Flexible design and operation of off-grid green ammonia systems with gravity energy storage under long-term renewable power uncertainty

Special issue on “Optimal design and operation of energy systems”

Uncertainty arising from climate change poses a central challenge to the long‐term performance of many engineered water systems. Water supply infrastructure projects can leverage different types of flexibility, in planning, design, or operations, to adapt infrastructure systems in response to climate change over time. Both flexible planning and design enable future capacity expansion if‐and‐when needed, with flexible design proactively incorporating physical design changes that enable retrofits. All three forms of flexibility have not previously been analyzed together to explicitly assess their relative value in mitigating cost and water supply reliability risk. In this paper, we propose a new framework to evaluate combinations of flexible planning, design, and operations. We develop a nested stochastic dynamic optimization approach that jointly optimizes dam development and operating policies under dynamic climate uncertainty. We demonstrate this approach on a reservoir project near Mombasa, Kenya. Our results find that flexible operations have the greatest potential to reduce costs. Flexible design and flexible planning can amplify the value of flexible operations under higher discounting scenarios and when initial infrastructure capacities are undersized. This approach provides insight on the climate change and techno‐economic conditions under which flexible planning, design, and operations can be best leveraged individually or in combination to reduce climate change uncertainty risks in water supply infrastructure projects.

Solar photovoltaic (PV) technology has the versatility and flexibility for developing off-grid electricity system for different regions, especially in remote rural areas. While conventionally straight forward designs were used to set up off-grid PV-based system in many areas for wide range of applications, it is now possible to adapt a smart design approach for the off-grid solar PV hybrid system. A range of off-grid system configurations are possible, depending upon load requirements and their electrical properties as well as on site-specific available energy resources. The overall goal of the off-gird system design should be such that it should provide maximum efficiency, reliability and flexibility at an affordable price. In this chapter, three basic PV systems, i.e. stand-alone, grid-connected and hybrid systems, are briefly described. These systems consider different load profiles and available solar radiations. A systematic approach has then been presented regarding sizing and designing of these systems. Guidelines for selection of PV components and system sizing are provided. Battery energy storage is the important component in the off-grid solar PV system. Due to load and PV output variations, battery energy storage is going to have frequent charging and discharging. So the type of battery used in a PV system is not the same as in an automobile application. Detailed guidelines for selection of battery are therefore also provided. At present, most of the world-wide PV systems are operating at maximum power points and not contributing effectively towards the energy management in the network. Unless properly managed and controlled, large-scale deployment of PV generators in off-grid system may create problems such as voltage fluctuations, frequency deviations, power quality problems in the network, changes in fault currents and protections settings, and congestion in the network. A possible solution to these problems is the concept of active generator. The active generator will be very flexible and able to manage the power delivery as in a conventional generator system. This active generator includes the PV array with combination of energy storage technologies with proper power conditioning devices. The PV array output is weather dependent, and therefore the PV power output predictability is important for operational planning of the off-grid system. Many manufacturers of PV system power condition devices are designing and developing new type of inverters, which can work for delivering the power from PV system in coordination with energy storage batteries as conventional power plant.

Carbon dioxide hydrogenation to methanol is one of the viable ways for large‐scale consumption of renewable energy. The intermittent and stochastic character of renewable energy leads to frequent changes in the operating conditions of production systems. Conventional design that focuses on the economic performance leads to rigid operating conditions and narrow operating windows of the production systems, which make it difficult to adapt to frequent changes in production capacity. It is imperative to expand the operating window of the renewable methanol production systems (RMPS) to adapt to the frequent changes in production capacity. In this work, the flexible design and regulation strategies for the RMPS are proposed, which expand the operating windows of the production systems at a low capital investment by quantitatively analyzing the relationships between process parameters and operating constraints of key equipment. The results indicate that, compared to economically optimized production systems, the proposed design method broadens the operating window of the RMPS by 54.02% with only a 22.38% increase in investment cost. The operating window can further be expanded by 113.29% with the addition of small‐scale equipment at the investment cost increasing by 117.02%. The effectiveness of the proposed method and strategies is analyzed and discussed through specific application scenarios. The proposed approach improves the flexibility of the RMPS, providing an analytical basis for the flexible design and operation of chemical production systems driven by renewable energy.

