Buffer Tank Research Articles

Resilience evaluation of active and passive redundancy using carbon-hydrogen-oxygen symbiosis network – An integrated and post-design analysis

Carbon-hydrogen-oxygen symbiosis network, which is an eco-industrial park design method, along with atomic targeting provides a different avenue to approach effluents whereby effluents from industries could be gathered and redistributed to the respective interceptors to produce products. Resilience of an eco-industrial park is of particular interest due to the fluctuating economy whereby commitment of participants would be into question due to downturn in the economy. Resilience index provides a metric to evaluate the resilience of an eco-industrial park by assigning a value between 0 and 1. Resilience of an eco-industrial park could be improved by either having active redundancy such as extra process lines or oversizing the process lines. However, passive redundancy such as storage and buffer tanks also play a role in improving resilience of an eco-industrial park. This work aims to develop a method for resilience evaluation of a carbon-hydrogen-oxygen symbiosis network as well as comparing active and passive redundancy in resilience improvement of an eco-industrial park. Besides, the resilience metric is also incorporated into the carbon-hydrogen-oxygen symbiosis network model to compare the differences between post-design and integrated approach. The results obtained showed that while incorporation of both active and passive redundancy on all species would maximise the resilience index, partial combination of both could achieve a similar result. Besides, post-design and integrated approach would yield similar resilience index when interceptors of carbon-hydrogen-oxygen symbiosis network is limited. When more degrees of freedom are given to the number of interceptors, the results of post-design would not differ much. On the other hand, the results from integrated approach would select extra interceptors. Primarily, species which have not been compensated in the network would be selected to allow for redirection of flow when disruption occurs.

ЦЕЛЕСООБРАЗНОСТЬ ПРИМЕНЕНИЯ ПРЕДВАРИТЕЛЬНОГО ОЗОНИРОВАНИЯ ВЛАЖНОГО ЗЕРНА ПЕРЕД СУШКОЙ

When drying grain, ozone enters into a number of chemical reactions that contribute to an increase in the partial pressure inside the grain and a change in the temperature gradient, which accelerates vaporization and increases the moisture diffusion coefficient. Practical application of the ozone-air mixture as a drying agent has not been established due to difficulties with process safety, the lack of substantiated ozone treatment modes, and imperfect ozonizer designs. The feasibility of using the ozonation process during drying was determined based on experiments on changing grain moisture using the ozone-air mixture as a drying agent. It was proposed to modernize the existing grain drying complexes by retrofitting the buffer silos with an ozonation system. A method for drying grain material has been developed that consists of two sequentially performed operations: preliminary ozone treatment of wet grain and its subsequent drying in a serial grain dryer. Three experiments were conducted to determine the effect of preliminary ozonation on the moisture separation process when heating a grain heap. It was found that the use of preliminary ozone treatment of wet grain in a buffer tank before the grain dryer with an ozone concentration of 5, 7.5 and 15.3 mg/m3 made it possible to increase the relative drying rate by 1.51-1.84 times. Preliminary ozonation of wet grain is advisable because it not only reduces the costs of bringing the grain to a conditioned state in terms of moisture, but also has a positive effect on the quality of the dried material.

Simulation study on preventing explosive mixture formation in PEM electrolysers’ water recovery tanks

Investigations of safety issues related to the design and operation of high-pressure proton exchange membrane (PEM) water electrolysers have until now mainly focused on the electrolyser stack. The present study focuses on the risk of explosive mixture formation in the water recovery system, which is part of the balance of plant in water electrolysers. After a major electrolyser company experienced an unexpected detonation in their system, we analysed their process design as a base case: a low-pressure buffer tank where anodic and cathodic water is mixed with make-up deionised water poses a safety risk because an explosive gas mixture is likely to form there, resulting in severe accidents. Several retrofit options are explored using dynamic and steady-state simulation models: these options are then evaluated based on their effects on safety, general economics and operation of the plant, in addition to ease of retrofit. The results show that preventing the formation of explosive gas mixtures in the water recovery system is achievable in several ways, such as avoiding recycling cathodic water altogether, stripping it of hydrogen, flushing buffer tanks with nitrogen or oxygen, rearranging the balance of plant appropriately, or changing the control algorithms of the system.

