solar panel confusion

dreaming

silverwhistle wrote: »

I'm a light user too (no TV, efficient lights etc.) and I'll have to get new white goods when I move back anyway, so will get efficient ones. Following Dreaming's comments I might get a washer/dryer as I'd forgotten that it can sometimes difficult to get things _properly_ dry in the UK!

To be honest I would not have chosen a washer/dryer - at least not the one I have as I have only successfully used it on towels. When I used it on jumpers it shrank everything. My old cheap separate tumble dryer was much more versatile but I don't have the space for it.
When I stop working I will be able to plan usage much better. As it was yesterday I generated 13.31 but most of that was exported as I was at work until 7. I must admit I never used to think about electricity and probably used to run everything together but for the past couple of years I have made a conscious effort to reduce my outgoings and make sure I only run what is necessary (to me!) now. Do I really need to have a clock on the microwave? That gets switched off at the plug now - although come to think of it do I really need a microwave? I know a lot of people here advocate a slow cooker to use the generated power - is that really more beneficial than having something simmering on a gas hob, or cooking 2 or 3 things in an electric oven? That might be obvious to others but not to me. How can I work these things out?
Keep us updated Silverwhistle.

Cardew

silverwhistle wrote: »

I used to work for a REC many, many years ago, and I remember in one of my first jobs explaining to monthly billing (maximum demand) customers that the possible reasons they'd had a higher bill were their poor power factors and/or switching on a bank of machinery etc. before another spike had finished, so I reckon I could be quite good at adjusting demand to output limits.:-)

Just in case that statement causes confusion, power factor is of no concern to domestic customers in terms of billing.

silverwhistle

A point probably worth making and hopefully my reference to maximum demand and 'banks of machinery' made the circumstances clear.

Mind you, I made an earlier comment on this thread about my ability to keep my usage under a certain level due to my experience here in Italy of having a maximum demand of 3.3 kw. In 6 years I think I've tripped the switch 3 times, and every time I believe , from the sound it made, it was when I had the washing machine on and the motor tripped in - not the water heater. As some of you will appreciate the load made by a motor is different to that of an immersion heater.

As for cooking with a slow cooker - remember there are other advantages over even a low gas. It can safely be left on whilst you're out and makes stews and such even more tender. Mine was lent to someone up the side of a mountain in dire straights and with a poor electricity supply, and I haven't seen her or it for ages, but I'd certainly get another. Microwaves are also useful if you already have one, but just need to be used appropriately.

A tumble dryer might come in useful just to finish off the odd item- my airing cupboard tank and pipes will obviously be so well insulated that I won't get any help there.

OffGridLiving

Cardew wrote: »

Just in case that statement causes confusion, power factor is of no concern to domestic customers in terms of billing.

Hi Cardew, are your comments connected with those voltage optimisation devices?

Cardew

OffGridLiving wrote: »

Hi Cardew, are your comments connected with those voltage optimisation devices?

No, simply to point out to those who might not appreciate that Power Factor is not a factor in domestic supplies.

Over the years there have been many scams where devices to lower electricity bills by xx% have been marketed. The 'technical explanation' (I use the term loosely) is that they lower the Power Factor.

There have been several threads on voltage optimisation devices. Whilst there can be small savings in a domestic situation, they are not likely to be cost effective as they cost £hundreds to install. Sadly Ohm's Law still applies.

OffGridLiving

Cardew wrote: »

There have been several threads on voltage optimisation devices. Whilst there can be small savings in a domestic situation, they are not likely to be cost effective as they cost £hundreds to install. Sadly Ohm's Law still applies.

Am I right in thinking that as they are there to reduce the voltage to 220v, that they act as a surge protector for all mains and lighting circuits?

[Deleted User]

Cardew wrote: »

No, simply to point out to those who might not appreciate that Power Factor is not a factor in domestic supplies.

Over the years there have been many scams where devices to lower electricity bills by xx% have been marketed. The 'technical explanation' (I use the term loosely) is that they lower the Power Factor.

There have been several threads on voltage optimisation devices. Whilst there can be small savings in a domestic situation, they are not likely to be cost effective as they cost £hundreds to install. Sadly Ohm's Law still applies.

Cardew - can I tap into your expertise?

