Energy Storage Reservoirs Research Articles

Feasibility study of RFX-mod2 performance improvement by additional magnetic energy storage

RFX-mod is an experimental fusion device built to explore and study plasma physics, especially in Reversed Field Pinch (RFP) configuration. RFX-mod allowed performing experiments with a plasma current up to 2 MA and obtaining stationary self-organized helical plasmas. Considering the results achieved so far, a significant upgrade of the device (RFX-mod2) is presently being implemented. This paper presents the feasibility study of a significant increase of the plasma current and flat-top duration via a limited upgrade of the RFX power supply system, without overstressing the poloidal windings or overcoming the power limits of the main step-down transformers (300 MVA) and maintaining the present set of thyristor converters units. The application of this concept to RFX-mod2 will be studied starting from the RFX-mod configuration, focusing on the needed modification of the present circuits and the desired improved performance. The increase of the maximum plasma current and flat-top duration, under the current and mechanical limits of the coils, can be reached using additional magnetic energy storage and a complete revision of the configuration and operating principle of the power supply system of the poloidal field coils. With this new operational concept, during the charging phase, the magnetizing winding is charged along with an additional inductor, which acts as an energy storage reservoir. The stored energy, in the order of 100 MJ, is transferred to the magnetizing winding, and thus to the plasma, via transfer resistors in the last phase of the plasma current ramp-up, to reach values of plasma current up to 2.6 MA.

TES-PD: A Fast and Reliable Numerical Model to Predict the Performance of Thermal Reservoir for Electricity Energy Storage Units

The spread of renewable resources, such as wind and solar, is one of the main drivers to move from a fossil-based to a renewable-based power generation system. However, wind and solar production are difficult to predict; hence, to avoid a mismatch between electricity supply and demand, there is a need for energy storage units. To this end, new storage concepts have been proposed, and one of the most promising is to store electricity in the form of heat in a Thermal Energy Storage reservoir. However, in Thermal Energy Storage based systems, the critical component is the storage tank and, in particular, its mathematical model as this plays a crucial role in the storage unit performance estimation. Although the literature presents three modelling approaches, each of them differs in the considered parameters and in the method of modelling the fluid and the solid properties. Therefore, there is a need to clarify the model differences and the parameter influences on plant performance as well as to develop a more complete model. For this purpose, the present work first aim is to compare the models available in the literature to identify their strengths and weaknesses. Then, considering that the models’ comparison showed the importance of adopting temperature-dependent fluid and storage material properties to better predict the system performance, the authors developed a new and more detailed model, named TES-PD, which works with time and space variable fluid and solid properties. In addition, the authors included the tank heat losses and the solid effective thermal conductivity to improve the model accuracy. Based on the comparisons between the TES-PD model and the ones available in the literature, the proposal can better predict the first cycle charging time, as it avoids a 4% underestimation. This model also avoids overestimation of the delivery time, delivered energy, mean generated power and plant round-trip efficiency. Therefore, the results underline that a differential and time-accurate model, like the TES-PD, even if one-dimensional, allows a fast and effective prediction of the performance of both the tank and the storage plant. This is essential information for the preliminary design of innovative large-scale storage units operating with thermal storage.

Development of rock sensible heat storage system: Modeling of a hematite reservoir

Although there is a significant increase in energy dependence in recent years, existing renewable energies cannot keep up with the continuously energy demand due to their natural intermittency. One possible solution is the use of heat storage systems, capable of accumulating large amounts of energy over long periods of time when there is excess of energy production and return it when necessary. In this paper, we describe the methodology used to characterize the thermal and physical properties of a Thermal Energy Storage (TES) reservoir filled with crushed hematite ore from Moncorvo, Portugal, aimed at storing energy as sensible heat. Moreover, a numerical model is proposed, which uses an inversion routine to simulate the temperatures inside the reservoir during heating and cooling periods. The results obtained allow to infer that hematite can absorb enough energy to be chosen as a heat storage material, since it has a high specific heat and a low thermal conductivity, which prevent heat loss. In addition, the model allowed for the calculation of the efficiency of a large-scale energy storage system.

