Solar up under lockdown

Did Netherlands Covid-19 lockdowns affect the performance of solar systems

On March 15, the Dutch PM announced that “All schools, cafes, restaurants and sports clubs will be closed in the Netherlands to stop the spread of coronavirus.” 3 months of hard lock down that most of us would happily forget followed. As we find ourselves starting to emerge from a second lockdown and starting to see light at the end of the tunnel it’s a good time to go back and see if we can find some positives from a difficult time.

It is reasonably well established that the natural environment benefited from a reduction in human activity during lockdown periods across the globe. Two of the most known examples are the clearing of the canals in Venice (some say the return of birdlife was also a result, but any one who has been to St Mark’s square knows there are plenty of birds in Venice!) and the reduction in pollution over Wuhan.

But what about the more direct impact on solar systems in the Netherlands? The graph below shows a clear increase over the 5yr and 30yr averages for the lockdown periods.

Impact of Dutch lockdown on irradiance

Graph 1

Irradiance overview Netherlands

Graph 2

The irradiance levels in April and May increased on the 30yr average by 29% and 24% respectively. These values are at the extremes at what would be expected based on normal variation in weather conditions, but are theoretically possible. It is worth noting that the combined irradiance of April and May achieved in 2020 has not been exceeded since records began in 1983! Statistically these sunlight levels could be considered a 1 in 50 year event.

As the lockdown began to ease at the beginning of June the irradiance levels returned to their long term averages, which in our opinion provides further evidence that the lockdowns did in fact contributed to higher irradiance levels throughout the Netherlands.However, while the data certainly suggests a direct impact, the natural variability makes it difficult to conclusively state that this is caused by the lockdowns.

Irradiance variation is widely misunderstood and the effects on performance under-estimated.

Graph 2 shows that during the boom years of Netherlands solar, irradiance levels have consistently been above the long term averages.

When an expected yield is provided for a system in design phase a long term average of irradiance is used (more on P50 andP90 later). Over the past 5 years actual irradiance has been 10% above historic levels in the Netherlands, the logical expectation is that system performance should be over achieving the expected yields provided pre-build by 10%.

It is difficult to predict future trends in irradiance, clearer skies obviously have a positive impact, but there are also much larger climate and weather affects that influence these trends. A return to historic averages, or even lower, are very likely within the SDE timeline of projects being built. When this happens, we expect a lot of rooftop asset owners will discover their systems, they thought were doing well by meeting expectation are actually underperforming, and have been ever since installation. 

For larger ground mount systems and the largest industrial rooftops with owners who are solar professionals, pyronometers are used to measure on site irradiance and monitor relative performance, but these level of sophistication remains quite rare for the majority of SDE projects.

The Autarco way

At Autarco, all of our performance metrics are based on actual irradiance data that we receive in 15min intervals for all of Europe. Using the digital twin in Helios, this irradiance data is used to generate true expected values (or retrodicted for the nerds). This Delivers a true base line for performance (referred to as Energy Performance Index (EPI) and ensuring all our systems are generating at optimal levels. It’s just one more example of how we use the power of data and digitilisation to deliver on our promise; “Solar made simple. Performance made certain”

Arc fault detection and application

The risk of fire caused by solar systems is very low and in the vast majority of cases caused by low quality products or installer errors that lead to an electrical arc and then fire. The chance of a fire being caused by an arc in your solar system is comparable to the same risk carried by most electrical appliances such as a TV.

Despite this low risk, at Autarco we have taken all possible steps to reduce risk. As a total solutions brand, we are in position to control these risks far better than a brand that only produces one product like a solar panel manufacturer or solar inverter manufacturer.

Read on to find out more.

What is an Arc Fault?

An arc is formed by separating two parts of a circuit where a current is running. A plasma is formed between the 2 parts emitting light and heat. The plasma is a good conductor, so in other words the current will keep flowing and the arc will continue until one of below;

  • The voltage in the circuit is reduced to less than 12V
  • The distance between the 2 parts is closed
  • The distance between the 2 parts is increased far enough to break the arc

In a solar system, the rooftop current is a direct current which makes arcs more troublesome than in an AC circuit where the voltage goes to zero (50-60 times in one second, according to the grid frequency).

