Solar Pv Options On A Shaded Site.

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This concerns my building plot.  I'm planning solar PV, ground mounted.  I face some administrative hurdles that are still preventing me installing this, but in the mean time I'm still planning what's best.

We have lots of trees, so I'm planning ground mounted solar PV rather than in or on roof as that gives me more scope to seek out the bits not shaded.

Initially I was thinking of just putting the array in one place all together on the south side of the plot in a clearing between trees. But that spot is not ideal. It's shaded by trees to the east and west of it, so really only gets full on sun from about 11AM to 4PM.

I've been looking at an alternative location on our eastern boundary. That will get full on sun from sunrise to 1PM (summertime). I could perhaps extend that to nearer 2PM with some pruning but not beyond that.

Working on the assumption we will have a fairly ordinary 4KW G83 system, that will usually come as two strings of panels.

What do you think of the idea of putting one string on the E facing area, and the other string on the S facing area?

The E facing ones would probably be at a fairly low angle, say 20 degrees so they are still working reasonably well when the sun is due S at mid day before it goes behind the tree. I could even arrange a compound slope to improve that a bit further.

The S facing panels would be quite a steep angle, say 45 degrees particularly to catch the mid day low winter sun.

The E facing panels just might get some late evening sun from the W in summer so another reason for keeping their angle low.

Is there any tool that can model the power collected from shaded arrangement like this? I've seen tools to optimise your elevation angle but nothing to deal with shading.

I'm trying to work out if splitting them would increase the overall yield rather than have them all S facing and accepting they won't perform well in the morning and evening.

As well as considering total power collected, I want to try an optimise power that can be used in the house.

It will be a well insulated low energy house heated by an air source heat pump.

My gut feeling is the split system while it might only deliver 2KW at any one time, it will deliver a usable 2KW for a much  large part of the day which is much more likely to be useful to help the ASHP. Crucially I feel good generation as early in the day as possible is important.

By comparison it will be 11AM before you get much usable power from the all S facing only option. That's a long time if you are wanting the ASHP to heat the house and some water "for free" and I feel the higher power but shorter generation of that option would be less useful.

Your collective thoughts please.

 
being ground mounted you could take a chance on using power one micro-inverters - bit cheaper than Enphase, and as they are accessible, if one dies it's no big deal. As it happens I've just bought the full one PVsol package so I could model the whole site for you, and it now supports micro-inverters - long overdue!

You are dead right about useable energy, 4kW pointing south is good for FiT generation, but giving power when you actually tend to use it, ie mornings and evenings. There's been a few articles about East-West being the new South in the solar press lately as the FiT reduces, but energy bills keep rising. Putting the panels at a low angle will help with this, but will compromise the summer winter performance, which is also when you use more energy. Would be useful to monitor your energy useage - if you ask paddler nicely he might lend you his power analyser. With this info we might be able to tailour you energy production to suite.

Would be far more inclined to go ground source than air-source - it has a far better performance ratio. There's a company in Cornwall who will design, supply and commission ground source for you  - you fit it yourself.

 
I'd agree with binky that if you have the area ground source is much better, air source is a lot easier and cost effective as a retro.

ground source would deffo be a LOT more effective for you during the colder spells you experience in the winter, when its needed the most.

I deal with a company in Lytham that actually manufacture heat pumps, and can/will, make a bespoke unit to suit your particular install,

you could either install it yourself [with some help from their tech guy] , or i could help you if you happen to possess a few McEwans and can obtain some dancing girls. :D

 
Here's a plan of my site

Solar PV.JPG

To the right, one possible site for panels is just south of the static caravan, This will get sunlight from sunrise to 1PM (summertime) before the sun goes behind the trees.

The other site is the extreme south west of the plot.

although this looks due south, it won't get any direct sun until about 11AM but by 4PM (again summertime) it gets shaded by a tree in next doors garden (not shown on the plan)

the big south facing gap between the trees looks a possibility, also, but I have ruled that out as there are a lot of overhanging branches and I fear a dropped branch would break a panel. so the two sites highlighted are the only 2 viable spots with reasonable clear views and no overhanging branches.

If anyone cares to model something I would be grateful.

 
The other option is to fit SolarEdge; it gives a similar result to micro inverters, but with a few differences.

I`ve used the kit quite extensively - very good for multiple split arrays with shade issues, or different azimuths.

 
you sure one of the trees can't 'have an accident'.

The Caledonian canal is using ground source direct into the water to heat shower blocks, and provide hot water for showers, you have a burn....

 
dea4d152be.jpg


Apparently they make bikes too :innocent

How about solar tracking? your on navitron aren't you Dave?

 
Trees and planners.

One of my pre commencement conditions was to mark out the site for an inspection by the planners. As well as the building outlines they wanted all the pipe runs etc marked as well.  They are paranoid about damaging the trees that are remaining. They did allow 2 of them at the front to be felled (one came down on Tuesday). I'll be out with the chain saw today reducing the stump to usable firewood.  Lets not even mention the trees in the middle of the plot that came down before the planners got involved.

Having said that the trees there will get thinned over time, but any such pruning will be gradual.

I did think about ground source, but although the heat pumps are not too expensive, the cost of the pipework and the antifreeze to fill them with is surprisingly expensive.  When you analyse a cost / benefit the extra cost over an air source heat pump has a very long pay back time as the saving is small. but I made the decision in time as air source heat pumps need planning permission here, so I included that in my planning application.  If I later choose to go back to a ground source, that is permitted development.

 
that company is about half a mile from my office - but they still insist on delivering :facepalm:   very good prices though.

do copper nails actually work?

 
interesting,

i always thought it was an urban myth,

there is a big tree [tall, but not very thick/mature] a few doors up that shades my back garden dumping yard really badly,

d'ya think theyd have done their stuff by next summer?

 
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