Cost Of Thermal Energy Storage Research Articles

Effects of expanded graphite on NaNO3/semi-coke ash shape-stable phase change composites for thermal energy storage

As an alkaline industrial solid waste with a porous structure, semi-coke ash can have adverse effects on the environment if accumulated or buried in large quantities. The research group has previously used this material in combination with NaNO3 to prepare a shape-stable phase change composite. Building upon the previous research team, this work manufactured the shape-stable phase change composite by cold-compression hot-sintering method using NaNO3 as the phase change material, semi-coke ash as the skeleton material and an innovative addition of expanded graphite as the thermal conductivity enhancer to enhance thermal conductivity of phase change material. Then, key thermal performance, mechanical strength, chemical compatibility, microscopic morphology, economic efficiency and emission reduction capacity were investigated. Results demonstrated that the sample SS2 with 0.5 wt% expanded graphite performed best, which also presented a mechanical strength of 113.82 MPa, a thermal conductivity of 1.844 W/(m·K), and an excellent thermal energy storage density of 424.91 J/g between 100–400 °C; Both the thermal performance and mechanical strength of sample SS2 decreased to some extent after the heating/cooling cycles; The semi-coke ash, expanded graphite, and NaNO3 showed excellent chemical compatibility while both the thermal energy storage cost (0.022 ¥/kJ) and the raw material carbon emissions (1041 kg) of producing per ton sample SS2 in this work were far below traditional shape-stable phase change materials.

Corrosion-resistant thermal spray coatings for low-alloy steel in contact with molten nitrate salts in solar power plants

The longevity and the cost of thermal energy storage (TES) components in solar power plants is a matter of great concern. To address this issue, three kinds of thermal spray coatings (Ni-5Al, NiCoCrAlY, and CoNiCrAlY) were successfully deposited on the low-alloy steel (P91) substrate by high velocity oxygen fuel (HVOF) spraying process. The corrosion performance of the prepared coatings in Solar Salt (at 565 °C for 15 days) was evaluated in detail by gravimetric analysis, field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). Results revealed that all three coatings were quite dense and the substrates were generally well protected by the coatings. Compared with Ni-5Al and NiCoCrAlY coatings, the CoNiCrAlY coating exhibited the best corrosion performance owing to the formation of a dense oxide layer on the surface. Further, it was revealed that despite containing corrosion-resistant composition in NiCoCrAlY coating, the presence of a large number of phase interfaces could be the vulnerable regions that may result in local corrosion failure. Moreover, increasing the content of aluminum and using pre-alloyed powder may be an excellent solution to improve the performance of Ni-5Al coating.

Natural zeolites as host matrices for the development of low-cost and stable thermochemical energy storage materials

Advanced thermal energy storage technologies based on physical adsorption and chemical reactions of thermochemical materials (TCMs) are capable of storing large shares of renewable energy with high energy density. Further research and development is required to improve the performance and reduce the cost of these materials. A promising approach to developing low-cost TCM is to use natural zeolite adsorbents as host matrices in the development of salt-loaded composite TCM. In this study, the thermal properties of various species of low-cost zeolites from natural deposits across Canada were investigated. Two high purity crystal (HPC) zeolites from the Trans Canada (TC-HPC) and Juniper Creek (J-HPC) deposits in British Columbia were determined to have the highest water uptake capacity (0.145 g/g and 0.113 g/g, respectively) and enthalpy of adsorption (408 J/g and 304 J/g, respectively). Despite having approximately half of the water uptake capacity and adsorption enthalpy of the commercially available synthetic zeolite 13X, the cost of thermal energy storage ($CAD/kWhth) of the natural zeolites was determined to be 72–79% lower than that of the synthetic zeolite. Repeated adsorption and desorption experiments demonstrated the hydrothermal stability of the HPC zeolites over multiple charge and discharge cycles. Overall, the experimental results and cost analysis indicate that Canadian HPC zeolites are promising alternatives to synthetic zeolites in the pursuit of low-cost and stable TCM.

