I have PV panels - 14 of them, styled “8.33 285w ETERNITY+10 PV modules”.  They are made by Table Trading S.L. aka 8.33 Solar. 

6 East facing and 8 West facing for the afternoon sun, using a Clenergy mounting kit. 3.99 kW nominal they rarely reach 3 at any time.  We’re in Durham in the North East of England, so not ideal for lots of sunshine in comparison to the South of the country.  Our best day this year was 1 June at 25.6 kWh; our highest peak generation was 2 Jun at 2.87 kW.

The inverter is by SolarEdge and comes with a website and an app to monitor the output.

Installed October 2015 at a cost of £5995 by a local company called WeRSolarUK (which nearly put me off). Installation was straightforward, all done in a day.  The company isn’t operating and their web site isn’t there, but hasn’t been struck off or shut down according to companies house. 

When installed I couldn't justify the battery option and at the time we didn't have an immersion heater because British Gas who replaced our boiler and upgraded the system said they were obsolete and that their fully insulated cylinders did not have them. Drat.

The installation included an EPC, rating our house as B 83.

The predicted performance was 2640 Kwh (sic) pa.  Actual is 15140 kWh over 5 years, so 3028 pa. 

I’m on the FIT scheme, starting at 12.47p for generation and 4.85p for export.  When installed we had dumb meters, but in 2017 got smart meters so the export was more accurate. Regrettably I still have to submit the readings to OVO manually.  Since installation, export is almost exactly half generation. Some days our electricity use is negligible during the day.

They keep remarkably clean - I’ve twice washed them with a long handled brush attached to the garden hose. They are tight enough to the roof that we don’t get birds underneath.  A roofer we used recently commented on that as he’s previously come across birds nesting under panels, even a pigeon!

So far saved electricity over 5 full years has been worth £999, based on units used compared to pre-solar. FIT payments have been £2545, so between those it has paid off more than half already. The estimate at the time of installation was an 11 year payback, but at this rate it will be 8 years.

My experience has been positive so far.  I wish we could have more which would then make more sense of a battery. Last time I looked was when we had a power cut, and our panels stopped providing power to us. I was astounded to find that most batteries also just stop working in such a situation.

At some stage I will get round to connecting it up to the immersion heater I had retrofitted when I eventually found a plumber who could do it - but I need to find a different installer.

We don’t yet have an EV but that could be a battery alternative.

There are remarkably few solar installations around us, but also an amazing number of east/west roofs, even on new builds.  One development about a mile away has solar panels as part of the roof tiling. The new development near us does not have them as standard.  @Transparent probably understands that better than me in terms of the need for balance in the network.

It was certainly a great investment.

Although the FIT is interesting from a historical perspective, i would personally be interested in more recent examples in terms of current tech/suppliers/costs/ROI that have made use of the Smart Export Guarantee (4p from OVO for example). There may not be many of these examples. 

So as an alternative look at the examples that made use of the FIT and see what difference the payback would be with a Smart Export Guarantee of 4p.

I have a 4kW domestic solar PV installation since 2016.· The array is 12 x 330w Panasonic HIT N Hybrid Modules. The estimated savings was (forecasted to be) about £450 per year with an estimated ROI over 11+ years so yet to recover the investment. We chose Panasonic as it came with 25 Year Performance & 15 Year Product Warranty. The installer was first4solar who were responsive and professional till the point of invoice settlement. Unlike many suppliers, they remain an ongoing concern. The smart WiFi monitoring system failed within two years so I can’t share the graphics as above except the dumb meter.

Since 2020 I have V2G and SMETS1 which reduced my FIT so I hope the export credits compensate for the reduced microgeneration.

As of now, generated 18kWH of electricity so roughly £2600 of savings achieved in the last 7 years. 

And we’re off, and what a start to this thread. Thanks for all these contributions!

I’m a novice when it comes to PV panels. I’m not ashamed to admit it, and actually that puts me in a good place to ask questions that others might ask. 

So in your case, @EverythingNeedsAUserName, it was the inverter manufacturer who provided the web/app interface to monitor generation, rather then the installer. @sylm_2000 calls out having a similar monitoring system but this failing after two years. Was this provided by the actual manufacturers/installers? Is there not a third party provider of this that’s available? Wouldn’t there always be a risk of the interface and software eventually failing if it’s reliant on the company surviving and maintaining this tool? Solar panels can last decades, but not all companies do…..

