DIY ground mount solar PV install

[scottishjohn]

the new plots are on side of big hill so only angle that would be impeded at all is to the east 

south+west have no restrictions to horizon all day and will get last of sun,as ground to the west drops off 100ft+ to sea level 

so maybe a simple fixed s/w array or split south +west 

will delve into more once I,m on the plot building and can take actual real world sightings for all parts of day 

 

[Onoff]

3 minutes ago, scottishjohn said:

the new plots are on side of big hill so only angle that would be impeded at all is to the east 

south+west have no restrictions to horizon all day and will get last of sun,as ground to the west drops off 100ft+ to sea level 

so maybe a simple fixed s/w array or split south +west 

will delve into more once I,m on the plot building and can take actual real world sightings for all parts of day 

 

 

Solar thermal array at the bottom of the hill? No pump needed/ natural thermo siphoning....

[scottishjohn]

24 minutes ago, Onoff said:

 

Solar thermal array at the bottom of the hill? No pump needed/ natural thermo siphoning....

I just wish i had a stream  then it would be a no brainer --hydro 

I have no doubt i could do a very good solar thermal ,but I,m not discounting solar PV - 

 

I am listening and thinking ,no hard and fast decisions made yet  on PV

but not convinced yet either ,

I expect some new government scheme ,otherwise for most people the equation will not be attractive enough  to invest 

Time will tell 

 

 

 

 

 

[ProDave]

For me the solar PV was only viable because I got the price down by some patience and some luck.

 

We have a burn, but there's hardly any fall. I think I calculated I might get about 50W from it.  It might be a fun project just for fun sake but not a serious source of power.

[Onoff]

I'd love a stream. Best I've got is the road that occasionally becomes a seasonal water course. Before it was a road elderly locals said it was little more than a narrow ditch but that watercress grew along the "banks". This time it joined up with the Darent about 3 or 4 miles down the valley:

 

 

 

Interestingly the watercourse crosses two historic boreholes that I only knew were there due to a link @JSHarris posted.

Edited February 18, 2019 by Onoff

[ProDave]

Meanwhile, inside the "Swiss Chalet"

 

101 uses for an old pallet.  #72, a bike rack

 

[newhome]

28 minutes ago, ProDave said:

101 uses for an old pallet.  #72, a bike rack

 

Do you have a bike for every day of the week? ?

[ProDave]

 

1 minute ago, newhome said:

 

Do you have a bike for every day of the week? ?

Starting at the right is my (now vintage) road bike that I have owned for 30 years. Then the 2 cheap mountain bikes that me and SWMBO ride, the purple one is our daughters bike, and lastly the folding one was given to us by a neighbour packing up to move out. Handy to take on the boat.

[ProDave]

Now this project is drawing to a close, I am wondering what to do with the 2 spare panels.

 

Initially I had thought to put them upright on the east facing end of the shed to catch some early morning sun and get generation starting earlier.  That still seems an option.

 

But I am noticing the generation from my E/W split tails off earlier in the evening than I had expected, there are some shading issues from next door beyond my control and where the panels are was the only option due to all the trees so I am stuck with that.

 

But I do notice, the West end of the shed seems to get good sunshine at this time of year until sunset.  but I don't think both would work there as again due to trees, one of them would get shading early on.

 

So my current thinking is one each of the spare panels on the E and W ends of the shed.  As only one will really be generating at any time, I could connect them in parallel to a small 350W inverter

 

This would give a 200W or so boost first thing in the morning, and again in the evening up until about 6PM.

 

Later in the year when the sun is higher the W facing one would get some shading later in the day, but by then I hope the sun being higher would make the neighbour shading of the main array less severe.

[ProDave]

So continuing with the above post, I am now thinking of fitting these 2 spare panels.

 

As I have decided on one facing E and one facing W to try and squeeze a bit more out of both ends of the day, my thought are turning to a suitable inverter and how to connect them.

 

So they are both 250W panels so a total of 500W (though only one will be producing any meaningful power at any time)  I feep coming back to these very cheap Chinese inverters  https://www.ebay.co.uk/itm/600W-MPPT-Grid-Tie-Inverter-Pure-Wave-DC11-32V-Input-AC230V-Solar-Inverter-BT3D/273358900685?hash=item3fa575cdcd:m:mx85YI3E9iyOMUo2KqEVq5w

 

The input voltage is right for one panel, and it would handle the power from both panels.

 

So how to connect them?

 

I would say connect them in parallel, as only one will be generating at a time.  The question is what effect witll the non generating panel have?  Will it zap some of the power or just sit there as a high impedance load doing nothing?  Should I put s series diode in series with each panel so only the higher voltage panel does anything and the other cannot back feed and zap power?

