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Solar Systems:
Q1: Advantage of Grid Tie systems
A1: 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.
Q2: Can I feed back into the Grid and what benefit does it really offer
A2: Some municipalities do allow you to feed back into the Grid – although it is quite a bureaucratic process! For domestic users there is no limit at present as to how much you can feed back in (dependant on municipal district); but for businesses you are limited to your average monthly consumption over the past 12 months. You will get around 45c per kWh from your electricity supplier - which is currently cheaper than cycling a battery bank for reserve power.
Q3: What do you need to know in order to quote for a solar system
A3: Every solar system is different, from our experience. In order to size up an applicable PV array, Inverter and battery bank, we need to know: Your estimated peak consumption (a typical winter and summer month); Your daily, or monthly, consumption; as well as the make-up of your appliances you wish to operate. We usually start by attempting to reduce your consumption with energy-efficient lights and appliances, before we attempt to solarise any system
Q4: Is it best to go completely Off-Grid
A4: 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.
Q5: Can I build up my solar system in phases
A5: 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.
Q6: Can you have a solar system just for back-up
A6: You can, but it is not recommended if you do not employ the PV yield on a daily basis. If you have a battery bank, then you can opt to cycle it down to, say, only 20% 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.
Q7: What does the latest Victron ESS software system really offer me
A7: The ESS software is designed to optimise your PV yield by taking any surplus power not employed for charging the battery bank, or the system-connected appliances, and diverting this surplus to power other appliances outside of the dedicated solar system by diverting such surplus power to other circuits in the DB board that are not wired on the output of the inverter.
Q8: What is meant by a Pre-Solar Backup system
A8: A pre solar Backup System refers to the implementation of a Solar Inverter coupled to solar batteries and used for back-up power. The advantage of this system is that by adding panels and a solar regulator at a laterstage, the user has a full solar system with the use of all solar components whenever he chooses.
Q9: Are solar roof tiles (like Tesla’s offering) worth considering
A9: These products are quite new to the solar market and are being promoted in the USA where subsidies for solar are quite prevalent. It will be some time before we see them in SA with our cheaper electricity prices (at present!) and where these systems will be more expensive than they would be in their country of origin. Both of these factors would negate the cost-effectiveness of the systems in S.A. So the jury is still out on these novel offerings from Tesla and other companies with similar products.
Q10: How long does the modern solar panel last
A10: 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.
Q11: Can one rent a solar system: Yes there are systems that are rent to own based!
A11: There may be some companies renting some smaller solar system which are mobile, but I know of none. In Europe there is a market for people wishing to rent out roof space to companies who will split the profits of such systems which feed back into the grid obviously.
Q12: How does a solar system pay for itself:
A12: There are many different models for justifying solar systems. One needs to take into account that the rewards of Solar are not measured over a few weeks or months, but rather a period spanning a few years. Battery based systems will always take a few years more than Grid-tied systems for the ROI to pay off. The most important factor is that it has a definite value, which is added to the value of the house. We recommend taking 75% of the pre VAT price of any system, and ‘capitalising’ that onto the value of your home or building. You can depreciate this ‘investment’ over say 25 years and work back your ROI. Most serious investors acknowledge that solar gives a better return than the Stock and Bond markets. Of course, as Eskom prices climb (and they will, increasingly, after they privatise!) so the value increases.