Optimization of design and operation of a digestate treatment cascade for demand side management implementation

Sustainable chemical engineering through demand side management (DSM) and renewable feedstock integration e.g. in biorefineries are key to optimizing the use of fluctuating energy resources and minimizing environmental impact while conserving resources. This contribution presents the results of the economic evaluation of integrating DSM into biofuel biorefineries through a dynamic simulation approach. A previously developed decision support tool for DSM implementation was extended to describe the size of intermediate buffer tanks as a function of oversizing up- and downstream processes. Design optimization of the process cascade determined the oversizing that allows the optimal balance of operational cost reduction through flexibility and capital cost increase through oversizing. Scheduling optimization validated the results of the steady-state optimization and show that, by considering interactions between processes, buffer tank capacity can be reduced, while increasing DSM potential.

Reservation of the heat supply system with biofuel heat energy sources

The implementation of the reservation of the heat supply system to a populated area was analyzed. It is noted that increasing the reliability of heat supply to consumers is a fundamental task, especially given the current military situation in Ukraine. The solution to this difficulty is considered when reserving heat supply by constructing a backup source of thermal energy using alternative types of fuel. A combined thermal scheme for connecting a hot water heat generator using biofuel to the existing city heat supply system is proposed to increase its reliability and survivability, which ensures the efficiency and reliability of operation of the heat supply system during the heating and summer periods. It is shown the possibility of operating a solid fuel heat generator with its power significantly less than the total heat load of the city's heating supply in several operating modes: during the heating period - for heating the return coolant at the inlet to the existing gas boiler house; in the summer period - for the needs of hot water supply in full; in the event of an emergency shutdown of a gas boiler house in winter - to maintain the viability of the heat supply system. The results of a calculation analysis of the operation of a 5,0 MW biofuel heat generator under different operating modes are presented. Heating the return coolant by 4...5 °C in winter, in addition to saving natural gas, prevents low-temperature corrosion of existing gas boilers. In the event of an emergency lack of natural gas supply, the combustion of wood chips ensures the production of thermal energy at the level of thermal losses of the heating network while maintaining the coolant temperature at least 3 °C at the calculated external air temperature. Thanks to the accumulation of thermal energy at night in the summer period in the volume of heating network pipes as a buffer tank, compensation for peak hot water consumption is provided with the available power of the solid fuel boiler house equal to the average load of the hot water supply system. When implementing a project to back up the heat supply system in Lutsk using a combined thermal scheme for connecting a solid fuel boiler house, an increase in the reliability and viability of the system and natural gas savings of 40,5% during a year of operation were achieved

Definition of a PVT coupled water source heat pump system through optimization of individual components

Exploiting renewable resources considering their discontinuity compared to building needs, necessitates energy system designs that simultaneously maximize generation and storage performance in different seasons. This article presents the optimization of RESHeat European project, concerning a high-performance system which combines water-source heat pump, cooled photovoltaic panels and thermal storage. The research regards the Italian demo site, near Rome, to define a solution for Mediterranean regions which alongside the requirement for heating have notable need for summer cooling. The targets are system's efficiency, with a minimum sCOP of 5, and a minimum 70 % coverage from renewable sources focusing ambient temperature management.A dynamic model of plant and building was used for parametric analysis, which covered separately heating and cooling modes, involving significant parameters: operating temperatures of the heat pump, number of strings comprising the photovoltaic array, volume of the buffer tank connecting PVTs and WSHP and setpoint temperature of a cooler added for tank temperature control in cooling. 184 alternative configurations were evaluated by Multi-Criteria Decision Making (MCDM) method based on energy, economic and logistic criteria, and weighted by five indices. The optimal system includes 15 PVT panels strings for 25 kWp, a 3 m³ storage tank and cooling setpoint temperature of 25 °C.