 

Someone must have done this befoe and know how best to connect them.

 

[Onoff]

10 minutes ago, ProDave said:

So continuing with the above post, I am now thinking of fitting these 2 spare panels.

 

As I have decided on one facing E and one facing W to try and squeeze a bit more out of both ends of the day, my thought are turning to a suitable inverter and how to connect them.

 

So they are both 250W panels so a total of 500W (though only one will be producing any meaningful power at any time)  I feep coming back to these very cheap Chinese inverters  https://www.ebay.co.uk/itm/600W-MPPT-Grid-Tie-Inverter-Pure-Wave-DC11-32V-Input-AC230V-Solar-Inverter-BT3D/273358900685?hash=item3fa575cdcd:m:mx85YI3E9iyOMUo2KqEVq5w

 

The input voltage is right for one panel, and it would handle the power from both panels.

 

So how to connect them?

 

I would say connect them in parallel, as only one will be generating at a time.  The question is what effect witll the non generating panel have?  Will it zap some of the power or just sit there as a high impedance load doing nothing?  Should I put s series diode in series with each panel so only the higher voltage panel does anything and the other cannot back feed and zap power?

 

Someone must have done this befoe and know how best to connect them.

 

 

Ask @binky?

[Jeremy Harris]

Just connect them in in parallel with diodes?  Only one panel is likely to be generating at any time, so with a series diode in the feed from each there's no chance of the non-generating panel loading the output down.  Downside is that the non-generating panel won't contribute anything when it's terminal voltage drops below that of the generating panel, but it might still contribute something, as as it unloads its terminal voltage will rise, allowing some current to flow.

[dpmiller]

Pop the cap off the terminal cover, you might find a diode in there already...

[ProDave]

55 minutes ago, dpmiller said:

Pop the cap off the terminal cover, you might find a diode in there already...

Normally an inbuilt diode is in parallel, and normally reverse biased.  It is there to bypass the panel if it is shaded.  I guess my situation is not disimilar to that and I could try them in series.

 

At the end of the day when I wire it up I will just try it and see what works best, series, parallel, with or without external diodes.

[Jeremy Harris]

Might find it works just fine with the two panels parallel connected.  If it does, then it would be a better solution (in terms of maximising output).  Can't do any harm to just try it and see how it works.

[ProDave]

I have just ordered one of these cheap chinese inverters, this one, the 500W version for £55.81 https://www.ebay.co.uk/itm/1000W-Grid-Tie-Inverter-230V-MPPT-Pure-Sine-Wave-Inverter-50Hz-60Hz-Send-From-F1/323722204850?hash=item4b5f58d6b2:m:mEuwP94Oxr8A8OuF2xH98AA

 

There are many version of this inverter and you have to be careful to choose the one where the input voltage range matches the Vmppt of your panel(s)  In my case the Vmppt of 1 panel is 30.4V, well within the 22-60V range, but some of them are set up for 24V panels so would have been no good.

 

Also worth noting that some of the sellers of these inverters offer them at a buy it now price or "make an offer"  Don't waste your time making an offer, I tried with 2 sellers making an offer £5 under the BIN price and they just came back with a counter offer 10p less than the BIN price.  If they are not prepared to accept an offer, why advertise it?

 

It will typically be about 3 weeks now before It arrives.  I will get the panels mounted on the shed ready in that time.

[ProDave]

I think the panels in parallel idea should work.  

 

Today I mounted the panel on the east side of the shed.  Now well into the afternoon with the sun shining on the W side of the shed and the E panel well and truly in the shade, it is still showing a Voc of 34 volts. So I don't think it's going to bother the active panel.

[ProDave]

So here they are mounted on the shed.

 

The east facing panel basking in the morning sunshine

 

And the west facing panel, at this time of the morning still in complete shade

 

Now all I need is for the cheap Chinese inverter to arrive.

 

[ProDave]

Today the Chinese inverter arrived. I think that is a record for an ebay purchase from China, getting here in just 9 days.  So of course today's job was to install it in the shed with it's big brother.

 

 

I have still got the clamp meter on there to assess it's performance, it only has the most basic of a display.

 

So far it is looking good. It was mid morning before I got it connected and I was then getting 150W from the E facing panel, even though the sun was well on it's way towards south.  And this afternoon as it is moving round to the west, I have seen up to 200W from that panel  Sadly the sunny day has become cloudy and somewhat hazy so that's probably it's peak for today.

 

But it shows the principle that these 2 otherwise spare panels should add some useful extra generation at the ends of the day.

