Solar PV overvoltage is not smart grid integration

In reality, the conditions are great, the technology is capable but the assets, i.e. in this case, residential rooftop solar are generally underperforming.

How do I know if my solar is underperforming? Accurate solar generation statistics will require the consideration of variables like orientation and geographical location. However, a 'seat of the pants', 'finger to the wind' estimation may be sufficient to warrant further investigation of potentially poor performing solar assets.

Data requirements

To make a comparison, you will need data from your own solar system. You can either:

• Get analytics figures from your inverter, or if you cant obtain data from your inverter for whatever reason then;
• Use billing data from your electricity retailer.

Ideally you can use both (to keep your retailer honest).

Run the numbers yourself against an online calculator like the one here. Good calculators will enable you to take the variables of system size, geography, seasonality, roof orientation etc. into account. However, for a 'seat of the pants', 'finger to the wind' estimation, average consumption data is enough.

The average daily solar production figure generated from calculator is the one we want to compare against the figure from the inverter or retailer. You may need to normalise figures from your inverter or billing data against the daily figure from the calculator. For example, if you only have data from your energy supplier then you will have to amortise the kWh solar generation figures to a daily average;

kWh/days in the billing period.

The problem

In my case, I have an SMA 5kW inverter. I know my solar system has been generating around 9kW on average per day over the 3-months of Autumn. Using the average figure from the link provided above I can see that my solar system is underperforming. But why?

In Australia, the combination of network constraints and lack of policy direction is resulting in poor remuneration for energy generation that is not consumed onsite. More information is covered in an article here. Commonly, and in my case, voltage issues on the network can cause your inverter to trip and cut you off from that sweet feed-in tariff cash money.

Ok so now what? How to know if your solar inverter is tripping and what can you do about it?

The first point of call is viewing error log data from the inverter. Check the error log for records. You don't need to be an analytics/tech guru to check the error log. A simple Google search for your inverter brand and coupled with the phrase 'view error' or similar will point you in the right direction. If errors exist you may have to look up a specific error code on the vendors website to describe the error message.

Secondly, you can view solar generation data on your analytics platform.

The telltale signs of over-voltage tripping your inverter:

The points in the above chart (in yellow) where the generation line hits zero, in the middle of the day are a telltale sign of over-voltage tripping your inverter. Even if there is no sun, solar will be generating something, it should never be zero!

If you cannot access the inverter error log or analytics you should seek advice from a solar specialist. They may be able to come and do some analysis on your setup.

The solution

If you determine that over-voltage may be an issue contact your solar installer or an electrician first and they can measure the voltage at your premises. In my case, average voltage was way high, 250+ on average over the tested period.

Next, contact your DNSP such as Essential Energy ASAP. They will schedule a time to check and log voltage over a set period. Possibly a week or so. If they deem there is too much voltage in your local network they may turn the voltage down at the transformer on your street.

Hope this is helpful to those who are experiencing poor generation and remuneration from solar assets. If you don't know how your solar is performing hopefully this article inspires you to take action and get some data from your system. Good decisions come from good information.

Final word

Australians have adopted solar with gusto and for good reason. Australia ranks among the world's top ten solar countries by capacity and ranks second on a watts per capita basis with 459 watts per capita to Germany with 548 watts per capita. Solar has great potential which is currently not being utilised in this country. We have the technological capability to enable smart grid integration of rooftop solar - A fleet of underutilised assets currently on our rooftops that could be coordinated in real-time to meet the requirements of the network to advance renewables, provide a better return on investment for asset owners and improve the energy network for all Australians.