Intermittent Production Research Articles

EFFECT OF COMMUNITY AND INFRASTRUCTURAL ISSUES ON OPERATIONAL EFFICIENCY OF OIL AND GAS ORGANIZATIONS IN KENYA

Purpose: The study investigated effect of community and infrastructural issues on operational efficiency of oil and gas organizations in Kenya
 Methodology: This study applied descriptive research design and employ exploratory research to explore the variables. The population of interest in this study comprised of 37 selected entities involved in exploration. The 37 entities formed the study units from which respondents were drawn from community liaison, management, operations, quality and security departments giving a target population of 148 respondent.
 Findings: Results indicated the significant and challenging issues faced by exploration organizations are diverse and dispersed in their nature. The exploration organizations have to face the risks whether they emanate internally or externally as they operate or envision to operate in Kenya.
 Unique Contribution to Theory Practice and Policy: The study points out that organizational changes should be based on reducing the impact of risk factors and is in line with the postulates of theory of constraints theory that drove this study. This theory is general and useful only as a technique for scheduling intermittent production systems to make operations lean. Operational managers need to visit research papers to ascertain what the contributors to their performance metrics are.

Acceptance of Demand Response and Aggregators as a Solution to Optimize the Relation between Energy Producers and Consumers in order to Increase the Amount of Renewable Energy in the Grid

Demand response plays a very important role in balancing the intermittent production of an increasing share of renewable energy sources on the energy market. This article analyses the importance of demand response and the role of aggregators for the new development of the electricity market, where the renewables will play a more important role. The main objective of this research is to determine the acceptance level of demand response and its implementation on the energy consumer side. This acceptance should include a professional actor, the aggregator which is assuming the role of optimizing the relation between energy producers and consumers, and to monitor the implementation and use of demand response. The research is based on semi-structured interviews with experts in energy from Hungary, Romania and Serbia, on workshops with experts and a wider online survey with end customers for electricity. The results indicate that there is a willingness potential to implement demand response programs with aggregators as intermediaries between energy providers and end consumers of electrical energy.

CFD simulations of a Y-junction for the implementation of hydraulic short-circuit operating mode

In the framework of the XFLEX HYDRO H2020 European Project, one of the demonstrators focuses on the implementation of the hydraulic short-circuit on the pump storage power plant of Grand-Maison owned by Electricité De France (EDF). The Grand-Maison power plant is a two-level plant production with one plant located above the downstream reservoir and equipped with four Pelton turbines; a second plant located downstream the reservoir and equipped with eight reversible pump-turbines. Hydraulic short circuit consists in running pumps and turbines in the meantime to balance the energy consumption of the pumps compared to the grid. Such an operating mode allows increasing the flexibility of the power plant and targeting the requirement of balancing the intermittent production due to the growing of new renewable energies such as wind and solar power plants. The hydraulic short-circuit operating mode leads to a change in the flow paths in the penstocks and junctions compared to the normal turbine or pump modes. Indeed, compared to the pump mode, this mode will lead to a flow derivation at the junction between the penstocks directed to the Pelton units and the penstocks directed to the upper reservoir. As this mode have not been scheduled at the beginning of the power plant construction, it is necessary to quantitatively assess the singular head losses generated at the junction to be able to simulate the complete behaviour of the power plant by means of a 1D model. CFD simulations are carried out with the Fluent software for several configurations of hydraulic short-circuit defined by the ratio of flow rate deviated to the Pelton turbines.

Application of Nanomaterials in Aqueous Redox Flow Batteries

AbstractIt is challenging to directly integrate renewable energies into the grid due to the inherent random and intermittent nature. Electrochemical energy storage techniques which can balance the intermittent production and smooth consumption are effective routes to fulfill the highly penetration of renewable energy sources. Among them, redox flow batteries (RFBs) are regarded as promising large‐scale energy storage and conversion devices attributed to the flexible design, long lifetime and high safety. Electrode and ion exchange membrane materials have crucial influences on cell performance of RFBs in terms of efficiency, rate performance, output power density and cyclability. Application of nanomaterials to obtain advanced electrode and membrane materials has prompt improvements of aqueous RFBs. This minireview includes the design, synthesis, and application of nanomaterials in preparation of both electrodes and ion exchange membranes for aqueous RFBs. Furthermore, current challenges and future prospects of application of nanomaterials in aqueous RFBs are outlined. We expect to provide a guide for the fabrication of advanced electrodes and membranes incorporation of nanomaterials towards high performance and low cost RFBs in future.

