Energy Management: A Strategy for HVAC Savings
By Carl Crow - April 2008 - Energy Efficiency
Energy-efficiency concerns remain a top priority for institutional and commercial organizations. Managers are ramping up their efforts to find savings related to heating, ventilation and air conditioning (HVAC) systems, including chillers, boilers, and air-handling components. Among the proven strategies at managers’ disposal for achieving cost savings is retrocommissioning, which helps identify energy-saving opportunities.
The process offers managers a range of benefits, especially when applied to components that commonly offer potential savings. The real challenge for managers is turning the results of retrocommissioning into bottom-line benefits.
Determining the Scope
After a building is constructed and occupied, it is common for energy use and costs to increase as the building ages. This happens sooner for some facilities than others, depending on the original design, quality of construction, attentiveness to the test and balance process, original commissioning efforts, and level of maintenance.
Retrocommissioning is a process intended to systematically identify the most wasteful inefficiencies that technicians can cost-effectively correct, and to restore or in many cases improve the building’s original level of energy-efficient operation. Factors that influence the scope of retrocommissioning work typically include the owner’s budget, the level of inefficiency to be corrected, the operating strategies employed to control energy use, and the commitment of the project team to the project’s initial and ongoing success.
Retrocommissioning involves several distinct phases. In the initial planning phase, the retrocommissioning agent, who might be an outside consultant or in-house champion of energy-efficiency improvement, identifies the building systems to be analyzed. Next, the agent performs an energy audit to determine the way those systems are supposed to operate and generates a prioritized list of operating deficiencies, also called energy-conservation measures.
These measures fall into two categories: low- or no-cost measures and those requiring a substantial investment, such as major equipment replacement.
The agent then conducts an energy and economic analysis to determine which energy-conservation measures are most cost-effective from a life-cycle standpoint.
Finally, the agent prepares a summary report and presents the results to the owner’s management team to determine the size of the investment in the project. In some cases, the investment might be substantial enough to require outside financing, such as through an energy service company (ESCO). An ESCO can provide a turnkey solution, financing the project costs out of the savings — a strategy known as performance contracting. The ESCO generally offers some form of guaranteed savings during the term of the contract.
Once a final scope and budget are set, implementation begins. In this phase, technicians correct the highest-priority deficiencies and recommission the system by starting it and checking for proper functionality and conformance to the design intent.
In the project closeout, or handoff, phase, the agent reports improvements to the owner, and facilities management personnel receive training in sustaining proper operation and maintenance of the modified systems.
A final long-term measurement and verification phase then begins to monitor the drop in energy use over time to ensure efficiency improvements last throughout the change of seasons, as well as to identify opportunities for further enhancements.
Numerous building systems are typical candidates for cost-effective retrocommissioning. Among the most commonly retrocommissioned systems, and the possible benefits, are these:
• reduce excessive lamp wattages through lamp replacement
• program lights to go off during unoccupied periods.
• recalibrate sensors
• correct improperly functioning control sequences
• eliminate excessive, simultaneous heating and cooling
• reset out-of-range or inappropriate setpoints during unoccupied periods
• repair disabled free-cooling economizers
• eliminate equipment running excessively or inefficiently
• reprogram equipment operating schedules to match building use
• control building pressurization to prevent unwanted infiltration and exfiltration.
• Balance air and water systems that are out of balance
• repair variable-air-volume boxes that are not working properly
• tighten loose fan belts
• repair leaking control valves
• replace leaking damper seals
• repair or replace malfunctioning variable-speed drives
• seal ductwork to minimize leaks
• reduce excessive air-change rates.
• repair door and window seals to prevent excessive infiltration of unconditioned outdoor air and excessive exfiltration of conditioned air
• replace inefficient glazing or install solar-control film
• provide internal or external shading devices to control solar-heat gain
• install additional thermal insulation where needed to reduce heat gain and loss.
