1Phase change materials (PCM) with their high thermal storage density at almost isothermal conditions 2 and their availability at wide range of phase transitions promote an effective mode of storing thermal energy. 3Literature survey evidently shows that paraffins and salt hydrates provide better thermal performance at 4 competitive cost. This review paper is focused on the classification of various paraffins and salt hydrates. To 5 acquire long term productivity of LHS system, the thermo-physical stability of both paraffins and salt hydrates; 6 and their compatibility with various plastic and metallic container materials play a vital role. Likewise, the 7 lower thermal conductivity of PCMs affects the thermal performance of LHS system. This article reviews the 8 various thermo-physical performance enhancement techniques such as influence of container shape and its 9 orientation, employment of fins and high conductivity additives, multi-PCM approach and PCM encapsulation. 10The performance enhancement techniques are focused to improve the phase transition rate, thermal 11 conductivity, latent heat storage capacity and thermo-physical stability. This review provides an understanding 12 on how to maximize thermal utilization of PCM. This understanding is underpinned by an analysis of PCM- 13Container compatibility and geometrical configuration of the container.

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This article is focused on numerical analyses of commercially available metal-oxides as potential nano-additives for paraffin in thermal storage applications. Technical and economic prospects of metal-oxides based nano-PCMs are evaluated to help formulate selection criterion for nano-additives to achieve optimum thermal performance at acceptable cost. Numerical model based on enthalpy-porosity technique is developed which incorporates natural convection and transient variations in thermo-physical properties of nano-PCM. Numerical model is simulated for charging and discharging cycles of nano-PCMs in shell and tube heat exchanger at controlled temperatures. Transient simulations help in analysing heat transfer categorisation and isotherms distributions, solid-liquid interfaces propagations, charging and discharging rates, and overall thermal enthalpy. Inclusion of nano-particles increase the effective thermal conductivity and surface area for heat transfer, which results in enhanced charging and discharging rates. The conductive heat transfer, peak heat flux, charging and discharging rates are significantly enhanced by increasing volume concentration of nano-particles. The percentage enhancement in charging rates of SiO 2 based nano-PCM samples with 1% and 5% are 29.45% and 41.04%, respectively. Likewise, the discharging rates are improved by 21.09% and 30.08%, respectively. However, an increase in volume concentration reduces natural convection and overall thermal enthalpy, and increases total cost of nano-PCM. For instance, the percentage reductions in total enthalpy of CuO based nano-PCM samples with 1% and 5% volume concentrations are 8.01% and 32.14%, respectively. Likewise, the total costs are increased from 14.26 €/kg for base paraffin to 70.89-309.33 €/kg, respectively. Hence, the significance and originality of this research lies within evaluation and identification of preferable metal-oxides with higher potential for improving thermal performance at reasonable cost. This article will help bring significant impact to large-scale utilisation of low-carbon and clean energy technology in domestic and commercial applications.

1In this article, the discharging cycles of paraffin in novel latent heat storage (LHS) unit are 2 experimentally investigated. The novel LHS unit includes shell and tube with longitudinal fins based 3 heat exchanger and paraffin as thermal energy storage material. The experimental investigations are 4 focused on identifying the transient temperature performance, effective mode of heat transfer, 5accumulative thermal energy discharge and mean discharge power of paraffin in LHS unit. Moreover, 6the influences of operating conditions such as inlet temperature and volume flow rate of heat transfer 7 fluid (HTF) on thermal behaviour of LHS unit are experimentally studied. The transient temperature 8profiles and photographic characterisation of liquid-solid transition of paraffin in LHS unit provide a 9 good understanding of temperature distribution and dominant mode of heat transfer. It is noticed that 10 during discharging cycles, natural convection has an insignificant impact on thermal performance of 11 LHS unit. However, due to inclusion of extended longitudinal fins, conduction is the dominant mode 12 of heat transfer. It is noticed that due to development of solidified paraffin around tubes and 13longitudinal fins, the overall thermal resistance is increased and thus, discharging rate is affected. 14 However, by regulating inlet temperature or volume flow rate of HTF, the influence of overall thermal 15 resistance is minimised. Mean discharge power is enhanced by 36.05% as the inlet temperature is 16reduced from 15 o C to 5 o C. Likewise, the mean discharge power is improved by 49.75% as the 17 volume flow rate is increased from 1.5 l/min to 3 l/min. Similarly, with an increase in volume flow 18 rate, the discharge time of equal amount of thermal energy 12.09 MJ is reduced by 24%. It is 19established that by adjusting operating conditions, the required demand of output temperature and 20 mean discharge power can be attained. Furthermore, this novel LHS unit can meet large scale thermal 21 energy demands by connecting several units in parallel and thus, it has potential to be employed in 22wide-ranging domestic and commercial applications. 23 24 Keywords 25 Thermal energy storage, Latent heat storage, Discharge cycle, Phase change materials, Heat transfer, 26 Shell and tube heat exchanger 27 28

Intense utilization of natural fuel resources is threatening the global environment and societal sustainability. It triggers up the need for finding environmental-friendly and sustainable sources of energy. In this perspective, microalgae have emerged as a potential alternative. Microalgae are featured with distinct ability to provide ecological services and respond to the sustainability challenges simultaneously. Microalgae can fix atmospheric CO2, valorize waste resources, and can produce a wide variety of bio-products. The promising features of microalgae pitch the idea of establishing a sustainable bio-refinery to draw multifaceted benefits and reinforce the objectives of resource efficient bio-economy. Unfortunately, in the last few years, preferential studies have been carried out to assess the potential of microalgae-based integrated bio-refinery. This review critically discussed the recent developments, opportunities, and barriers in the microalgae bioindustry and wastewater treatment. Particularly, microalgae potentials for biofuels and resources recovery are addressed towards sustainable biorefinery. Moreover, techno-economic and 2 commercial viability of microalgae-led bio-refinery is reviewed to drive this technology towards practicality.

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