
- Fuel cells
- Biomass generation
- Solar/Wind generation
- Battery storage/Uninterruptible Power Supply (UPS)
Dual feed supplies rely on a second source of electricity from the grid company, and can mitigate local outages on the network. They will not be of use in the event that the wider network is without power, and therefore consideration of the source of outage is an important factor if choosing this option. The capital costs of the connection from primary substations can also be high.
Gas driven generators operate on a similar principle to diesel generators, but utilise natural gas as a fuel source. These generators require a connection to a natural gas supply, and so power is therefore dependent on the availability of gas. During natural disasters such as earthquakes the supply pipework can be ruptured making the generation unavailable.
Fuel cells operate by generating electricity from a fuel through chemical reaction similar to that of a battery. In contrast to a battery needs recharging, a fuel cell needs refuelling. Fuel cells can operate with a number of different fuels, have limited harmful emissions, and are a relatively quiet means to generate electricity. They do have a small foothold in the market, primarily for remote off-grid applications, although a few companies have trialled MW scale modular solutions.
Biomass generation uses technology similar to diesel generation, but utilises fuels harvested from sustainable plant sources, such as wood. They are not suitable for back up supplies, as they need regular use and maintenance to keep the feed mechanism working reliably, and suitable storage facilities for the wood.
Intermittent renewable energy sources such as solar photovoltaic or wind energy are unsuitable for backup power supply, unless they are just used for “topping up” a battery energy storage system.
Conventional battery powered uninterruptible power supplies offer “no break” power supply at loss of power, providing a bridge to allow diesel generation to start or allow equipment to shut down safely. The low maintenance requirements of modern battery systems, speed of response, and the high power quality make them technically very attractive. However, they are costly, and so are most commonly specified for short duration outages or in critical applications.