Reducing Noise in PV Power Plants

Reducing Noise in PV Power Plants
Reducing Noise in
PV Power Plants
Comprehensive testing points the way to significantly reducing noise from central inverters
Photovoltaics in Japan: SMA Sunny Central CP JP inverters are in operation in the Kagoshima PV power plant and in densely populated areas of the island country.
Typically, PV power plants are spread out over several acres of land far from residences, towns or cities. Up
until now, central inverter manufacturers have not had to deal with noise emissions from the central inverters
in and near such large industrial PV farms. In collaboration with the Rheinisch-Westfälischen Technischen
Hochschule Aachen (RWTH University Aachen), SMA Solar Technology AG carried out comprehensive and
complex testing to identify the sources of noise and ways to reduce it. We found that because noise emissions
behave logarithmically, a 10dB reduction will cut the central inverter’s noise emissions by half.
“We’ve been asked to look into reducing the noise generated by our central inverters, especially those in the
more densely populated regions in Japan,” said Aaron Gerdemann, Global Product Manager at SMA Solar
Technology AG and expert for the Japanese market.
As more and more major PV power plants are operating near residential areas, villages and towns, there is a
growing demand for quieter central inverters. The findings of the tests have already lead to implementing the first
noise reduction measures, and a retrofit kit is available now for central inverters already in operation.
Test Scenario for Extensive Inspection
The experts from RWTH Aachen have extensive experience in industrial noise emission testing for machines and
machine systems. However, this project was the very first time that inverters had been the focus of noise emission
tests. Using extensive test equipment, the team performed a multitude of different acoustic tests to identify and
classify all sources of noise in the central inverter during operation.
They performed a number of assessments and analyses including:
• Investigation of structure-borne noise transfer paths
• Transfer of airborne noise and its effects
• Analysis of noise caused by vibrations
• Resonance frequency testing
To visualize from exactly which sources
noise is generated, an acoustic camera
was used to closely examine a stock
Sunny Central 500 CP-JP central inverter
during normal operation up to full load.
Once the test team was able to identify
the choke as the main source of noise, it
was removed and went through the same
testing.
Measuring Airborne and Structure-Borne Noise
They intentionally produced structureborne vibrations inside the central inverter
with a shaker unit in place of the choke,
and closely observed how individual
components reacted.
Using an omnidirectional loudspeaker
inside the central inverter, the test team
was able to identify where structure
noise and airborne noise occurred.
Considerable Reduction in Noise
Taking into account all the test results, the Sunny Central CP central inverter can now be operated with
considerably reduced noise emissions. The actual noise of the central inverter depends on different parameters
and varies individually in for example power class, installation (concrete base or plinth) optional equipment,
and. component tolerances.
Splitter silencers with rain protection attached on the rear of the central inverter.
SMA Solar Technology AG
Sonnenallee 1
34266 Niestetal, Germany
Tel: +49 561 9522-0
Fax: +49 561 9522-100
E-mail: Powerplants@SMA.de
www.SMA.de/powerplants
WP_NOISE-REDUCTION AEN141310 Printed on chlorine-free paper. Technical specifications subject to change without notice.
The Sunny Central CP inverters underwent extensive hardware and software modifications to reduce noise. For
example, the inverter’s modulation process has been changed and the air exhaust equipped with a specially
designed splitter silencer. The internal structure of the splitter silencer was configured specifically for wave
lengths resulting from the inverter bridge’s 3 kHz cycle frequency. Also, other inverter components have been
acoustically improved by adding base paneling and an air baffle. On average these measures lead to a
reduction to half of the percepted noise level in a 10 meters distance.
These noise reducing measures are available for central inverters as an option but can also be used to retrofit
existing installations. Long term, plans are underway to find a choke manufacturer to produce a “quieter” choke.
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