Intermediate Storage Tanks Research Articles

Performance evaluation of combined passive/active thermal charge/discharge latent heat tank with stabilized-solid-liquid storage material for intermediate thermal storage system

This study proposes a new model operation for an intermediate thermal storage (ITS) tank for solar water heater system. It combines passive-charge active-discharge (PCAD) in a single storage tank, potentially reducing the number of components of the system and improving the net energy balance. The charge process is done by heating the storage material using an electric heater, which is also suitable for direct photovoltaic heating. The temperature profile of stabilized storage material in this stage shows a close plateau line in the solid-liquid transition, indicating a steady phase transition takes place. It minimizes the temperature deviation between the solid/liquid region, which is advantageous for determining the operation protocol. For the discharge process, the working fluid circulates from the mantle side and continues to the inner side of the tank, resulting in two-consecutive heating. It allows the fluid to harness the stored heat up to 72.8%. It is also achieved by the stabilized storage material, which has a better solidification mechanism. Thus, the proposed PCAD tank is able to meet the criteria of an ITS tank, which requires energy exchange during the charge/discharge stage. The finding demonstrates that a simplification of the ITS tank is achievable. The implication of the finding can be used as a fundamental basis for developing new solar water heating systems, including for direct charge operation using photovoltaic-heating systems where the heat is taken as alternative energy storage instead of electricity.

A method for calculating the volume of an intermediate storage tank in storm sewer systems for management and treatment

The purpose of the article is to clarify and supplement the methodology given in the current regulatory and methodological framework for the purpose of engineering calculation of the storm flow management scheme for sewage treatment plants. The flow control scheme, including an intermediate tank, a pumping station and a separation chamber, is analyzed by mathematical modeling using a computer algebra system. Changes are proposed in the calculation formula for determining the volume of storage tank for the scheme of emptying the tank by pumps, taking into account all types of separation chambers. The dependence is established and graphs are shown showing the effect on the volume of the tank of the coefficient, which takes into account the variability of the flow diverted by the separation chamber into the collector.

Impact of management strategy on green methane production from wind energy

Mitigating the effects of global warming by reducing greenhouse gas emissions requires the adoption of sustainable practices and the promotion of renewable energies. However, in an energy scenario strongly dominated by intermittent energy sources, storage systems are becoming increasingly important. In this context, the conversion of renewable energy peaks into green hydrogen can be considered an interesting possibility. Furthermore, the use of power-to-gas systems solves, at least in a transition phase, the problems associated with the lack of infrastructure dedicated to hydrogen. In this study, a power-to-gas system producing synthetic methane from wind energy was modelled. Three management strategies were implemented and compared to assess the flexibility and versatility of the system. Results showed the importance of using an intermediate hydrogen storage tank to reduce the amount of surplus hydrogen. However, the choice of a management strategy depends on the purpose for which the power-to-methane system is designed.

GHG Emissions from CO2 Ship Transportation Chain

In a CCS chain, the CO2 is first captured and then transported to a suitable permanent storage site. The transport element could either be by pipeline, ship, or a combination of both, and the choice of transportation strategy will depend on several factors. Such as location of emission source, location of suitable storage sites and the volume of CO2 to be transported. In the ongoing Norwegian Longship project, the transport concept under planning is shipping of CO2 from one or two emission sites to an import hub located at Kollsnes, Norway. From Kollsnes, the CO2 is to be transported to an offshore aquifer through a pipeline. The scope of the ongoing project ''CO2LOS II'' (CO2 Logistics by Ship Phase II) is to reduce the cost of CO2 ship transportation by utilizing new technology and investigate optimization possibilities in the logistic chain. The project focuses on all activities between capture and permanent storage. Within this setting, this article encompasses a qualitative/quantitative assessment of greenhouse gas (GHG) emissions from the transport chain. This associated GHG emission is expected to be significantly lower than the quantities of CO2 stored, still it is worthwhile to estimate. The investigation has shown that it is the electricity consumption of the CO2 liquefaction plant that is the major contributor of GHG emissions from the transport chain followed by the fuel consumption of the ship, while the CO2 boil-off from intermediate storage tanks and the ship's cargo tanks is not a major contributor to the emissions in the transport chain. Therefore, the effort should be to reduce the fuel or power consumption or to change the fuel type to a lower carbon intensive fuel or power mix.

