While efficiency is often cited as a key factor in selecting individual pieces of heating, ventilation, and air conditioning (HVAC) equipment, this may not be the best way to achieve the most efficient and optimized building performance. This may seem counterintuitive, but there are many variables that contribute to optimized building performance. It depends on how the building is being used and occupied, how the various pieces of equipment in the building interact and work together, and what the goals are for the facility.
In many industrial and manufacturing buildings, system redundancy and optimization are key priorities on that list. This makes it important to look beyond the efficiency of a single piece of equipment and instead consider building performance and efficiency — in keeping with the priorities for the facility — and seeing the whole as greater than the sum of its parts.
A Better Approach
Rather than asking which individual pieces of equipment are the most efficient, the question becomes how to make the entire system more efficient, while also ensuring it meets the priorities identified for the facility. Resisting the urge to go granular immediately — and instead taking this systems approach up front — helps maximize efficiency and performance of the entire building.
It starts with understanding what you want to achieve in your facility, and what building outcomes are being sought. Is the driver reliability and redundancy, efficient performance, a sustainability goal, or other benchmarks or regulations?
Next, consider how the building will be run and when it will be occupied. The needs of a manufacturing facility differ greatly from the needs of a hospital. Knowing how the building will be used provides a better understanding of full-load and part-load performance, which helps determine what equipment and systems are best suited for the building.
From there, move backward into what building systems best match these goals and needs. In addition, it’s important to look at how the various building systems — from plumbing, lighting, security, and HVAC — interact and best work together to optimize building efficiency.
The issue of system redundancy and optimization also plays a key role in this process. Emergency power sizing, peak-demand utility charges, and power blackouts and brownouts are all issues to consider for manufacturing and industrial facilities. Certain systems are better suited to provide redundancy than others. For example, chiller-based thermal storage systems run the chillers at night when energy prices, cooling loads, and outdoor temperatures are lower. By moving some of the system redundancy into thermal storage rather than excess or oversized chillers, systems using air-cooled chillers with ice storage have increased emergency cooling capacity with competitive or lower first cost, and lower maintenance and water costs.
Consider these key strategies that can help in successfully implementing a systems-level approach in building design:
- Understand the utility cost structure. Don’t choose systems and equipment without a clear understanding of the utility rates and structure for a specific building and location. Understanding the utility rate structure, which often includes consumption charges and demand charges, allows for a more accurate analysis of building performance based on how the building will be occupied and used. In some areas, demand charges can comprise up to 75 percent of the monthly utility bill. Knowing this can help in choosing the most efficient system from a utility bill perspective, such as taking advantage of the load-shifting capabilities of a thermal storage system. It’s often helpful to consult a partner who offers expertise in building systems and equipment, as well as in utility rate structures and billing.
- Consider the total budget. Selecting the building systems and equipment that will best provide optimized efficiency and performance for a specific building also hinges on the budget — both up front and long term for staffing and maintenance. Selecting a system that requires less long-term maintenance can help save staffing costs in the long run.
- Understand the needs. Asking the right questions about how the building will be used and occupied is a critical consideration in choosing the systems and equipment that will provide the most efficient and optimized performance.
- Use a modeling program. Using a modeling or energy simulation program in building design contributes to sound decision-making and can pay off in improved energy efficiency and performance. Modeling allows you to optimize the systems from an energy and utility bill perspective before construction even begins. It’s important to model against the potential optimized performance of the whole building and its systems, rather than modeling against performance of individual components.
Consider this example of a major automotive manufacturer working to develop a new district cooling and heating plant for its campus, which consists of a combination of offices, production, and laboratory test facilities that produce large quantities of heat. A primary performance goal was to create a LEED Gold or better solution.
Given the varying demands of the different building types — along with the desire for high energy-efficiency performance — a whole-system approach was followed. The consulting engineer chose to work with a major equipment provider to consider and evaluate all design options.
While efficiency is often cited as a key factor in selecting individual pieces of heating, ventilation, and air conditioning (HVAC) equipment, this may not be the best way to achieve the most efficient and optimized building performance. It was a collaborative process from the beginning, involving the consulting engineer, its sales representative, and system application experts from the equipment manufacturer. Project requirements, objectives, and design limitations were discussed; utility rates and building load profiles were shared; and existing design concepts were reviewed. Assignments for further investigation were identified, to be completed before the team assembled for a face-to-face design-day meeting.
The design-day meeting was a deep dive into the design and operation of the campus’ central plant. Since the plan was for both a district cooling and heating plant, careful consideration was given to understanding their simultaneous demands so that heat recovery could be maximized. The utility rate structure included a high daytime rate that made a thermal storage system attractive. A ground source solution was also part of the preferred design. The diversity of system demand led to careful consideration for equipment selection criteria for safe and efficient system operation.
The design-day meeting ended with a list of follow-up evaluations to be completed on the way to a holistic, integrated design solution. Follow-up items included an evaluation of the turndown capability of the larger chillers at nonstandard operating conditions to help determine if there was a need for a small “swing” chiller, and an assignment to develop a system control mode table to be evaluated by the manufacturer’s system application experts.
Seeing the Sum Instead of the Parts
Taking this approach can result in improved energy efficiency and operational cost savings, and play a role in meeting goals you may have for performance, redundancy, sustainability, energy consumption, and efficiency.
By determining upfront what you want to achieve in your building and the steps that need to be taken, you will be better prepared to choose the systems that are best suited for the job. It will also help you keep your priorities at the forefront when designing industrial and manufacturing facilities.