Abstract

Data center cooling systems consume a significant amount of electricity. The temperature of heat source (hot indoor air) and cold source (outdoor air) is usually ungraded, which results in wasted heat transfer temperature difference. A novel multi-stage cooling system is proposed to match different temperature grades of heat sources with corresponding cold sources. The heat transfer process and energy saving principles of the cooling system are illustrated using T-Q diagrams. A theoretical model is established based on the system heat transfer characteristics. The mismatch coefficient δ and entransy dissipation ΔJ of multi-stage cooling system both reduced by 6.7% compared to single-stage system, and the total temperature difference at natural cooling mode is reduced by 1.3 °C. The multi-stage cooling system offers a new approach to enable greater natural cold sources utilizations and lower power consumptions.

Abstract

This paper proposes a data-driven linear model predictive control (MPC) method to assess wind farm capability of primary frequency regulation (PFR) and reasonably allocate droop coefficient to wind turbines (WTs). The proposed method transforms the wind farm PFR nonlinear model into a linear model by using Koopman operator theory (KOT). Hence, a convex optimization problem is constructed based on a linear MPC model, which makes real-time analytical solution possible. Furthermore, the linear model coefficient matrix can be obtained by data-driven training, which is independent of complete model and accurate parameters. The case study validates that the proposed method can achieve high-accuracy assessment and allocation that the relative error is less than 1.60e-2 p.u. by only using historical operation data, and is suitable for online applications owing to the fast calculation speed, which the average assessment time is no more than 0.93s.

Abstract

As a clean, efficient, and safe new energy carrier, hydrogen is widely utilized in the construction, transportation, and power industries, and it is also one of the critical directions of the world energy transition. China produces about 2/3 of hydrogen through coal-tohydrogen as the world’s largest hydrogen producer and significant consumer. However, “grey hydrogen” generates lots of carbon dioxide (CO2) emissions through the combustion of fossil fuels. As an effective way to achieve rapid carbon reduction in the future, Carbon Capture, Utilization and Storage (CCUS) technology is regarded by the IEA as a bottom-up technology to achieve carbon neutrality. This study presents a CCUS retrofit planning method based on the classic coal-tohydrogen process and CCUS technology. Carbon capture devices capture CO2 through the electricity supplied by the hydrogen power generation unit, the remaining electricity can be sold for revenue; meanwhile, captured CO2 can be further utilized to profit. The cases discuss the effectiveness and economy of the planning model from the perspectives of full-chain carbon footprint and the levelized cost of hydrogen (LCOH) production. The simulation results show that the LCOH in the proposed retrofit planning method is 9.65ï¿¥/kg. Compared with the unretrofitted scenario, the full-chain carbon footprint is reduced by 79.7%, and the LCOH is increased by 36.5%.

Abstract

Biogas is a type of sustainable energy produced by the anaerobic decomposition of organic matter derived from plants and animals. Biogas comprises significant quantities of CH4, CO2, and minor concentrations of H2S. The substance is naturally introduced into the surrounding ecosystem, with its composition exhibiting variability contingent upon its origin. The biogas reforming process was conducted in a DBD-NTP reactor, using catalysts to enhance the total reaction efficiency under ambient circumstances. Fe/γ-Al2O3, Co/γ-Al2O3, and Ni/γ-Al2O3 catalysts were synthesized by the wet impregnation method and reduced the catalyst with H2 gas in a tubular furnace. Synthesized catalysts were analyzed by XRD, BET, XPS and SEM. Prepared catalysts are integrated into a discharge zone of a DBD reactor and tested for biogas reforming reaction. The DBD plasma system produced an applied potential ranging from 16 kV to 22 kV, while maintaining a flow rate of 70 mL min-1 with a gas mixture contains CH4, CO2, and N2 at a ratio of 30:30:10. The experiment started with performing the reaction in the absence of H2S, followed by reaction with the addition of 0.054% H2S (mixed with N2), while ensuring a consistent residence duration. The data obtained from observations suggests that H2S exerts a substantial influence on the process of conversion. When H2S was added, the CH4 conversion drastically decreased from 24% (without H2S) to 15% (with H2S), and the CO2 conversion decreased from 21% to 17% at 22 kV with Ni/ γ-Al2O3 catalyst packed DBD. H2S also has an impact on energy efficiency and syngas ratio. Moreover, H2S has more impact on CH4 than CO2.

Abstract

The transition toward a low-carbon economy will have important implications for major mineral-exporting countries. We examine the distribution of these minerals across emerging markets and developing economies (EMDEs) and identify potential implications, notably fiscal implication, for these economies due to the shifting patterns of demand that are likely to result from the energy transition. Producers of specific minerals like copper, nickel, and graphite stand to gain from the projected increase in demand for these minerals over the next two decades or so. These countries include Brazil, Chile, China, Mozambique, Peru, Philippines, and Indonesia. Our study emphasizes the need for proactive government planning and policies to seize economic opportunities and mitigate potential risks arising from the low-carbon transition.