Continuous tannin extraction by use of screw reactor

A pilot-size screw reactor (extraction unit) was used for tannin extraction of spruce. Yield of the same magnitude or better was obtained when comparing a screw reactor with batch reactors. A longer presoaking time in water seemed to be better than a short one for obtaining higher yield. A higher yield is obtained with lower dry-water ratio, which suggests that the internal diffusion in bark does not determine mass transfer as much as is the case without presoaking of bark. The higher dry-water ratio decreased the yield. The prior soaking of the bark also minimized the mechanical reactor feeding problems (clogging). The benefits of a screw reactor likely are that run time changes for different process conditions are flexible; it simplifies design and construction of an industrial unit for tannin production; and it saves space because of the need for fewer and smaller intermediate storage tanks.

A simple strategy to maximize water-reuse in multistage, multiproduct batch processes

Many countries are currently facing a severe water crisis. Further, in various industrial sectors, small and medium enterprises operate multistage, multiproduct batch processes that require large quantities of water. This work is motivated by the inability of such enterprises to deploy complex water-reuse strategies since their plants are neither well instrumented nor automated. The design and operational strategies of water reuse networks for multistage, multiproduct batch processes is inherently challenging due to the underlying discontinuities and other nonlinearities. In this paper, we propose an easy-to-implement water-reuse strategy that utilizes intermediate storage tanks with finite capacities. The strategy relies on a simple heuristic that maps discharge from specific stages to be stored in corresponding tanks. A fallback sequence is also provided in case the tank cannot accommodate the entire discharge volume. An analogous scheme for reusing water from the tanks in appropriate process stages is also proposed. In this paper, we demonstrate using a textile industry case study that this simple reuse strategy can result in significant water savings. For this, we develop an optimal production schedule using a genetic algorithm that simultaneously minimizes production makespan and the freshwater consumption. Our results show that for a set of 4 products with up to 14 production stages, 76% of the freshwater could be reduced if 13 tanks can be deployed. Even with 2 tanks, the proposed strategy results a 42% reduction of the freshwater requirements.

Property Integration of Water Network for Batch Processes in Multiple Production Lines

Batch operation is the main production pattern for high value-added chemicals, and the wastewater from different batch production lines features differently in properties, such as contaminant concentrations, toxicity, pH, and chemical oxygen demand. Less attention has been drawn on the batch water network design with water property considered. To address this issue, this work develops a superstructure-based optimization approach to incorporate property integration within the synthesis of batch water network. Multiple production lines are considered in the study, so in addition to the water re-using system inside each production line, the re-using across lines and the central property treatment system are included by involving intermediate storage tanks as hubs for in-line, inter-line water allocation and treatment. The property treatment system is constructed by a list of property interceptors, which operate in semi-continuous manner with optimized treating performance in different time intervals. To obtain the desired network structure, a Mixed Integer Nonlinear Programming (MINLP) model is formulated, and the operation schedule of interceptors and storage tanks are optimized as well. Finally, a multi-property case is elaborated to validate the proposed method. By considering the potential interactions among batch production lines, a 22.12 % drop in Total Annual Cost (TAC) is achieved in the case study, demonstrating the effectiveness of the method.

