What is solar power?
We’re pretty sure you know what it is by now, but how does a solar panel make electricity from the sun?
The “photovoltaic effect” was discovered way back in 1839 by French physicist Alexander Edmond Becquerel while he was fooling around in his dad’s lab. The first ‘real’ solar module was created by Charles Edgar Fritts in 1883 and shown to Werner von Siemens (yep, that Siemens) who gave the invention his stamp of approval and a new way to harness free energy was up and away. It took a few more decades of tinkering with the materials needed to make large scale manufacturing of solar (PV) modules affordable and plentiful. The most common forms of PV modules are now made from silicon, phosphorous and boron.
Without getting too nerdy, when sunlight hits these elements, the combinations of materials at atomic level are ‘excited’ and loosen up electrons, that travel this way and that and produce an electrical current, which is harnessed and directed toward an inverter.
An inverter is needed to turn the wild, untamed DC current produced by the PV modules into the nice and friendly AC current that is used in our homes via power points.
After huge efficiency gains in the 1970’s, most research and development dollars continue to be spent in improvements to a PV cells efficiency percentages. From only 1% in the 1950’s most solar panels now work in the 18-22% efficiency range, with improvements occurring all the time.
So what is the best solar panel to use on my home?
We’re pretty lucky here in Australia because we have several government and non-government entities that keep a pretty tight watch on the solar industry to make sure resellers and installers are doing the right thing by their customers. That said, there will always be some dodgy operators that try and cut corners and sell substandard product. As a first, we recommend you seek out CEC Approved Retailers or, in other words, businesses that have passed higher standards as laid down by the Clean Energy Council.
These Approved Retailers are all committed to industry best practice and all offer high quality components, including panels. They will get into a world of pain if they don’t comply with the standards as set out by the CEC, so you can be comfortable knowing you will be offered a great panel that works well and lasts 20-25 years. There are stacks of brands on the market but these days, at least in 1st world Australia, the majority of brands offered are Tier 1.
What does Tier 1 mean?
There is a bunch of jargon associated with solar panels so let me explain some of those terms unique to the industry.
Tier 1: International ratings agency, Bloomberg, came up with a set of criteria for classifying solar panel manufacturers. To qualify for Tier 1, the manufacturer must
a. make not just solar panels
b. have a turnover beyond $1Billion US
c. spend at least 10% of that turnover on research and development
d. have a dedicated office in each of the countries it sells into
e. have proven efficiencies over 16%.
Bloomberg update the Tier list every Quarter. The weird thing about this rating system is a company may drop down to Tier 2 if they fail to spend the right amount on R&D but jump back up again the next quarter if they do, so it’s perfectly feasible to buy a Tier 1 panel that becomes Tier 2 a few months later. And vice versa. So while the Tier rating system isn’t perfect, at least there is one, right? From your perspective, when being harassed by an over enthusiastic solar sales person, go to point d in the previous paragraph. If your sales person cannot name the solar panel company’s Head Office here in Australia, politely show them the door.
Watts per panel: As panel manufacturers jostle for greater market share, we are seeing higher wattage panels being offered. Over the last few years panels have gone from 250 to 275, 280, 300, 330, 350 up to 500w per panel! Watt, I mean, what this means is you can install a larger system on your roof using fewer panels. A 5kW system with as few as 10 panels. These larger wattage panels are usually larger in size, however, so make sure your friendly solar installer has measured your roof correctly and taken into account the heavier weight of these larger panels. Generally, panels between 300 to 350 watts are ideal for residential applications.
Mono vs Poly: This is short for monocrystalline vs polycrystalline. Monocrystalline panels have rounded edges which have been cut during production to optimize performance while polycrystalline modules look perfectly rectangular so you can easily identify them by their appearance. In terms of colour, mono cells are mostly dark and poly module have a bluish finish. When comparing panels of the same rated power output, there is currently no practicable difference in the performance of these two technologies. The only difference worth knowing is that if you are dead set on buying the highest efficiency panel on the market, the most expensive, highest watt panels are monocrystalline. But the only advantage of a more efficient solar panel is that you can get more watts on your roof. If you can fit the system size you need on your roof with more affordable, less efficient panels, then there is no difference between mono and poly.
PERC: This anagram stands for Passivated Emitter and Rear Cell or Passivated Emitter and Rear Contact and is a new technology aimed to achieve higher energy conversion efficiency by adding a dielectric passivation layer on the rear of the cell. What all that means is slightly more efficient panels at a higher price. You don’t need PERC tech for your home system but may want to consider it for your next utility scale solar farm out west of Mildura – the one with 230,000 panels.