 

[ProDave]

Today is the longest day. From now on the days get shorter.  So it seemed a good opportunity to evaluate the first half years figures. So having just done my weekly meter readings, here are the headlines:

 

Generation since late January 923KWh.  Export since late January 57KWh  So self usage 866KWh.  At my current electricity unit price that is a saving of £128

 

If the second half of the year mirrors the first then I should be able to hit my self use target of £250 pa

 

The total generation is well down on what PVGIS predicts. That is partly down to choosing an E/W spit in the hope that will make self usage easier.  But the big issue that has come to light is those damned trees, and shading.  I sited the panels on the one bit of garden that I though was largely clear of shading, and that seemed true at the start of the year. but as the sun got higher and the trees grew their leaves, it became clear there is a big shading problem in the mornings from the trees to the east of the panels that overhang a lot more than I appreciated.  There is also a shading issue in the late afternoon from a tree in next doors garden.

 

The trees to the east are mine, and I will be felling some of them, but I can't do that until the autumn as I will need to drop them into the field behind us, so can't do that now until after harvest.

 

The total export is lower than I expected.  Most of that occurs at mid day on a sunny day when the panels generate more than the immersion heater can use, and if nothing in the house is using significant power.  If I was able to sign up to one of the new export payment schemes, I would have earned £3.13 for that export, or a predicted £6.26 per year.  But to be able to claim that, I would have needed to have paid an MCS contractor to install it.  I think it is safe to say the extra MCS cost would never ever be recouped by that tiny export payment.

 

If you want to drill down into more detail about usage, it is worth noting that my PV dump controller has sent 324KWh to the immersion heater so far this year.  That means only 542KWh has truly been used by something that would otherwise have imported power.  It could be argued that the heat that has gone into the immersion heater has saved  the ASHP from heating water. Assuming a COP of 2 when heating hot water, that is a real import saving of perhaps only 162KWh  So perhaps the true saving is only 704KWh or about £105 actual reduction in electricity bills.

 

Another point of interest, peak generation year was week beginning 10th May.  Even this week has been lower. That may be the point when the sun got high enough to show up the shading problems, or it may just be that for the last 5 or 6 weeks the weather has been pretty lousy for the time of year?

 

 

[Jeremy Harris]

The last couple of weeks haven't been great here, May was generally better than June has been so far.  Today was the first day for a couple of weeks where we were generating enough to charge my car, for example (it's now fully charged and we're exporting - damned nuisance given that there's nothing else we can do with the power at the moment!).

[ProDave]

Since we got back from our recent holiday,  our import meter is now alternating it's display between the meter reading and "rEd"

 

This means Reverse Energy Detected, and a lot of import meters have this "feature" to detect if there has been an attempt to run the meter backwards to fiddle your bill.

 

An unintended consequence is someone with a PV system with such a meter will trigger this function.

 

I am not sure why it has taken until now to activate that feature. Is it perhaps that the total "backwards" power (now about 97KWh) has gone over a threshold?  Or could it be it is triggered by a certain power level of export?  It is most unusual for us to export more than 600W as the immersion heater soaks up the rest, but I will bet while on holiday there will have been periods with no hot water being used when the immersion thermostat had opened and with nothing to soak up the PV generation, then over 3KW could have been exported at times.

 

I am in 2 minds whether to do anything about it (request a meter change) or just let it be.

[MrMagic]

@ProDave Mine does exactly the same - it's either rEd permanently on when exporting or cycling when not exporting (which I guess is a warning to a meter reader that 'rEd' has happened at some point). This is on a brand new meter that was fitted as I advised my energy supplier that my old meter was spinning backwards.... so I think this behaviour is 'correct'.

 

If in doubt contact your energy supplier.

[SteamyTea]

Bit late to this party.

On 14/02/2019 at 13:40, ProDave said:

Now comes the issue of registering this with the DNO

 

On 14/02/2019 at 13:40, ProDave said:

So they want a drawing of the installation, and a "commissioning form"  

The commissioning form is just there paper trail form.

You need to add this each time as well

On 18/02/2019 at 10:06, ProDave said:

declaration of conformance from the manufacturer stating it was G83/2 compliant

It frustrated me no end as I could be sending several of them a day, for the same inverter, just at different address.

Just they way they work.

The other thing they (Western Power) were keen to know was the physical location of the AC isolator, they were not too bothered about the DC one.

[Jeremy Harris]

Our meter also shows the rEd message, as did our old meter.  Seems to be normal and doesn't bother the meter reader, but then there is also the mandatory warning sticker in the meter cabinet that lets anyone know that there is a PV system installed.