Thermocline thermal energy storage is one of the most promising solutions for recovering waste heat in industrial plants. This paper aims to optimise the shape of a thermal energy storage to minimise its environmental impacts and maximise its exergy efficiency.
The first industrial thermocline storage was tested in Solar One CSP plant. This experiment proved that this technology was efficient and reliable . Hoffmann et al. studied the impact of HTF mass flow rate and filler particle diameter on energy efficiency.
Consequently, by raising the initial inlet temperature of charging or lowering that of the discharging, the thermocline heat storage tank is able to keep relatively high efficient discharging capacity under a large flow rate, which is significant to enhance the charging/discharging power.
High thermal performance of packed-bed thermocline tank with stable thermal stratification can be achieved by careful selection and determination of geometrical (packing), operational and thermophysical parameters.
The thermophysical properties of HTF and TESM are evaluated at average operating temperatures (310 °C). A lifetime of 25 years is assumed. Fig. 6. Dimensions of the Eco-Stock® thermal storage system Table 5. Specifications of the industrial thermocline tank
The optimisation method is applied to an existing industrial thermocline tank depicted in Fig. 6. This is an air/ceramic packed-bed system with a maximum storage capacity of 10 GJ (2.8 MWh). Its specifications are reported in Table 5. The thermophysical properties of HTF and TESM are evaluated at average operating temperatures (310 °C).