Well, the jury is still out on this question. Some older panels have moved past 30 years and are still giving over 50% of their specifications. Modern panels are guaranteed to give some 85% of optimal after 20-25 years depending upon manufacturer.
Grid tie systems are most popular with businesses, or houses, where most of the power is consumed during the day and where a battery bank is therefore not a major factor. If the PV system can also feed back into the Grid by acquiring ‘Credit’ from your electricity supplier; then, especially with businesses that don’t work over weekends, you will be able to utilise ALL the PV yield that your array can supply – making it very efficient and cost-effective.
Some municipalities do allow you to feed back into the Grid – although it is quite a bureaucratic process!
You are only allowed to feed back a certain percentage of your daily generation and you need to pay a surcharge in order to do so. It varies from Municipality to Municipality, some areas charge R400 per month to feed power back into the grid.
This depends upon your circumstances and can cost hundreds of thousands, due to the large battery bank required, but most people already connected to Mains usually stay connected and the solar system usually represents between 20-80% of their total consumption. If you are already Off-Grid and employing a Genset, then obviously it is better to get all your power from the PV array and only employ the Genset in case of inclement weather and emergencies.
Modern solar systems are designed to be scalable so you can start small and expand without making any major component redundant. The exception to this is the battery bank which, as a rule of thumb, you should not mix – if the batteries differ in age by more than 6 months.
You can, but it is not recommended if you are not going to utilise the PV yield on a daily basis. If you have a battery bank, then you can opt to cycle it down to, say, only 80% overnight, thus leaving you with ample reserve in the event of a power-out that occurs after solar charging hours. The main aspect is to ensure that you are employing your PV yield optimally on a daily basis.
It depends how often it rains in your neck-of-the-woods, as well as how dusty an environment your PV array is subjected to. They should ideally be cleaned at least twice a month by you, or by nature. Use only fresh water with no detergents – spraying with a garden hose is quite adequate as a rule.
Again this depends upon the location of your site. As a rule-of-thumb for Gauteng area we use a figure of 1000W per hour, per square meter – although it can be slightly higher.
A great deal! Just because your panel is only shaded by say 10%, you could easily be losing up to 80% of your potential yield. (It is much less with thin film panels). Winter shading is a big issue for many solar systems installed in the summer and where the installer did not allow for a drop in the angle of the sun in winter. Obstruction such as neighbouring buildings, masts, turrets, high trees, etc. can all lead to shading and a reduction in PV yield.
This is a definite ‘No-No’ and will lead to issues regarding the charging requirements for the different batteries. Avoid this at all costs!