Improvements to air conditioning of office spaces
People have been thinking about using Sleepbreeze's as an environmentally friendly means of achieving thermal comfort in offices. This got me thinking. Why would you do that?
Well the answer is pretty simple, but needs a bit of thought. Some years ago I was with a big defence company called QinetiQ. We moved offices from our battered (but loved) laboratories to state of the art open plan office accomodation.
A lot of planning went in to this move, in particular about the number of people, computers, printers that would be in the building. These were tallied up, allowing the architects to spec the size of the air conditioning plant needed.
It wasn't long before we started to notice that some people kept cooler than others, depending on where they sat.
Not a problem, thought the occupants - we'll bring in desk fans. The response from the architects was "Oh no you won't, the load on the air con system is finely tuned and won't tolerate it."
What they were getting at was the desk fans / pedestal fans / tower fans use about 60-100 watts, depending on their size. However, their efficiency is somewhere between 40-80%, depending on whether they are motor or belt driven. That means, roughly speaking, that for every desk fan brought into the building it was the equivalent of having an extra laptop or half a person dumping heat into the air con system! No wonder they got shirty with us.
So, getting back to "Why not use a desk fan to supplement air con", the answer is blindingly obvious. They actually put extra strain on the air con system, using up yet more energy. Granted, not as much as if you drop the temperature by an extra few degrees. But not the greatest implementation of what is otherwise a good idea.
If you want to go down the route of turning the air conditioning thermostat "up" to save energy and using local air flow to still maintain peoples' thermal comfort, then use a low energy fan!! Yes, there are ineffeciencies, ust as there are in a desk fan, but these are in proportion to the total energy used. So, 50% of our 4 watt personal cooler is 2 watts. 50% wastage of a 100 watt desk fan is 50 watts!
About 10 years ago I was at a conference in Yokohama and met Prof P O Fanger - famous for his work on thermal comfort. He was asked to reflect on changes we'd see in office life in the future. He proposed that fresh air would be pumped direct to each person, rather than through the whole room. Whilst he was actually talking about fresh air, as in O2 content, he wasn't that far off what people are now considering on the thermal side. Local air movement for personal, tailored comfort, leading to reduced operating costs and CO2 emissions.