An application of continuous flow microreactor in the synthesis and extraction of rabeprazole

Abstract The oxidation of rabeprazole sulfide is a key step in the synthesis of rabeprazole, a drug for the treatment of stomach acid-related disorders. The current rabeprazole production process adopts one pot batch process, which has low reaction efficiency and poor stability. A continuous process can greatly improve the production efficiency and solve the above problems. Therefore, the reaction parameters of rabeprazole in microreactor were explored through laboratory experiments to explore the possibility of continuous production of rabeprazole. Rabeprazole sodium was synthesized by using rabeprazole thioether as a raw material and sodium hypochlorite solution as the oxidant. Oxidation, quenching, acid-base regulation and extraction were completed continuously in the microreactor. Rabeprazole solution with a purity of 98.78% (±0.13%) can be obtained continuously in 56 s, whereas intermittent production lasted for at least 2 h. Thus, the microreactor can effectively improve the oxidation synthesis efficiency of rabeprazole, and provide reference for the realization of other reactions in the microreactor.

Research on Production Pattern Optimization of Intermittent Wels

The study is focused on tight sandstone gas reservoirs with poor physical properties. The Sulige gas field is considered as an example gas reservoir: As the number of low-productivity and low-efficiency wells increases every year, the intermittent production scheme provides a way to maintain the stable production of those wells. However, the existing differences in the classification of intermittent wells and the production pattern are not conducive to the standardized management of gas wells. Therefore, according to the geological characteristics of intermittent wells, as well as the production performance, the intermittent wells were classified into three types: natural decline type (ND), poor reservoir physical property type (PRPP), and liquid loading type (LL). Furthermore, the charts of optimal shut-in time for different types of intermittent wells were established by analyzing the relationships between the shut-in time, the pressure recovery degree, and the gas productivity growth rate. Finally, according to the optimal shut-in time chart, the research results reveal the reasonable and optimal shut-in time in a well, providing the way to the production pattern optimization of the intermittent wells in the Sulige gas field.

Short-Term Electricity Load Forecasting with Machine Learning

An accurate short-term load forecasting (STLF) is one of the most critical inputs for power plant units’ planning commitment. STLF reduces the overall planning uncertainty added by the intermittent production of renewable sources; thus, it helps to minimize the hydrothermal electricity production costs in a power grid. Although there is some research in the field and even several research applications, there is a continual need to improve forecasts. This research proposes a set of machine learning (ML) models to improve the accuracy of 168 h forecasts. The developed models employ features from multiple sources, such as historical load, weather, and holidays. Of the five ML models developed and tested in various load profile contexts, the Extreme Gradient Boosting Regressor (XGBoost) algorithm showed the best results, surpassing previous historical weekly predictions based on neural networks. Additionally, because XGBoost models are based on an ensemble of decision trees, it facilitated the model’s interpretation, which provided a relevant additional result, the features’ importance in the forecasting.

