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Noise emissions from inverters and battery charging stations |
Solar inverters
PV systems convert sunlight into electrical energy in the form of DC voltage. To feed the power generated in this way into an AC grid, the DC voltage must be converted into AC voltage. Inverters are used for this purpose. In large systems, the energy that has to be converted is so high that so-called central inverters are used. To cool the components inside the inverter, a flow of air must be fed into the housing through an inlet opening, which absorbs the heat from the internal components and slides out of the housing again through an outlet opening.
Depending on the volume of heat generated, the natural movement of convection can be used for this purpose; in the case of large air volumes, this convection must be forced by a fan that dissipates the hot air. Practically all larger inverters are therefore equipped with support fans that generate sound through the oscillation of the air. In addition, the inductivity of the inverters generates additional noise emissions in the audible medium frequency range. If inverters are located near inhabited buildings, the audible clock-frequency noise may lead to complaints against the operation of the PV system.
This leads to the dilemma that increasing the switching frequency with the aim of shifting the noise emissions into the inaudible range leads to a significant reduction in efficiency and a massive increase in cooling costs due to faster switching. Since inverters are usually installed directly on or near house walls, another problem is that the sound is reflected by the walls and can be transmitted to areas that are relatively far away from the device location.
This is where our acoustic enclosures offer a remedy.
Designed for the installation site, our acoustic enclosures reduce the noise emissions from inverters on the basis of the following acoustic principles:
Sound insulation
Sound absorption
Prevention of sound reflection
This is achieved firstly through the targeted guidance and deflection of the air flow and the refraction of air vibrations. It is also achieved by the insulation in the acoustic enclosure, which covers a wide frequency spectrum and, last but not least, by encapsulating the sound within the enclosure.
PV systems convert sunlight into electrical energy in the form of DC voltage. To feed the power generated in this way into an AC grid, the DC voltage must be converted into AC voltage. Inverters are used for this purpose. In large systems, the energy that has to be converted is so high that so-called central inverters are used. To cool the components inside the inverter, a flow of air must be fed into the housing through an inlet opening, which absorbs the heat from the internal components and slides out of the housing again through an outlet opening.
Depending on the volume of heat generated, the natural movement of convection can be used for this purpose; in the case of large air volumes, this convection must be forced by a fan that dissipates the hot air. Practically all larger inverters are therefore equipped with support fans that generate sound through the oscillation of the air. In addition, the inductivity of the inverters generates additional noise emissions in the audible medium frequency range. If inverters are located near inhabited buildings, the audible clock-frequency noise may lead to complaints against the operation of the PV system.
This leads to the dilemma that increasing the switching frequency with the aim of shifting the noise emissions into the inaudible range leads to a significant reduction in efficiency and a massive increase in cooling costs due to faster switching. Since inverters are usually installed directly on or near house walls, another problem is that the sound is reflected by the walls and can be transmitted to areas that are relatively far away from the device location.
This is where our acoustic enclosures offer a remedy.
Designed for the installation site, our acoustic enclosures reduce the noise emissions from inverters on the basis of the following acoustic principles:
Sound insulation
Sound absorption
Prevention of sound reflection
This is achieved firstly through the targeted guidance and deflection of the air flow and the refraction of air vibrations. It is also achieved by the insulation in the acoustic enclosure, which covers a wide frequency spectrum and, last but not least, by encapsulating the sound within the enclosure.
Mounting methods and types of invertersInstallation types
We differentiate between the following installation locations: - Wall mounting - Floor mounting - Mounting directly under a solar table Types of inverters.
String and multi-string inverters, module inverters, stand-alone inverters Battery inverters, central inverters (output from 100 to 1,200 kW). 
