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Above and right: The tri-
> higher energy savings – perhaps as much as eight per building had already been granted planning approval
generation system comprises
cent. Outside air, tempered in the rooftop plant room and did not have to comply with this. Consequently,
a combined heat and power
air-handling units, is ducted onto the active chilled tri-generation was selected solely for its positive
engine linked to an absorption
chiller. Facing page: Active
beam system, and each beam also has its own fresh contribution to improving energy efficiency and
chilled beams are driven by air air correction to localise the control. Heat is recovered reducing emissions.
from the ventilation system.
from extract air using thermal wheels in the air handling ‘The savings from the building’s tri-generation system
plant. Chilled water for the system is supplied either are significant, and therefore the CO2 emissions are
from water-cooled chillers served by a cooling tower reduced to less than 35 CO2kg/m sq,’ Dhaliwal says.
on the roof of the building, or from an absorption ‘The CHP is driven by the building’s electrical load when
chiller that forms part of the tri-generation system. the building’s load is drawing around 60 per cent of the
Consideration was also given to using water from the CHP load for a sustained period of time.
local dock as a cooling source but this was found to be ‘The hot water from the engine is then directed
non-viable, as the future development of the adjacent either to heat exchangers to supply space heating
dock could lead to the ground-source heat pump system and domestic hot water (DHW), or to the absorption
becoming redundant sometime in the future. chiller, depending on requirements. When there is
a requirement for cooling, the absorption chiller is
Tri-generation configured as the lead chiller and supplemented by
The tri-generation system comprises a 1000kVA gas- the water-cooled chillers if necessary, or at times when
fired combined heat and power (CHP) engine linked to it would be uneconomic to run the CHP. Similarly, gas-
an absorption chiller. While tri-generation is now being fired boilers are used to either provide space heating
heavily promoted by the Greater London Authority as and DHW when the CHP is off, or to supplement the
part of its ‘London Plan’ for reducing emissions, the heat generated by the CHP as and when required.’
Jas Dhaliwal, left, and
colleagues at AECOM,
the M&E contractor on
the project.
34 CIBSE Journal December 2009 www.cibsejournal.com
CIBSEdec09_pp32-35_KPMG.indd 34 19/11/09 16:30:23
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