PowerSwitch

A local good cause organisation is proposing provide two voltage optimisers @ £700 each to public buildings. They say "These save an average of 10% on electricity costs per year."

Does anyone have any knowledge to support such a scheme?

I can not recomend any such devices.
Electricity is sold by the the KWH and in most cases reducing the voltage wont reduce the the number of KWH used to do a given task.

Different loads respond in different ways to reduced voltage and in general no saving results from reducing the voltage.

Incandescent lamps will use slightly less power but give a lot less light. The cost per lumen will be increased.
If the reduced light is acceptable, then simply use lamps of lower power.

Flourescent and discharge lamps on copper/iron ballasts will use less power but give less light. Cost per lumen about the same.
Starting may be less reliable especialy at low temperatures.

Flourescent and discharge lamps on electronic ballasts will give the same light, and use very slightly more power. Cost per lumen increased, though only minutely, less than 1%, but still an increase.

Switched mode power supplies will provide the same wattage output, but be very slightly less efficient. Running costs very slightly increased, but by less than 1%. Still an increase though.

Thermostatic space heaters and water heaters will use less power when running, but will have to run for longer to achieve the desired result.
Overall running costs unaltered.

Non thermostatic space heaters will cost less to run, but produce less heat in exact proportion. A "2KW" heater might only use 1.8KW but would produce less heat.

A fully loaded induction motor will draw more current, be less efficient, and run hotter with increased risk of failure.

A lightly loaded induction motor will perhaps be more efficient, and is arguably the ONLY appliance in which a saving results.

A commutator motor will run slower and therefore probably have to run for longer to do the same work.

Remember that these voltage reducing devices are transformers and that the user will be paying forever for the iron losses in the transformer.

In large premises voltage drop within the installation is often a problem and will be worsened by reducing the voltage.

Some users report significant savings, but normally only when a number of real energy saving ideas are implemented at the same time.
For example "we changed all our lighting to LED or T5 flourescent, installed presence detectors, and a voltage optimiser, our bill fell by 20%"

That's what I thought. Certainly that must be the case for a heating device, but the adverts claim that a motor can do it's task just as well with a lower voltage and therefore use less energy. I'm just rather doubtful. Having one's coffee grinder, vacuum cleaner, fridge motor etc running at a slower speed doesn't sound too bright. Or do AC motors run at a speed determined by the supply frequency and just have a lower torque at lower voltages? I'm a bit out of my comfort zone here. Incandescent light bulbs would be dimmer but what happens with CFLs?

edit: Ah, thanks Adam. I wrote the above before all of your post arrived.

Googling the subject mostly brings up sites from people trying to sell the kit. I found one electricians' forum with some pretty cynical posts on it though. The trouble is that some quasi-government and government-funded agencies seem to be pushing the idea.

A good qaulity CFL will work correctly over a wide voltage range, including the reduced voltage provided by a so called optimiser. The light output should be unchanged, the power used would increase very slightly, probably by less than 1%, but still an increase and not a saving.

Cheaper CFLs will use less power at lower voltages, but also give less light in about the same proportion.

The speed of an induction motor is determined primarily by the supply frequency, voltage changes have only a slight effect.
A fully loaded induction motor will therefore draw more amps in order to provide the same output at the lower voltage.

There may be a saving on part loaded motors.

Voltage optimisers are indeed popular in the public sector, but that shows how effective the sales teams are, not how effective the product is.
There may well be a saving in old offices with a lot of old fashioned lighting, but this is achieved by reducing lighting levels not by increasing efficiency.
If the reduced lighting is acceptable, then this may be achieved at much lower cost by useing lower power lamps, or even by removing some lamps.

Adam, I passed on your comments to the organisation concerned and have had this reply:

Thanks so much for that info. ...
I don't think we will find any public buildings with lightly loaded induction motors contributing most of the usage so we can forget voltage optimisers as part of the project.