Voltage optimisation devices... I've been told that I can shave 18% off my electricity bills per anum for £400 quid especially as I have an ASHP. Is this a lot of tosh?

Cheers

zeupater

jeepjunkie wrote: »

Cardew - can I tap into your expertise?

Voltage optimisation devices... I've been told that I can shave 18% off my electricity bills per anum for £400 quid especially as I have an ASHP. Is this a lot of tosh?

Cheers

Hi

In a domestic situation it's, let's say, somewhere between unusual & impossible ....

There is much confusion between power factor optimisation and voltage optimisation, so let's take a quick look at both within a domestic scenario ....

In the UK, for domestic supply, we are metered & billed in terms of energy supplied (real power) with the power factor therefore being irrelevant.

Electrical devices within your property will mostly fall into one of two groups - restive or capacitive - something like an electric kettle, panel heater, filament lightbulbs or toaster will be fully resistive, a fan assisted oven or fan heater mostly resistive with most electronics equipment, such as TVs, timer circuits, radios etc being capacitive ....

Our TV is on at the moment and, using a plugin monitor, the following spot values apply ....

Mains voltage - 247.7
Amps - 0.91
Power factor - 0.85
Watts (Real) - 190

... when the picture changes brightness all values change. If it's darker, the power required drops, but the power factor changes to ~0.5, but looking at the above the calculation the apparent power would be 225W (247.7*0.91), whilst the billing meter will be (/should be) measuring the power factor and correcting the billable power to 191W (225*0.85) ... with the odd 1W being tolerance and rounding related.

Most (/all ?) clamp based energy monitors, such as the OWL, simply measure the Amps passing through the sensor, they have no idea of the actual voltage and direction of energy flow. Voltage is normally parameter dependant on these items, therefore, if the unit is set to 230V it would be registering 209W(230*0.91), therefore an error of +9.4%(209/191) ... however, on a 3kW kettle, which would have a power factor of ~1.0, the apparent power and real power would be the same and the same clamp based monitor would be registering an error of -7.1%(230/247.7) ... the overall accuracy of energy monitors such as OWL therefore not only depend on their own accuracy and the parameters, but also on the mix of devices and usage within each household.

Within commercial operations there is the likelihood that processes which have a very high capacitive load exist, therefore, as the grid needs to be able to cope with the maximum (apparent) load at any point in time, commercial sites are billed taking power factors into account which in turn creates an incentive to smooth out the effect of capacitive loads on the demand side of the billing meters. This reduces both the cost of energy to the organisation and the need for excess generating capacity along with better load balancing in the grid which in turn lowers supply-side costs.


Considering the above regarding power optimisation, lets now look at pure voltage optimisation (/adjustment) ....

Assuming a theoretical optimisation unit in my property at the moment which would ensure that the delivered voltage was maintained at 230V and is 100% efficient at doing so (which it isn't) ...

(i) - My TV's electronic circuit would still need to draw 190W (real) from the mains in order to operate, the power factor would still be 0.85, therefore with the voltage being 230 it would need to draw a maximum 0.97A(190/0.85/230) .... therefore no energy advantage derived from voltage optimisation.

(ii) - A fully resistive item such as a kettle operates on a much more basic basis. Assuming a typical 3kW element to be ~20 Ohms and applying Ohm's law (V=IxR), at the optimised voltage the current would be 11.5A (230/20), therefore 2645W(230*11.5) and at mains voltage 12.4A (247.7/20), therefore 3071W (247.7*12.4). As can be deduced, the lower voltage delivers less power, however, relating this to any thermostatic device such as a kettle means that the time to achieve the same result, ie a boiled kettle, takes 13.9% ((2645/3071)-1) longer, but importantly, uses the same amount of energy (actually slightly more considering additional operating heatloss) ... therefore no energy advantage derived from voltage optimisation.

... As can be gathered from the above, when applied to the majority of household electrical devices which follow the same rules, there is absolutely no major cost advantage to be gained from voltage optimisation, so what would the items be which would create savings .... well quite simply, it's resistive load items without a required (eq thermostatically switched) duty ... that, in most households simply leaves resistive lightbulbs, however, with the drawback being the provision of less light, this could more easily be achieved using lower wattage bulbs ....