So far saved electricity over 5 full years has been worth £999, based on units used compared to pre-solar. FIT payments have been £2545, so between those it has paid off more than half already. The estimate at the time of installation was an 11 year payback, but at this rate it will be 8 years.

 

 

This is a fantastic visualization of reduced imported electricity from the grid. It’s important to call out here that energy is still being used. It looks like a fridge/freezer and standby devices cause a content low level or usage over night. Well those will carry on using energy, but it’s taken straight from the energy generated from the PV panels and not from the grid via the meters.

A very good ROI as well, but @Jeffus can you outline why someone getting panels now, and using the smart export guarantee might not see the same benefits? Is it simply a case of less £ per kWh?

Can you help us to understand the forces at play here? You have an electric vehicle (EV), which acts as a storage battery when plugged in and when the sun is shining. When you had a smart meter fitted, this meant your export could be measured exactly, rather then assumed to be 50% of generation. That’s why the FIT payments were reduced, am I right? So when you refer to export credits, that’s the payments from OVO for the energy you’ve exported from the car battery to the grid via your V2G charger. Have I got that right, @sylm_2000?

The Energy Savings Trust’s Solar Energy Calculator suggests that if I were to install now on the current scheme, over a 25 year lifetime, a 4kWp system facing West here would generate 2,770 kWh / year and actually COST me £203.  That would put most people off.

As we have on average generated 3,000 kWh / year, that calculation is understating the case a little, but it would only halve the cost to around £100.

So if as their calculator suggests, the installation is still up at £5,419, there isn’t a FINANCIAL incentive to install them.  Not enough sunshine in the North East ;)

@Tim_OVO  The inverter manufacturer provides the web/app interface to monitor generation and state that it will be there for the lifetime of the installation without ongoing cost. 

Solaredge claim to be The World’s #1 Home Solar Energy System.  The app has been updated several times since 2015, as has the web site. The company seems forward thinking and active in homes and businesses round the world.

When it was first set up by the installer, we could see ALL of the installations done by our installer as everyone had the same login.  After a year that was decided to be against privacy rules and practice, so we were each allocated our own site.  Frustratingly, the installer didn’t set it up showing which panel was where, because the lads hadn’t recorded it, so I just have one big string of panels.

@Tim_OVO you’re spot on except a small caveat SMETS1 can work or against depending on your consumption profile. Again I might be overplaying here, it is not much of a difference.

My concern remains the longevity of the solar panels which is indirectly proportional to the installers/companies survive in the business. The ROI or risk to reward is disproportionate especially with the FIT now gone. 

The software and monitoring system is my second bugbear. There is no standard platform to collect, share and  analyse data. I think this could be a great opportunity for Kaluza like apps to integrate microgeneration with grid load balancing. 

Thanks for confirming, both!

A potentially stupid question here, but should maintenance be needed on your set up, and the original installers were no longer in business, I’m assuming another installer would be capable and qualified to do the work?

Yes I agree and as a novice I’m surprised to hear there isn’t a software offering this. Similar to the third party Bright app which uses usage data from the DCC to display smart meter usage. A universal platform for PV panel households to use, no matter what happens to the manufacturer / installer would surely offer utility and peace of mind, considering the average life span of a panel array.  

For Kaluza’s Flex platform, I suspect this future monitoring would happen at the smart meter export level…?

First a response to that last comment from @Tim_OVO 

The Smart Meter will only provide data averaged over a half-hour. Those with solar panels require data at intervals of around 1-3mins (20 to 60 per hour), and it needs to show ‘peakiness’ too. Averages aren’t very useful if you’re busy trying to maximise efficiency!

There are standard/generic methods for analysing electrical parameters, the most established one being Modbus, invented by Modicon in 1979!

You basically buy one or more Modbus energy meters, connect these with a 2-wire bus-network to a Modbus-TCP unit which sends the data wherever you want it via ethernet and/or internet.

I’m exploring Modbus generally at the moment because many people would probably be interested in making graphs of energy usage as we increasingly try to combat Global Warming.

Can I ask that we leave this Monitoring subject alone here, rather than get distracted from solar panels. If anyone knows more about Modbus networks and the SCADA software used to handle the commands and data, then please send me a PM

Energy monitoring needs to be a separate topic on its own.

lPostScript: Energy Monitoring now does have its own topic!]

