An emerging problem associated with the increased global demand for electric vehicles (EVs) is the post-use of lithium-ion batteries installed in them. Discarded batteries maintain 70–80% of their performance; thus, they are highly valuable recycling resources. Accordingly, technologies that complement the intermittency of renewable energy by integrating discarded EV batteries into battery energy storage systems (BESSs) are receiving attention. Here, the economic feasibility of a residential solar photovoltaic (PV) + reused BESS (RBESS) integrated system in three emerging countries (Philippines, Indonesia, and Vietnam) was analyzed by comparing its performance with that of diesel power generation and central grid-supplied power. The proposed system had a higher economic feasibility than diesel power generation (55.9% lower LCOE) but a lower economic feasibility than the central grid-supplied power (282.7% higher LCOE) in all three countries. Additionally, we conducted a sensitivity analysis by incorporating the investment cost, government subsidy, and social cost of greenhouse gas emissions. In conclusion, the Philippines is the best country for grid parity with the integrated system, following Indonesia and Vietnam. This study examined both the economic and social benefits of the proposed system as a countermeasure to climate change and the virtuous resource cycle.

This study investigates the factors that affect the investment environment of the renewable energy industry in emerging countries, and quantifies them to derive relative priorities, drawing on the Vietnamese solar market as a critical case. Vietnam's solar photovoltaic (PV) market was exposed to various adverse policy situations during 2017–2019. The priorities of the determinant factors were derived using analytic hierarchy process analysis, based on a survey of 20 energy experts. The priority of the factors in Level 1 include, in descending order, policies, legal framework, profitability, ease of access to finance, infrastructure, and external factors. The top five of the 29 important factors in Level 2 are level of policy implementation, policy consistency (predictability), feed-in-tariff price, incentives and subsidies for foreign (direct) investment in solar PV, fruitage remittance, and transmission/distribution lines. We demonstrate that the active establishment and implementation of policies is crucial for the development of the renewable energy market. The improvement of the grid infrastructure and measures for system integration should be supported in accordance with solar power deployment. Therefore, actively engaging the interests of various stakeholders comprehensively and in a balanced manner during policymaking can be decisive in supporting stable market growth, facilitated by partnerships between local developers and international investors.