Flexibility In Supply Research Articles

Cost and system effects of nuclear power in carbon-neutral energy systems

Moving towards carbon-neutral societies, both nuclear and renewable energy can potentially supply CO2-free electricity. While the cost of renewable energy has decreased significantly, the cost of nuclear has, however, increased in the past decades and now in general exceeds the cost of renewables. However, one cannot compare directly the per unit cost of electricity since temporal behavior in the electricity production differs substantially between the two groups of technologies. Nuclear power inherently aims to provide a constant base load supply of electricity, while renewables generally depend on weather patterns. Thus, the two have different requirements and impact the overall system costs differently regarding flexibility and system design. Focusing on the case of Denmark, this article investigates a future fully sector-coupled energy system in a carbon-neutral society and compares the operation and costs of renewables and nuclear-based energy systems. The study finds that investments in flexibility in the electricity supply are needed in both systems due to the constant production pattern of nuclear and the variability of renewable energy sources. However, the scenario with high nuclear implementation is 1.2 billion EUR more expensive annually compared to a scenario only based on renewables, with all systems completely balancing supply and demand across all energy sectors in every hour. For nuclear power to be cost competitive with renewables an investment cost of 1.55 MEUR/MW must be achieved, which is substantially below any cost projection for nuclear power.

Coupling energy management of power systems with energy hubs through TSO-DSO coordination: a review

Abstract The transition towards a sustainable energy system requires the integration of high-penetration renewable energy sources (RESs) and the use of new energy management frameworks to handle RES variability and uncertainty. The evolution of novel energy management technologies has made it possible to design and operate integrated energy systems (IESs) that couple various energy carriers such as electricity, heat, and gas. The emergence of energy hubs (EHs) offers the potential for greater efficiency, reliability, and flexibility in energy supply and demand. However, integrating EHs into the power system operation remains a significant challenge due to the complex interaction between the transmission system operator (TSO), distribution system operator (DSO), and EHs. Enhanced coordination between TSOs and DSOs is of the utmost importance within this context. This paper first aims to review and highlight the most practical features of EHs including the EH concept, topology, elements, classifications, flexibility resources, and optimization approaches. Subsequently, it describes TSO-DSO roles and all concepts that are in line with the aims of this subject, such as conceptual framework, TSO-DSO coordination schemes, formulation, and solution techniques. Meanwhile, it will identify any remaining research gaps and prospective trends in this respect.

Tri-generation design and analysis of methanol-reforming high-temperature fuel cell based on double-effect absorption cooling power cycle

The methanol-reforming based high-temperature proton exchange membrane fuel cells is promising in both stationary and mobile applications, due to the trade-off between the efficiency and durability. However, challenges arise in the system integration due to the coupling of various-grade heat flows. Additionally, the exiting waste heat recovery systems face thermal-electric coupling issues, leading to limited flexibility in the energy supply. To this end, a thermally coupled tri-generation system based on methanol-reforming high-temperature proton exchange membrane fuel cell and double-effect absorption cooling power cycle is proposed. The cooling oil cycle absorbs heat from the fuel cell stack and burner, supplying heat for the preheaters, methanol reformer and double-effect absorption cooling power cycle. The cooling and power outputs of the double-effect absorption cooling power cycle are flexibly adjusted by varying the vapor split ratio. The mathematical models are developed and validated, based on which the exergy, exergoeconomic, economic and environmental performances are investigated. Under the design conditions, the tri-generation system yields net power, cooling, and hot water of 102.8 kW, 64.75 kW, and 43.83 kW, respectively, with exergy efficiency of 39.0% and unit exergoeconomic cost of product exergy of 65.09 $/GJ. The economic and environmental analyses indicate that, compared to the conventional system, a 54.2% reduction in carbon dioxide emissions is achieved, and the payback periods stand at 4.0, 5.6 and 9.0 years for the methanol prices of 0.40, 0.45 and 0.50 $/kg, respectively.

