Ground mounted solar PV installation project

[DAPPH]

Now I've got the camping trailer just about complete, I'm starting on some solar PV with battery storage. We don't want to put solar on the roof of the house. Apart from 22.5 degrees not being a good angle for solar efficiency up t'north, it's and old stone building, probably around1750s and it would look pig ugly. Plus the roof are sandstone "slates" called grey slate locally, so not ideal to attach stuff through.

The wife has identified a small piece of land that she doesn't want to cultivate. The good thing is that its bang on south facing. The bad bit is that its a bit of a pig to get to and its next to our boundary. its also a bit small, ideally I would have liked twice the area, but we have discussed this at length. It was the site of the old Calor tank and wouldn't be used for anything else, so its a good use of a rough bit of land.

I'm not going to discuss planning on the forum. This may prove difficult and I would rather French kiss Liz Truss than go through this with our planning department, let's just say its not permitted development and leave it at that We have told all the neighbours, and none have an issue as long as they are camouflaged a bit.

Here's the rough site survey. I'm going to do more detailed one once I get the strimmer out.

View attachment 358803

As per the text in the pics, I'm going for 3 rows of 4 panels. I need to make sure that I don't shade the panels behind so worked out the max angle I can tilt at is 41 degrees from the horizontal.

View attachment 358804

This assumes the panel is right on the floor, no gap, in reality there will be a bit. I'll rerun the calcs once I've done a better survey with a longer tape and somebody to help.

The height is important as I have promised the neighbours that they won't be much higher than our boundary wall. about 1.2m should be fine, the wife is thinking of adding a bit of trellis to make sure.

I'm thinking of making this a manual tilt system. So, I can adjust the angle of the dangle every couple of months to improve efficiency. The next thing was to understand the best angles at different time of the year.

The rule of thumb is the latitude minus 15 for summer and plus15 for winter, So between 38.7 and 68.7 degrees summer to winter.

A supposedly better method is during winter, multiply the latitude by 0.9 and then adding 29°. this gives 77.36 max angle. For summer, the tilt angle is calculated by multiplying the latitude by 0.9 and subtracting 23.5°. this gives 24.86 max angle so a much wider range, 23.5 to 77.36 degrees.

There are also various sites with calculators where you stick in your latitude or city. Interestingly, none of them gave the same result and they are different to the above. Here's the output of one of them, this one https://footprinthero.com/solar-panel-tilt-angle-calculator.

Optimal fixed angle
36.8° from horizontal
Your optimal tilt angles by season:
Spring: 36.8°
Summer: 21.8°
Fall: 36.8°
Winter: 51.8°
Your optimal tilt angles by month:
January: 46.8°
February: 41.8°
March: 36.8°
April: 31.8°
May: 26.8°
June: 21.8°
July: 26.8°
August: 31.8°
September: 36.8°
October: 41.8°
November: 46.8°
December: 51.8°

Using the above, my max angle of about 41 degrees means I would only be suboptimal for 3 months of the year. I'll do a bit more reading on this one, I don't like when stuff like this differs from the site to site

Given I can't get a machine in to level the land without taking down a dry stone wall, I'm going to concrete in some unistrut posts, or similar and build off of those. I have a dozen bags of postcrete that need using up, I may need a bit more postcrete but I'll dig nice deep holes so the structure will weather our winds ok.

Cheers
Andy

I do believer Soay ( sp?) sheep make good grass & weed cutters for keeping the weeds down and you don't need to hoof trim them , a couple in the fenced off area with some shelter & water could see you have a tidy site and two lumps of meat for the freezer .

 

[Gareth J]

Also recommend PVgis tool.

A few thoughts; do you need to consider maximising output in summer? Most people have more solar than they know what to do with for at least a few months. Better to compromise on efficiency then and focus on the winter.

Is this really the limit of space? If not, how would adding more panels, potentially at different angles compare with the added cost/complexity of pivoting framework?

 

[brewdexta]

I did pay a local installer to do a full survey for me about 3 years ago with the intention of putting shed loads of solar on the barn roof which is east/west facing. The result wasn't that good cost wise, although prices have come down a bit. He went out of business but as I paid him I ended up with a detailed design

Not wanting to go into planning issues, we are in a corridor of outstanding natural beauty or similar which means that normal planning goes out of the window and they seem to make it up as the go along.

It doesn't help that when I see a south facing banking in the field, I think that its an ideal location for solar, the missus sees a habitat for flora and fauna.

However, I do have a possible plan for more, but in a different location I'm treating this as stage one.

