Data Loggers Measure Circuit-level Energy Loads in Government Offices

The Power of Government: Engineers are using small, battery-powered data loggers to measure circuit-level energy loads at NY state government offices

In order to keep New York state government running smoothly, its capital city offices need a steady, reliable supply of electricity, even during emergencies. When the State Office of General Services made the decision to replace emergency backup generators for their offices in Albany, the first challenge was for engineers to accurately assess the power needs for more than twenty buildings.

The complex includes the state capitol building, which is a 19th century blend of Italian Renaissance, Romanesque and French Renaissance architectural styles, as well as several high-rise office towers ranging in height from 20 to 30 stories. In the event of an emergency cutting the buildings from the main power grid, emergency generators would have to supply enough power for lighting and other essential services.

Ryan Thordson is an energy engineer working in association with the Office of General Services and the New York Power Authority, the state-owned power supplier. He is seated with the task of assessing the emergency energy load so that the 5-megawatt, multimillion-dollar generators can be sized correctly. And, he admits, a lot is riding on getting this right.

Thordson acknowledges that it’s possible to rely on the power utility to measure an entire building’s energy usage, but for this project, the engineers need finer detail. The challenge is to measure power requirements at the individual circuit level, which means collecting data from over 200 points spread over 20 buildings, all within the project’s timeline of about half a year.

Thordson’s experience with energy assessment and logging devices led him to recommend small, battery-powered portable data loggers for this project. The State Office of General Services purchased sixteen HOBO® Energy Logger Pro™ data loggers from Onset Computer Corporation (www.onsetcomp.com) and connected each with a pulse input adapter cable to a WattNode® kWh transducer. The transducer monitors current and voltage and converts them to a pulse proportional to kilowatt-hours that is then sent to the HOBO Energy Logger Pro, which logs the resultant data.

The data loggers, which are brick-sized, are connected via the sensors to circuits in a building’s electrical gear switch room, where they take readings once every minute, 24 hours per day. Once a week, Thordson downloads the data from each circuit into his laptop. When he connects the loggers to his computer via a USB cable, Onset’s HOBOware® Pro graphing and analysis software recognizes the logger and downloads the week’s data points in seconds. He then connects the loggers to new nearby circuits or moves them to another building.

He likes that the data loggers are easy to set up and use; it’s one of the main reasons why he chose them. The software is intuitive and automatically recognizes the logger and sensors when they’re plugged in. And, setting up the devices didn’t involve any programming or wiring.

Using small portable data loggers isn’t the only way the New York State Office of General Services could have gathered their energy load information. Thordson explains that they could have contracted another engineering firm to do it for $200,000-$250,000. However, by buying the loggers and doing the collection and analysis themselves, they will be able to do the study for about $25,000 – significant savings.

Another plus is that the company now owns the sixteen portable data loggers, and can use them again in the future. Since each unit has six plug-and-play data input channels, they are flexible and can be adapted for multiple monitoring requirements. The loggers’ ability to easily accommodate third party sensors, with the use of optional analog modules, is also beneficial, he says, since the engineers won’t know exactly what data-collection requirements they’ll have down the road.

The units have been successfully collecting energy-use data for a few months, and Thordson expects he’ll be right on target with providing energy profiles to the engineers responsible for sizing the generators.

He also predicts that such fine-scale energy use data will be increasingly important to the industry in general. Building managers and engineers usually rely on power utilities to meter usage, he explains, but the only way to have a quality energy management program is to have some kind of on-site metering. Knowing energy loads down to the circuit-level can translate to enormous cost and energy savings.