Question 11.6: A solar tower CSP power plant uses a TES system that operate......
A solar tower CSP power plant uses a TES system that operates as follows:
• Power plant electric power output: P_{el} = 20 MW
• Electrical (overall) efficiency of the power plant: \eta_{el} = 0.2
• TES system enables a 5-h operation of the power plant at full capacity: \tau_{s} = 5 h
• Specific heat of storage medium c = 1.0 kJ/(kg K) and density ρ = 2160 kg/m³
• Storage medium temperature limits are t_{s1} = 350°C and t_{s2} = 550°C
Determine (i) the thermal capacity of the TES system, (ii) the storage energy density, and (iii) the required mass and volume of storage medium.
1. Thermal capacity of the TES system
Q_{s}=\tau_{s}\,P_{el}/\eta_{\mathrm{el}}=5\,\mathrm{{h}}\times20\,\,\mathrm{MW/}0.2=500\,\,\mathrm{MW}\mathrm{{h}}= 500 MWh × 3600 s/h = 1,800,000 MJ
2. Storage energy density
q_{s}=c\ (t_{s2}-t_{s1})=1.0\,\mathrm{k J}/\mathrm{kg\, K}\times(550-350)\,{\mathrm K}=200\,\,{\mathrm {kJ}}/{\mathrm{k}}{\it\mathrm{g}}3. Required mass of storage medium
m_{s}=Q_{s}/q_{s}=1.8\times10^{9}\,\mathrm{kJ} \,/200\,\mathrm{kJ}/\mathrm{kg=9\times10^{6}\,\mathrm{kg=9000~t}~}4. Required volume of storage medium
V_{s}=m_{s}/\rho=9\times10^{6}{\mathrm{~kg/2160~kg/m^{3}=4167~m^{3}}}It can be a storage in the form of a cube with a side length of 16.1 m.