August 4, 2015
It is a hot day in July. The temperature outside is reaching a record high. Inside your office building, the thermostat is set to a balmy 79 degrees Fahrenheit. And yet, you are not hot. Could this scenario be possible? The U.S. Department of Energy (DoE) thinks so.
Modeled after the Department of Defense’s DARPA organization, the Advanced Research Projects Agency-Energy (ARPA-E) is designed to invest in technologies that address the grand challenges of the energy sector. The challenge posed by the Delivering Efficient Local Thermal Amenities (DELTA) program was to develop technologies that allow the thermostats of commercial buildings to be raised in the summer and lowered in the winter without impacting occupant comfort.
The concept of zoning a home is widely understood to have benefits for reducing energy usage. With zoning, homeowners can control which rooms are kept at specific temperatures based on personal preference and which rooms are used most often. Bedrooms don’t need to be heated as much as living rooms, and the house can be warmer in the summer or colder in the winter during the hours when a person isn’t home. But retrofitting an older home for temperature zoning is expensive, invasive, and time-consuming.
The same challenge is true for commercial buildings. But is there a way to apply the energy-saving concept of zoning without requiring large capital investments? The DoE has thrown down the gauntlet and Syracuse University’s Professor H. Ezzat Khalifa along with a team of strategic partners answered the call. Khalifa’s team was awarded $3.2 million from the DoE and $319,000 from Empire State Development’s Division of Science, Technology, and Innovation (NYSTAR). Selected from a larger pool of proposals, Khalifa’s team is one of 11 total teams addressing this energy problem.
Thirteen percent of total U.S. energy usage—about 5.2 quadrillion British thermal units (Btu)—is attributed to building heating, ventilation, and air conditioning (HVAC) for residential and commercial buildings. This also accounts for about 13 percent of the U.S. greenhouse gas emissions. ARPA-E sought to explore an option that allowed buildings to reduce the energy used for heating and cooling by lowering the temperature to which buildings are heated in the winter from 70 degrees to 66 degrees and raising the temperature in the summer from 75 degrees to 79 degrees. ARPA-E estimates that doing so would decrease the energy consumed for heating, ventilating, and air-conditioning the buildings by more than 15 percent.
The Syracuse DELTA system will be a self-contained unit, smaller than a computer desktop tower, that is installed under an employee’s desk.
In cooling mode, the system works at night to freeze the phase-change material and, when the desk is occupied during the day, 79-degree ambient air will flow over the frozen phase change material, releasing the stored cooling as a gentle breeze of 72-degree air, which can be blown directly at the occupant.
In heating mode, the system works during the day to draw heat from the phase-change material and, using a heat pump, boosts the temperature of the blown air to a comfortable 85 degrees. The heat pump consumes less than 15 watts of electricity to deliver more than 60 watts of heat, thereby keeping the occupant comfortable in the 66-degree room. During the night, when the occupants are gone, the system works to melt the frozen phase-change material by drawing heat from the room and pumping it above the material’s melting temperature so it can be used again the following day.
The ARPA-E challenge required that these units be capable of maintaining a comfortable temperature for 10 hours, and that the units not use any more than 65 watts. The system that the Syracuse team is proposing should be able to meet the requirements using less than 12 watts in the summer and less than 15 watts in the winter.
This unit does not require any additional office infrastructure beyond a power cord to plug the unit in a wall outlet. If adopted by an entire office, this micro-environmental control system could save more than 20 percent of the total energy provided for heating and cooling in a building— exceeding the ARPA-E goal of 15 percent.
So, fear not. Your office may be warmer or colder in the future, but you will not be, thanks to researchers at Syracuse University.
Led by NYSTAR Distinguished Professor H. Ezzat Khalifa, the team includes collaborators at SyracuseCoE, United Technologies Research Center, Air Innovations, Cornell University, and Bush Technical.