Greener Facilities Short List - 15 Mechanical Improvements to Save Energy

Feb. 19, 2003

Rick Fredrizzi writes a monthly newsletter for called 'Greener Facilities'. This article is part of the February 2003 edition of that newsletter. To view the entire newsletter or to subscribe to the newsletter, click here.

Mechanical energy efficiency improvements exist at many, (dare I say all) facilities. Many however are size and capacity specific and some of the following upgrades may not apply. That said…

  1. Central plant energy efficiency opportunities include installing higher efficiency chillers (or other AC systems). New chillers are 25 to 50 percent more efficient than chillers 10 or more years old. Since many facilities with central chillers must replace them to comply with the CFC phase-out it pays to invest in a new, high-efficiency unit. The new chillers also have vastly improved controls that make it easier to optimize chiller efficiency.
  2. Consider installing a larger cooling tower to improve efficiency and reduce tower return temperature. Cooling towers are rarely sized to handle "worst case" conditions. As a result the entire cooling system is very efficient on the warmest days. An oversized cooling tower results in lower return water temperatures and higher chiller efficiency.
  3. Install variable speed drive(s) on the cooling tower fan(s). A variable speed fan will allow the cooling tower to operate efficiently using less fan energy and will reduce fan maintenance by eliminating on-off fan cycling.
  4. Install high efficiency condensing boilers for heating hot water. All gas and propane-fired boilers should be modulating condensing boilers with efficiencies higher than 90 percent. This is about 30 percent more efficient than most older boilers. Also, condensing boilers operate very efficiently at low loads. Most new installations utilize two or more smaller, modular boilers rather than a large boiler.
  5. Install a high efficiency hot water heater. New high efficiency hot water heaters use much less energy to heat water for kitchen, pool and guestrooms.
  6. In warm months, reduce outside air outside intake, especially when enthalpy is high. Many facilities bring in too much outside air during warm and humid periods.
  7. Repair (and upgrade where necessary) insulation on steam, hot water and chilled water piping. Consider "wicking" insulation on chilled water piping. Much of the installation on existing steam, hot water and chilled water piping was installed when energy was cheaper. Additional insulation will further reduce piping losses.
  8. Install variable speed drive(s) on the hot water pumping system(s). All continuously operating hot water pumps should have variable speed drives that reduce pumping energy during periods of low hot water use.
  9. Obtain "free" hot water from the chiller(s) or other air conditioning units. Consider adding a new "heat recovery" chiller to produce hot water. Facilities that require cooling most of the year can obtain "free" hot water from their refrigeration equipment. This can be accomplished by double bundled heat exchangers in the chillers or using a plate heat exchanger in the condenser-cooling loop going to the cooling tower.
  10. Install variable speed drives on all constant speed fans that are throttled back in response to variable loads. Fans that are controlled with dampers should be retrofitted with variable speed drives. A speed reduction of only 20 percent will reduce fan energy by nearly 50 percent.
  11. Install premium efficiency motors on pumps and fans that have long run hours. Motors on all pumps and fans with long run hours should be replaced with premium efficiency motors. Also, oversized motors should be replaced with smaller motors, which operate more efficiently than the oversized motor they replace.
  12. Consider geothermal heating and cooling. Using the ground (or anearby body of water) for a heat source or heat sink can result in high heating and cooling efficiency, especially during peak conditions.
  13. Install ozone cooling tower water treatment. An ozone water treatment system will keep chiller heat exchanger surfaces clean and efficient while reducing cooling system chemicals.
  14. Install/upgrade HVAC controls to include intelligent new EMS technologies. The latest generation of energy management systems is much easier to use and deliver more consistent savings than earlier energy management control systems. They can deliver a substantial savings while also improving comfort.
  15. Consider installing a desiccant HVAC system. Desiccant technology (which dehumidifies air) has become a valuable tool in space-conditioning options. In certain cooling applications, desiccant cooling units provide advantages over the more common vapor-compression and absorption units. For example, desiccant units don't require ozone-depleting refrigerants, and they can use natural gas, solar thermal energy, or waste heat, thus lowering peak electric demand. They are particularly effective at treating the large humidity loads resulting from ventilation air in much of the country.

Facility managers also can generate significant lifecycle savings through other measures, such as natural landscaping, water-saving equipment, low-maintenance materials, salvaged construction debris and smart building controls. In next month's e-newsletter, we'll explain and cite some practical applications for green building materials and systems.

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