Echelon Data Centres – LCY10 Nos 1, 2 and 4 Greenwich View Place, London E14 9NN Heat Rejection Using Dock Cooling – Technical Note 4Th December 2020 Rev 02
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Echelon Data Centres – LCY10 Nos 1, 2 and 4 Greenwich View Place, London E14 9NN Heat Rejection using Dock Cooling – Technical Note 4th December 2020 Rev 02 1.0 Introduction Echelon Data Centres (Echelon DC) are developing the buildings at Nos 1, 2 and 4 (known as GV1, GV2 and GV4) Greenwich View Place to become a single data centre. Previously the buildings were 3 separate units, but through planning approvals received in 2012 and 2016, they have now become a single building now termed LCY-10. Previously HDR|Hurley Palmer Flatt produced a paper on the “External Energy Options” that were available to the project at LCY-10 including the use of dock cooling for heat rejection in tandem in a resilient format with the Barkantine Energy System (similar to Option 6). This Technical Note considers the reality of being able to reject heat into the nearby Outer Millwall Dock and any implications to being able to provide the capacity required to support the overall 17MW of IT load capacity within LCY-10. 2.0 Background The LCY-10 buildings are built adjacent to the Outer Millwall Dock located in the Isle of Dogs Peninsula in East London. Figure 1 shows the location, Figure 2 shows the key side with GV3 building protruding over the top of the dock itself approx. 1m above the water level. The dock is considered a closed water body, the slipway to the Thames opposite Surrey Quays is completely close and has the West Ferry Road running over it. To the North via the Glengall Bridge, there is the Millwall Inner Dock which then connects by canal connection to the South Dock; although the South Dock can be opened to the Thames, all of the docks are effectively closed. LCY-10 Figure 1 – Millwall Dock Location Map Echelon - LCY10 - Dock Cooling Technical Note 041220 rev02.docx Page 1 of 13 Figure 2 - LCY-10 Buildings at Millwall Outer Dock The Millwall Docks were planned to be built in 1865 and were completed in 1867, there was some rebuilding in 1943 due to bomb damage and construction of “false quays” in the 1960s, however the water levels and depths remained the same. There is significant detail around the provision and building of the docks, more detail can be found in the link below: https://www.british-history.ac.uk/survey-london/vols43-4/pp353-356 In terms of the outer dock’s capacity, this has been calculated by use of mapping and information on the building of the dock sections as shown in Figure 3 below. Section “b” illustrates the depth of the water at approx. 7.5m at its shallowest point and considering some degree of silting. Dock Specification More than 8,000ft of dock wall, between 28ft and 30ft high, was built to enclose 35½ acres of water, 24ft deep (fig. 129a). This walling survives, but it is behind later quays except at the north end of the Inner Dock and along the south quay of the Outer Dock. It has straight sides with a slight batter, and a brick skin about 2ft thick backed by mass concrete up to 11ft 6in. thick. Horizontal bands of brickwork tie the facing into the backing. The walls originally had Bramley Fall stone copings with continuous mooring rails. Figure 3 - Millwall Outer Dock Sections (reference “b”) and Dock Specification Echelon - LCY10 - Dock Cooling Technical Note 041220 rev02.docx Page 2 of 13 The area of the outer dock has also been calculated and is shown in Figure 4 below, this combined with the section gives an overall indication of the total volume of the dock also shown in Figure 4 of 720,000cu.m. This obviously doesn’t take into account the neighbouring volume of water in the Inner Millwall Dock, which is considered only as a benefit and not the main location for the heat rejection. Figure 4 - Millwall Outer Dock Area and Volume Calculation These calculations are then taken forward into the CFD modelling for the heat rejection process into the Outer Dock. 3.0 Heat Rejection and Constraints The expected IT load capacity for the LCY-10 project has now been increased to 17MW, this gives a total heat rejection of approximately 22MW to be rejected over two independent systems, although linked if required, systems as follows: A) Dry air coolers located across the roof areas of LCY-10 in a resilient format with valving to give concurrent maintainability. This format provides up to 60% of the overall heat rejection capacity B) Heat rejection to the Barkantine Energy System or the Dock Cooling with either system taking the capacity of approx. 