Question

04: An Ocean Thermal Energy Converter (OTEC) pumps 200 m/s through a heat exchanger in which the temperature (expressed in Kelvins) drops by 1 %. All the heat extracted is delivered to the ammonia boiler. The ammonia temperature, THT, at the turbine inlet is equal to the mea temperature of the water in the warm water heat exchanger minus 1 K. The temperature, Tcr, of the ammonia leaving the turbine is kept at 10°C by the cooling effect of 250 m/s of cold water. The efficiency of the turbine/generator system is 90% of the Carnot efficiency of a heat engine working between THT and TcT 12 MW of the produced electricity is used for pumping. Heat capacity of water is 4.2 MJ m K (i) What must the intake temperature of the warm water be, so that a total of 20 MW of electricity is available for sale? (ii) What must the intake temperature be so that the OTEC produces exactly equal to the amount of power needed for pumping? Q5: Comment on two tidal energy electricity-generation systems

Answer 1

cger TITemperature at indit f Heat T2-Temperotuie at exi Heat (T- T) Ti AT = O.o1T Tit 0.39 T TIT2 Tmean 0.995T1 2 2 ater in Heat e Qgiren by 'qCe)aT mcp AT M 200 n3 8.4T, MW (0-335 T,-10K Turbine in let Temperatusie 283 k exit temperatusre o9 nc Turbine effictency 2 3 G.o 0.935T1

Work ouput From Turbine x 8.4T MW) 2 83 1 - 0.995T-1 Wnek 2o MW 20 MW WT Wp 0.9X283 X 8.4TI |2 = 20 Co. 915 TM-1 254.7T O 3 T 32 3.81 (0-995T-1) o.gxo.995TI -o.3 T - 254.7T, 3-aX o995 T, - 3-91 R55. TI o.89 6 T 3.79ITt3.1z0 2 o.896T 259.39IT t31o 293.y9 K, 0.0117 Ti not feasible Ti nek Turbine Cage sork (i) in the Lo dund 2 83 x8.4T ニ12 - 0.935T,-1

о-9Х2 83хTI O.J T 1 2 о-995 T - 1 o.9T 0 9X293T 1.43(о-995T- 1) 0-9хо.д95TI ч ФОИ 2 895T — о 255-С TI 1423T + 1.Ч3 о- ш 25. o23 T 35 T 1Y3 о. у aing T 297.17K, 5.56K ( K notFeasike TiE 14-17°с