HVAC, water heating (WH), and other appliances represent more than half of the total energy used in U.S. residential and commercial buildings. As peak electricity demand continues to grow thanks to population growth, appliance growth, and air conditioning, additional R&D can help reduce consumption – avoiding costly new transmission infrastructure. BTO’s Grid-interactive Efficient Buildings (GEB) research offers the HVAC, Water Heating, and Appliance subprogram a major opportunity to enable new value streams and energy savings from innovative technology solutions and applications.
At the core of the technology being developed in the HVAC, Water Heating, and Appliance subprogram is the capability of the equipment to be responsive and dispatchable to both the electrical and gas grids while still providing occupant comfort. This subprogram is focused on developing energy-efficient equipment and components that are able to receive these signals from utilities and respond by adjusting their performance and energy consumption, particularly during periods of peak power demand. Today we are operating this equipment with on and off switches (0 or 100% loads) when most often something in between would be ideal for energy efficiency, occupant comfort, and the grid.
It is very common today for cars to have six-, eight-, and even 10-speed transmissions – but a lot of the equipment in our homes operates as if we were driving with single-speed technology. Rather than “driving” building equipment with an on and off switch, we’re looking toward the ability to vary the output of appliances without impacting comfort. The ability to respond incrementally to grid conditions allows equipment to operate at a lower output while still maintaining comfort. In winter during times of high heating (and grid) demand, furnaces and heat pumps would receive a signal to run at a slightly lower temperature for a slightly longer period of time, reducing overall demand. This helps shave winter peaking, enhancing the reliability of the entire grid when all the building loads across a region are managed.
The main technical challenges to achieving this vision is to develop equipment and technologies that 1) can continuously respond to part-load conditions, 2) have integrated thermal storage, and 3) have grid integration capabilities. We’ve found multiple pathways for success exist: Sometimes supporting state-of-the-art variable-speed compressor technology in HVAC is the ideal solution for this part-load efficiency requirement; other times relying on simpler components in an innovative configuration, like using robust single-speed compressor technology in tandem configurations to provide variable capacity need, is the ideal low-cost solution.
The subprogram is also developing transformative technologies for the future, such as nonvapor compression heat pumping technologies. Today’s direct-expansion compressors are complex and come in discrete sizes; even with variable-speed technology they are not fully able to track building (or water heating) loads. These next-generation heat pumping technologies are often modular and have the potential to scale in size. The availability to scale is an important feature that could enable these technologies to better track load and enhance grid-responsiveness. These alternative technologies, such as nonvapor compression, have the potential to enable better demand response and can reduce the issue of having oversized equipment in the field. This also could help expand demand response programs into more residential homes.
The incorporation of thermal storage into devices that previously didn’t have energy storage will also enhance the grid by reducing peak loads and add new functionality to several appliances, like off-grid operation or better thermal performance. One example is the thermoelectric heat pump recovery system being developed for domestic dishwashers, which extracts the waste heat from the drain water and recovers heat that would normally be lost during the drying process. The recovered heat is applied during the washing phases and end of cycle drying, saving energy.
We are also looking at systems like ORNL’s Ground-Level Integrated Diverse Energy Storage (GLIDES) system that are capable of integrating and using low-grade heat, and reducing the energy requirements of the AC systems and providing off-grid operation for a few hours. These types of systems enable smarter building-grid integration. Beyond this, GLIDES' use of low-grade heat, which would otherwise be lost in traditional HVAC systems, makes it more efficient. We are just starting to pursue energy storage as a means to save energy and reduce grid peaking events.
GEB research represents a vast opportunity for HVAC technologies to provide value and energy savings above and beyond simple operational efficiency. We are just starting to scratch the surface of what this potential will bring, but BTO is well-positioned on enhancing the reliability of the entire grid. Instead of building technologies such as air conditioners and heating systems being the cause of peaking events, our portfolio, impacting half of the total energy used in U.S. buildings, will leverage innovation and new technologies to bring about this grid-interactive efficient buildings future.