Managing material shortages in project supply chains: Inventories, time buffers, and supplier flexibility

We consider a two‐stage project supply chain with a downstream project firm producing an engineer‐to‐order (ETO) complex product or a make‐to‐order (MTO), low‐volume, customized industrial product as a project, and an upstream contract supplier supplying a key material to the project. The project faces two uncertainties: project activity time uncertainty and material consumption uncertainty, which may be positively or negatively correlated. In anticipation of these uncertainties, the project firm has to carefully decide its promised project due date to its project customer, against which harsh penalties will be assessed, and his material order quantity to commit to the contract supplier in advance. In most practical settings, project firms order from contracted suppliers via a flexible wholesale price contract consisting of a discounted advance order price and a risk‐premium adjusted expedite order price. The discounted advance order price encourages the project firm to take more inventory risk in the supply chain, and the expedite order price incentivizes the supplier to bear more inventory risk by carrying safety stock in excess of the project firm's advance material order. We formulate an optimization model that solves the project firm's project due date and material order problem, which takes into account the supplier's strategic reaction to the project firm's material order under the flexible wholesale price contract. We show that for MTO projects, risk‐sharing with suppliers on project materials is less important to the project firm, with the project firm assuming ownership of all material inventory in the channel and setting a deliberate project due date being the key. On the other hand, for ETO projects, risk‐sharing with contracted suppliers assumes critical importance. Project firms managing ETO projects should fully exploit the flexibility in the material supply contract to optimally drive the supplier's safety stock level and set the project due date reflecting the shared risk in the supply chain.

Optimal energy management of an integrated energy system with multiple hydrogen sources

Hydrogen is considered a promising alternative to fossil fuels in an integrated energy system (IES). In order to reduce the cost of hydrogen energy utilization and the carbon emissions of the IES, this paper proposes a low-carbon dispatching strategy for a coordinated integrated energy system using green hydrogen and blue hydrogen. The strategy takes into account the economic and low-carbon complementarity between hydrogen production by water electrolysis and hydrogen production from natural gas. It introduces the green hydrogen production–storage–use module (GH-PSUM) and the blue hydrogen production–storage–use module (BH-PSUM) to facilitate the refined utilization of different types of hydrogen energy. Additionally, the flexibility in hydrogen load supply is analyzed, and the dynamic response mechanism of the hydrogen load supply structure (DRM-HLSS) is proposed to further reduce operating costs and carbon emissions. Furthermore, a carbon trading mechanism (CTM) is introduced to constrain the carbon emissions of the integrated energy system. By comprehensively considering the constraints of each equipment, the proposed model aims to minimize the total economic cost, which includes wind power operation and curtailment penalty costs, energy purchase costs, blue hydrogen purification costs, and carbon transaction costs. The rationality of the established scheduling model is verified through a comparative analysis of the scheduling results across multiple operating scenarios.

Welding Technology for Liquefied Natural Gas Tanks

Liquefied natural gas (LNG) is of great importance in the energy segment of the economy. Natural gas, has a higher calorific value, better fuel efficiency and is more environmentally friendly, thereby gaining more importance compared to oil and coal. Not only does LNG offer greater flexibility in supply, it also has cost advantages for transportation starting from a distance of 2,000 km (at sea) and 4,000 km (on land) respectively. Consequently, the LNG market will grow in the coming decades compared to two other fossil sources - oil and coal. To use natural gas, it is necessary to create safe and economically profitable transportation routes from natural gas deposits to end users. One possibility is to transport gas in a liquefied state, at low temperatures. To ensure safe and reliable storage of liquefied gas at minus 163 ° C, good physical and mechanical properties of the base material and weld (corresponding tank system) are required. To meet these high requirements, appropriate welding methods and welding materials are selected. The paper presents an analysis of activities on the development of new welding materials and improvement of welding technologies for the construction of LNG tanks.

BoSL FAL pump: A small, low-cost, easily constructed, 3D-printed peristaltic pump for sampling of waters

Water sampling is an essential undertaking for water utilities and agencies to protect and enhance our natural resources. The high variability in water quality, however, often necessitates a spatially distributed sampling program which is impeded by high-cost and large sampling devices. This paper presents the BoSL FAL Pump - a low-cost, easily constructed, 3D-printed peristaltic pump which can be made from commonly available components and is sized to suit even the most space constrained installations. The pump is 38 mm in height and 28 mm in diameter, its components cost $19 AUD and the construction time is just 12 min (excluding 3D printing times). The pump is driven by a direct current motor which is commonly available, cheap and allows for flexibility in the energy supply (5–12 V). Optionally, the pump has a Hall effect sensor and magnet to detect rotation rates and pumping volumes to improve the accuracy of pumping rates/volumes. The pump can be easily controlled by commonly available microcontrollers, as demonstrated by this paper which implements the ATmega328P on the Arduino Uno R3. This paper validates the pump for long-term deployments at flow rates of up to 13 mL per minute in 0.14 mL volume increments at accuracy levels of greater than 99%. The pump itself is scalable, allowing for a wider range of pumping rates when, for example, large volume samples are required for pathogen and micropollutant detection.

