Engineering systems in manufacturing, industrial buildings: Energy efficiency
Manufacturing and industrial facilities have some unusual engineering requirements, and focus significant time on enhancing energy efficiency.
Jonathan Eisenberg, PE, Associate Manager, Rolf Jensen & Associates Inc., Boston
Brian P. Martin, PE, PDX Electrical Discipline Manager, CH2M Hill, Portland, Ore.
Peter Pobjoy, PE, LEED AP, Chief Design Officer, Southland Industries, Los Angeles
Peter Zak, PE, Principal, GRAEF USA, Milwaukee
CSE: What types of systems have you specified in manufacturing facilities to help make them more efficient? Discuss occupancy sensors, zoned control, etc.
Zak: Natural daylighting and ventilating control are low-hanging fruit; more complex approaches involve efficient control and interlocks between facilities services and production equipment.
Eisenberg: We consulted with a lab facility on an air sampling system that monitored CO and volatile organic compounds, among other properties. The intent of the system is to increase the ventilation rate to as high as 15 air changes per hour (ACH) in an upset condition, but to reduce the rate of air change in an unoccupied mode to as low as 2 ACH. Our role was to look at a worst-case flammable liquid spill and determine if the reductions in ventilation rates were acceptable from a fire protection standpoint.
Pobjoy: Those systems include:
- Energy-efficient motors for both process-related equipment and building HVAC and plumbing equipment
- Variable frequency drives on most pumps, fans, and compressors
- Dynamic electrostatic filters with low pressure drop
- Oversized ductwork to reduce static pressure and fan energy
- Oversized piping to reduce pressure drop and pump energy.
Martin: There has been an emphasis on lighting systems for quite some time to increase energy efficiency. Some states no longer have an exemption of lighting power density for manufacturing spaces, so that has really driven the watts/sq ft down. T5 and LED lighting have made that possible. Additionally, we also see very few motors that are run across the line; nearly all of them are controlled via an adjustable speed drive. We are specifying higher efficiency drive systems as well as higher efficiency UPS systems. The data center market has helped drive the demand for increased efficiency in UPS and adjustable speed drive systems, with the industrial market receiving the benefit.
CSE: What types of renewable energy systems have you incorporated into manufacturing or industrial facilities?
Martin: We have designed solar arrays and small-scale wind turbines, but quite often these are being added as a side project, after the initial build-out of the facility. Getting a large facility designed, built, and commissioned is so complex and expensive that we are asked to pre-facilitate for renewables so that they can be added after the bulk of the construction activity is done. The decision to defer is sometimes driven by project financials as well. If a project starts to overrun its original budget, owners typically look for low-hanging fruit to “value engineer.” Renewables sometimes are an easy target, especially since they are typically a low percentage of the overall facility demand.
Zak: The most common and cost-effective systems we have engaged are heat recovery systems from building exhaust and production equipment.
Pobjoy: Those renewable energy systems include solar thermal systems generating hot water, which is then stored in a tank for daily use. The hot water is used by absorption chillers to generate chilled water and by heat exchangers to generate heating hot water and domestic hot water. The solar system used evacuated tube technology.
Eisenberg: While we do not design or specify such systems, we are seeing an increase in our project work on facilities such as hydrogen and liquid natural gas (LNG) fuel. Both of these fuels are more prevalent in the U.S. today as alternative energy sources.
CSE: Have you seen the demand for electric vehicle charging stations increase in facilities like this?
Eisenberg: In our hydrogen fuel cell work, we see a move away from electric powered fork trucks in large central distribution warehouses. These facilities are using more hydrogen-powered vehicles to reduce the time needed for re-charging.