Prospects and Challenges of Green Hydrogen Economy via Multi-Sector Global Symbiosis in Qatar

Low carbon hydrogen can be an excellent source of clean energy, which can combat global climate change and poor air quality. Hydrogen based economy can be a great opportunity for a country like Qatar to decarbonize its multiple sectors including transportation, shipping, global energy markets, and industrial sectors. However, there are still some barriers to the realization of a hydrogen-based economy, which includes large scale hydrogen production cost, infrastructure investments, bulk storage, transport & distribution, safety consideration, and matching supply-demand uncertainties. This paper highlights how the aforementioned challenges can be handled strategically through a multi-sector industrial-urban symbiosis for the hydrogen supply chain implementation. Such symbiosis can enhance the mutual relationship between diverse industries and urban planning by exploring varied scopes of multi-purpose hydrogen usage (i.e., clean energy source as a safer carrier, industrial feedstock and intermittent products, vehicle and shipping fuel, and international energy trading, etc.) both in local and international markets. It enables individual entities and businesses to participate in the physical exchange of materials, by-products, energy, and water, with strategic advantages for all participants. Besides, waste/by-product exchanges, several different kinds of synergies are also possible, such as the sharing of resources and shared facilities. The diversified economic base, regional proximity and the facilitation of rules, strategies and policies may be the key drivers that support the creation of a multi-sector hydrogen supply chain in Qatar.

PV-Wind-Diesel System for Energy Supply on Remote Area Applied for Telecommunication Towers in Comoros

The Comoros is an archipelago in the Indian Ocean located in the Mozambique Channel between the African continent and Madagascar. Geographically Comoros is composed of four islands: Grande Comores, Anjouan, Mohéli and Mayotte (under French administration). Apart from Mayotte, the others three independent islands commonly known as the Union of the Comoros are suffering from energy stress since their independence year 1975 until nowadays. The energy supplied and distributed by the national electricity company, SONELEC produced by diesel engines, is not stable with so much load shedding all the time. This instability energy leads to a lack of a phone network in some telecommunications towers connected to grid. The majority of telecommunications towers are located in rural areas not connected to grid and running on diesel generators, which once again leads to a problem with the telecommunications network when diesel engines fail. The two competing companies which operate in the field of telecommunications in the Comoros, namely Comores Télécom, a national public company and Telma, the private one, are still unable to ensure the provision of the telecommunications network on a regular basis. This is why we propose in the present work, a sizing of hybrid system composed essentially of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers in order to permanently ensure the provision of the telecommunications network for the well-being of the population. Our future energy must be based on non-polluting energies with significant resources. Renewable energies are the best candidates but with intermittent production especially in rural areas not connected to the national electricity grid whose energy demand is more important to meet the needs of the population. The aim of this work is the sizing of a hybrid system composed of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers located in rural areas in the Comoros. In fact, to verify the performance of the hybrid system, a numerical study has been carried out with the HOMER 2.68 Beta software using meteorological data from the Comoros. The results obtained show that this hybrid combination is more profitable in the margin of economic cost and environmental assessments with a less expensive investment. These results also show a better optimization of Wind/PV/Battery of the hybrid system used, satisfying the demand and contributing to the preservation of the environment to fight against climate change with a low cost of energy.

Studies on the thermochemical energy storage in the coal ash zeolite/water system

Deterioration of the air quality and the greenhouse effect requires replacement of the conventional fuels with renewable energy sources (RES). The main disadvantage of RES is the intermittent production of energy during the day and the different seasons. This requires efficient energy storage solutions. Affordable technologies applicable to household-scale heating are thermochemical energy storage systems (TES). TES are usually applied for concentration and storage of solar energy. TES based on zeolites as heat storage media use the exothermic effect of water adsorption. The preferred storage medium is commercial zeolite 13X, which is characterized by high porosity and a large specific surface area. In these systems, the charging is carried out at 130-180 °C and the energy storage efficiency is over 90 %. In the present study, storage media of zeolite X synthesized by the alkaline conversion of coal fly ash was studied in a laboratory assembled TES as a possible substitute of zeolite 13X. The results revealed a micro-mesoporous structure for coal fly ash zeolites (CFAZ) in contrast to the microporous 13X. The charge of TES with CFAZ can be carried out at lower temperatures, while its discharge is enough exothermic. The utilization of coal ash as raw materials for synthesis of heat storage media contribute to many environmental benefits.