Exergo-economic analysis for screening of metal hydride pairs for thermochemical energy storage for solar baking system

The novelty of this research work is the exergo-economic analysis (including the cost of exergy destruction and exergy loss) of metal hydride based thermal energy storage system coupled with a solar bakery unit for the screening of metal hydride pairs (Case 1: pure MgH2/LaNi5& Case 2: V2O5 doped MgH2/LaNi5) for thermochemical energy storage. Firstly, a numerical simulation is performed by using COMSOL Multiphysics 5.3a software. Secondly, an economic and exergo-economic model is developed to calculate the annual levelized cost of the thermal energy storage system. The life-cycle economic assessment findings indicate that the Levelized thermal energy storage cost of the pure MgH2 based system (32.28 $ /kWhth) is 8.2 times higher than that of the V2O5 doped MgH2 system (3.954 $/kWhth). Moreover, an 87.75% decrease in cost was observed in Case 2 (V2O5 doped MgH2). Furthermore, Case 2 (V2O5 doped MgH2) can save 92.58 % of hydrogenation reaction time as compared to Case 1 (Pure MgH2). Ultimately, the selection of V2O5 based MgH2 as a thermal heat-storing medium is then assessed as a better option for the MHTES for the solar bakery unit (SBU). The findings of this research provide a clear insight into the mechanism of cost formation in the system.

Cost-effective ultra-high temperature latent heat thermal energy storage systems

The availability of cost-effective energy storage technologies with durations from 10 to 100 h is key for intermittent renewable energies, like wind or solar, to become a large share of the electrical grid power. Battery prices forecasted for the upcoming years are still too expensive; and storing the energy as heat instead of electricity, arises as a promising cheaper solution. Even if there is an efficiency penalty when converting heat back to electricity, the low cost of thermal energy storage (TES) systems is an important advantage. Besides, not always the heat stored in a TES system needs to be converted to electricity, as heat corresponds to about 50% of the global energy demand. In this work, the potential of Ultra-High Temperature Latent Heat Thermal Energy Storage (UH-LHTES), which can reach energy capacity costs below 10 €/kWh by storing heat at temperatures well beyond 1000 °C, is presented with the help of a Computational Fluid Dynamics (CFD) model. Modelling results, together with real materials performance and cost data, allow to estimate cost-efficiency boundaries for UH-LHTES systems for a range of sizes from 10 kWhth to 10 MWhth. The CFD model has been validated reproducing the real size and materials of a UH-LHTES prototype developed in the framework of the AMADEUS project. The CFD model is proven to be a reliable tool to reproduce the operation of a UH-LHTES system and it predicts quite precisely UH-LHTES prototype discharge rates and heat losses.

Review of Carnot Battery Technology Commercial Development

Carnot batteries are a quickly developing group of technologies for medium and long duration electricity storage. It covers a large range of concepts which share processes of a conversion of power to heat, thermal energy storage (i.e., storing thermal exergy) and in times of need conversion of the heat back to (electric) power. Even though these systems were already proposed in the 19th century, it is only in the recent years that this field experiences a rapid development, which is associated mostly with the increasing penetration of intermittent cheap renewables in power grids and the requirement of electricity storage in unprecedented capacities. Compared to the more established storage options, such as pumped hydro and electrochemical batteries, the efficiency is generally much lower, but the low cost of thermal energy storage in large scale and long lifespans comparable with thermal power plants make this technology especially feasible for storing surpluses of cheap renewable electricity over typically dozens of hours and up to days. Within the increasingly extensive scientific research of the Carnot Battery technologies, commercial development plays the major role in technology implementation. This review addresses the gap between academia and industry in the mapping of the technologies under commercial development and puts them in the perspective of related scientific works. Technologies ranging from kW to hundreds of MW scale are at various levels of development. Some are still in the stage of concepts, whilst others are in the experimental and pilot operations, up to a few commercial installations. As a comprehensive technology review, this paper addresses the needs of both academics and industry practitioners.