New textile-based hybrid photovoltaic/thermal (PV/T) system

This paper introduces a new textile-based hybrid PV/T system utilizing a spacer fabric treated with phase change material (PCM). The PCM absorbs excess heat from the PV modules, which keeps the modules in their optimal temperature range so that their power output is enhanced. The thermal energy stored in the PCM is then used for hot water generation. Cold water, which is pumped through thin capillaries integrated into the spacer fabric, absorbs the heat stored in the PCM and is heated up. The warm water can be used immediately or stored in an intermediate storage tank. Comparing the proposed textile-based hybrid PV/T system to conventional hybrid PV/T systems, the proposed system is less expensive and provides a higher overall efficiency. The textile-based collector is lightweight, thin and flexible.

Production costs for synthetic methane in 2030 and 2050 of an optimized Power-to-Gas plant with intermediate hydrogen storage

The publication gives an overview of the production costs of synthetic methane in a Power-to-Gas process. The production costs depend in particularly on the electricity price and the full load hours of the plant sub-systems electrolysis and methanation. The full-load hours of electrolysis are given by the electricity supply concept. In order to increase the full-load hours of methanation, the size of the intermediate hydrogen storage tank and the size of the methanation are optimised on the basis of the availability of hydrogen. The calculation of the production costs for synthetic methane are done with economics for 2030 and 2050 and the expenditures are calculated for one year of operation. The sources of volume of purchased electricity are the short-term market, long-term contracts, direct-coupled renewable energy sources or seasonal use of surpluses. Gas sales are either traded on the short-term market or guaranteed by long-term contracts. The calculations show, that an intermediate storage tank for hydrogen, adjustment of the methanation size and operating electrolysis and methanation separately, increase the workload of the sub-system methanation. The gas production costs can be significantly reduced. With the future expected development of capital expenditures, operational expenditure, electricity prices, gas costs and efficiencies, an economic production of synthetic natural gas for the years 2030, especially for 2050, is feasible. The results show that Power-to-Gas is an option for long-term, large-scale seasonal storage of renewable energy. Especially the cases with high operating hours for the sub-system methanation and low electricity prices show gas production costs below the expected market prices for synthetic gas and biogas.

Optimal Design and Operation of Buffer Tanks Under Stochastic Conditions

Abstract Safety regulations demand the elimination of random mistakes and the reliable operation of production units. However, the control and maintenance of batch and semi-continuous processes haalways been difficult. In this paper, a way of preventing malfunctions in batch and semi-continuous processes is presented by using appropriately designed buffer tanks. A stochastic model was investigated in which batch and continuous subsystems were linked by an intermediate storage tank. The main concern was the reliability of the system. Reliable operation was defined as neither the exhaustion of raw materials nor the excessive accumulation of them. The counting processes that describe the random batch-input and random batch-output processes are supposed to be independent homogeneous Poisson processes with different rates. By introducing a function that describes the material in storage, reliable operation is defined as when this function satisfies two inequalities for a time interval of any duration. By applying probabilistic methods, an integral equation is set up for the the reliability. Nevertheless, its analytical solution cannot be determined, hence the values according to a Monte Carlo simulation are approximated. By applying this method, a link could be identified between the necessary initial buffer and tank capacities that belong to a reliability level. Economic investigations were conducted to help determine the optimal initial buffer and tank capacities that satisfy the appointed reliability level.

Global Optimization Algorithm for Large-Scale Refinery Planning Models with Bilinear Terms

We propose a global optimization algorithm for mixed-integer nonlinear programming (MINLP) problems arising from oil refinery planning. It relies on tight mixed-integer linear programming (MILP) relaxations that discretize the bilinear terms dynamically using either piecewise McCormick (PMCR) or normalized multiparametric disaggregation (NMDT). Tight relaxations help finding a feasible solution of the original problem via a local nonlinear solver, with the novelty being the generation of multiple starting points from CPLEX’s solution pool and the parallel execution. We show that optimality-based bound tightening (OBBT) is essential for large-scale problems, even though it is computationally expensive. To reduce execution times, OBBT is implemented in parallel. The results for a refinery case study, featuring units with alternative operating modes, intermediate storage tanks, and single- and multiple-period supply and demand scenarios, show that the algorithm’s performance is comparable to commercial solve...

