What is a solar panel?
How do solar panels work?
A solar panel converts sunlight to electricity. Sunlight is composed of particles known as photons. Solar panels absorb the photons and initiate an electric current. When this occurs electrons are knocked out of their atomic orbits and released into an electric field produced by the solar cells which pull these free electrons into a directional current. Otherwise known as the photovoltaic effect.
Module types – what’s all the hype?
There are many different module types in the market and yes they all have varying points of difference so let's break this down a little more…
Mono v Poly
Monocrystalline and multi or polycrystalline refers to the manufacturing process to create the cells. Mono-cells are more expensive to produce and typically have higher cell efficiencies. However, polycells are usually cut in square cells, therefore, they might achieve a greater efficiency of panel coverage and they can work more efficiently at higher temperatures.
You may notice that some of the more expensive and otherwise better quality manufacturers like Sunpower, REC, and FLEX offer monocrystalline cells technology with their higher quality panels.
60 Cell v 72 Cell Modules (panels)
This simply refer to the number of cells on a panel or module. So, 60 cells or 72 cells. Therefore, it is reasonable to expect that larger cell or 72 cell panels will be bigger in size to accommodate the extra 12 cells.
60 Cell panels are typically found on panels with wattage ratings of up about 300 Watts. And typically panels larger than 300 Watts will be 72 Cell panels.
So for those who say bigger wattage panels are better is not necessarily correct as all they are referring to is the wattage of the panel and therefore the dimensions of the panel to accommodate the number of cells it contains. Remember, the larger the panel the larger roof space required to fit the panel so some residential jobs are not suitable for the larger panels and others are due to limited roof space – sound confusing? Call me for that one!
Always remember your installer must carry these larger panels onto your roof (usually by ladder) so think of their back and safety;)
N-Type v P-Type
This refers to the type of silicon used to make the cell. A P-N layer needs to be made to create the electric field within the cell. Essentially this is a ‘doping’ process using boron for P-Type and phosphorus for N-Type.
Historically P-Type has been used in the solar industry with premium quality manufacturers like REC using N-Type in their latest high end solar panels. There is a premium price for N-Type silicon cells due to additional costs in the manufacturing process.
Half Cells – WTF?
I thought everything was getting bigger so what are these half cell panels? Half cell modules are relatively new tech. When you half the cell you half the current. This process can increase performance by 5-8 Watts per module.
Again a leading innovator with this technology is REC with their N-Series panels.
This is a relatively new technology that uses a double glass construction which allows light to enter from the rear of the panel and the front. So, not very beneficial when mounted on a typical rooftop installation but very beneficial for some commercial installations and more importantly ground mount installations where the panel is significantly off the ground allowing sufficient light to enter from the rear of the panel as well as the front surface.
Don’t let some slick fast talking solar salesperson talk you into these for your home rooftop job – pointless!
I am about to reveal insider information as to what we pay for solar panels per watt! But don’t forget we have STC’s to consider, an inverter or optimised inverter, rail and racking, electrical kits with isolators (we refer to this as BOS or balance of system).
These days (late 2018) we can buy wholesale at a typical price range of $0.45 / Watt (value range) to $1.49 / Watt (high-end premium panels such as Sunpower).
I know first hand there are cheaper panels available, but we choose not to offer these to the market as we do not want to stand behind a less known product or one we simply think you should NOT buy.
Be careful of cheap solar panels and inverters found on sites such as eBay or Gumtree and Facebook. These products may not be on the approved product list so no STC’s will be offered or worse still you may not be allowed to connect them to the grid (off-grid not an issue). Check your products here: http://www.solaraccreditation.com.au/products/modules/building-approved-modules.html
I don’t want to be honest here to tell you I don’t really know but, it's not far from the truth in some respects. It’s actually hard for us to tell some panels apart!
Sometimes it comes down to the fact there are a few panels you should not go with no matter how low the cost.
Then there is a range of say ‘good’ panels very similar spec to each other. Then there is a range of ‘better’ panels and three or four very high end manufacturers where if you want the ‘best’ then here they are!
Some key points to consider when making your selection should be:
Performance and workmanship warranty?
Is the panel PID free?
Salt mist and erosion tested? (90% of Australia is on the coastline)
What is the power temperature coefficient (Pmax)?
Trade history of the manufacturer?
The best advice I can give is that you must trust the company you choose to deal with. You must trust that they have done the hard work and research to make the best offerings available to you.
I take the approach that although I may typically work with a certain selection of manufacturers I will not be scared to offer a similar but different product should it be offered at a great price.
