Pilani, Oct 16: A faculty member from the Birla Institute of Technology and Science Pilani has co-authored a comprehensive international review published in the journal Applied Energy, mapping the technological, financial, and policy pathways to a carbon-free global energy system.
The review finds that 91% of new utility-scale electricity capacity commissioned worldwide in 2024 was already cheaper than the least expensive new fossil-fuel option, with onshore wind and solar PV costs falling to $0.034 and $0.043 per kilowatt-hour, respectively. Closing the cost-of-capital gap for renewables in emerging economies, the study estimates, could save the global energy transition $31 trillion by 2050 and unlock $54 trillion in cumulative health benefits from cleaner air.
The study, "Pathways towards a carbon-free energy system: Technological advances, policy barriers, and integrated decarbonization strategies", was led by Prof. Hussein Togun, with contributions from researchers across Iraq, India, Saudi Arabia, and Chile, including Prof. Bhupendra K. Sharma of the Department of Mathematics, BITS Pilani.
The study argues that renewable energy has crossed a decisive threshold: it is no longer just an environmental imperative but one of the most economically competitive options for new power generation anywhere in the world.
Prof. Hussein Togun, Thi-Qar Technical College, Southern Technical University, Basrah, Iraq, said,
"Our work moves beyond individual technology assessments to present a holistic, evidence-based roadmap for global energy transition. By linking techno-economic performance with policy design and financial mechanisms, we aim to equip decision-makers with actionable insights to accelerate deployment of renewable energy systems and overcome the structural barriers that currently slow progress."
Cheaper technology, though, won't be enough on its own. Atmospheric CO₂ concentrations crossed 420 parts per million in 2023, the highest in at least three million years, and global temperatures are already up 1.1–1.2°C since pre-industrial times. Even if every current national climate pledge is met in full, the world is still on course for 2.4–2.6°C of warming by 2100, well past what the Paris Agreement calls for.
The study also proposes an Integrated Techno-Economic-Policy-Social framework, a planning model that treats decarbonisation as something that has to happen across technology, finance, governance and society at once, rather than as a straightforward swap of fossil fuels for renewables.
Prof. Bhupendra K. Sharma, Department of Mathematics, BITS Pilani, added,
"This review underscores that achieving a carbon-free future is not merely a technological challenge but a complex socio-technical transition requiring coordinated action across finance, governance, and infrastructure. Our contribution highlights the critical role of mathematical modeling and integrated planning in optimizing generation, storage, and transmission to minimize system costs while ensuring reliability. The findings provide a strategic framework that can guide policymakers, researchers, and industry leaders toward sustainable, secure, and economically viable decarbonization pathways."
One of the paper's key findings concerns the cost of capital: the same solar or wind project can cost three times more to finance in an emerging economy than in a developed one, simply because of political, currency and market risk. Narrowing that gap, from around 10% down to 5% is what drives the transition's single biggest savings, more than technology cost reductions alone could deliver. Even so, reaching net-zero at the required pace will still take roughly $150 trillion in cumulative global investment through mid-century.
The paper draws on case studies of countries that have made real progress, offering a practical playbook for others. Denmark built a world-class offshore wind industry through long-term targets, competitive auctions and coordinated grid planning. Iceland runs an electricity system with an unusually low carbon footprint, powered almost entirely by hydropower and geothermal. South Australia has, on several occasions, generated more renewable electricity than the state actually needed — a useful case study in keeping the grid stable as conventional generators are retired. China's manufacturing scale and India's auction-led rollout show two very different routes emerging economies can take to expand renewables quickly.
Benefits beyond emissions
The gains from decarbonisation go well beyond the climate ledger. Fossil-fuel combustion is linked to roughly 8.7 million premature deaths a year worldwide, which is why cleaner air makes up such a large share of the transition's projected economic benefits. The renewable energy sector already employed about 16.2 million people globally in 2023, a number projected to more than double to 38 million by 2030 under an accelerated transition.
What's still in the way
The obstacles are real. Permitting and development for utility-scale offshore wind can take five to nine years in OECD markets. Transmission capacity hasn't kept pace with generation; in the United States alone, roughly 2,600 GW of mostly wind and solar capacity was sitting in interconnection queues as of 2024, with average wait times running past four years. Supply chains for critical minerals and manufacturing remain heavily concentrated in a handful of countries.
The authors point to grid expansion, anticipatory transmission planning, cross-border interconnection, storage deployment and market redesign as the practical steps needed to absorb rising shares of variable renewable energy. They also argue the transition can't stop at the power sector — it has to reach electrification of end-use sectors, green hydrogen for hard-to-decarbonise industries, sustainable bioenergy, circular-economy practices, and support for workers and communities whose livelihoods are tied to fossil fuels.
Ultimately, the researchers conclude, getting to a carbon-free energy system will take more than better technology. It will require renewable energy, storage and grid infrastructure to be built out together with financial de-risking, institutional reform, stable long-term policy, international cooperation, and transition strategies that don't leave people behind.
