Development of Levelized Cost of Electricity, Life Cycle Greenhouse Gas Emissions and Net Energy Ratio of Solar-based Thermal Energy Storage Systems

Abstract

In this study, a data-intensive model was developed to evaluate the levelized cost of electricity (LCOE), the lifecycle greenhouse gas (GHG) emissions and the net energy ratio (NER) for thermal energy storage (TES) technologies, namely, sensible heat, latent heat, and thermochemical storage. To evaluate the LCOE, GHG emissions, and NER of storage systems, five scenarios were developed: two-tank indirect sensible heat storage (S1), two-tank direct sensible heat storage (S2), one-tank direct sensible heat storage (S3), latent heat storage (S4), and thermochemical storage (S5). A Monte Carlo simulation was performed for each scenario to examine the uncertainty in the LCOE, GHG emissions and NER. The GHG emissions for individual scenarios were found to be 13.52 – 46.86 gCO2eq/kWh (S1), 6.27 – 24.88 gCO2eq/kWh (S2), 4.53 – 18.79 gCO2eq/kWh (S3), 9.36 – 33.43 gCO2eq/kWh (S4), and 9.69 – 28.99 gCO2eq/kWh (S5). The results indicate that when uncertainty is considered, the GHG emissions can be greatly reduced in both S2 and S3. In S3, however, investment costs are also reduced (unlike in S2). The low investment costs are reflected in the LCOE. The LCOE ranges for individual scenarios are 0.08 – 0.59 $/kWh (S1), 0.03 – 0.22 $/kWh (S2), 0.02 – 0.16 $/kWh (S3), 0.06 – 0.43 $/kWh (S4), and 0.22 – 1.19 $/kWh (S5). The impact on LCOE was examined by varying the following key parameters; plant capacity, solar multiple, storage duration, capacity factor, and discount rate. Consequently, the impact on NER and GHG emission were examined by varying parameters such as heat exchanger efficiency, material input requirement, pump efficiency, emission factors for electricity source, storage duration, solar multiple, capacity factor, emission factors for Canadian provinces, and plant capacity. The NER ranges for individuals scenarios are 2.66 – 4.65 (S1), 13.34 – 18.59 (S2), 20.7 – 28.44 (S3), 0.21 – 2.03 (S4), and 5.63 – 8.57 (S5). In terms of NER, both S2 and S3 demonstrate a high potential to increase the energy output from TES systems. It can also be deduced from this study that S2 and S3 both have low investment costs and GHG emissions. For these reasons, S2 and S3 are more favourable scenarios to be implemented commercially. This study will provide key information for industry and policy makers in decision making and in determining which thermal storage technology is economically viable, energy efficient, and has the least environmental impact.