Biological Methanation of H2 and CO2 with Mixed Cultures: Current Advances, Hurdles and Challenges

In order to take action against global warming and ensure a greater energy independence, countries around the world are expected to drastically increase the proportion of renewable energy in their energy mix. However, the intermittent production of energy explains why energy supply and demand do not match. In this context, biomethanation, coupled with anaerobic digestion, could be an interesting approach to transform the extra amount of produced electricity by converting hydrogen (produced by electrolysis) and carbon dioxide (present in biogas) into methane. In this review, we have summarized several recently published results which involve biological methanation processes performed by mixed cultures, with an emphasis on microbiological as well as process aspects. In particular, the different microorganisms involved in the process, as well as the used metabolic pathways, along with their kinetic and thermodynamic specificities, are described. Furthermore, the influence of process parameters such as the type of reactor, the type of diffuser and the choice of H2 injection (in situ or ex situ) or the different operating conditions are presented. Explanations of the different performances observed in literature are assumed, technical bottlenecks are listed, and possible solutions to overcome these issues are presented. Finally, the current commercial deployment of this technology is discussed through the example of three companies offering different biomethanation solutions.

Assessing Renewable Resources at the Saronikos Gulf for the Development of Multi-Generation Renewable Systems

Decarbonisation of any energy system implies that more renewables will have to be incorporated into the grid. This requires a thorough assessment of available resources to properly estimate potential contributions and identify opportunities. This work focuses on the Saronikos Gulf, which is part of the most crowded urban coastline in Greece. Solar, wind and wave resources are analysed, and the long-term characteristics affecting power production are discussed. Solar resources provide ≥250 Wh·m−2 with small long-term changes. Wind resources at coastal and onshore regions are ≥50 W·m−2; however, it has higher annual volatility. Finally, the wave resources of the region are from 130 to 170 W/m with a positive resource rate of change ≈2.5 W·m−1/year. It is expected that multi-generation by different resources, especially with temporal overlaps of wind and waves, will reduce intermittent production, hence accelerating the energy transition.

A Mathematical Model of Intermittent Gas Lift in Elevation-Production Operation with Line-Pack and Line-Drafting Phenomena in a Gas Line

This paper discusses a transient model of the intermittent gas lift technique in an oil well. The model is developed in the gas line, in the tubing-casing annulus, and the tubing. The line-pack and line-drafting phenomena in the gas line are considered in the model. A numerical approach will be used to solve the mathematical model that represents fluid flow during intermittent gas lift injection. The dynamics of important variables in the intermittent gas lift are investigated and analyzed to determine the best production strategy for intermittent gas lift. The variables are film thickness and velocity, slug height and velocity, and gas height and velocity. The relationships between surface injection control parameters (gas injection pressure and gas injection rate) and the velocity and height of film, gas, and liquid are shown in one cycle of the gas lift intermittent process. The higher the gas injection pressure, the faster the gas injection velocity, and the thinner the film thickness in the tubing. In order to obtain clean tubing from film thickness, the gas injection pressure needs to be optimized, which will lead to maintaining compressor discharge pressure availability. Detailed observation of the dynamic performance inside the tubing production well will give the optimum oil production rate for oil wells under a gas lift intermittent production strategy for field application.

Hydrogen storage alloys for stationary applications

• An alternative option to store hydrogen in a more compact and safer way than compressed gas systems, applied to a hybrid H2 – Li-ion Power-to-Power plant built in an off-grid site. In off grid locations the energy supply has always been a problem in terms of infrastructures and costs. Power-to-Power (P2P) energy systems could assume an important role especially in these sites, in order to make these places energetically independent and mostly based on renewable sources exploitation. P2P have in fact a great potential to help fixing the problem of intermittent production of RES like wind and PV. This paper aims to describe a real hybrid H 2 -battery P2P system with special focus on the topic of hydrogen storage. Today, H 2 is conventionally stored in high-pressurized vessels and this solution is linked to several technical and regulatory problems (encumbrance, safety, metal embrittlement, too large volumes going above regulatory limits in some cases, etc.). Instead, hydrogen can be absorbed in large quantities using metal hydrides, reaching volumetric density values often higher than liquid hydrogen. Discovered in the late 70 s and extensively studied in the last decades, this kind of solution has never reached a proper commercialization principally due to the limited gravimetric density values, making them unsuitable for automotive and transport purposes. But hydrogen storage alloys (HSA) can raise significant interest for stationary applications. Two of the most promising alloys are considered as applicable in a real P2P plant that will be built in Italy (Ginostra – Sicily) in the framework of the H2020 project REMOTE, modelled, designed and compared to the state-of-the-art solution based on a compressed hydrogen vessel. The final part of the paper covers the preliminary economic assessment of this new kind of plant and a future (optimistic) price trend, plotting a hypothetic learning curve.

