How Do Solar Power Diverters Work?

UPDATE: The Feed-In Tariff is now closed for new applications. To find out about the new scheme designed to replace it, click here.

We get a fair few comments regarding solar power diverters here at TheGreenAge. These clever little gadgets prevent electricity produced from your solar panels from being exported back to the grid by diverting the electricity to the immersion instead.

Why send excess electricity to your immersion?

The reason for doing this is that under the Feed-in tariff, very few people have an export meter fitted as part of their solar installation – instead the Government assume you are exporting 50% of what is generated and pay you this accordingly. Therefore if you can use all the electricity that you produce in your home instead of exporting it then not only do you still benefit from the maximum feed-in tariff payments available you also benefit from the maximum energy savings.

On the whole these solar power diverters (also known as solar PV optimisers) divert the electricity to the immersion. They monitor the electricity being consumed in the home and the electricity being produced by the solar panels – as soon as there is a surplus being produced they divert this to the immersion unit – without the power diverter in place, this electricity would normally be exported back to the grid – this is where the most common question we get arises.

A common misconception regarding solar power diverters

If the Solar power diverter kicks in at 70 watts surplus PV output, this would not be enough to power the immersion heater, these heaters are rated at 3kW, so would consume at least 3000 watts therefore the extra 2930 watts will be dragged from the grid and electricity bills would be very large.

Excess grid power should be fed to the grid until sufficient power is available to operate the appliances, 70 watts will not do it.

Well obviously if this was the case it would rather limit the effectiveness of a solar power diverter! Pulling in the shortfall of electricity from the grid would in fact cost you a huge amount of money. Fortunately on the whole they don’t work like that. We spoke to Bob Morris, founder of the Apollo Gem Solar power diverter system and he said the following:

The truth about solar power diverters!

A TV and most other appliances that require an electronic power supply can only operate using full mains voltage and the power for which they are rated. If you were to restrict the power flowing into such appliances they will not operate – put simply the TV would not be on!

On the other hand a heating appliance such as an immersion heater is a pure resistive load and will work at any power regardless of the rated power. In other words a 3KW immersion element will work quite happily if you were to restrict the power flowing into to say 1.5KW but it would only produce half of its rated heat energy.

Our Apollo GEM system electronically regulates the power flowing to such heating devices according to the export power available, just like you can restrict water flow by partially opening a tap.

If the available export power is (say) 70W then the gem will restrict the power flowing into the immersion to 70W even if the full power rating of the element might be 3000W. This ensures that no grid power is imported to run the immersion.

A system that simply waited until 3KW of export power was available and then turned on the immersion fully would be very inefficient and only be able to save a few percent of the power exported.

So there you have it! A solar power diverter monitors both electricity being consumed by the house and electricity being produced by the solar system and will only divert when there is a surplus of electricity being produced – so hopefully that puts to bed a common misconception of how these clever little units work!

Think we missed something? Do you have a different opinion?

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