The best efficiency is achieved when the solar panel is perpendicular to the suns rays. Solar modules absorb solar radiation from the sun directly or from the sun reflected off clouds or the area surrounding the module.
Remember, the sun rises in the east and sets in the west. It is also higher in the summer sky than the winter.
Advanced tracking systems or solar trackers maximise production by following the sun throughout the day and throughout the year by achieving optimal efficiency at all times possible.
You may see these systems on some commercial or industrial installations but not on residential due to much higher costs and engineering needs. The most economical way is roof mounted.
Azimuth is the angle measured in a clockwise direction from north referring the direction the panels are facing. In the southern hemisphere true north is the best.
Like most buildings, we are limited to what we have to work with. If you are building a new home you may want to consider this as part of your design requirements. In fact, if you are serious about energy efficiency then design the entire home with better thought into passive light, heating/cooling, ventilation and insulation to massively reduce the required energy inputs to maintain and sustain the home. You will be far better off long term.
However, if a north facing array is not possible the following are generally the next most desirable depending on your energy behaviour: west, east and yes even south!
In the past, we must consider the economics. How much as solar some down in price? A lot right!
So what most people don’t realise is some people are actually better with a split east / west array than a north.
Well in some cases this layout more closely aligns to the energy use pattern than a north array. Yes it misses the midday peak but gets better early and late yields than what a north facing system does.
And south facing – you must be kidding?
Well no! You may not be aware but let's say you have a 30% loss having panels on the south. Then why not put an extra 30% of panels up to make up for the loss. If you have space and have no alternative, then this makes sense – economically.
The reason you never would have done this in the past was simple maths or ROI (return on investment). Cheaper solar means great flexibility with respect to installation options. Also, we have some great new technologies that help deal with greater yields, in less than favourable light conditions, shade, mixed arrays, panel mix match otherwise known as optimizers or microinverter systems.
Rule of thumb: ideal tilt angle = latitude (Brisbane 27.5 degrees). This is why people elect to use a dual axis tracking system so they get maximum efficiency on the direction and angle at ALL times.
For most rooftop installations this is governed by the pitch of the roof. Most roofs are between 15-25 degrees. Again if you have less than ideal pitch/orientation then adding equivalent panels the corresponding reduction in maximum efficiency can be off-set!
The alternative is a personal dislike of mine – tilt angles! They can be a total eyesore looking at the roof on an otherwise nice home with fin like looking things coming up off the roof – hell no! Add more panels. We even do commercial jobs with close to flat roofs without tilt. We again just add more panels to make up for the loss. This usually comes down to available space.
How does the weather affect my panels?
Solar panels are in very harsh conditions in this country. Some regions have temperature fluctuations of minus 10 degrees to plus 40 degrees! Raining one minute blistering sun the next, not to mention wind blowing sound storms and cyclones and frost or snow. Yet, your solar panels can keep producing power! But what effects do these things really have?
People naturally think Australia lots of hot sunny days great for solar – not exactly right! Before Australia jumped on this bandwagon who was leading the charge internationally? Germany. Is Germany hot and sunny? No.
Even New Zealand has great conditions for solar. Did you know the bottom of the South Island of New Zealand has similar or better conditions than Germany? It does. But why?
As the temperature rises the performance of the solar panels reduces. This is a fact.
This should be something to consider when buying solar. The cheaper lower grade panels do not offer the same benefits to helping you get a better yield. Something to look at on a data sheet is the power temperature coefficient (Pmax) – the lower this number the better. Ask us we can explain it in more detail.
Yes, clouds reduce the performance because less sunlight is reaching the panel.
Rain can come due to the clouds so as above but, rain can be good because let's face it the panels need as wash too.
Wind can have a cooling effect so wind can be good but, if your installer has a regular spot on ‘crap solar’ (Facebook) this can be a bad thing for you! Caveat emptor.
Panels are tested to withstand a minimum of 25mm diameter hail at 23m/s. Hail can damage the glass which in turn reduces the performance of the panel and therefore the entire system. This panel needs to be replaced.
A direct lightning strike can cause damage to your system. If you live in a lightning prone area you can install lightning protection.
Not such a big deal in most of Australia but again the panels are designed and tested for this outcome. Snow has a similar effect as does shade. We recommend microinverter or SolarEdge optimized systems to improve overall performance.
Salt Water Mist
If you live on the direct ocean you obviously have money invested in your property so make sure you get the best advice when choosing the best panel and system for these locations. Not all panels are created equally! Also give it a wash regularly.