Electric power failures in the aftermath of disasters cripple the delivery of critical emergency services. While emergency generators are available in some facilities, these systems are designed for short-term use and support limited functions. The substantial investment required to ensure emergency power for all critical services is difficult to justify because of the uncertainty associated with the likelihood and magnitude of future disasters. Investment evaluations change when a new source of emergency power is considered. This study evaluates the costs and benefits of a program to preemptively install new building-sited electric combined heat and power (CHP) generation technologies to ensure reliable long-term power for critical municipal services in hurricane-prone regions of the US. Three municipalities are selected for this analysis: Houston, Texas; Miami, Florida; and Charleston, South Carolina. Analysis indicates that costs of such a program can, in some cases, provide net energy bill savings regardless of the occurrence of a disaster.
Emergency generators in disaster-prone areas are typically designed for short-term use for only the most vital municipal services. Post-disaster health care, shelter and public safety are extremely limited and in some cases virtually non-existent, largely due to electric system failures (US House of Representatives, 2006). Evaluating the future benefits of more extensive emergency power systems as part of a risk management process is difficult because of uncertainty associated with the likelihood and magnitude of future natural disasters. The expected benefit of additional investments in emergency generation equals the product of estimated benefits and the probability of occurrence. The probability of a disaster at any one specific location is exceedingly small, resulting in limited expected benefits. Consequently, existing emergency generation systems are typically determined by minimal requirements specified in existing health and safety codes.
Cost–benefit calculations for expanding municipal emergency power capabilities can change substantially, however, by considering a different source of emergency power available with new building-sited combined heat and power (CHP) electric generation (US Department of Energy, 2000 and US Department of Energy, 2002). Instead of traditional emergency generator applications, these technologies are integrated in building energy systems to continuously provide some portion of a facility's electricity and thermal energy needs, including space heating, water heating and air conditioning. In the event of a power outage, these systems continue to operate, providing power for critical services. The economic benefit during normal daily operation helps offset some or all of their costs.
While CHP systems are widely recognized as useful for emergency power applications (Hordeski, 2005; Gulf Coast CHP Application Center, 2006), no analysis has been conducted to evaluate the costs and benefits of a program to preemptively install CHP systems to provide critical emergency services for an entire municipality. Economics of CHP systems depend on (1) hourly energy use characteristics of critical service buildings, (2) CHP system characteristics and (3) electric and natural gas prices. Under the right circumstances, CHP systems can provide net economic savings over time, reducing the cost of expanding critical services emergency power systems.
This paper evaluates the costs and benefits of preemptive municipal disaster preparedness programs to provide minimum levels of CHP-generated electric power required for critical disaster management, safety, health and temporary shelter services during widespread and prolonged central electric system outages in hurricane-prone areas of the US.
Three municipalities are selected for this analysis: Houston, Texas; Miami, Florida; and Charleston, South Carolina. These locations are all in the “strike zone” of Caribbean-spawned hurricanes and each reflects different climate characteristics as indicated in Table 1.
Table 1.
Characteristics of three study locations
Charleston Houston Miami
Mean January temperature, °C (°F) 8.8 (47.9) 11.0 (51.8) 20.1 (68.1)
Mean July temperature, °C (°F) 27.6 (81.7) 28.7 (83.6) 28.7 (83.7)
Population (2005) 106,712 2,016,582 386,417
Sources: Comparative Climatic Data, National Climatic Data Center, US National Oceanic and Atmospheric Administration, 2001, US Census Bureau, 2005.
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Variations in hourly heating and cooling energy use help determine system configuration and energy cost savings that can occur with CHP systems. As indicated in Table 1, Miami has by far the warmest climate in the winter season (January). All three locations are characterized by warm summer seasons requiring substantial air conditioning. Municipalities range in size from Charleston, with a population of 106,712, to Houston, with over 2,000,000 inhabitants.
The remainder of this paper is organized as follows. The next section describes new CHP technologies and potential CHP economic advantages relative to emergency-only generators. Section 3 identifies critical service building facilities used in the analysis and describes the development of hourly electricity and natural gas load data required for CHP system design and economic analysis. The next section discusses CHP system design and economic analysis methodology. Analysis results are then presented, with the final section providing a summary of this research.
