Page 402 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Governmental Facility—Mission Critical 375

Black starts are avoided with load-shed controls that maintain the balance between
generation and load. The necessity for black start generating equipment in a CHP-COPS
must be figured into all cost analyses. An auxiliary generator system set up for black
start looks a lot like the idle emergency gen-set that a CHP-based COPS is intended to
replace in the first place. In some applications, the smaller black start generating equip-
ment may be used to offset the cost of higher capacity emergency generating equipment
as discussed in the next section.

Emergency Power
It sometimes comes as a surprise to many in the building industry that the requirement
for emergency power does not originate in the National Electric Code. As an installa-
tion code, the NEC only provides guidance on leading safety practice. Whether or not
an emergency generator, or other backup source is needed for fire pumps, egress light-
ing, fire alarm protection systems, or elevators is provided by NFPA 101, the Life Safety
®
Code . A related standard, NFPA 110, Standard for Emergency and Standby Power Sys-
9
tems, is adopted by reference into the NEC and the Life Safety Code. NFPA 110 classi-
fies backup power systems according to class, type, and level which distinguishes their
character according to occupancy type, the number of seconds required to start, and the
number of minutes required to operate, respectively. Any CHP system must be set up
so that power balance is possible within the time frames required by the application.
According to NEC Section 700.5, a backup or alternate power source may be used
for peak-shaving as long as it has the capacity to supply emergency, legally required
standby, and optional standby loads first. Whenever the backup (alternate) source is
temporarily out of service, a portable or temporary alternate source must be available.
A variation of this impairment mitigation requirement appears in the best practice doc-
uments of other industries.
To summarize: CHP-COPS can increase availability and security by
• Reducing the size of the emergency generators by allowing noncritical loads to
be supplied from the CHP system.
• Reducing the number and duration of emergency generator starts.
• Allowing more “business critical” loads to be kept on during utility grid outages
or disturbances. If there is a disturbance on the grid, the CHP prime mover will
adjust to mitigate it; if there is a voltage transient on the owners electrical system
(such as from a large motor start) the grid serves to dampen the mitigate that
transient.

Interconnection
Interconnection issues pervade all sizes of independent generation. In addition to oper-
ator safety and net metering concerns, all interconnections must accomplish smooth,
in-phase synchronous transfers between grid-connected and island-mode.
Utility engineering staffs are sensitive to interconnection technical details because
so much of the last mile of the macrogrid is still configured in central station fashion.
Traditional, macrogrid utilities operate in an economic space in which prices are admin-
istered; not discovered, and the cost of making changes to the last mile of electrical
distribution to accommodate customer-owned CHP has to be figured into the tariff
approved by the public utility commission.