Datacenter Cooling Costs and Management

Cooling Costs

• Cooling can account for up to 63% of an IT department's power usage
• Electricity is measured in kilowatt-hours (kWh)
• A 100-watt light bulb uses 100 watt-hours of electricity in 60 minutes
• Ten 100 W light bulbs use 1 kWh of electricity per hour
• Companies worldwide spent approximately $29 billion on datacenter cooling in 2007, a 400% increase from 2000

Causes of Cooling Costs

• Cooling is a major component of power consumption and IT budgets
• Increased server and storage device deployment leads to increased power consumption
• Higher computing power in confined spaces increases heat density within racks
• Irregular heat loads in datacenters are exacerbated by poor heat management planning
• Overcooling datacenters can significantly increase costs

Calculating Cooling Needs

• All equipment in a server room generates heat
• Humidity changes in datacenters impact cooling needs
• Filtration and humidification can be more expensive than using a regular air-conditioning system

Economizers

• Water-side economizers use evaporative cooling to produce chilled water for datacenter cooling, especially effective in environments with temperatures below 55 degrees Fahrenheit for 3000+ hours per year
• Economizers can reduce chilled-water-plant energy consumption by up to 75%
• Reduce maintenance costs by minimizing or eliminating chiller operation
• Prevent contaminants and humidity changes from entering the datacenter
• Typically incorporated into chilled water or glycol-based cooling systems

On-Demand Cooling

• Provide temporary cooling when central air conditioning fails
• Two types: air-to-air and water-based
• Air-to-air coolers can be wheeled into rooms needing cooling
• Smaller air-to-air coolers use flexible ductwork and standard 110-volt outlets
• Larger air-to-air units are mounted outside buildings with cool air ducted through a window, operating on 208-to-230-volt circuits
• Water-based systems are larger units, using garden hoses to supply water for cooling

HP's Solution

• Dynamic Smart Cooling uses sensors to control datacenter temperature
• HP labs reduced datacenter cooling power from 45.8 kW to 13.5 kW using Dynamic Smart Cooling
• System adapts to changing workloads by adjusting cool air delivery based on computer needs
• Sensors on computers detect warming and signal air conditioners to deliver more cool air

Optimizing Airflow

• Air exchange rate is crucial for optimal cooling
• Normal offices require air exchange twice an hour
• High-density datacenters require air exchange 50 times an hour
• Insufficient air exchange can lead to overheating before cool air reaches equipment

Hot Aisle/Cold Aisle

• Equipment draws air from the front and exhausts air from the rear
• Cold sides of equipment are arranged together, hot sides face each other
• Allows equipment to draw in cool air, rather than preheated air from neighboring racks
• Cold aisles have perforated floor tiles to draw cooler air from raised floors
• Floor mounted cooling is placed at the end of hot aisles, not parallel to racks

Raised Floors

• Datacenters are built on raised floors 18 to 36 inches high
• Higher floors allow more air distribution under the floor
• Higher floors can disrupt day-to-day operations and increase height

Supply Air Directly to Heat Sources

• Cooling only the devices generating heat is more cost-effective than cooling the entire datacenter
• Use diffusers designed for datacenter cooling directly at equipment intakes
• Place diffusers near equipment intakes, avoiding heat exhausts
• Minimize air leaks through cable accesses in hot aisles
• Use computational fluid dynamics (CFD) models to optimize cooling unit placement
• Properly sized return plenums allow adequate air flow
• Under-floor supply plenums must be large enough to service equipment

Fans

• Fans consume significant power, especially when operating simultaneously
• Use low-pressure drop air handlers and ductwork for efficient airflow
• Use redundant air handlers at lower speeds for greater efficiency

Design for Your Needs

• Datacenters are often underutilized
• Upsize duct, plenum, and piping infrastructure for future scalability
• Use variable-speed motor drives on chillers and pumps for improved part-load performance
• Consider efficient techniques like medium-temperature cooling loops and fluid-side economizers
• Upsizing cooling towers improves chiller performance and economizers

Putting Everything Together

• Implement organization-wide considerations for efficient cooling
• Use life cycle cost analysis for decision-making
• Involve key stakeholders in project planning
• Document and clarify design decisions
• Set quantifiable goals based on best practices
• Introduce energy optimization early in the design phase
• Include integrated monitoring, measuring, and control systems
• Benchmark existing facilities and track performance
• Evaluate potential for onsite power generation
• Provide facility operation staff with site-specific training