Clean energy technological innovations are widely acknowledged as a prerequisite to achieving ambitious long-term energy and climate targets. However, the optimal speed of their adoption has been parsimoniously studied in the literature. This study seeks to identify the optimal intensity of moving to a green hydrogen electricity sector in Greece, using the OSeMOSYS energy modeling framework. Green hydrogen policies are evaluated, first, on the basis of their robustness against uncertainty and, afterwards, against conflicting performance criteria and for different decision-making profiles towards risk, by applying the VIKOR and TOPSIS multi-criteria decision aid methods. Although our analysis focuses exclusively on the power sector and compares different rates of hydrogen penetration compared to a business-as-usual case without considering other game-changing innovations (such as other types of storage or carbon capture and storage), we find that a national transition to a green hydrogen economy can support Greece in potentially cutting at least 16 MtCO2 while stimulating investments of EUR 10–13 bn. over 2030–2050.

The Open Source Spatial Electrifcation Tool (OnSSET) is extended to provide a long-term geospatial electrifcationanalysis of Ethiopia, focusing on the role of grid- and of-grid technologies to increase residential electricity access underdiferent scenarios. Furthermore, the model explores issues of compatibility between the electricity supply technologiesover time. Six potential scenarios towards universal access to electricity in the country are examined based on threepathways; the Ambition pathway sees high demand growth and universal access achieved by 2025, the Slow Down pathway follows a lower demand growth with a slower electrifcation rate and with a higher share of of-grid technologies,and the Big Business pathway prioritizes grid electricity frst for the industrial sector, leading to slower residential electrifcation. The results show a large focus on grid extension and stand-alone PV deployment for least-cost electrifcationin case of low grid-generation costs and uninhibited grid expansion. However, in case of a slower grid rollout rate andhigh demand growth, a more dynamic evolution of the supply system is seen, where mini-grids play an important rolein transitional electrifcation. Similarly, in the case where grid electricity generation comes at a higher cost, mini-gridsprove to be cost-competitive with the centralized grid in many areas. Finally, we also show that transitional mini-grids,which are later incorporated into the centralized grid, risk increasing the investments signifcantly during the periodswhen these are integrated and mini-grid standards are not successfully implemented. In all cases, existing barriers todecentralized technologies must be removed to ensure of-grid technologies are deployed and potentially integratedwith the centralized grid as needed.

A significant obstacle to the incorporation of Nexus considerations in planning and policy design is the understanding and acknowledgement of cross-sectoral interdependencies. This chapter explores the importance of disseminating knowledge of the Nexus among key actors from policy, business and civil society, and in formal education contexts. Examples from capacity development activities and Nexus dialogues linked to the implementation of the Climate, Land, Energy and Water systems (CLEWs) framework are presented. Insights from the latter, as well as other initiatives with similar scope of action, are distilled to forward the importance of learning in such an approach. Additionally, the chapter highlights the main aspects to take into account when promoting these types of activities in new Nexus contexts.

Energy system modeling can be used to develop internally consistent quantified scenarios. These provide key insights needed to mobilise finance, understand market development, infrastructure deployment and the associated role of institutions, and generally support improved policymaking. However, access to data is often a barrier to starting energy system modeling, especially in developing countries, thereby causing delays to decision making. Therefore, this article provides data that can be used to create a simple zero-order energy system model for a range of developing countries in Africa, East Asia, and South America, which can act as a starting point for further model development and scenario analysis. The data are collected entirely from publicly available and accessible sources, including the websites and databases of international organisations, journal articles, and existing modeling studies. This means that the datasets can be easily updated based on the latest available information or more detailed and accurate local data. As an example, these data were also used to calibrate a simple energy system model for Kenya using the Open Source Energy Modeling System (OSeMOSYS) and three stylized scenarios (Fossil Future, Least Cost and Net Zero by 2050) for 2020-2050. The assumptions used and the results of these scenarios are presented in the appendix as an illustrative example of what can be done with these data. This simple model can be adapted and further developed by in-country analysts and academics, providing a platform for future work.

