Innovation in Global Power - Parsons Brinckerhoff
Innovation in Global Power - Parsons Brinckerhoff
Innovation in Global Power - Parsons Brinckerhoff
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Thermal – Achiev<strong>in</strong>g New Efficiencies, Reduc<strong>in</strong>g Carbon Emissions<br />
http://www.pbworld.com/news_events/publications/network/<br />
Improv<strong>in</strong>g Kitchen Steam Boiler Operation<br />
The orig<strong>in</strong>al boiler was sized to meet the kitchen load<br />
demand, but over time part of the steam kitchen equipment<br />
had been converted to direct gas or electric fired equipment,<br />
so the boiler had become oversized, result<strong>in</strong>g <strong>in</strong> extreme<br />
short cycl<strong>in</strong>g and a drop <strong>in</strong> efficiency. We <strong>in</strong>stalled a steamto-water<br />
heat exchanger up stream of a direct fired gas<br />
domestic hot water heater serv<strong>in</strong>g the kitchen. The system<br />
was arranged to meet the kitchen steam demand first and,<br />
if steam was available, to then feed the new heat exchanger.<br />
Cold water to the domestic hot water heater passes first<br />
through the new heat exchanger and is heated there by the<br />
excess steam. It then flows to the direct fired heater. If the<br />
available steam is adequate for domestic hot water production,<br />
then the heater does not fire. If the steam boiler capacity<br />
cannot meet the demand at this moment, then the heater<br />
fires and heats the water to the desired temperature.<br />
Wide Range of Additional Energy Conservation<br />
Measures<br />
The follow<strong>in</strong>g energy conservation measures that we implemented<br />
can often be applied to other projects.<br />
Water Pump Control. In a number of build<strong>in</strong>gs, we <strong>in</strong>stalled<br />
variable frequency drives (VFDs) on the water pumps and<br />
outside air fans to m<strong>in</strong>imize the water pump<strong>in</strong>g cost and<br />
outside air condition<strong>in</strong>g costs. For example, the Tuttle North<br />
build<strong>in</strong>g had five constant speed pumps that served the<br />
heat<strong>in</strong>g system. VFDs were <strong>in</strong>stalled at these pumps and<br />
the three-way heat<strong>in</strong>g coil control valves were converted to<br />
operate as two valves to support the variable flow operation.<br />
Dur<strong>in</strong>g the occupied hours, the pumps modulate flow to the<br />
coil, which reduces power consumption particularly at partial<br />
load conditions. When the build<strong>in</strong>g is unoccupied, the flow is<br />
ma<strong>in</strong>ta<strong>in</strong>ed at 20 percent to avoid coil freez<strong>in</strong>g.<br />
CO2 Sensors. The majority of build<strong>in</strong>gs featured air handl<strong>in</strong>g<br />
units that operated with a fixed amount of fresh air <strong>in</strong>take<br />
that was <strong>in</strong>dependent of the build<strong>in</strong>g occupancy. This mode<br />
of operation, common for build<strong>in</strong>g design until several years<br />
ago, results <strong>in</strong> unneeded energy consumption. We <strong>in</strong>troduced<br />
CO2 sensors (<strong>in</strong>door air quality sensors) that reduce the<br />
fresh air <strong>in</strong>take, and consequently, the heat<strong>in</strong>g and/or cool<strong>in</strong>g<br />
energy consumption, particularly when the build<strong>in</strong>g is only<br />
partly occupied.<br />
The CO2 sensors are located <strong>in</strong> the return air ducts of 56 air<br />
handl<strong>in</strong>g units. They have automatic controls to modulate<br />
their outside air dampers and exhaust dampers to suit build<strong>in</strong>g<br />
occupancy. The CO2 sensor read<strong>in</strong>gs fluctuate depend<strong>in</strong>g on<br />
build<strong>in</strong>g occupancy levels. The outside air is set to a m<strong>in</strong>imum<br />
rate required for the build<strong>in</strong>g m<strong>in</strong>imum exhaust.<br />
HVAC Upgrade. At the Metro Center, which has class rooms<br />
and lecture halls, the HVAC system was upgraded to <strong>in</strong>clude a<br />
new variable air volume (VAV) system with summer economizer.<br />
This replaced the old high pressure air handl<strong>in</strong>g units and<br />
w<strong>in</strong>dow mounted direct expansion (DX) units. F<strong>in</strong> tube radiation<br />
<strong>in</strong>stalled at the build<strong>in</strong>g perimeter improved occupant<br />
comfort and elim<strong>in</strong>ated the need for costly reheat<strong>in</strong>g systems.<br />
The chiller was replaced with a new, high efficiency unit.<br />
We replaced the constant volume/reheat AC system at the<br />
faculty office build<strong>in</strong>g, which comprised seven old rooftop<br />
units. The new VAV system, which has superior efficiency<br />
and provides better air distribution/occupant comfort, will<br />
be controlled by the campus build<strong>in</strong>g management system.<br />
Heat Recovery. Because there are many heat generat<strong>in</strong>g<br />
HVAC systems on the campus and needs for the heat<br />
throughout the campus, we implemented a heat recovery<br />
system where it made economical sense. One example is<br />
the Tuttle North sports complex, where heat from the<br />
computer room A/C condenser was dissipated by a cool<strong>in</strong>g<br />
tower. This heat will now be recovered to heat the Olympicsize<br />
swimm<strong>in</strong>g pool water. Other energy sav<strong>in</strong>gs at the pool<br />
<strong>in</strong>clude a roll-over cover to conserve heat when the facility is<br />
not <strong>in</strong> use and VFDs for the water recirculation pumps.<br />
Vendor Misers. Lights on the large number of vend<strong>in</strong>g<br />
mach<strong>in</strong>es throughout the campus operated around the clock,<br />
as did the compressors for soda vend<strong>in</strong>g mach<strong>in</strong>es. We<br />
<strong>in</strong>troduced vendor-misers, which are proximity sensors that<br />
activate the lights on vend<strong>in</strong>g mach<strong>in</strong>es when approached by<br />
a potential user. Shortly after a mach<strong>in</strong>e dispenses its product<br />
and the buyer walks away, the vendor-miser shuts the power,<br />
vastly reduc<strong>in</strong>g the energy consumption of the unit.<br />
Other Measures. Other measures that contributed to the<br />
energy sav<strong>in</strong>gs and are worth mention<strong>in</strong>g <strong>in</strong>clude:<br />
• Replacement radiator steam traps and float and thermostat<br />
traps at steam risers <strong>in</strong> the steam supply ma<strong>in</strong>s <strong>in</strong> several<br />
build<strong>in</strong>gs and the elim<strong>in</strong>ation of steam leaks<br />
• Air-air heat recovery units for build<strong>in</strong>g exhaust<br />
• A thermal ice-storage system for the sports complex<br />
• Water meters<br />
• Light<strong>in</strong>g motion sensors <strong>in</strong> several locations<br />
• Replacement of <strong>in</strong>candescent lights and T-12 compact<br />
fluorescent lights with low wattage compact fluorescent<br />
lights and T-8 or T-5 compact fluorescent lights with<br />
electronic ballasts<br />
• LED-type exit signs<br />
• Double-pane w<strong>in</strong>dows <strong>in</strong> the campus library and<br />
adm<strong>in</strong>istrative complex<br />
• Improved roof <strong>in</strong>sulation and weather stripp<strong>in</strong>g for<br />
exterior doors.<br />
<br />
19 PB Network #68 / August 2008