A perfect storm of events descended upon Merck’s (then Schering-Plough) research facility in 2008 that has since lead to $150,000 in annual energy savings in chilled-water production. A corporate initiative to reduce energy consumption in its facilities led Merck to set new energy expectation standards; Merck’s S-6 research facility in Summit, NJ, was one of several projects identified as having great potential for energy and cost savings. A crucial facility, the S-6A chiller plant is a 7,800-ton plant that serves two buildings, a 500,000-square foot (sq ft) product development research facility and a new 300,000 sq-ft clinical manufacturing facility. It is therefore vital that both buildings have a reliable source of chilled water year round.
SITUATION ANALYSIS
Continual expansion on the campus had compromised the efficiency and operability of the central chilled-water system. In addition to high chilled-water system pressure and low differential temperature, the plant also experienced periodic reverse bypass flow. Karl Varnai (Summit engineering manager) and Tom Pagliuco (corporate energy director) recognized these as typical signs of inefficiency and energy waste; they also recognized the difficulty in resolving them in such a complex system with a diversity of chiller types, complicated piping, and multiple systems.
As a result, the two attended the New Jersey Pharma Food Energy Users Group (NJPFEUG) to investigate optimization solutions. Pagliuco, responsible for energy initiatives and for introducing ideas to Merck managers, went looking for new technology that could be piloted at the S-6 plant and expanded to other Merck facilities if successful; Varnai was seeking a solution to the energy management issues at his S-6 plant. tekWorx’ presentation on how variable flow chilled-water systems save energy left Pagliuco thinking, “I need this.”
“Our problems were a combination of hydronic design and operating control issues. Unfortunately, the control guys can’t deal with the mechanical issues without a consulting engineer, and the consultants can’t implement control systems,” said Varnai. “We really needed a partner that could deal with both at the same time, and that’s why we chose tekWorx.”
Prior to tekWorx’ involvement, the Summit research facility’s chilled-water system was based on a traditional primary-secondary hydronic design comprised of four-head primary CHW pumps, two sets of three variable-speed secondary pumps, and an open chilled-water bypass. All cooling coils had two-way valves, and the facility’s seven different size chillers (six centrifugal and one absorption, made by three different manufacturers) were controlled by a Trane Tracer system. The Tracer used a “make it work” control sequence that did not provide for energy optimization nor data collection for maintenance and performance monitoring. Due to the complex mix of chillers and wide range of loads, operators usually controlled the plant manually.
In addition, Merck’s business requirements dictated that the entire retrofit needed to occur during the plant’s winter shutdown, and, in order to get the project approved, Varnai and team needed to show a three-year financial payback (Merck’s minimum standard ROI for capital projects). This meant the facility needed to reduce CHW annual production energy consumption by at least 1,000,000 kilowatt-hours (kWh). Additionally, the growth of the facility necessitated the implementation of an automated system to free up staff and to communicate plant data to a facility management system. Varnai and the tekWorx team also determined the modifications should maximize the use of the existing control infrastructure to minimize both disruption and cost.
“The only physical modification to the plant was reducing the decoupler line size and adding a control valve,” said Patrick Scanlon, Merck’s senior project engineer. “Since there were no physical modifications to the plant, the payback was more attractive and a better sell to management.”
Working together with Merck, tekWorx audited the S-6 plant and its loads to identify opportunities to improve the overall system power per ton. tekWorx’ recommended solution consisted of three parts:
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Convert the S-6 plant to an integrated primary secondary (ISP) design
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Implement adaptive control techniques
- Modify building air-handling unit (AHU) valves
ISP CONVERSION
In contrast to the original primary/secondary design wherein two pumping loops share a common pipe, the first step in tekWorx’ energy optimization efforts was to convert Merck’s system to an ISP design.
With only one integrated pumping loop, water circulates through both the chillers and the load. The ISP system has a control valve in the bypass line that opens during light load conditions to ensure minimum evaporator flow. When this valve is closed (which is most of the time) there is no flow through the common pipe, so there is no degradation of the system Delta T.
