Volume 2, Issue 2 (June 2024) – 4 articles

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Case Report

26 February 2024

‘Greening’ an Oil Exporting Country: A Hydrogen and Helium Closed-cycle Gas Turbines Case Study

Holistic decarbonisation requires collaborative efforts and substantial investments across diverse economic sectors. This study introduces an innovative national approach, blending technological insights and philosophical considerations to shape decarbonization policies and practices. Libya is the case study. The proposed framework involves submersible power stations with continuous-duty helium closed-cycle gas turbines to supply electricity demand and hydrogen. Extensive national data is analysed, incorporating factors such as sectoral consumption, sea temperature, and port locations. An analytical model is developed, providing a valuable foundation for realistic decarbonization scenarios. The model aims to maintain the benefits of current energy consumption, assuming a 2% growth rate, while assessing changes in a fully green economy. The results offer qualitative and quantitative insights on hydrogen use and an expected rise in electricity demand. Two scenarios are examined: self-sufficiency and replacing oil exports with hydrogen exports. This study provides a quantitative perspective on decarbonization, focusing on a submersible helium closed cycle gas turbine concept resistant to natural disasters and proliferation. Findings underscore the substantial changes and investments needed for this transition, identifying primary needs of 27 GW or 129 GW for self-sufficiency and exports, respectively. This foundational analysis marks the start of research, investment, and political agendas toward decarbonization.

Article

13 March 2024

The Potential of Salinity Gradient Energy Using Reverse Electrodialysis to Generate Electricity for Seawater Desalination Plants, an example from Western Australia

Seawater desalination plays a vital role in addressing the increasing global demand for freshwater. However, the energy-intensive nature of desalination processes and the generation of brine by-products pose environmental challenges. In Western Australia (WA), approximately 48% of freshwater is supplied by two seawater desalination plants employing the energy-intensive seawater reverse osmosis (SWRO) method. These plants are powered by a combination of renewable and conventional energy sources. Typically, the most efficient approach for desalination plants involves a blend of renewable energy sources. Salinity gradient energy (SGE) harnessed through the reverse electrodialysis (RED) system, which derives energy from mixing waters with varying salinities, has emerged as a potential solution. RED utilizes ion-exchange membranes to convert the chemical potential difference between two solutions into electric power. The net specific energy of SGE, calculated based on the Gibbs free energy associated with mixing seawater and wastewater, is estimated at approximately 0.14 kWh per cubic metre of brine for SWRO desalination plants. The combined SGE potential of WA’s two desalination facilities theoretically amounts to approximately 87.4 MWh of energy. However, due to the inherent limitations of the RED system’s current energy efficiency, only about 2.5% of the desalination plant’s energy requirements can be met through this technique. This paper addresses a significant gap in the literature by analyzing the technical and economic constraints of utilizing salinity gradient energy (SGE) through the reverse electrodialysis (RED) system for seawater desalination plants. This marks the first examination of its kind, shedding light on both the technical feasibility and economic challenges of SGE-RED application in this context. The scientific contribution lies in its innovative approach, integrating technical and economic perspectives to provide an understanding of SGE-RED technology’s potential drawbacks and opportunities. By identifying and tackling these challenges, this paper aims to pave the way for optimizing SGE-RED systems for practical implementation in seawater desalination plants.

Commentary

25 April 2024

Monitoring Complexity in Clean Energy Systems Applications

Clean energy applications often involve systems with technological process monitoring. This supervision aims to optimize operation, in particular efficiency, performance and compatibility with dedicated criteria. Most of these energy systems involve complex procedures. A complex procedure is an arrangement of compound processes interacting in interdependent behaviors. The supervision of these complex procedures focuses on the interaction of compound processes, their digital coupling and the handling of uncertainties in their detection and digital tools. Real-virtual pairs, such as digital twins, could carry out such surveillance. This commentary aims to analyze and illustrate such supervision in clean electromagnetic energy systems based on a review of the literature. The notion of complexity and the interactions of the compound processes involved are first addressed and detailed. The modeling of these interactions is presented through the mathematical coupling of the electromagnetic equations with other equations of the phenomena involved. These phenomena are linked to the functional or environmental behaviors of the systems. Compound process monitoring in complex procedures is then analyzed taking into account threats, unsolicited external events and uncertainties related to the sensing and digital tools involved. This contribution illustrated several points relating to, the relationship between the complexities of a real energy procedure and its coupled virtual model, the dependence of the model reduction strategy on each specific application and the reduction of uncertainties through the matching of real-virtual pairs. The different analyses are supported by literature references permitting more information when necessary.

Article

23 May 2024

Numerical Study on Pyrolysis Characteristics of Oil-Based Drilling Cuttings in a Two-Layer Screw-Driving Spiral Heat Exchanger

Oil-based drilling cuttings is a pollutive nearly-solid waste produced in oil exploitation that has to be treated for meeting clean production requirement of oil and gas exploration. A two-layer screw-driving spiral heat exchanger was thus proposed for this purpose. To investigate its effectiveness and performance, a 10-component n-decane one-step product proportional distribution chemical model was used to describe oil-based drilling cuttings pyrolysis process, and numerical simulations were carried out of forced convection inside the heat exchanger with a full consideration of pyrolysis and evaporation effects. The influences of rotation speed, screw pitch and cross-sectional shape of spiral tube on pyrolysis, flow, and heat mass transfer characteristics were studied. The results show that the heat absorbed needed for evaporation is much less than that for pyrolysis, and the heat transfer coefficient with consideration of evaporation and pyrolysis is almost two times greater than that without. The pyrolysis rate increases first, and then decreases once the temperature is higher than 838 K due to the coupled effects of temperature and reactant concentration change. The velocity, heat transfer coefficient and conversion ratio of oil-based drilling cuttings all increase with rotation speed, but the conversion ratio increase becomes slower and slower once the rotation speed exceeds 0.2 rad·s−1. The average vorticity and flow resistance of oil-based drilling cuttings both decrease with screw pitch monotonously, while heat transfer coefficient increases first and then decreases because of the opposite effects of centrifugal force and thermal entrance length. Reducing screw pitch can increase conversion ratio, but once screw pitch is smaller than 800 mm, the conversion ratio approaches to a constant. Cross-sectional shape of spiral tube also affects pyrolysis performance, and circular cross-sectional spiral tube seems to be the best.

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