Solar energy collection and storage - Solar Energy Sciences and Engineering Applications - page 125

Figure 4.2.1 An integral collector storage solar water heater.

AIR

ω

T (t) = H+H COS t

L U

δ a )

T g (t) = T a + T a COS (t -

WATER
SURFACE

0

T g (t)

UCZ

T N (L U .t) = T a (t)

NCZ

HEAT DIFFUSION EQUATION

a 2 T N (x.t ) a T N (x.t )

at

a H (x.t)
ax

= 1
x w

- 1
k w

x

ax 2

4

HEAT DIFFUTION
BOUNDARY
CONDITIONS

H (x.t) = TH (t) η e - µ n x

L NA L N

n = 1 n

THRMAL PROPERTIES AND PARAMETERS
FOR NCZ
T N (x.t), k w, α w, σ w

T N (L N .t) = T (t)

H (L N .t) LCZ

ω δ

T (t) = T - T COS ( t - )

aT N (x.t)
ax

k w

X = L N

HEAT-BALANCE EQUATION

aT g (x.t) aT N (x,t)

dT (t)
dt

- ρ w L C -q (t) L C

= -k w

˜ H (L N - t) -k g

ax

ax

ω t - δ q ) q (t) = q - q COS (

x = L N +L c X = L N

THRMAL PROPERTIES AND PARAMETERS

CONTROL VOLUME
CONSIDERED

FOR LCZ
T (t), k w, ∝ w, σ w

THRMAL PROPERTIES AND PARAMETERS
FOR THE GROUND
T g, k g , ∝ g, σ g

aT g (x.t)
ax

k g

x = L N - L C

Figure 4.2.2 Heat transfer in a non-convecting solar panel (Norton, 1992).

dissolves holds more salt than does cooler water. Salty, heated water being heavier
remains at the base of a solar pond. Insolation penetrating through the top layers of a
pond is absorbed by the layer with heat loss inhibited by the intervening non-convecting
layer (Leblanc et al., 2011).
Salt-gradient solar ponds consist of three zones:

• a surface convecting zone of low-salinity water, typically 0.2 m-0.4 m thick;

• a non-convecting or salinity-gradient zone beneath the surface zone, which ther-

mally insulates a lower convecting heat-storage stratum in which dissolved salt
concentration increases with depth, typically 1.0 m-1.5 m thick; and