Pay Close Attention
The key to success for any retrocommissioning project is to plan the work, then work the plan. Lack of attention to any of the following critical actions can lead to setbacks and possibly failure to realize the predicted savings in energy and cost:
• Involve the facility maintenance staff throughout the project.
• Benchmark the facility’s energy use and demand. Collect utility records, weather data, and equipment logs. Create a baseline building-load profile, and compare it to similar facilities. A useful tool is Portfolio Manager software available from the U.S. Environmental Protection Agency’s ENERGY STAR program.
• Assign an in-house project manager.
• Establish the funding mechanism — internal investment, utility rebates, performance contract, etc.
• Carefully select retrocommissioning service providers, including the engineer, contractor, testing and balance firm, and retrocommissioning agent.
• Measure and verify results by taking meter readings and tracking utility bills.
• Establish a program of continuous monitoring and improvement, sometimes referred to as continuous commissioning.
Case Study: Shriners Hospital
A retrocommissioning project at Houston’s Shriners Hospital for Children, an ENERGY STAR-labeled building each year since 2003, offers a textbook example of the way a successful project can yield significant bottom-line results.
The hospital, a 248,775-square-foot facility that opened in 1996, is a non-profit, acute-care facility funded entirely by donations from individuals and corporations. In 1997, Shriners’ energy-management team, consisting of an energy manager, four engineers, a technician, a biotech professional, and an administrative assistant, started a retrocommissioning project to reduce the hospital’s utility costs by 40 percent.
When managers with Shriners first benchmarked their facility using Portfolio Manager, it scored a below-average rating of 42 out of 100, based on 1996 data. Shriners began investigating energy-efficient strategies in 1998 and instituted several low-cost operations and maintenance opportunities, as well as made two technology upgrades that improved its rating to 75 within two years.
The energy-efficiency upgrades implemented at Shriners addressed a series of specific issues. For example, technicians installed light-emitting diode (LED) exit signs that use one-tenth of the ampacity of a standard fluorescent sign. They also installed occupancy sensors in public areas and mechanical timers in non-public areas to turn off lights in unoccupied areas.
They also balanced air and hydronic water systems throughout the hospital, decreasing electric-power use by 68,900 kilowatt hours in nine months, and they installed energy-efficient motors and variable-frequency drives.
Related to the other HVAC components, they installed new, energy-efficient motors and two new chilled water pumps. They also installed an off-hours air conditioning system to serve one section of the hospital so rooms are air conditioned by an 87.6-ton air-handling unit (AHU) fed from the central plant when the section is fully occupied and by a 1.5-ton dry-expansion (DX) split system when it is not occupied.
With the enhanced DX split system in place, they interlocked the new air conditioning unit with the AHU through the energy management system, allowing only one unit to operate at a time. HVAC certification and refrigeration maintenance were essential to optimize performance.
The Bottom Line
Shriners’ energy manager also maintains and regularly reviews all of the organization’s energy bills, savings, anticipated savings, future technologies for investment, and opportunities for additional energy savings.
The hospital’s dramatic steps resulted in a 24 percent reduction in energy consumption that went directly to the organization’s bottom line. This result prompted executives to request the energy manager investigate energy-saving opportunities for the organization’s headquarters in Tampa, Fla.
Shriners’ energy savings translated directly into increased funding for the hospital’s core mission, which is to provide quality pediatric and orthopedic care to children.
Delbert Reed, director of engineering and maintenance at Shriners Hospital for Children, summarized the benefits of the retrocommissioning project this way:
“While some facility managers don’t think that they have the funding or time necessary for energy-saving measures, we believe that they can’t afford not to look at opportunities to increase their efficiency. Our technologies and operational changes save a significant amount of money every month — money we can use to further the mission of our hospital.”
Carl Crow is a vice president for Smith Seckman Reid, www.ssr-inc.com. He has 28 years of experience in mechanical engineering for health care, laboratory, and higher education facilities.