Analysis of District Heating and Cooling systems in Spain

Currently, district energy systems allow long-distance distribution of energy and the use of renewable energies, increasing their interest in the fight against global warming and the energy crisis. This paper presents the current deployment of heat and cold distribution networks in Spain in order to analyze their technical and economic potential, opportunities and future challenges. Subsequently, a comparison is made with the networks at an international level. It has been observed that heat and cold networks in Spain have increased substantially since 2013, but the installed power in 2019 of these systems to provide either heat or cold covers a very small proportion of the total demand. These systems in Spain are supplied mainly by biomass, natural gas or a combination of them, however, the use of renewable energy is still below the European average. It can be concluded that heating and cooling networks still do not have the potential to replace all the demand of the residential sector, although their implementation is important to achieve greater energy efficiency, more flexibility in supply, greater energy independence and to avoid the waste of energy resources. Thus, technical and financial barriers are identified.

Luminescent Solar Power-PV/Thermal Hybrid Electricity Generation for Cost-Effective Dispatchable Solar Energy.

The challenge in solar energy today is not the cost of photovoltaic (PV) electricity generation, already competing with fossil fuel prices, but rather utility-scale energy storage and flexibility in supply. Low-cost thermal energy storage (TES) exists but relies on expensive heat engines. Here, we introduce the concept of luminescent solar power (LSP), where sunlight is absorbed in a photoluminescent (PL) absorber, followed by red-shifted PL emission matched to an adjacent PV cell’s band edge. This way the PV cell operates nearly as efficiently as under direct illumination but with minimal excessive heat. The PL absorber temperature rises because of thermalization, allowing it to store the excessive heat, which can later be converted into electricity. Tailored luminescent materials that support an additional 1.5 kW h PV electricity for every 1 kW h of (virtual) heat engine electricity with a dynamic shift between the two sources are experimentally demonstrated. Such an ideal hybrid system may lead to a potential reduction in the cost of electricity for a base-load solution.

Implicaciones del consumo y de la flexibilidad de la oferta laboral en el bienestar de los partícipes de planes de pensiones del Sistema de Empleo

This work aims to carry out a comparative analysis of the pension plans of the employment system (both defined benefit and defined contribution plans) from the point of view of the welfare perceived by each worker. Considering flexibility in the labor supply of the promoting company of the pension scheme, we seek to maximize the utility of the time preferences of consumption and leisure for each employee. We propose a dynamic optimization problem of intertemporal choice, and we describe both the returns on the investments of the Fund and the annual wage growth rates as discrete markovian processes. For each type of pension plan, we analyse the optimal consumption and leisure values that maximize the utility (welfare) of the worker over several periods of time.

Evaluation of field-stored switchgrass hay as bedding material for broilers

Summary Availability and expense of preferred bedding materials such as pine shavings has prompted evaluation of other materials. Grass hay derived from high-yielding biomass cultivars has been successfully employed as bedding material in both research and commercial applications. Grass hay for ruminant feed can be stored outdoors if protected, and outdoor storage may provide additional flexibility in transportation and supply of grass hay bedding. This study examined live performance in straight-run broilers reared on new grass hay bedding and grass hay bedding that had been stored outdoors in polyethylene wrap for 2 seasons. Live performance was affected primarily in the starter and grower phases, with stored hay bedding treatments resulting in depressed BW (59 g difference; P = 0.0034) and body weight gain (58 g difference; P = 0.0038) in the grower phase. FCR was significantly elevated in both the starter phase (0.02 g:g difference; P = 0.0052) and the grower phase (0.07 g:g difference; P

