Quick savings solutions

Design considerations like variable frequency drives are approaching the cost of motor starters, which allow for choices that weren't possible until now.

11/19/2012


There are some simple design considerations that will have an impact on energy or operating cost savings with minimal or no increase in first cost. The cost of variable frequency drives (VFDs) is approaching the cost of traditional motor starters. Originally the drives provided a means of saving energy because they would maintain a high level of efficiency while reducing motor speeds and using less power. These are traditionally used in variable air and water flow systems. However, use in some constant flow applications has proven this cost-effective in some circumstances: by using a VFD in lieu of a motor starter, you can save air balancing costs due to sheave and belt changes. This translates to low first cost, less labor, and maintained system efficiency.

Hot and chilled water system pump configurations provide opportunities for quick investment returns. Most pumping configurations will use dual pumps with one unit being used as standby; each pump provides 100% redundancy. In a variable flow configuration, rather than selecting two pumps at 100% redundancy, evaluate the option of operating two pumps in parallel. There is an immediate savings due to a reduction in pump size. Proper selection of the pumps would result in the ability of a single pump to provide as much as 75% total system flow should there be a failure.

Selecting chillers and cooling towers presents several opportunities to keep operating costs at a minimum with few additional costs. Chiller capacity and efficiency is a function of condenser water temperature—colder condenser water temperature will provide a slight increase in unit capacity. The water temperature is a function of the cooling tower size; as with most equipment, there are nominal unit casing sizes. The actual tower performance is a function of the amount of surface area or fill and fan size. Maximizing the amount of surface area within a given tower casing will reduce the condenser water temperature, reduce the tower fan operation, and increase chiller efficiency. This additional first cost becomes negligible within the total system cost and provides maximum benefits.

There are rooftop applications that present almost immediate investment returns. Most rooftop units struggle with large quantities of outside air. This holds true for the heating and cooling side when large quantities of ventilation are required. The choice is either to split the load with multiple units or to move to a larger single unit. In either case, there is an increase in the first cost and usually a loss of unit efficiency.

Installing an air-to-air heat recovery unit between the building exhaust and ventilation air is a simple means of recovering expended building energy and avoiding higher unit first cost and operating costs. Certainly equipment efficiencies and added installation costs are the most obvious, but there are also opportunities when selecting a primary fuel source. The best type of energy is free energy, although there is a premium to be paid for harvesting solar, wind, and in some instances geothermal energy. In most cases there are programs that will help fund the higher first cost through grants or tax incentives. Even with offset dollars, these systems usually have a payback period of 10 to 15 years, which is close to the useful life of the system. If the decision is based purely on economic factors, the design and installation of these systems would never occur.

Besides free energy, there is another opportunity to save operating costs. The comparison of natural gas, fuel oil, and electrical costs is commonly overlooked. Rate structures vary by utility and region, but do provide a method of adding value without increasing first cost. As an example, natural gas or fuel oil would be the most logical heating source in cold climates; however, in some regions this service may be unstable or volatile with respect to availability and cost. Electricity may be a viable solution especially if there is ample capacity as provided by either a nuclear plant or hydropower. The simplest method to compare the values is to break down the units into dollars per Btu.


Peter D. Zak is a principal with Graef-USA Inc., where he manages the MEP group. He is a member of NCEES and is on the editorial advisory board of Consulting-Specifying Engineer. He was an adjunct assistant professor at the Milwaukee School of Engineering for 20 years and is a registered professional engineer in 24 states.



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
World-class manufacturing: A recipe for success: Finding the right mix for a salad dressing line; 2015 Salary Survey: Manufacturing slump dims enthusiasm
2015 Top Plant: Phoenix Contact, Middletown, Pa.; 2015 Best Practices: Automation, Electrical Safety, Electrical Systems, Pneumatics, Material Handling, Mechanical Systems
A cool solution: Collaboration, chemistry leads to foundry coat product development; See the 2015 Product of the Year Finalists
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Getting ready for industrial IoT; Visualizing the (applied) automation continuum; Preventing VFD faults and failures; Using wireless for closed-loop applications
Migrating industrial networks; Tracking HMI advances; Making the right automation changes
Understanding transfer switch operation; Coordinating protective devices; Analyzing NEC 2014 changes; Cooling data centers

Annual Salary Survey

After almost a decade of uncertainty, the confidence of plant floor managers is soaring. Even with a number of challenges and while implementing new technologies, there is a renewed sense of optimism among plant managers about their business and their future.

The respondents to the 2014 Plant Engineering Salary Survey come from throughout the U.S. and serve a variety of industries, but they are uniform in their optimism about manufacturing. This year’s survey found 79% consider manufacturing a secure career. That’s up from 75% in 2013 and significantly higher than the 63% figure when Plant Engineering first started asking that question a decade ago.

Read more: 2014 Salary Survey: Confidence rises amid the challenges

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.