The large energy produced by arcs can be controlled in certain industrial applications such as welding and plasma cutting and they are also commonly used in lighting applications. If uncontrolled, the hot plasma may cause damage and will cause plastic parts to melt and potentially cause fire.

Possible causes of an arc in a solar system

There are numerous connection points in a solar system that are potential flash points for electrical arcs to occur. You can think of these points simply as switches and plugs.

Individual solar panels have connectors (plugs) on the end that are joined together. The ones that come on the solar panels are installed in highly automated production lines with stringent quality control. The installer just needs to make sure they hear a “click” when they connect the plugs and then the risk is incredibly low.

The connectors on the cable that connects the panels on the roof to the inverter on the ground are added by the installer and this introduces two risks;

  1. They use a different brand of connectors to those on the solar panels
  2.  They do not install the connectors properly.

As a total solution brand, Autarco uses approved dealers and provides all connectors of the same brand to our professional install partners.

Some form of DC switch is mandatory at the solar inverter, so the inverter can be safely disconnected from the solar panels for maintenance etc. Often referred to as a DC Switch or DC Isolator.

  • When an installer is not suitably trained or is trying to save costs they may install an external switch that is not suitable for the solar system which can result in arcs.
  • Beyond incorrect product choice, the connections in the external switch may also be poorly done. Autarco dealers and installers receive instructions how to install these switches properly.

Autarco inverters have an integrated DC switch, so they are always properly matched and installed under strict quality control.

External Causes
Animals chewing through wires can also lead to arcing. By proper separation of the DC-cables, propagation of the arc is prevented.


Prevention beats detection every time. That’s why we have deployed innovative technologies and processes in our total solutions to mitigate the three main causes of unsafe situations.

  • Product Quality
  • Design Safety
  • Install Quality

You can read more about this on our safety page.


In addition to our prevention measures, new Autarco inverters are now available with inbuilt Arc Fault Detection. This means that the inverter can detect an arc in line and will then shut down and send an alarm.

The detection in Autarco inverters conforms with UL1699B-2018, which is an American standard, but is currently the only available standard for arc fault detection in the world. As new standards (the European organisations are working on one now) become available, our inverters can be upgraded to comply with them.

There is still an additional risk: if the sun is shining there is always a voltage between the panels even if the inverter shuts down, so the arc may not be extinguished by inverter shutdown. By adding optimizers to each solar panel it is possible to reduce voltages of all panels on the roof to a safe value.

Read more about Autarco and safety

Interested? Get a free roof scan and follow up from one of our Authorized Dealers near you.

Interested in becoming an Autarco Authorized Dealer? Click here to learn more.

New process for system registration and monitoring setup

Recently Autarco made a significant improvement to its Helios software. From this moment on, registering a system and setting up the monitoring no longer takes place in MyAutarco, but directly in Helios. Therefore, all steps in the process from design to asset management are now in Helios. Information is automatically validated and fulfilled serial numbers are provided, to make the process from designing, quoting and registering PV-systems even more easy. The result of all this is the Digital Twin, an exact copy of the installed system, that forms the basis for our monitoring and asset management services.

Monitoring setup

On completing the monitoring setup, serial numbers for inverters and monitoring adapters are paired. With this, Autarco can collect monitoring data from the PV-systems, in order to analyze these and show them in MyAutarco. Also, a page in MyAutarco is created, that the end customer will get access to.

The following data is required in order to perform the monitoring setup:

  • End customer contact details;
  • Inverter(s) serial numbers;
  • Monitoring adapter(s) serial numbers.


On registering a system, you confirm that the system as designed in Helios exactly matches the real installation. Adding serial numbers and pictures completes the administration, that will be verified by Autarco. Once verified, the kWh guarantee can be issued.

In the registration process the following information needs to be confirmed and provided:

  • End customer contact details;
  • Installation address;
  • Layout;
  • Valid inverter selection and string plan;
  • Completed monitoring setup;
  • Solar panels serial numbers;
  • Pictures.

Important details regarding Tigo optimizers

Solar panels can’t always be installed with the ideal layout, sometimes shading of buildings and trees in the near vicinity can cause lower yield than expected. We supply optimizers from Tigo to reduce yield loss thanks to shade. This solution allows you to install an optimizer on either one or more solar panels per string. Visit the Tigo website for important recommendations regarding which combinations are possible and what to look out for when designing a PV layout.

More details on the Tigo website