**Preface to "Secure and Sustainable Energy System"**

Alarming reports from the Intergovernmental Panel on Climate Change (IPCC) have shown that climate change urgently needs to be addressed, and in 2015, United Nations (UN) members agreed to keep the global temperature increase below 2°C through their Nationally Determined Contribution. The UN also added 'Climate Action' to their Sustainable Development Goals (SDGs). However, IPCC and the UN Environment Programme (UNEP) reports highlight that further actions must be taken to fulfil these SDGs. Increasing the share of sustainable energy resources in the energy baskets would not only reduce Green House Gas (GHG) emissions—in line with the SDGs and the Paris Agreement—but would also increase energy security.

Several developed and developing economies are still adhering to pro-fossil fuel energy policies. The extra GHG generated by new coal-fired power plants could more than wipe out any reductions in emissions made by other nations. One of the most significant barriers to developing a sustainable energy system is the low level of investment. The lack of long-term financing, the low rate of return, the existence of various risks, and the lack of capacity of market players are major challenges to developing sustainable energy systems.

With this background, this Special Issue aims to contribute to the climate actions which called for the need to address GHG Emissions, keeping global warming to well below 2°C through various means, including accelerating renewables, clean fuels, and clean technologies into the entire energy system. As long as fossil fuels (coal, gas and oil) are still used in the foreseeable future, it is vital to ensure that they are used cleanly through abated technologies. Financing clean and energy transition technologies is vital to ensure the smooth transition towards net zero emission by 2050. This Special Issue collected 17 high-quality empirical studies that assess the challenges of developing secure and sustainable energy systems and provide practical policy recommendations. The editors wish to thank the Economic Research Institute for ASEAN and East Asia (ERIA) for funding several papers that were published in this Special Issue.

> **Farhad Taghizadeh-Hesary and Han Phoumin** *Editors*