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Main sources of noise
Fans and the inductivity of the inverters, which is perceived as clocking. The sound level of inverters is between 30 and 63 dB(A), depending on the inverter type, design and installation location. The sound level increases with increasing inverter load. This clearly shows that the design and location play a central role in avoiding noise complaints. When installing inverters on house walls, care must be taken to decouple the device from the house wall using rubber buffers so that no device vibrations are transmitted to the house wall. Such vibrations can not only be perceived in the house but can also be reflected into other areas. Sun protection for inverters Inverters should always be installed in a cool place. The losses that inevitably occur during the transformation from DC to AC voltage are released into the ambient air in the form of heat. The cooler the environment, the better the heat can be dissipated. Cooling takes place either via cooling fins or via fans integrated in the inverter. As long as the maximum permissible temperature of the inverter is not reached (the inverter regulates in this case), the loss of power is not dramatic. High temperatures can have a more drastic effect on the service life of the inverter. Analyses have shown that an increase in temperature of 10 Kelvin (equivalent to 10°C) can reduce the life expectancy of the electrical components by up to 50%. Locations such as rooms under the roof, a warm boiler room or places with direct sunlight should not be selected or, if this is not possible, the inverters should be protected from atmospheric influences and also by shading. 
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Sound and weather protection for inverters |
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The basic structure of the acoustic bonnet is an aluminium plug-in profile frame.
The service doors around the system are integrated into the profile frame. The sound enclosure requires a concrete or metal base in the base area of the sound enclosure on which the enclosure is fixed. The acoustic bonnet has service doors around the inverters to allow unhindered access for maintenance and service work. The supply of fresh air and the removal of hot air is ensured via corresponding ventilation openings. The air openings are designed on the non-noise-sensitive side to ensure optimum sound insulation. The service doors are based on 1.5 mm thick aluminium panels with 40 mm thick "Stratocell®Whisper" insulation on the inside; this material has some of the best sound-absorbing properties available on the market. As the laminated polyethylene foam absorbs noise and does not reflect it, it is an excellent alternative to many of the noise protection materials used today. The insulation is also moisture-resistant, does not build up mould, can be rinsed with a high-pressure cleaner and complies with fire protection class: B-S2-d0 (flame-retardant). |
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Sound enclosures basic features |
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Die Schallhaube braucht zur Auflage eine Ebene aus Beton oder Metall, in der Grundfläche der Schallhaube, auf der die Haube fixiert wird.
Die Schallhaube hat rund um die Wechselrichter Servicetüren die einen ungehinderten Zugang für Wartung- und Service arbeiten ermöglichen. 
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1 ) Air inlet for cooling the inverters
2) Discharge of warm air 3) Base frame of the acoustic bonnet 5.5 cm aluminium profiles 4) Service doors made of 5 cm aluminium panels with 40 mm insulation on the inside 5) Roof panels with a Static load of 160 kg/m2 6) Internal insulation made of StratocellWhipser 40 mm |
Sound enclosure with green roof for inverters |
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Unsere begrünten Schallhauben sind optisch ansprechend durch die freie Wahl der RAL-Farbe, in Kombination mit den Pflanzen. Zudem leisten sie einen wichtigen Beitrag im Kampf gegen den Klimawandel.
Für die Bepflanzung der Schallhauben-Dächer eignen sich vor allem immer grüne Sedum Pflanzen, die mit wenig Wasser und Sonne auskommen. Als Substrat eignet sich ein Gemisch aus Perlit und Pflanzenerde, diese Kombination erlaubt die Füllung der Pflanzenwanne, ohne dass ein grosses Gewicht entsteht und bietet den Pflanzen eine Ideale Struktur für die Wurzelbildung. Energetische Vorteile Durch die Schichtung auf dem Schallhauben-Dach wird zusätzlich der Akustische Komfort erhöht respektive die Schallisolation gegen oben nochmals verstärkt. Zudem bieten sich energetische Vorteile dadurch, dass die Umgebung der Wechselrichter auch bei direkt Sonneneinstrahlung nicht erhöht wird. Dies schützt den Ertrag der PV-Anlage auch an Hitzetagen und erhöht die Lebensdauer der Wechselrichter. |
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Noise protection bonnets based on the same principle for compressors, ORC systems and other industrial applications. |
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