 

[addjunkie]

I did a dash yesterday to get a set of belts for my big mower. Enroute I drove past a field of solar. It just looked wrong if you know what I mean, completely out of place. Im no eco warrior or nnatural habbitat extremist by any means, but good fields full of solar just makes no sense, trying to be green and importing food across the world.

But a few panels on-a bit of scrub, useless ground Im all for it. In my opinion every new build domestic or commercial should have them by law.

As for planning, we are national park so fully understand your view. Our new guy isnt too bad and can actually be helpful if you get him out. The old one would rather have a pile of rubble and derelict barns, than allow you to rebuild / modernise to make useful.

 

[northwest]

The old one would rather have a pile of rubble and derelict barns, than allow you to rebuild / modernise to make useful.

I have met and tried to deal with this type of person. I quite simply don't get it and it really messes with my head.

 

[brewdexta]

I've had a think about solar panel spacing. Modelling is fine but you can't beat the real world. In the interest of just getting on with it, I'm going to make it adjustable. I'll put in at least 6 hot galvanised unistrut posts then run unistrut lengthways so I can move panels along it as necessary. That way I can space panels or squeeze more in etc. Any height adjustment will be part of the frame that sits on it and i will make them adjustable too.

I'll get 12 panels to start with. If I find that I can squeeze more in then I can always buy more.

All this unistrut takes me back to my BT days when I used to construct transmission systems in telephone exchanges. You built all the iron work, mainly unistrut and tie bar, installed the cabinets, all the DC power bus bars, installed the equipment and commissioned it, happy days.

 

[brewdexta]

How are you finding the pellets working out versus oil? I nearly got involved in pellet production a few years ago, but decided the cost savings weren't quite enough to justify the investment (I was looking at production rather than end-use and it seemed to me that the price of pellets was folowing the price of oil a little too closely rather than being a straight cost-of-production plus profit margin equation) What also put me off was too many stories about pellets being imported that were either largely dust or hadn't been sealed properly so had absorbed moisture and converted to sludge... then the final nail in the coffin was finding that some of the big cattle feed companies were diversifying into the field and obviously had several major financial advantages!)

All good so far. The pellets come from an Austrian timber construction component company as a byproduct. They use offcuts of wood to fuel the production process. The timber came from managed forests in Siberia, so that will probably change to Polish forests of similar, and the price will go up. It's cheaper than LPG that we had before, and the last time I looked it was more expensive than mains gas, which we couldn't get at the time.

 

[Gareth J]

I know you're not going for planning and that sounds wise. But I recall something to do with planning and making it a "temporary" structure. Potentially by bolting to concrete railway sleepers. But in your case maybe by making sure anything concreted in the ground has the concrete hidden by 6" of topsoil. So it looks like they're just hammered in. Hopefully you'll never have to worry either way.

Another thing that is concerning is that boundary wall. You mention it has a height and that the panels are to be more or less lower than it. What about shading from the East? That's going to hamper those closest panels 1/2 the time, which also, unless you have lots of strings, or microinverters (do they work with battery setups?) will drag the output of other panels in their string down.

 

[brewdexta]

I know you're not going for planning and that sounds wise. But I recall something to do with planning and making it a "temporary" structure. Potentially by bolting to concrete railway sleepers. But in your case maybe by making sure anything concreted in the ground has the concrete hidden by 6" of topsoil. So it looks like they're just hammered in. Hopefully you'll never have to worry either way.

Another thing that is concerning is that boundary wall. You mention it has a height and that the panels are to be more or less lower than it. What about shading from the East? That's going to hamper those closest panels 1/2 the time, which is also, unless you have lots of strings, or microinverters (do they work with battery setups?) Will drag the output of other panels in their string down.

Unfortunately I have no answer for the wall, however the hill to the east means that the wall is just in shade anyway, that is just part of the fun of being in the Pennines. Not ideal but not much I can do.

I may be going for planning, I'm just not saying or going into the boring process on here

 

[gaz1]

Unfortunately I have no answer for the wall, however the hill to the east means that the wall is just in shade anyway, that is just part of the fun of being in the Pennines. Not ideal but not much I can do.

I may be going for planning, I'm just not saying or going into the boring process on here

not forgetting there is council planning officers on here as well

 

[julianthegypsy]

I looked at building a panel controller ages ago and it really didn't look difficult or expensive to make it move to follow the sun every ten minutes, and the difference in output was significant. I think I still have some photosensitive resistors and an Arduino somewhere in a box of old project stuff to get round to one day!