MYH9 facilitates autoregulation of adipose tissue depot development.

White adipose tissue not only serves as a reservoir for energy storage but also secretes a variety of hormonal signals and modulates systemic metabolism. A substantial amount of adipose tissue develops in early postnatal life, providing exceptional access to the formation of this important tissue. Although a number of factors have been identified that can modulate the differentiation of progenitor cells into mature adipocytes in cell-autonomous assays, it remains unclear which are connected to physiological extracellular inputs and are most relevant to tissue formation in vivo. Here, we elucidate that mature adipocytes themselves signal to adipose depot–resident progenitor cells to direct depot formation in early postnatal life and gate adipogenesis when the tissue matures. Our studies revealed that as the adipose depot matures, a signal generated in mature adipocytes is produced, converges on progenitor cells to regulate the cytoskeletal protein MYH9, and attenuates the rate of adipogenesis in vivo.

Brayton-cycle-based pumped heat electricity storage with innovative operation mode of thermal energy storage array

As a novel physical energy storage technology with energy densities and efficiencies comparable to advanced compressed air energy storage, pumped heat electricity storage (PHES) has attracted significant attention in recent years. Arrayed multi thermal energy storage (TES) reservoirs have promising potential for large-scale TES storage, and the operation modes of TES arrays significantly affect the PHES system which has not been investigated in presented studies. By performing numerical simulations considering coupling dynamics, transient heat transfer, and thermodynamics, the transient behavior of the cyclic steady-state of a 10 MW/8 h Joule–Brayton PHES system under four operation modes including series, parallel, in-sequence, and the innovative “temperature complementation” is investigated in this study. The PHES with series-connected reservoirs arrays has a round-trip efficiency of 64.9% and a delivery variation of 43.1%; these results are better than those obtained under the parallel and in-sequence operating modes of the singular reservoir PHES. Under the innovative “temperature complementation” operation mode, the delivery stability improves further with a variation of 13.2%. The TES reservoirs could be reduced to 1.8 times the minimum volume with a round-trip efficiency of 63%–65%. Such a TES array with the “temperature complementation” operation mode may facilitate the development and application of other fixed TES technologies by providing stable thermal energy delivery.

Using saline or brackish aquifers as reservoirs for thermal energy storage, with example calculations for direct-use heating in the Portland Basin, Oregon, USA

Tools to evaluate reservoir thermal energy storage (RTES; heat storage in slow-moving or stagnant geochemically evolved permeable zones in strata that underlie well-connected regional aquifers) are developed and applied to the Columbia River Basalt Group (CRBG) beneath the Portland Basin, Oregon, USA. The performance of RTES for heat storage and recovery in the Portland Basin is strongly dependent on the operational schedule of heat injection and extraction. We examined the effects of the operational schedule, based on an annual solar hot water supply pattern and a building heating demand model, using heat and fluid flow simulations with SUTRA. We show RTES to be feasible for supply of heating energy for a large combined research/teaching building on the Oregon Health and Science University South Waterfront expansion, an area of planned future development. Initially, heat is consumed to increase the reservoir temperature, and conductive heat loss is high due to high temperature gradients between the reservoir and surrounding rock. Conductive heat loss continues into the future, but the rate of heat loss decreases, and heat recovery efficiency of the RTES system increases over time. Simulations demonstrate the effects of varying heat-delivery rate and temperature on the heat production history of the reservoir. If 100% of building heating needs are to be supplied by combined solar/RTES, then the solar system must be sized to meet building needs plus long-term thermal losses (i.e., conductive losses once the system is heated to pseudo-steady state) from the RTES system. If the solar heating system barely meets these criteria, then during early years, less than 100% of the building demand will be supplied until the reservoir is fully-heated. The duration of supplying less than 100% of building demand can be greatly shortened by pre-heating the reservoir before building heating operations or by adding extra heat from external sources during early years. Analytic solutions are developed to evaluate efficacy and to help design RTES systems (e.g., well-spacing, thermal source sizing, etc.). A map of thermal energy storage capacity is produced for the CRBG beneath the Portland Basin. The simulated building has an annual heat load of ∼1.9 GWh, and the total annual storage capacity of the Portland Basin is estimated to be 43,400 GWh assuming seasonal storage of heat yields water from which 10 °C can be extracted via heat exchange, indicating a tremendous heating capacity of the CRBG.

