Civil Engineering Reference
In-Depth Information
Table 4
Claimed performances of TCA' ClimateWell 10 machine (N'Tsoukpoe et al.
2009
)
Storage capacity
a
(kWh)
Mode
Maximum output
capacity
b
Electrical
COP
c
Thermal
efficiency (%)
(kW)
Cooling
60
10/20
77
68
Heating
76
25
96
160
a
Total storage capacity (i.e. including two barrels)
b
Cooling capacity per barrel: 10 kW cooling is the maximum capacity. If both barrels are used in
parallel (double mode), the maximum cooling output is 20 kW, and the heating output is 25 kW
c
Coefficient of performance (COP) = cooling or heating output divided by electrical input
especially; however, it can be operated to fulfil either cooling or heating
requirements in buildings. It can be seen that the condenser and evaporator are
combined together in conjunction to the desorber and the absorber reactors in the
TCA system.
During the charging phase, the weak concentration solution or the poor solution
is pumped over the heat exchanger. As the poor solution attains the saturation
point, the solid (salt) crystals present in the poor solution are dropped into the
vessel by means of the gravity. The water vapour which is desorbed during this
process is transferred to the condenser through the gas pipe arrangement.
By this, the heat of condensation and binding energy release are transferred to
the building indoor spaces (heating mode) or to the ground-coupled heat exchanger
(cooling mode). Likewise, during the discharging phase, the heat of evaporation is
supplied by the low-temperature heat source, either from the building space heat
exchanger or by the ground-coupled heat exchanger to the condensed water in the
condenser. Herein, the condenser acts as the evaporator, which in turn produces
the water vapour that flows back to the reactor heat exchanger.
The concentrated solution after absorbing the vapour turns into unsaturated
solution by virtue of the dissolution of some salt crystals present in the reactor
vessel. The heat storage density acquired by this system is 253 kWh/m
3
of LiCl
salt. The cost factors involved in using the salt has limited the incorporation of this
system for long-term heat storage applications. The important aspects of the TCA
system are summarized in Table
4
.
4.9.5 Solid/Gas Thermochemical Energy Storage System
The solar-energy-based sorption thermochemical energy storage system dedicated
for solar air-conditioning application is being developed in recent times. This
sorption system operates under two distinct phases, namely the diurnal period and
the nocturnal period (Stitou et al.
2012
). The schematic and the photographic
views of the solid/gas thermochemical storage process pilot plant for solar air
conditioning are depicted in Fig.
11
.
During the diurnal period (or the daytime), the reactor in the system gets heated
up by the solar thermal energy as retrieved through the solar collectors. This heat