Ok, so talk to me about inverters
All solar systems need an inverter. As mentioned earlier, that wild n crazy DC power that is generated on your roof needs to be tamed and calmed and converted into smooth and relaxed AC current that can be fed into your 240v power sockets scattered throughout your house. A traditional solar system uses panels and an inverter that connects to your switchboard and gives your home free clean energy while the sun is in the sky. Inverters range in size according to how much PV you have installed on your roof. The most common system size in residential Australia is 6.6/5, or 6.6kW of panels (say 20 x 330w panels) and a 5kW inverter. The bigger the PV array, the larger the inverter needed. It is worth noting that the Networks (the poles and wires companies) almost all have rules around how big a solar system you can install on your home. These rules are based around whether your house is single or three phase, the geography of the house and densities of existing PV in the network as well as other onerous requirements that appear from time to time. Once again, your friendly solar man should be across these rules and regulations as the install rules are different in each network (there are 16 independent networks across Australia, by the way).
Are all inverters the same?
Yeah, right. They all are supposed to perform the same function as mentioned above, but there is always the good/better/best scale, like with anything, really. Inverter manufacturers do not have a Tier rating system like solar panels do, so it’s best to do a bit of research before committing to an inverter brand for your next install. By the way, if your friendly solar sales person says they sell Tier 1 inverters, politely show them the door as they are lying to you. Generally, it’s important to look for the following:
- Look for a brand that has been around a bit, has modern manufacturing facilities and invests in research and development. Australia has lots of little quirks in its power grid, like voltage surge and inertia bumps, so a brand that has made a product for the Australian market is a better bet
- An inverter has a lot of parts within it and is tasked to perform in often extreme environments especially here in Australia. So stuff can go wrong. Look for a company that has a dedicated presence in Oz with a live support team in place, ideally here also. Your friendly solar retailer may not be around in 3-5 years so it’s vital you can get support and service from the inverter manufacturer should things go, heaven forbid, pear shaped.
- Make sure the brand is committed to quality. You can get a sense of this by looking for compliance to international quality standards like the ISO9000 family of quality standards.If the product you’re looking at isn’t made by an ISO9000 certified manufacturer, don’t use them. You should ask to see evidence of ISO certification from your friendly solar sales person. If they can’t produce one politely show them the door.
Add ons. Is the inverter smart? Does it have monitoring as standard, that meaning can it provide real data in real time to your device so you can measure your solar systems performance? The better inverter brands all have some kind of embedded monitoring functionality and frankly, who wouldn’t want to look at pretty little graphs on your phone at the end of another gloriously sunny free-energy-from-the-sun day?
What are micro inverters?
These things are great for a number of reasons.
Firstly, a bit of a background to the whole solar thingie. Roof top solar systems are laid out in lines or rows which are called arrays. If you see, say, 10 panels beside each other and another 10 below that, this is called a ‘string’ array. What that means is each solar panel is connected to each other with a DC cable that goes to the inverter, hence those 10 panels form a string. Now, what people don’t know about solar strings is that if just one of the panels is not working, the whole array’s performance drops by at least 50% because the string constitutes the system size or performance. Imagine a rowing team of eight plus a cox is needed for the Very Exciting Rowing Race. If rower number 3 is in shade, the whole team will drop by 50+%, regardless of whether the others team members are going sick to compensate. So, if one of your panels is in shade (shade is the enemy of solar), the systems performance will drop off a cliff. Example: shade from a chimney/tree/antenna. Here is another example of what you should be discussing with your friendly solar sales person. If you have really big trees shading your roof throughout the day, solar is a waste of time and money. Unless you want to cut ‘em all down which is expensive and the neighbours will hate you as well.
This is where micro inverters come in. Micro inverters are tiny little DC to AC inverters that are fitted directly underneath every single solar panel – so if you have 20 panels, you have 20 inverters.
The advantages are: each panel now works independently, so if one is in shade, the others will still work to their max, limiting lost generation. As well, micro inverters are a lot safer because that wild n crazy DC current has been tamed at each panel. Usually with string systems, the DC cable going to the inverter is running through the roof cavity for example, right next to insulation batts or old newspapers from the 50’s. If there is a power surge and the various connections in the solar array choose to arc, creating a spark…well Goodnight Irene.
In addition, micro inverters enhance greater efficiencies because the conversion from DC to AC is a lot shorter so very little power loss as compared with string arrays.
As well, if your roof is not ideally suited to a string array (eg multiple faces, some north facing some east/west etc, a solar system with micro inverters allows you to install virtually anywhere, as all panels will be working independently wherever they’ve been put.
In short, micro inverter PV systems are really roolly good BUT, they cost more…
Some solar guy said his inverter was “battery ready”. What does that mean?
Ok, so batteries have been the talk of the town for a few years now in the solar game. The reality is they are still way expensive and little understood. Go to our Battery School page to learn more about Batteries 101.
Anyhoo, if your friendly solar sales person says their inverter costs a little more but is “battery ready”, politely show them the door. All inverters are able to connect to batteries. Some inverters will only connect with some batteries. (brand marries brand to create monopoly – fail!). The reality is if you choose to install a quality solar system with a decent inverter brand, you will be able to connect a storage device in the future regardless. Do not pay more when the sales guy says just $500 more will secure your energy independence into the future by investing in ‘battery ready’ technology – that’s a crock. As battery storage becomes more common in the next few years, we’ll all get to experience the huge number of options already out there in the storage space and make quality decisions based on facts not fantasy.