By Daniel Marut & Michael Baselice, Comcast; Daniel Howard, George Gosko, Supriya Dharkar, Riebeeck van Niekerk & Tanner McManus, Hitachi; Gregory Baron, US Air Force (formerly with Hitachi)
Comcast contracted Hitachi Consulting to explore energy conservation measures (ECMs) at five headend sites in the West Division and five in the Central Division. The task involved an on-site energy assessment, development of computational fluid dynamic (CFD) models of existing airflow conditions, and recommendations of ECMs for each headend. The effort resulted in identification of three key measures that apply broadly to Comcast headends and hubs: airflow optimization, advanced HVAC controls, and replacement of older, less efficient and ozone-depleting refrigerants. Implementing these three measures would provide a 5-year energy savings opportunity for the ten sites of just over $1.5 million, with the annual savings being just over $300,000. Hitachi Consulting also assessed LED lighting opportunities at the ten headends. Implementation of LED lighting and controls would provide a 5-year energy savings opportunity for the ten sites of just over $300,000, with the annual savings being just over $60,000.
The motivation for the effort is the fact that cable headends and hubs often do not employ the most modern cooling practices such as contained equipment aisles with hot/cold aisle discipline, which is now common in most data centers. These headends and hubs consequently have far more cooling capacity that would otherwise be needed. The challenge is to explore what could cost-effectively be done in these facilities to achieve significant energy savings in a reasonable payback period.
Detailed cost proposals from a multitude of subcontractors across all sites was not feasible for the present effort. However initial estimates indicate that payback periods on the order of 3 years or under are feasible for most sites and with sites in states with higher utility rates paying back even sooner. The estimated range of implementation costs varies from approximately $40k to $160k, depending mainly on the size of the site. The true cost of implementation and payback period can only be determined from piloting the ECM implementations and measuring the actual energy savings obtained in the pilots.
In addition to potential energy consumption and cost savings benefits, there are also significant performance and customer satisfaction improvements that come from having more efficient, robust, and redundant cooling in headends and hubs. The benefits of the airflow optimization, advanced HVAC controls and refrigerant replacement also improves:
- power margin
- site resiliency towards R-22 phase-out by 2020
- normalizing inconsistent temperatures across the inlet side of the equipment
- reduces overheating equipment situations with no alarms
- adds HVAC redundancy
- and extends the useful life of the HVAC technology.
All of this leads to significant operating expense (OpEx) cost reductions and improved customer satisfaction via reduced IT equipment downtime.
More optimized cooling technology can also reduce the cost of future capital investments by lowering the tonnage of cooling required in replacement projects. The reduction of total energy consumption at headends and hubs can also enable more sites to be viable for alternate energy projects that seek to reduce Comcast’s dependence on the electrical grid and reduce the carbon footprint overall.
The specific energy conservation measures recommended in this effort include:
Air Flow Optimization (AFO):
- Increase utilization of blanking panels in all racks to limit the hot and cold air to a specificspace and limit infiltration within the racks
- Increase utilization of top of aisle containment to limit hot air recirculation and infiltrationover the top of the racks
- Increase utilization of end aisle containment (strip curtains or end panels/doors) to containcold aisles and prevent infiltration of cold air
- Redirect and/or add additional supply ducting to deliver cold air directly into contained cold aisles
- Reposition and/or add additional return ducting to facilitate hot air return to CRAC units
HVAC Controls:
- Add advanced HVAC controls to optimize key components of the HVAC system to reduceHVAC energy consumption by 15-25%
Refrigerant Replacement:
- Install next gen replacement refrigerants that extend the life of existing HVAC systems and can also increase efficiency and capacity over R-22 and R-407C by as much as 20%
- As part of refrigerant replacement and/or installation of advanced controls, “true-up” the HVAC equipment to address any performance issues and bring it back to nominal operation.
In this report, the results of detailed site visits, modeling and recommendations for each of the ten headend sites will be presented, followed by an analysis of the portfolio overall as well as conclusions and recommendations from the effort.
The ten Comcast headends covered by this report are:
West Division Sites
- Roseville, MN
- Hayward, CA
- Santa Clara, CA
- Beaverton, OR
- Burien, WA
Central Division Sites
- Stone Mountain, GA
- Atlanta, GA
- Jonesboro, GA
- Woodstock, GA
- Augusta, GA
The potential energy savings associated with implementation of these three ECMs at the 10 headend facilities is summarized in Table 1 below. The average utility rate for these 10 sites was $0.081, and as stated in the introduction, when all sites are considered, the total energy cost savings over 5 years was estimated to be $1.5M.