One of the biggest sale persons around moved into South Africa recently. In Solar PV Systems, that person is called: “Sir Eskom Loadshedding!”

“Phone and web site enquiries have escalated somewhat since the start of loadshedding,” says Alan Straton from Straton Solar. “Everyone wants to be free of Eskom and loadshedding and most are of the impression that Solar Power is the magic bullet to do that.”

The price of Solar Panels has plummeted over the last eight years and the electricity price per unit (Kw) manufactured from a pure grid tie solar installation is now less than 70c per unit amortised over the 20-year life expectancy of an installation.

On the other hand, the price of batteries still needs to reach that tipping point before beginning to plummet. “Batteries are the next frontier in terms of lower price and higher storage capacity,” says Straton.

Solar PV “flavours”

Grid tie with battery backup refers to a hybrid system which will not be affected by load shedding depending on the size of the batteries. Off Grid is completely independent with no connection to the grid.

Taking the Nelson Mandela Bay Municipality as an example, Straton notes: “A grid tie system for a single-phase installation may only be a maximum of five KW in size. This is good enough for an annual average of 960 units of electricity each month (more in summer, less in winter).

“The pay back on such a system is around six to seven years. If the system is installed in a business, the payback is from the time of switching on as Section 12B of the Income Tax allows an immediate 100 percent depreciation allowance on renewable energy installation. If you do not have mission critical items then Grid Tie only is the way to go.”

He continues: “A hybrid system also operates under the same constraints as the pure grid tie system mentioned above. In addition, one must remember when buying batteries for your system that you are buying cycles. Much like buying five litres of petrol for your generator, batteries have a finite life.”

Businesses in Nelson Mandela Bay on a three-phase supply may install far more than the five-kilowatt limit. Most businesses that have contracted Straton Solar to install a Solar System opted for a seven-kilowatt hybrid system to keep essential equipment running during loadshedding. They also added pure grid tie in various increasing increments of ten kilowatts.

Battery Choices

According to Straton three main battery types are available. Lead acid batteries can have a cycle life of 500 and are the cheapest option. Limitations are that a discharge of greater than 80 percent will severely curtail the life of the battery and that a full charge again takes 14 to 16 hours. Price per 200 AH ranges from R2 000 to R4 500.

Lithium ion has been popularised by the “sexy” Tesla Powerwall and comes with a ten-year warranty and 5 000 cycles. At the end of ten years, the Powerwall is said to retain 70 percent of its capacity. Lithium ion batteries are also available in less “sexy” forms and locally in South Africa. The price ranges from R40 000 to R85 000 for a five-kilowatt system.

“Making a bid for the title of ‘preferred battery’ is a zinc-bromide hybrid flow battery popularised by Australian company, Redflow. Their Zcell can deliver ten kilowatt hours (kWh) of stored energy each day. Redflow batteries can charge and discharge 100 percent of their energy capacity each day, avoiding the damage such performance causes traditional battery chemistries,” Straton explains.

Redflow batteries can also maintain their nominal storage capacity throughout their operating life, unlike lithium-based and lead-acid batteries which lose energy storage capacity with use. Redflow warrants its ZBM2 and ZCell zinc-bromine flow batteries for ten years or 36 500 kWh with an output of roughly 3 650 full cycles (whichever comes first).

When purchasing batteries, you must be aware that you are essentially buying fuel upfront. “With electric vehicles receiving huge focus from major manufacturers the price of batteries is sure to come down or stay at the same level for higher capacity and more cycles,” Straton adds.

Straton Solar gave some estimates for the cost of installation for the various solar system choices (end of 2018 prices):

Grid Tie

R17 0000 to R25 000 per KW. Factors affecting the price: Roof type and orientation, roof angle and pitch (ideally the angle should be equal to the latitude of the roof), number of panels required, type of panel required, shadow on the roof, inverter type and warranty, cable runs.

Hybrid

R23 000 to R38 000 per KW. Factors affecting the price: Variables with grid tie system, type of batteries, power required, cycles required, space available.

For a private home on single phase power requiring the maximum of a five-kilowatt system the price ranges from R85 000 to R190 000 depending on which variables apply and whether a pure grid tie or hybrid system is required.