22 May 2008


District energy systems have the potential to decrease the CO2 emissions linked to
heating, cooling, electricity and hot water. This is true in particular when considering the
prospect of large polygeneration energy conversion technologies, allowing a more rational
use of energy and a better sharing of resources between users. Significant improvements
towards lower greenhouse gas emissions will however not be possible without rethinking the
way heating and air-conditioning shall be met, namely changing from individual solutions to
more rational solutions, including the consideration of networks when dealing with high
energy density districts. Several alternatives of advanced networks exist. They range from
relatively high temperature networks with local organic Rankine cycles or absorption cooling
units, to low temperature networks with or without phase change fluids but with heat pumps.
The paper presents a new network operated with CO2 and connected to a central plant with
an open cycle CO2 heat pump. The system is discussed and compared with a double water
network that would meet the same heating and cooling demands.