Question 11.7: An SHS storage system is required for a high-temperature CSP......
An SHS storage system is required for a high-temperature CSP plant that is operating as follows:
• CSP plant electric power output P_{el} is 30 MW
• Overall (electrical) efficiency of the CSP power plant \eta_{el} is 20%
• Energy storage duration \tau is 6 h a day
• Storage medium is high-temperature concrete
• Storage medium temperature varies in a storage cycle from t_{min} of 520°C to t_{max} of 760°C
• Properties of storage medium: specific heat c = 0.9 kJ/kg K, density \rho = 2400 kg/m³
Calculate (a) the required thermal capacity of the storage, (b) the storage energy density, and (c) the required mass and volume of storage material.
1. Required thermal capacity of the SHS storage
Q_{s}=\tau\,P_{\mathrm{el}}/\eta_{\mathrm{el}}=6\,\mathrm{h}\times30\,\,\mathrm{MW/0.2}=900\,\,\mathrm{MW}\mathrm{h}=900\,\,\mathrm{MW}\mathrm{h}\times3600\,\mathrm{s}/\mathrm{ h}=3240\,\,\mathrm{GJ}2. Energy density of the storage
q_{s}=c\left(t_{\mathrm{max}}-t_{\mathrm{min}}\right)=0.9\times(760-520)=225\ \mathrm{kJ/kg}3. Required mass of the storage material
m_{s}=Q_{s}/q_{s}=3240\times10^{6}\mathrm{~kJ} /225\mathrm{~kJ}/\mathrm{kg=14,400,000~kg=14,400 ~t }4. Required volume of the storage material
V_{s}=m_{s}/\rho=14,400\;\mathrm{t}/2.4\;\mathrm{t}/\mathrm{m}^{3}=6000\;\mathrm{m}^{3}