Long-term Storages Research Articles

Allocation Analysis of the Energy Storage System in Integrated Energy Systems Considering the Carbon Emissions and Cost

With the increasing integration of renewable energy into the power grid, the variability in its power generation has a growing impact on the stable energy supply of the system. The utilization of energy storage systems (ESSs) has been considered as an efficient approach to mitigate this effect. However, due to the different characteristics of different ESSs, it becomes an urgent issue about how to allocate the ESSs or combine different types of ESSs to maximize its performance. This study has constructed a new method to compare the performance of different ESSs, and analyze the strengths and weakness of mainstream ESSs with the real energy systems in Wuhan. It demonstrated that for short-term storage options such as superconducting energy storage, lithium-ion battery storage, and supercapacitor storage, larger capacities (2000kWh) yield better results. Conversely, the optimal allocation of long-term options like lead-acid batteries, flow batteries, and compressed air energy storage systems, depends on specific characteristics and wind patterns. Furthermore, this research also reveals that when considering the combination of involving both long-term (lead-acid battery) and short-term (superconducting battery) storages, it cannot simultaneously achieve optimal performance in terms of operating cost or carbon emissions reduction. For hybrid combinations such as supercapacitor-lithium-ion battery (short-term-short-term) or compressed air-energy-flow battery (long-term-long-term), it is crucial to ensure that the type with superior performance possesses maximum capacity.

Long-term effects of rewetting and drought on GPP in a temperate peatland based on satellite remote sensing data

Rewetting previously drained peatlands restores the critical function of peatlands as long-term carbon storages and sinks currently threatened by climate change and additional human-induced disturbances. Understanding and projecting the restoration process by rewetting, however, currently face a pressing challenge, the lack of consistent and gap-free records of important carbon cycling indicators of peatlands such as the gross primary production (GPP) over long term. In this study, we reconstructed the GPP in a rewetted peatland called Zarnekow (Fluxnet-ID: DE-Zrk) in Germany from 2000 to 2020 by combining long-term satellite observations and limited-term tower-based eddy covariance (EC) measurements based on Random Forest regression models. The R2 between the reconstructed data and EC data was 0.6. The reasonable reconstruction of long-term GPP enabled trend analysis that identified two distinct periods of decreasing/increasing in GPP due to rewetting and droughts. Rewetting in the winter of 2004 and 2005 stabilized GPP after a decreasing period. A drought in 2018 significantly increased GPP, and GPP remained high over the following two years. Furthermore, the month-specific trends show significant seasonality at this site, specifically, an increasing trend over the 21 years in the growing-season months of June to August and a decreasing trend in the other months. The most important variables for satellite-based estimates of GPP at this site include total evapotranspiration, land surface temperature, enhanced vegetation index and near-infrared reflectance vegetation index. Long-term analyses of carbon fluxes through the combination of satellite observations and EC measurements provide crucial insights into the restoration of carbon sequestration functions in rewetted peatlands.

Optimal design and operation of solar energy system with heat storage for agricultural greenhouse heating

A significant challenge of agricultural greenhouses is their high energy demand which is mainly satisfied by fossil fuels resulting in climate change impacts. In this paper, a joint design-operation linear optimization framework for a solar energy system with heat storage is developed to fulfill the agricultural greenhouse heating load. The energy system consists of solar collector, backup boiler, and short-long term heat storages. The developed framework is applied to reach minimum-cost solution. Then, the effects of emission reduction policies, greenhouse cultivation scheduling, natural gas price, and investment cost scenarios are investigated. Furthermore, a multi-objective optimization is performed in terms of minimizing CO2 emissions and total annual cost using epsilon-constraint method. The optimal energy system due to the minimum-cost solution includes a 1065 m2 solar collector and a 1265 kW boiler in combination with 967 kWh and 25 MWh short-term and long-term heat storages, respectively. The 30 % carbon reduction policy results in a 70.5 % increase in solar collector area. The selected optimal solution of the Pareto front, which is the closest solution to the ideal point, has 35.3 % more annual cost and 89.5 % less CO2 emissions compared to the minimum-cost solution.