PowerSwitch: 1
SnakeOil: 0

Thanks, glad to hear that.
If perchance they DO have any large and partly loaded induction motors, then it can be worthwhile to fit a variable speed drive to the motor, this reduces the voltage AND THE FREQUENCY supplied to a motor and can give a useful saving on large pumps and fans which have been oversized.
If however the motor is fully loaded then little is gained* by fitting a variable speed drive.

If the premises contain much lighting, then the £700 might be better spent on improving the efficiency of the lighting.

In all common circumstances, incandescent lamps, including halogen types should be replaced with CFL or LED.
Flourescent lighting though generally of good efficiency does vary quite a bit. It can be worthwhile to replace older flourescent fittings with new types.
As an example, many old flourescent fittings use a pair of 65 watt lamps each with a copper iron ballast that wastes 15 watts, giving a total use of 160 watts. This could be replaced with a modern fitting containing a pair of 58 watt lamps only run at 56 watts per lamp, on a twin electronic ballast with 4 watts loss, giving a total load of 116 watts for the same light.
And the lamps are cheaper and longer lasting too!

Failed flourescent fittings should almost allways be replaced with new high efficiency ones.

*on new installations it is common practice to fitt variable speed drives to all large induction motors.
Not so much for energy saving (though some people believe that a VSD AUTOMATICLY saves energy) but for other reasons.
A smooth and gentle start is achieved, thereby reducing the shock, vibration and wear and tear on the driven machinery.
The reduced current during starting reduces voltage drop in cables that may produce irritating lamp flicker elswhere in the premises.
If the motor is fully loaded, then power used is actually increased by about 2 or 3% due to the losses in the VSD.

biffvernon wrote:A local good cause organisation is proposing provide two voltage optimisers @ £700 each to public buildings. They say "These save an average of 10% on electricity costs per year."

Does anyone have any knowledge to support such a scheme?

These are not "voltage" optimisers as such; they're usually called power bosses. They correct the power factor of the supply which is, very simply, the inductive or capacitative phase shift of your alternative current supply such that the real power demand no longer syncs to the apparent demand and this allows power to pass unused from live to neutral.

The power boss tracks the supply current and the power demand and continually tunes the load's supply current to keep the power factor spot on. See here:
http://en.wikipedia.org/wiki/Power_factor

The more important point about these devices is that most fridges and other gadgets where power factors are a problem normally contain this type of circuitry as standard -- it's one of the cheapest and simplest ways of improving the eco-label rating. Consequently power factor measurement and correction is only an issue with older appliances.

However, saying that, I've got a power meter that automatically checks power factors, and I've done a few jobs in the past measuring the PF's of computers and power supplies in offices, and then replacing the power supplies with new ones I know have a good PF, and that will usually pay for itself in the first year. That's because office/works type appliances don't have the same drivers for optimising performance.

The voltage optimisers that I have inspected are simple transformers that reduce the supply voltage, nothing to do with power factor.

Power factor correction is a different matter entirely.
Large power users are charged a penalty for bad power factor and there is therefore a financial incentive to improve it.

In the case of domestic and other relatively small supplies, no charge is made for poor power factor and there is no financial gain by improving it.
A study of the electricity bill for domestic or other small premises will show no adjustment, penalty, fee, or charge for power factor. The bill is calculated purely on the number of KWH used.
Domestic and similar meters dont measure power factor.

There are numerous "snake oil" gadgets that claim to improve the power factor, some might even work, but wont save money in most buildings.

Different things - power factor correction is well worth doing and has been done for ages. Voltage "optimisation" is less convincing, as Adam says. A vendor of voltage optimisers I've seen before is http://www.powerperfector.com/ so take a look and see if the marketing is convincing or not...

This is concerning, Adam2. There's a product being pushed at householders quite heavily at the moment called VPhase. It won a prize recently from Shell. If what you're saying is correct then this needs to be publicised more widely. Are you aware of any research that confirms what you're saying?

