This article applies to
|Country||Australia & New Zealand|
Note: All solar PV systems should be designed and installed by CEC accredited designer and installer.
What is a Solar System?
A Solar System is a power generating device that captures and transforms the energy of sunlight into electricity so it can be used to power appliances at our house. It normally contains the following essential components:
1. Solar Panels: This is considered to be the biggest part of the cost of a solar system. They are the power generating part of the system and they produce DC (Direct Current).
2. Inverter: The inverter is a very important part of the solar system as it determines how much AC power can be supplied to your house, along with your panels. The inverter is not a power generating device, but its function is to convert the DC from Solar Panels to AC (Alternate Current), which all our home appliances rely on.
3. Mounting structure: The mounting structure is the backbone of a Solar System because they help secure the modules to the rooftop and provide support to them.
Note: You will also need a battery and a generator if you are living in an off-grid area.
How does a Solar System work?
First of all, think of electricity current as water flow. In order for the water to flow from one location to another, you need to have potential difference, which means a higher and a lower ground. Same thing with power and electricity, and the solar panels on your roof are the device that create that potential.
Your solar panels are made of semi-conductors, which means they are sleeping electrons that lack energy to move around and are waiting to be awakened. When sunlight hits your panels, the heat wakes up the electrons as it gives them power to move around. This forms a Direct Current (DC), which can't be used at our house yet because all appliances use AC, which is Alternate Current.
Your inverter is here to convert DC to AC. The circuits inside the inverter help achieve that and also help feed excess power from your solar system back to the grid.
You can also consider including a battery to consume power, if no one is home during the day. You can then store the excess power that was going to the grid, in the battery. This would greatly increase your self-consumption rate, meaning you don't reply on the grid as much as before.
What makes an efficient Solar System?
First of all, you need to have the right system size that not only meets your current energy needs, but will also cover for the future if you plan to have more electrical appliances, e.g. changing the gas cooktop to an electric one, or if you consider a battery system for the house in future. The system design should be done by your solar company but here's what you can do as the property owner: start thinking about what is the right size for you.
You can do a quick energy audit by thinking about what are the most commonly used appliances at your house and do a quick calculation. For an example, between 7am to 7pm(total 12 hours) , the total energy consumption is:
Fridge(100W x 12hrs) + Air conditioner(1KW x 3 hrs) + Laptop(50W x 5hrs) + TV(60W x 2hrs) + Lighting(100W x 2hrs) = 4.77kWh
So your daily (daytime) energy consumption is 4.77kWh, then divided by 4, which is the average sun lighting hours in Australia - 4.77/4=1.19 KW
Therefore a 1.2KW solar system would cover your daytime energy needs. (Remember a Solar System can only cover daytime energy needs). Again, this is just a rough example, you can also refer to your electricity bill to get the exact daily energy usage.
Secondly, the DC-to-AC ratio needs to be around 1.25kW. What is DC-to-AC ratio? It is a ratio of how much DC capacity (the total power of your solar panels on the roof, e.g. 6kW) can be fed into the inverter's AC power rating (for e.g. a 5kW inverter).
Many tests are done to find out what the best ratio is to give the best performance, because you don't want to over-size or under-size your inverter too much. As a result, the system with a 1.25 DC/AC ratio has total power losses of 0.6% for commercial arrays, and 0.1% for residential arrays.
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