Variación espacial de la composición de 222Rn en los acuíferos Barva y Colima Superior, Costa Rica

MEN: El 222Rn es un trazador natural que permite determinar la conectividad entre las aguas subterráneas y las superficiales. El estudio presenta el primer análisis espacial de 222Rn en aguas subterráneas, superficiales y agua potable de la red de abastecimiento en los acuíferos Barva y Colima Superior en el Valle Central de Costa Rica. Se analizó la composición de 222Rn, δ18O y otras variables físico-químicas in situ en un total de 40 sitios de muestreo. En general, las nacientes de la zona norte presentaron una composición homogénea de 222Rn con una concentración promedio de 21,3 Bq/L. La concentración de 222Rn en los pozos varió entre 2,0 Bq/L y 50,5 Bq/L. Las altas concentraciones de 222Rn en algunos pozos pueden atribuirse a la desgasificación profunda a través de los fallamientos locales. En la red de abastecimiento de agua potable, la concentración de 222Rn varió entre 4,7 Bq/L y 30,8 Bq/L. Los valores encontrados en la red de abastecimiento, superiores al límite sugerido por la Agencia de Protección Ambiental de los Estados Unidos (11,1 Bq/L) para agua de consumo humano, pueden atribuirse al corto tiempo de residencia del agua de extracción subterránea en la red de abastecimiento. La utilización de tanques de almacenamiento o captación permitiría aumentar el tiempo de residencia del agua antes de ingresar a la red de consumo, facilitando la pérdida de 222Rn hacia la atmósfera o por decaimiento radioactivo. Asimismo, un análisis espacial es requerido a escala nacional, especialmente, en áreas de fallas activas o actividad volcánica.

Multistage Production Planning in the Dairy Industry: A Mixed-Integer Programming Approach

This paper addresses a production planning problem in a multistage production system consisting of continuous processing resources separated by finite-capacity storage tanks, stimulated by a particular case study in the dairy industry. The problem is formulated as a mixed-integer linear programming (MILP) model that incorporates several distinguishing characteristics of dairy production, such as multistage bulk production, shelf-life requirements, intermediate storage, setups, resource speeds, limitations on minimum and maximum lot sizes, and the conservation of flow among various tanks. The objective is to maximize the total profit while determining the quantity of intermediate products and SKUs processed on various resources, the assignment of products to various resources and intermediate storage tanks, the quantity of each SKU sold, lost sales of each SKU, and waiting times. The determinations often reveal production bottlenecks. The efficiency of the proposed model is illustrated through its applicat...

Long-term turnaround planning for integrated chemical sites

An integrated chemical site involves a complex network of chemical plants. Typically, these plants interact closely, are dependent on each other for raw materials and demand for their products, and have the provision of intermediate storage tanks to help manage inventory at strategic points in the network. Disruptions in the operation of these plants can drastically affect flow of material in the site network. As a result, the choice of sequence and timing of planned periodic turnarounds, which are major disruptions, is important in order to minimize effects on profits and production. We investigate a discrete-time mixed-integer linear programming (MILP) model to perform turnaround optimization. The objective is to recommend potential schedules in order to minimize losses while satisfying network, resource, turnaround, demand, financial and other practical constraints. We propose general formulations to tackle this problem and study an industrial-size site network under various scenarios over a long-term horizon.

Nonlinear Autoregressive Exogenous modeling of a large anaerobic digester producing biogas from cattle waste

In waste-to-energy plants, there is every likelihood of variations in the quantity and characteristics of the feed. Although intermediate storage tanks are used, but many times these are of inadequate capacity to dampen the variations. In such situations an anaerobic digester treating waste slurry operates under dynamic conditions. In this work a special type of dynamic Artificial Neural Network model, called Nonlinear Autoregressive Exogenous model, is used to model the dynamics of anaerobic digesters by using about one year data collected on the operating digesters. The developed model consists of two hidden layers each having 10 neurons, and uses 18days delay. There are five neurons in input layer and one neuron in output layer for a day. Model predictions of biogas production rate are close to plant performance within ±8% deviation.

