Take the Test
Why is it so hard for our industry to accept the benefits and savings from Voltage Optimisation in domestic buildings?
In response to an article published in the October issue of Renewable Energy Installer, entitled “Taking the Test”, Chris Norman, Chairman of the Energy Services and Technology Association (ESTA), specialist group for voltage management and optimisation, explains why the conclusion drawn in this article was invalid.
Incremental Voltage
Whilst the incremental voltage from any one PV installation is only a couple of volts the cumulative effect of a number of arrays on the same distribution leg is much higher. Each array pushes up the voltage to the other arrays on the same leg which have to raise their voltage even higher in order to export.
The vast majority of LV sub stations have fixed voltage taps on their transformers and are unable to respond to a voltage increase caused by micro-generation. Should the Supply Authority reduce the tap setting on the transformer the supply voltage will drop below the regulated minimum in periods when the PV arrays are not generating. The net effect is that the Supply Authority cannot reduce the supply voltage and the prevalence of PV arrays is pushing the voltage up further resulting in supply voltages of above 250v during peak generation periods. The excessive voltage resulting from this effect causes increased energy consumption within homes and significantly shortens the lifetime of appliances.
The best way of handling supply voltage variability due to micro generation is to stabilise the house at 220V using a fixed set point Voltage Optimiser. VPhase manufacture the only domestic product on the market which does this.
Incandescent Lighting
Moving from incandescent lighting to LED lighting will give a bigger energy saving than voltage optimisation, however the choice is not mutually exclusive. LED lighting yields an energy saving of around 10% under voltage optimisation with no loss of luminescence so the best option is to do both. The Carbon Trust paper is incorrect in a number of respects including its assertion that there is no energy saving from reducing the supply voltage for LED’s. The Carbon Trust’s assertion arises from the assumption that there is no energy saving from voltage controlled devices; in fact there is generally a saving of around 5% due to the reduction in losses within the voltage control circuitry.
Devices Used For Heating
There will be no energy saving from these devices, appliance lifetime will however be improved.
Flat Screen TVs
As per the comments above on voltage controlled devices, there will be some saving but it will be small. There is significant variability from device to device with some devices yielding 7% but most in the area of 2 or 3%.
Fridges and Freezers
Testing cooling devices is difficult to do because their energy consumption is significantly influenced by the ambient temperature, the number of times the doors are opened and what is placed inside them. The only way to get a valid test result on cooling devices is to place them in a temperature controlled environment; pre-condition them for 24 hours with the doors closed to stabilise the body temperature of the device and test for 48 hours using a fixed load and controlled door opening frequency and time. Without this level of rigour the energy measurements will vary quite wildly and provide grossly misleading results. EA Technology, a reputable independent test house, has undertaken testing under lab based conditions and savings of 13% have been confirmed.
Overall Savings Levels
Extensive independent field trials undertaken by VPhase consistently demonstrate savings of up to 12%. Lab based device trials and household modelling indicate that the savings that can be expected in a typical household is 8%.
Conclusion
The Authors conclusion is based on inadequate testing and is quite simply incorrect. Voltage Optimisation makes sense in both domestic and commercial environments, the saving provided by Voltage Optimisation is significant and easily justifies the investment in the technology. As voltages are pushed up further by micro generation and household electricity bills continue to rise the logic for installing Voltage Optimisation becomes more and more incontrovertible.
So why is there so much scepticism around voltage optimisation? Some of the reasons are:
• There is a lack of knowledge of how products respond to voltage variation. Devices do not always respond as you would expect.
• Ad hoc testing is yielding confusing results. Energy consumption testing is not easy and must be done in a controlled, professional and statistically valid manner.
• Some voltage optimisation product manufacturers have historically made exaggerated savings claims. These have served to undermine the credibility of the technology.
• Voltage optimisation has been inappropriately associated with often fraudulent plug in products which offer no energy saving benefits.
It is time for the electrical industry to move beyond all this and come to terms with the fact that domestic voltage optimisation is a serious proven technology that offers real benefits. Take the test by all means, but do it properly.