RESIDENTIAL SOLAR OPTIONS
A Grid-Tie solution is the simplest (and cheapest) solar solution of introduce saving on your electrical bill. The solution consists of a grid inverter and solar panels. The quantity of solar panels will determine the amount of savings the solution will render, and the grid inverter needs to be the correct size to convert the solar electricity (direct current) from the solar panels to be available in your house.
A grid-tie does not incorporate any batteries and therefore does not offer any backup power. While the sun is shining on the solar panels, electricity is harvested from the sun and routed to your house for direct consumption in parallel with the utility grid (Eskom). When the sun sets the utility grid is the only possible supply of power to your house. Also, more important, even during the day when the sun is shining on the solar panels, and the utility grid (Eskom) fails, the solar system also shuts down. This is a safety precaution and system limitation that cannot be circumvented.
A grid-tie system does not offer any backup power or energy, but only introduces saving on your monthly utility electricity bill.
We prefer designing grid-tie solutions around an SMA grid inverter which is rich in functionality, including Internet online monitoring, integrated Grid Management Services and DC Isolators. It is a cost effective and super-efficient device sold with a standard 5-year warranty (extendable to 25 years). The SMA grid inverters (Sunnyboy or Sunny Tripower) can be integrated with other SMA or Victron products, with batteries, to offer very smart backup (hybrid) solutions.
A UPS on the other hand, is a simple solution which offers electrical backup power for limited duration, but does not offer any saving. The duration of the backup electricity supply depends on the size of the battery and the load placed on the battery. An inverter is used to convert the energy stored in the battery (Direct Current) to usable alternating current in your house. The battery is charged while the electrical utility grid is available, through the inverter/charger. This stored energy in the battery is then available for the inverter to automatically convert and start powering connected loads (lights, TV fridge etc).
The size of the inverter determines what appliances can be powered simultaneously, and the capacity of the battery defines how long the connected loads (lights, TV fridge etc) will be able to operate before the battery need to be charged again.
A UPS does not introduce or offer any saving, but is only a solution to keep the lights on, when the grid utility supply is off.
Hybrid solutions offer both the functions of a UPS and a Grid-tie solution. It incorporates solar panels, a battery and one or more inverters to offer backup power when the utility grid is off, as well as introducing savings on you monthly electricity bill. It is also a more independent solution, as the solar panels can charge a depleted battery on a sunny day, meaning you are not dependent on the utility grid to re-charge your battery.
If the solution is well designed, then the solar panels will be able to power the connected loads in your house during the day, but at the same time re-charge the battery if it was depleted the previous night.
A hybrid inverter is a single unit, typically a low-specification budget product, to offer backup power during utility grid failures, but also manages solar panels to introduce savings. Hybrid inverters are usually grid interactive, meaning that it interacts with the Eskom grid which can charge the battery or supply the connected loads if the sun-energy is not sufficient and the battery is depleted. Some can reverse the direction of the energy flow to feed possible excess sun-energy back to the grid.
A more durable, reliable, and efficient hybrid solution will either be and AC-Coupled solution (typically SMA) or a DC-Coupled system (typically Victron). Both these solutions offer the same functionality, albeit in different ways. There are situations where one is better, but then in other areas the other is better. A very smart solution will deploy both DC- and AC-Coupled components to reap the benefit of both the technologies.
SMA AC Coupled Solution
SMA is a top-quality product designed in Germany and offers a standard 5-year warranty. The warranty can be extended to 15, 20 or 25 years.
The Flexible Storage System (FSS) is an ‘Smart Home’ solution offering advanced energy management options and the Home Manager (part of the FSS) is capable of remotely controlling devices and wall plugs to optimise energy management.
The FSS is a bi-directional AC-Coupled solution which can be used for on-grid (Grid Interactive) solutions with- or without Battery Backup and with- or without Seasonal Self Consumption optimisation.
The FSS manages the energy harvest from solar panels, charging a battery from solar- or Eskom power and inverts DC power from solar panels and/or a battery to supply connected AC loads.
The Sunny Island 8.0H inverter is rated at 6kW AC power, but can power a load of 8/9.1/11 kW for 30min/5min/3sec respectively. Coupled with an SMA SunnyBoy it can accommodate up to 12kWp of solar power.
The Sunny Island 6.0H inverter is rated at 4.6kW AC power, but can power a load of 6/6.8/11 kW for 30min/5min/3sec respectively. Coupled with an SMA SunnyBoy it can accommodate up to 9.2kWp of solar power.
The smaller Sunny Island 4.4M rated at 3.3kW is also available, but can power a load of 4.4/4.6/5.5 kW for 30min/5min/3sec respectively. Coupled with an SMA SunnyBoy it can accommodate up to 4.6kWp of solar power.
Components can be paralleled with additional units to deploy a 3-phase solution.
Only when the Grid utility power is off, is the output power limited to the capacity of the inverter and is it necessary to use high power demand Items (kettle, microwave, hair dryer etc) with consideration.
Victron DC Coupled Solution
Victron is a leading manufacturer based in Holland. The configuration is described as a DC-Coupled Hybrid solution consisting of an intelligent interface (GX device), MPPT DC Charge Controller(s) and Battery Inverter/Charger(s). These are top-end quality products offering a standard 5-year warranty which can be extended to 10 years.
The battery inverter charger is capable of advanced management of energy and loads.
It is a grid interactive unit meaning that it interacts with the Eskom grid which can charge the battery or supply the connected loads if the sun-energy is not sufficient. It can reverse the direction of the energy flow to feed possible excess sun-energy back to the grid. This is a very useful feature that will maximise savings once “feeding power back into the grid” is allowed in your municipality.
The unit offers multiple advanced functions. It is a powerful true sine wave inverter, a sophisticated battery charger that features adaptive charge technology.
Off-Grid and Grid Independent
The term “Off Grid” is often used, but with differing interpretations. We understand “Off-Grid” to mean a facility with no connection to a utility power supply – the facility is dependent on the solar solution as the only source of energy and electrical power. The solution compensates for cloudy days, extended overcast periods or increased consumption (visitors etc) with extra solar panels and a larger battery than will usually be required.
We introduced the term “Grid independent”, which means a solution that can provide power and energy to the facility on an average sunny day, indefinitely. It does not compensate for cloudy days, extended overcast periods or increased consumption (visitors etc) with extra solar panel or over-size battery, bat a connection to the utility power supply (or generator) is retained to fill in shortfalls on “not-average” days.
Off-Grid solutions need to be significantly larger than Grid Independent solutions for the same implementation, as off-grid must cater for worst case days, i.e. short winter days or overcast summer days.