Strategic energy planning to achieve universal electricity access and meet the future energy needs of African nations is essential to formulate effective policy measures for climate change mitigation and adaptation. Africa can not afford a cost-prohibiting green energy transition to achieve United Nations Sustainable Development Goal 7. In this study, I employ open-access energy models, enhanced with geospatial data, to identify least-cost power generation investment options for forty-eight African nations. Different levels of electricity consumption per capita and costs of renewables are considered across four scenarios. According to the analysis, to achieve universal electricity access by 2030 in Africa, the power generation capacity needs to increase between 211GW-302GW, depending on electricity consumption levels and the cost of renewables considered, leading electricity generation to rise between 6,221PJ- 7,527PJ by 2030. Higher electricity generation levels lead to higher penetration of fossil fuel technologies in the power mix of Africa. Natural gas will be the dominant fossil fuel source by 2030, while the decreasing costs of renewables will lead solar to overtake hydropower. To meet the same electricity demand levels, decreasing the cost of renewables can enable a less carbon-intensive power system, although higher capacity is also needed. However, Africa is still hard to achieve its green revolution. Depending on electricity consumption levels and costs of renewables considered, grid-connected technologies are estimated to supply 85%-90% of total electricity generated in Africa in 2030, mini-grid technologies 1%-6%, and stand-alone technologies 8%-11%. Off-grid solar and hybrid mini-grid solar technologies are essential in electrifying residential areas. Higher penetration of renewable energy sources in the energy mix creates local jobs and increases cost-efficiency. The analysis demonstrates that 6.9 million to 9.6 million direct jobs, depending on the policies and renewable development levels, can be created in Africa by expanding the power sector from 2020 to 2030 across the supply chain. While increasing electricity consumption levels in Africa leads to higher total system costs, it is also estimated to create more jobs, fostering political and societal stability. Finally, the decreasing costs of renewables could further increase the penetration of renewables in the energy mix, leading to an even higher number of jobs.

The 2030 Agenda for Sustainable Development calls for the achievement of universal access to affordable, reli-able, sustainable and modern energy for all. To fulfil this ambition, least developed countries need to mobilise enormous investments in a short amount of time. Deciding the extent, priority and timing of these investments is a hard task, for which many governments currently lack internal resources. Development Partners are supporting these efforts by contributing to the national energy planning ecosystems. In this comment, we focus on the role of Development Partners. We reflect on the approach to support strategic energy planning they took so far and on how they may improve it to further - and more effectively -support countries where de-mand arises. We take the example of one recent capacity development effort in Sierra Leone. We highlight that academia is one pillar of the national energy planning ecosystem, and conclude that academic partnerships play a critical role in changing the paradigm from short-term capacity transfer to a more sustainable capacity development. Formalised academic partnerships may increase the retention of capacity and support na-tional planning ecosystems in becoming more self-sustained. Increased knowledge sharing on best open prac-tices for energy data and model infrastructure may further support the ecosystem by improving the communication between academia, government and utilities.

Africa's economic and population growth prospects are likely to increase energy and water demands. This quantitative study shows that energy decarbonisation pathways reduce water withdrawals (WWs) and water consumption (WC) relative to the baseline scenario. However, the more aggressive decarbonisation pathway (1.5 degrees C) leads to higher overall WWs than the 2.0 degrees C scenario but lower WC levels by 2065. By 2065, investments in low-carbon energy infrastructure increase annual WWs from 1% (52 bcm) in the 2.0 degrees C to 2% (85 bcm) in the 1.5 degrees C scenarios of total renewable water resources in Africa compared to 3% (159 bcm) in the baseline scenario with lower final energy demands in the mitigation scenarios. WC decreases from 1.2 bcm in the 2.0 degrees C to 1 bcm in the 1.5 degrees C scenario, compared to 2.2 bcm in the baseline scenario by 2065, due to the lower water intensity of the low-carbon energy systems. To meet the 1.5 degrees C pathway, the energy sector requires a higher WW than the 2.0 degrees C scenario, both in total and per unit of final energy. Overall, these findings demonstrate the crucial role of integrated water-energy planning, and the need for joined-up carbon policy and water resources management for the continent to achieve climate-compatible growth.