 

[gaz1]

I looked at building a panel controller ages ago and it really didn't look difficult or expensive to make it move to follow the sun every ten minutes, and the difference in output was significant. I think I still have some photosensitive resistors and an Arduino somewhere in a box of old project stuff to get round to one day!

they might be ok but you still need auto track points when theres no sun around so the unit auto tracks to those points at specific times

 

[Gareth J]

Unfortunately I have no answer for the wall, however the hill to the east means that the wall is just in shade anyway, that is just part of the fun of being in the Pennines. Not ideal but not much I can do.

I may be going for planning, I'm just not saying or going into the boring process on here

The answer might be to run it in 2 strings (will almost certainly be a two string inverter with x12 panels) or even 4 strings vertically (in your pic) so that the morning shading only drags down the panels with shade on them. Or to fit panels with microinverters. Again, not sure about these with battery storage but they may work ok if your battery storage can be at the meter so it just hoovers up AC before it escapes out to the grid. But that'd mean more expense.

 

[brewdexta]

The answer might be to run it in 2 strings (will almost certainly be a two string inverter with x12 panels) or even 4 strings vertically (in your pic) so that the morning shading only drags down the panels with shade on them. Or to fit panels with microinverters. Again, not sure about these with battery storage but they may work ok if your battery storage can be at the meter so it just hoovers up AC before it escapes out to the grid. But that'd mean more expense.

I was planning on 2 strings so that works.

Just completed the fag packet unistrut drawing on the train to London so I can get some ordered and get the groundwork done.

 

[gaz1]

something to consider

tracking vs fixed

this one is based on panels at side of each other in long lengths and tracks

ignoring its a parbolic solar water the refererence can be used with just one motor and greased bars

 

[DAPPH]

Also recommend PVgis tool.

A few thoughts; do you need to consider maximising output in summer? Most people have more solar than they know what to do with for at least a few months. Better to compromise on efficiency then and focus on the winter.

Is this really the limit of space? If not, how would adding more panels, potentially at different angles compare with the added cost/complexity of pivoting framework?

A local church in Saron have their panels lent against the buildings walls , all that holds them in place are 20 litres of salty water in plastic containers hung off the back so they are at the right angle . It looks like they are sat on pea rit laid on a double weed proof membrane to hold weeds at bay , the rest of the bone yard gets cut regularly so it looks like a lawn .

 

[willie.macleod]

Charge EV during the day when there is sunlight, only needs doing once or twice a week. We have a 7kw charger so even on a sunny day our PV isn't going to cover all of that.

You can dial the EV charging down to 2.3kW easily enough if that helps by using a granny charger or your existing EVSE/car may be also be able to adjust the charging rate.

I do believer Soay ( sp?) sheep make good grass & weed cutters for keeping the weeds down and you don't need to hoof trim them , a couple in the fenced off area with some shelter & water could see you have a tidy site and two lumps of meat for the freezer .

Hoof trimming will be the least of your issues with Soays, I reckon they'd be running up the panels and launching themselves out of there in search of the ever greener grass in the neighbours garden.

 

[brewdexta]

In terms of tracking, maybe next time. For now I shall keep it simple so it will get done this year

 

[brewdexta]

I had a quick look at the PVGIS tool, very nice

It gave an optimal fixed angle of 39 degrees giving me 3379kWh in annual production from a 4kWp system.

Going to the tracking screen, just using tilt angle, not vertical tracking, this increased to 4176kWh annually, but that will be automated daily tracking, not my intended manual change of angle every month or so.

So, changing the fixed angle is probably the best way of modelling this, but that assumes the same angle all year, so an average. 25 degrees gave 3328kWh and 45 degrees gave 3356. So not much in it.

Looking at individual months, for example May, at 39 degrees I could achieve 451, but at 25 degrees I get 465.

So, my conclusion is that aim for 39 degrees and if I can be bothered to get the spanner out and loosen 6 bolts a few times a year, I may get another couple of hundred kWh.

But, if after the site survey 39 degrees causes a lot of shade, lowering that a few degrees wont' make much difference.

 

[Gareth J]

You can, with PVgis, input a horizon profile that'll include the shading. (I think it's PVgis anyway. If it isn't, let me know and I'll try to remember where it is I saw it)

With that in mind, it might be worth considering running a comparison scenario with/without the panels closest to the wall/boundary. The money saved might be better invested in more battery storage or hanging the panels vertically on a south/SSE/SSW wall.

Also, when choosing your optimum angle, remember that overall productivity isn't necessarily the goal. It's not like the days of FiTs. What I mean is, an extra kWH in summer, when you're potentially already producing more than you can use is of near zero value. Sacrificing it, to gain even a portion of a kWh over winter might be worth it.