MULTIPLE EFFECT DISTILLATION OF SEAWATER WATER USING SOLAR ENERGY - THE CASE OF ABU DHABI SOLAR DESALINATION PLANT - Energy Research Developments: Tidal Energy, Energy Efficiency and Solar Energy - page 15

was measured by a three-wire RTD connected to the DAS. Figure 10 shows a block diagram
of the data acquisition and analysis for the heat collection system. The estimated percentage
error in the heat measurement was estimated as 1.5 - 3% while the error in the collector
efficiency measurement 2.0 - 3.5%.

Figure 10. Block diagram of data acquisition system for heat collection.

5. Data Analysis

5.1. Calculating the Solar Radiation on Absorber Plate

The global solar radiation intensity on a tilted surface can be expressed by Eq. 1.

I = I + I (1)

t d s

where I d is the direct component of solar radiation and I s is the diffuse component. According
to [5], the components can be expressed as:

1

sin( h )

I = I × P × cos( θ )

(2)

d o

1

1 + cos( α )

sin( h )

1 1 − P

I = × I × sin( h ) × × (3)

s o

2 1 − 1 ln( P ) 2

where P is the atmospheric transmittance, h is the solar altitude, α is the tilt angle to the
ground, θ is the incidence angle of direct radiation on the tilted surface. The solar angles are
shown in figure 11. The transmittance P is defined as the ratio between the normal solar
radiation at the ground level to the corresponding value at the outer limit of the atmosphere:

I

N

P =

(4)

I

oN