Investigation of Combined Heating and Cooling Systems with Short- and Long-Term Storages

Modern buildings in cold climates, like Norway, may have simultaneous heating and cooling demands. For these buildings, integrated heating and cooling systems with heat pumps, as well as short-term and long-term thermal storage, are promising solutions. Furthermore, combining this integrated system with renewables aids in the transition to future sustainable building energy systems. However, cost-effectively designing and operating such a complicated system is challenging and rarely addressed. Therefore, this research proposed an integrated heating and cooling system that incorporated a short-term water tank and a long-term borehole thermal storage. Meanwhile, three operating modes: heating, cooling, and free cooling were defined based on different heating and cooling load conditions. A detailed system model was developed in MATLAB using heat pump manufacture data as well as simulated and measured building loads. Following that, sensitivity studies were performed to investigate the impacts of ground properties, thermal storage size, setpoint temperature, heat pump characteristics, and load conditions. The findings identified the crucial factors that influence the system’s overall energy efficiency and the functioning of the key system components. Particularly, it revealed that low cooling to heating ratios caused an imbalance in charging and discharging, further reducing the ground temperature and degrading the heat pump’s performance.

Comparison of sCO2 and He Brayton cycles integration in a Calcium-Looping for Concentrated Solar Power

Concentrated Solar Power is expected to play a crucial role to reach a sustainable power generation. Efficiency increase and development of long-term storages are the main aspects that could be further addressed to enhance the Concentrated Solar Power diffusion. In this context, the Calcium-Looping process is a promising opportunity for the ThermoChemical Energy Storage. Previous studies showed that, between the indirect integrations, Brayton cycles operating with supercritical CO2 or Helium are an interesting alternative. However, since their discussion has been developed in separate works, a detailed comparison of these integrations is lacking. The purpose of the present study is to find the differences, similarities and important aspects that characterize the two systems, performing a comparison in energy, economic and technical terms. Results show that choosing the He power block allows to reach the highest performances, while the cheapest alternative is the sCO2 cycle. Compression, regeneration, and high-temperature heating are the most important aspects for the He integration, differently from the case with sCO2, where only the regeneration process determines changes of the plant benchmarks. The comparison does not highlight univocally a better option, but according to the criteria required is possible to evaluate the most suitable alternative.

Optimizing trading decisions of wind power plants with hybrid energy storage systems using backwards approximate dynamic programming

On most modern energy markets, electricity is traded in advance and a power producer has to commit to deliver a certain amount of electricity some time before the actual delivery. This is especially difficult for power producers with renewable energy sources that are stochastic (like wind and solar). Thus, short-term electricity storages like batteries are used to increase flexibility. By contrast, long-term storages allow to exploit price fluctuations over time, but have a comparably bad efficiency over short periods of time.In this paper, we consider the decision problem of a power producer who sells electricity from wind turbines on the continuous intraday market and possesses two storage devices: a battery and a hydrogen based storage system. The problem is solved with a backwards approximate dynamic programming algorithm with optimal computing budget allocation. Numerical results show the algorithm's high solution quality. Furthermore, tests on real-world data demonstrate the value of using both storage types and investigate the effect of the storage parameters on profit.

Designing dual-defending system based on catalytic and kinetic iron Pyrite@C hybrid fibers for long-life room-temperature sodium-sulfur batteries

The poor conductivity and severe polysulfide dissolution greatly restrict the development of room-temperature sodium-sulfur (RT-Na/S) batteries. To address these issues, a dual-polysulfide-defending system based on catalytic and kinetic hybrid fibers is designed to realize high-performance and long-life for RT-Na/S batteries. The hollow carbon fibers filled with yolk-shell FeS2/C hollow nanocubes (FeS2[email protected]) are constructed as the flexible sulfur host. The highly conductive and porous network ensures fast electron/ion transports and facilitates high mass loading. More impressively, the polar FeS2 boxes ensure the strong chemical binding and high catalytic redox reaction on polysulfides, which produce the first defense on polysulfide shuttle. Meanwhile, the FeS2@C/carbon nanotubes (CNT) hybrid film works as the modifying layer on the separator, which builds the second defense to ion shuttle. Taken the advantages of both dual-polysulfide-defending system and the hierarchical polar electrode, the RT-Na/S battery achieves superior high-rate capability, long-term cycling stability and high energy storages. It obtains an ultralow capacity decay rate (0.024%) during 1000 cycles at the rate of 2C with a high mass loading of 7.6 mg cm−2. Therefore, this work not only designs a freestanding kinetic and catalytic host for sulfur electrodes, but also provides a new design on RT-Na/S batteries to realize long life, superior rate capability and high energy storage synchronously.

