Decarbonisation and electrification – are they really quieter?

Decarbonisation and electrification are hailed as crucial steps towards a sustainable future, with promises for cleaner energy and reductions in carbon emissions. However, these do not inherently lead to quieter environments. They do, of course, offer numerous environmental benefits, such as mitigating climate change and improving air quality, but their impacts on noise are more nuanced.

Let us delve into the various aspects of noise generation associated with a low carbon transition:

Electric vehicles

While EVs can be quieter than traditional internal combustion engine vehicles at low speeds, they still produce noise. This comes from tyre-road interaction and aerodynamic effects at higher speeds. The increased use of EVs would not greatly affect traffic noise emissions from higher speed motorways (which are a dominant noise contributor across the world). Additionally, the need for pedestrian safety to introduce artificial engine sounds at low speeds and reversing alarms has presented a new soundscape for us to become accustomed to.

The widespread need for electric vehicle charging infrastructure also presents new acoustic challenges. While smaller home chargers are not an issue, larger cabinet-type ‘super chargers’ come with cooling fans and transformer hum. In addition, an EV’s own fans and compressors will operate when fast charging to avoid the battery overheating, and accurate sound level data tests are often unavailable for these newer technologies. The fans change speed depending on the demand; this creates a character to the fan noise which increases the potential for annoyance.

With super chargers potentially falling within proposed changes to Permitted Development rights in the UK, without a need for detailed acoustic assessment scrutinised by external stakeholders, these could pose a future noise source with little recourse for post-installation mitigation.

Renewable energy

Decarbonisation efforts typically involve the deployment of renewable energy sources , which are often perceived as silent alternatives to fossil fuel -based power generation. While it is true that renewable energy technologies produce less operational noise compared to conventional power plants, it is a myth that they are inherently quieter.

Wind turbines, for instance, generate noise from blade rotation, gearbox operation, and aerodynamic effects. This can be audible to residents near and far, particularly in quiet rural areas. Furthermore, the construction and maintenance of renewable energy infrastructure can also introduce temporary increases in noise levels. Large -scale projects such as offshore wind farms require extensive construction activities involving seismic surveys, marine transportation, dredging, drilling, and piling, which can disrupt already endangered marine wildlife habitats.

Solar power installations involve the use of equipment such as inverters, substations, and battery energy storage systems (BESS) with associated cooling systems. These can all contribute to ambient noise levels. To gain the economies of scale needed for efficient clean energy production, solar farms need to be deployed across large areas - typically starting at 200 acres for commercial grade projects – resulting in a wide dispersion of both construction and operational phase noise impacts.

National Planning Policy also requires consideration of ‘Agent of Change’ principles. However, there have been little to no studies on how swathes of solar panels can function as ground reflectors, unrevealingly increasing the distance at which other sound sources (eg road traffic, industrial facilities) can propagate across large distances.

Air source heat pumps

Another aspect to consider is the indirect effects of the transition to electric heating and cooling systems in buildings which make way for ground, water, or air source heat pumps. But with most building stock found in densely populated urban cities, without an easy access to deep ground or water sources, often the only workable options are air source heat pumps (ASHPs).

ASHPs can be multiple times more efficient than previous system - they produce less carbon, have lower operating costs, and reduce energy consumption. Early engagement is vital to find suitable locations for ASHPs. This prevents needing unforeseen extensive acoustic mitigation at a later stage, with rooftops being an inconspicuous location of choice.

Still, there are challenges when using ASHPs in already noisy cities.

• With many overlooking sensitive receptors in proximity, and a preference by local authorities to avoid ‘background creep’, stringent noise limits often apply to new ASHP installations.
• Manufacturer sound level data is often supplied as a side-on measurement, which does not reliably represent when the dominant air flow (and resultant noise) is vertically orientated. Therefore, it may not be consistently assessed in noise emission predictions.

• Options to attenuate noise emissions are often also limited; top hat silencers have only a moderate level of attenuation. Any in-line attenuation will increase the pressure on the system too, potentially making the fan work harder and become noisier.
• ASHP manufacturers will cautiously require surrounding enclosures and acoustic louvres to have generous separation distances to maintain necessary air flow, which can easily fill the available roof space with accompanying structural loading and visual impacts. If anything, there is often more resistance to mitigation rather than resistance to air flow!

Conclusion

While decarbonisation and electrification offer significant environmental benefits, including reduced greenhouse gas emissions and improved air quality, they do not guarantee a quieter world by default. The noise impacts of these transitions depend on a multitude of factors, including technological advancements, urban planning strategies, and societal choices. Electrification is not necessarily any quieter; it just sounds different. As we strive towards a more sustainable future, it is essential to consider noise reduction as an integral part of our efforts to create healthier and more liveable communities.