Designing of a PV Solar system for your home or office is a very stressful process, because your rely almost entirely on the service provider to give your a system that will work for you. However most of the time the service providers are talking a technical language that you don’t understand.

There is a saying that there is no stupid question, but be honest nobody wants to sounds like they don’t know what you talking about. So what do we do, we just tell the service provider to design a system for you. The end results is that you will always wonder if your will get what you paid for. Or if you paid for too much.

As a service provider that understand the PV Solar system industry better than the ordinary people on the street it is vital for us to ensure we provide you with the best deal.

 

We can design a system just based on your utility bill. By just looking at you historic energy demand to design a system. Mostly because of our experience from previous projects similar to your energy demand, and the understanding of the technical parameters of a system.

                 

We will usually design a system with the following technical terms

• 3 kWp generating capacity, 5 kVA invertor and 7 kWh battery storage

Now what does that all mean and how am I sure it is correct. I will try to explain it by showing you 2 graphs of a energy demand from my home. Figure 1 (Energy demand over 24 hours) and Figure 2 (Historic Energy usage over a week) below

Figure 1 Energy demand over 24 hours

Figure 1 illustrates 2 important factors to me:

1) Base load (Constant minimum energy demand) is around 0.5 kW. It is mostly due to the Fridge that is running 24 hours of the day, and the demand of a fridge/ refrigerator is ~ 0.5 kW (Or 500 Watt). Your will notice that between 00h00 and 5h00 the demand is showing a pattern of small spikes, that is how the compressor of the fridge is auto start and stop as the fridge looses it heat/increase of temp.

2) Peak load (Max Energy demand for a short period) ~3 kW. That happens usually when high power consumer appliances like kettle, hair driers, geysers, micro waves and tumble driers are switch on.

The information above are used to size my invertor. In thus case a 3 kVA invertor would be able to handle the demand, but to be save we give you extra capacity for the days you put on a more stuff simultaneously.

The info also helped me to calculate the amount of energy you will require during the night when the sun is not shining. (0.5 kW X 12 hours = 6 kWh battery storage). I recommended a 7 kWh battery storage system, which will allow 1 nigh of energy. (Note: In case we have an few days with low solar energy from the sun the batteries would not last for the second day).

Now you understand 2 of the specifications I recommenced (5 kVA and the 7 kWh).

 

Figure 2 Historic Energy usage over a week

Figure 2 shows me the historic Energy usage over a few days of the week (Data for the other days was not available at time of the article)

I noted that the daily consumption is around 10 kWh per day. If I escalate it to 365 days a year = 3650 kWh.

In the Western Cape of SA we are extremely lucky that the Specific yield (kWh/kWp) is ~1700, just because of the location of SA. Most countries in Europe is ~1000 kWh/kWp).

This value allows me to calculate the PV solar generating capacity:

– 3650 / 1700 = 2.15 kWp. Allowing for extra capacity by recommending a 3 kWp system.

 

I hope that this explanation will make you understand the system a little better and that you will be able to ask that question with more confidence.