There is somewhat of a revolution occurring throughout the UK and Europe, as the number of Combined Heat and Power (CHP) installations continues to grow, amongst renewed investment in cogeneration technology. With the potential to deliver major economic advantages and address electricity supply issues, it is perhaps little surprise that the uptake of such systems is rising rapidly. Such systems also present a number of challenges for site operators, not least the noise impact on surrounding premises.

Power has traditionally been generated in large power stations situated away from noise-sensitive areas, such as residential estates. However, the increase in the use of on-site CHP plants in hospitals, retail and district-heating schemes – to name a few – has brought industrial noise into the heart of communities.

Wakefield Acoustics equipment
24/7 requirement for power generation on such sites undoubtedly has the potential to disturb our everyday lives. This risk is reflected in both the strict noise control regulations and the noise measures being installed to prevent excessive noise on such installations.hilst the introduction of noise sources into mixed industrial and residential areas is not a new occurrence, CHP plants and energy centres can present challenging noise control issues due to the high amplitude and low-frequency tonal nature of noise produced by engines and associated exhaust systems.In order to quantify the noise impact from such installations upon nearby residential areas, it is normal practice to undertake an assessment in line with BS4142:2014. Taking current noise levels on site, and calculating (or measuring) the effects from new noise sources, the standard determines the likelihood and severity of adverse impacts on noise sensitive areas.

In focus: case study

Mitigating acoustic emissions from multipart cogeneration machinery can be a complex and challenging task. So, when a large UK hospital installed a new CHP system, comprising two gas engines, into an existing energy centre on-site, they turned to Wakefield Acoustics to provide a state-of-the-art noise control solution.

The plant provided continuous power to the hospital, but due its location being 30-40m away from a number of residential properties, noise emissions from the processes and the equipment were highly regulated. This being the case, a tight noise target was imposed for the project which required a noise level of 39dBA to be achieved at the properties.

In order to effectively mitigate the noise on-site, one of the gas engines was isolated inside an acoustic enclosure within the existing energy centre building. Such isolation ensured noise inside the energy centre complied with Control of Noise at Work Regulations. With available space for the second gas engine limited, an acoustic enclosure was integrated to house the engine partially within the building, and partly outside the structure.

Whilst the design of the acoustic enclosure panels was relatively straight-forward, the ventilation system was a little more of a challenge. High ventilation rates were required for cooling of the engines whilst also incorporating suitable noise control measures within the confines of the existing building fabric. In order to achieve this, large ventilation attenuator units were designed to fit within the available space of the building. The ventilation fans were also supplied by Wakefield Acoustics as part of the turnkey package, which were required to draw the air through the attenuators, motorised dampers, filter boxes, louvres and associated ductwork forming the full ventilation systems.

As with most CHP installations, all components within the system were fully designed from an acoustic perspective to ensure there were no areas through which excessive noise could pass. Careful consideration was also given to the building in which the equipment is housed, as well as the ventilation equipment and engine exhaust systems in place.

At the hospital, a detailed noise survey was undertaken at the start of the project in order to identify and treat any weak points in the building fabric which may have created a path through which noise could pass. Following the survey, all noise transmission paths were considered and treated appropriately to ensure site noise targets could be met.

Through careful diagnosis and the implementation of the acoustic technologies, noise levels across from the hospital CHP system were treated in line with the facilities goals.

For more information visit: www.wakefieldacoustics.co.uk