Abstract

Rapid urbanization and rising energy demand in cities have stimulated research into sustainable energy solutions. The challenges reside in designing cities that not only meet energy needs but also reduce their environmental impact. This necessitates a comprehensive framework that integrates the necessary elements for the development of sustainable energy city. Japan has risen to the challenge by incorporating renewable energy, energy storage, and innovative energy management technologies into its urban planning. This study seeks to evaluate Japan’s approach to sustainable energy city development and recommend a framework for Malaysia or developing economies alike on sustainable energy city deployment. Additionally, it suggests a business alliance between Japan and Malaysia to promote socioeconomic benefits and sustainability objectives in both countries. A visit to a sustainable energy city in Japan was conducted for on-site evaluation of infrastructures and technologies, as well as interviews with the management company. Japan’s comprehensive approach to supportive policies and incentives has aided in the development of sustainable energy cities supported by public-private partnerships and active community participation. The key energy components of the Japan’s case study include both energy management and resilience approach. The proposed cooperation between Japan and Malaysia has the potential to promote long-term growth, shared prosperity, and contribute to global efforts in combating climate change.

Abstract

The demand for cooling of buildings is continuously growing due to global warming contributing to more global CO2 emissions. Escalating resource costs and climate change risks intensify the need for efficient cooling solutions. Phase change materials have been used in building envelopes to reduce the energy consumption. However, these materials are often costly, which creates a barrier for their implementation. Reducing the PCM quantities without compromising their behavior provides a substantial reduction to their overall payback period and increases their feasibility. This study aims to optimize the incorporation of encapsulated PCM in building envelopes by studying the effect of their distribution pattern within the walls. The simulations are done using 2D finite element method. The results indicate that PCM distribution has an important effect on the efficiency of the design and an optimal distribution can allow the reduction of PCM quantities in a wall. In the studied case, the lowest cooling load was found at 14% volumetric percentage of PCM rather than 30% if optimal distribution is used. This consequently have important implications on the need for geometrical optimization when it comes to encapsulated PCM systems.

Abstract

The increasing importance of electric vehicles lies in their lower emissions compared to fossil fuel vehicles. However, challenges like long charging times and range anxiety hinder their widespread adoption. Battery swapping stations offer a practical solution to expedite EV refueling, reducing wait times and range concerns. This research proposes a battery-swapping architecture that provides battery-swapping services to electric vehicles while exploring additional revenue sources and cost reductions. The model uses batteries of the battery swapping station as a battery energy storage system, supplying power to mobile or stationary loads during grid or renewable energy source downtime. By offering cost-effective electricity during peak hours or non-availability, the model demonstrates up to a 35% reduction in consumer electricity costs during peak hours and an 8.8% reduction in overall costs during 24-hour operation. The implementation combines linear programming with machine learning to forecast renewable energy output and electric vehicle energy demand, considering flexible battery charging and discharging controls and degradation processes. These optimization results show the potential of the proposed model to boost battery swapping station income and cut costs, contributing significantly to the electric vehicle market’s growth.

Abstract

The quest for energy sustainability and clean water is at the forefront of humanity’s challenge today. This research aims to utilize an integration of parabolic trough solar power plant with sCO₂ Brayton cycle coupled with a direct contact desalination system. An integrated model was developed to achieve the aim. The results illustrated that thermal and exergetic efficiency increased with Pressure Ratio (PR) increment and peaked at around PR of 3.2 and decreased thereafter. The change in net work output (ΔWnet), transitioning from 101 kW to 7 kW as PR increases from 2.7 to 3.2, indicates a reducing rate of increment. However, from PR 3.2 to 3.7, ΔWnet showed negative values, from -1 kW to -74 kW, reflecting not only reducing efficiencies, but also an increasing rate of its reduction. Increasing the bottoming cycle pressure continuously reduces efficiency, with minor declines between pressures of 7400 to 7600 kPa due to sCO₂ density changes near the critical point. Furthermore, the interplay between pressure ratio (PR) and the bottoming cycle (P1) affects both water production and the number of DCMD units required. Water production and DCMD units required showed an inverse relationship with sCO₂’s cycle efficiencies.

Abstract

Hydrogen is considered one of the most promising alternative fuels for aviation, which can be used to power aircraft and airport ground services. Onsite hydrogen production from renewables can be suitable for small-size airports, while the larger size airports can be supplied through transportation either from dedicated green hydrogen production plants or other sources of hydrogen. This paper presents a study of two hydrogen supply scenarios, one taking the small airport of Stockholm Skavsta as a case study for in-house hydrogen production. The second is evaluating offshore green hydrogen supply to the large size airport of Arlanda. The in-house hydrogen production evaluates 18 scenarios covering all possible scenarios for alkaline, PEM, and solid oxide electrolysis as production means and compressed, cryo-compressed, and liquid gas as storage, with power supply from grid and grid plus in-house solar system. The optimum production and storage facility size is determined in association with the levelized cost and carbon emissions for each scenario. For the large-size airport, the study evaluates the hydrogen supply from offshore production facilities transported as compressed, cryo-compressed, or liquid gas via offshore pipeline and onshore pipeline, Offshore pipeline and truck, Ship and onshore pipeline, or Ship and truck. The results showed the levelized cost to be between 2.93 – 2.44 Euro/kg H2 in the case of in-house production. Compressed hydrogen offshore and onshore pipeline is the least cost for Arlanda airport hydrogen supply. This paper demonstrates a direction for aviation sector decarbonization and establishes a pathway for airports’ in-house hydrogen production and outsourced hydrogen supply.