• Energy Management @ U-M
  • Energy Fest
  • Outreach
  • Staff Members
• Energy-Saving Tips and FAQ
• Energy Highlight
  • Past Highlights
• Computing
• Lighting
• Programs
  • Absorption Chillers
  • Energy Star / Green Light
  • ECO
  • EEI
  • Energy Conservation Tools
• Buildings
• News and events
  • Energy Fest
• Links
• Site Map

Past Energy Highlights

Belt Replacement = Energy Conservation:
Energy conservation measures can come in all shapes and sizes. V-belts use a trapezoidal cross section to create a wedging action on the pulleys. Cogged belts have slots that run perpendicular to the belt’s length. Synchronous belts are toothed at an angle and require the installation of mating toothed-drive sprockets or sheaves (the wheel or roller that holds the belt.)

V-cogged belts (left and above) have distinctive herringbone tracks to eliminate slippage and reduce noise. Below is a standard v-belt.

The belt and sheave systems installed in the air handling units and return fans in campus buildings are usually the standard v-shaped, but they can stretch and eventually slip on both motor and fan sheaves. This belt slippage causes a waste of motor horsepower and reduced efficiency. Synchronous belts and sprockets do not slip, and are preferred over a “straight” cogged belt and sprocket due to lower noise levels.

The University has replaced many v-belts and sheaves with synchronous belts and sprockets, which offer an efficiency of about 98%, require less maintenance and retensioning, and run slip-free. Not all belts can be replaced, due to length limitations in current manufacturing, accessibility issues, and economic feasibility. This Energy Conservation project was originally proposed by Kim Borregard and Brian Morgan to cover nine buildings on Central Campus and has been expanded to include most Ann Arbor Campus General Fund buildings, where feasible.

The pilot study at Randall Lab on Central Campus confirmed the average energy savings of about seven percent. Although a savings of seven percent doesn’t sound like much, it averages out to a yearly savings of more than $700 per belt. With over 200 belts already replaced, seven percent can add up quickly, and pay for itself in approximately six years. In addition, there is a reduction in maintenance and labor costs due to the longer life of synchronous belts - estimated at two to three times as long. The result is less downtime due to less belt replacement and reduced frequency of tension adjustment.

Solar Collector Array at CPP:
The Central Campus Power Plant and Energy Management have joined forces to install a solar collector array on the roof of the power plant to preheat campus hot water. The collector’s rotating platform tracks the sun and its aluminum mirrors focus the sun’s rays onto pipes. It will be one of the first of its kind in the U.S.

The array contains six 4’ X 39’ Power-Spar modules on a rotating platform with a controller that points the collectors directly at the sun throughout the day. A pump will circulate a glycol solution between the collector on the roof and a double wall shell and tube heat exchanger mounted on the wall inside the Turbine Building. A second pump will circulate domestic water from an incoming line through the heat exchanger and back into the line just upstream of the water heater.

The collector saves about 250 million BTUs of steam per year. That translates to a savings of $4000 per year. The use of the solar collector to heat the water also avoids the addition of 500 tons of carbon dioxide to the atmosphere over its lifetime. If this pilot unit proves successful, there are plans to install them at several other locations on campus heating pool water, domestic water and heating water.

The collector’s manufacturer, Menova, is currently researching using the collector to produce chilled water using a low temperature absorption chiller.

Solar Collector Array on the top of the Central Power Plant

Tertiary Valve Replacement:
The Tertiary Valve Replacement Project is to replace selected, existing, tertiary chilled water (CHW) valves. Tertiary CHW control valves regulate the flow rate of distribution CHW to each building from a regional CHW system. At U-M, most tertiary CHW valves are typically sized to match the connecting pipe diameter which is often sized to accommodate future additions to the CHW system. Thus, many tertiary valves have been sized to accommodate potential future loads that have yet to be added and therefore are presently oversized and difficult to control properly.

Besides difficulty in maintaining stable tertiary CHW temperatures and flows, oversized tertiary CHW valves lead to unnecessary energy consumption due to increased distribution pump flow rates, and increased chiller cycling (e.g. operating 2 chillers at part load, when only 1 is needed). Such cycling reduces chiller efficiency, and requires the operation of unnecessary primary pumps, condenser pumps, and cooling towers.

This project replaces selected, existing, tertiary CHW valves with smaller valves to improve control of CHW temperatures and flows in nine buildings. The estimated project cost is $314,800; the energy cost savings is $92,430, and the simple payback is 3.4 years.

Estimated Project Cost = $314,800
Estimated Energy Cost Savings = $92,430/yr
Estimated Payback Period = 3.4 years

Tertiary Valve installed at East University Chiller Plant

Reduction of Autoclave Trap Cooling Water:

Autoclave sterilizers are machines that use high pressure steam to sterilize and decontaminate medical and science laboratory equipment. When the machine is operating or idling, steam surrounding the sterilization chamber condenses and is discharged to the public sanitary sewer. However, the condensate discharge temperature is required by the Plumbing Code to be less than 140 degrees before it enters the public sanitary sewer system. Tempering is achieved by mixing a constant flow of city water with the condensate discharge regardless of the condensate discharge temperature or volume, often resulting in city water needlessly being used.

An autoclave manufacturer developed a water conservation kit to reduce the water consumption of its autoclaves. A pilot project was proposed and approved for funding in July, 2006 to evaluate and verify the manufacturer’s claim that the water conservation kit would reduce water consumption by its autoclaves by 62%. Six autoclaves in the E. H. Kraus Natural Sciences building were selected for the pilot project. An ultrasonic flow meter measured the water flow rate before and after the installation of the autoclave water conservation kits. Subsequently, the manufacturer’s claim of a 62% reduction in water consumption was verified. The results from the pilot project confirmed that for each autoclave water conservation kit installed on a typical autoclave that is operating or idling yearly 24 hours per day, that the estimated annual water and sewer cost savings is $2059/year (at 2007 water and sewer rates).

This pilot project resulted in an additional 27 autoclave water conservation kits approved for installation in 6 buildings for FY 07.

Autoclave Sterilizer located in the E.H. Kraus Natural Sciences Building	Water conservation kit installed in Autoclave Sterilizer located in the E.H. Kraus Natural Sciences Building

Site maintained by: Plant Operations Web Services

© Copyright The University of Michigan, Site Info