Consulting-Specifying Engineer - January 2008 - (Page 51) To answer this, engineers performed an analysis with Chicago as a representative climate. This type of climate can yield large energy savings, but also results in many hours that fall below the ASHRAE recommended minimum humidity levels. To gain a better understanding of the energy savings potential, a parametric analysis was conducted to evaluate how different indoor design temperatures affects both energy use and indoor humidity levels; see Figure 1 for details. Based on this analysis: •Designing for higher discharge air temperatures (cold-aisle) and higher return-air temperatures (hot-aisle) will result in significant annual electricity savings. •To achieve the maximum projected savings, the indoor humidity levels must be allowed to fall far below current recommendations of ASHRAE and other industry organizations. •Using traditional isothermal humidification or more energy efficient adiabatic humidification processes, the lower limit humidity level can be increased to an acceptable level, but the potential energy savings will be reduced. One conclusion drawn from the modeling described in this article is that there needs to be further research on the leakage of data center facilities. From stateof-the-art facilities to data-center spaces built within existing office buildings, and data centers constructed within converted warehouses and industrial buildings, there is likely a spectrum of leakage rates and causes. Compared to state-of-the-art facilities, leakage is probably worse in converted manufacturing or warehouses spaces, where envelope integrity may not have been a priority during the design and construction of the original facility. These facilities could potentially be the most chal- lenging in maintaining indoor temperature and humidity levels. Knowing more about the scope and scale of data center leakage could encourage owners to tighten up their facilities and to budget more for better envelopes on new construction and conversions. Another important area of research required comes from the computer manufacturers. Building owners, CFOs, and CIOs need accurate data as to the trade-offs that come from expanding the temperature and humidity tolerances related to possible decreased lifecycle of computer equipment compared to annual electrical utility savings. With this data, it will be possible to accurately develop lifecycle cost analysis and reliability studies. Bill Kosik is Chicago managing principal with EYP Mission Critical Facilities Inc. and is a member of CSE’s Editorial Advisory Board. Specify quiet Our new outdoor generator sets (10-200 kW) are powerfully quiet. Powerful enough to equip cell tower sites, fire stations, healthcare facilities, schools and hotels with reliable, low-emissions standby power. Quiet enough to easily meet local ordinances. Make a sound decision. Specify enclosed generator sets from Cummins Power Generation Inc. Register to win Bose® noisecancelling headphones at www.cumminspower.com/quietpower © 2007 Cummins Power Generation Inc. All rights reserved. Input #226 at csemag.com/quickResponse Consulting-Specifying Engineer • JANUARY 2008 51 http://www.cumminspower.com/ http://www.cumminspower.com/ http://csemag.com/quickResponse
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