your electricity. There is a guaranteed ‘allowance’ of 4kW on single phase and 10kW on
three phase.
o
Is the access to the roof easy for the scaffolders and installation team?
Step 5 – Research the products
A solar array involves two main components; the solar modules (panels) and the inverters.
There are two common types of module, monocrystalline and polycrystalline. In recent years they
have been considered the same in terms of performance, reliability and cost.
Most modules have tempered reduced iron glass, an anodized frame and are similar in weight and
size. The cell or module efficiency is often referred to but not that important on a large farm roof, as
it is just a measure of the power output compared to the size of the cell or module. A 245 watt
module produces 245 watts of power whatever its efficiency. If a module is described as 16%
efficient compared to another make at 14% efficient this just means the 16% efficient module is
slightly smaller. This is therefore not a major issue on a large roof area and price per unit of power
(watt or kW) is a better comparison when considering quotes.
The inverter is probably the most complex part of an installation as this is a working piece of
electrical equipment. It is esse ntial to match the right inverter to the right solar array to ensure that
maximum output can be achieved. Furthermore it is important to have an inverter with a low
operating voltage so the inverter will start working with less light i.e. earlier in the morning and later
in the night.
Carver Knowles believes that one of the most important issues is the warranty. The products tend to
have 5 or 10 year warranties and obviously the longer the better as it shows the supplier’s trust in
their product. Also check that the warranty covers both parts and labour. The solar modules
themselves should also have a performance warranty. As a guide the warranty should state that the
module should be at least 80% efficient in 25 years’ time.
Some companies can monitor the performance of the installed system remotely via a SIM card. If
this is installed and there is a dip in performance or any other problem, the company are likely to
know before you are aware and can resolve the issue more quickly. This is often an additional extra
and also requires an annual subscription fee for the use of the service.
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