Scaling Hybrid Building Tech from Defense to Commercial Use: GTI Energy Webinar - September 9, 2025: Summary & Review

         This webinar explores hybrid technology for buildings, especially chiller plants and hybrid rooftop unit (RTU) systems that combine natural gas and electric heating technologies with adaptive, AI-enabled controls. Susan Stover, GTI’s Director, Defense, Energy, and Collaborative Programs, talks with Jason LaFleur, GTI’s Senior Program Manager of Building Technologies.

     Chillers, boilers, and heat pumps are being used in the defense industry for practical energy efficiency reasons. Resilient, reliable, and efficient building energy is important for military buildings. In these hybrid systems, there is also redundancy, which may be more expensive upfront but which also provides superior reliability, resiliency, and efficiency.

     Two large Illinois National Guard buildings that are over 100 years old were outfitted with natural gas heat pumps. This is an outdoor system that provides year-round heating and cooling. These were integrated with hybrid boiler and chiller plants. The gas heat pumps provided significant savings for cooling, reducing electricity costs.  

     Hybrid rooftop units (RTUs) can provide heating, cooling, and ventilation with a gas-fired furnace for backup. These are drop-in replacements for electricity access. The gas system comes on when temperatures hit 0 degrees F. 

      These units also switched over to lower-impact refrigerants, including R-32 and R-454B. The switch to gas can be done based on temperature, energy costs, or emissions. Electric to gas price ratios vary significantly in different parts of the country. One goal is to avoid peak demand periods. Sometimes the electric heat pumps and gas furnaces were used simultaneously. Emissions concerns depend on local sources of power generation. Electricity rates are an important factor. As shown below, these systems can provide about 26% total cost savings.

     They modeled costs in different states and regions based on heating degree days and cooling needs. They utilize smart fuel-switching controls. At what temperature the system switches to gas depends on energy costs and desired emissions. These hybrid RTU systems are mostly DOD demonstration projects that can be applicable to the commercial market. Commercial applications of gas heat pumps for buildings can be developed from the military demos and inform utility incentives.

     Q: Can extreme temperatures affect hybrid RTUs? A: They can reduce efficiency, but the system can be programmed to adapt and kick in when needed to keep environmental conditions the same in the building.

     These systems can also take advantage of dynamic power pricing to optimize costs. Power and natural gas reliability are factors as well. If one goes out, the other is available. Each project and each area will be different and unique based on power availability, costs, and climate. Smart controls can optimize.

 References:

Scaling Hybrid Building Tech from Defense to Commercial Use - September 9, 2025GTI Energy Tech Talk Data Driven Energy Systems - July 23, 2025 on Vimeo