PV+ - anybody heard of this?

SibertSolar · Apr 9, 2016

Ok, thanks, and is the unit manipulating the voltage/supply that the inverter senses and synchronises with? Also, how is the PV+ unit different from a VO unit?

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marc8 · Apr 9, 2016

PV+ not sure if it will be cost effective

Gavin A · Apr 11, 2016

matthunt said:
Yes the PV + is connected between the grid and the inverter, but not between the meter and the inverter

to be clear, is the inverter backfeeding through the VO transformer?

IT looks like it may not be, and is simply taking the place of a henley block / distro board to make for a neater installation, with the VO unit only operating on the supply (from combined solar and grid) to the house consumer unit rather than the actual PV circuit itself.

Hopefully that's the case otherwise it would invalidate the G83 or G59 protection settings on the inverter which are designed to protect the local grid from over voltage caused (at least in part) by the PV generation.

matthunt · Apr 11, 2016

Gentlemen, the best way to look at the product is like a G59 relay, if the grid reaches statutory limits then the device will switch the inverter out of circuit but on the grid side and not the inverter side.

Gavin A · Apr 12, 2016

matthunt said:
Gentlemen, the best way to look at the product is like a G59 relay, if the grid reaches statutory limits then the device will switch the inverter out of circuit but on the grid side and not the inverter side.

have you got G83 type test approval for that? There's no mention of it on your website.

Also can you explain what the point is in doing that rather than simply feeding the inverter in on the grid side of the VO unit? I suppose you save the transformer losses for self consumption, but then the voltage at the house side will be higher than if the PV was connected to the other side due to the resistance in the transformer (when the house is exporting).

The manual and wiring diagram don't really make it look like it works in that way.

To satisfy my curiosity would you mind just confirming directly that the PV is backfeeding through the VO unit to export to the grid?

If you actually have managed to produce a decent unit that serves a proper purpose and integrates well with PV without invalidating the G83 type test approvals, then it could be worth us having a look at. I gave up on Vo a few years ago due to the level of unsupported rubbish being spouted about it, and rubbish build quality and support from the units we tried.

GreenE4u · Mar 1, 2017

Hello Gentlemen, This is my first time on this forum so apologies if I over step the mark. As Matthunt pointed out " look at the product is like a G59 relay, if the grid reaches statutory limits then the device will switch the inverter out of circuit" The important words are "if the grid reaches statutory limits."

Given that the Solar panel system has to comply with the strict requirements of the grid, how can such a relay improve the performance of the solar panel system? Where does the 25% increase in performance all these companies selling the device come from? Is there any hard facts?

Having had a 4kW system in operation for 7yrs and taken readings of the performance of the panels and system over the period, I fail to see the benefits of adding such a device. As such I think it is a waist of money.

Bruce076 · Mar 16, 2017

I have heard of this (unfortunately).

I discovered some unscrupulous salesman had sold one of these DC PV+ units to my elderly mother, ripping her off to the tune of £2,500. After 6 months her FiT readings were slightly lower than the same period the previous year. I simply put this down to the panels maybe needing a clean. Before installation she was told by the salesman her FiT readings would double!

I'm personally seeing that the firm involved is reported to Trading Standards for this disgusting example of gross miss-selling.

My advice would be avoid at all cost in a domestic situation.

Rob Latta · Mar 23, 2017

I saw one of these last week from a family member. £3000 if the offer was taken up now, because they were in the area doing other installs and VAT is currently cheaper. £4000 if taken up later because VAT will go up after April to 20% on solar things

This was their sales pitch

Our inverter is close to end of warranty (5 years). All the time it's being subjected to spikes in voltage which cause stress and it has to give off those spikes as wasted heat.
They will install a "power saver" which will reduce or eliminate the spikes, thus protecting the inverter from all that stress that's lowering it's life expectancy
Something about our voltage being over 250V but the power saver will also cause our voltage to drop to 220V which will save money on appliances
They will provide a 10 year guarantee for it and for our existing inverter. Replacement would be with a high quality inverter. I asked what the current cost of such an inverter would be today and they said £2500
The power saver will make more electricity go back into the grid and increase the revenue from the feed in tarriff by 40% (£300 per year)
It will make more electricity available for our appliances and decrease our electricity use by 30% (£200 per year)

After listening to the pitch my family member tried to buy it. If I hadn't suggested we get the advice of a relative in the energy business they would have bought it.

Some web research leads me to conclude they were selling what's known as PV+ which is approximately £700-£1000 fully installed (although that would be without the inverter warranty extension mentioned above) according to random websites I see selling it and a posting on the Money Saving experts forums (I tried to link them but it wouldn't allow me to)

Clodbuster · Mar 23, 2017

Rob Latta,
I had a very similar sales pitch yesterday and, blow me down, I could get a discount as they had installers in the area.

I listened to the salesman who tells me that all panel arrays have a protection so if one panel goes over the rating for that panel (in my case 240w) then the inverter shuts down THE WHOLE array for 15 minutes so I lose all generation for that period. This may happen 4 - 5 times per day. This “PV Plus” irons these spikes out preventing the inverter shutting down so you record greater generation. He said between a minimum of 25% to a possible 40% depending on season etc.

Cost is £4000, at my current generation and return about 7.5 years to recoup.

Anyone able to corroborate that the panels are shut down so frequently?

LeeH · Mar 23, 2017

Sounds like snake oil to me.

Never seen mine shut down, you can see the generation on a graph online.