Population growth, urbanization and economic development drive the use of resources. Securing access to essential services such as energy, water, and food, while achieving sustainable development, require that policy and planning processes follow an integrated approach. The 'Climate-, Land-, Energy- and Water-systems' (CLEWs) framework assists the exploration of interactions between (and within) CLEW systems via quantitative means. The approach was first introduced by the International Atomic Energy Agency to conduct an integrated systems analysis of a biofuel chain. The framework assists the exploration of interactions between (and within) CLEW systems via quantitative means. Its multi-institutional application to the case of Mauritius in 2012 initiated the deployment of the framework. A vast number of completed and ongoing applications of CLEWs span different spatial and temporal scales, discussing two or more resource interactions under different political contexts. Also, the studies vary in purpose. This shapes the methods that support CLEWs-type analyses. In this paper, we detail the main steps of the CLEWs framework in perspective to its application over the years. We summarise and compare key applications, both published in the scientific literature, as working papers and reports by international organizations. We discuss differences in terms of geographic scope, purpose, interactions represented, analytical approach and stakeholder involvement. In addition, we review other assessments, which contributed to the advancement of the CLEWs framework. The paper delivers recommendations for the future development of the framework, as well as keys to success in this type of evaluations.

Paraguay's power system is based entirely on hydropower. It serves as the largest net electricity exporter in Latin America. Nonetheless, the country´s electricity consumption per capita is one of the lowest in the world and the transmission and distribution network has one of the highest losses in Latin America. This paper presents an electricity expansion investment outlook (2018–2040) for Paraguay using OSeMOSYS, analyzing three electricity demand scenarios under different electricity export prices to Brazil. The study identifies the least-cost power generation mix, future investments and the financial requirements to meet the needs of different demand scenarios. We find that Paraguay will need to invest in hydropower plants, by mainly expanding the capacity of Yacyreta to cover its electricity needs and sustain national electricity exports levels. In the High demand scenario, where the electricity demand could approximately double by 2040, the country's overall electricity exports decrease by 50% compared to the Reference scenario. Based on the different scenarios examined, the government spends approximately 18.3–31.2 billion USD on power plant investments for the period 2018–2040 to cover future electricity demand. The findings could be useful in supporting decision-making concerning socio-economic development pathways in the country.

Ethiopia is a low-income country, with low electricity access (45%) and an inefficient power transmission network. The government aims to achieve universal access and become an electricity exporter in the region by 2025. This study provides an invaluable perspective on different aspects of Ethiopia's energy transition, focusing on achieving universal access and covering the country's electricity needs during 2015-2065. We co-developed and investigated three scenarios to examine the policy and technology levels available to the government to meet their national priorities. To conduct this analysis, we soft-linked OnSSET, a modelling tool used for geospatial analysis, with OSeMOSYS, a cost-optimization modelling tool used for medium to long-run energy planning. Our results show that the country needs to diversify its power generation system to achieve universal access and cover its future electricity needs by increasing its overall carbon dioxide emissions and fully exploit hydropower. With the aim of achieving universal access by 2025, the newly electrified population is supplied primarily by the grid (65%), followed by stand-alone (32%) technologies. Similarly, until 2065, most of the electrified people by 2025 will continue to be grid-connected (99%). The country's exports will increase to 17 TWh by 2065, up from 832 GWh in 2015, leading to a cumulative rise in electricity export revenues of 184 billion USD.