Preliminary analysis of long‐term storage requirement in enabling high renewable energy penetration: A case of East Asia

Integrating a high penetration of renewable energy for developing sustainable and low-carbon electric energy system is becoming a common trend around the world. Many studies have evaluated the energy storage requirement for accommodating variable renewable energy (VRE). However, in the situation of high renewable penetration, there will be a huge potential requirement of long-term energy storage for addressing the seasonal energy imbalance between VRE and load demand. Thus, a key element of evaluating the storage demand in enabling high VRE penetration is identifying the timescales of storage needed and the economic combination of long-term and short-term energy storages. This is neglected in existing researches. In this study, we quantitatively analyse the role of long-term seasonal storage in enabling high VRE penetration. A generation expansion planning model is formulated to optimise the least-cost generation portfolio with a renewable penetration target. Based on the proposed model, an empirical analysis for East Asia in 2050 is performed. The results indicate that (1) long-term storage contributes to addressing the long-term energy imbalance issue, (2) the optimal duration time of long-term storage is around 720 h (a month), and (3) the long-term storage becomes economical when the renewable penetration is above 70% (54.2% VRE penetration).

Sizing and performance analyses of a combined heating and cooling system with the integration of short- and long-term storages

Technological advancements in the utilization of renewable energy sources have unveiled potentials for increasing building energy efficiency. Integrating heat pump-based energy systems with thermal storages is a suitable option to meet the thermal requirements of modern buildings and exploiting the available renewable energy sources. However, how to size the main components of a heat pump-based energy system with the integration of short- and long-term storages is not yet well explored. Therefore, this study focused on the design and performance analyses of an integrated heating and cooling system consist of a heat pump, borehole long-term thermal storage, and hot water tank short-term thermal. Heat pump models were introduced as parametric models based on the producer data. The dynamic thermal model of the energy system was developed and analysed in MATLAB. Different combinations of heating and cooling loads were tested. Integration of cooling and heating systems was discussed through different operation strategies and challenges were addressed. The results of the parametric analysis identified the key parameters affecting the design of components and efficiency of the system. Moreover, the results showed that lower cooling to heating load ratio leads to an excessive reduction of the ground temperature and overall efficiency over the long-term operation.

The impact of ventilation conditions on the quality of Rio Grande Russet tubers during long-term cold storage

Abstract The effect of speed and duration of ventilation fans on the quality of russet potatoes (Rio Grande Russet) stored at 5 °C ± 2 and 95% RH ± 5 in 2016 and 2017 seasons was investigated. Three fans moved air at three rates: 52 cubic feet per minute (CFM), 13 CFM, or 0.6 CFM and operated under continuous or intermittent control. This investigation included a zero-ventilation control. The tubers were analyzed periodically for weight loss, texture, ethylene production, respiration rate, sprouting incidence, power consumption, and nutritional value (total phenolics, total flavonoids, reducing sugars, and ascorbic acid) during the storage period. The results indicated that the rate of weight loss was higher under continuous high CFM ventilation. Intermittent ventilation at 0.6 CFM significantly reduced weight loss and have turgid tubers when compared with the control. There was a significant difference in sprouting rate and power consumption between continuous and intermittent ventilation. Continuous ventilation at 52 CFM significantly increased total flavonoid content and decreased reducing sugars compared to intermittent ventilation at 0.6 CFM. This study indicates the importance of using slow and medium CFM fans in long-term potato storages to reduce tuber weight loss and power consumption.

Stability Evaluation of DMT and Harmala Alkaloids in Ayahuasca Tea Samples.

Ayahuasca tea is a hallucinogenic beverage used for religious purposes in Brazil and many other countries that has therapeutic potential in the treatment of some mental health disorders. In the context of psychedelic research, quantification of the tea’s main alkaloids prior to its administration in animal or human studies is essential. For this reason, this study aims to provide information regarding the stability of the main ayahuasca alkaloids (dimethyltryptamine, DMT; harmine, HRM; tetrahydroharmine, THH; harmaline, HRL) in three different conditions: (1) A year stored in a refrigerator either in plastic or glass containers, (2) seven days at 37 °C to reproduce usual mail transportation, and (3) after three freeze–thaw cycles. Samples were quantified after a dilute-and-shoot procedure using liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). There was no significant degradation of DMT concentration over time in all tested conditions. Harmala alkaloids (THH, HRL, and HRM) showed important variations after long-term and high-temperature storages. Although DMT has proven to be stable in all studied conditions, the harmala alkaloids revealed intense degradation and even concentration increment. This may be caused by degradation, alkaloid inter-conversion, and leaching from tea precipitate material. Therefore, ayahuasca quantification before administration in controlled sets is mandatory.