Oxidative stability performance of new azophenol derivatives as antioxidants in working fluids for high-temperature solar applications

In solar applications, the oxidation stability of heat transfer fluidsreducesthe thermal energy storage cost. In this work, the effect of new two azophenols, namely -2-sec-butyl-4-((3-chlorophenyl) diazenyl) phenol and 2-sec-butyl-4-((3-nitrophenyl) diazenyl)phenol, was studied to produce an oil that has good characteristics and is compatible with metals such asstainless steel, carbon steel, aluminum, and copper, which are generally used to manufacture pipes, heat exchangers, receivers, and storage tanks. The prepared compounds were characterized using spectroscopy analysis. The prepared compounds were added to a heat transfer fluid under operating conditions in the presence of iron and copper as catalysts. At different time intervals, the samples were tested by measuring the total acid number value. The results of this measurement show that compound II performed better than compound I. Additionally, the quantum chemical parameters were calculated. The theoretical calculations were compatible with the experimental results.

Modeling, transient simulations and parametric studies of parabolic trough collectors with thermal energy storage

For investigating the system response of parabolic trough collector heat generating system, a plant with parabolic trough collector field and two-tank molten salt thermal energy storage model with component-level control algorithm is developed for managing various working conditions. The model is transient inside the components and responds with hourly weather and demand data. The main purpose of this work is providing an alternative design methodology that focuses on the collector field, and storage size by investment, location, and load type.Using a simple economic model, the plant parameters are calculated, which contains only initial investment costs of the parabolic trough collector field and thermal energy storage costs. Depending on the economic model, various sizes of collector field and storage combinations are created at fixed initial investment costs in the mathematical model. A parametric study is performed by using the economic model simulating at several initial investment costs, two different locations in Turkey, and four different load profiles.As a result of the parametric study, maximum solar fraction cases are selected and the generalized trend is observed. The effect of thermal energy storage on the solar fraction is discussed and the change in thermal energy storage with optimum plant size is investigated. After the optimum investment, the linear increment trend of dispatchability is disappearing and increases asymptotically by increasing the plant and/or storage size. Later in this work, the significance of the load profile is emphasized, which should be one of the major design parameters for solar-powered energy systems.

Optimal Dispatch Model Considering Environmental Cost Based on Combined Heat and Power with Thermal Energy Storage and Demand Response

In order to reduce the pollution caused by coal-fired generating units during the heating season, and promote the wind power accommodation, an electrical and thermal system dispatch model based on combined heat and power (CHP) with thermal energy storage (TES) and demand response (DR) is proposed. In this model, the emission cost of CO2, SO2, NOx, and the operation cost of desulfurization and denitrification units is considered as environmental cost, which will increase the proportion of the fuel cost in an economic dispatch model. Meanwhile, the fuel cost of generating units, the operation cost and investment cost of thermal energy storage and electrical energy storage, the incentive cost of DR, and the cost of wind curtailment are comprehensively considered in this dispatch model. Then, on the promise of satisfying the load demand, taking the minimum total cost as an objective function, the power of each unit is optimized by a genetic algorithm. Compared with the traditional dispatch model, in which the environmental cost is not considered, the numerical results show that the daily average emissions CO2, SO2, NOx, are decreased by 14,354.35 kg, 55.5 kg, and 47.15 kg, respectively, and the wind power accommodation is increased by an average of 6.56% in a week.

Effects of sodium nitrate concentration on thermophysical properties of solar salts and on the thermal energy storage cost

Thermal energy storage (TES) systems are key components of concentrating solar power plants in order to offer energy dispatchability to adapt the electricity power production to the curve demand. Nitrate molten salts are the storage media used today in concentrated solar power plants. They are also used as heat transfer fluid (HTF) in the molten salt tower (MST) technology. Traditional MST plants work in the temperature range of 240–565 °C using the so-called solar salt, a mixture of 60–40 wt% of NaNO3 and KNO3. This study wants to optimize the thermal energy storage cost of the solar concentration technology by analysing different mixtures of solar salts, using different percentages of NaNO3 and KNO3 in the mixture. The new mixtures seek a reduction in the cost of the storage material while optimizing its physical and chemical properties. The study shows how an increase in the proportion of sodium nitrate for a new binary solar salt to 78–22 wt%, produces an increase in the heat capacity of the mixture by reducing the necessary inventory of salts in the system. However, the new salt presents an increase in the melting point, going from 240 °C to 279 °C, which makes the operation of the system difficult. The impact on the cost of this optimization in the performance of a commercial plant was analysed. The plant chosen to evaluate the impact is a tower technology plant with 85 MWe power and 13 h of storage. The study shows a LCOE reduction of up to 0.6% for the new mixture with higher sodium nitrate.