Maintenance - I hope so! SolarEdge still have lots of links to approved installers, so although my installer has gone, I hope it wouldn’t be difficult.  There is at least one nearby that will do a service for £75, and specifically state “We will service your system, even if we didn’t install it”.

Upgrades? As 6 years has passed since installation, and with EV and battery tech improving, there are installers keen on integrating new controllers and systems, and adding battery and water heating. 

Monitoring

• the SolarEdge monitoring web site gives me 5-minute data, which I can export as csv day by day, even back to the very first day that the system went live on . The app only gives the data every 15 minutes as I refresh.  
• the IHD from OVO gives 5-second updates to usage, at present on an overcast day -857W compared to the SolarEdge monitoring generation of 1.02kW. So the frequent data would seem to be in the system, if not recorded for posterity. (BTW, my OVO account usage on the web site has no daily data since 6th August! Prior to that it is half-hourly.)

I’m wondering if solar panels will be worth the outlay.

@EverythingNeedsAUserName ‘s graphs are very revealing! @Transparent what are you doing with all the electricity your panels are generating?

I can’t use all the electricity produced in the summer months: I could charged the car up and get a diverter to heat the hot water, then get 4p a unit selling the surplus back to the grid, which isn’t very tempting.

In winter the output is so much less, or nothing at all later in the day when I need it for my heat pump.

Battery storage may help, but should I not bother with PV, just get biggest the battery I can afford and charge it at the lowest tariff available?

By a funny coincidence @juliamc there’s a new thread this week about this very question. The poster can’t install solar panels due to the property being listed, so is considering storage and off peak usage replacing oil fired heating:

 But that still leaves you vulnerable to wholesale electricity costs…. 

@juliamcwrote:

what are you doing with all the electricity your panels are generating?

Good question.

1: I don’t get any Smart Export Guarantee payments (yet).

Because I moved from off-grid solar to grid-connected generation at the start of the OVO PowerVault Storage Battery trial in January (2021), the paperwork had to be processed by an approved SEG Agent. OVO is such an agency, but they rejected the initial documents from my DNO because those showed that a formal certificate was not necessary.

OVO and PowerVault then changed the grid-connection arrangement such that a G-99 certificate is required. However, six months has passed and there’s still no sign of the problem being resolved.

This issue needs highlighting here for any others contemplating grid-connected PV Solar Panels. You are completely dependent on the installers adequately providing documentation. Once equipment is fitted and any invoices paid, you lose all leverage to get this sorted.

SEG payments cannot be back-dated. So the export from my Solar Panels during summer ‘21 has been available for OVO to sell on the wholesale market, but at my expense (around £30 of lost SEG).

That’s why @Tim_OVO and @Jess_OVO can afford to buy a slab of lard to go with their loaf of bread ‘pay’ at the end of each week.

2: My PV Solar Panels are connected to the PowerVault Battery using an AC-input configuration.

Let’s calculate this using generous efficiencies of 94% for AC-to-DC (charge) and 90% for DC-to-AC (discharge) cycles.

For each 1kWh generated by the PV Panels, 1x0.9x0.94 = 846w ends up in the battery.

To retrieve that back into the home I get 846x0.9 = 760w

Using this configuration, my three rooftop arrays rated at  5.1kW actually yield just 3.88kW from a period of full sunshine.

That’s appallingly bad, and no one would seriously consider such an arrangement if they were aware of the figures.

3: The Storage Battery itself has running costs, mainly for the fans which cool it. My measurements show this is approx 500kWh per year. That equates to around £20 of ‘lost’ SEG payments… which I don’t receive anyway!

4: What solar generation I do actually capture goes towards running:

• my two separate water purification units (we have a well)
• the whole house Mechanical Ventilation and Heat-recovery unit
• the (off-grid) broadband VDSL router and network hubs
• a fair proportion of the house lighting (24v LED units)
• the chickens!