• Analysis of geothermal energy production and storage, from daily to seasonal. • Description of non-linear behavior of geothermal fields and thermal networks. • Simultaneous supply of heating and cooling demands via geothermal network. • Optimization of real-world system deployed at ETH Zurich university campus. • Definition of rationale for design and operation of geothermal fields and network. We investigate the optimal operation of multi-energy systems deploying geothermal energy storage to deal with the seasonal variability of heating and cooling demands. We do this by developing an optimization model that improves on the state-of-the-art by accounting for the nonlinearities of the physical system, and by capturing both the short- and long-term dynamics of energy conversion, storage and consumption. The algorithm aims at minimizing the CO 2 emissions of the system while satisfying the heating and cooling demands of given end-users, and it determines the optimal operation of the system, i.e. the mass flow rate and temperature of the water circulating through the network, accounting for the time evolution of the temperature of the geothermal fields. This optimization model is developed with reference to a real-world application, namely the Anergy Grid installed at ETH Zurich, in Switzerland. Here, centralized heating and cooling provision based on fossil fuels is complemented by a dynamic underground network connecting geothermal fields, acting as energy source and storage, and demand end-users requiring heating and cooling energy. The proposed optimization algorithm allows reducing the CO 2 emissions of the university campus by up to 87% with respect to the use of a conventional system based on centralized heating and cooling. This improves on the 72% emissions reduction achieved with the current operation strategies. Furthermore, the analysis of the system allows to derive design guidelines and to explain the rationale behind the operation of the system. The study highlights the importance of coupling daily and seasonal energy storage towards the achievement of low-carbon energy systems.

Many off-grid electrical systems in developing countries use energy storage to increase their reliability and operational flexibility. The primary goals of this chapter are to provide nonspecialists with an understanding of the basic electrochemistry occurring in chemical batteries and to describe the operation and performance of batteries from an electrical viewpoint. Particular attention is given to interpreting specifications provided by battery manufacturers. A circuit model of a chemical battery is developed which is used in subsequent chapters to analyze the operation of off-grid systems. The chapter considers flooded, absorbed glass mat (AGM), gel, and various lithium–ion batteries. Safety and maintenance aspects are covered.

Multi-scenario design of ammonia-based energy storage systems for use as non-wires alternatives

Stationary solar power plants consisting of an array of solar panels are one of the most important components of auton-omous power grids. Given the variety of existing topologies and methods for tracking the maximum power point, the purpose of this work is to review converter topologies, classify MPRT algorithms and their comparative analysis. Based on the analyt-ical review, a comparative table for the considered algorithms was compiled. By comparing the main MPRT algorithms, it was found that intelligent algorithms have a number of advantages over basic ones. However, implementation of these algorithms is complex and requires more computational resources, which until recently was a significant problem. Autonomous power systems based on distributed independent sources of generation are attracting increasing attention due to the fact that they show the ability to significantly save energy and reduce pollutant emis-sions due to high prevalence of renewable energy sources (RES).Compared to the use of electricity from traditional power plants, significant changes in requirements for the amount of electricity consumption, combined with uncertainty about available solar and wind energy for the required power generation, require implementation of energy storage systems to mitigate intermittency problems and to meet requirements of the peak electricity consumption. In the autonomous electric power system, energy storage technologies usually exist in the form of electrochemical energy storage and thermal energy storage.The cost and technological capabilities of energy storage systems are key parameters that affect optimal design and op-eration of the system. In this paper, the analysis and study of the technical and economic impact of various storage technologies for optimal design and operation of autonomous electric power systems were conducted.

