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CHP System #2 consists of a
60 kW Microturbine, whose waste heat is used to
run a single effect absorption chiller with 70
kW (20 tons) of cooling capacity. By using the
waste heat from the microturbine, the overall
system efficiency can be significantly improved.
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Microturbine
The Microturbine provides 60 kW of power to the
building plus high-temperature exhaust heat that powers
the absorption chiller and is used to regenerate the
desiccant. When the chiller is not running, a
damper diverts turbine exhaust to atmosphere.
Absorption Chiller
Absorption is a physiochemical process of evaporating
and condensing a refrigerant. Here water is the
refrigerant and concentrated lithium-bromide solution is
the absorbent that drives the refrigerant cycle.
Inside the chiller, refrigerant [water] is absorbed by
the absorbent [LiBr/H2O],
which lowers the pressure and allows the refrigerant to
evaporate at low temperature. While evaporating,
the refrigerant removes heat from a chilled water stream
which runs through tubing in the chiller and then is
pumped to a cooling coil in the RTU. After
absorbing refrigerant, the dilute LiBr/H2O solution is heated by the hot
turbine exhaust which drives off the refrigerant, the
dilute LiBr/H2O solution
is heated by the hot turbine exhaust which drives off
the refrigerant and the cycle start over again.
After leaving the chiller, the warm turbine exhaust is
used to dry or "regenerate" the desiccant unit.
Solid Desiccant Unit
In this unit, silica gel embedded in a sotating
honeycomb wheel absorbs humidity from building
ventilation air. The wheel then rotates the moist
gel into the regeneration section where hot gas from the
absorption chiller dries it.
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