Existing and new arrangements of pumped-hydro storage plants

The energy sector is undergoing substantial transition with the integration of variable renewable energy sources, such as wind and solar energy. These sources come with hourly, daily, seasonal and yearly variations; raising the need for short and long-term energy storage technologies to guarantee the smooth and secure supply of electricity. This paper critically reviews the existing types of pumped-hydro storage plants, highlighting the advantages and disadvantages of each configuration. We propose some innovative arrangements for pumped-hydro storage, which increases the possibility to find suitable locations for building large-scale reservoirs for long-term energy and water storage. Some of the proposed arrangements are compared in a case study for the upper Zambezi water basin, which has considerable water storage limitations due to its flat topography and arid climate. Results demonstrate that the proposed combined short and long-term cycles pumped-storage arrangement could be a viable solution for energy storage and reduce the cost for water storage to near zero.

SAT-585 Autoregulation of Adipose Tissue Development

White adipose tissue not only serves as a reservoir for energy storage but also secretes a variety of hormonal signals and modulates systemic metabolism. A substantial amount of adipose tissue develops in early postnatal life, providing unique access to the formation of this important tissue. However, while a number of factors have been identified that can modulate the differentiation of progenitor cells into mature adipocytes in cell autonomous assays, it remains unclear which are connected to physiological extracellular inputs and are most relevant to tissue formation in vivo. We elucidated that mature adipocytes themselves signal to adipose depot-resident progenitor cells to direct depot formation in early postnatal life and gate adipogenesis when the tissue matures. Our studies reveal that, as the adipose depot matures, a previously unrecognized signal is generated in mature adipocytes that converges on progenitor cells to regulate the cytoskeleton and attenuate the rate adipogenesis in vivo. This signal toggles the adipose depots from developmental to tissue homeostatic levels of adipogenesis.

Potential application of Aloe Vera-derived plant-based cell in powering wireless device for remote sensor activation.

It is well proven that electrical energy can be harvested from the living plants which can be used as a potential renewable energy source for powering wireless devices in remote areas where replacing or recharging the battery is a difficult task. Therefore, harvesting electrical energy from living plants in remote areas such as in farms or forest areas can be an ideal source of energy as these areas are rich with living plants. The present paper proposes a design of a power management circuit that can harness, store and manage the electrical energy which is harvested from the leaves of Aloe Barbadensis Miller (Aloe Vera) plants to trigger a transmitter load to power a remote sensor. The power management circuit consists of two sections namely; an energy storage system that acts as an energy storage reservoir to store the energy harvested from the plants as well as a voltage regulation system which is used to boost and manage the energy in accordance to a load operation. The experimental results show that the electrical energy harvested from the Aloe Vera under a specific setup condition can produce an output of 3.49 V and 1.1 mA. The harvested energy is being channeled to the power management circuit which can boost the voltage to 10.9 V under no load condition. The harvested energy from the plants boosted by the power management circuit can turn ON the transmitter automatically to activate a temperature and humidity sensor to measure the environmental stimuli periodically with a ton of 1.22 seconds and toff of 0.46 seconds. This proves that this new source of energy combined with a power management circuit can be employed for powering the wireless sensor network for application in the Internet of Things (IoT).

