Brains for buildings, packaged in a smart briefcase

Energy efficiency isn’t just about bulbs and appliances. It’s also about rooms and floors, whole homes and office buildings, managed down to the minute and the degree to minimize energy consumption without sacrificing comfort. A new device from a group of Berkeley engineers, working with electrical engineering and computer sciences (EECS) professor and CITRIS director Costas Spanos, advances that effort by making it easier than ever to monitor building conditions and use.

A sizable industry has evolved to address the systems side of energy efficiency, providing private consultations, energy audits and in-depth “retro-commissionings” to help building owners reduce carbon footprints and monthly bills through technological fixes that are more substantial than a basic lighting upgrade or thermostat adjustment.

Many options already exist for monitoring complex variables within a building — such as temperature, humidity and occupancy on a room-by-room basis — in order to squeeze more efficiency out of lighting, heating and air conditioning systems. Few, however, are accessible to homeowners and building managers who may lack the time or expertise necessary to set up a wireless sensor network or the wherewithal to pay someone else to do it.

But Berkeley’s new Building-in-Briefcase (BiB) system is “trivially” easy to deploy in just about any building environment, say co-developers Kevin Weekly (Ph.D.’14 EECS) and EECS graduate students Ming Jin and Ruoxi Jia. “The idea for BiB is that everything is in the briefcase, including the sensors and the router, and you can take the briefcase wherever you go,” Jin says.

Ordinarily, Weekly says, a building owner or manager would hire a company to install sensors at strategic locations, allowing data transmission over a low-power radio network. Such effort isn’t necessary with the BiB system, he says, which communicates via WiFi and comes with a plug-in router and eight battery-powered sensors capable of measuring temperature, humidity, ambient visible light, motion and, for some of the sensors, even carbon dioxide levels (which can then be used to extrapolate the number of occupants in a given space).

Each sensor covers between 25 and 100 square meters depending on the makeup of the room, meaning an entire briefcase is good for an office of about 30 people. All users have to do is distribute the sensors, power up the router and wait for the data and analytics to pour in through a centralized, easily accessible database.

“Now someone with little technical knowledge can bring in these wireless briefcase sensors and set up a wireless sensor network and do a survey quickly without all of that engineering expertise,” says Weekly, the platform’s primary developer.

The other benefit of BiB is reliability, he adds. WiFi networks are more tolerant of noise than low-power radio protocols and less prone to lose data during transmission.

There’s a caveat, though: the sensors, which can be programmed to collect measurements every 10 to 60 seconds, don’t transmit to the central database in real time. Instead, the WiFi module within each sensor switches on for only a few seconds at regular intervals, typically between one and ten minutes, and a built-in microcontroller with 128 kilobytes of RAM quickly dumps its memory.

This small latency is a tradeoff, but not a big one, because most users look at their data after the fact anyway, Weekly says. It also allows for a much longer battery life: up to nine years with one-minute sampling and ten-minute reporting intervals.

The project was funded by the Republic of Singapore’s National Research Foundation through a grant to the Berkeley Education Alliance for Research in Singapore (BEARS) program, and is part of the much larger Singapore-Berkeley Building Efficiency and Sustainability in the Tropics (SinBerBEST) program. It has already resulted in some 60 briefcases being deployed in government, commercial and school buildings across Singapore, where heat, humidity and air-conditioning demands are bigger issues than in Berkeley.

Looking forward, BiB sensors also can be used to aid attention and learning in schools and other public indoor spaces, known to be affected by temperature and carbon dioxide levels. “The classroom is an area that requires a lot of attention,” Jin says. While the team has no immediate plans to market and sell the device, he adds, “it can be commercialized in the future.”