DOE’s BENEFIT Initiative Seeks Low-Cost Building Sensors

By Claire Swedberg

The U.S. Department of Energy is funding three multi-year projects to create either passive or active RFID sensors that can collect temperature, humidity or other environmental data for use by building-management systems.

The U.S. Department of Energy (DOE) has launched three RFID-based sensor projects as part of a $19 million investigation into identifying ways in which technology can make energy efficiency more accessible in homes, offices, schools, restaurants and stores. The Buildings Energy Efficiency Frontiers and Innovation Technologies (BENEFIT) initiative is funding a total of 18 projects, encompassing sensors and controls, heating, ventilation and air conditioning (HVAC) and related technologies, windows, building envelopes (the physical elements, such as doors and walls, separating a building's interior from its exterior) and energy modeling. The RFID projects fall within the sensors and controls category.

Heading one of the three RFID projects is Clemson University's development of passive ultrahigh-frequency (UHF) RFID tags with built-in sensors. Another of the projects, being run by Oak Ridge National Laboratory (ORNL), focuses on research into peel-and-stick sensors made with active 433 MHz RFID tags powered by photovoltaic technology. The third project, involving the Palo Alto Research Center (PARC), also consists of peel-and-stick sensors, using passive UHF RFID tags that can transmit temperature, humidity or other sensor data to a server when interrogated. PARC is also assisting ORNL with its project.

DOE's Marina Sofos

The DOE launched the BENEFIT initiative to identify low-cost technology solutions to improve buildings' energy-consumption rates. Each project is intended to yield systems that could reduce utility costs, decrease a building's carbon footprint and create jobs.

Most development work will begin this fall and is expected to conclude within two years, says Marina Sofos, the technology manager of the DOE's building technology office. "Each project is slated for two to three years," she says. Although wireless solutions for monitoring temperatures and other conditions within buildings are already available, Sofos notes, few are currently in use. Part of the challenge, she says, is in the cost of the sensors that could be used to monitor and thereby reduce the amount of waste associated with lighting, HVAC and other energy consumption. "The goal for the wireless sensors projects," she states, "is to drive down the cost of sensors."

By reducing the cost of installing, maintaining and operating sensors, the DOE hopes to accelerate the rate at which sensors are deployed in government, commercial and residential structures.

PARC, a research and development company owned by Xerox, is developing a sensor with printed antennas using technology devised through its Novel Electronics program, according to David Schwartz, PARC's manager of energy devices and systems. The data collected from the sensors will be managed by software provided by building controls solutions company Energy ETC. The sensors are expected to measure temperature and humidity levels.

The UHF-based sensor will come with silicon chips, a temperature and humidity sensor, and a printed antenna. The device is expected to be the size and thickness of a playing card. In the future, Schwartz says, it could also incorporate printed sensors. The sensor will be energized when interrogated by an RFID reader, and will use that reader's RF power to perform a sensor reading and transmit that data, along with its own unique ID number, to the reader, which can then forward the information to a building-management system (BMS) on a server to interpret it. Schwartz adds that he prefers to use the term RF to describe the technology, rather than RFID, because the sensors and reader that PARC is developing will employ a proprietary air-interface protocol, and the primary function will not be to identify the sensor, but rather to collect its measurements.

ORNL's Teja Kuruganti

The system will employ fixed readers mounted in rooms, Schwartz says, to periodically interrogate and power the sensors also deployed within those rooms. The reader electronics will be designed as part of the project, he adds.

Clemson University is working with Phase IV Engineering to develop a passive sensor manufactured by 3D printers. The humidity and temperature sensors will be printed, as will the RFID tag antenna, whereas the chip and substrate will not. This passive UHF RFID sensor will be powered by an interrogator that could be installed within the sensor's vicinity, says Hai Xiao, Clemson's S.L. Bell distinguished professor in the university's Holcombe Department of Electrical and Computer Engineering. Harvard University is also providing consulting services for the project, Xiao says. The sensor is being developed for use within commercial buildings, but could also be installed in homes, and could be interrogated by both handheld and fixed readers.

Phase IV's role in the project consists of adapting current long-range RFID sensor electronics to the new sensor that the research team is creating, explains Roy E. White, Phase IV's products and business development director. It also involves developing the data interface between the reader and the BMS.

ORNL is designing an active 433 MHz solution with sensors and RFID tags built into a single device powered by rechargeable batteries and indoor photovoltaic energy harvesting, says Teja Kuruganti, the lab's senior R&D staff member.

According to Kuruganti, ORNL is working with electronics manufacturer Molex to build a prototype of a sensor that uses a photovoltaic cell to draw energy from indoor lighting to power the tag's sensor measurements and periodic transmissions.

PARC's David Schwartz

"We were investigating very low-cost sensors that measure temperature, humidity and light levels," Kuruganti says. The goal is to create sensors could cost less than $10 apiece, he explains. Because the sensors are active, a typical facility would require only one or two receivers.

ORNL's work involves printing sensors on a plastic substrate with thin-film rechargeable batteries. While the lab had already developed printed temperature and humidity sensors, Kuruganti notes, the goal is now to make them more reliable so that they will continue to operate well long after the sensors are mounted in a building.

Additionally, the lab is building the receivers, and is working on interoperability with building automation. Initially, Kuruganti says, the system is being designed for small or midsize commercial buildings containing no building-automation systems.