Renewable Energy, 5th Edition

(4.136)

where U may depend on wind speed in analogy to (4.118). The collector gain is now given by $E_c^{gain}=E_c^{sw}+E_c^{lw}+E_c^{sens},$ where the first term is proportional to A, while the two last terms are proportional to A_a. Assuming now a fluid flow $J_m^c$ through the absorber, the expression for determination of the amount of energy extracted becomes [cf. (4.128)]

$\begin{array}{ll}{J}_m^c{C}_p^c(T_{c,out}-T_{c,in})\hfill & =E_c^{gain}(\overline{T}c)-A_{a}C\prime \mathrm{d}\overline{T}c/\mathrm{d}t\hfill \\ =E_c^{sw}+E_c^{lw}(\overline{T}c)+E_c^{sens}(\overline{T}c)-A_{a}C\prime \mathrm{d}\overline{T}c/\mathrm{d}t),\hfill \end{array}$ (4.137) ...