Abstract
Solar power microturbines are required to produce steady power despite the fluctuating solar radiation, with concerns on the dispatchability of such plants where thermal energy storage may offer a solution to address the issue. This paper presents a mathematical model for performance prediction of a honeycomb sensible-heat thermal energy storage designed for application of concentrated solar power microturbine. The focus in the model is to consider the laminar developing boundary layers at the entry of the flow channels, which could have a profound effect on the heat-transfer coefficient due to large velocity and temperature gradients, an effect which has not been considered in the modelling of such storage systems. Analysing the thermal and hydrodynamic boundary layer development, the Nusselt number and the friction factor were evaluated using a validated conjugate heat-transfer method. The simulations results were used to develop accurate regression functions for Nusselt number and friction factor. These formulations have been adopted within a one-dimensional model to evaluate the performance of the storage under different operating conditions. The model was in good agreement with conjugate heat transfer results with maximum relative error below 2%. Two case studies are presented to demonstrate the applicability of the proposed methodology.
Highlights
The fluctuating and uncertain behaviour of renewable energy sources has led to concerns regarding the reliability of electric grids which incorporates them
The storage unit is designed for integration with a parabolic dish concentrated solar power plant operated by a micro gas turbine
The maximum relative error calculated for the friction factor is around 25%, while the average relative error is below 9% and the correlation coefficient is always above 0.995
Summary
The fluctuating and uncertain behaviour of renewable energy sources has led to concerns regarding the reliability of electric grids which incorporates them This challenge has created an increased interest in the development of energy storage systems. In comparison to other intermittent forms of renewable energy such as wind or photovoltaics, concentrated solar power (CSP) technologies have the potential for integration with cost-effective thermal energy storage to increase the dispatchability of the plant [3]. This is important for solar dish CSP plants with relatively small size (1–25 kWe) characterised by a low thermal inertia when compared with large-scale technologies such as parabolic through or solar tower [4].
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