DOE-2 Energy Modeling Summary - Courthouse
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Modulating Condensing Boilers (AltS3)
The average operating efficiency of the boilers was increased from 80% to 93%, representing typical
efficiency for a modulating condensing boiler.
0.54 kW/ton Chiller
The centrifugal chillers were upgraded to high efficiency chillers, with a full load COP of 6.51 (0.54
kW/ton).
0.54 kW/ton Chiller with VFD
The centrifugal chillers were upgraded to high efficiency variable flow chillers, with a full load COP
of 6.51 (0.54 kW/ton).
0.49 kW/ton Chiller with VFD
The centrifugal chillers were upgraded to high efficiency variable flow chillers, with a full load COP
of 7.18 (0.49 kW/ton).
VFD Cooling Tower Fans
The baseline two speed cooling tower fans were changed to variable speed fans. The fans modulate
the cooling tower air flow continuously (down to a minimum flow of 25%) to achieve desired
condenser water temperature.
Energy Recovery (Enthalpy Wheel)
The outdoor air supply is tempered with an enthalpy wheel total energy recovery system (pre-heating
the air in heating season and pre-cooling the air during the cooling season). The enthalpy wheel is
assumed to have the following characteristics:
Total Air Volume
45,900 cfm
Supply Static Pressure drop
0.5"
Return Static Pressure drop
0.5"
Total HR effectiveness
67%
CO2 Sensor Control of O.A.
Each air handler is equipped with a CO2 sensors in spaces with variable occupant densities (e.g.,
conference rooms, courtrooms, auditoriums, training rooms, etc.) and those locations within the
space served by the longest lengths of ductwork. The difference in CO2 concentration between the
return air of each space and outside air is an indicator of the amount of ventilation air required by
the spaces served by the air handler. CO2 sensors, when properly calibrated, allow the flow of fresh
air to be reduced during periods of lower occupancy. This strategy has the potential to significantly
reduce the outside air load on the building at any time an air handler is not operating in an
economizer mode.
APPENDIX I - GSA LEED COST STUDY
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