Problem 24.1: please help!! Solar Thermal Energy 462 onsider a solur thermal elecinic plant built using a system of 2D...
Solar Thermal Energy 462 onsider a solur thermal elecinic plant built using a system of 2D concentrators that reflect sunight to a system of pipes carrying molten salt with concentration C # 200. Example 24.5 2D Concentrator Efficiency Optimization Wher is the optimal efficiency poxsibie (essaming an onbient temperoture of 300 K and incident sunight u 1000 W/r)? Solving eq (24.23) un encany gives 818 K At this temperature. Cartot efficiency is approximately 63% and about 13% of sneident radiation s reradiated giving a maximum possible efficiency of η u o 55 Figure 24.14 1.0 The overall system conversion efticiency is 3000 (24.21) 24.3 Suppo This quantity vanishes at ambient temperature T T tsince the eticiency iCamot goes to zero) and also vanishes at the radiative equihbrium temperature T Ta = (Yoooeiing/oA)I/4 (where all incoming radia- tion is reradiated), and is positive between. For a given concentration and rate of incoming power, then, the the- oreticai maximum power outpat available is optimized to inera 0.4 simpli 500 1000 0 2000 2500 temperatare ( c to the radiatia Figure 24.13 The maximum theoretically possible systea coaversion efficiency n(T) for concentrated solar electrical power generution as a function of absorber temperature. assuming unhtent temperature T "300 K, and incoming power per unit area o sc 1000 Wini. The curves are labeled by the concentration C. At how temperatures, efticiency is suppressed by the Carnol limit.(The dashed line gnes Sconelr).) At high temperatures mosi energy is re-radiated have to energy 24.4 Consid ( Fot 401 3HOOT. /72 3cT. T 2 (24.22) :0 that th tion. A 30 r. rt_ 4oT 5 + CIoT-0. (24.23) This quintic equation does not have a simple analyticy the absorbing material. solution, but can be easily soived numerically. The sys- tem etficiency ni) is graphed as a function of T in Figure 24.13 foe several possible values of concentra- bon C, assuning clear sky overhead sum insolation of to 1000 Wim2. For real sysems, the thermal to elec 24.3 Discuss some of tric conversion efficiency is subslantiaily less than the Carnot maximum. Knowiedge of the actual conversion efficiency n as a function of temperatare can he used lo optinize temperalure and gower output for more reahstic 24.5 Analya descri efficiency. reliability, versatility, and water reqaire- ments and availability Discuss some of the possible advantages or disad- vantages of the different approaches to solar therma electricity production: parabolic trough, power tower. parabolic dish. Can you imagine other approuche might be worthwhile pursuing? is assu of radi 24.6 Consid pane that that th Problems ature Discussion/investigation Questions 24.1 The radius of Mars orbit around the Sun avcrages roughly R 2.28 x 10 km. Assuming that the sur face temperature is roughly uniform over the p surface and eonstant over a Martian day. face is a perfect black tody, and thal there is t atnxsphcre, estimate the average surface tenige when the planet is in radiative equilibrium eccentzicity of Mars' elliptic orbil 24.1 Estirnate the energy used for space and water beating in yout home. How feasihle would it be to get ail of this cnergy from simple low-temperature solar theronal 24.7 Cotstd the qua that the sur- hler a Martian da 24.2 Sodat thecanl eolectors powering smail off-grid ele tric generaors have been progesed for the develop ing wwld. Rescarch and discuss the advantages and disalvantages of this peuposal Topies tnight inctucde t black body, and hat there is no the ten efticien 24.2 The e e is Estizuace the range over which the scar 24.8 Redo which tghly incom
Solar Thermal Energy 462 onsider a solur thermal elecinic plant built using a system of 2D concentrators that reflect sunight to a system of pipes carrying molten salt with concentration C # 200. Example 24.5 2D Concentrator Efficiency Optimization Wher is the optimal efficiency poxsibie (essaming an onbient temperoture of 300 K and incident sunight u 1000 W/r)? Solving eq (24.23) un encany gives 818 K At this temperature. Cartot efficiency is approximately 63% and about 13% of sneident radiation s reradiated giving a maximum possible efficiency of η u o 55 Figure 24.14 1.0 The overall system conversion efticiency is 3000 (24.21) 24.3 Suppo This quantity vanishes at ambient temperature T T tsince the eticiency iCamot goes to zero) and also vanishes at the radiative equihbrium temperature T Ta = (Yoooeiing/oA)I/4 (where all incoming radia- tion is reradiated), and is positive between. For a given concentration and rate of incoming power, then, the the- oreticai maximum power outpat available is optimized to inera 0.4 simpli 500 1000 0 2000 2500 temperatare ( c to the radiatia Figure 24.13 The maximum theoretically possible systea coaversion efficiency n(T) for concentrated solar electrical power generution as a function of absorber temperature. assuming unhtent temperature T "300 K, and incoming power per unit area o sc 1000 Wini. The curves are labeled by the concentration C. At how temperatures, efticiency is suppressed by the Carnol limit.(The dashed line gnes Sconelr).) At high temperatures mosi energy is re-radiated have to energy 24.4 Consid ( Fot 401 3HOOT. /72 3cT. T 2 (24.22) :0 that th tion. A 30 r. rt_ 4oT 5 + CIoT-0. (24.23) This quintic equation does not have a simple analyticy the absorbing material. solution, but can be easily soived numerically. The sys- tem etficiency ni) is graphed as a function of T in Figure 24.13 foe several possible values of concentra- bon C, assuning clear sky overhead sum insolation of to 1000 Wim2. For real sysems, the thermal to elec 24.3 Discuss some of tric conversion efficiency is subslantiaily less than the Carnot maximum. Knowiedge of the actual conversion efficiency n as a function of temperatare can he used lo optinize temperalure and gower output for more reahstic 24.5 Analya descri efficiency. reliability, versatility, and water reqaire- ments and availability Discuss some of the possible advantages or disad- vantages of the different approaches to solar therma electricity production: parabolic trough, power tower. parabolic dish. Can you imagine other approuche might be worthwhile pursuing? is assu of radi 24.6 Consid pane that that th Problems ature Discussion/investigation Questions 24.1 The radius of Mars orbit around the Sun avcrages roughly R 2.28 x 10 km. Assuming that the sur face temperature is roughly uniform over the p surface and eonstant over a Martian day. face is a perfect black tody, and thal there is t atnxsphcre, estimate the average surface tenige when the planet is in radiative equilibrium eccentzicity of Mars' elliptic orbil 24.1 Estirnate the energy used for space and water beating in yout home. How feasihle would it be to get ail of this cnergy from simple low-temperature solar theronal 24.7 Cotstd the qua that the sur- hler a Martian da 24.2 Sodat thecanl eolectors powering smail off-grid ele tric generaors have been progesed for the develop ing wwld. Rescarch and discuss the advantages and disalvantages of this peuposal Topies tnight inctucde t black body, and hat there is no the ten efticien 24.2 The e e is Estizuace the range over which the scar 24.8 Redo which tghly incom
