Energy Efficient MeeFog System Allows Amherst College to Humidify the New Science CenterUniversities
Science Center Expansion
Founded in 1821 with a focus on liberal arts, Amherst College has seen an 85% increase in enrollments in Science, Technology, Engineering and Math (STEM) classes during the past 15 years. Consequently, a new Science Center was opened in the fall of 2018 that embraces sustainability and efficiency standards.
The facility was designed to reduce energy usage by 73% compared to the typical science building through a variety of features. These include:
- More efficient systems for building HVAC
- Individual lab hood controls
- An insulating building envelope
- A floor plan that groups specialized labs
- Rainwater harvesting (to reduce water consumption by a million gallons a year)
- A rooftop solar array (to provide one third of energy use)
Additional solar energy comes from the Farmington Solar project in Maine via a 20-year power purchase agreement (PPA) for 10,000 megawatt hours (MWh) of electricity. This PPA cuts carbon emissions by 3,200 metric tons per year and greenhouse gas emissions by 17.5%. The rest of the needed power (about half) is derived from a combined heat and power (CHP) plant on campus which is to gradually be phased out.
“Deriving such a significant amount of Amherst’s electrical needs from this renewable source represents a major step in the College’s Climate Action Plan (CAP),” said James Brassord, chief of campus operations. “This electricity will be used to power the infrastructure that will allow us to decarbonize the campus.”
Massachusetts College Air Handling Units:
- Humidification and Cooling Supplied to five air handling units (AHUs) and four heat recovery units (HRUs).
- Consisting of one pump rack with dual 5 GPM pump units, 5 hp motors, VFD & pressure transducer.
- The Mee pump units are mounted on one stainless steel pump rack with single-point power connection and PLC that monitors both pump units and provides auto-switchover.
Entering air conditions: 66 °F db / 44° F wb
Leaving air conditions: 55° F db / 42° F wb
Mee’s scope of work: Supply of fog pump
rack, staging valves, nozzle manifolds, and mist eliminators.
Max fog system power: 2 x 5 HP
Humidification stages: 15
Fog System Design:
MeeFog Nozzle Count: 121
Humidification capacity: 1,530 #/hr
MeeFog Nozzle Count: 140
Cooling capacity: 20° F
Building Efficiency Improvements
Meanwhile, tangible reductions in energy load and carbon footprint are being achieved through building energy efficiency improvements. The Science Center labs have a ferocious appetite for cooling. Various regulations and standards demand no recirculation of inside air in the labs. Thus, new ambient air must be continually fed in. During the summer months, that air is hot. A lot of energy is required to bring down the temperature to a comfortable level, courtesy of a Central chiller plant Campus Loop.
“Continuous air replacement is the top operating expense of the Science Center,” said Amherst College Science Center Specialist Kyle Mangini who looks after all laboratory and mechanical systems. The Science Center design included features that reduce the cost burden (and hence the carbon footprint) of the chiller plant. This is achieved via a waste heat energy recovery system.
The exhaust air from the Science Center is fed through a glycol loop by Konvekta (Princeton, NJ) which is used to cool the outside air entering the building. The heat exchange efficiency of this system is raised by the addition of a MeeFog cooling system by Mee Industries (Irwindale, CA). It adiabatically precools the exhaust air by 10 ℉ to 15 ℉ with the evaporation of microfine fog droplets before it reaches the glycol loop. Thus, the workload on the large centrifugal chillers used to cool the outside air is considerably reduced.
“Chiller energy usage can be brought down by as much as a third using this cooling augmentation approach,” said Mangini.
Jonathan VanDine, owner of JVD Industrial (Windsor, CT) acted as the manufacturer’s rep for the fogging system. He explains how it works: Four heat recovery units (HRUs) have fog nozzle arrays stationed inside to spray the exhaust air with fog. In summer, the exhaust air from the labs ranges between about 72 ℉ and 76 ℉. Fogging drops that number down anywhere from 60 ℉ to 64 ℉ before it is drawn across the heat exchanger to be applied to the inlet outside air supply.
Mangini said that three electric centrifugal chillers of around 500 to 600 tons each are used to provide chilled water to the entire campus. One of these chillers is used to cool anywhere from 85,000 to 100,000 CFM of outside air needed by Science Center labs.
“The glycol loop helps to reduce air replacement costs and is almost always running,” said Mangini.
In July when temperatures can reach 80 ℉ or more, up to 500 tons of cooling might be needed for outside air to the lab. The fog system for exhaust air operates seasonally. It runs from May to September.
“Once we start the fogging system, the tonnage needed for cooling drops to around 150 to 250 tons,” said Mangini. “We get a lot more cooling out of the convective glycol system due to fogging at the exhaust level.”
He estimates that the average tonnage curtailment from the Mee/Konvecta systems runs at around 30%. If the chillers are operating at 250 tons per day, MeeFog System’s High-Pressure Water Atomization reduces the load by about 80 tons and the Konvecta system by about 20 tons on a summer’s day due to the evaporative cooling of exhaust air.
Seasonal numbers show a reduction of about 36,000 tons of chiller cooling due to fog alone. Data pulled from building systems at Amherst College from the summer of 2022 shows a reduction of 17,049.5 tons of chilling load when only the glycol loop is running and 53,119.5 tons reduction when both fog and the glycol loop are operating. The numbers for fogging increase during the hottest months and tail off in May/June and September.
“Eliminating an additional 36,000 tons of annual chiller load is huge for us,” said Mangini. “As well as representing a major dent in the annual bill for continuous air replacement to the labs, the combination of MeeFog and a glycol loop brings about another big drop in our carbon footprint.”
Amherst College also uses MeeFog HVAC Systems for building humidification in the winter. From roughly October to June, fogging is used inside five air handling units (AHUs) to raise the dry winter air to the desired level of humidity. “We need humidity in labs to avoid static electricity that can damage computers and other equipment, and in our mill so wood doesn’t get too dry,” said Mangini. “Our physics department wants 40% humidity, and we can’t reach that without MeeFog.”
He added that as another aspect of the college’s CAP, fogging may eventually replace steam-based humification systems used at other parts of the campus such as the Art Museum building and other facilities.
Future Plans for Geothermal
While these systems have already eaten into the carbon footprint of the campus, Amherst has even bigger plans. It aims to achieve carbon neutrality by 2030. A major part of this is converting from steam heating powered by fossil fuels to low-temperature hot water heating. This project is being staged over seven years and is scheduled to be completed by 2030.
It will require conversion of the existing heating system as well as the laying of new pipes underground to connect all campus buildings to each other and the low-temperature hot water system. To complete the transition, Amherst will drill geothermal wells and install electric heat pumps. Water will be heated to 130 ℉ to provide heat to buildings.
“We just began removing steam heating gradually from the campus,” said Mangini. “The transition to geothermal energy means the college can reduce its slash carbon dioxide emissions by another 14,000 tons per year.”
Sidebar: Cost Breakdown for Fogging
- Cost of the MeeFog System taking into account the equipment, the mechanical contractor, added construction costs to the owner, labor, engineering, and administrative costs: Approximately $300,000 for a system similar to Amherst (the MeeFog spec list came to $192,000).
- Return on investment: $500-$1500 per ton of building capacity saved depending on arrangement, existing infrastructure and build-out costs.
- Operational costs for fogging: about 7-10HP of pump kw plus the cost of reverse osmosis water.
If the building already has a glycol loop-style energy recovery system, the payback for MeeFog should be realized within one cooling season in New England. If an energy recovery system needs to be added, a longer payback timeline would be required.