The long-term success of a PV system ultimately relies heavily on the quality of the components within it – and too often many inverter manufacturers cut corners to achieve less expensive products that will sell quickly.
Why Quality, Safety & Testing Matter in Your PV Inverters
Matt Marx | SMA America
When it comes to choosing an inverter, quality and safety are essential. These two factors work together to ensure maximum efficiency and sustainability for PV projects.
While many installers prefer different inverter brands for different reasons, one thing that most installers want is an inverter they can trust. Leading manufacturers rely on state-of-the-art testing facilities to regularly test their equipment alongside other competitors. This ensures the creation of reliable and high-quality products.
Often, inverters that aren’t manufactured with quality in mind or tested thoroughly result in some serious consequences that will affect the life of a PV plant, and more importantly, profitability. Here are a few reasons that investing in a quality product is more important than saving on upfront costs.
Passive Cooling Leads to Loss of Power Output
The primary cause of semiconductor failures in inverters is temperature cycling, so it is critical that inverter manufacturers design products that will achieve effective temperature management in order to maintain the health and profitability of a system.
Many inverters are designed using passive cooling, which is said to eliminate the need for additional components (and ultimately result in fewer components). However, under testing, SMA found that this approach forced the inverter to reduce its power output in an effort to cool the various components. Poorly designed heat sinks also trapped falling dust and debris, reducing cooling effectiveness even more and causing hot spots in crucial power components.
A passive cooling temperature management strategy dramatically reduces power output, lessening the life of a PV component by 75 percent. In systems that are designed to operate for 20 to 30 years, this loss of power output resulting from passive cooling can have a profound effect on reliability, power production, and O&M costs – which prevents a plant owner from maximizing profitability.
Poor DC:AC Ratios Equal High Maintenance Costs
As module prices continue to decline, integrators can realize a significant opportunity to increase the size of a PV array while maintaining the number of inverters, otherwise known as increasing the DC:AC ratio, which is the key determinant of MWh yield, levelized cost of energy, and ROI.
A high DC:AC ratio increases lifetime power production and profitability, and can actually reduce balance-of-system costs up to 50 percent. However, not all inverter manufacturers are able to achieve high DC:AC design ratios.
Poor DC:AC ratios forces plant designers to choose between a reduced array size – which reduces lifetime power production – or an increased number of inverters to achieve the same lifetime power production, which leads to approximately 40 percent higher inverter costs as well as higher O&M costs over the life of a system.
PV inverters are a source of electromagnetic interference (EMI), which is something that has to be limited. EMI occurs during the flow of electrons in many devices, including PV inverters. The level of EMI that PV inverters generate must be below a certain level, otherwise, the inverter might interfere with critical operations in military, air traffic control, railroads or FM-radio frequencies.
Some inverters on the market have EMI values more than 10 times what is legally allowed, which is grounds for unwanted legal attention. The reason EMI is so high in some inverters is likely due to undersized filters. Correctly sized filters could be used, but they are more costly and have thus been sacrificed in the design of some low-cost manufacturers.
The key takeaway when it comes to EMI levels is that it isn’t just one component of an inverter that contributes to high EMI: It’s the overall design of these inverters that results in a lower quality product that does not comply with existing laws.
Loss of Power Output
Obviously, the more sun a solar plant is exposed to, the more power it can produce. But this also exposes the electrical components of an inverter to heat – and these components are almost always temperature sensitive. At higher temperatures, inverter components can start to lose performance and decrease lifetime expectancy.
However, high-quality inverters should perform well under normal, ambient temperatures. In SMA’s testing facility, which tested inverters for performance stability when exposed to ambient temperatures that are common in solar plants, results showed that some inverters suffer power loss at ambient temperatures as low as 21 degrees Celsius. At a temperature of 35 degrees Celsius, output power degraded to 20 percent less performance overall and it continues to diminish with each additional centigrade.
IT Security Issues
Many manufacturers offer cloud-based remote management system to operate, control and maintain PV systems.
Cloud-based, remote management systems are a great way to monitor and control a PV plant – but not every cloud management system is safe or secure. Many of the servers that host remote cloud-based systems are located in China, which has a dubious reputation for government controlled internet and censorship – – which means that customers could be cut off from their PV system data or even lose access to their energy supply in extreme cases.
The long-term success of a PV system ultimately relies heavily on the quality of the components within it – and too often many inverter manufacturers cut corners to achieve less expensive products that will sell quickly. Before selecting equipment and designing a project, it is imperative that integrators consider the true cost of lower-priced inverters versus investing in quality inverters that they can trust.
The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag
SMA America is the U.S.-based subsidiary of global PV leader SMA Solar Technology AG. SMA is a power conversion, energy management and support service provider for residential through utility-scale photovoltaic systems. SMA's leading range of solar inverters and related technologies spans all power classes and is compatible with all module types, resulting in the largest solutions portfolio in the industry. With more than 30 years of experience and 35 gigawatts of installed capacity, SMA is represented in every major PV market on the planet and continues to lead the industry with unmatched technological innovation, strong service support and educational programs.
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