I'm in the process of getting quotes for a 4kW PV installation and am getting conflicting advice on the most appropriate type of panel for a west (with a hint of south thrown in) facing installation. The conflict seems to be monocrystalline v polycrystalline.
Anyone able to throw any light (sorry!) on which would be more appropriate?
I'm also getting conflicting opinions on panel manufacturers with some knocking Chinese manufactured panels such as Suntech and others telling me that German Schuco have issues. Again, any enlightenment(!) would be welcome.
Neither, because your roof faces west, there will not be enough light on it to generate much power until well after noon.
Output will be well below optimum no matter which panel you use. Your only real option unless you're off grid and genuinely have no south facing roof space or spare ground is to put the array on its own support away from the building.
As long as the inverter isn't grossly undersized it will make very little difference to the total power generated.
Unbroken sunshine is not that common in the UK, which means that peak panel output is quite infrequent hence the total loss of power due to undersizing of the inverter is very small. You could guess that you might lose 400W (4kW array, 3.6kW inverter) for 20 minutes a day,
130Whr per day or about 50kWhr per year. Insignificant when you can expect to generate nearly 4000kWhr per year.
On those few days with unbroken sunshine the panels will get hot and ouput will drop to below the inverter limitation.
I have a system with nominal 3.87kW peak output and a 3.8kW inverter. Peak output from the inverter with broken cloud (cool panels) is
3.77kW, so some inverter limitation will be occuring. On the only continuously sunny day that we've had since installation the peak output was 3.288kW, some 15% below the nominal panel output and well below the inverter maximum output.
It varied, depending on who I asked. All (of my sample) excluded PV panels, inverters and cabling from wear & tear or failure, which I would expect to be interpreted broadly. Several excluded _anything_ to do with PV (or wind) systems. One distinguished betweeen an owned system and a "roof for rent" scheme. One would not cover roof damage or future leakage caused by a PV system added to an existing roof. I was asking particularly about branch-drop damage from nearby trees and also kids chucking bricks.
Surely they are connected in parallel are they not? A small amount of shade on one panel indeed reduces its output hugely, but that that form the unshaded ones unless they are wired in series.
I used to have PV arrays on my houseboat to charge 12V batteries (no mains). Robert
Wiring in series is the preferred option by UK installers for domestic grid tied systems. It is the cheapest and quickest method and does not require thick wire to overcome voltage drop.
Transformerless are certainly available, can be fractionally more efficient, but against that is the need for separate earthing of the panels.
In my case, I couldn't justify the extra cost of transformerless (both inverter cost and the earthing provision) in terms of payback.
I'm not sure who mentioned it, but some inverters, like mine, have no fans, and are naturally cooled, which means one fewer component to fail, and also no energy spent spinning a fan.
By definition an inductor is needed in any inverter..and its very arguable as to whether that is a 'transformer'' or not. An inverter is by definition a 'transformer' in its own right, as it 'transforms' DC into AC.
Of all the possible technologies to 'transform' a variable voltage DC source into a fixed voltage AC one, I can think of none that do not require a choke or transformer of some sort. That might be in the limit a ferrite entity of small size working at high frequencies (and blowing away all the broadband in the neighbourhood) but it is still in essence an inductor.
The obvious way to do it is to have a DC to DC inverter to step up from variable panel output to - say 600VDC and than phase chop that into a rough sinusoid and smooth that with a final RF suppression choke. It may be possible to do it in one stage as well, but there will still need to be a transformer in there somewhere.
Careful with the words Mr. Hatter. For clarity turn, as usual, to the internationally accepted definitions of the IEV [1]:
IEV number 151-13-46 EN inverter
electric energy converter that changes direct electric current to single-phase or polyphase alternating currents
and
IEV number 151-13-42 EN transformer
electric energy converter without moving parts that changes voltages and currents associated with electric energy *without change of frequency* [my emphasis]
The generic term is converter:
IEV number 151-13-36 EN (electric energy) converter
device for changing one or more characteristics associated with electric energy
NOTE ? Characteristics associated with energy are for example voltage, number of phases and frequency including zero frequency.
In the limit all real electrical/electronic circuits contain inductance, whether in the form of 'components' or otherwise and whether material to the operation of the circuit or not. Lumped parameters are merely a convenient approximation...
There are many possibilities and it's a very active research field at the moment. Here's one review paper:
Wow, I am surprised. So that does indeed mean that if a shadow falls across any part of the array then the whole array output will be seriously compromised.
When they set these arrays up they must take therefore great care with the positions of local trees (including potential growth over 25 years) or the possibility of people next door building an extension, or anything else that might shade part of the array.
Most do. Some installers might not, as can be seen here:
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is pretty hard to believe that anybody in their right mind would do this.
More trivially, there is a bungalow not far from me which had a small array fitted a couple of months ago. The TV aerial is directly above one of the panels, which is already well spattered with bird droppings.
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