I am not aware of any proper independant research, as distinct from claims made by the vendors of these devices.
However basic physics suggests that they are of little if any use.
Electricity is sold by the KWH, and in most cases a given number of KWH are required to achieve the desired result.
In somes cases a reduction in energy use WILL result, but only by reducing the output of heaters and lamps, not by any increase in efficiency. Reducing the voltage on say a fan heater WILL reduce the energy used, but will also reduce the heat output in exact proportion.
It could be argued that the user wont notice the reduced heat or light output, and a saving would therefore result. If however the user does notice, and selects more numerous or higher wattage lamps and heaters, then no saving results.
It would be just as logical to market 40 watt incandescent lamps as "energy saving" on the grounds that they use "33% less energy than 60 watt lamps" which is true, but they give less light in roughly the same proportion.
A kettle or an immersion heater will use less power whilst heating, but will have to run for longer. No detailed research is needed to show that the energy needed to heat a given volume of water is determined by basic physics.

Older electronic goods often contain linear voltage regulators, in such cases there will probably be a power saving as less electricity is wasted as heat in the voltage regulator, though in a few cases the appliance wont work at the lower voltage.
Most homes and busineses however wont contain many, or indeed any, loads with linear voltage regulators.
Virtually all modern appliances use switched mode power supplies, these operate correctly over a wide voltage range, and use virtually the same power at any voltage within this range.
To confirm this requires an accurate wattmeter and a variable voltage AC supply.

Cheers Adam. Your argument sounds very reasonable to me. I'll have a dig and see if anyone's done any whole house monitoring of these devices - would be useful to have a simple study to point people towards.

A couple of months ago I reported a supplier of magnets to be attached to cables and fuel lines to trading standards - with some immediate result!

The voltage optimisers are a bit more complex but from what Adam is saying I think a case may be brought against a fair few suppliers. The Advertising Standards Authority, who now have powers over internet advertising, may also be interested.

Here's an Australian paper which tested a range of domestic appliances at different voltages:

http://itee.uq.edu.au/~aupec/aupec04/pa ... erID77.pdf

Blimey they've managed to get support from some fairly big installers:

http://www.eagaheat.com/vphase-eaga

and apparently they're now accredited under CERT after a demonstration action was undertaken by SSE:

CERT Accreditation

CERT (Carbon Emission Reduction Target) is seen as an enabler to accelerate the adoption of our technology.

Over the last six months, an increased effort has been placed on securing CERT credits. The field trial results, as independently analysed by EA Technology, were submitted to Ofgem in October 2010, their peer review by AEA Technology was completed by December 2010 and our response to that review was submitted by the end of 2010.

On 21 March 2011 Ofgem confirmed that VPhase has secured a CERT measure based around its initial Demonstration Action with Scottish and Southern Energy ("SSE") and Ofgem; at 2.5 tonnes of carbon dioxide over a 20 year measure. The savings represent an excellent, proven approach to lowering household carbon emissions, yet the figure falls somewhat short of anticipated results, given that the device has been independently rated for a 36 year component lifespan. Other trials, for example Great Places and staff homes, have demonstrated carbon dioxide savings to be around 3.6 tonnes over a notional 20 year life. The CERT demonstration that was conducted in association with SSE has indicated energy savings of 5.2 % (6.3% for a gas centrally heated home). Whilst this is an important energy saving figure, the methodology upon which the Demonstration Action was based of 'day on/day off' is too easily impacted by day to day load variability in the domestic home which can be significant. Ofgem has agreed with VPhase that the 2.5 tonnes of carbon dioxide and 6.3% saving figures may be reviewed as further trial data is made available to improve the CERT measure beyond this current baseline.

I am aware that the Department for Energy and Climate Change ("DECC") is carrying out a consultation on the future of consumer electronics and appliances in CERT and that one of the scenarios being considered is that everything other than insulation and heating be removed from CERT. If this scenario was adopted then VPhase would no longer be able to utilise its CERT measure....

http://www.londonstockexchange.com/exch ... 22SN000895