Chr!s · Mar 23, 2017

oldsalty said:
Hi,

I am being touted by my local installer to add a module called PV+ to my residential solar array. This module is claimed to effectively improve efficiency of my installation by 20% (thereby increasing my FiT earnings) by balancing out and reducing overvolting, which they tell me cuts out generation for every period of overvolting. Forgive my brief description but that is as I understand what it is supposed to do!

The module costs GBP859.00 (fully installed) so is something worth finding out about before going for it.

Is there anybody who knows this equipment and can comment on the efficacy of the claims. Many thanks.

Hi, ask him to show you his calculations to back up his 20% claim, if your unit is not suffering from over voltage, where is the 20% savings coming from?

whinmoor · Mar 23, 2017

Complete twaddle. Best avoided.

Gavin A · Mar 23, 2017

Clodbuster said:
Rob Latta,
I had a very similar sales pitch yesterday and, blow me down, I could get a discount as they had installers in the area.

I listened to the salesman who tells me that all panel arrays have a protection so if one panel goes over the rating for that panel (in my case 240w) then the inverter shuts down THE WHOLE array for 15 minutes so I lose all generation for that period. This may happen 4 - 5 times per day. This “PV Plus” irons these spikes out preventing the inverter shutting down so you record greater generation. He said between a minimum of 25% to a possible 40% depending on season etc.

Cost is £4000, at my current generation and return about 7.5 years to recoup.

Anyone able to corroborate that the panels are shut down so frequently?

please report them to trading standards & RECC if they are members, this is a scam based on complete lies, and by reporting the company you may save many others from being ripped off. Thanks.

Gavin A · Mar 23, 2017

Bruce076 said:
I have heard of this (unfortunately).

I discovered some unscrupulous salesman had sold one of these DC PV+ units to my elderly mother, ripping her off to the tune of £2,500. After 6 months her FiT readings were slightly lower than the same period the previous year. I simply put this down to the panels maybe needing a clean. Before installation she was told by the salesman her FiT readings would double!

I'm personally seeing that the firm involved is reported to Trading Standards for this disgusting example of gross miss-selling.

My advice would be avoid at all cost in a domestic situation.

sue them as well please. Small claims court should be an open and shut case.

LeeH · Mar 24, 2017

matthunt said:
Gentlemen, the best way to look at the product is like a G59 relay, if the grid reaches statutory limits then the device will switch the inverter out of circuit but on the grid side and not the inverter side.

It's gone quiet..

Clodbuster · Mar 24, 2017

This is the unit offered to me.
PV Plus | The Renewable Energy Hub - https://www.renewableenergyhub.co.uk/blog/pv-plus-unit/

Clodbuster · Mar 27, 2017

I had a reply from the manufacturer of my inverter and I copy their reply in.

“Thank you for contacting us, Inverters are designed to only convert the maximum DC input that the inverter is capable of, it does not read the generation of individual panels. The over voltage issue the PV Plus refers to only occurs in a very small number of systems usually farms and areas that are remote where the supply voltages can be less stable.

The voltage of the PV panels which is DC does not increase with the exposure to more sun, with a small amount of daylight the DC voltage of a PV module is almost at maximum so stays stable throughout the day, it’s the current which is directly affected by irradiance levels, so overvoltage of the PV system is not possible if the system is designed correctly and inverter will not turn off.”

So that solves the question.

whinmoor · Mar 27, 2017

This link explains how the output of solar panels can decrease as temperatures rise (and voltages reduce):

http://www.solar-facts-and-advice.com/solar-panel-temperature.html

Rob Latta · Mar 29, 2017

Whilst looking into this I did see an in-situ 1 year long experiment with two systems side by side on an industrial estate (one side of a roof with a PV+ system and the other side without). It shows a graph for 1 day with lots of up/down curves for the non PV+ system as it shut down when voltage was too high (compliance with regulations I think?) whereas the PV+ system shows a constant horizontal line because it didn't have to shut down, due to the PV+. The report is in PDF format and is at the light blue link that says "pv-final-data" at this page PV+ Grid Voltage Monitor Unit - http://matt-e.co.uk/are-you-getting-the-most-out-of-your-pv-system/ and is also available from this direct PDF link http://matt-e.co.uk/wp-content/uploads/2016/02/pv-final-data-V2.pdf

The results are quoted below. I kind of like it because I'm a sucker for something written up like a school science experiment but I don't really have the knowledge or experience to critique its validity

Results
The systems were commissioned on 24th June 2015 and have been left to run without interruption until the 24th of June 2016.
Final meter readings taken:

System 1 Non PV+ 1558.66kWh

System 2 PV+ 1744.97kWh

As shown in the table below both systems easily out performed the expected generation. However the PV+ unit achieved an additional 186.31kWh or 11.95% compared to the system without the PV+ unit fitted. <see the PDF for the table>

Conclusion
While the additional 11.95% increase is significant in monetary terms, especially for the early adopters on higher FiT rates, It should be noted that the test was carried out on an industrial estate where heavy loads on the local grid significantly lower the voltage during the working week. Thus reducing the need for and the benefits of installing the PV+. This theory is supported as most of the increase in generation was gained during early evening after local factories had stopped production but mainly during weekends when they are closed. It would be fair to assume grid voltages in residential areas would be more consistent during the day, therefore in areas of higher grid voltage, inverter off times would be more frequent meaning further loss on generation

Clodbuster · Mar 30, 2017

I see the trial was run by the supplier - those always make me take them with a pinch of salt.

Do I read it right - the inverters shut down because the mains voltage is above 244v - nothing to do with the panel generation?

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