Systemwide energy return on investment in a sustainable transition towards net zero power systems.

The Glasgow Climate Pact articulated the vital importance of renewables in reducing emissions on the way to net-zero pledges. During the power sector transition, foreseeing conditions affecting the plausibility of pathway options is crucial for specifying an optimal system development strategy. This study examines the net energy performance of nine decarbonisation global energy transition scenarios until 2050 by applying a newly developed systemwide energy return on investment (EROI) model. All scenarios result in an EROI value above the upper limit of the net energy cliff, expected to be around 10. EROI trends heavily depend on transition paths. Once achieving higher renewable energy shares begin requiring significant enabling technologies, EROI continually declines as the shares increase. Shortening the transition period leads to a sharper declining of EROI, which stabilises after achieving 100% renewables. The vulnerability arising from natural gas and oil depletions may have worst impact on EROI of fossil fuels dominated systems.

Photovoltaics at multi-terawatt scale: Waiting is not an option.

25% annual PV growth is possible over the next decade.

Climate and biodiversity impacts of low-density polyethylene production from CO2 and electricity in comparison to bio-based polyethylene.

Plastics are essential materials for modern societies, but their production contributes to significant environmental issues. Power-to-X processes could produce plastics from captured CO2 and hydrogen with renewable electricity, but these technologies may also face challenges from environmental perspective. This paper focuses on environmental sustainability assessment of CO2-based low-density polyethylene (LDPE) compared to bio-based LDPE. Life cycle assessment has been applied to study climate impacts and land use related biodiversity impacts of different plastic production scenarios. According to the climate impact results, the carbon footprint of the produced plastic can be negative if the energy used is from wind, solar, or bioenergy and the carbon captured within the plastic is considered. In terms of biodiversity, land-use related biodiversity impacts seem to be lower from CO2-based polyethylene compared to sugarcane-based polyethylene. Forest biomass use for heat production in CO2-based polyethylene poses a risk to significantly increase biodiversity impacts. Taken together, these results suggest that CO2-based LDPE produced with renewable electricity could reduce biodiversity impacts over 96 % while carbon footprint seems to be 6.5 % higher when compared to sugarcane-based polyethylene.

Contextualizing the scope, scale, and speed of energy pathways toward sustainable development in Africa.

Faced with interrelated challenges of climate change and energy crises, Africa's future energy system orientation could be steered toward sustainable development. In this study, we contextualized diverging fossil fuels-dominated and renewable energy-based pathways toward sustainable development in Africa. A novel and sophisticated techno-economic energy modeling tool is used to describe the scope of the pathways in high geo-spatial and full hourly resolution for Africa covering the entire energy system. This study demonstrates that a renewable energy pathway is not only climate-compatible, but also delivers a lower cost system structure than alternative pathways. Our results show that Africa can leapfrog carbonization by using its low-cost renewable electricity and green hydrogen. Furthermore, Africa can become a self-sufficient green economy and an exporter of green fuels. Notably, solar photovoltaic-battery hybrid systems and electrolyzers are instrumental in achieving carbon-neutrality in Africa. This research presents a "true-zero emission" pathway for Africa.

The role of renewables for rapid transitioning of the power sector across states in India.

Recent events like heatwaves and abnormal rainfall are a glimpse of the devastating effects of human induced climate change. No country is immune to its effects, but a developing country like India is particularly vulnerable. This research, for the individual states of India, explores the technical feasibility and economic viability of a renewable transition pathway for the power sector. Based on the assumptions of this study, we show that a renewables-based power system by 2050 is lower in cost than the current  coal dominated system, has zero greenhouse gas emissions and provides reliable electricity to around 1.7 billion people. Electricity generation will be based on solar PV, wind energy, and hydropower, while batteries and multi-fuel reciprocating internal combustion engines based on synthetic fuels provide the required flexibility to the power system. This transition would address  multiple imperatives: affordability, accessibility, and sustainability without compromising economic growth.

Assessment of lithium criticality in the global energy transition and addressing policy gaps in transportation.

The forthcoming global energy transition requires a shift to new and renewable technologies, which increase the demand for related materials. This study investigates the long-term availability of lithium (Li) in the event of significant demand growth of rechargeable lithium-ion batteries for supplying the power and transport sectors with very-high shares of renewable energy. A comprehensive assessment that uses 18 scenarios, created by combining 8 demand related variations with 4 supply conditions, were performed. Here this study shows that Li is critical to achieve a sustainable energy transition. The achievement of a balanced Li supply and demand throughout this century depends on the presence of well-established recycling systems, achievement of vehicle-to-grid integration, and realisation of transportation services with lower Li intensity. As a result, it is very important to achieve a concerted global effort to enforce a mix of policy goals identified in this study.

