Environmental Noise Impact Assessment. Crag Digital Energy Centre

Transcription

1 4 Turlough Gardens, Fairview, Dublin 3 Phone : +353 (0) Environmental Noise Impact Assessment Crag Digital Energy Centre Author : Dr. Peter Hill Date : September 2017

2 1 Introduction Acoustic Designs were engaged by Integrated Energy Systems International Limited (IES) to provide an assessment of potential environmental noise from the proposed Energy Centre for the Crag Digital data centre project at Clondalkin Industrial Estate, Clondalkin, Dublin 22. The proposed site development consists of a data centre with 28 data halls each of which will have 3 air handling units (AHU's) providing cooling on a duty-assist-standby basis. Chilled water and electrical power for the data centre will be provided by an onsite energy centre containing 8 gas engine/generators each with a heat recovery boiler and chiller system providing combined electrical power and cooling. This noise assessment is primarily concerned with the noise from the energy centre, however, breakout noise from the air handling units contained in the data centre is also included in the noise modelling. Noise modelling was carried out using NoiseMap 5. 2 Noise Receptors and Limits Clondalkin Industrial Estate is an industrial estate on the west of Dublin just outside the M50 motorway. This specific site is bounded by the M50 to the east, other industrial units to the north and west and the Grand Canal and Old Nangor Road to the south. The closest noise sensitive receptors are housing which is present at various distances on all sides of the site. The closest noise sensitive receptors are the residences on the southern side of Old Nangor Road. There are no noise sensitive receptors (residence, educational, healthcare, etc) in the business park. The primary noise sources on the site are engine exhaust noise from the energy centre gas engines as well as breakout noise through the building envelope of both Crag Digital 2

3 the energy centre and the data halls. The proposed development will not result in a noticeable increase in vehicle traffic in the area. 2.1 Site Noise Limits It is understood that the noise criteria outlined in Environmental Protection Agency (EPA) Guidance Note for Noise: Licence Applications, Surveys and Assessments in Relation to Scheduled Activities (NG4) April 2012 should apply at the boundary of this site. The NG4 document proposes the following noise limits; Daytime Evening Night time (07:00 to 19:00hrs) (19:00 to 23:00hrs) (23:00 to 07:00hrs) 55dB LA r,t 50dB LA r,t 45dB LA eq,t In addition, during the night time period no tonal or impulsive noise from the facility should be clearly audible or measurable at any NSL. In practice the energy centre will run 24 hours so the effective noise limit for continuous operation will be the night time noise criteria. Some operations such as bringing an engine on-line may generate higher noise levels in the short term. Where these activities are likely to result in noise levels above the EPA night time noise criteria, these activities can be scheduled to be carried out during daytime where possible. 3 Energy Centre The energy centre contains 8 parallel energy system units. Each unit consists of a gas engine and generator set, a heat recovery boiler and a chiller unit. Each of these units is contained in a separate room within the building. The exhaust from each engine and the boiler will be fed into a 45m high chimney. The primary noise sources from the energy centre are the engine noise and the engine/boiler exhaust noise for Crag Digital 3

4 each unit. The engines are enclosed within the buildings which will attenuate the noise from them and noise from the exhaust will be attenuated by silencers. Table 3.1 shows the sound power level data for the noise sources; Table 3.1 Sound Power Levels for energy centre plant LWA Data Centre AHUs Boilers Chillers Gas Engine Casing Gas Engine Exhaust The system is designed to run continuously with engines being periodically taken out of service for maintenance. During normal running, the gas engine exhaust will be passed through the boiler for heat recovery purposes, which is estimated to provide approximately 10dB of attenuation. The boiler is bypassed during engine startup for a period of about 20 minutes which will result in a higher noise level. However this will normally only occur for one engine at a time. The engine exhaust silencers can provide up to 35dB of attenuation. 4. Building Construction For the purposes of the noise modelling, the following Kingspan cladding construction was selected for the Energy Centre building. This construction was selected from the Kingspan Acoustic Performance Guide as offering the highest sound insulation performance from those listed. Walls: AWP/60 +Insulation + 19mm plasterboard(15kg/m2) + 0.7mm steel liner Roof: KS1000 LP/45 +Insulation + 2x12.5mm plasterboard (15.2kg/m2) These constructions are rated with a sound reduction of 48 and 58 db R w respectively. These figures are obtained in laboratory condition figures and are the maximum acoustic performance from these constructions. In practice the actual performance Crag Digital 4

5 will be degraded due to real word factors. It is therefore prudent to include a safety margin in the modelled noise levels. Noise levels in the data halls are significantly lower than the noise in the engine halls of the energy centre. It is therefore not necessary to use the lining proposed above. Kingspan AWP/60 wall panels and KS1000 RW/40 are both rated with sound reduction values of 25 db R w. The data hall breakout noise levels have been modelled with this wall and roof construction. 5. Noise Model Results Table 5.1 shows the sound pressure levels at the closest location on the site boundary due to the breakout noise through the building envelope, the noise from the exhaust with no attenuation and boiler bypass, the exhaust with boiler and silencer attenuation and the combined noise from the silenced exhaust and the building breakout noise. Table 5.1 Calculated site boundary noise levels due to the energy centre. db LAeq Engine exhaust (no attenuation) 74.3 Engine exhaust (silencer + boiler) 29.6 Building breakout noise 36.5 Combined (breakout + silenced exhaust) 37.3 Combined noise during startup 38.0 It is clear from Table 5.1 that the noise from the engine exhaust is the primary noise source from the proposed activities on the site. Without a silencer, noise from the engine exhaust is excessive. Breakout noise through the building envelope is not excessive with the proposed construction. Care will need to be taken in the design and construction details to achieve the maximum sound insulation performance from the proposed construction. Crag Digital 5

6 Fitting a silencer to the engine/boiler exhaust reduces the noise from the plant on the site to well below the EPA night time noise criteria. This is also the case when one engine is in startup mode (boiler bypassed) and all other engines running normally. Thus it will not be necessary to restrict engine startup schedules to certain times of day. Table 5.1 shows that the proposed EPA site boundary sound levels can be met during normal operation of the proposed site plant.. Figure 5.1 Noise contours for the proposed energy centre with silenced exhaust. Crag Digital 6

7 6 Conclusions The calculated noise level from the proposed energy centre will require noise reduction from the engine exhaust in order to meet the EPA guideline noise levels during normal operation. The calculated noise level from the proposed energy centre can meet the EPA guideline noise levels during normal operation with the proposed Kingspan building construction and silenced (35dB attenuation) exhaust. Crag Digital 7

8 Appendix I Glossary of Technical Terms A-weighting Frequency weighting applied to sound measurements intended to mimic the frequency sensitivity of the human ear at low to moderate noise L Aeq L Ar levels. Denoted by A Equivalent continuous A-weighted sound pressure level of a steady sound that has, over a given period, the same energy as the fluctuating sound being measured. (re 20mPa) 2 A-weighted noise rating level. Obtained from the L Aeq noise level with appropriate weightings to adjust for the character of the noise Crag Digital 8

9 Appendix II 3D model view of the proposed data centre Crag Digital 9