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ENERGY EFFICIENCY CASE STUDY


Win 1: Turn off the emergency staircase lighting


The lights on the two 27-storey emergency staircases at Portland House were on all day, every day. There are 189 light fittings in total, each with a 30W lamp. Camsell says it was costing almost £5,000 a year in electricity just to keep the empty staircase illuminated. ‘We said to ourselves ‘this is wrong,’ he explains, so Camsell and Barrett set about finding a solution. It was not possible


to use a time clock- based solution to turn the lights off during the day because it was an emergency staircase. So they opted for a presence detection solution instead. The ESP Micro Sensor switch from Parkway Electrical Services uses microwaves to detect people and it had the addition advantage that it could be installed inside an existing fitting without the need for any modification. It was established that, if the motion


sensors turned off the lights for 90% of the time, about £4,500 a year could be saved. The sensors cost £8,500 installed, which gave him a payback of under two years, which was well within his 3.5 year cut-off.


With motion sensors to turn off the lights for 90% of the time, about £4,500 a year could be saved


Before the work started, the power consumption of the staircase lighting was recorded for a week. Again, after the sensors were fitted, power consumption was monitored. A graph of consumption showed the detectors were performing well, with one exception. Twice a week, at lunchtime, there was an unexplained blip on the power consumption graph. ‘We spent ages trying to figure out what was causing the problem,’ Camsell says. The mystery was solved by painters working on the stairs who had spotted one of


the tenants using the staircase for fitness training by running up and down it twice a week. Measurements confirmed the modification was saving £4,228 a year, which gives a payback of two years. ‘We’d have got down to 1.9 years payback if it wasn’t for that bloke running up and down the stairs,’ Camsel jokes. The system has been so successful that it will now being rolled out across all of Land Securities’ London portfolio.


Win 2:Turn off unnecessary lift shaft lighting


Camsell says he was waiting for the lift one morning when he noticed the service lights were on in the lift shaft. He assumed the lift was being serviced. The following morning the lights were still on; they remained on for almost two weeks. He checked the other five lift shafts; the lights were on in these too. Then he got out his calculator: in total there were 238 light fittings in the lift shafts, each with twin 58W lamps, giving a total lighting load of 29.7 kW. At an electricity cost of 8.5p a unit, lighting the empty lift shafts was costing him £60 per day. Camsell spoke to the lift company about energy wastage. There has been no problem since. Assuming the lift shaft lights are on for maintenance 10% of the time, Camsell says this no-cost intervention has saved him about £19,500 a year.


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£4,228 TOTAL ANNUAL SAVING


£19,500 TOTAL ANNUAL SAVING


November 2011 CIBSE Journal 41


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