Hi All,

Sent here by Jess_OVO from the Smart Meter forum who were all extremely helpful with a problem I was having with my smart meter installation that my energy supplier Together Energy seemed unable or unwilling to help with. I have the following equipment fitted for the last 4 years with the FIT paid by British Gas at Feed in Tariff 4.68 p/kWh and Export at 5.50p/kWh giving about £315 last year other years not analysed as I always had better things to do. The system 26 JA Solar 270W Black JAM6(K)(BK)-60-270-4BB fitted on a south facing roof, a Samil Solar River 6000TL inverter and a Ladis & Gyr - 5235B meter The estimated system performance was 6199kWh/year. All very detailed but not that interesting. Since then I have had a Tesla 13.64 k battery fitted about 3 months ago and I have fitted  my Energi Eddi and Zappi for hot water production and Car charging from surplus PV energy. My car is a fully electric Kia Niro plus 64 kWh battery, I charge whenever I remember and I have surplus energy and so far approx 2000 miles have only once paid or a charge. On the whole I am delighted with the system performance especial the reduction in grid demand the Tesla has produced. Don’t ask for exact figures, let it suffice to say since the Tesla was fitted in late May I have only used 15 kWhs, so at my present rate not considering the standing charge that’s about £1.80 of electricity, approximately 2 summer months for a couple of quid. I recently removed an Ariterm Biomatic 40i pellet burning boiler as it proved over the 4 years it was fitted, to be dirty, demanding of lots of maintenance and completely unreliable. I consider having it fitted as the worst decision  have ever made and the Tesla as my best. The final straw came when the Ariterm Portal website was taken down, without notice making analysis of the frequent trips impossible. I contacted Bio Nordic the UK agents ,who’s only employee as far as I can see lives in Sweden and in line with the support I had received over 4 years still await a reply. If your reading this James Haigh don’t bother replying the boiler is at a local scrap merchants and good riddance to a load of old rubbish. That’s my green attempts so far in the energy field but no doubt I have other mistakes to be made maybe even with ground or Air source  heating.

Regards

John

If you’re struggling to understand what @JohnMcG has just written:

a: his carriage-return key seems not to be working

b: here’s the translation -

c: We haven’t yet had a topic about wood/pellet boilers. So when we do, I’ll be referring back to John’s comments and experiences.

In the meantime, just be aware that legislation to combat Global Warming may outlaw certain wood-burning technologies.

If anyone else wants to investigate this subject area, then I would suggest starting with the Windhager range of bio-fuel combustion boilers. These heat the wood and then burn the gasses above it. However the size and capital cost of these is such that they’re of more interest for a small community-run heating plant.

d: @Jess_OVO was quite correct to request that you head over to this topic area, John. It’s not just that we too don’t know where Bio Nordic’s representative has gone, but we also happen to have a box of virtual tissues, if that makes you feel any better

I forgot to ask @JohnMcG - could you provide a (not too technical) explanation of the Zappi and Eddi?

In particular it will occur to some readers that your solar inverter is rated at 6kW, whereas I stated above that the limit for grid export is 3.68kW (16A). I believe it’s the My Energi system which allows this because it limits the total export from the house rather than the rating of the inverter. Have I understood that correctly?

Do you want me to modify my diagram to better show this?

dPostScript: there is now a separate topic on solar load diversion controllers]

So glad you’ve joined the conversation over here, @JohnMcG!

Not only do we have virtual tissues but a resident technical artist in @Transparent who’s really helped me visualise how all your kit fits together. 

Sounds like it’s been a bit of a journey of trial and error, seeing which green technologies fit the bill. What replaced the wood-pellet boiler in terms of space heating?

Great point on this one too, @Transparent. Fancy writing a topic on your experience of them, @JohnMcG ? Be interested to hear the decision making process prior to install and how this compared to the reality of living with this type of heating system… 

Agree with this one ^^

And on a similar note, what about solar thermal panels? First off is there consistency about what these are called? Wet solar? Solar thermal generators? 

How do they compare on costs and ROI vs PV energy generation? @EverythingNeedsAUserName you’ve mentioned this being on the upgrade list. What’s your thinking? @cybermaggedon may be able to step in if they’re about...

Once we have someone here describing their use of a PV diverter to heat their hot-water, I’ll post a comparison of that method v a solar thermal array.

In the meantime, I think we ought to mention Maximum Power Point Tracking.

MPPT is a software system which operates in the solar inverter. This optimises the power being generated by monitoring the power-output and adjusting the current being drawn from the PV Panels.

The example above shows the MPPT formula operating on a 320W panel whose output characteristics are shown by the blue line.

The inverter constantly ‘hunts’ for the optimal output by decreasing and increasing the current being drawn.  Taking too much current causes the output voltage to fall. Taking too little means that available energy is wasted.

A string inverter may have more than one MPPT input port, each of which will have an electrical specification:

• maximum input voltage (eg 500v)
• maximum current handling ability (eg 12Amps)
• MPPT operational range (eg 240-480v)

Provided that these parameters are not exceeded, Panel strings with different characteristics can be connected to each port.