Injection of CO2 at Ambient Temperature Conditions – Pressure and Temperature Results of the “cold injection” Experiment at the Ketzin Pilot Site

Abstract From June 2008 to August 2013, slightly more than 67 kt of CO2 were injected at the Ketzin pilot site (Brandenburg, Germany). The CO2 reservoir is a saline aquifer at a depth of 630 – 650 m with initial pressure and temperature conditions of about 33 °C/62 bar. These reservoir conditions are near the critical point of pure CO2 (31.0 °C/73.8 bar) and the CO2 liquid-vapour equilibrium. In order to avoid phase transitions and near-critical phenomena throughout the injection process the CO2, which was delivered by road tankers and stored in intermediate storage tanks on site at ∼ -18 °C/21 bar, was pre-conditioned at site and pressurised to ∼ 65 bar and heated to ∼ 40 °C during regular operation. This injection process design worked exceptionally well. However, such a pre-conditioning and heating of the injected CO2 to elevated temperature is unrealistic for an industrial sized CO2 storage setting as the energy need is high and costly and the CO2 will be delivered by pipeline already at ambient temperature. To study the effects of lower pre-conditioning temperature and effects of potential two-phase flow on the injection process, a “cold injection” experiment was carried out between March and July 2013. The injection wellhead temperature was decreased stepwise from 40 °C down to 10 °C. Below 20 °C two-phase flow developed in the surface installations and in the injection well down to the reservoir and a mixture of gaseous and liquid CO2 has been injected. This two-phase CO2 injection ran smoothly for eight weeks without any operational issues.

Thermoeconomic design optimization of a thermo-electric energy storage system based on transcritical CO2 cycles

The conceptual design of a thermo-electric energy storage (TEES) system for large scale electricity storage is discussed in this work by showing the results of the thermoeconomic optimization of three different system configurations that were identified in previous works. The system is based on transcritical CO2 cycles, water storage and salt-water ice storage and is designed for a capacity of 2 h discharge and equal charge and discharge power of 50 MW. A two-step optimization procedure is used. The system intensive design parameters are optimized at the master level through a genetic algorithm. The optimal cycle mass flow rates are calculated in a nested linear programming step where the heat integration between the cycles is optimized subject to the heat transfer feasibility imposed through Pinch Analysis cascade calculations. The synthesis of the heat exchanger network and of the storage tank systems was solved through a set of heuristic rules. Equipment purchasing costs were estimated by means of cost functions that were built upon vendors quotations. The results are discussed by showing the Pareto fronts of the three optimization cases and the trends of the decision variables along each optimal front. Nine solutions are discussed in more detail by showing the values of the design parameters and the process flow diagrams including storage and heat exchanger layouts. Design guidelines are then formulated which can be used in future works for detail plant design. The topological features that are found to maximize the system performance at the minimum costs are: superheating before the CO2 heat pump, two independent systems of hot water storage tanks above and below the ambient temperature, and air cooling at the heat pump side. The design parameters that affect significantly the costs and performances are the cycle pressures. These are in fact directly associated with temperature differences both at the cold and hot storage sides which should be carefully optimized to obtain the best trade-off between exergy losses and costs for heat exchangers. Due to the change in specific heat of the supercritical CO2 along the temperature range of hot water storage, a system of multiple storage tanks was used. Intermediate storage tanks help reduce significantly the temperature differences at the hot storage side and therefore their number represent another critical design parameter that must be optimized to achieve the best trade-off between costs and performances.

