Dyson College of Arts and Sciences

Attendant with this new concern for resiliency is a search for investments and policies that are economic and effective. There is a growing sense that the existing approach of relying on emergency and backup generators to hedge the risk of extended power outages may no longer be the preferred solution. In the next section we explore the advantages of continuously operating DERs as a strategy for enhancing community resiliency. III. The Advantages of Continuously Provided Power over Backup/Emergency Power There are numerous reasons to believe that microgrids and combined heat and power systems are a superior approach to power and thermal resiliency when compared with reliance on emergency generators. The CHP system runs continuously, providing an economic benefit to the site. The emergency generator is akin to an insurance policy. You buy it and hope you don't have to use it. The emergency generator may rely on diesel fuel that requires storage (tanks) and delivery. The period of power availability is contingent on the size of the tank, and the ability to get deliveries into an area that's operating under emergency conditions. The CHP system can continue to run, if gas supplies remain available. The CHP system may be able to operate for shorter periods on a stored fuel, (diesel, propane) as well. Emergency generators are tested for short durations and at infrequent periods. They are rarely subject to all of the variability in conditions that will occur over a more extended period of operation. If the future is one where we anticipate power disruptions that are both more frequent, and of greater duration, we need to analyze the relative efficacy of DERs versus emergency generators to perform under such conditions. Continuously operating CHP often runs with an availability rate in excess of 95%. Forecasting the relative effectiveness of CHP versus EGU's entails a probability of each's capability for meeting power demands over (probabilities of ) several days of outages. CHP provides "thermal resiliency" in addition to electric power. In winter, the heat and hot water that are a byproduct of power generation from the CHP system insure habitability at the host site. In the summer, heat driven cooling from the CHP system allows cooling demands to be met with a much lower site electric load. Due to code requirements, in many instances a CHP system cannot serve the purpose of meeting life safety requirements. However, even in such cases, CHP is able to provide backup power to a site at a much lower cost than backup generators. The CHP is serving a dual function of providing operating savings and offsetting capital costs of backup generators that would provide a similar degree of reliability for the host site. Compared with Emergency Generators: CHP provides continuous benefits to host facilities, rather than just during emergencies CHP can result in daily operating cost savings CHP offsets capital costs associated with investments in traditional backup power 34

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