Research on Multi-Objective Optimization of Low Pulsation Unloading Damping Groove of Axial Piston Pump

The high- and low-pressure switching of the axial piston pump is realized by the structure of the valve plate, and the buffer-groove structure on the valve plate is very important to reduce the pressure shock and flow fluctuation. In order to optimize the structural parameters of the buffer tank of the piston pump, the influence of the triangular-groove structure on the outlet pressure–flow characteristics was analyzed, and the low-pulsation buffer-groove structure was designed. First, the relationship between the structure of the triangular buffer tank and the output pressure and flow characteristics of the pump was analyzed theoretically. The Computational Fluid Dynamics (CFD) method was used to calculate the pressure and flow characteristics of the whole pump flow field of the triangular-groove structure, and the influence of the buffer-groove structure parameters on the outlet flow pulsation characteristics was studied. The multi-objective optimization algorithm was used to optimize the structure parameters of the buffer tank, and the optimized structure significantly reduced the outlet pressure–flow pulsation of the piston pump. The results show that, after optimization, the width angle of the front and rear triangular groove is 82.3°, the depth angle is 12.7°, the optimized pressure pulsation rate is 0.3%, and the optimized flow pulsation rate is 13.7%.

Hybrid Advanced Control Strategy for Post-Combustion Carbon Capture Plant by Integrating PI and Model-Based Approaches

Even though the energy penalties and solvent regeneration costs associated with amine-based absorption/stripping systems are important challenges, this technology remains highly recommended for post-combustion decarbonization systems given its proven capture efficacy and technical maturity. This study introduces a novel centralized and decentralized hybrid control strategy for the post-combustion carbon capture plant, aimed at mitigating main disturbances and sustaining high system performance. The strategy is rooted in a comprehensive mathematical model encompassing absorption and desorption columns, heat exchangers and a buffer tank, ensuring smooth operation and energy efficiency. The buffer tank is equipped with three control loops to finely regulate absorber inlet solvent solution parameters, preventing disturbance recirculation from the desorber. Additionally, a model-based controller, utilizing the model predictive control (MPC) algorithm, maintains a carbon capture yield of 90% and stabilizes the reboiler liquid temperature at 394.5 K by manipulating the influent flue gas to the lean solvent flowrates ratio and the heat duty of the reboiler. The hybrid MPC approach reveals efficiency in simultaneously managing targeted variables and handling complex input–output interactions. It consistently maintains the controlled variables at desired setpoints despite CO2 flue gas flow disturbances, achieving reduced settling time and low overshoot results. The hybrid control strategy, benefitting from the constraint handling ability of MPC, succeeds in keeping the carbon capture yield above the preset minimum value of 86% at all times, while the energy performance index remains below the favorable value of 3.1 MJ/kgCO2.

Optimizing the production process of biscuit industry as an approach to strengthening the local agricultural sector which reduce vulnerability of the global food crisis case study: analysis of waste in coconut biscuit industry with the DMAIC method

Abstract The local biscuit industry as a potential partner in the agricultural sector continues to grow rapidly. The development of local industries, including the coconut biscuit industry, must be continuouslyoptimized as an approach to empowering local agricultural sector that indirectly play a role in reduce vulnerability of the global food crisis. This makes the industry continue to try to find and adopt efficient and effective ways to increase product value and expand market share, one of the ways is the application of lean manufacturing. In this article, a case study is used in the coconut biscuit industry using the DMAIC analysis method and several tools such as VALSAT, fishbone diagrams and FMEA. Based on the analysis conducted, it is known that in the coconut industry there are several wastes such as unnecessary motion, defects and rework, and waiting with non-value added (NVA) activities for 784s. Therefore, further analysis is carried out regarding the proposed improvements that might be implemented. Some of the suggestions for improvement that can be given are the preparation of a buffer tank that is integrated with aload cell and transfer using a piping system, determine standardization of temperature and treatment of ovens as well as stipulation of work instructions and briefings during the initial process of the production line, analysis and evaluation of capacity, line layout, and lifetime on sugar water silo pumps and adjustments size and maintenance of dough tubs so as to reduce waste and NVA in the production process area.

