Civil Engineering Reference
In-Depth Information
pipes located in the ground, (2) surface water closed heat pump system which uses
similar pipes located under the water in a lake or pond, and (3) ground water open
heat pump system which uses the pumped water from a well and an additional heat
exchanger to deliver water to a close loop system inside the building.
Each of these systems has its advantages and disadvantages. Due to the closed
loop confi guration of the ground coupled heat pump system, this system does not
need a constant supply of a large quantity of water and also does not require any
type of water treatment. The main disadvantage of this system is the high cost of
drilling down the earth for installation of the pipes.
Surface water closed heat pump system uses the water in the pond or lake that
has a high thermal conductivity and therefore is very useful for heat transfer to and
from the lake or pond water to the water in the building loop. Same as previous type
there is no need for water treatment due to closed building loop. It is also less expen-
sive due to lack or need for deep drilling necessary for the previous system. The
disadvantage of this system is its need for an available large lake or pond to sub-
merge the heat exchanging pipes.
Finally ground water open heat pump system is less expensive due to lower cost
of drilling a well compared to that of required for ground-coupled systems, but
requires continuous supply of well water and also water treatment provisions.
In some specifi c climate condition and due to lack of access to very large sources
of ground space or available water capacity a small cooling tower or boiler should
be added to the system to supplement the functions of the ground, or water as the
soul sources of heat exchange in a hybrid confi guration.
The sources of energy consumption in this type of systems are supply fan motor
input power, electric preheat and reheat coils, compressor power input, pumps
power input, and cooling tower fans (if it is required) required power. Duct air leak-
age, heat transfer from ducts and pipes, and effi ciency loss in water coils are other
sources that can indirectly increase the energy consumption of the system. Also
power required to run the boiler if it is necessary could be another source of energy
consumption.
The small energy consumed by low voltage power provided for control valves
and dampers is the other source of energy consumption. There is always electrical
power consumption for heat tracing the water piping outside the heated mechanical
rooms, and protecting the cooling tower basins from freezing.
8.12
Airside Systems
8.12.1
Traditional Airside HVAC Systems
It should be noted here that in the remaining part of this section, when I talk about
the power required for running the system, the focus is mainly on the power required
for the airside operation only. Of course all the power consumers that were
