Occupancy sensor for controlling lights increases energy efficiency

17th August 2007

By: Christy van der Merwe


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Lighting accounts for 30% to 40% of a commercial build- ing’s energy costs, and the installation of so-called ‘intelligent lighting’ is one of the fastest ways to increase the energy efficiency and reduce the operating costs of commercial buildings, “thereby providing the biggest impact with the least amount of capital input”, Electro Sense director Emmett Green tells Engineering News.

For this reason, energy services company Electro Sense has seen the demand for its proactive energy management system increase dramatically over the last year, as the drive for ‘green’ buildings and the need to implement energy efficiency gather momentum in South Africa. This momentum is largely attri- buted to the fact that the energy crunch has intensified this year.

The Electro Sense proactive energy management system is approved by the Eskom demand-side management programme, which aims at reducing the growth of energy demand.

The company was named Energy Company of the Year in 2006 by the South African Association of Energy Efficiency, and also scooped the Eskom eta award for energy efficiency in 2006.

This tried and tested technology is a sensor-based system that controls lighting based on the presence of people in a room, and has been used in the US and Europe for decades, although it is relatively new in South Africa.

The mechanism makes use of three technologies, namely infrared sensors, micro- phonics, which detect sound, and high-frequency signals, which detect changes in a specified area. It is a combination of these technologies that ensures the best functioning of the occupancy sensor for controlling lights.

“Infrared sensors detect fluctuations in temperatures that occur when individuals enter the detection zone – even the slightest movement results in a temperature change and activates the sensors,” explains Green.

The system can also work in conjunction with electronic dimmable ballasts which consider ambient lighting, thereby dimming the lighting according to the lux value set on the system. The brighter the natural light entering the room, the less the lighting required.

Recently, Electro Sense undertook the retrofitting of lighting systems at the Dimension Data campus in Johannesburg. Studies under- taken here by the Tshwane Univer-sity of Technology have shown that an 85% decrease in lighting costs will save the campus over R25-mil- lion in electricity costs over the next ten years, which is a reduction of about 16% of the total electricity costs of the campus.

“This indicates the huge savings achievable. As it stands, this is a conservative estimate, calculated at a 5%-a-year escalation of energy prices,” adds Green.

This retrofit also curbs greenhouse-gas emissions generated through coal-based power generation, and is the equivalent of taking about 3 100 cars off the road.

Established in South Africa in 2003, Electro Sense is now starting to see a shift in the corporate attitude towards energy efficiency. Unfortunately, in new developments, the lighting budget is still often the first to be cut, because lighting is the last thing to be installed in the building. For this reason, 95% of the work carried out by the company is the retrofitting of existing buildings, and the installation of systems into new buildings accounts for only 5% of the work.

The company is now also focusing on launching a domestic range, which will soon be available in hardware stores. These systems will be completely do-it-yourself and easy to install, and will be marketed from a convenience angle, as well as highlighting safety and security.

“If we could simply eliminate the waste of energy caused by people leaving lights on when not needed, we would not be in the situation we are in now, where load shedding is needed,” says Green.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor



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