passive rdhx as a cost effective alternative to crah air ... · passive rdhx as a cost effective...
TRANSCRIPT
Passive RDHx as a Cost Effective Alternative to CRAH Air Cooling
Jeremiah Stikeleather
Applications Engineer
Passive RDHx as a Cost Effective Alternative to CRAH Air Cooling
While CRAH cooling has been a common data center cooling solution, OPEX for RDHx cooling can be better at minimizing today’s energy consumption and operating costs. This will have increasing significance as we look to the future and interest in sustainability grows.
Agenda
• Industry Terminology
• Benefits of the Passive Rear Door Heat Exchanger
• The Study: Comparing 3 Cooling Designso Traditional CRAH Units
o RDHx’s with a Primary Piping Manifold
o RDHx’s with CDU’s and a Secondary Water Loop
• Summary of the 3 Design Alternatives
Industry Terminology
CRAH – Computer Room Air Handler
CRAC – Computer Room Air Conditioning
RDHx – Rear Door Heat Exchanger
IRC – In Row Cooler
CDU – Coolant Distribution Unit
CAPEX – Capital Expenditure
OPEX – Operating Expense
Close Coupled Cooling – Cooling that is adjacent to server racks
Greenfield Building – Construction of a building on greenfield land where there is no work constraints
Front of Enclosure
Rear of Enclosure
Benefits of the Water-Cooled Passive Rear Door Heat Exchanger (RDHx)
• Takes up very little space
• Air-to-Water Heat Exchanger
• Close-coupled cooling solution
• Removes the heat at the source
• Very little energy required
• Significant energy reduction versus a typical CRAH solution
• Heat exchange process occurs at rear of the rack
• Water thermal capacity is 3400 times greater than air
• Significant reduction in maintenance costs
93°F
72°F
91°F
73°F
Benefits of the Water-Cooled Passive Rear Door Heat Exchanger (RDHx)
The Study: 3 Cooling Designs Designs Compared:
• Design 1 – Traditional 30-Ton CRAH Units
• Design 2 – RDHx’s with a primary piping manifold system
• Design 3 – RDHx’s with Coolant Distribution Units
and secondary water loop
Study includes:
• All aspects of deploying solutions in a 1 MW Data Center
• Supply and installation of cooling system
• Electrical connections, valves, piping
• Building monitoring integration system
• Leak detection, smoke/fire detection
• Condensate removal
The Data Center Configuration:• 1 MW of IT power in a raised floor environment
• 5,000 sq. ft. white space
• Planned deployment of 177 IT enclosures
• Infrastructure for a space loading of 200 watts /ft2
• 28 ft2 per IT enclosure (assume 5.7 kW / rack)
The Benchmark Air Cooling System:
• Chilled water Computer Room Air Handlers (CRAHs).
• (12) 30-Ton operating units around perimeter
• CRAH unit air discharge temperature 68°F to 70°F
• Two additional CRAH units installed for redundancy
• Cold air discharged under an 18 inch raised floor
• Hot aisle-cold aisle arrangement
The Benchmark Air Cooling System:
• CRAH running at a reduced load of 80% (4.6 kW)
• Chilled water for the CRAHs (100% water, no glycol)
• Branch connected from a main chilled water loop running external to the white space
• Chiller, water supply, and related energy costs not included in any of the cooling designs
Design 1 – Traditional CRAH Units
Fourteen 30-Ton CRAH units• 12 active, 2 standby
Assume 25% CRAH performance reduction• Large area with unpredictable airflow
• Obstructions (columns, cable runs, etc.) alter airflow
• Wasted air (openings in tiles that do not provide direct access for rack intake)
White space consumption and the required service clearance is factored in
• Footprint required by CRAH system complicates future expansion of IT enclosures
Design 1 Summary – Traditional CRAH Units
Cost includes:
• Supply and installation of CRAH units
• Space fit-out
• Fire protection/suppression systems required for access and CRAH
footprint
De-rating published sensible cooling by 25% considered conservative
due to the
built-in inefficiencies of CRAH based air cooling systems