Experimental study of effects of buffer tank volume on pressure pulsation in valved linear compressor's pipe system at different frequencies

Experimental study of effects of buffer tank volume on pressure pulsation in valved linear compressor's pipe system at different frequencies

Optimal control of a heat pump-based energy system for space heating and hot water provision in buildings: Results from a field test

This paper presents and discusses results from a field test that uses model predictive control (MPC) to optimise the operation of a multi-source heat pump-based energy system for space heating and hot water provision in a building. The objective of the optimisation is to minimise the electricity consumption of the heat pump using flexibility from the heat sources, the space heating and domestic hot water tanks while ensuring end-user comfort and system constraints. The field test was performed in the context of the RES4BUILD project. The integrated system consists of photovoltaic-thermal (PVT) collectors, an advanced vapour-compression multi-source heat pump and water buffer tanks for space heating and hot water needs. The heat pump utilises a solar buffer, a borehole thermal energy storage (BTES) and air as heat sources. The solar buffer is supplied with heat from the PVT collectors. The optimal operation of the system is obtained by monitoring and controlling the interactions between the different system components using MPC, taking into account the weather and heat load forecasts. Results have shown that MPC has a potential and added value for the optimal operation of multi-source heat pumps in real-life while considering system constraints and user behaviour to ensure thermal comfort. However, significant effort and expert knowledge are needed to develop the sufficiently accurate system models required by this control approach. The outcomes and conclusions of this work are therefore a basis for further development of such control approaches to improve their replicability and feasibility on a large scale, considering the diverse nature of energy system components in buildings.

Enhancing process state monitoring in energy storage systems: A robust design synthesis with physics-informed generalized observer

Energy storage systems (ESSs) are crucial for managing renewable energy fluctuations. Knowing ESSs’ states is vital for thermal management. This paper presents a robust design synthesis approach, leveraging a physics-informed generalized observer (GO), for enhancing the process state monitoring in ESSs. The proposed GO takes advantage of the inherent characteristics of ESSs as interconnected subsystems with distinct physical significance. By utilizing measured inputs and outputs, the GO accurately estimates the unmeasurable and unknown process states. GO employs a physics-informed model and a tracking feedback correction mechanism for accurate state estimation. It offers high accuracy, robustness, and insensitivity to measurement noise. To validate the effectiveness of the proposed approach, two case studies are conducted on ESSs. The first involves monitoring the core temperature of lithium batteries, and the second involves an experimental study on monitoring the inner chamber temperature of heat buffer tanks. Experimental results demonstrate approximately 10% improvement compared to conventional methods. GO provides a simple design method, clear physical interpretation, and strong interpretability. Overall, GO is an effective and versatile observer for process monitoring with significant advantages and potential for various applications.

The potential of decentral heat pumps as flexibility option for decarbonised energy systems

Decarbonising the energy system requires high shares of variable renewable generation and sector coupling like power to heat. In addition to heat supply, heat pumps can be used in future energy systems to provide flexibility to the electricity system by using the thermal storage potential of the building stock and buffer tanks to shift electricity demand to hours of high renewable electricity production. Bridging the gap between two methodological approaches, we coupled a detailed building technology operation model and the open-source energy system model Balmorel to evaluate the flexibility potential that decentral heat pumps can provide to the electricity system. Austria in the year 2030 serves as an example of a 100% renewable-based electricity system (at an annual national balance). Results show that system benefits from heat pump flexibility are relatively limited in extent and concentrated on short-term flexibility. Flexible heat pumps reduce system cost, CO2 emissions, and photovoltaics and wind curtailment in all scenarios. The amount of electricity shifted in the assessed standard flexibility scenario is 194 GWhel and accounts for about 20% of the available flexible heat pump electricity demand. A comparison of different modelling approaches and a deterministic sensitivity analysis of key input parameters complement the modelling. The most important input parameters impacting heat pump flexibility are the flexible capacity (determined by installed capacity and share of control), shifting time limitations, and cost assumptions for the flexibility provided. Heat pump flexibility contributes more to increasing low residual loads (up to 22% in the assessed scenarios) than decreasing residual load peaks. Wind power integration benefits more from heat pump flexibility than photovoltaics because of the temporal correlation between heat demand and wind generation.

