Inverters: what are Micro-Inverters?
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The electricity produced by a Solar PV array is DC and thus needs to be converted to AC before it can be used by the house or exported to the grid. This conversion process is done by an Inverter, and it is often one of the most expensive parts of a solar PV kit (often costing more than a single solar PV panel).
For a traditional solar PV array, they tend to use one inverter for the entire array, in what is called a “string inverter”. Here, the array is connected as a string of panels, with the electricity flowing through the entire string and finally to the inverter where it is transformed into AC electricity and passed to the house or grid:
Good quality Inverters can cost around £1,000 and have manufacturers guarantees of 5 to 10 years. They are typically seen as around 96% efficient and because of the DC to AC wiring required at installation, they are difficult to install and require a professional electrician.
However, the real problem with string inverter systems is that the performance of the array is dependent on any one single panel. Thus, if any panel becomes damaged, or is affected by shading issues, then all the panels are affected and the system performance is severely reduced. Additionally, string inverter arrays can only be monitored on the end system output, rather than monitoring each individual panel. Thus, if any one panel is being affected by shading, dirt or is broken, it is very difficult to tell which panel is causing the problem (its even difficult to recognise that there is a problem in the first place).
Is there a solution?
Yes. The solution comes in the form of “micro-inverters”. These are small inverters that connect to each panel at the source. Thus, you end up with an inverter per panel. Sounds expensive? Not really, as will be shown later
Micro Inverters have several advantages including:
- They allow each panel to be monitored individually thereby enabling you to maintain your system more easily and ensure that it is operating at its best throughout its lifetime.
- The enable the system to maximise the power generated from each panel, even if some panels are affected from shading.
- They tend have a longer life span than traditional string inverters. String inverters will generally need replacing during a solar PV systems lifespan, whilst micro inverters shouldn’t.
- They are easier to install as they do not require large DC to AC connection wiring.
Cost and Performance:
Let’s take a look at the cost/performance of Micro-Inverters using the Enecsys Micro Inverter:
A typical inverter for a 2kWp system will cost around £1,000 and has a high probability of needing replacing during the lifetime of the solar PV system. Thus, we can safely assume that the cost of a string inverter during the life of a solar PV system will be £2,000 in total.
The cost of one single micro-inverter from Enecsys is £200 (excluding cables and connection items). However, in a 2kWp system, we will have 10 panels and thus will need 10 inverters, bringing the total cost to £2,000. Thus, given the life expectancy of the Enecsys micro-inverter versus a more traditional string inverter, the relative cost is the same.
However, there are other advantages:
- Micro inverters are cheaper to install as they require no dangerous DC to AC wiring
- Micro Inverters make the system cheaper to maintain as the system, and any problems, can be easily identified and rectified
- Micro inverters increase the performance of any system, especially those that are affected by shading. It is estimated that a Micro Inverter will increase the performance of any system by up to 20%.
For those that plan for the long term – micro-inverters are the way to go. The extra initial cost is well worth the price. Don’t believe all the retailers that say Solar PV are maintenance free – they are NOT. A system that is easy to monitor and maintain is essential.
To view more details or to purchase an Enecsys Micro Inverter please visit our online shop
