The leading manufacturer of solar inverters SMA conducted a test series in which they compared the performance of their products to much cheaper products of a competitor. Here are the 5 key findings.
FACT 1: Passive cooling reduces PV component’s lifetime by up to 75%.
With ca. every 10°C higher temperature of a component, the lifetime is halved. For the relatively cheap inverter, tests at full power revealed temperatures to be 20°C higher than what you would see in an high-quality inverter of the same power class.
Applying Arrhenius’ rule, this means a lifetime reduction of 75%. The reason: The cheap inverter uses passive cooling which is not powerful enough. In contrast, SMA's OptiCool™ intelligent temperature management technology allows more power output with less heat stress.
FACT 2: The inexpensive inverter loses power output when ambient temperatures rise.
The tests showed that the inexpensive inverter, that produced 30 kW (or 100%) at 20°C, significantly lost output power when the ambient temperature rose above 21°C. At a temperature of 35°C, quite common for solar power plants, the output power degraded to 24 kW. This equals 20% less performance and it got worse with every additional centigrade.
The SMA inverters managed to deliver 100% power output – even if outside temperatures rose up 50°C.
FACT 3: The cheap inverters‘ 1:1 DC:AC ratio creates higher costs
The advised DC:AC ratio of 1:1 of the cheaper inverters force plant designers to choose between a reduced array size – reducing lifetime power production – or an increased number of inverters. This also increases installation costs, as well as operations and maintenance costs, and eliminates any perceived benefits of lower inverter cost.
A higher DC:AC ratio on the other hand like the industry-leading 1.5:1 ratio of SMA inverters increases the lifetime power production and profitability with an significant impact on system design and can actually reduce balance-of-system costs up to 50%.
FACT 4: The cheap inverter produced 16x higher EMI than legally allowed.
The tested inexpensive inverters produced electromagnetic interferences far above permissible limits of regulation EN 6100-6-3:2011. Peak values were at 65dBμV/m, which is more than 16x the allowable threshold. However, the manufacturer chose to untruthfully place a “CE” mark on its product.
Most likely, the reasons are undersized filters because of the passive cooling concept. Undersized filters are used to generate less heat. This leads to the assumption that the manufacturer has chosen to save costs and thereby created a potentially dangerous environment.
Dangerous, because disturbing the radio frequencies is an unlawful act. In Germany, this might be a violation of §315 StGB, which could result in a punishment of up to 10 years imprisonment.
FACT 5: The Chinese Great Firewall could cut you off from your energy supply
The manufacturer of the cheaper inverters offers a cloud based PV management system with servers located in China. With the "Great Firewall" and the "Golden Shield Project", China has a large set of powerful tools for surveillance and to even shut down internet access completely as it happened in 2009, when internet access was blocked in the region Xinjiang.
Given the widespread capabilities the government has to control and even shut down access to the Internet, it is possible that censorship measures could also lead to a shutdown of your electricity supply if your server happens to be in a blocked region.
The test results show that inexpensive inverters might come at a price PV system operators probably would not want to pay. With high quality inverters like those of SMA, PV system operators can have more power output, a longer system lifetime, save themselves from legal trouble, and also save costs in the long run. For more information about the tests, visit solar-trust.com where you can download a test report.