Dyson College of Arts and Sciences

If properly designed, configured and operated, these onsite generation sources, together with controls and processes to balance local power demand and supply can keep critical buildings, functions and infrastructure operating during grid outages. DER systems do not necessarily provide a higher degree of resiliency, as nearly all owners of PV systems discovered during Superstorm Sandy. Additional design, configuration, utility interconnection and operations are required to provide this service of enhanced reliability. Incremental investments, while providing an important new degree of functionality, add to the capital and operations cost of a DER system. The various onsite technologies each have advantages and disadvantages as resiliency measures for insuring the continued operation of critical infrastructure when the external power grid is down. Power generated in CHP applications, in most instances, utilizes natural gas as the input fuel to drive reciprocating engines, microturbines and gas combustion turbines. The additional measure of resiliency provided by CHP applications is contingent on the natural gas distribution system operating during emergency events that affect the electric power grid. Certain engines and turbines may be able to operate on stored fuels; diesel, or propane for instance. In the event that the gas supply is not available, or for functions that require immediate (10 second or less), start-up, these alternatives augment the performance capabilities of the onsite power system. Renewable resources, such as PV and wind, are subject to diurnal, daily and seasonal fluctuations. In the absence of storage, the reliability value of onsite renewables is significantly diminished. However, hybrid systems that combine CHP, PV, storage and enabling controls and system management algorithms can be a highly effective means of markedly enhancing the resiliency of a campus, block, or neighborhood of interconnected buildings and businesses. II. Emergency and Backup Power Systems The traditional approach to supplying power during outages is reliance on emergency and backup power from onsite generators. Codes and regulation at many types of facilities require emergency power (NEC Article 700) and legally required standby power (NEC Article 701). Emergency power is required for systems whose operation is essential for safety to human life. Examples include exit signs, emergency lighting for egress, power and lighting for fire command centers, power for automatically operated doors. Emergency power at hospitals serves specialized care areas such as emergency rooms, intensive care and coronary care units, in addition to functions mentioned above. 4 Legally Required Standby Power is for building systems that do not directly affect life safety, but where failure could interfere with rescue operations, firefighting, or create health hazards. Two other categories are identified in the NEC. Optional Standby Systems (NEC Article 702) are functions that do not create life safety concerns but the failure of which would result in significant operational or financial losses at the site. These functions could include communication systems, refrigeration, certain critical industrial or HVAC loads. NEC Article 708 adds a fourth category of backup power provided to "Critical Operations Power Systems" (COPS). This is power for specified loads (functions) at sites that have been designated as COPS, by municipal, state or federal authorities. 31

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