Experimental research of an integrated scavenging pump coupled with a buffer tank for a free-piston engine

Experimental research of an integrated scavenging pump coupled with a buffer tank for a free-piston engine

Optimal supply air temperature with respect to data center operational stability and energy efficiency in a row-based cooling system under fault conditions

This is the first study of data center row-based cooling strategies under fault conditions. An optimal supply air temperature (SAT) for row-based cooling is proposed to ensure energy efficiency and operational reliability. The appropriate SAT for emergency operation is determined by evaluating how long the allowable IT equipment's inlet air temperature (IAT) can be maintained by only running the fan of the computer room air handling (CRAH) unit when the chilled water supply is interrupted. Three cases with SAT values of 20 °C, 22 °C, and 24 °C are evaluated in a numerical analysis, and the maintenance potential of the IAT is assessed by analyzing 600 s of transients from the time of cooling failure. In all cases, the IAT is almost the same as the SAT under normal cooling, but in cooling failure, the time to reach downtime beyond the allowable IAT is 246s in Case 1, 133s in Case 2, and 85s in Case 3. Response strategies to cooling failure include increasing uninterruptible power supply (UPS) capacity and applying a thermal buffer tank. The study concludes that it is reasonable to set the SAT of row-based cooling to 22 °C or lower and to install a thermal buffer tank in the chilled water system for effective downtime delay. These results are based on a rack power density of 7 kW/rack.

Modeling and simulation of dynamic characteristics of a green ammonia synthesis system

Green ammonia production system driven by renewable electricity will be under frequent dynamic operation due to the fluctuation of renewable energy. The nonlinear dynamic model of a green ammonia synthesis system is developed and the dynamic responses of PEM (proton exchange membrane) electrolysis subsystem, PSA (Pressure swing adsorption) subsystem and ammonia synthesis subsystem during the start-up process and under the fluctuation of renewable electrical current are analyzed. The start-up dynamic results show that the hydrogen production rate of PEM electrolysis system is positively correlated to the current. The nitrogen output of PSA system is affected by the adsorption time, adsorption pressure, bed length, and air velocity. A start-up period of 300 min from the warmed-up state to the design state can maintain the temperature rise rate of the ammonia synthesis reactor at approximately 40 K/h. The dynamic results under step fluctuations of electrical current show that the PEM electrolysis subsystem and the PSA subsystem response fast compared to the ammonia synthesis reactor and buffer tanks. Using large buffer tanks to smooth the fluctuation allows the system to slide with the variation of renewable current to some extent, resulting in a higher outlet ammonia fraction when the current increases. Different volume ratios of the hydrogen tank to the nitrogen tank volume can lead to different variations of the hydrogen/nitrogen ratio. PID controllers can effectively maintain the bed temperatures, hydrogen/nitrogen ratio, and pressure of the ammonia synthesis reactor at their set points despite fluctuations in renewable electrical current. Buffer tanks are necessary to compensate for the imbalance between the flow rate fluctuation caused by current change and the flow rate regulation caused by PID controllers.

Applying a 2 kW Polymer Membrane Fuel-Cell Stack to Building Hybrid Power Sources for Unmanned Ground Vehicles