I can't see any advantage in using these devices which would justify their costs in our pretty typical domestic situation.

HTH
Z

[Deleted User]

zeupater wrote: »

Hi

In a domestic situation it's, let's say, somewhere between unusual & impossible ....

There is much confusion between power factor optimisation and voltage optimisation, so let's take a quick look at both within a domestic scenario ....

In the UK, for domestic supply, we are metered & billed in terms of energy supplied (real power) with the power factor therefore being irrelevant.

Electrical devices within your property will mostly fall into one of two groups - restive or capacitive - something like an electric kettle, panel heater, filament lightbulbs or toaster will be fully resistive, a fan assisted oven or fan heater mostly resistive with most electronics equipment, such as TVs, timer circuits, radios etc being capacitive ....

Our TV is on at the moment and, using a plugin monitor, the following spot values apply ....

Mains voltage - 247.7
Amps - 0.91
Power factor - 0.85
Watts (Real) - 190

... when the picture changes brightness all values change. If it's darker, the power required drops, but the power factor changes to ~0.5, but looking at the above the calculation the apparent power would be 225W (247.7*0.91), whilst the billing meter will be (/should be) measuring the power factor and correcting the billable power to 191W (225*0.85) ... with the odd 1W being tolerance and rounding related.

Most (/all ?) clamp based energy monitors, such as the OWL, simply measure the Amps passing through the sensor, they have no idea of the actual voltage and direction of energy flow. Voltage is normally parameter dependant on these items, therefore, if the unit is set to 230V it would be registering 209W(230*0.91), therefore an error of +9.4%(209/191) ... however, on a 3kW kettle, which would have a power factor of ~1.0, the apparent power and real power would be the same and the same clamp based monitor would be registering an error of -7.1%(230/247.7) ... the overall accuracy of energy monitors such as OWL therefore not only depend on their own accuracy and the parameters, but also on the mix of devices and usage within each household.

Within commercial operations there is the likelihood that processes which have a very high capacitive load exist, therefore, as the grid needs to be able to cope with the maximum (apparent) load at any point in time, commercial sites are billed taking power factors into account which in turn creates an incentive to smooth out the effect of capacitive loads on the demand side of the billing meters. This reduces both the cost of energy to the organisation and the need for excess generating capacity along with better load balancing in the grid which in turn lowers supply-side costs.


Considering the above regarding power optimisation, lets now look at pure voltage optimisation (/adjustment) ....

Assuming a theoretical optimisation unit in my property at the moment which would ensure that the delivered voltage was maintained at 230V and is 100% efficient at doing so (which it isn't) ...

(i) - My TV's electronic circuit would still need to draw 190W (real) from the mains in order to operate, the power factor would still be 0.85, therefore with the voltage being 230 it would need to draw a maximum 0.97A(190/0.85/230) .... therefore no energy advantage derived from voltage optimisation.

(ii) - A fully resistive item such as a kettle operates on a much more basic basis. Assuming a typical 3kW element to be ~20 Ohms and applying Ohm's law (V=IxR), at the optimised voltage the current would be 11.5A (230/20), therefore 2645W(230*11.5) and at mains voltage 12.4A (247.7/20), therefore 3071W (247.7*12.4). As can be deduced, the lower voltage delivers less power, however, relating this to any thermostatic device such as a kettle means that the time to achieve the same result, ie a boiled kettle, takes 13.9% ((2645/3071)-1) longer, but importantly, uses the same amount of energy (actually slightly more considering additional operating heatloss) ... therefore no energy advantage derived from voltage optimisation.

... As can be gathered from the above, when applied to the majority of household electrical devices which follow the same rules, there is absolutely no major cost advantage to be gained from voltage optimisation, so what would the items be which would create savings .... well quite simply, it's resistive load items without a required (eq thermostatically switched) duty ... that, in most households simply leaves resistive lightbulbs, however, with the drawback being the provision of less light, this could more easily be achieved using lower wattage bulbs ....

I can't see any advantage in using these devices which would justify their costs in our pretty typical domestic situation.

HTH
Z

Thanks for the thorough explanation even if most of went over my head

OffGridLiving

Some of these companies are now tying their products to PV installations. Again, is this all just smoke and mirrors too, or is there a valid benefit from them with PV?