Assessing the potential for renewable energy powered desalination for the global irrigation sector.

By 2050, it is estimated that the annual cereal production would need to increase by about 140% and total global food production increase by 70%. Meanwhile, total water withdrawals for irrigation are projected to increase by 11%. In contrast, poor management of existing water resources, pollution and climate change has resulted in limited freshwater resources. The aim of this paper is to assess how improved irrigation efficiency and renewable energy based desalination maybe used to secure future water supplies for the growth of rice, wheat and maize. The efficiencies of the existing irrigation sites were obtained and improved based on a logistic curve. The growth was projected such that by 2050, all existing irrigation sites would have an efficiency of 90%. The new irrigation efficiencies were used to obtain the reduced irrigation demand for the years 2030 and 2050. The desalination demand was estimated and an energy system model used to optimise the corresponding renewable energy based power system. It was found that improving the average irrigation efficiency to 60% by 2030, led to a 64% reduction in total desalination demand. Similarly, an improvement towards 90% irrigation efficiency, by 2050, translates to an 80% reduction in global desalination demand. In 2030, the total water cost is mostly within 0.7 €/m3-2 €/m3 including water transportation costs. Literature reports that farmers may be willing to pay up to 0.63 €/m3 for their irrigation water. The global range in 2050 is estimated to be 0.45 €/m3-1.7 €/m3 reflecting the lower system costs in 2050. The above results indicate that as conventional water prices increase, renewable energy based seawater reverse osmosis desalination, offers a cost effective water supply for the irrigation sector. Adoption of high efficiency irrigation systems alleviate water stress and can eliminate need for additional water supply.

Radical transformation pathway towards sustainable electricity via evolutionary steps.

A transition towards long-term sustainability in global energy systems based on renewable energy resources can mitigate several growing threats to human society simultaneously: greenhouse gas emissions, human-induced climate deviations, and the exceeding of critical planetary boundaries. However, the optimal structure of future systems and potential transition pathways are still open questions. This research describes a global, 100% renewable electricity system, which can be achieved by 2050, and the steps required to enable a realistic transition that prevents societal disruption. Modelling results show that a carbon neutral electricity system can be built in all regions of the world in an economically feasible manner. This radical transformation will require steady but evolutionary changes for the next 35 years, and will lead to sustainable and affordable power supply globally.

Electricity system based on 100% renewable energy for India and SAARC.

The developing region of SAARC (South Asian Association for Regional Cooperation) is home to a large number of people living below the poverty line. In future, providing affordable, universally accessible, reliable, low to zero carbon electricity in this region will be the main aim. A cost optimal 100% renewable energy system is simulated for SAARC for the year 2030 on an hourly resolved basis. The region was divided into 16 sub-regions and three different scenarios were set up based on the level of high voltage direct current (HVDC) grid connections. The results obtained for a total system levelised cost of electricity (LCOE) showed a decrease from 71.6 €/MWh in a decentralized to 67.2 €/MWh for a centralized grid connected scenario. An additional scenario was simulated to show the benefits of integrating industrial gas production and seawater reverse osmosis desalination demand, and showed the system cost decreased by 5% and total electricity generation decreased by 1%. The results show that a 100% renewable energy system could be a reality in the SAARC region with the cost assumptions used in this research and it may be more cost competitive than nuclear and fossil carbon capture and storage (CCS) alternatives. One of the limitations of this study is the cost of land for installation of renewables which is not included in the LCOE calculations, but regarded as a minor contribution.

Hydro, wind and solar power as a base for a 100% renewable energy supply for South and Central America.

Power systems for South and Central America based on 100% renewable energy (RE) in the year 2030 were calculated for the first time using an hourly resolved energy model. The region was subdivided into 15 sub-regions. Four different scenarios were considered: three according to different high voltage direct current (HVDC) transmission grid development levels (region, country, area-wide) and one integrated scenario that considers water desalination and industrial gas demand supplied by synthetic natural gas via power-to-gas (PtG). RE is not only able to cover 1813 TWh of estimated electricity demand of the area in 2030 but also able to generate the electricity needed to fulfil 3.9 billion m3 of water desalination and 640 TWhLHV of synthetic natural gas demand. Existing hydro dams can be used as virtual batteries for solar and wind electricity storage, diminishing the role of storage technologies. The results for total levelized cost of electricity (LCOE) are decreased from 62 €/MWh for a highly decentralized to 56 €/MWh for a highly centralized grid scenario (currency value of the year 2015). For the integrated scenario, the levelized cost of gas (LCOG) and the levelized cost of water (LCOW) are 95 €/MWhLHV and 0.91 €/m3, respectively. A reduction of 8% in total cost and 5% in electricity generation was achieved when integrating desalination and power-to-gas into the system.