The novel constructions of hybrid energy sources using polymer electrolyte fuel cells (PEMFCs), and supercapacitors are developed. Studies on the energy demand and peak electrical power of unmanned ground vehicles (UGVs) weighing up to 100 kg were conducted under various conditions. It was found that the average electrical power required does not exceed ~2 kW under all conditions studied. However, under the dynamic electrical load of the electric drive of mobile robots, the short peak power exceeded 2 kW, and the highest current load was in the range of 80–90 A. The electrical performance of a family of PEMFC stacks built in open-cathode mode was determined. A hydrogen-usage control strategy for power generation, cleaning processes, and humidification was analysed. The integration of a PEMFC stack with a bank of supercapacitors makes it possible to mitigate the voltage dips. These occur periodically at short time intervals as a result of short-circuit operation. In the second construction, the recovery of electrical energy dissipated by a short-circuit unit (SCU) was also demonstrated in the integrated PEMFC stack and supercapacitor bank system. The concept of an energy-efficient, mobile, and environmentally friendly hydrogen charging unit has been proposed. It comprises (i) a hydrogen anion exchange membrane electrolyser, (ii) a photovoltaic installation, (iii) a battery storage, (iv) a hydrogen buffer storage in a buffer tank, (v) a hydrogen compression unit, and (vi) composite tanks.

Flexibility implications of optimal PV design: building vs. community scale

The Swiss Energy Strategy 2050 aims for a significant increase in renewable energy generation, with photovoltaic (PV) energy having the largest share. Such development challenges the balance between electricity supply and demand, which can be partly mitigated through optimized PV integration together with energy storage systems. This study investigates the optimal placement of rooftop and façade PV for a small energy community considering investment and operational costs, embodied and operational emissions, and financial and environmental benefits of excess on-site electricity production, as well as batteries and different heating system options. Additionally, a methodology is developed to quantify energy flexibility needs at both the building and community scale. A case study neighborhood, comprising three single-family and two multi-family homes is optimized across different scenarios. Results show that when individual self-consumption is considered, installing an air-to-water heat pump system with a heating buffer tank allows for smaller PV systems with better grid interaction conditions. When collective self-consumption is considered, an overall reduction in PV system size is observed, contributing to reduced energy flexibility needs by effectively lowering peak feed-in power and improving the match between on-site PV production and demand.

Design and Long-Term Performance of a Pilot Wastewater Heat Recovery System in a Commercial Kitchen in the Tourism Sector

This paper assesses the performance of waste heat recovery from commercial kitchen wastewater in practice. A pilot study of heat recovery from the kitchen at Penrhyn Castle, a tourist attraction in North Wales (UK), is outlined. The pilot heat recovery site was designed and installed, comprising a heat exchanger, recirculation pumps, buffer tank and an extensive temperature/flow monitoring system for performance monitoring of the waste heat recovery system. Continuous monitoring was conducted for a period of 8 months, covering the 2022 tourist season. The recovered heat from the kitchen wastewater preheats the incoming cold freshwater supply and consequently reduces the amount of energy consumed for subsequent water heating. Retrofitting the pilot heat recovery system to the kitchen drains resulted in a heat saving of 240 kWh per month on average, a reduction of 928.8 kg CO2e per year, and a payback period for the investment costs of approximately two years, depending on the cost of energy supply. The presented results illustrate the potential of this form of renewable heat in reducing the carbon footprint of water heating activities in buildings and the hospitality sector.

Integrated continuous downstream process of monoclonal antibody developed by converting the batch platform process based on the process characterization.

A continuous downstream process of monoclonal antibody was developed based on the process characterization. Periodic-counter current chromatography (PCCC) with two protein A columns was used for the capture step. For low pH virus inactivation (VI), a batch reactor was employed, which can work as a surge (buffer) tank. Flow-through chromatography (FTC) with two connected columns of different separation modes (anion-mixed mode and cation exchange) was designed as a polish step. After 24 h PCCC run, the collected pool was processed for VI. After adjusting pH and electric conductivity, the solution was fed to the two connected FTC columns for 24 h. Virus filter was also connected to the exit of the connected-column. PCCC and FTC were run in parallel. Six runs of different feed rates (0.5-10 L/day) and feed concentrations (1-3.2 g/L) were performed with protein A columns of 1-5 mL and FTC columns of 3-10 mL. The largest run (feed rate 10 L/day, feed concentration 2 g/L) was carried out at a GMP facility with 15 mL protein A columns and 100 mL FTC columns. Good recovery and purity values were obtained for all runs. The process was found to be flexible and stable for feed fluctuations. Only three surge or pool tanks were needed in addition to the final product pool tank.