With rising energy concerns, efficient energy conversion and storage devices are urgently required to provide a sustainable, green energy supply. Electrochemical energy storage devices, such as supercapacitors and batteries, have been proven to be the most effective energy conversion and storage technologies for practical application. Currently, carbon materials hold the key for the development of high-performance electrochemical energy storage devices. However, the widely used carbon materials, such as graphite and activated carbon are often derived from non-renewable resources under relatively harsh environments, which hinders the sustainable development of electrochemical energy storage systems. In this context, biomass demonstrates many desired properties to derive renewable carbon materials for both electrochemical energy storage applications, because of its natural abundance and unlimited availability. Here, natural biomass, such as cotton textile, wheat flour, and corncobs, have been explored to produce renewable carbon materials via a low-cost and high throughput manufacturing process for energy storage systems design. Excitingly, the biomass-derived renewable activated carbon scaffolds not only demonstrated hierarchically porous structures but also excellent flexibility, making them ideal backbones for next-generation energy storage design. Specifically, activated cotton textile (ACT) with excellent flexibility and conductivity has been successfully derived from cotton textile for flexible energy storage systems design, such as flexible supercapacitors, flexible lithium-ion batteries, and flexible lithium-sulfur batteries. Besides flexible ACT, carbon nanotubes (CNTs) have also successfully derived from the natural yeast-fermented wheat dough without using any extra-catalysts or additional carbon sources. Yeast-derived carbon nanotubes from the fermented wheat dough not only provide an ideal sulfur host for lithium-sulfur batteries with a record lifespan of 1500 cycles but also expand our current understanding of the synthesis of carbon nanotubes. Biowastes-corncob, have also been explored to derive onion-like carbon materials for energy storage application. These research activities not only brought new insights on the deriving renewable carbon materials from natural abundant biomass resources but also boosted the design and fabrication of next-generation flexible energy-storage devices, which hold great promise for future wearable/flexible electronics.

In the attempt to tackle the issue of climate change, governments across the world have agreed to set global carbon reduction targets. [...]

Sustainable design, integration, and operation for energy high-performance process systems

This paper is the introduction to a topical collection on “Changing Values and Energy Systems” that consists of six contributions that examine instances of value change regarding the design, use and operation of energy systems. This introduction discusses the need to consider values in the energy transition. It examines conceptions of value and value change and how values can be addressed in the design of energy systems. Value change in the context of energy and energy systems is a topic that has recently gained traction. Current, and past, energy transitions often focus on a limited range of values, such as sustainability, while leaving other salient values, such as energy democracy, or energy justice, out of the picture. Furthermore, these values become entrenched in the design of these systems: it is hard for stakeholders to address new concerns and values in the use and operation of these systems, leading to further costly transitions and systems’ overhaul. To remedy this issue, value change in the context of energy systems needs to be better understood. We also need to think about further requirements for the governance, institutional and engineering design of energy systems to accommodate future value change. Openness, transparency, adaptiveness, flexibility and modularity emerge as new requirements within the current energy transition that need further exploration and scrutiny.

Guest editorial: Application of cloud energy storage systems in power systems

Evaluation of hierarchical controls to manage power, energy and daily operation of remote off-grid power systems

Energy-related activities are a major contributor of greenhouse gas (GHG) emissions. A growing body of knowledge clearly depicts the links between human activities and climate change. Over the last century the burning of fossil fuels such as coal and oil and other human activities has released carbon dioxide (CO2) emissions and other heat-trapping GHG emissions into the atmosphere and thus increased the concentration of atmospheric CO2 emissions. The main human activities that emit CO2 emissions are (1) the combustion of fossil fuels to generate electricity, accounting for about 37% of total U.S. CO2 emissions and 31% of total U.S. GHG emissions in 2013, (2) the combustion of fossil fuels such as gasoline and diesel to transport people and goods, accounting for about 31% of total U.S. CO2 emissions and 26% of total U.S. GHG emissions in 2013, and (3) industrial processes such as the production and consumption of minerals and chemicals, accounting for about 15% of total U.S. CO2 emissions and 12% of total ...