Reducing the fluctuation of oxygen demand in a steel plant through optimal production scheduling

Sufficient and timely oxygen supply was essential for the steelmaking process to ensure product quality, production continuity and energy saving. The intermittent production mode and the simultaneous operation of several converters in steelmaking process will lead to large fluctuations of real-time oxygen demand. However, the contradiction between the limited guarantee capacity of oxygen supply and the oxygen demand fluctuation exists, which will affect production stability and lead to oxygen emissions. Therefore, the oxygen demand optimization problem of the steelmaking stage (ODOPSS) with multiple converters in a steel plant was concerned and an optimal production scheduling model was built for minimizing the oxygen demand fluctuation and the penalty of casts’ starting time deviation. To solve the model, a hybrid genetic algorithm combining variable neighborhood search (HGAVNS) was used. Results of computational experiments indicated that HGAVNS outperformed the genetic algorithm (GA) and the variable neighborhood search algorithm (VNS). The sensitivity analysis showed that the deviation penalty decreased with increasing model coefficient at the expense of increasing the oxygen demand fluctuation. Results also indicated that the more frequent supply of hot metal and increasing percentage of dephosphorized charges would in general increase the oxygen demand fluctuation. In addition, the analysis of two industrial cases showed that the oxygen demand fluctuation could be reduced by 49.32% and 51.32% respectively at most, indicating that the proposed model could be conducive to ensuring the production stability and reducing the potential oxygen emissions, so as to realize cleaner and sustainable steel production.

The role of aggregators in facilitating industrial demand response: Evidence from Germany

Industrial demand response can play an important part in balancing the intermittent production from a growing share of renewable energies in electricity markets. This paper analyses the role of aggregators – intermediaries between participants and power markets – in facilitating industrial demand response. Based on the results from semi-structured interviews with German demand response aggregators, as well as a wider stakeholder online survey, we examine the role of aggregators in overcoming barriers to industrial demand response. We find that a central role for aggregators is to raise awareness for the potentials of demand response, as well as to support implementation by engaging key actors in industrial companies. Moreover, we develop a taxonomy that helps analyse how the different functional roles of aggregators create economic value. We find that there is considerable heterogeneity in the kind of services that aggregators offer, many of which do create significant economic value. However, some of the functional roles that aggregators currently fill may become obsolete once market barriers to demand response are reduced or knowledge on demand response becomes more diffused.

Users' Adherence and Off-Label Use of HIV-Pre-Exposure Prophylaxis

HIV-PrEP (HIV-Pre-Exposure Prophylaxis) has been available through German pharmacies in various package sizes since 2017. It can be used for daily dosing or as an intermittent product used as required. The aim of this survey was to record socio-demographic basic characteristics, the respondents' medical history regarding STI (sexual transmitted infections), previous PEP (Post-exposure prophylaxis) use, the system of PrEP use, the prior diagnostics carried out as well as the advice regarding the use of PrEP and information on whether PrEP was passed on to others. A cross-sectional analysis was carried out in the form of a revised, self-developed multiple-choice questionnaire for 515 users within the network of HIV-competent pharmacies. Three-quarters of the exclusively male respondents were in the age group of 20-39 years. More than 80% used the PrEP according to recommendations. Approximately two-thirds had received PEP in the past. The same number also had, at least, one STI in previous years. The necessary previous diagnostics were mostly carried out; 7% of the PrEP is passed on to other users. The majority (approximately 2/3) of the PrEP users are high-risk users with regard to previous STI or previous PEP use, and use the PrEP according to recommendations. As a result of simpler prescribability and broader use, the importance of PrEP is expected to grow in future.

