Solar Voltage Rise – why you should care

Solar power is becoming increasingly popular as the world continues to shift towards green, renewable energy sources. Solar panels are being installed on rooftops, in fields, and even on the sides of buildings. This surge in solar power usage has led to a new phenomenon known as “solar voltage rise”. In this article, we will explore what solar voltage rise is, why you should care about it, and how to prevent it.

The trend towards solar energy is not only environmentally friendly but also economically beneficial. As solar technology advances, the efficiency of solar panels improves, making solar investments more attractive However, as adoption rates increase, certain challenges emerge. Solar voltage rise is one such technical challenge that can affect the performance and safety of solar power systems.

What is Solar Voltage Rise?

Solar voltage rise, also known as “solar voltage spike” or “solar overvoltage”, is a temporary increase in the voltage output of solar panels. This increase can occur during periods of high sunlight, or when there is a sudden decrease in cloud cover. The increase in voltage can be significant, ranging from a few volts to over 100 volts. This spike in voltage can cause damage to solar panels, inverters, and other components of the solar power system.

Why Does Solar Voltage Rise Occur?

Solar voltage rise occurs because solar panels are designed to operate at a specific voltage. When there is an increase in sunlight, the panels are able to produce more electricity, which leads to an increase in voltage. This voltage spike can occur even if the panels are not connected to a grid or a battery. It is a natural occurrence in solar panels and is not always a cause for concern.

The underlying physics of photovoltaic cells in solar panels is such that they convert light into electricity. When exposed to more light, they generate more electricity, which in turn increases the voltage. This is because the voltage of a solar panel is directly related to the intensity of the sunlight it receives. If the intensity increases suddenly, such as after a passing cloud, the voltage can rise quickly before the system has time to adjust.

However, if the voltage rise is significant and sustained, it can cause damage to the solar panels and other components of the solar power system. This is why it is important to monitor and regulate the voltage output of solar panels. Excessive voltage can stress the electrical insulation and connections, leading to potential failures or even fires if not properly managed.

Why Should You Care About Solar, Voltage Rise?

As an owner of solar panels, it’s important to be mindful of solar voltage rise for several reasons:

Safety: A significant voltage increase can be hazardous, particularly if you’re working on or near the solar panels. It poses risks to nearby electrical equipment and structures, including the potential for electric shocks and fire hazards due to electrical malfunctions.

Equipment Damage: As noted, a prolonged voltage rise can harm solar panels, inverters, and other solar power system components, leading to expensive repairs or replacements. While damage might not be immediately apparent, it can gradually impair the system’s performance and dependability.

Efficiency: A solar voltage rise can compromise your solar panels’ efficiency. Excessive voltage output may cause the panels to shut down or perform poorly, diminishing the energy they generate. An efficient system is crucial for maximizing investment returns and ensuring consistent electricity production.

• Longevity: Frequent voltage spikes can reduce the lifespan of your solar panels and associated equipment, necessitating more regular replacements and incurring additional costs. Shielding your system from voltage rise is cost-effective over time and helps maintain your commitment to a sustainable future.

Preventing Solar Voltage Rise

 To prevent solar voltage rise and safeguard your solar power system, you can implement the following key strategies:

1. Install a Voltage Regulator: A voltage regulator is a device that monitors and adjusts the voltage output of solar panels. It helps prevent voltage spikes and protects your equipment by ensuring that the voltage remains within a safe range.
2. Install a Battery Storage System: Batteries can help regulate the voltage output of solar panels by storing excess energy and releasing it when needed. They act as a buffer, absorbing sudden spikes in voltage and providing a stable output to the grid or your home.
3. Use Micro-Inverters: Instead of having one large inverter for your entire solar power system, micro-inverters can be installed on each individual panel. This allows for more precise control of voltage and can help prevent spikes. Each panel operates independently, reducing the overall risk of voltage rise affecting the entire system.
4. Perform Regular Maintenance: Regularly inspect and maintain your solar panels and other equipment to ensure they are functioning properly. This helps identify any issues with voltage output and prevents damage. Regular maintenance includes cleaning the panels, checking connections, and ensuring all components are in good working order.

 5.Install your inverter near your Switchboard

To minimize solar voltage rise, we always try to minimize the length and increase the size of the cable between your switchboard and your inverter. Compare the two scenarios:

1. Installing a 5kW inverter 5 meters away from your switchboard. A voltage rise calculation shows a 0.3 per cent voltage rise when we use our standard 6mm2 cable.
2. Install the same 5kW inverter 25 meters away. Increase your cable to 10mm2. Your voltage rise issue would increase to 0.9 per cent.
3. Installing your inverter further away from your main switchboard means your material cost goes up, your labor cost goes up, and your solar voltage rise goes up.

