Environmental Engineering Reference
In-Depth Information
Table 3.11
Parameters of Low-temperature Storage Materials
ρ
λ
Density
in
Heat conductivity
Heat capacity
c
kg/m
3
in W/(m K)
in kJ/(kg K)
Water (0°C)
999.8
0.5620
4.217
Water (20°C)
998.3
0.5996
4.182
Water (50°C)
988.1
0.6405
4.181
Water (100°C)
958.1
0.6803
4.215
Granite
2750
2.9
0.890
Coarse gravely soil
2040
0.59
1.840
Clay soil
1450
1.28
0.880
Concrete
2400
2.1
1.000
Source:
Khartchenko, 1998
over periods of a few hours to a few days. Hence, long-term storage systems
need significantly larger volumes. Large storage systems can be:
•
artificial storage basins
•
rock caverns (cavities in rocks)
•
aquifer storage (groundwater storage)
•
ground and rock storage.
Furthermore, storage systems can be divided into different temperature ranges:
•
low-temperature storage systems for temperatures below 100°C
•
medium-temperature storage systems for temperatures between 100°C and
500°C
•
high-temperature storage systems for temperatures above 500°C.
Finally, there are different types of heat storage such as:
•
storage of sensible (noticeable) heat
•
storage of latent heat (storage due to changes in physical state)
•
thermo-chemical energy storage.
Because of space considerations, this topic describes only
low-temperature
storage systems for the storage of sensible heat
. Table 3.11 shows parameters
of some low-temperature storage materials.
Domestic hot water storage tanks
Only annual usage simulations can estimate the exact dimensions of a hot
water storage tank. The size depends on the hot water demand, solar fraction
(see Equation 3.59, p112), collector performance, collector orientation, pipes
and last but not least on the annual solar irradiation. For central European
climates, a rough estimate can be made. Here, the
storage volume
should be