40% of the overall required heat rejection. For resilience purposes both systems have to be capable to being able to cope with having up to 10MW of heat rejection. For the Dock Cooling system, this is covered by a license from Environment Agency Permit reference EPR/NB3996VS. A copy of the permit is contained within Appendix A and in summary permits the following: Echelon - LCY10 - Dock Cooling Technical Note 041220 rev02.docx Page 3 of 13 • Allowable Dock Water Extraction rate up to 25,353m3/day • Maximum Inlet / Discharge Water Temperature Difference 10°C • Absolute Maximum Discharge Water Temperature 28°C 4.0 Dock Cooling CFD Process Introduction To make an initial assessment of the potential thermal capacity of the dock a Computational Fluid Dynamics (CFD) model has been constructed. This model has been run transiently to determine the possible rate of temperature rise in overall water temperature under summer conditions and to assess the potential for short-circuiting between the intakes and outflows from the cooling system, Model The model represents the Outer and Inner Docks north as far as South Quay and assumes that the dock is 7.4m (24 feet) deep. It is assumed that the dock is completely enclosed with no transfer of water at South Quay. The extent of the model can be seen in Figures 5, 6 and 7 below. Heat transfer to and from the dock walls/floor and is based on a fixed temperature and a heat transfer coefficient of 0.133W/m2K. Heat transfer from the water surface is based on ambient temperature and heat transfer coefficient of 11.4 Wm/2K The model has been configured to simulate a warm summer period with a maximum temperature of 38°C reducing to a minimum of 20°C at night. Figure 5 - CFD Model Plan of Outer and Inner Docks Echelon - LCY10 - Dock Cooling Technical Note 041220 rev02.docx Page 4 of 13 Figure 6 - CFD Model of Outer and Inner Docks Figure 7 - CFD Model Intake and Outlets Assumptions and Boundary Conditions Flow and Intakes and Outlets • Water Flow Rate: 238 l/s • Supply Temperature: 28°C (fixed) • Nominal Heat Load (at 18°C intake): 10MW • Operation: System runs for 16 hours per day • Intake: Located 1000mm above bed • Outlet: Located 1000mm below surface. Echelon - LCY10 - Dock Cooling Technical Note 041220 rev02.docx Page 5 of 13 Ambient Condition Assumptions • Initial Dock Water Temperature: 18°C • Ambient Air Temperature Variation: Sinusoidal 20°C to 38°C • Dock Wall Temperature: 12.5°C • Dock Bed Temperature: 12°C CFD Results A transient simulation has been carried out for a potential 'worst-case' summer scenario. For this case it is assumed that the dock water is at a uniform temperature of 18C at the start of the simulation. Ambient temperatures for the seven-day period vary diurnally between 20°C and 38°C; for the purposes of this model the temperature variation is assumed to sinusoidal. The cooling system is assumed to be operating for sixteen hours per day during this period with the system switched off during the coldest eight hours. The results of the simulation are shown in the graphs in Figures 8 and 9. Figure 8 shows the temperature of the water entering the intakes (adjacent to the intakes when the system in not running). Also plotted in this figure is the cooling available during this period assuming that the supply temperature cannot exceed 28°C and the flow rate remains constant. Figure 9 shows the temperature in the dock at the three monitor points 1m below the surface shown in yellow in Figure 5. The results show that temperatures within the dock are typically rising at approximately 0.4C per day. At the inlets and the monitor point closest to the outlet vary noticeably during the day, rising during the day as warm water is pumped into the dock and is also warmed by the ambient air. This is followed by a period of cooling overnight as ambient temperatures fall and the cooling system is switched off. At locations further from the inlets the variation in temperature (Outer Dock and Inner Dock) is less marked however the overall trend in temperature rise is similar. If these conditions were sustained temperatures would be anticipated to rise at a similar rate (with heat transfer from the air will decreasing and heat transfer to the dock walls and floor increasing). On this basis temperatures in the dock adjacent to the outlet being approximately 24°C at the end of a two-week period. Echelon - LCY10 - Dock Cooling Technical Note 041220 rev02.docx Page 6 of 13 Summer Dock Cooling Intake Temperature 21.5 21.0 20.5 20.0 ) C ( e r 19.5 u t a r e p 19.0 m e T 18.5 18.0 17.5 17.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Elapsed TIme (Days) Intake Temperature Summer Dock Cooling Available 12.0 10.0 ) 8.0 W M ( e r u t 6.0 a r e p m e T 4.0 2.0 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Elapsed TIme (Days) Available Cooling Figure 8 - Predicted Intake Temperature and Potential Cooling Capacity Echelon - LCY10 - Dock Cooling Technical Note 041220 rev02.docx Page 7 of 13 Summer Dock Monitor Temperature 21.5 21.0 20.5 ) C ( e 20.0 r u t a r e 19.5 p m e T 19.0 r o t i n o 18.5 M 18.0 17.5 17.0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 Elapsed TIme (Days) Outer Dock Adajcent Inner Dock Figure 9 - Dock Monitor Point Temperatures The plots of flow from the outlets (Figure 9) show that warm water is rising towards the surface and away from the intakes and as a result there is only limited local recirculation of warm water; the increase in temperature seen at the intakes is largely due to the overall rise in dock temperature rather than localised effects.