CONTROLS
tekWorx next developed adaptive control algorithms for its CEO (control and energy optimization) system. The adaptive algorithms continuously optimize the system’s energy performance in real time, including the multi-mode pumping operation that is a fundamental part of the ISP design. In the multi-mode operation, pump speed is still regulated to maintain the remote Delta P set point (just like the primary/secondary system), but the pumps operate in different modes depending on the load. The algorithms were implemented on the CEO’s PLC-based hardware platform in order to control all equipment associated with generation and distribution of chilled water, optimizing the total system power per ton. Per the request of Merck’s engineers, tekWorx integrated the CEO chiller plant control system with the site’s Honeywell EBI facility management system to facilitate remote monitoring and maintenance.
AHU VALVES
The final step was replacing old “leaking” globe valves on the major AHUs with high–performance rotary valves. The new valves enabled better control of the flow through the AHUs, thus raising the return temperature and improving Delta T. And since the new valves have a 300:1 controllability and high Cv ratings, Merck could replace two globe valves on the large AHUs with a single high–performance rotary valve, thereby realizing significant cost savings.
RESULTS
Changing the plant’s piping from the traditional primary/secondary design removed its inherent energy inefficiencies and placed the system in a position to maximize the benefit from adaptive control. Further, the system pressure has been reduced from over 100 pounds per square inch (PSI) to approximately 75 PSI. The new AHU valves have further raised the return temperature and improved Delta T due to improved flow and efficiency.
Based on an average reduction of 0.20 kW per ton and annual cooling production of approximately 6 million ton hours, the former Schering Plough facility now uses 1,200,000 fewer kWh than it did a year ago. “ This is a major savings when you are paying $0.125 per kWh,” says Scanlon.
Merck has seen that the most important outcome of the tekWorx implementation has been the ability to continuously measure and verify plant efficiency. “That is the bottom line; [we’re] making chilled water and saving money,” says Scanlon. “Did I hear someone say Kaizen?”
Better yet, the implementation was actually less than expected. “One of the things we really liked about tekWorx was that they didn’t want to redo our entire campus control system. They simply wanted to help us optimize the performance of our chilled-water system. That alone provides us a lot of savings,” said Varnai. Tekworx replaced the Trane CPU with an Allen-Bradley PLC and integrated it with the existing networked devices, including VFDs, chiller control panels (York, Carrier, and Trane), and hardwired I/O controllers. Merck’s chillers are now sequenced based on efficiency. In particular, constant speed chillers are used only when they can be fully loaded; the new variable-speed chiller is modulated to meet the demand in between steps. All pumps are variable speed, and they are sequenced to meet the flow demand at the lowest total pumping energy.
As a result of tekWorx working with the plant’s existing systems, the payback result was recognized in approximately two years instead of three; the project cost was $300,000 with annual energy savings of $150,000. This cost savings was realized with minimal mechanical modifications to the plant.
“A lot of energy management is visibility,” said Pagliuco. Merck, like other operators, experienced a catch-22 in trying to establish some type of baseline for plant energy consumption that’s best summed up by Pagliuco. “You don’t know what you’re missing until you meter it, but it’s hard to justify metering without knowing what you’ll save.”
The ability to record flows, power, pressures, temperatures, VFD speeds, etc., is vital for improving plant performance. Merck’s engineers are pleased not only with the financial savings and lower temperatures that were delivered as promised, but with the insights they’ve gained from having reliable data with which to work. Installing the tekWorx system now enables authorized personnel to remotely monitor and adjust plant operations via a VPN connection; this feature not only reduces maintenance costs but also allows issues to be solved much more quickly.
Scanlon asserts, “The graphical overview display allows the mechanic to view the system as a whole and how changes impact the system.” If a problem should arise, Scanlon can look at the system from his desk or his home PC, and tekWorx can log onto the system to assist with troubleshooting. If necessary, tekWorx engineers can change a program and download it directly to Merck’s controller. “As an additional safeguard we had tekWorx give us the capability to switch back to a [traditional] primary/secondary system,” says Scanlon, “but we have never done [that] since making the switch to integrated primary/secondary.”
The installation of the tekWorx system has also significantly lessened the impact of day-to-day work. “Before the installation of the tekWorx system, HVAC mechanics spent a good deal of time "making" the plant work; a good majority of the equipment was operated in manual mode, even though there was a Trane Tracer control system.“ says Scanlon. “A great deal of energy was wasted in order to meet set-point temperatures and differential pressures. In contrast, today you will find a mechanic in the control room monitoring plant status. All hand/off/auto changes can be made from the tekWorx computer.”
“We got what we were promised,” concludes Pagliuco.
