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16 Needs and Benefits Industry experts and airport and public transit stakeholders suggested that four project tenets or metrics were important to them: reliability, resiliency, affordability, and sustainability. Depending on specific design attributes, microgrids have the potential to fulfill all four project metrics, increasing power reliability and resiliency while reducing ongoing costs and carbon emissions. This chapter provides further context to these categories in relation to airports and public transit entities. C H A P T E R 3 Benefits to Airports and Public Transit Entities United Airlines suggested that the airline experiences power dips approximately once a month, and power surges cut out air conditioners and lighting 1â2 times a year and appear to be increasing in frequency. United recounts a recent power blip which resulted in three delayed flights and more than 100 mishandled bags. United Airlines (Internal Email) Reliability Airports and public transit operations can experience power reliability issues that result in power instability and poor power quality. A well-designed microgrid with an intelligent control system can ensure that utility power reliability does not affect airport and transit systems. Resiliency To continue operating through utility grid power disruptions, airports and public transit entities may rely on on-site backup generators. Issues with these power sources can include: â¢ Capacity constraints (e.g., existing generators not sized to meet all of the critical load). â¢ Distribution constraints (e.g., existing generators not connected to all of the critical loads). â¢ Continuity issues (e.g., transitioning from utility power to standby power creates an inter- mittent loss of power). A brief outage will cause sensitive electronic equipment to âre-boot,â creating a delay. The delay may create or elevate security concerns and delay travelers. â¢ Non-critical load disruptions. The loss of loads that are not considered critical and therefore not supplied by backup power prevents efficient use of the lavatories and other traveler comfort services. Combined, these issues contribute to the deterioration of the overall traveler experience.
Benefits to Airports and Public Transit Entities 17 Affordability and Cost Risk Reduction Cost is a complex aspect of energy projects because technology advances and market forces are decreasing the costs of microgrid systems while electricity and fuel costs are volatile. Future fuel costs cannot be accurately predicted, creating uncertainty about the true future costs of systems. Some specific areas of consideration related to cost include: â¢ Assets with low use: Generally, backup generators are seldom used. Burlington International Airport notes that even their 44-year-old generator has only 357.5 hours on it, indicating an average use of 8.1 hours per year. The economic case for assets improves the more they can provide services. â¢ Manual operations: Load shedding in response to utility requirements has been performed in some airports and transit facilities. In some cases, this is accomplished via a manual transfer switch to divert loads on to generators. Although automated equipment is costlier up front, it offers ongoing savings and efficiencies and is not prone to human error. â¢ Electricity price rise: Unpredictable electricity cost increases are possible, potentially caus- ing significant budget disruptions. Microgrids can offer protection against energy cost rises, especially with the use of renewable energy. Sustainability Most industries are now looking for ways that they can reduce emissions to help move toward goals of reducing greenhouse gas emissions and slowing global warming. The worldâs first global transport sector climate action framework was released in 2008 with the goal of stabilizing avia- tion CO2 levels beyond 2020 with carbon-neutral growth (ATAG n.d.). Many airports and public transit facilities are implementing energy efficiency measures, installing on-site renewable energy generation, and creating goals for further initiatives that include microgrid implementation. The transport sector represents approximately 17% of global emissions, with air transportation accounting for roughly 12% and non-road transport contributing 14% of the transport total (ATAG 2016). Although the majority of airport emissions are associated with aircrafts and landside vehicles, building-related emissions and electricity purchases make a sizable contribution (ACI 2014). The most cost-effective way to lower emissions is to invest in energy efficiency measures (Lazard 2015). Before establishing their microgrid, Burlington International Airport in Vermont identified targeted energy efficiency measures to reduce the power capacity needed for essential loads and to reduce cost. Burlington Electric Department Synergies and Trade-Offs Looking back at the four project tenets, synergies and trade-offs can be observed between the different metrics. Table 1 summarizes some examples of these synergies and trade-offs. Defining project goals and microgrid expectations at the beginning of a project is critical to developing a successful microgrid that meets the top objectives of the organization. Another consideration for organizations is that engineering optimality does not always align with economic optimality. Designing a system to capitalize on revenue streams increases project complexity and can result in systems that are larger than required to serve the microgridâs pri- mary loads. Evaluation of these trade-offs have become a focus point for the DOE.
18 Microgrids and Their Application for Airports and Public Transit 1 Gas infrastructure has been shown to take a lot longer to be repaired after serious damage (Lifelines Council 2014). This concern is more pronounced in earthquake-prone regions such as California. 2 In the reverse situation, maximizing revenue potential via offering ancillary services also can reduce the systemâs ability to be in a position to support its own loads during an emergency loss of utility grid power. 4 The benefit is a system that has been maintained and operated by an in-house team. 5 Other issues involved leaking fuel tanks, inaccessible fuel tanks, and lack of availability of fuel. The City of San Franciscoâs âSolar Resilientâ program is demonstrating that solar PV with battery storage can be an effective alternative to diesel generators for buildings designated as post-disaster shelters (e.g., schools and libraries) while lowering carbon emissions (SF Environment 2016). Tenet Tenet Synergy Trade-Off Resiliency Reliability Generally, measures used for resilience will increase reliability and vice versa. Introducing a co-generation plant or fuel cell system can offer resilience against an electrical grid power failure; however, these systems are still reliant on the main gas infrastructure, which can also be vulnerable.1 Resiliency Affordability Sustained outages can have greater business costs that the microgrid can offset, thus making the net cost of the microgrid lower. A conservative design approach with additional components and systems can increase redundancy and the robustness of the system but will also have cost implications.2 Resiliency Sustainability A system that is more resilient is, almost by definition, more sustainable because system life is maximized. Introducing a co-generation plant or fuel cell system shifts imports from electricity imports to importing gas. Depending on the location of the project, this may increase or decrease related emissions. Reliability Affordability Depending on the frequency and cost impacts associated with outages, increasing energy reliability through a microgrid can reduce cost impacts. A microgrid also offers a hedge against unpredictable and increasing electricity costs.3 A microgrid requires an array of components and systems that need to be maintained to ensure the reliability of the system. O&M tasks such as scheduled maintenance and monitoring are increased when compared to a utility grid connection, for which the utility is responsible for these duties.4 Reliability Sustainability In some cases, renewable energy generation can be more reliable than some fossil-fuel generators. During Hurricane Sandy, backup diesel generators at hospitals and datacenters failed to operate because of flooded generators or flooded basement fuel pumps (Hamblen 2012).5 Affordability Sustainability Sustainability often proves to be financially attractive for businesses. Many microgrids incorporate diesel generators, gas turbines, and gas fuel cells, which can provide benefits such as a lower up-front cost and a non-intermittent generation source. The up-front savings over renewable generation has an ongoing emissions consequence.6 6 Depending on the project location, the emissions associated with the on-site generation can exceed those associated with utility grid power. This is generally true of gas generation on the West Coast, but it is not the case on the East Coast because of varying percentages of renewable energy in the utility grid power mix. Transmission loss avoidance also should be factored into the equation. 3 A microgrid feasibility report conducted for Stewart Airport in Orange County, NY, found that an average yearly outage of 0.4 days represented the breakeven point for microgrid costs (NRG Energy, Inc. 2016). Table 1. Synergies and trade-offs matrix (Arup 2017).