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YOUR STORY
Energy wasting 'criminal'
11/06/2007 12:28 - (SA)
Andrew Perkin, News24 User
With reference to your correspondent's letter regarding Noelene's electricity saving tips, permit me to respond.
I am a professional electrical engineer, and feel compelled to back up the statements made on TV. In particular, geyser management through application of a programmable digital timer outstrips the energy savings afforded by commercial or residential lighting management, by factor ten or more.
The modern residential geyser with a properly set thermostat (60 degrees, maximum) takes approximately 30 to 45 minutes to heat the volume of water, from cold to working temperature. It is unlike a kettle, which has to heat the water to boiling point, and thus works in accordance with the laws of diminishing returns.
During the eight or nine hours away from home, and the eight or nine in the evenings during which no hot water is used, the geyser continues to cycle, operating for roughly ten minutes out of every sixty (and slightly less during the day, or during summer, when ambient temperatures are higher).
This energy wasted is, frankly, criminal. It can be shown that using the timer to switch on the geyser at 05:00 in advance of the morning shower period, switch if off between 08:00 and 16:00, switch it on at 16:00 in advance of the nighttime bathing and cooking period and switch it off for the night at 20:00, has the potential to realise a water heating energy (and thus monetary) savings of 40%.
During the warmer daylight hours, the water retains some heat for general use. This phenomenon is improved if the geyser is well insulated.
A ripple effect
This technique should not be confused with municipal ripple control, an inelegant technique of peak lopping, applied by supply authorities, which only leaves consumers frustrated, as their geysers are switched off en-bloc at precisely the time they need hot water!
It is my view that the random coincidence of geysers being in the "managed on" position would far outstrip any peak demand benefit currently obtained through ripple control. In my opinion, geyser management could be used to strip 10% off this country's peak demand.
Unfortunately the technique I espouse is not universally applicable, since programmable timers require a degree of consumer sophistication, and a great number of households have totally random lifestyles, not suited to a timer working to a more or less consistent routine.
However I believe significant penetration into the population of geysers in service an be achieved, and with it, energy and peak demand savings.
In closing, a word regarding such a timer. Such a device needs to be sufficiently robust, to handle the operating current of the geyser. The device should be of the appropriate quality, and installed by a suitably qualified electrician, in order to comply with the national code for the wiring of premises. It should also come equipped with a manual override facility, in order to switch on the geyser for hot water required at odd times, or completely, over weekends.
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