Literature Review: Data Center- Physical, Environmental and Energy Footprint

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▼This page is a literature review.Feel free to edit this page and add sources and summaries.

Any comments are welcome on the discussion page including additional resources/papers/links etc. Papers can be added to relevant sections if done in chronological order with all citation information and short synopsis or abstract. Thank You.

• data centers are responsible for >2% of US total electricity usage
  • between 25% and 35% of worldwide consumption of DC (30 billio watts) consumed by US DC
  • half of the power used in cooling the electronics
• difficulty associated with recovering and reusing low-quality waste heat
  • capture temperature is limited by the temperature limits of the electronics, which remain below 85 °C in most cases
• most servers operate rearely at their max cap
  • majority operates at or below 20% of max cap
  • when the system is idle, 60-100% of the max power drawn from grid
  • Many data centers feature servers with power densities in excess of 100 W/cm2 and even up to as high as 200 W/cm2, which means that a rack with a 0.65 m2 footprint has heat dissipation requirements as high as 30 kW, or roughly 30 times higher than the amount of energy dissipated by a typical rack with the same footprint in 1990
• Physical organization
  • a rack is a standard metal frame or enclosure
  • height: 78 in ; width: 23-25 in; depth: 26-30 inch >>> rack
  • standard racks are arranged in rows at a pitch of approx 2m
  • the height or thickness of modular asset mounted in a rack is described by 1U == 1.8 in
  • a typical full size rack can take a tootal of 42 of 1U assets
• Thermal load and temp limit
  • the energy flux dissipated by traditional data centers is in the range of 430–861 W/m2, the energy flux dissipated by the newer generations of data centers has been increased at least by 10 times (6458–10,764 W/m2)
  • the capacity of conventional HVAC systems for similar size rooms (40–86 W/m2)
  • see table 1 (Heat load and physical size of microprocessors/cores in recent literature)
  • an individual hard disk can dissipiate powers as high as 12W and mass storage devices consume up to 20-30% of total power supply
  • The table indicates that for standard servers the total power consumption is typically in the range between 300 and 400 W, however, for highly populated servers the power consumption can reach up to 525 W.
  • For blade servers, the power consumption was around 250 W each
  • per-rack power consumption is about 7 kW
  • power consumption of a high performance fully utilized rack is on the order of 10–15 kW
  • power dissipated by racks loaded with blade servers can approach 21 kW
  • ASHRAE anticipates power consumptions of 60 kW for a single rack filled with extreme density communication equipment and 35 kW for a single rack filled with extreme density computer servers
  • the amount of heat dissipated by a singlr 0.6m x 0.6m rack was between 0.26 and 1.3kW
  • 250 kW power dissipation for liquid cooled systems and 60 kW for racks with air-forced cooling systems
  • designing cooling system for today's data centers the assumed heat capacity for the racks is in the range of 10–15 kW, however, if rack is filled with supercomputer servers, it can generate in excess of 60 kW of heat.
  • thermal management systems are shifting from traditional air cooling to liquid or two-phase cooling
  • a data center with an efficient air cooling system, the cold air is typically supplied at 25 °C and the exhaust air leaves the room and returns to CRAC at 40 °C
  • see Table 5. Air-cooled data center heat sources and streams in recent literature
  • 0.5 MW raised floor data center housed 50 racks with a cooling flow rate per rack of ~1500 CFM and average 10.5 °C temperature increase from bottom to top of every rack
  • improving data center energy efficiency using variable speed server fans studied a data center with 28 extremely high power density racks with a maximum air flow rate for each rack of 2400 CFM, cold air temperature of 15 °C and a maximum temperature rise of 40 °C
  • in the report published by the Silicon Valley Leadership Group temperature ranges of 10–13 °C and 15.5–18.4 °C were reported as standard for the supply and return water temperature by CRAC
  • see Table 6. Summary of “typical” air-cooled data center heat sources and streams
  • see Table 8. Summary of “typical” water-cooled data center heat sources and streams
• The use of remotely siting servers in individual homes to provide domestic heating is referred as a “Data Furnace” by Liu et al. [73]
• 6% of total US energy usage goes to home heating according to IEA
• District heating is more suitable for the higher waste heat capture temperatures of liquid cooled servers (up to 50–60 °C rather than 35–45 °C), but does not require the remote siting of servers
• a 2 MW data center installed in an empty WWII shelter in Helsinki provides enough water heated by waste heat to heat 500 homes or 1000 apartments [75]
• The required waste supply temperature when a heat pump is used is in the range of 22–92 °C
• Intel [78] developed a heat recovery chiller to capture the waste heat in a legacy data center
  • consists of an evaporator and condenser
  • waste heat is captured through a plate heat exchanger which then transfers the heat to an evaporator
  • heat pump system is transfer the heat from the lower temperature water flowing in the evaporator to the higher temperature water flowing in the condenser
• the optimum location for legacy air cooled DC to install a heat exchanger to extract waste heat and repurpose it in district heating or hot water production is at the return to CRAC unit or at the chiller water return ( temp as low as 35C)
• the easiest location to capture waste heat is at the cold plate loop heat exchanger in water cooled DC ( temp range 60-70C)

• this paper investigated the feasibility of Data Furances , which are micro-datacenters, on the order of 40 to 400 CPUs, that serve as the primary heat source for a single-family home [a 1700 square foot residential house that is moderately insulated and sealed with a heating setpoint of 21°C (70°F)]
• 3 benefits of DF: 1) smalled footprint 2) reducesd total cost of ownershiop per server 3) close prox. to user
• computer server>> metal box>> converts electricity into heat
• exhaust air temp > 40-50C >> too low to regerate electricity efficiently
• proposal >> electric resistive heating elements with silicon heating elements
• A mid size data center of 100kW can be hosted inside a building and the waste can be used to heat thhe building
• DFs have essentially no additional cooling or air circulation costs since the heat distribution system in the house already circulates air
• One disadvantage of DFs is that the retail price of electricity is usually higher in the residential areas by 10% to 50% than industrial areas