A framework for analyzing trade-offs in cost and emissions in power sector

Current electricity markets operate on a cost minimizing objective for power supply. However, countries across the world need to decarbonize their power systems in line with their policy objectives to mitigate climate change. In this context, this paper presents a framework to analyze synergies and trade-offs in cost and emission minimization strategies in the power sector. Emission minimizing objective can reduce emissions from existing fleets having flexibility in electricity supply, regardless of renewable energy capacity additions. This framework can also provide us with win-win strategies for reducing emissions while keeping costs low.An optimization model is developed for case study of India with data of 568 coal and 199 gas thermal units to analyze alternative real time dispatch and operating strategies. The cost and emission optimal supply strategies are compared in terms of power plant operations, emission reductions, and resulting cost of carbon abatement. The results show that 9.8% of carbon dioxide emissions can be reduced with 19% increment in the cost of electricity in emission minimizing strategy with respect to cost minimization. The operations in emission optimal supply strategy require additional 28 million dollars per day. The cost of carbon abatement is 99–129 dollars per tonne.

Evaluation of the energy efficiency of an industrial consumer in trigeneration mode

The optimization of the energy supply solution of an industrial facility is a main objective of any management program within a company, having as desideratum: quality, safety and flexibility in energy supply. The electricity and heat supply (heat and cold) using a trigeneration plant is a modern technological solution, with high energy efficiency performance and low impact on the environment. Also, this technology is economically efficient, assuring the reduction of the global energy consumption of the industrial society, and implicitly the increasing of the profit. The input data considered in this paper are the values and the characteristics of the demands of the three energy forms belonging to the analysed industrial consumer. The structure of the thermal energy both as heat (technological steam, heating, domestic hot water) and cold (air conditioning) is considered. The consumption of the electricity covers the need of both the technological process and of the buildings (power supply and lighting). In a first stage, the most suitable technological solution for the specific conditions and characteristics of the needs is chosen. The multicriteria analysis of the proposed technological solution is performed during the next stage.

A portable device for nucleic acid quantification powered by sunlight, a flame or electricity.

A decentralized approach to diagnostics can decrease the time to treatment of infectious diseases in resource-limited settings. Yet most modern diagnostic tools require stable electricity and are not portable. Here, we describe a portable device for isothermal nucleic-acid quantification that can operate with power from electricity, sunlight or a flame, and that can store heat from intermittent energy sources, for operation when electrical power is not available or reliable. We deployed the device in two Ugandan health clinics, where it successfully operated through multiple power outages, with equivalent performance when powered via sunlight or electricity. A direct comparison between the portable device and commercial qPCR (quantitative polymerase chain reaction) machines for samples from 71 Ugandan patients (29 of which were tested in Uganda) for the presence of Kaposi’s sarcoma-associated herpesvirus DNA showed 94% agreement, with the four discordant samples having the lowest concentration of the herpesvirus DNA. The device’s flexibility in power supply provides a needed solution for on-field diagnostics.

Borrowing constraints, effective flexibility in labor supply, and portfolio selection

We study optimal job switching and consumption/investment policies of an economic agent under the borrowing constraints against future labor income in a continuous and infinite time horizon. The agent’s preference is given by the Cobb–Douglas utility function whose arguments are consumption and leisure, and the jobs are characterized by the trade-off between labor income and leisure. We obtain a closed-form solution to the optimization problem by using the martingale and duality method, and investigate theoretical implications of it. The most interesting finding for the optimal job switching policy is that the borrowing constraints in the financial market can decrease the effective flexibility in labor supply of the agent in the labor market. Thus, an environment of the financial market can affect an agent’s decision making in the labor market. We also show how the effects of the borrowing constraints on the optimal consumption/investment policy reinforce or compete with those of the job switching opportunities.

Coordinated Control Strategies for Fuel Cell Power Plant in a Microgrid

Solid-oxide fuel cell (SOFC) power plant plays a vital role in a hybrid alternative energy based microgrid due to its reliability and flexibility in power supply. However, the control of SOFC is challenging in terms of providing a fast load tracking while maintaining the fuel utilization rate within a safe range. To this end, this paper builds two basic coordinated control strategies (CCS) for power management of SOFC-based microgrid. The first is “Fuel Cell follows Inverter” scheme, where fast tracking is preferred while SOFC may operate on the edge of the safety range. The second is “Inverter follows Fuel Cell” scheme, where high security is guaranteed by sacrificing performance in load tracking. To obtain a robust and simple scheme, energy balance principle is used in CCS such that PI controller is sufficient to fulfill the basic duties. Moreover, a simple supervisory control strategy is proposed for microgrid to provide a reasonable power reference for SOFC. The control system is designed and tuned based on an SOFC plant with inverter's average model. The efficiency of the proposed strategies is validated via a grid-connected SOFC/photovoltaic microgrid.

