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Green machine: Hitting the lights in wasteful offices

Tue, 05/25/2010 - 5:24am
New Scientist

Most people instinctively turn off the light as they leave a room at home. But what about the office? Energy saving can seem a mite less vital when we're not footing the bill.

Here, perhaps technology can help ensure the lights and heating are not left on when the sun is blazing or no one is there to use them. Such systems can cut a building's energy use by an average of 40 per cent, says Jack Bolick, chief executive of San Francisco-based Adura Technologies.

The company has developed a wireless light-monitoring network, which gives companies owners control over their building's lights, without the cost of completely rewiring. The system uses information from occupancy sensors to turn off lights in vacant areas of the building. The system can also dim or switch off individual lights to coincide with seasonal changes in the hours of daylight.

Each light and sensor is given its own IP address, so it can be remotely monitored and controlled.

US businesses alone spend around $33 billion per year on lighting, so more efficiency could help companies' bottom line as well as cutting greenhouse gas emissions.

Smart choices

Systems that can turn unneeded lights off are already common, but by adding an internet connection, Adura also hopes to tap into the trend for smart electricity grids.

Such grids will enable utility companies to monitor energy use in minute detail, allowing them to alter the price of electricity as demand changes. In turn, companies could save still more money by remotely switching off lights when prices rise.

Because the system monitors the current flowing to each light, it can measure how much electricity is saved by switching them down or off, says Bolick. "I can give you your carbon footprint by cubicle, or by room."

Easy win

In a recent test by the Pacific Gas and Electric Company, simply giving employees wireless control of the three lights closest to their workstation, and allowing them to turn them on or off individually, reduced the electricity used by the building's lights by up to 72 per cent.

"We're doing lighting first, which is the most pervasive thing in the building," says Bolick. But Adura's environmental control system can handle terabytes of data, he claims, so could use other kinds of sensor.

For example, the company is investigating ideas such as sensors to detect when windows are open so that air conditioning can be turned down. Or sensors could monitor the current and voltage being drawn from each plug socket, to allow companies to more closely monitor their electricity consumption, and possibly identify potential savings.

It is also working with Cypress Envirosystems, based in San Jose, California, to control heating and air conditioning thermostats.

Dim the lights

At the Lightfair convention in Las Vegas earlier this month, Cavet Technologies, based in Toronto, Canada, launched its own lighting control system that can respond to requests from utilities to reduce demand by cutting the energy consumed by lights.

Its approach is to cut the current flowing to a building's lights at times of high demand – but to turn it on again so quickly that no one will notice. By introducing short on-off pulses in the current, electricity consumption can be reduced without reducing the level of light in a room, the company claims.

But Paul Mitcheson, an electrical engineer at Imperial College London, says there is a limit to how much electricity could be saved in this way, as reducing lighting by more than 10 per cent would make it noticeably darker.

A better method might be to use software to detect fluctuations in the grid supply, he says. When demand on the grid begins to exceed supply, the grid drops below its normal operating frequency – 50 Hz in the UK, 60 Hz in the US. Responding to those fluctuations would enable firms to avoid high lighting costs, he says.

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