Management of the Output Electrical Power in Thermoelectric Generators

Thermoelectric Generators (TEGs) are devices for direct conversion of heat into electrical power and bear a great potential for applications in energy scavenging and green energy harvesting. Given a heat source, the conversion efficiency depends on the available temperature difference, and must be maximized for optimal operation of the TEG. In this frame, the choice of materials with high thermoelectric properties should be accompanied by the identification of criteria for an optimal exploitation of the electrical power output. In this work, we briefly review the main properties of TEGs, focusing on the electrical power output and the thermal-to-electrical conversion efficiency. Besides, we discuss principles of operation of TEGs enabling the optimization of the electrical power output, based on the suitable choice of the electrical load. In particular, we comparatively present and discuss the conditions for matching the electrical load—yielding to maximum power transfer—and those for maximizing the conversion efficiency. We compare the two conditions applying them to the exploitation of a heat reservoir for energy storage and to the recovery of heat from a heat exchanger. We conclude that the difference between the two conditions is not significant enough to justify the complexity required by the implementation of the maximum efficiency. In addition, we consider the effect of the thermal contact resistance on the electrical power output. Using a simple thermal-electrical model, we demonstrate that the equivalent electrical resistance measured between the terminals of the TEG depends on the thermal exchange. Hence, for maximum power transfer, the electrical load of the TEG should not match its parasitic resistance, but the equivalent electrical resistance in each specific operating conditions, which determine the thermal fluxes. The model can be applied for the development of efficient alternative algorithms for maximum power point tracking.

A simple passive 390 mV ac/dc rectifier for energy harvesting applications

This paper reports a simple, discrete, ac/dc rectifier architecture intended for magnetic energy harvesters that functions with ac input voltages as low as 390 mVpk. The proposed four NMOS rectifier (4NR) employs cross-connected, saturated-load NMOS inverters. The circuit is completely passive, exhibits good low-voltage performance, consists of only four components for small footprint, and requires no additional blocking diode to prevent power flow from the load. At 2 Vpk input, the 4NR exhibits a power efficiency of 93 % and 400 μW of output power. The 4NR is also successfully connected to an off-the-shelf TI BQ25504 dc/dc converter + battery management chip and shown to charge both capacitor and lithium-ion battery energy storage reservoirs.

Chance-Constrained Scheduling of Underground Pumped Hydro Energy Storage in Presence of Model Uncertainties

Abandoned underground quarries or mines may be rehabilitated as natural reservoirs for underground pumped hydro energy storage (UPHES). In addition to the inherent modeling inaccuracies of the traditional PHES that arise from, e.g., approximating the nonlinear pump/turbine head-dependent performance curves, the optimal operation of these underground plants is also affected by endogenous model uncertainties. The latter typically arise from a limited knowledge of the physical characteristics of the system such as the geometry and hydraulic properties of the underground cavity. In this paper, chance-constrained programming is leveraged to immunize the day-ahead scheduling of an UPHES owner against both these model uncertainties and the modeling approximations. The proposed method is tested on a fictitious UPHES system using an existing underground quarry as lower reservoir. Results demonstrate that the methodology allows finding a compromise between conservativeness and economic performance, while being computationally efficient. This model may thus be integrated in the daily scheduling routine of UPHES owners, or may help regulators and system operators to better estimate the available flexibility of such resources.

Cyclic transient behavior of the Joule–Brayton based pumped heat electricity storage: Modeling and analysis

Pumped heat electricity storage (PHES) has the advantages of a high energy density and high efficiency and is especially suitable for large-scale energy storage. The performance of PHES has attracted much attention which has been studied mostly based on steady thermodynamics, whereas the transient characteristic of the real energy storage process of PHES cannot be presented. In this paper, a transient analysis method for the PHES system coupling dynamics, heat transfer, and thermodynamics is proposed. Judging with the round trip efficiency and the stability of delivery power, the energy storage behavior of a 10 MW/4 h PHES system is studied with argon and helium as the working gas. The influencing factors such as the pressure ratio, polytropic efficiency, particle diameters, structure of thermal energy storage reservoirs are also analyzed. The results obtained indicate that, mainly owing to a small resistance loss, helium with a round-trip efficiency of 56.9% has an overwhelming advantage over argon with an efficiency of 39.3%. Furthermore, the increases in the pressure ratio and isentropic efficiencies improve the energy storage performance considerably. There also exit optimal values of the delivery compression ratio, particle sizes, length-to-diameter ratios of the reservoirs, and discharging durations corresponding to the maximum round-trip efficiency and preferable discharging power stability. The above can provide a basis for the optimal design and operation of the Joule–Brayton based PHES.

