Residential solar panels pitch considers whether there is an alternative to PVs on your roof.
There are numerous difficulties associated with erecting your PVs on the roof of your home; here are a few that come to mind.
At what angle should you pitch your residential solar panels, and on what sort of structure should you position them?
I could add others; like, in the case of our home, of necessity the panels are distant from the inverter. It makes sense to have your PVs close to the battery room.
Then, there's no doubt that they are a bit of an eye sore, for your neighbours in particular. In fact, in some residential complexes, any structures on the roof are banned.
Having gone through the whole process of building a solar generator on and in my home, facing all these difficulties, I would do it differently if I ever was to undertake a similar project again.
So, if you're planning to go green and plug into Mr Golden Sun as my granddaughter calls him, then perhaps give this at least some consideration; it's worth a thought.
Obviously it depends on the circumstances of your property; for some this wouldn't be feasible. But I suspect most of us could use some extra garaging for our cars, bicycles, lawnmowers and your other hobbies.
Residential solar panels pitch invites questions about the angle of your PVs.
Instead of what I have above, I'd pitch my residential solar panels something like the structure below, without the fancy shaped thin film PVs, and brick it in to make a secure and dry place for the batteries; and of course a garage or workshop.
These residential solar panels pitched just right is even better, but of course they are shaded in the early morning. I spotted them in a small fishing village in Holland; the Dutch are masters of water and solar.
Shadows on PV panels is a very important consideration; block one and all those in series won't perform at all.
Ideally your panels should be at right angles to the sun for maximum efficiency; that in itself creates difficulties. The angle of declination of the sun changes with the seasons.
There are highly sophisticated tracking systems, but they are very expensive and most likely far beyond the average home owner.
So mostly the recommendation is that your PVs should be angled to the declination of the sun. In my case that's 30 degrees but yours could be considerably more or less depending on how far you live from the equator.
In fact, because of the shorter days in winter, and the sun is lower in the sky, you might want your residential solar panels pitched at an extra five or ten degrees.
But I settled for 30 degrees because our winters are dry and cloudless, whereas the summers are often wet and misty.
In our region, on average, our panels actually produce more energy in the winter, despite the shorter days and lower declination, than in the summer.
Then to catch the early morning and afternoon sun, which is when most of the power is often being used, I'd have two extra strings of panels that are facing east and west, or perhaps slightly NE and NW.
They are dedicated to getting you extra energy for the early morning coffee and breakfast, and preparing dinner; for that you would want maximum power early and late in the day, when the sun is low. They need to be angled much more steeply, say at 45 or even 60 degrees, accepting they would be less efficient for the rest of the day.
So, to avoid using the roof of our house, what would I do? Firstly, the panels still have to be up high because our home is surrounded by lofty trees.
So, erecting them at ground level, which is certainly the best option, simply isn't feasible.
I would build a garage, with a pitched roof, but perhaps without cladding; the photovoltaic panels would be the covering to keep the rain and weather out. It may be necessary to put in a layer of sisilation to keep the building dry; or simply a silicone sealer.
At one end of the garage, I would build the battery room, and that would have to be properly walled and clad to prevent any rain getting in; water and electrical equipment don't go together, do they?
Whether you decided to brick in the walls of the garage is up to you, and your circumstances. In South Africa we would certainly make the whole structure secure. But the battery room itself must be safely enclosed.
That safe room would also house the MPPT and inverter. They need to be as close to the batteries as possible as the voltage is low, and the current very high; that means big heat losses in the cabling.
Using a scaffolding it would be very easy to work under the panels, connecting up the wiring. Clambering around in the ceiling was pure misery.
The inverter produces high tension 110 or 220V, AC, so the current is relatively low, according to the formula, power is equal to the product of the amps and volts.
Raise the battery voltage from 48V, which is the recommended option, to that of the mains and the current halves or quarters depending on where you live. Since heat loss is proportional to the amps squared, so sending your electrical power some distance to your distribution board is much less of a consideration.
The high tension line would either be strung across the gap between the battery room and the mains distribution board in your home, or buried underground.
So, there's no clambering around in sweltering ceilings and no danger of electrical fires damaging your home; and you've gained a garage at nominal cost, with no roofing, for your car or paraphernalia. The photovoltaic panels are the cladding.
If you're fortunate enough to work from home, it's the perfect place to charge your electric car or motorcycle during the day when the power is free.
And the cabling between the panels and the MPPT is shorter than usual; less cost of copper wiring, and fewer losses. I should get 3200W from my panels but because of the long cabling, it's only 2800W. Now with the extra 930W of west facing solar panels we regularly maximise at 3500W and more.
Residential solar panels pitch; make it the angle of the declination of the sun at your latitude, and build a dedicated structure to support the panels and house the batteries, inverter and MPPT.
Read more about Joule heating at Wikipedia, if you're interested.
Worth a thought, eh?
Bite the bullet and purchase at least a 60A MPPT, 5KVA inverter and a minimum of 3kW of panels, allowing for more if need be in time.
I didn't plan properly and went from a 2kw inverter, to 5kw to 10kW. You should be smarter and go big the first time to avoid the necessity of a solar powered generator upgrade.
And if you have a large expanse of ground, and no trees, put your panels on the ground; otherwise build your residential solar panels, as suggested, pitched on a separate building with no other hard cladding.
Grid tied is my first choice, if you have a good utility, but in many third world countries the power goes off every day, and brownouts are common; you need expensive batteries. But either way, the residential solar panels pitch is important.
Avoid another mistake I made; whilst your PV panels facing due south in America, should be at the angle of declination, should you decide to include west and east facing solar panels for the late afternoon sun, make them steeper for when the sun is low in the sky. Most homes have too much energy in the middle of the day and not enough for preparing breakfast and dinner.
Just what are the options in terms of grid tied, batteries and the mains supply? Read more at total blackout. Just what happens if your utility company loses control of the grid?
The MPPT, or maximum power point tracker, is a smart, ingenious device that, by keeping the voltage in the cabling high, enables you to extract about a third more energy from your panels. It's dependent on the voltage of each string being equal, or at least nearly the same, so residential solar panels pitch is important.
So, your string of east facing panels would need a separate MPPT, as would those looking out to the west.
In short, one large MPPT, probably 60amps, for the panels that are north or south facing, and two smaller for the east and west panels; the voltages would be too disparate to have only one.
For more information, you can read up about the solar charge controller MPPT here; you have to have at least one if you have batteries.
Day in the life of solar geek Bernard Preston
» Residential panels pitch
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