The U.S. General Services Administration (GSA) requested Federal Energy Management Program (FEMP) technical assistance (TA) to examine the potential for distributed energy resources at their facilities. Using the National Renewable Energy Laboratory's REopt® modeling and optimization tool, GSA assessed the possibility of these technologies to increase energy efficiency and reduce costs at Region 4 sites.
GSA Region 4 considered distributed energy resources across their portfolio of approximately 200 facilities, driven by a desire to reduce energy costs, reduce emissions, and meet federal renewable energy targets. GSA prioritized 22 facilities for analysis, based on factors such as roof age and total electricity consumption. Technologies of interest included solar photovoltaics (PV), distributed wind turbines, battery storage, combined heat and power, and geothermal heat pumps (GHP)—REopt's newest technology model. GSA sought to understand what current technologies are viable based on current market costs and which buildings would be good candidates for installation of these technologies.
The TA team used the REopt platform, an energy modeling and optimization tool for distributed energy systems, to assess these technologies at GSA Region 4 facilities in a two-phase screening.
- In the first phase, simulated load profiles based on annual consumption data and blended utility rates were used to screen opportunities for solar PV, wind, and combined heat and power across the 22 facilities prioritized by GSA. Based on phase one results and other considerations such as scenic or historic viewsheds (areas in line-of-sight deemed worthy of preservation against development), GSA down-selected five facilities for more detailed analysis in phase two, along with two additional facilities.
- In this second phase, hourly or sub-hourly load data, where available (five of the seven sites), detailed utility rate models, considering tariff structures such as energy charges, demand charges, time-of-use rates, tiered rates, and estimates of land, roof, and carport space for on-site technologies were used to refine the results. Phase two also expanded the list of considered technologies to include battery storage and GHP.
Several buildings proved to be viable candidates, and GSA included four of the seven facilities from the phase two analysis in their current energy savings performance contract Round 6 project with their Central Office. The selection of these sites was driven by analysis results, energy consumption, aging infrastructure, holding period, as well as other factors. The region indicated that they also learned a lot about renewables and selection criteria.
- This analysis used REopt's new GHP model to evaluate GHP at federal sites. It was helpful to hear from building managers who anecdotally validated some of the techno-economic assumptions related to HVAC cost savings facilitated by GHP.
- The team evaluated variations in National Institute of Standards and Technology (NIST) and U.S. Energy Information Administration electricity and fuel cost escalation rates. These rates had a significant impact on resulting system sizes and economics. Federal agencies are required to use NIST assumptions for life cycle cost analyses, but due to historically low interest rates, NIST's inflation rate default is currently less than zero and may not reflect the costs agencies may face.
- GSA indicated that they would be interested in learning to use the REopt tool themselves for initial screenings to help prioritize sites for more detailed analysis.