Impact of drilling mud on chemistry and microbiology of an Upper Triassic groundwater after drilling and testing an exploration well for aquifer thermal energy storage in Berlin (Germany)

After completion of an exploration well, sandstones of the Exter Formation were hydraulically tested to determine the hydraulic properties and to evaluate chemical and microbial processes caused by drilling and water production. The aim was to determine the suitability of the formation as a reservoir for aquifer thermal energy storage. The tests revealed a hydraulic conductivity of 1–2 E-5 m/s of the reservoir, resulting in a productivity index of 0.6–1 m3/h/bar. A hydraulic connection of the Exter Formation to the overlaying, artesian “Rupelbasissand” cannot be excluded. Water samples were collected for chemical and microbiological analyses. The water was similarly composed as sea water with a maximum salinity of 24.9 g/L, dominated by NaCl (15.6 g/L Cl and 7.8 g/L Na). Until the end of the tests, the water was affected by drilling mud as indicated by the high pH (8.9) and high bicarbonate concentration (359 mg/L) that both resulted from the impact of sodium carbonate (Na2CO3) additives. The high amount of dissolved organic matter (> 58 mg/L) and its molecular-weight distribution pattern indicated that residues of cellulose, an ingredient of the drilling mud, were still present at the end of the tests. Clear evidence of this contamination gave the measured uranine that was added as a tracer into the drilling mud. During fluid production, the microbial community structure and abundance changed and correlated with the content of drilling mud. Eight taxa of sulfate-reducing bacteria, key organisms in processes like bio-corrosion and bio-clogging, were identified. It can be assumed that their activity will be affected during usage of the reservoir.

Photorechargeable Lithium-Ion Battery Electrode Based on Nanocrystals of Anatase TiO2 Combining Energy Conversion and Storage

The intermittent nature of renewable energies, in particular solar, limits its utilization at demand. Its hybridization with an energy storage reservoir is required, such as an electrochemical battery, to accommodate the balance between grid delivery and consumer demand. Although photovoltaic and batteries are two mature technologies widespread, their combination require electronics management, good assessment on both power dimensioning and ageing of each component, and still require a substantial cost reduction to become competitive with fossil fuels and nuclear. With long term view, the approach of bridging together the functions of solar conversion and its storage at the molecular level is worth attention for both scientific and technological point of view to pave the way towards photo-rechargeable ion batteries or non-intermittent photovoltaic displays. Tributsch in the early 80’s demonstrated the possibility to trigger light-induced interfacial ion transfer in mixed electronic/ionic semi-conductors as a result from the charge separation process within the depletion region (1). Up to now, the charges stored in such materials are only confined to the extreme surface (energy density less than 1 Wh/Kg), limited by the Debye length of the space charge layer (2). In this presentation, we will expose our strategy based on anatase TiO2 nanocrystals of 4 nm size assembled in carbon-free electrode to overcome this limitation. Anatase TiO2 with its n-type semi-conducting properties affords the de-insertion of lithium ions under illumination to counterbalance the hole transfer to Ti3+ induced by light. As a result from downsizing to such a nanoscale, surface reactions are promoted with respect to the total volume of particles. Consequently, our results, which will be discussed in-depth, show the possibility to quantitatively photorecharge an electrode of ca. 700 µAh/cm2 capacity in about one hour light exposure (Fig. 1). Both the mechanism and electrode performances will be discussed during this communication. Figure 1

The effect of the injection salinity and clay composition on aquifer permeability

Seasonal energy storage can be achieved by injecting hot or cool water into underground, but when the brine aquifer is used as the energy storage reservoir, there is the problem of permeability reduction, even channel blocking due to the release, immigration and deposit of colloidal particles. Aiming to find the effect of clay mineral compositions and the injection fluid salinity on the permeability of the brine aquifer, an experimental study was carried out using sand column. When the sand samples contain illite, montmorillonite and kaolinite, the permeability characteristics were tested with the injection fluid salinity ranging from 0 to 5g/L. Results indicate that clay minerals are the most important factor that influences the permeability of the brine aquifer and montmorillonite causes the largest permeability reduction; the effect of injection salinity is weaker than the clay minerals and the permeability characteristics of all of the three tested sand samples have abnormal change in the injection concentration ranging from 2g/L to 4g/L. That concentration range should be avoided when using the brine aquifer as the thermal energy storage reservoir.

