Decarbonisation pathways: renewable energy systems
Australian National University
Presentation title: Dynamics of the transition to renewable hydrogen
Abstract: Accomplishing the goal of net zero emissions by 2050 will require an economical zero-emissions fuel, such as hydrogen in addition to electrification and deployment on renewable electricity. Currently, the high production cost of zero emission ‘renewable’ hydrogen, produced from electrolysis powered by renewable electricity, is delaying its adoption.
In this study, we examine the role of uncertainties in projections of techno-economic factors on the transition to renewable hydrogen. We developed a dynamic simulation model to explore the development of hydrogen supply with different production technologies in response to projected hydrogen demand towards different climate targets. We conduct a Monte-Carlo based uncertainty analysis to quantify the impact of uncertainty on hydrogen production by different technologies, and on the associated GHG emissions from both the feedstock supply and the production process. The results show that the uncertainty around the cost of electrolyser systems, the capacity factor, and the gas price are the most critical factors affecting the timing of the transition to renewable H2.
In particular, we explore the effect of the volatility of the cost of gas and projected reductions in the capital cost of electrolysers on the risk of gas-based hydrogen projects becoming stranded. With low-cost gas, these assets are replaced by CCS projects with high capture rates. However, when a higher cost of gas and/or favourable conditions for green hydrogen are assumed, all types of blue hydrogen projects become uncompetitive within 10 years of operation. This analysis shows that there is a substantial risk that investments in blue hydrogen will lead to stranded assets.
Presentation title: The impact of electricity retail tariff on hydrogen certification and grid emissions
Abstract: The emission intensity of hydrogen produced by grid electricity depends heavily on electrolysis operational strategies. Here, we examine the trade-offs between least-cost tariff-based electrolysis operations and operations that minimize CO2 emissions or wholesale electricity costs. We conduct a counterfactual analysis across five years of historical data (2017-2021) and five years of modelled data (2022-2026) on wholesale electricity prices and emissions intensities in Australia’s National Electricity Market transitioning to net-zero emissions. We use the Victorian electricity grid as a case study. Modelling shows the present tariff structures, characterized by high daytime volumetric usage and demand charges, overwrite climate and wholesale market signals.
To reduce operational expenses, hydrogen producers will engage in tariff-based operation, which, given Australia's current tariff structure, will result in extended operation during the night to avoid peak usage and demand charges. However, we demonstrate that tariff-based operation will result in suboptimal societal outcomes: first, extensive night-time operation is much more carbon intensive than daytime operation and, second, extensive night-time operation does not take wholesale market signals into consideration.
Compared to tariff-based operations, mitigation-based operations might cut indirect emissions by an average of 33% while increasing yearly power prices by an average of 103% over historical and scenario years (2017-2026). The higher costs are due to a significant increase in demand charges and higher peak usage charges during daytime operation. Spot-based operation results in a 69% rise in yearly power costs. As low wholesale market prices begin to coincide more often with significant renewable energy output (i.e., 2021 onwards), spot-based operation between 2021 and 2026 decreases indirect emissions by an additional 25.2% on average.
Electrolysis operation will influence the intraday and long-run generation and capacity requirements across the electricity system. Providing that preserving the system stability and reliability is of the utmost importance, we recommend a significant tariff reform to unlock wider system benefits. As greater proportions of renewable output are associated with lower spot prices, there appears to be an opportunity for more cost reflectivity to enhance market efficiency and the potential for reducing emissions. To allow for the passing through of wholesale market signals, the timing of peak and off-peak consumption and demand tariff structures must be considered. Reclassifying the midday hours as off-peak and exempt from demand charges would encourage a larger extent of daytime operation by hydrogen producers, which would not only lower wholesale energy costs, but also the indirect emissions of hydrogen production.
University of Adelaide
Presentation title: Green hydrogen from electrocatalytic seawater splitting: a sustainable route towards blue economy
Abstract: With the increasing demand for renewable resources to achieve net zero in 2050, ocean has a pivotal role in the future sustainable environment and economy. Therefore, rational application of marine renewable energy is crucial for rapidly decarbonizing the industrial sector and many chemical transformation processes. Converting renewable energy into hydrogen, a high energy density (∼140 MJ kg−1) fuel with zero-carbon emission, is an ideal choice for intermittent energy storage. In addition, hydrogen can be converted either electronically into fuel cells or thermochemically into chemical reactors to produce synthetic fuels such as methane, methanol, hydrocarbons and oxygenates for fuel exportation.
The price of renewable electricity varies strongly with the location, and particularly the arid coastal regions are often suitable for cheap clean energy production, followed by chemical energy conversion and transportation of the fuels via the ocean. Unfortunately, the areas with intensive renewable energy resources are usually located in coastal zones, including North America, Atacama, Sahara, Arab, Iran, Namib, and Australia, which are scarce freshwater. Hence, electrocatalytic seawater splitting is a desirable strategy for green hydrogen production. However, conventional commercial noble metal benchmarks for hydrogen evolution reaction (HER) are unstable in seawater/alkaline seawater electrolysis and cannot be used. This is because chlorine evolution occurs at the counter electrode, and highly corrosive hypochlorite by-products block the active sites of the noble metal catalysts. Consequently, the development of stable and active electrocatalysts for seawater splitting is of crucial importance for this process.
Herein, we focus on the major challenges and possible solutions for seawater splitting and then evaluate the practical application prospect towards blue economy. As a demonstration, we synthesized a nickel surface nitride encapsulated in a carbon shell (Ni-SN@C) for green hydrogen production from seawater. The unique catalyst combines the desired features of both metallic Ni and nickel nitrides, enabling excellent corrosion resistance and Pt-like HER activity for seawater splitting. The catalyst achieves a current density of 10 mA cm–2 at a small overpotential of 23 mV (ƞ10) and outstanding stability for the HER process in alkaline seawater. Furthermore, when coupled with hydrazine oxidation, a practical two-electrode flow-electrolyser was assembled for hydrogen generation at a current density of 1 A cm–2 with a cell voltage of only 0.7 V.
The University of Sydney
Presentation title: Sustainable technology for greenhouse gas capture, storage, and utilisation
Abstract: The increasing level of greenhouse gases from anthropogenic activity has brought about serious problems such as climate change and environmental pollution. Thus, developing practical technologies to recycle and reuse emitted carbon is profound. Herein, our research focuses on capturing greenhouse gases and their subsequent conversion to industrially valuable products. Specifically, we develop economically feasible technologies for the capture and selective thermal catalytic conversion of CO2 into valuable chemicals such as methanol and ethanol. Meanwhile, based on the market demands, affordable and durable materials are designed and fabricated for capturing and converting CH4, another greenhouse gas, into hydrogen and industrial feedstock. We are also exploring innovative approaches to produce cost-effective fertilizer through sustainable and low-emission methods. Ultimately, we are investigating and unveiling the feasible ways to maximize the carbon credits for greenhouse gas capture, storage, and utilization processes.