Solar thermal collectors

Considering the top cycle temperatures prescribed for both cycles 2 and 3, different collector prototypes are under development in the framework of project, namely: an evacuated CPC for cycle 2; and a linear Fresnel concentrator for cycle 3.

At this point, a preliminary assessment of the evacuated CPC allows an early estimation of its efficiency parameters (steady-state) according to the values presented in Table 2.

Table 2. Estimated efficiency parameters (steady-state) for Cycle 2 evacuated CPC collector

П0

a1 [W/(m[6].K)]

a2 [W/(m2.K2)]

0.68

1.0

0.007

A ray-trace based assessment allows a preliminary estimation of longitudinal and transversal incidence angle modifier (IAM) values according to Table 3.

Table 3. Estimated transversal and longitudinal IAM values for Cycle 2 evacuated CPC collector

в

20

40

50

60

К(в)

1.00

0.61

0.33

Kl(e)

0.90

Instantaneous power calculations performed after cycle 2 conditions and estimated CPC parameters follow the corrected methodology presented in [14].

Regarding cycle 3, the present state of development of the linear Fresnel concentrator does not allow an early assessment of both optical and thermal performance (information available to the project consortium within next spring, according to project planning).

Nevertheless, in the present paper the assessment of the POWERSOL technology for top cycle temperature conditions of cycle 3 is made after thermal and optical parameters of a commercial parabolic trough collector (PTC), the LS-3 model (used between 1984 and 1990 in the Mojave desert, CA, USA solar thermal power plants, e. g.).

LS-3 PTC efficiency and IAM follows the parameters described in [15], with thermal loss coefficient calculated after the polynomial expression presented in [16]. Instantaneous power calculations for LS-3 PTC followed ‘EW’ tracking configuration neglecting diffuse or ground reflected radiation components (reasonable simplification in view of the 26.2 concentration factor).

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