AKF - Bulletins - Generators

Generators

Generators and associated energy plants are the main sources of electricity. Alternate sources such as photo voltaics, fuel cells, and windmills provide a small fraction of the energy needs.

To supplement or backup larger power generating systems individual buildings or communities may provide partial or total electrical generation on site.

The generation usually fits into three categories:

Emergency Power: This generation, mandated by code, requires alternate generator power to be transferred automatically to elevators, fire pumps, fire alarm systems and egress lighting. These generators usually allow for the evacuation of the building and in New York City are to have at least six hours of operating fuel. Once the building is evacuated nonemergency loads can be manually transferred to the generator.
Standby Power: This is usually a power requirement necessitated by business considerations and relates to providing power for data transfers and power to maintain an environment within the data space suitable for equipment operation.
Co-Generation: This is where a building or site will be independent of the utility grid and generate its own power as well as utilize the bi-product of the generation (steam, hot water). In these instances the utility grid may or may not back up the facility.

The utility companies have been supportive of facilities providing various degrees of generation and have adjusted rates and rebates to allow these generators to operate and supplement utility power grids in times of high usage.

Because of their wide spread impact recent power disruptions are initiating a rethinking of the use of generators on all types of projects to back up the utility power. For example the wide spread disruption of power forcing a quick evacuation of buildings may create more harm than allowing people to remain in the buildings. Consideration may be given to powering up the building to allow for a more sustained usage; this may be accomplished by increasing the size of generators and their associated source of fuel supply. This will allow a greater portion of the building systems to receive power during an occurrence and allow people to remain in place.

The two primary methods of providing backup to the utility supply are the installation of gas driven or diesel engine driven generators.

Gas driven units are normally not used for emergency or time dependent applications because they are dependent upon an outside source (the gas line) and if they are turbines, they can take up to 60 seconds to start.

Diesel engine driven generators are normally used because they maintain an on-site fuel source (storage tanks) and re-energize loads quickly (less than 10 seconds).

Generators must be maintained and tested under load on a regular basis. Load banks may be provided to overcome the problems of transferring sensitive loads to the emergency system for test purposes. In any case the units must be exercised under load to maintain their dependability.