Solar FAQs

Safety

As my system will be inspected by an independent inspector, will it be safe?


No. An inspector only checks a narrow range of parameters. So, e.g. the inspector does not check that the rails were installed correctly, or the modules were installed to manufacturer's specifications and therefore warranty not lost; or that the clamps were not overtighted or the screws in the switches torqued correctly. This is all outside the inspector's work.

Maintenance

What maintenance does my solar photo-voltaic system require?

Cleaning off the dust. This will happen when it rains. Most solar photo-voltaic systems are installed on pitched roofs that will have an angle anywhere from 20 – 40 degrees. In some cases, where they are installed on a flat roof, they will be propped up using angle frames to give a suitable angle of about 37-odd degrees (for most of Australia). By virtue of this angle, the rain washes down the dust.

In addition an annual check up is recommended to ensure that all the fixings are secure and the panels performing optimally.

 

Bird droppings

Bird droppings, on the other hand, if left on the modules, can affect the performance of the modules. Good modules will have built-in diodes, however, even then, bird droppings should be cleaned out when convenient.

And don't build an antenna system near your modules else you'll provide a perch for birds and....

 

Mechanical and electrical fittings, switchgear

For optimal performance of your system, it is highly recommended that an annual check up is carried out by a qualified solar pv technician. Isolators and switches can often start to deteriorate over time and it is advisable to catch these in good time. In addtion a good clean up will ensure maximum power generation.

Metering

Will my smart meter have to be changed after installing a Solar System?

No. All smart meters, by regulation, should be re-configurable, remotely, at little extra cost, to capture data relating to energy exported from your solar photo-voltaic plant.

 

What is a solar-meter?

This is a loose term used to describe any meter that is capable of capturing information relating to power that is fed back onto the grid. Another term often used is "bi-directional meter". And, technically speaking, a smart meter, too is capable of being a "solar meter".

 

How often is the grid-feed metering netted off?

Every half-an-hour.

 

How can I establish if my "solar meter" or smart meter is recording my solar energy correctly?

All meters have certain fields which will display the amount of energy fed back onto the grid; most will also show this broken down between weekday export and weekend export.

  • Field Nr. 13 shows the total
  • Field Nr. 14 shows weekday export, and
  • Field Nr. 16 shows weekend export.





Sizing

What is the ideal size of system for my home?

This depends upon a number of factors: from your current usage, to the patterns of usage, and your expectations out of the system. Typically grid-tied systems (which are the most common ones dotting our urban landscape) are based on the day-time usage. The idea is to generate enough power during the day to meet your requirements and leave a healthy surplus which can be fed back onto the grid and earn you the 60c-plus/kWh.

Or, if you are on the more current 8c-plus/kWh feed-in tariff, then the idea would be to use as much of the energy domestically (also known as "self consumption") as possible. Perhaps in such a case, explore facing the system to the west and east or just west instead of north.

Much as we would like to stick a formula out on the web, we realise that the matter is a little more complex and so prefer to have a direct talk with the prospective customer to fully understand his/her unique requirements and load patterns.

But, here are a few clues:

- your system will produce an average of 3.6 x size in kW per day. I.e. a 2kW system should generate about 7.2kWh/day through the year. Facing west the system would loose about 12%, but gain the possibility of saving almost four times more in energy costs (i.e. saving at about 30c/kWh instead of earning 8c/kWh.

Once all the workings are done, you need to assess your roof, to establish if it is viable (azimuth- and shade-wise), etc.

 

Technical

What is the difference between magnetic north and solar north (or True North)?

Magnetic north is based on the magnetic field of the Earth, which is not necessarily the same as the Sun's position relative to the Earth.

In Melbourne, Solar North (or true north) is about 11.6 degrees to the west of Magnetic North (N 011.6 W as expressed as a Conventional Compass Bearing or 348.4 deg. true - as expressed as a True Bearing). Or, looked at another way, we could say that the Magnetic North is 011.6 degrees' east of True North, written as 011.6 deg. true.

This changes location to location in Australia. A solar photo-voltaic system is designed to be orientated to Solar North and not magnetic North.

Such considerations become especially important when assessing the impact of shade from a tree or structure on the PV plant.

 

Can I have a battery back-up to my grid-connect system?

Yes. A careful analysis would have to be done of the equipment you’d like to run in the event of a power failure. Based on this information a battery back-up system can be designed to work hand-in-hand with your grid-connect photo-voltaic system. However, more often than not, the costs would outweigh the benefits, and a simple Uninterrupted Power Supply Unit would suffice.

 

How important is quality DC cable?

Very. Research has shown that using cable specifically designed for solar application improves reliabiliy. Some technologies of cable manufacture are far better than others; take RADOX solar cables, according to IEC 216, they have a lifetime of 8 times longer than rubber and 32 times longer than PVC cables. RADOX is specifically designed for use in severe conditions assuring an installation of optimal yield for its entire lifetime.

 

 

 

 



Mono, Poly, or Amorphous?

Aren't monocrystalline modules the best?

No!

What is best is what gives the highest yield and that depends on other factors.

The essential difference between mono, poly, and amorphous is the amount of space that it takes to generate a given amount of power.

Mono, being the most efficient will typically take about 3 - 4% less space than poly; and about 50 -60% less space than amorphous.

However, this does not mean that mono will generate more power per watt installed. Power generated per watt installed (better known as yield) depends upon numerous issues including the quality of Silicon and other materials used, temperature coefficients (i.e. how badly a cell or a particular technology responds to heat), performance under low-light conditions, etc.

And this is where quality poly comes into its own: for the past several years, poly modules (e.g. those from SolarWorld AG) have performed outstandingly well in independent lab tests, from those at Photon Lab in Germany to the Desert Knowledge in Australia, generating higher yields than other technologies including mono.

 

Will my modules cause reflection in the sky?

Hardly. Most good-quality modules are designed to absorb as much of the light as possible. This is achieved through an anti-glare coating and the use of textured glass. Hence there is very little reflection.

Good news for the pilots; and airborne insects that like to lay their eggs on water surfaces, and may mistake an array of modules for water – something that has been known to happen if the module reflects too much light!

 

Is heat good for my modules?

No. The hotter the modules get, the poorer their performance. When comparing modules have a look at their “normal operating temperature”. The higher it is, the better will be the overall performance of the module.

And the lower the temperature coefficient the less will be the loss in power with temperature change.

So, for instance, if a house has equally good NE and NW faces, pick the NE as it will generally be cooler in the mornings....

 

What about hail protection?

Qualtiy modules will carry IEC 61215 certification. To attain this qualification the modules would have to be subjected to various tests including hail impact: a 25mm diameter ice ball travelling at 23 meters/second, directed at 11 impact points.

Some module manufacturers such as Solon and SolarWorld have a thicker front tempered glass (4mm instead of 3.2mm) and hence offer slightly better hail protection.

 

 

 

 

 

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