Tools aid designers in selecting efficient hydronic HVAC systems
Outdated and inefficient heating and cooling systems and the enormous cost to replace them ultimately sealed the fate of the Wilshire Grand Hotel. Owners of the cultural landmark in downtown Los Angeles decided to put a new building in its place even as they were in the midst of modernizing the circa-1950s hotel.
After more than five years of construction, the new 73-story Wilshire Grand Center opened in June 2017, laying claim to the title of tallest building west of the Mississippi River and boasting, among other amenities, innovative climate systems.
Though most building projects are not 1,110-ft-tall skyscrapers with dazzling exterior LED light displays, the Wilshire Grand demonstrates a new way of thinking about commercial building, using an integrated design approach involving the fields of architecture, engineering and construction to achieve efficiency and sustainability goals. Technological advances, stringent energy targets and consumer demand for sustainable surroundings are likewise influencing both new construction and retrofit projects.
With HVAC systems accounting for 50% of a commercial building’s energy use, designing efficient heating and cooling systems is critical to meeting a project’s sustainability goals. Water is key in many HVAC systems because it is the most efficient conductor of heat or cold. Water also has proven to be an adaptable medium as HVAC system design has evolved. Although products typically take center stage when talking about innovation, hydronic system design is advancing in other ways.
Here are three tools that are fostering greater efficiencies in HVAC system design.
Intuitive Selection Programs
An HVAC system made up of high-efficiency components will only enjoy the efficiency gains of these individual products if it is designed, installed and operated as a system. New HVAC systems and retrofit projects can be massive undertakings, but with a strategic hydronics system solution planned from the start, designers can help maximize energy savings. Advanced software tools for product selection, such as Bell & Gossett’s ESP-Systemwize, give HVAC system designers the ability to choose all system components within a single integrated tool. With these tools, designers can make side-by-side product comparisons, create customized project schedules and receive technical assistance in real time.
Accurate Calculation of Load Profiles
Detailed analysis of a building’s heating and cooling loads helps ensure proper equipment is selected for a system, maximizing efficiency and minimizing operating costs. However, designers do not always have the expected or actual building load profile available to them. In these cases, equipment sizing often is based on a system’s design load, or the maximum capacity of the system. This general industry practice leads to selection of equipment that is oversized and therefore not as efficient.
When pump system efficiency is measured at 100% load conditions, it is not an accurate representation of that system’s typical operation. A system generally only operates at that level 1% of its yearly operation. Flow requirements fluctuate constantly throughout the year based on a building’s heating or cooling loads at any given time. As a result, centrifugal pumps installed in HVAC systems operate at part-load conditions most of the time.
By applying a specification formula that accounts for variations in load profile, HVAC designers now have the tools to select pumps based on real-world system demands, ensuring the most efficient system performance. Bell & Gossett’s Part Load Efficiency Value (PLEV) is a calculation that accounts for the entire variation profile and flow requirements based on the actual heating or cooling load in a commercial building HVAC system, not just the best efficiency point. The PLEV selection criteria are accessible through ESP-Systemwize. Although PLEV itself does not provide energy savings in an HVAC system, it is another tool for helping designers select pumps that operate at the highest efficiencies across a building’s operating conditions.
Just as it is important to take the total systems approach in selecting HVAC components to ensure the highest efficiencies are realized, the HVAC system must be considered in relation to other building systems to achieve long-term operational savings. In the case of the Wilshire Grand Center, the design team used data from extensive energy modeling to design the glass façade, which informed the design of the HVAC and lighting systems—the two biggest energy users within a building. Efficient use of energy within buildings is a primary focus of industry guidelines such as ASHRAE 90.1, as well as government regulations. In drought-prone California, water efficiency standards are part of state codes for new construction that apply to HVAC and lighting systems—a driving factor in the Wilshire Grand design.
Once a building is operational, advanced data analytics provided by sensors, software, embedded electronic controllers, digital communications and other means enable automatic integration of hydronic HVAC systems with other systems in a building. Using this data wisely helps ensure smart use of resources, efficient overall building performance and long-term operational savings.