Annual comparative performance and cost analysis of high temperature, sensible thermal energy storage systems integrated with a concentrated solar power plant

The present study conducts a comprehensive comparative techno-economic analysis of some near-term sensible thermal energy storage (TES) alternatives to the ‘standard’ two-tank molten salt system for concentrated solar power (CSP) plants. As such, we conducted detailed, relative annual transient simulations for single-medium thermocline (SMT), dual-media thermocline (DMT), and shell-and-tube (ST) systems. To be consistent with recent literature, the DMT and ST systems use concrete with a porosity of 0.2 (e.g. where concrete occupies 80% of the system) as their low cost filler material. The systems were integrated into a validated 19.9MWe Gemasolar CSP model, which has a solar multiple of 2.5. For a relative analysis, the storage capacity of each TES alternative was fixed at 722MWhth (15 h storage) for all TES alternatives. Based on this capacity, a geometric optimization was performed on DMT and ST systems to maximize the discharged power and minimize the pressure drop. Using the optimum designs, it was found that a CSP plant with a two-tank molten salt system enables the highest amount of electricity generation in a year followed by the SMT and DMT systems, which resulted in 7% and 9% less electricity generation, respectively. As the worst performer, a CSP plant integrated with a ST system generates 20% less electricity over a year. This implies that despite having the same theoretical capacity, the real performance is not same for the alternatives. While these losses may seem egregious at first, large TES cost reductions are made possible in these alternatives due to the fact that a single tank or concrete can be used (noting that concrete is <1/20th the price per kg of molten salt). We propose herein that the true techno-economic advantage (or lack thereof) of choosing alternative TES systems should be judged by a ‘normalized cost of thermal energy storage (NCOTES)’ which normalizes the cost of storage systems with regards to their annual electricity generation capacity. According to our analysis, optimized DMT and ST systems without embedded pipes (e.g. bored or formed concrete) can achieve 55% and 46% reductions relative to the NCOTES of the two-tank system, respectively (with 650K as cut-off discharge temperature), while the SMT system has an 13% lower NCOTES than the two-tank system. With embedded pipes, however, the ST design has a higher NCOTES (+1% to +100%, depending on the discharge cut-off temperature), indicating that embedded piping is the biggest cost driver and that the elimination of piping should be a priority in ST systems. Overall, this study provides a methodology for the relative comparison of various sensible TES alternatives, and it gives insight into the most promising alternatives for moving beyond two-tank molten salt systems.

Economic Evaluation of Shell-and-tube Latent Heat Thermal Energy Storage for Concentrating Solar Power Applications

Abstract The capital cost and thermal performance of shell and tube type latent heat thermal energy storage (LHTES) is analyzed in this paper. In order to get the lowest cost of the shell and tube LHTES, the ideal one dimensional heat transfer model is used. The discharging process of shell and tube LHTES working in solar thermal power tower system and parabolic trough solar thermal power system were numerically simulated using lumped capacitance method. The capital cost of the LHTES was calculated considering different volume ratio of tubes and tube length. The results of the economic analysis shows that the tube and shell LHTES is a promising method to reduce the thermal energy storage cost.

Material Selection in Engineering Design Using Choquet Integral-Based Linguistic Operators under Hybrid Environment

The performance of phase change materials directly influences the performance and cost of thermal energy storage, and it is the first important task to select the suitable phase change materials for use in a particular kind of applications. Due to the decision maker’s knowledge field and the nature of evaluated attributes, assessments are always with different formats, which were first unified into the linguistic terms in the basic linguistic term set. Two-additive fuzzy measures were used to model criteria interactions by pairs, and the special expressions of Marichal entropy and Choquet integral were derived, more convenient to use in practice. Fuzzy measures were identified based on the maximum of Marichal entropy, and, based on the Choquet integral, the linguistic hybrid weighted geometric averaging with interaction was developed for integrating the individual attributes’ ratings. The detailed decision making procedure was illustrated, with the material 33.2Cu as the optimal solution, which by comparison is reasonable and trustworthy.

