Frequently Asked Questions
You have to define the capacity of the solar array that you need in kilowatts. Each solar panel generate between 300w- 650w each. So if you need to generate 5.4kw per hour, then you will look at 10 x 540w panels.
In a perfect off-grid system your panels must generate enough power to supply load to your house during the day and it must generate surplus to charge the batteries in order for you to have full batteries at sunset.
It is dictated by your peak consumption when more than one appliance or equipment are used at the same moment. We can also connect a logger to Distribution Board to record your usage over a period and to see what and when is your peak consumption.
An analysis of your equipment and the individual consumption can give us a basic indication of what your peak will be. We can also eliminate certain breaker circuits from the solar system if you want to reduce your inverter size.
It all depends on the outcome that you want. The rule of thumb is that your battery bank must last you throughout the night until sunrise when the photovoltaic panels started to generate power.
You can do a simple exercise to determine your night consumption in kilowatts (or units) by taking your meter readings at sunset and again at sunrise for a few nights.
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What you need to know about...
The effectiveness of your installation depends on the combination of the correct number and size of panels, the storage capacity of your battery bank and the choice of inverter-mppt-controller combination.
At Powerhour Solar we believe in the importance to determine and define your required outcome before you implement an installation and here are the important steps in the process that will result in an outcome that meets your expectations.
- Start by determining your monthly electricity usage in kilowatts and break it down in an average daily consumption. You could do that by recording your meter reading over a period or by checking the reading on your monthly municipal account. If you record your meter at sunrise and at sunset you can differentiate between sun light and night time consumption. By checking your consumption during the night, you know the size of battery bank you need.
- Determine which appliances are the major contributors to your consumption, such as geysers or stoves. Keep in mind that a single geyser use at least 3kW per hour and a stove can use from 1,2 to 1,5kW per hour. By installing a gas stove and or solar geyser you can reduce the size of your primary solar installation and your battery bank substantially. You can remove the non-essential items such as pumps, geysers and stoves, from the solar installation if you choose so.
- If you know now what is your required usage during night time, then you can determine the capacity of your battery bank in kilowatts, and if you know the load that your house draw during the day, you can determine the number and size of PV Panels that will produce sufficient energy to charge the batteries whilst taken into consideration that your appliances consume solar power and you charged your batteries during the day.
- Only after that you can determine the correct type and capacity of inverter.
What options are available in terms of batteries? You basically have a choice between a Deep Cycle battery bank or a Lithium-Ion Bank. A deep-cycle battery is a lead-acid battery designed to be regularly deeply discharged using most of its capacity. There is an indirect correlation between the depth of discharge (DOD) of the battery, and the number of charge and discharge cycles it can perform. A deep-cycle can discharge between 20% and 45% but the higher the discharge, the lesser the cycles.
Lithium-Ion Batteries is currently winning the race for the most popular choice in storing renewable energy. It is a rechargeable battery that allows for a discharge of 100%. You therefore use the full capacity of the battery whereas in the event of a deep-cycle battery you only use a portion of the batteries’ capacity.
Lead, which is the heaviest non-radioactive metal, has been the standard in batteries for decades. Why should you consider a lithium battery conversion? Here are seven features explaining the disparity between lead-acid and lithium-ion batteries.
1) Weight: Lithium-ion batteries are one-third the weight of lead acid batteries.
2) Efficiency: Lithium-ion batteries are nearly 100% efficient in both charge and discharge, allowing for the same amp hours both in and out. Lead acid batteries’ inefficiency leads to a loss of 15 amps while charging and rapid discharging drops voltage quickly and reduces the batteries’ capacity.
3) Discharge: Lithium-ion batteries are discharged 100% versus less than 40% for lead acid. Most lead acid batteries do not recommend more than 40% depth of discharge.
4) Cycle Life: Rechargeable lithium-ion batteries cycle 5000 times or more compared to just 400-500 cycles in lead acid. Cycle life is greatly affected by higher levels of discharge in lead acid, versus only slightly affected in lithium-ion batteries.
5) Voltage: Lithium-ion batteries maintain their voltage throughout the entire discharge cycle. This allows for greater and longer-lasting efficiency of electrical components. Lead acid voltage drops consistently throughout the discharge cycle.
6) Cost: Despite the higher upfront cost of lithium-ion batteries, the true cost of ownership is far less than lead acid when considering life span and performance.
7) Environmental Impact: Lithium-ion batteries are a much cleaner technology and are safer for the environment.
Though they are used to power the same applications, that is where the similarity between lithium-ion and lead acid batteries ends. Lithium batteries deliver higher-quality performance in a safer, longer-lasting package.
What is a Hybrid Inverter? it is an intelligent inverter which is a hybrid between the traditional on-grid inverter and off-grid inverters. The hybrid inverter synchronizes with your mains utility power as well as the solar power available in your battery bank.
The solar hybrid inverter will prioritize the input and will give preference to solar power, and then if the demand exceeds the solar power it will supplement it with Eskom power. If the solar power exceeds the power utilised during the day, the excess power will be channeled to the batteries. If the batteries are fully charged the excess power will be stored for usage during the night and if your Eskom connection is off, the inverter will rely solely on battery power. You could be independent from the grid if your usage does not exceed the stored capacity of your battery.
With a grid-tie installation there is no battery bank and your solar panels will generate electricity that will firstly be utilised by your electrical appliances, and the surplus power will be pushed back into the grid. When insufficient electricity is available, the inverter drawn from the mains grid to make up the shortfall. Conversely when excess electricity is available, it is sent to the mains grid. With a grid-tie installation you are still dependent on a reliable grid, and when the grid is off, your grid-tie inverter is also off.
The biggest advantage of a grid-tie connection is that you save on a battery bank which is a significant investment. The other side is of the coin is that when the grid is down or if you experience load shedding then your system is also down.