I’ve a friend who has just had her Solar Thermal Panels aka Solar Water Heating removed from an unshaded south facing roof.  She had them installed around 15 or 20 years ago, in the hope that it would reduce her climate impact.  Whilst it did give hot water so that she did not need to heat it in summer, and it helped a little even in winter, it never came close to cost effective.  There was an ongoing cost to maintenance that reduced the benefit, and payback would have been far longer than their life. Her roof needed retiling, and the cost of removing and refitting was prohibitive. Sorry I do not have actual figures. 

I have abandoned any idea of such panels due to the cost which was quoted locally at £6000 to include a larger hot water cylinder that might have fitted into the airing cupboard, and our East/West roofs which would have limited any benefit. Cost of heating water is at present £8-£9 per month based on the amount of gas used in each of the summer months.  Suggested savings were around £60 for a full year. There would have been a benefit from RHI but the system would have to be installed and the RHI applied for before midnight on 31 March 2022. 

...

In the meantime, I think we ought to mention Maximum Power Point Tracking.

 

Thanks - nice explanation, @Transparent.

Non-owner here, but I'm interested to understand what these things are capable of …

I guess you could say that the top of the curve is a ‘target’, @Simon1D but of course the inverter can’t actually take energy from the PV Panels above the blue line. So the point where it crosses the blue line is what is being sought.

From my online research there are a number of different methods to construct an MPPT algorithm, and my diagram is a sort of ‘fudge’ between several of them!

The ‘better’ the electrical characteristics of the Panel the sharper is the ‘knee’ of its curve, and the current tails off rapidly once the voltage rises.

There’s no universal standard for specifying Panels. In choosing the Panasonic HIT ones I was looking for:

• The highest output in overcast/cloudy conditions
• The lowest degradation of output over lifetime of the Panels
• The presence of blocking diodes to prevent complete loss of output if one portion of the panel was in shadow.

So there’s more to this than simply looking for the highest peak-output per m².

The actual HIT panel which I have has now been superseded by a new design, so you can’t just buy the same model. In any case they were pretty expensive. I could’ve bought 340W units from rival manufacturers for half the price. But in my case roof-access was a relatively complex/time-consuming part of the job, and I needed units that could stay put for at least 20-years!

So @Simon1D and I have been exchanging PMs over the weekend regarding the way in which I’ve drawn the above graph for a notional 320W panel.

There are (at least) two issues under discussion

• the graph has two different parameters on the y-axis, which implies a ‘conversion factor’ between them
• I’ve circled the intersection between the two line traces, which does not coincide with the apex of the green MPPT line

I’m hoping that Simon will now post a couple of graphs he’s drawn to illustrate the problem because we can’t exchange graphics using the PM facility of this Forum software

I’m not disagreeing with him.

My graph is considerably simplified from a number of different approaches used to achieve MPPT. You can find these online, and they vary from extremely accurate (academic) mathematical models through to ‘quick and messy’ strategies which take little computational time to create the required MPPT curve.

For obvious reasons, commercial manufacturers of string inverters don’t openly publish their algorithms online for us to see!

Thanks for the prompt, @Transparent. Here goes…

First, my approximation to the @Transparent ‘s graph, with the intersection of current and power curves labelled A, and the maximum power point labelled B:

Next is a graph, plotting the same data, but with the power axis re-scaled a bit:

My comment is only that the point of interest, maximum power, labelled B’ is at the same voltage as before (dP/dV = 0 is a property of the data, not of how they’re plotted), whereas the point of intersection, labelled A’, has moved to a different voltage (the intersection is a property of the plot, not of the data themselves). Another way to put this is that the location of the intersection between I(V) and P(V) depends how you convert from current to power, and rescaling the axis is a way of changing that conversion.

Perhaps this comment is clearer than anything I managed to come up with in our little exchange of PMs, @Transparent? At least having the pictures helps.

PS Since our chat, I went off to read the wikipedia page on MPPT which gives more information. Among other things, I learned that panel temperature has an effect on the shape of the power curve, rather than the panel insolation. Looking at that page again, I notice that it includes this plot

It would be nice to see a set of full P(V) curves, for differing amounts of sunlight, but there is only this indication of where those curves have their maximum point. These voltages have been marked on each I(V) curve and those points joined up to make the slightly wiggly line.

Perhaps a plot like this might be what @Transparent has in mind?