Hydroclimatic influences and physiographic controls on phosphorus dynamics in prairie pothole wetlands

While wetlands are known as long-term storages or sinks for contaminants, not all are equally effective at trapping phosphorus (P). The prevalence of P-sink behavior in prairie pothole wetlands remains unclear, especially across gradients of human disturbance. The objectives of the current study were three-fold: (1) characterize the spatiotemporal variability of wetland hydrology and wetland water P concentration across a range of prairie potholes; (2) establish the propensity of different pothole wetlands to act as sources or sinks of P; and (3) assess the potential controls of climatic conditions, landscape characteristics, wetland soil physiochemical properties and local hydrology on source versus sink dynamics. Ten intact and three consolidated (i.e., drained) wetlands located in southwestern Manitoba, Canada, were monitored for water level fluctuations and water soluble reactive P (SRP) concentration over two years with contrasting antecedent wetness conditions. Soil cores were also collected to measure soil physiochemical properties such as the equilibrium phosphorus concentration (EPC). Water column SRP concentrations were compared to EPC values to infer the time-variable source versus sink behavior of each of wetland. Statistical analyses were then performed to assess whether the source versus sink behavior of individual wetlands could be linked to their physiographic or hydrologic characteristics. Results show that some wetlands persistently acted as P sinks while others switched between source and sink behavior. Persistent P-sink behavior was more common with intact wetlands, as opposed to consolidated wetlands. Wetland soil texture, storage volume and short-term water level fluctuations appeared to control the source versus sink behavior of individual wetlands. The dominant controls on P-sink behavior identified under dry conditions were, however, different from those identified under wetter conditions. This study therefore highlights the importance of considering the non-stationary nature of P-sorption dynamics and their controls, even at sub-annual timescales, in the prairie pothole region.

Optimization of grid-connected microgrid consisting of PV/FC/UC with considered frequency control

In this paper, ultracapacitors are used as short-term storages for the frequency control of grid-connected microgrid that consists of photovoltaic panels, fuel cells, and the battery packs as long-term storages. Fuel cells and battery packs have delays in load tracking; therefore, ultracapacitors are used to compensate for the sudden power fluctuations in the microgrid that occur due to the output power uncertainty of the PV arrays and the loads required in the microgrid, as well as the sudden interruption of the main grid. The microgrid consists of interruptible and uninterruptible loads. When the total produced power in the microgrid, in addition to the purchased power from the grid, cannot satisfy the demand, first, the interruptible loads, and then the uninterruptible loads, are interrupted. In this paper, the forced outage rate of each component and some notions of the reliability are considered for the microgrid. To ensure the system's reliability, the uncertainty of the PV power and load demand is considered.

Heat Transport in Evacuated Perlite Powders for Super-Insulated Long-Term Storages up to 300 °C

Vacuum super insulation (VSI) with expanded perlite powder is commonly used at cryogenic temperatures, but principally can also be adapted to applications at higher temperatures, such as the long-term storage of hot water in solar thermal systems. Due to the lack of experimental data in the respective temperature range, especially without external load, thermal conductivity measurements have been performed with commercial perlite powder up to 150°C mean sample temperature, corresponding to storage temperatures of around 300°C. Two different experimental geometries have been used: a guarded hot plate (GHP) setup and a cut-off concentric cylinder (CCC) apparatus. Furthermore, the radiative heat transport has been determined separately by extinction measurements using Fourier transform infrared (FTIR) spectroscopy. In addition to the laboratory experiments, a real-size prototype of a solar VSI-storage tank with 16.4 m3 water storage volume has been constructed, and the effective thermal conductivity of the perlite insulation has been determined from a heat loss measurement. The heat transport in evacuated perlite has also been treated theoretically using common models and approaches for gas heat conduction, solid-body conduction and heat transfer by thermal radiation. For the coupling between solid-body and gas conduction which occurs in the intergranular spaces of a powder material, a simple model has been developed. The total effective thermal conductivity λeff of a vacuum super insulation with dry, evacuated perlite powder (p≤0.01 mbar,ρ≈60 kg/m3) amounts to 0.007–0.016 W/mK for mean sample temperatures between 50°C and 150°C, compared to 0.003–0.005 W/mK at cryogenic temperatures. For the real-size storage prototype, the value λeff=0.009 W/mK has been obtained at T=90°C (storage temperature), p = 0.08 mbar and ρ=92.4 kg/m3, which compares to 0.03–0.06 W/mK for dry conventional storage insulations. With the applied theoretical models and approaches, the effective thermal conductivity of evacuated perlite and its individual contributions can successfully be described at different densities (55-95 kg/m3), compression methods, vacuum pressures (10-3-1000 mbar) and filling gases (air, Ar, Kr) up to mean sample temperatures of T=150°C. With regard to practical purposes, it has shown that vacuum super insulation with perlite is a suitable and economic method to achieve low thermal conductivities also at medium storage temperatures.