Merchant renewables and the valuation of peaking plant in energy-only markets

Abstract Merchant renewables are a new asset class. With historically high cost structures and low wholesale prices associated with merit order effects, continuity of entry has been reliant on Renewable Portfolio Standards or other policy initiatives such as government-initiated Contracts-for-Differences. But in Australia's National Electricity Market, sharply falling costs of renewables and volatile wholesale market conditions from coal plant exits over the period 2017–2020 led to a surprising number of merchant intermittent renewable investments. Adding to the merchant renewable fleet are older wind plants whose inaugural long-dated PPAs recently matured. Rolling over PPAs is possible, but not necessarily optimal. In this article, a merchant gas turbine, merchant wind, and an integrated portfolio comprising both plants are valued in the NEM's South Australian region. Asset valuations reveal surprising results. The modelling sequence shows stand-alone gas turbine valuation metrics suffer from modest levels of missing money, that merchant wind can commit to some level of forward (fixed volume) swap contracts in-spite of intermittent production, but the combined portfolio tightens overall valuation metrics significantly. Above all, the combined portfolio is financially tractable, overcoming the missing money for a gas turbine plant undertaking peaking duties. In a NEM region where intermittent renewable market share exceeds 50%, this suggests the energy-only, real-time gross pool design may yet be deemed suitable vis-a-vis meeting environmental objectives and Resource Adequacy.

Impact of Social Welfare Metrics on Energy Allocation in Multi-Objective Optimization

Resource allocation problems are at the core of the smart grid where energy supply and demand must match. Multi-objective optimization can be applied in such cases to find the optimal allocation of energy resources among consumers considering energy domain factors such as variable and intermittent production, market prices, or demand response events. In this regard, this paper considers consumer energy demand and system-wide energy constraints to be individual objectives and optimization variables to be the allocation of energy over time to each of the consumers. This paper considers a case in which multi-objective optimization is used to generate Pareto sets of solutions containing possible allocations for multiple energy intensive consumers constituted by commercial greenhouse growers. We consider the problem of selecting a final solution from these Pareto sets, one of maximizing the social welfare between objectives. Social welfare is a set of metrics often applied to multi-agent systems to evaluate the overall system performance. We introduce and apply social welfare ordering using different social welfare metrics to select solutions from these sets to investigate the impact of the type of social welfare metric on the optimization outcome. The results of our experiments indicate how different social welfare metrics affect the optimization outcome and how that translates to general resource allocation strategies.

Estimation of solar and wind energy resources over Lesotho and their complementarity by means of WRF yearly simulation at high resolution

Abstract An application of the Weather Research and Forecasting model aiming to estimate wind and photovoltaic energy resources over Lesotho is presented. To this scope, the whole year 2015 was simulated in a two-way nesting mode reaching 1 km horizontal resolution. Different model parameterizations were tested and compared to available observations, then the best performing simulation was used to elaborate wind and photovoltaic potential maps over Lesotho. Concerning the photovoltaic potential, Lesotho presents a good potential countrywide, having values ranging from around 1600 kWh/kWp to 1750 kWh/kWp, with maxima in the highlands. The results also show that there are many promising areas for wind power exploitation. Zones with higher wind potential are mainly found all along the eastern border with South Africa, from north to south and in general in the highlands. The wind potential exhibits much more variability respect to the photovoltaic one, with estimated energy production ranging from 1000 kWh/kW up to 4000 kWh/kW. Finally, an evaluation of complementarity of wind and solar electricity generation was done at different time scales, showing that some areas with negative correlation coefficient exist, where it is possible to minimise intermittent production and allowing an optimal integration in the electricity grid.