6.Increase your cable size

• 5kW inverter can produce up to 21 amps. While a 2.5mm² cable is sufficient for 21 amps and is commonly used in Australian homes, solar voltage rise calculations often lead electricians to opt for a minimum of 4mm² cable to maintain a voltage rise under 2%, minimizing voltage drop is a priority. That’s why we use a 6mm² cable as the standard for a 5kW single-phase inverter. If the inverter is far from the switchboard and the voltage rise nears 2%, we’ll install parallel 6mm² cables to ensure reliability.

Correctly program volt response modes

The 2015 revision of the Australian standards for solar inverters (AS/NZS 4777.2) introduced several grid support functions to mitigate the overvoltage issues caused by solar power. Although some of these functions were merely suggested, nearly all inverter manufacturers I reached out to had adopted the recommended settings.

• However, the issue arises with the preset values, which act as a severe limitation on your solar system’s performance. It’s crucial for your installer to adjust these settings. The volt-response settings vary slightly among Electricity Distributors. The following example illustrates the standard preset values versus the more accommodating values allowed by Energex and Ergon (Qld). If your electrician is not knowledgeable about the proper voltage settings and leaves your inverter at its preset values, your inverter will prematurely hit the overvoltage threshold.

 7.Use a three-phase inverter

Installing a 3-phase inverter is one solution. This type of inverter divides the current across three separate cables, meaning that instead of pushing 21 amps through a single cable to the grid, it sends 7 amps through each of the three cables. According to Ohm’s law, reducing the current also proportionally lowers the solar voltage rise.

Upgrading an older home to 3-phase can be cost-prohibitive. However, if 3-phase power is already available in your home, investing in a 3-phase solar inverter is advisable. For new constructions, adding 3-phase power during the build is not significantly more expensive. (Additionally, 3-phase installation enables the possibility of a larger solar system.)

Adopting these measures can effectively mitigate solar voltage rise, safeguard your equipment, and promote the sustainable utilization of renewable energy.

Volt response mode settings

Volt-Watt Response Mode

This outdated function is pre-set in your inverter to reduce in its maximum production capacity in a linear fashion between 250 volts and 265 volts. This means that if the voltage at your inverter is a legal 256 volts, then your inverter will be limited to 68% of its capacity. This will happen even if you are consuming all of your solar production and not contributing to voltage rise. That’s not splitting hairs – that’s like pulling on your handbrake while you’re cruising down the highway.

The CEC has pointed out that Volt-Watt response mode is a “blunt instrument”. I suggest in Qld we should be turning Volt-Watt off or increasing the lower limit to 255 volts. These values may be specified by your Electricity Distributor so it’s important to check that first. In Qld, the Volt-Watt setting is not required.

If the voltage at your inverter is a legal 256 volts, then your inverter will be limited to 68% … that’s not splitting hairs, that’s like pulling a handbrake …

Volt-Var Response Mode

Volt Var response mode will be OFF by default. If your sparkie takes the time to correctly enable Volt-Var mode, your inverter will gradually limit the production capacity when the voltage gets high. This can help prevent your inverter from tripping from overvoltage. (The values required in Qld are; between 248 volts and 253 volts, your inverter will reduce to 90% of its maximum capacity or a 0.9 power factor).

If the wrong mode is chosen, your inverter will be reduced to 90% of its maximum capacity even at normal operating voltages (eg, a 5kW inverter will only ever get to 4.5kW max).

Sustained overvoltage

Your inverter reaches 257 volts for 10 minutes – your inverter will turn off (a Qld Setting limit). If your sparkie ignores this adjustment, the inverter will turn off at 255 volts after 10 minutes.

Overvoltage

If your voltage reaches 260 volts for more than 1 second – your inverter will turn off.

Overvoltage

Your voltage reaches 265 volts. Your inverter will turn off.

The challenge arises when the installer is not familiar with the settings and needs to spend time adjusting your Fronius inverter on-site. Many inverters necessitate a Windows laptop and the appropriate adapter for these adjustments, which is inconvenient for MacBook users. Enphase and SolarEdge often require extensive efforts before their engineers will generate new grid profiles.

Ultimately, if your electrician does not modify the default settings of your inverter, it will shut down at conservative preset voltages. This is akin to driving with the handbrake engaged.

In conclusion,

with the increasing adoption of solar power, it’s crucial for owners of solar panels to understand solar voltage rise and implement strategies to mitigate it. Doing so will safeguard the safety, efficiency, and durability of their solar power systems. Measures such as installing voltage regulators, utilizing batteries, employing micro-inverters, and conducting consistent maintenance can protect equipment and support the expansion of renewable energy. Comprehending and managing solar voltage rise is an essential move towards a sustainable and dependable energy future.

Please take a look at the Solar Packages we offer: https://djsolar.com.au/solar-panels-solar-energy-systems-installer-brisbane/