Effects of Al- and Mn-contents in the negative MH alloy on the self-discharge and long-term storage properties of Ni/MH battery

The charge retention and long-term storage properties of AB5-based Ni/MH batteries were studied by partial/complete replacements of Al- and Mn-contents by Ni in the AB5 alloys, separately. A high-temperature accelerated testing scheme (60°C and 60-days) was proven to be capable of predicting the status of batteries after long-term storages at room temperature (6-months and 293-days). Charge retention and impedance measured from the accelerated scheme can be correlated to the open-circuit voltage and impedance after long-term storage, respectively. While both Al and Mn were important to maintain good charge retention, Al, with its good oxidation resistance to slow down the oxidation/corrosion of the MH alloy, contributed to a lower internal impedance, Mn, on the other hand, slowed down the pulverization rate and reduced the irreversible capacity loss, however, contributed to a higher reversible capacity loss. The addition of Y2O3 in the positive electrode was found to raise the open-circuit voltage and reduce both reversible capacity loss and impedance increase during long period storage by slowing down the oxidation/corrosion of the MH alloy in the negative electrode.

In storage psychrophilic anaerobic digestion of swine slurry

Anaerobic digestion of manures induces deodorization and conserves nitrogen. Livestock producers could transform their long-term (250–300 day) manure storages into psychrophilic anaerobic digesters, thus greatly reducing the investment, operational and technical cost associated with the treatment. But, sufficient inoculation is required and the feeding regime differs from that of a fixed volume digester, as the fed manure volume to digester content ratio is ever decreasing over time and the retention time is as long as the storage period. The project was designed to establish, in the laboratory, the inoculation conditions and feeding regime leading to the efficient establishment and operation of anaerobic digestion in conventional storages. In the laboratory using the biochemical methane potential test (BMP), methane production was monitored from swine manure inoculated with one of the three inocula (cattle manure—B; municipal wastewater anaerobic sludge—R, and; food processing wastewater anaerobic sludge—C) at four ratios (0, 10, 30 and 50%). Also, six prototype digesters were used to simulate VSS digestion in conventional storages, under two feeding regimes (once every week and every 2 weeks) and using three inocula. With the BMP and for all three inocula, a ratio of 10% provided the fastest initiation and the highest methane production. Both R and C initiated methane production as of the 1st day because of their active bacterial population, while B, obtained from a facultative system, required 24 days. After 100 days, all three inocula had produced the same amount of methane, for the same inoculation ratio. In the prototype digesters, both R and C inocula produced methane as of the first day, while the B inoculum produced methane after day 45 and 78 days, for the 1/week and 1/2week feeding regime, respectively. For both feeding regimes and after 148 days, all three inocula produced the same cumulative amount of methane. Thus, 10% B can initiate anaerobic conditions in swine manure during storage, as long as the storage period exceeds 140 days and a 45 day initiation period at a temperature is 35 °C.

NON-ALLOYED Ge/Pd OHMIC CONTACT FOR GaAs MESFET'S

GaAs MESFET's with non-alloyed ohmic contacts have been achieved through a solid phase reaction of the Ge/Pd/GaAs(xtl) structure upon annealing at 325° C for 30 min. Different Au-based overlayers over Ge/Pd have been tested for device applications and compared with a conventional AuGeNi contact. The thermal stability of the contact resistivity has been evaluated through long-term storages at 300°C.