The growing field of macro-energy systems (MES) brings together the interdisciplinary community of researchers studying the equitable and low-carbon future of humanity’s energy systems. As MES matures as a community of scholars, a coherent consensus about the key challenges and future directions of the field can be lacking. This paper is a response to this need. In this paper, we first discuss the primary critiques of model-based MES research that have emerged because MES was proposed as a way to unify related interdisciplinary research. We discuss these critiques and current efforts to address them by the coalescing MES community. We then outline future directions for growth motivated by these critiques. These research priorities include both best practices for the community and methodological improvements.
Fusion could be a part of future decarbonized electricity systems, but it will need to compete with other technologies. In particular, pulsed tokamak plants have a unique operational mode, and evaluating which characteristics make them economically competitive can help select between design pathways. Using a capacity expansion and operations model, we determined cost thresholds for pulsed tokamaks to reach a range of penetration levels in a future decarbonized US Eastern Interconnection. The required capital cost to reach a fusion capacity of 100 GW varied from $2,700 to $7,500 kW−1, and the equilibrium penetration increases rapidly with decreasing cost. The value per unit power capacity depends on the variable operational cost and on the cost of its competition, particularly fission, much more than on the pulse cycle parameters. These findings can therefore provide initial cost targets for fusion more generally in the United States.
The REPEAT Project’s revised analysis examines the climate and energy impacts of legislation passed by the 117th Congress, focusing on the Inflation Reduction Act of 2022 and the Infrastructure Investment and Jobs Act of 2021. Updated with the latest data from 2022, the analysis includes enhanced information on methane emissions in the oil, gas, agriculture, and forestry sectors. It presents three ‘Current Policies’ scenarios—’Conservative’, ‘Mid-range’, and ‘Optimistic’—to reflect uncertainties in law effectiveness and supply chain constraints. Additionally, it compares two benchmark scenarios: a ‘Frozen Policies’ scenario based on early 2021 policies, and a ‘Net-Zero Pathway’ scenario aligning with President Biden’s climate goals. The report covers greenhouse gas emissions, clean energy, electric vehicle deployment, fossil fuel use, and their impacts on energy costs, investment, employment, air pollution, and public health. The findings, which are approximate due to uncertainties, are updated regularly and have not been peer-reviewed.
The Inflation Reduction Act (IRA) notably reduces costs for utility-scale solar and wind projects in the U.S. by expanding tax credits. Utility-scale solar and wind costs can decrease by about 60% with the PTC bonus rate, and offshore wind costs by around 20%. The 45X Tax Credit makes U.S.-manufactured solar and wind components more competitive than imports, potentially cutting solar module costs by over 30%. This legislation could generate significant job growth in the renewable sector, with an estimated 1.3 million additional solar jobs and 250,000 wind jobs by 2035. Overall, utility-scale solar and wind jobs could reach 1.7 million and 520,000 respectively. The IRA will also increase wages in these sectors and boost the demand for construction materials like aluminum, cement, and steel, with demands in some cases exceeding current U.S. consumption and production levels by 2035.
Recent research shows that the ‘Three Pillars’ standard (new supply, deliverability, hourly matching) is crucial for accurate carbon accounting in U.S.-subsidized electrolytic hydrogen production to prevent excess emissions. Some believe this standard’s costs could negate the $3/kg clean hydrogen tax credit from the Inflation Reduction Act (IRA), threatening the U.S. clean hydrogen industry. Others see the standard as essential to meet IRA’s emission goals, but worry it may hinder rapid electrolyzer deployment, necessary for long-term emission reductions. This perceived dilemma assumes that the ‘Three Pillars’ make early grid-connected hydrogen projects economically unfeasible. However, as outlined in this memo, such concerns are unsubstantiated, indicating that implementing rigorous emissions standards doesn’t necessarily compromise the viability of early hydrogen projects.