Novel concepts of increasing energy storage capacity at Pumped Storage Power plants

The paper presents two novel concepts for increasing energy storage capacity at Pumped Hydro Storage (PHS) plants that are planned, being constructed or already exist. Both concepts make use of compressed air, but unlike other storage technologies that utilize compressed air, the air is not intended as the energy storage itself, it is a working fluid for moving water. By using compressed air, it is possible to utilize storage volumes that are positioned below the original upper reservoir in PHS plants. The two concepts presented here uses this principle, one by inflatable air bags positioned below the lower reservoir level, and the other by excavation of underground reservoirs that serve as the increased storage volume. The necessary operation comes at an efficiency penalty, but the energy storage reservoir will have an increase in size, without any new dam being built or existing water levels rise. This makes it ideal for retrofitting at existing PHS plants, which would increase the energy storage capacity as well as making it possible to install additional power generating capacity.

Optimization for Operation and Design of Solar-Hydro Pump Energy Storage Using GAMS

Mae Sariang is remote area about 200 kilometers from main substation, which creates several problems of power system operation, specially losses and reliability. This paper studies the optimize operation and design sizing of lower reservoir and pump station for hydro pump energy storage in order to maximize profit. The system is modelled using GAMS. Data in analysis are based on load, power generation from solar farm, natural stream flowed profile in Mae Sariang area. From the simulation results, the optimized size of hydro pump storage should be 6.6 MW, the size of pump at 2.07 MW, the lower reservoir volume capacity at least 20,731 cubic meter. The maximum profit is 56.45 million baht per year and optimized operation results in winter season have the excess energy will be used to pump the water to upper reservoir. Summer season the power system has to import power from grid and lower profit more than other season. Rainy season the power system can use power from hydro pump system as hydro power plant without drawing from the grid and best profit more than other seasons. Natural stream is important to sensitivity analyze it is the important variables that greatest profit. If in upstream problems with little rainfall, forests were destroyed. They will have problem solve in the future.

Wave propagation and thermodynamic losses in packed-bed thermal reservoirs for energy storage

This paper presents a numerical and theoretical analysis of thermal wave propagation in packed bed thermal reservoirs for energy storage applications. In such reservoirs, the range of temperatures encountered is usually such that the solid storage medium will exhibit significant changes in specific heat capacity. This in turn results in non-linear wave propagation and may lead to the formation of shock-like thermal fronts. Such effects have an impact on the exergetic losses due to irreversible heat transfer, and should be taken into account during the design and optimisation of the reservoirs. In the present paper, the emphasis is on thermal losses due to irreversible heat transfer. Frictional (pressure) losses and heat leakage between the storage medium and the environment are also important but are not considered here. The implications of the results for storage material, and particle size are discussed briefly in the context of loss minimisation.

Future Perspectives of Metabolomics in Adipocytes

Obesity and diabetes have reached global epidemic status in modern society. It is well known that metabolic syndrome leads to the progression of these diseases, eventually decreasing quality of life. In wake of these epidemics, adipose tissue has attracted significant attention because of its activity as an energy storage reservoir. Lately, even more importance has been given to the different classes of adipocytes including white, brown and beige adipose tissues. Most research has been focused on understanding molecular mechanisms of cellular signaling. However, not much is known about metabolic reprogramming and the influence of metabolic stimuli on adipocyte activity. Systems biology driven by untargeted metabolic profiling of adipocytes will bridge the gap between nutrition, metabolism and regulation of metabolic disorders. In particular, metabolomics, an emerging omic science, will play an important role in identifying biomarkers associated with these metabolic diseases. The aim of this review is to provide an overview of adipose tissue subclasses and their role in health and disease.