- Thread starter Will Mcloughlin
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Discuss Voltage Optimisers is this going to save you ££££ what do you think in the Green Energy Forums | Green Energy Hub area at ElectriciansForums.net
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Got this today from one of the well known and respected building energy monitoring organisations:
"EXAGGERATED CLAIMS FOR ENERGY SAVING
I think we may be making some headway against the claims made for voltage reduction (VR), thanks to greater awareness of the concept of an energy balance. Put simply, reduced energy input results in reduced output; so when you see a Youtube video "proving" that you get savings on a fan motor from reduced voltage at various speeds, the reason is simply that it is a free-running fan (keep your eyes open during the opening sequence) and they aren't mentioning its reduced air throughput at reduced power.
But now that vendors are being challenged over the energy balance, they have had to change their tune. They now say that motor-driven equipment "becomes more efficient" at lower voltage, enabling it to sustain its output with less input energy. Can this be true? Let's take the case of a motor delivering its maximum output of 7.5 kW. If it has an IE3 rating it would be working with an efficiency of about 90%, requiring 8.33 kW of input power. Now let's suppose that VR saves 10% on the input power (bigger savings are sometimes claimed), taking it from 8.33 to 7.5 kW. That would be the same as the output power. Bingo! A one-hundred-percent efficient motor.
In reality of course, maintaining output at lower voltage will necessitate a higher current (watts being volts times amps) and this will increase the losses in the motor, making it less rather than more efficient, and raising rather than lowering the input power required for the given output."
I think we may be making some headway against the claims made for voltage reduction (VR), thanks to greater awareness of the concept of an energy balance. Put simply, reduced energy input results in reduced output; so when you see a Youtube video "proving" that you get savings on a fan motor from reduced voltage at various speeds, the reason is simply that it is a free-running fan (keep your eyes open during the opening sequence) and they aren't mentioning its reduced air throughput at reduced power.
But now that vendors are being challenged over the energy balance, they have had to change their tune. They now say that motor-driven equipment "becomes more efficient" at lower voltage, enabling it to sustain its output with less input energy. Can this be true? Let's take the case of a motor delivering its maximum output of 7.5 kW. If it has an IE3 rating it would be working with an efficiency of about 90%, requiring 8.33 kW of input power. Now let's suppose that VR saves 10% on the input power (bigger savings are sometimes claimed), taking it from 8.33 to 7.5 kW. That would be the same as the output power. Bingo! A one-hundred-percent efficient motor.
In reality of course, maintaining output at lower voltage will necessitate a higher current (watts being volts times amps) and this will increase the losses in the motor, making it less rather than more efficient, and raising rather than lowering the input power required for the given output."
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In the vast majority of loads the power will reduce with voltage, it does not stay constant. It is resistance which stays constant.
If power remained constant then dimmers would not work and a 240V lamp would light to full brightness on a 120V supply!
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Or even better a washing line!
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So explain how both an old type and a modern dimmer work. less power less light, same light, same power. S
Power is not energy.
Power = Watts not Volts - Same power, less volts, higher amps.
Energy = Power x Time - ususally kWh
To dry clothes requires the same energy.
Wind and sun are free natural sources of energy hence a clothes line.
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I only know how old type dimmers work im afraid, ive never yet worked with the modern sine wave dimmers as they haven't really made it in to the theatre industry yet. We're still mostly triac based phase angle control with a fair amount of thyristor dimmers still around.
But either way they all work by reducing the voltage.
I'm not sure what you're getting at here, I've not suggested that power and energy are the same thing anywhere.
The statement that reducing the voltage increases the current is only possible if the load has constant power, which it doesn't.
I=V/R so as the voltage is reduced the only way the current could increase is if the resistance decreased.
If current were to rise as voltage drops then the current would become infinite every time the AC waveform crosses the zero point.
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