Environmental Engineering Reference
a coefficient of performance of 1.5.
The initial cost of an ACES is much higher than that for conventional
home heating and cooling systems, mainly because of the cost of the stor-
age tank. Energy savings in a house with electric resistance backup can be
over $1,000 per year, which gives about a 10- to 15-year payback.
The system is usually sized to meet the summer cooling require-
ments, rather than the winter heating load, of a building. In order to meet
the total heating requirements of a building, an ACES is best suited for cli-
mates where the heat provided to the building from the tank during the
winter is nearly equal to the heat removed from the building for cooling
and transferred back into the tank during the summer. This is possible in
areas where the winter and summer climates are not too extreme, such as
Maryland and Virginia.
INTEGRATED COMMUNITY SYSTEMS
An Integrated Community Energy System (ICES) is a type of district
heating and cooling system that uses heat pumps to collect and concen-
trate energy. The use of heat pumps allows free heat that would other-
wise be lost to be removed from fuel cells, boiler waste heat, groundwa-
ter, lakes, solar and geothermal sources. An ICES has three major compo-
nents: heat pumps, a heat source which may also act as heat storage and a
distribution system. The heat pump section of an ICES may be centralized,
distributed or cascaded. In a centralized system, one or more large heat
pumps are used in a manner similar to the centralized boiler of a district
heating system. The heat pumps are located in a central facility, and they
remove heat directly from a heat source. This heat is then used to warm
distribution water, which is then pumped to individual buildings.
In a distributed system, small heat pumps are located in each build-
ing. Water from the heat source is sent directly to an individual heat pump.
Heat removed from the distribution water is then used to warm the build-
ing. Some heat pumps may be used to also provide cooling.
A cascaded system uses both centralized and individual heat pumps.
A central heat pump removes low temperature heat from the primary source
and adds it to the distribution water, which is sent to individual buildings.
Heat pumps in the buildings then use this distribution water as a secondary
heat source. This system is used when the primary source water is too cor-
rosive, such as salt water, or contaminated, such as waste water.