Power consumption much higher due to fans, humidification, and reheat
functions
Increased rack power density will force a change in cooling infrastructure
– more CRAHs, supplemental cooling, hot aisle/cold aisle containment
Design 1 – Traditional CRAH UnitsCost Summary
Design 2 – RDHx with manifold system• Dedicated chiller
• 177 RDHx
• Chilled water distribution from prefabricated manifold system
• 2 CRAH units for humidification control and room cooling backup
• CAPEX reduced by not using additional pumps or plate-and-frame heat
exchangers
Design 2 – RDHx with manifold system Piping manifold alternatives:
• Manifold and pump tapping into bypass/mixing line• (Manifold return water discharges back into the bypass)
• Manifold and three-way valve tapping into supply and return lines• (Mixing building return water with supply water to achieve higher supply water temperatures for
the RDHx)
• Similar to methods used in the radiant piping industry
Design 2 – RDHx with manifold system
Controls for the proposed system rely on supply air temperature
sensors for the racks and their corresponding RDHx that is
connected to the manifold, and a modulating control valve or circuit
setter at the manifold return
Design 2 Summary – RDHx with manifold
CAPEX comparable to CRAH design (Design 1)
OPEX for RDHx is minimal• (About 3% of the total power consumed by CRAH units)
RDHx units are passive
Small RDHx whitespace footprint • Reduce overall building footprint
• Greenfield project savings
• Construction savings for future expansion
RDHx ROI within first year of operation
Over 3x IT expansion, 5.7 kW to 18 kW / rack(RDHx nominal cooling capacity 18 kW)
Design 2 – RDHx with manifold system Cost Summary
Design 3 – RDHx with CDU and secondary water loop
• 4 Coolant Distribution Units (CDU’s)
• CDU is floor-mounted device – heat exchanger, pumps, controls, distribution manifold
• CDU connects to water from chiller (or cooling tower)
• 2 CRAH units (Humidity control and room cooling backup)
• No condensate (Temperature/humidity sensor regulates secondary loop temperature 2 degrees above dew point)
• The RDHx water loop is isolated from primary water loop
• CDU power consumption 3.7 kW each
Design 3 Summary – RDHx with CDU
• CDU increases CAPEX
• Low OPEX cost CDU pumps use 15% of power for CRAH units
• Break-even point is in Year 3
• Design 2 and 3 are “future proof”5.7 kW racks can grow up to 18 kW
Design 3 – RDHx with CDUCost Summary
Summary
• At 5 kW per rack, CAPEX for RDHx and CRAH cooling
approximately equal• (CAPEX could be further reduced by implementing alternating RDHx’s – CAPEX savings up to 25% compared to
populating each rack with an RDHx)
• OPEX is significantly reduced with RDHx designs
• Reduced energy consumption
• Reduced demand charges
• Reduced maintenance costs
• RDHx allows for future growth without new construction costs
• RDHx performs well with elevated water temperatures
• Minimizing chiller energy usage
• Reducing chiller OPEX
Summary
• OPEX savings increased using waterside economizers•(Free cooling window is increased using elevated water temperatures)
• Hybrid system including some CRAH units with RDHx adds redundancy for greater system availability
• Increasing rack density to 18 kW can minimize infrastructure space
(CAPEX savings 30-40%)
Study Conclusions
• A common misconception that liquid cooling is too expensive to deploy disproved
• CAPEX for liquid cooling and traditional air cooling is approximately the same at 5 kW / rack
• Increasing energy costs encourage data center owners and operators to consider liquid cooling
• Passive liquid cooling enables expansion and flexibility at a lower, incremental, capital expenditure
Future Considerations
• A similar study done by a 3rd party consulting
engineering firm is comparing RDHx’s to IRC’s
• 4 MW Data Center, 5000 sq. ft.
• IRC CAPEX $4.5M, 6 MW cooling capacity
• RDHx CAPEX $2.5M, 7.5 MW cooling capacity
Thank You
Patrick GiangrossoGeneral Manager
(603) 479-4806