ORNL, FEMP Collaborate to Design, Build, Demonstrate Smart Wall

Oak Ridge National Laboratory researchers demonstrated a first-of-its-kind smart wall that combines advanced manufacturing, building and power electronics innovation during the Department of Energy’s Federal Energy Management Program’s virtual 2020 Energy Exchange event.

The prototype wall, called EMPOWER, was built to highlight the event’s technology showcase. Designed for interior use, the EMPOWER wall demonstrates how an assembly of innovations serving as a room’s cooling system can reduce energy use, decrease peak time energy demand, lower energy utility bills, utilize renewable energy and maintain occupant comfort.

“EMPOWER realizes the power of possibilities, showcasing FEMP’s ability to work with national labs to deliver tangible energy-efficient solutions,” said ORNL’s Melissa Lapsa, 2020 Energy Exchange director and FEMP program manager.

The EMPOWER wall, which measures 5-feet by 8-feet, was 3D-printed at the Department of Energy’s Manufacturing Demonstration Facility at ORNL using a unique infrastructure scale additive manufacturing system called SkyBAAM that prints concrete. SkyBAAM is low-cost, cable-driven, field-deployable and can be adapted for any construction site.

“What makes SkyBAAM unique is that it eliminates the need for a gantry system commonly found in large-scale additive manufacturing systems,” ORNL manufacturing researcher Brian Post said. “This can be set up within hours at a construction site with minimal site preparation.”

Inside the EMPOWER wall is thermal storage and an active insulation system with a chiller that connects to the wall. Embedded pipes carry chilled water throughout the wall during low peak demand hours, cooling its interior temperature.

“Active insulation surrounding the thermal storage can vary thermal conductivity on-demand,” said ORNL’s Diana Hun, a buildings researcher. “It transfers coolness stored in the interior of the wall to the occupied space when needed.”

This on-demand capability of the active insulation reduces electricity costs by lowering the use of the heating, ventilation and air conditioning, or HVAC, system. The EMPOWER wall also uses a control method, called model predictive control, to optimize the operation of the active insulation and thermal storage based on the prediction of future conditions which can include weather or the occupant’s behavior.

Based on the control predictions, the optimal charging/discharge rate for the wall and timing can be determined. The wall’s embedded sensors can then send a signal to the existing HVAC system to turn on or off.

“By working in concert with the active insulation, this control method minimizes energy consumption and energy cost during peak demand times without compromising thermal comfort,” said Pijae Im, an ORNL buildings researcher.

A smart inverter, which is a power electronics device, powers the chiller connected to the wall and the pumps that transfer the cool temperature stored in the concrete to the wall’s surface. This inverter is connected to a battery that also stores energy from the building’s main power grid during low electricity demand times and allows the energy to be available when needed during peak demand times.

“The inverter introduces resiliency to the EMPOWER wall,” said ORNL’s Aswad Adib, a power electronics researcher. “By combining battery energy storage with a renewable source, the inverter can power the wall without dependency on the main electrical grid.”

The smart wall concept will be validated when two additional EMPOWER walls are built for installation in office buildings in fiscal year 2021. FEMP has collaborated with ORNL to produce the walls, test functionality and reveal field validation results during the 2021 Energy Exchange.

In addition to FEMP and ORNL, the EMPOWER wall project is supported by the Advanced Manufacturing Office and the Building Technologies Office in DOE’s Office of Energy Efficiency and Renewable Energy.