Flexibility, dynamism and diversity in energy supply and demand: A critical review

Flexibility is vital to the operation of electricity systems. It ensures that the system can keep supply and demand in balance in real time. Until recently the provision of flexibility was a fortunate by-product of thermal power generation using fossil fuels as a convenient storage medium. The rapid emergence of renewables poses a major challenge to this model. As thermal power stations are increasingly displaced with more variable renewable sources of electricity, new forms of flexibility are urgently needed. Two promising candidates for this role are energy storage and demand side response.This paper argues that in low carbon systems flexibility may at times and in certain places supersede the need for component efficiency, in order to improve overall system efficiency. We reach this conclusion after reviewing the origins of flexibility on the supply and the demand side. In both domains the concepts of material redundancy, tolerances and skills are pertinent and help our understanding of the potential for and limitations to flexibility.On the demand side new capacities may need to be developed, including skills and societal norms, if the gap between technical and realised potential is to be closed.

Analyzing the interaction of factors for flexibility in supply chains

PurposeIn the present scenario of global competition and economic recession, most of the organizations are facing tough challenge to survive in the market because of shortening product life cycle and reducing profit margin. Customers are seeking better design, production and delivery, which have made firms to concentrate on flexibility in supply chains. Therefore, the purpose of this study is to identify major factors and develop a suitable framework for flexibility in supply chains.Design/methodology/approachBased on literature review, about 14 factors have been identified. To develop relationship among these factors, a team of five experts from industry and academia was formed. Based on inputs from experts, different relationships are developed among factors to form structural self-interaction matrix (SSIM). Based on this matrix, a flexibility framework is developed by interpretive structural modelling approach.FindingsTop management commitment, strategy development for flexible SC, application of advance technology and IT tools, information sharing in SC members, trust development among supply chain members have emerged as major driving factors. Logistics and warehouse management, suppliers flexibility, distribution flexibility and manufacturing flexibility have emerged as dependent factors.Research limitations/implicationsFramework developed in this study is based on interpretive structural modelling. This framework can be further validated with some case analysis and empirical findings.Originality/valueFindings of the study can be useful for industry professionals to develop strategies for flexible supply chains. It will help them in taking new initiatives for making supply chains more responsive and proactive for customers demand.

Costs of Power Supply Flexibility: The Indirect Impact of a Spanish Policy Change

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After monetary policy, climate policy: is delegation the key to EU ETS reform?

Since the crash of carbon prices in phase II of the European Union Emissions Trading System (EU ETS), many have argued that the low price mirrors structural failures requiring intervention. A wide range of reform options have been suggested, including delegating the governance of the carbon market to an independent authority. This article analyses the debate by reconstructing the various arguments for or against reform. Three possible drivers of the price decline are investigated: (1) exogenous shocks; (2) insufficient credibility; and (3) market imperfections. It is argued that the extent to which a low price is problematic and warrants reform depends on the specific objectives associated with the EU ETS and the perception on the functioning of the market. A two-dimensional EU ETS Reform Space, comprising the degree of price certainty within the EU ETS and the level of delegation, is devised. Within the Reform Space, EU ETS reform options currently discussed are mapped. This descriptive structure offers a framework to clarify whether delegation responds to various concerns with respect to the EU ETS. Delegation might enhance flexibility under unforeseen circumstances, decrease policy uncertainty, and increase the credibility of long-term policy commitments. However, higher degrees of delegation face challenges including democratic legitimacy and political feasibility.Policy relevanceIn January 2014, the European Commission proposed a structural reform of the EU ETS characterized by a quantity triggered Market Stability Reserve, increasing flexibility in allowance supply. However, intense debate has revealed considerable differences in opinion regarding the need for and objectives of any adjustment mechanism. Other proposals, including various degrees of delegation to a rule-based adjustment mechanism or an independent authority as well as degrees of price certainty, were also suggested. This article offers a new framework, the EU ETS Reform Space, to compare reform options more systematically. This work therefore contributes to structuring the policy debate by providing a tool to better understand the merits and demerits of various reform proposals