The REPEAT Project has finalized its analysis of the climate and energy impacts of key legislation from the 117th Congress, focusing on the Inflation Reduction Act of 2022 (IRA) and the Infrastructure Investment and Jobs Act of 2021 (IIJA). This report, updated with the latest data from 2021, includes enhanced evaluations of methane emissions in the oil and gas sector and opportunities for emission reduction in agriculture and forestry. The analysis introduces three ‘Current Policies’ scenarios—’Conservative’, ‘Mid-range’, and ‘Optimistic’—to account for uncertainties in IRA’s effectiveness and potential supply chain constraints. Additionally, it compares a ‘Frozen Policies’ scenario, reflecting laws as of early 2021, and a ‘Net-Zero Pathway’ scenario, aligning with President Biden’s goals to significantly reduce U.S. greenhouse gas emissions by 2030 and achieve net-zero by 2050. This brief report previews the final findings on these laws’ impact on the U.S.’s greenhouse gas emissions trajectory.
The U.S. introduced a production tax credit (PTC) to encourage low-carbon hydrogen production, essential for a net-zero carbon economy. Hydrogen produced via electrolysis qualifies for the full subsidy if using carbon-free electricity, but may not if the electricity mix includes emitting resources. This study explores the effects of grid-connected electrolysis on the western U.S. power sector through 2030 under various clean hydrogen PTC implementations. It finds that subsidized grid-connected hydrogen production could induce higher emissions than fossil-based methods. Minimizing emissions requires grid-based hydrogen producers to match their electricity consumption hourly with clean, deliverable generation, effectively mirroring behind-the-meter carbon-free generation. Despite this, indirect emissions from competition for clean resources persist. The study suggests that stringent hourly matching standards consistently outperform other methods, with added costs less than $1 per kg and potentially negligible if clean, firm electricity resources are available. This approach addresses indirect emissions without significantly increasing production costs.
This study examines the environmental and economic viability of different fuel production methods as part of U.S. net-zero greenhouse gas emission strategies. It conducts lifecycle assessments for hydrogen (H2), synthetic natural gas (SNG), and Fischer-Tropsch liquid (FTL) fuels, considering three sources: biomass with carbon capture and storage (CCS), natural gas with CCS, and renewable electricity. The study finds that hydrogen production, especially from biomass with CCS, is more cost-effective and efficient in reducing greenhouse gas emissions than FTL and SNG. Sensitivity analysis reveals the significant impact of capital costs and capacity factors on the levelized costs of carbon mitigation (LCCM), with natural gas-based processes being particularly sensitive to feedstock price changes. Biomass-based fuels with CCS show the highest potential for carbon mitigation and become increasingly cost-effective at higher carbon pricing. These results emphasize the critical importance of biomass-based hydrogen production with CCS in achieving U.S. net-zero emissions goals.
Europe’s reliance on Russian natural gas, highlighted by the Russian-Ukraine conflict, poses a significant energy security risk. To address this, Europe must urgently reduce its dependency on Russian fossil fuels through demand reduction, alternative energy sources, and rapid clean energy infrastructure development. The European Commission’s REPowerEU plan targets a two-thirds reduction in Russian gas imports by 2022 end, but stops short of total elimination until 2027 and lacks a detailed policy analysis for immediate energy security. A new report offers detailed strategies for the EU and the UK to quickly sever Russian gas dependence. It suggests enhancing the REPowerEU plan with additional gas reductions for electricity and adjusting gas storage targets. This report, aligning with other studies, outlines immediate strategies for a Russian gas embargo, assessing policy implications and climate commitments. Its integrated electricity and gas models confirm the feasibility of eliminating Russian gas dependency while maintaining supply security.
In electricity systems with high variable renewable energy, flexible operations of natural gas combined cycle (NGCC) power plants with carbon capture and sequestration (CCS) can enhance economic value. A new model efficiently represents these flexible NGCC-CCS plants. It dissects plants into subcomponents with linear constraints for energy and mass balances, and simplifies complex unit commitment (UC) constraints. This study explores linear relaxation of discrete UC variables with a generator clustering method, integrating this into a power system model. A case study shows the hourly operations of NGCC-CCS components and their impacts on environmental and economic performance. The findings reveal that linear relaxation with generator clustering significantly speeds up runtime (18–527 times faster) and minimizes errors. The model demonstrates that flexible NGCC-CCS plants reduce power system operating costs by adjusting output during peak demand, indicating their increased relevance in future grids dominated by renewable resources.