Spatial and temporal modeling of sub- and supercritical thermal energy storage

This paper describes a thermodynamic model that simulates the discharge cycle of a single-tank thermal energy storage (TES) system that can operate from the two-phase (liquid–vapor) to supercritical regimes for storage fluid temperatures typical of concentrating solar power plants. State-of-the-art TES design utilizes a two-tank system with molten nitrate salts; one major problem is the high capital cost of the salts (International Renewable Energy Agency, 2012). The alternate approach explored here opens up the use of low-cost fluids by considering operation at higher pressures associated with the two-phase and supercritical regimes.The main challenge to such a system is its high pressures and temperatures which necessitate a relatively high-cost containment vessel that represents a large fraction of the system capital cost. To mitigate this cost, the proposed design utilizes a single-tank TES system, effectively halving the required wall material. A single-tank approach also significantly reduces the complexity of the system in comparison to the two-tank systems, which require expensive pumps and external heat exchangers.A thermodynamic model is used to evaluate system performance; in particular it predicts the volume of tank wall material needed to encapsulate the storage fluid. The transient temperature of the tank is observed to remain hottest at the storage tank exit, which is beneficial to system operation. It is also shown that there is an optimum storage fluid loading that generates a given turbine energy output while minimizing the required tank wall material.Overall, this study explores opportunities to further improve current solar thermal technologies. The proposed single-tank system shows promise for decreasing the cost of thermal energy storage.

Technology Advancements for Next Generation Falling Particle Receivers

The falling particle receiver is a technology that can increase the operating temperature of concentrating solar power (CSP) systems, improving efficiency and lowering the costs of energy storage. Unlike conventional receivers that employ fluid flowing through tubular receivers, falling particle receivers use solid particles that are heated directly as they fall through a beam of concentrated sunlight for direct heat absorption and storage. Because the solar energy is directly absorbed by the particles, the flux limitations associated with tubular central receivers are mitigated. Once heated, the particles may be stored in an insulated tank and/or used to heat a secondary working fluid (e.g., steam, CO2, air) for the power cycle. Thermal energy storage costs can be significantly reduced by directly storing heat at higher temperatures in a relatively inexpensive, stable medium. This paper presents an overview of recent advancements being pursued in key areas of falling particle receiver technology, including(1) advances in receiver design with consideration of particle recirculation, air recirculation, and interconnected porous structures; (2) advances in particle materials to increase the solar absorptance and durability; and (3) advances in the balance of plant for falling particle receiver systems including thermal storage, heat exchange, and particle conveyance.

Evaluation of thermal energy storage and recovery for an electrical energy mediator system

Energy storage both electrical and thermal is a rapidly emerging field of interest toward the development of more sustainable energy systems. The inherent inefficiencies associate with electrical storage can be partially overcome when thermal storage that collects and storage the waste thermal energy for alternative uses is integrated. Consequently, thermal energy storage systems are an enabling technology that will allow increased energy efficiency of a community, permit load levelling to reduce peak electricity demand. In order to facilitate a technology evaluation, a sizing strategy is developed for a phase change material (PCM) thermal storage system that determines system requirements under given thermal energy capture and recovery cycles. The sizing process utilizes a simplified one-dimensional heat transfer model that estimates melt times for a phase change material thickness without detailed geometry information. This melt time estimate allows the proportion of phase change material to fluid routing materials to be calculated, giving an estimate of material cost for the thermal storage cell to determine economic feasibility. The model is compared to both experimental data and computational fluid dynamics models in order to determine its limitations. Through a specific example of hydrogen based distributed electrical energy mediator system, the utility of the sizing model in determining the estimated cost of thermal energy storage is demonstrated.