Understandably, most people do not have in-depth knowledge of the various system options and the very first step we take when doing a consultation (after confirming the primary objective of our potential client) is to give them a basic overview of the types of solar systems out there.
The section below gives an overview of the most popular system configurations today. It is not a detailed analysis of the various system types, but should help most people to decide which system will meet their needs.
This is our most popular system for residential customers. This system gives you the freedom of being off grid, but because you have a grid connection available, you do not have to have a big battery bank to get you through days with no or little sunshine.
In other words, the significant expense you have to go to in order to make provision for 3-5% of the time of poor weather in a total off grid system is avoided.
As battery storage becomes better and more cost effective, the battery capacity can be increased over time to move to a total off grid scenario.
The biggest advantage of this system is that you are protected against power outages, while you are saving on electricity. The downside is that the system is more expensive than a normal grid tied system due to the batteries and the more expensive battery to AC inverter.
The MPPT solar charger provides power to the inverter and charges the battery bank.
The inverter is programmed to use battery and solar power to power the house / office.
Should the battery voltage drop below a set value, the inverter will seamlessly switch to grid power, protecting the batteries from discharging further.
It is important to design the system so that the PV panels, the batteries and the loads are well balanced to ensure that the system only goes to grid power in poor weather conditions or exceptionally high use of electricity (outside the usage the system was designed for).
Ironically it is batteries, and not inverters or solar panels or charge controllers etc. where the biggest mistakes are made in solar system design and installations. In off grid solar systems, batteries are normally the most costly component of the system, yet not many people realise the enormous pitfalls there are in selecting the correct battery type for the application and conditions (such as ventilation, temperature, charge and discharge times and peak current requirements to name a few).
We have invested countless hours studying batteries and still spend hours weekly reading up and contacting manufactures and peers in the industry in order to give our customers the correct advice on battery choice.
This is a very complex topic and there are good resources available online to educate yourself, but be warned, prepare to spend quite a few hours and then go back for more studying, as new questions will emerge as you start delving into the battery world. One such good resource is www.batteryuniversity.com. The fact that a site like this even exists is an indication that this is a minefield to be negotiated carefully.
This is also where the biggest advances are happening at the moment, and we are (in South Africa at least) seeing very interesting developments in Lithium battery solutions, specifically targeted at the residential and commercial solar energy and backup power market. The key is to find a battery manufacturer that is trustworthy and backs up their warranty. We have found such a supplier and is very proud to be associated with their product.
What makes the modern Lithium battery landscape very interesting is that we are able to offer the technology at prices better than lead acid over the life of the battery. In other words, for the energy stored and extracted for as long as the battery lasts, Lithium beats lead acid. This is major news, because the price of Lithium has the potential to fall by a large margin in the coming years where lead acid costs are actually going up.
This means that the cost of being able to produce, store and consume your own solar power will be cheaper than Eskom in the not to distant future (our estimate is 1 – 2 years for consumers currently paying close to R2 / kWh).