Injection operation and operational pressure–temperature monitoring at the CO2 storage pilot site Ketzin, Germany—Design, results, recommendations

The Ketzin pilot site for geological storage of CO2 in the German Federal State of Brandenburg about 25km west of Berlin is the only German CO2 storage site and has been the first European pilot site for on-shore storage of CO2 in saline aquifers. Continuous injection of CO2 started on June 30th, 2008, and a total of 61,396t of CO2 have been injected by September 2012. The injected CO2 was predominantly food-grade with a purity>99.9%, only from May to June 2011, 1515tCO2 from the Schwarze Pumpe oxyfuel pilot plant with a purity of >99.7% have been injected. The injection is accompanied by a comprehensive operational monitoring program. The program includes continuous measurements of flow rate, fill levels of intermediate storage tanks 1 and 2, outlet pressure and temperature for the injection plant, wellhead pressures (WHP) and casing pressures 1 and 2 for all wells, bottom hole pressure (BHP), bottom hole temperature (BHT) and distributed temperature sensing (DTS) along the injection tubing for the injection well Ktzi 201, BHP for the two observation wells Ktzi 202 (from March 2010 to October 2011) and Ktzi 200 (since October 2011), and above-zone pressure monitoring in shallow observation well P300. This operational pressure–temperature monitoring successfully ensured and proved a safe, smooth and reliable injection operation. A vital part of the operational P–T data comes from the downhole P–T measurements, which are recommended for any CO2 storage site. Without this downhole information, it would not have been possible to provide the complete picture of CO2 injection. The recommended downhole installation design of P–T tools distinguishes CO2 storage from the operational engineering of underground storage of natural gas, where BHP monitoring can be done via WHP recording. The DTS safety monitoring along the injection tubing supported typical operational processes as conditioning of the CO2 and improvement of injection rate and injection temperature and will be beneficial to any CO2 storage project. The above-zone pressure monitoring gives no hints to any hydraulic connection or CO2 leakage through or failure of the cap rock.

Air conditioning production by a single effect absorption cooling machine directly coupled to a solar collector field. Application to Spanish climates

Due to the increasing energy consumption of air conditioning in buildings and the need to decrease the fossil CO2 emissions to the environment, the interest of using renewable energy sources shows up stronger than ever. We present a general study whose aim is to propose a method to evaluate an upper bound in the potential of solar cooling by using some simplified models. As an example it has been applied to the very diverse climates of Spain. In the paper it has been assumed a direct solar coupling between the solar collector field and a single effect absorption cooling machine, without any intermediate solar storage tank. An equation is obtained that shows the dependence of the generator/solar-collectors equilibrium temperature on basic design parameters of the system (absorption machine-solar collectors). The paper analyzes the effect of these on the total amount of cooling produced along a typical mean year and the peak cooling power. The paper also includes a discussion on how to estimate the values and what is their physical meaning of the parameters which define the behavior of real absorption machines. Finally tables are included for the 12 climates of Spain that can be used as an example of how to make a quick pre-sizing of such direct coupled system. The classification of the Spanish climates is based on general data (average monthly total horizontal solar radiation, average monthly dry temperature, etc.) and the results could be generalized for climates with the same severity. Moreover if hourly weather data is available for any place (like tmy2, bin, epw, etc. files), the procedure can be applied without further changes.

Global Optimization of Large-Scale Generalized Pooling Problems: Quadratically Constrained MINLP Models

The generalized pooling problem is a generic way of identifying a topology containing sources nodes, intermediate storage tanks, and sinks when monitoring specific stream qualities is imperative. One important application domain of the generalized pooling problem is wastewater treatment. Choosing among the wide array of available wastewater treatment technologies is a combinatorially complex optimization problem that requires nonconvex terms to monitor regulated stream qualities about a treatment plant. In this work, we address five instantiations of the generalized pooling problem to global optimality by introducing (i) a quadratically constrained MINLP model formulation that reduces the number of bilinear terms, (ii) novel piecewise underestimation methods for the nonconvex bilinear terms to tighten the relaxation [Gounaris et al. Ind. Eng. Chem. Res. 2009, 48, 5742−5766; Wicaksono and Karimi AIChE J. 2008, 54, 991−1008], and (iii) a branch-and-bound algorithm suited to address the combinatorial complex...