Solar PV+ Optimiser

Dr_Watson

I've been offered the installation of a PV+ Optimiser for my own owned Solar PV system. The company claim that I will see an increase in 20% of the Feed In Tariff payments I receive, along with further reductions in my electricity bill.
Questions I have are:-
Does anybody have any experience of having these fitted to their system?

Are the increases in FIT payments actually achieved?

How does altering or modifying your own system affect you when signing your monthly declaration to your FIT supplier to state that you haven't altered it, or have, as would be the case?

What are the reasonable costs of fitting such a device?

Are the units actually MCS accredited? The installer reckons they are but i've not seen anything to confirm this.

Any experience or help will be welcome!

Cardew

The widely advertised 'Voltage Optimisers' merely lower the mains voltage which, as Ohms Law still applies, achieves next to nothing in a domestic application.

I suggest you post in the Green and Ethical section of the MSE forum where these devices have no doubt been widely discussed..

System

Spot on Cardew. This link might save the OP some time. The writer appears to know what he is talking about:

http://www.yougen.co.uk/blog-entry/1948/Is+domestic+voltage+optimisation+all+it'27s+cracked+up+to+be'3F/

ChumpusRex

These devices can possibly increase your PV output, if the grid in your area is too weak to accept the power from your PV system.

Mains voltage in the UK is "officially" 230 V (actually, there is a legally allowed range of between 208 V and 253 V). In practice, the mains voltage is usually in the region of around 240 -245 V.

When you use a lot of power, the voltage at your house goes down (because electricity flows "downhill" from high voltage to low voltage). When your PV panels are generating, they need to push electricity back into the grid, which causes the voltage at your house to rise.

If your solar system finds that the voltage goes up above the legal limit of 253 Volts then it will shut down automatically. Because the voltage goes up the most when you are generating most power, this voltage cutoff can result in your system shutting down at the exact time that it is most productive.

Because of this, some solar systems can be configured so that they don't shut down until about 262 V. However, this high voltage can cause problems to your other appliances which may be overloaded by it.

To know whether a voltage optimiser would be useful, you need to know if your solar system is shutting down due to high voltage. If it isn't, then an optimiser (which just lowers the grid voltage) will do nothing.

Even if your solar system is shutting down from high voltage, it may be possible to increase the shutdown voltage; or you could ask your local electricity distributor to lower your grid voltage.

If you can't adjust the shutdown point on your PV, and your electricity distributor (not supplier) won't reduce your grid voltage (or can't reduce it any further), then an optimiser may help.

Dr_Watson

Thanks for the help everyone, I'll be leaving my 'working fine as it is' solar PV installation alone.

Martyn1981

Dr_Watson wrote: »

I've been offered the installation of a PV+ Optimiser for my own owned Solar PV system. The company claim that I will see an increase in 20% of the Feed In Tariff payments I receive, along with further reductions in my electricity bill.
Questions I have are:-
Does anybody have any experience of having these fitted to their system?

Are the increases in FIT payments actually achieved?

There's a chance that they were trying to sell you an upgrade to your system, by changing it to a SolarEdge system with power optimisers.

These phonecalls (I've had a few, and even allowed one to visit) generally talk about a 20% to 25% increase in generation.

If you have a heavily shaded system, then a SolarEdge setup can help a lot, and probably give you a 20% improvement. My smaller WNW system is heavily shaded and is a SolarEdge set up. It outperforms my ESE systems, after taking size and orientation into account.

If you don't have any (much) shading then the SE kit will only give you a small increase in performance, perhaps 5%. But a retrospective upgrade will cost £'000's.

The quote for upgrading my ESE systems, was ~£4.5k. Roughly the cost of installing a new PV system, with SE kit today. I'd estimate increased income (due to some minor shading and relatively inefficient inverters) at ~£140pa. Alternatively, replacing the two poorish inverters, with a single more efficient model, as and when one fails, would probably give me half the increase, for around £800, money that will have to be spent eventually, anyway.

Mart.

ChumpusRex

Martyn1981 wrote: »

There's a chance that they were trying to sell you an upgrade to your system, by changing it to a SolarEdge system with power optimisers.

These phonecalls (I've had a few, and even allowed one to visit) generally talk about a 20% to 25% increase in generation.

Good point. However, in this case, there is a specific device called a "PV+ optimiser" for which the marketing claims a 20% increase in FIT.

This specific device is just a mains voltage reducer, which shields the PV system from high grid voltage so that it doesn't cut out.

Martyn1981

ChumpusRex wrote: »

Good point. However, in this case, there is a specific device called a "PV+ optimiser" for which the marketing claims a 20% increase in FIT.

This specific device is just a mains voltage reducer, which shields the PV system from high grid voltage so that it doesn't cut out.

Hi Rex, good to know, many thanks.

Of course, if you are suffering overvoltage from the grid during 20% (or so) of generation time, then really it's up to the DNO to solve the problem, since they are required to keep voltage between 216V and 253V, even where SSEGs (small scale electricity generators) exist.

My SE inverter has shutdown once, in 4 years, due to overvoltage. It was easy to diagnose as my older ESE SMA inverters were still running and reporting grid voltage at 256V.

Only happened the once, and was on a Sunday afternoon, when demand is classically low, and spikes can occur.

It came back on later when the voltage had dropped back down. Typically voltage here is around 240-244V. Never close to our 'pretend' UK 230V nominal.

Mart.