A paper presented at the Domestic Use of Energy Conference held at the Cape Peninsula University of Technology in 2006 written by Johan Delport discusses three ways to save geyser energy consumption:
- Install the geyser vertically instead of horizontally
- Install a geyser blanket and pipe insulation
- And most interestingly – he proposes the installation of a dual element (two elements triggered at slightly different temperatures) to off-set the negative effects of small withdrawals of hot water.
Small withdrawals of hot water waste disproportionally large amounts of energy because even though say only a litre or two is used from the tap, a larger amount of hot water flows from the geyser through the house piping before hot water is available. This hot water then cools in the piping and the energy used to heat it is simply wasted. In addition, the geyser element is switched on by the thermostat which detects the small drop in temperature caused by cold water flowing into the geyser to replace hot water flowing out.
The dual element concept reduces the impact of small water withdrawals to some extent because only one of the two elements switches on (the water temperature does not drop enough to trigger both elements for small withdrawals). The same happens when the heated water cools and the thermostat activates to reheat water in the geyser.
Another point made in the paper is that thermostats are simple devices that are prone to “overshooting” the set point temperature to some degree. A dual element reduces the amount of energy used to overheat the water for small withdrawals of hot water.
The paper claims a saving of 40kWh per month for a 4kW dual element (2x2kW).
These dual elements are designed to fit standard geysers and have been accepted by Voltex as stock items. They will be available at retailers such as Builders Warehouse within a few weeks apparently.
Click here to download the complete paper.