It is well-known that inverters, as semiconductor-based electronic products, are sensitive to heat. Under low temperature, they work better, and are vulnerable to power loss and damage at high temperatures, although the semiconductor components themselves are heat-resistant.
At present, the inverters adopt two methods of cooling, which is natural cooling and fan cooling. Low-power models mainly use natural cooling, and medium to high-power models are basically fan-cooled.
When the inverter converts DC power to AC power, heat is generated. This heat will be transferred to the ambient temperature of the inverter shell. The temperature needs to be kept below a certain level, above that level the material in the inverter will begin to degrade, insulation will become brittle, solder will expand and crack and the metal parts in the capacitor will be fatigue. In that case, it will not only affect the efficiency of the inverter, but also shorten service life.
Even in Australia, where the temperature environment is milder, there are still some areas where the maximum temperature can reach 40 degrees in summer, and with the heat emitted inside the inverter, the ambient temperature of the inverter is usually higher than the local natural temperature. Just like when you cook in the kitchen in summer, you can feel that the temperature in the kitchen is higher than the temperature of the other rooms in the house.
The inverter itself is also a heat source. To keep heat low, the inverter will stop generating electricity or “de-rating” through the system to notify the inverter’s brain, which is also known as temperature derating. The power is reduced gradually, and in extreme cases, the inverter will be completely turned off. Only when temperature drops back to a threshold value, the inverter will return to the optimal working state.
As early as many years ago, the inverter will begin to de-rating at 25 degrees. With the continuous innovation of technology, the current inverter can reach 40 degrees before starting to commence de-rating, and the inverter with excellent quality design may not begin to do this until at higher temperatures.
So how can you know if the inverter is derating, or do you need to worry about inverter load reduction?
Derating is actually more difficult to see because the load reduction parameters are not written on the parameter table, and sometimes they are drowned in a corner of the manual.
You will need to be aware the following:
- The inverter should not be installed under direct sunlight or unventilated rooms.
- How many days a year can the temperature in the area you live in reach more than 40°, and if this number of days is small, then don’t worry too much about these power losses. In the case of cold weather, the power generated by the inverter is a little more than the rated power, which also makes up for some losses.
- Maintain a minimum clearance between adjacent inverters or other objects specified in the installation guide.
- Most inverters begin to derate between 40-45°, so if the inverter is installed under the roof and nightside or under the solar modules, those help inverters to maintain a state of basically no derating.
Let’s take a look at the derating curves of several different brands.
SMA didn’t do as well. Solis and Each Energy did very well. However, what is surprising is that I found that all Each Energy single-phase grid-connected inverters with a rated power of less than or equal to 3 kw can still work at full rate at 60 degrees, which can almost be said to never derate as the temperature above 60 degrees is not a normal degrees, unless there is a fire.
There is no place on earth where the daily temperature can reach such a high!
I was puzzled why they could perform so well, it turned out to be related to the design of the structure. The inductances of SMA and other brands are mostly built-in, and Each Energy put it outside of the housing, reducing the impact of inductances heating on the machine. This change is really clever.
Of course, Solis also adopted such a design to reduce internal heat, but from the derating curve, Solis’s performance is not as good as Each Energy, then it must be the difference in internal structure design. The inverter you buy may look beautiful in appearance, but whether its internal organs are beautiful and neat does affect the performance of the inverter. The internal structure is reasonably arranged, and the heat dissipation components are installed around the internal devices that are prone to heat, which can effectively and reasonably reduce the heating situation of the inverter, and more stabilize the performance of the inverter, so that the inverter still maintains excellent output under extreme temperature conditions.
While ensuring their installation conditions, the smaller the inverter, the shorter the peripheral distance requirements. Take Each Energy for example, only 150mm is needed on the left and right sides of inverters, which of course means that its heat dissipation is better, and the same area can be installed more machines.
Because it is installed outdoors, the protection level of the inverter must reach IP65, or even IP66, which can prevent dust, rain, salt spray corrosion, and adapt to the harsh external environment. In places with serious pollution, or dust, it will affect the function of the heat dissipation because fine objects such as dust, leaves, and sediment may also enter the air duct of the inverter, which will also affect the power generation and service life of the inverter. In order to improve the actual service life of the inverter and maintain the maximum power generation efficiency – It is necessary to create a good operating environment for the inverter to protect it from wind, sun, and rain. Also, regular inspections should be carried out to keep the heat dissipation smooth and avoid over-temperature derating and other faults.