Energy, Sustainability and Society最新文献

Background

PV/diesel microgrids are getting more popular in rural areas of sub-Saharan Africa, where the national grid is often unavailable. Most of the time, for economic purposes, these hybrid PV/diesel power plants in rural areas do not include any storage system. This is the case in the Bilgo village in Burkina Faso, where a PV/diesel microgrid without any battery storage system has been set up. This power plant is composed of three diesel generators operating in parallel (two of 16 kW and one of 24 kW), coupled with a photovoltaic field of 30 kWp. It was observed that for such power plants, the grid management is not always efficient due to constantly fluctuating solar output and loads. This inconsistency in energy output raises the question if integrating battery energy storage systems could improve the grid's performance. While many studies in the literature focus on hybrid energy systems, only a few of them have tackled the optimization of existing and operational systems.

Methods

This study investigated three scenarios based on the existing microgrid's characteristics: conventional standalone diesel generators, PV/diesel without battery storage and PV/diesel with a battery storage system which are the main technologies used for off-grid rural electrification in Burkina Faso. The levelized cost of electricity (LCOE) was used to assess the economic performance of each scenario, and the calculations were made using the HOMER software.

Results

It was found that the best among the scenarios considered is the PV/diesel/battery configuration which has the lowest LCOE of US$ 0.524/kWh. The battery storage system for the optimal configuration has a capacity of 182 kWh with about 8 h of autonomy.

Conclusions

It can be inferred from this study that a storage unit is necessary for an optimal management of a PV/diesel microgrid. Indeed, the storage unit significantly reduces the operating and maintenance costs associated with running diesel generators, as well as the excess electricity. The storage system also allows for a greater reduction in CO₂ emissions compared to systems without storage.

Background

Large-scale renewable energy projects are increasingly being rolled out across rural Kenya, with the government playing a frontline role in attracting energy investors through various state-led and state-centric policies and investment incentives such as feed-in-tariffs and power purchase agreements. While these policies are commendable, and are indeed attracting many private investors, existing studies document how social and environmental justice concerns are often overlooked—sometimes causing local contestations against energy projects. However, to date, there has been less attention given to cases where procedural justice elements (e.g., access to information, access to meaningful participation, access to justice, and respect for local culture) led to a successful land negotiation for energy development without outright conflict. Using a case study in Kenya, this article aims to bridge this gap by showing how a fair application of various elements of procedural justice in land consultation has facilitated the establishment of the Kipeto wind farm. This qualitative research is based on semi-structured interviews that took place from February to March 2023, with a follow-up visit in December the same year, supplemented with review of secondary data sources.

Results

The results indicate that for energy projects to be accommodated in and by communities, access to land must be properly negotiated, particularly with the actual landowners whose livelihoods are most likely to be implicated by the project. Second, local people’s perception of what they regard as a ‘just’ or ‘fair’ process of land consultation constitutes the basis for their acquiescence and compliance.

Conclusion

Ensuring a ‘just’ procedure in land consultation with the actual landowners is a key strategy to avoid conflicts. Land investors, governments, and policy-makers who interface and negotiate with communities must ensure the provision of procedural justice, particularly in contexts where local livelihood is tied to land and where land is individually owned. Although the findings suggest a positive case of wind energy development in Kenya, the project is barely 4 years old; things may change overtime if agreed conditions are not met as specified in the MoU. Therefore, additional follow-up research is needed to ascertain the extent to which both KEL and landowners live up to their promises.

Background

To reduce the effects of climate change, the current fossil-based energy system must transition to a low-carbon system based largely on renewables. In both academic literature and non-academic discourse concerning the energy transition, resilience is frequently mentioned as an additional objective or requirement. Despite its frequent use, resilience is a very malleable term with different meanings in different contexts.

Main text

This paper seeks to identify how resilience is understood in the field of the energy system and whether there are similar aspects in the different ways the term is understood. To this end, we review more than 130 papers for definitions of energy system resilience. In addition, we use different aspects to categorize and examine these. The results paint a diverse picture in terms of the definition and understanding of resilience in the energy system. However, a few definition archetypes can be identified. The first uses a straightforward approach, in which the energy system has one clearly defined equilibrium state. Here, resilience is defined in relation to the response of the energy system to a disturbance and its ability to quickly return to its equilibrium. The second type of resilience allows for different equilibriums, to which a resilient energy system can move after a disruption. Another type of resilience focuses more on the process and the actions of the system in response to disruption. Here, resilience is defined as the ability of the system to adapt and change. In the papers reviewed, we find that the operational definition of resilience often encompasses aspects of different archetypes. This diversity shows that resilience is a versatile concept with different elements.

Conclusions

With this paper, we aim to provide insight into how the understanding of resilience for the energy system differs depending on which aspect of the energy system is studied, and which elements might be necessary for different understandings of resilience. We conclude by providing information and recommendations on the potential usage of the term energy system resilience based on our lessons learned.

Background

Concerns about the sustainability of commercially available batteries have driven the development of post-lithium systems. While previous studies on Magnesium batteries have explored both the potential environmental footprint of battery production and their possible use in stationary applications, their environmental impact in electromobility remains unexplored. This study provides an initial prospective evaluation of the environmental performance of a theoretical Mg–S battery for potential use in electric vehicles (EVs). Utilizing life cycle assessment (LCA) methodology, various scenarios are analyzed and compared to conventional systems. The analysis focuses on potential environmental impacts, including climate change, resource criticality, acidification of the biosphere, and particulate matter emissions.

Results

In the battery pack level, the Magnesium anode and its respective supply chain have been identified as main drivers of environmental burdens. Additional concerns arise from the uneven geographical distribution of Mg production, which leads to dependency on few producers. In terms of resource criticality, the Mg–S battery could carry significant advantages over benchmark systems. A look into the use-phase via theoretical implementation in an electric vehicle (EV) also suggests that the Magnesium based EV could perform on a comparable level to an LIB EV, also outperforming conventional ICEVs in several impact categories.

Conclusions

This study is based on optimistic assumptions, acknowledging several remaining technical challenges for the Mg battery. Consequently, the results are indicative and carry a significant degree of uncertainty. Nonetheless, they suggest that the Mg–S system shows promising environmental sustainability performance, comparable to other reference systems.

Background

Reducing energy consumption and greenhouse gas emissions is a crucial issue in the cassava starch processing industry. In this study, the integrated system combining livestock, cassava cultivation and cassava production in the same area leads to both a zero emission goal and economic efficiency, a typical example of an effective agro-industrial symbiosis. A heat exchange/recovery system was applied including the economizer, heat exchanger tank, biogas tank, and boiler. The economizer attached to the boiler’s chimney transfers heat from exhaust gases for pre-heating feed water entering the boiler. The biogas tank recovers energy from the wastewater of starch production and livestock, and the generated biogas was used as fuel for the boiler.

Results

The energy and exergy efficiency, energy losses, and exergy destruction for the heat recovery system were analyzed. The specific energy consumption was used to evaluate the overall energy efficiency for a cassava starch factory with a capacity of 20 tons/day. The results show that there is a high potential to recycle waste into energy in the cassava starch industry. The total energy saving and reduced greenhouse gas emissions per year of the cassava starch factory were 0.054%/year and 123,564 kgCO₂/per year, respectively.

Conclusions

Cassava starch factories can save energy and reduce emissions when applying a heat recovery system in the integrated agro-industrial system. Excess heat from the production was used for evaporating (removal of) NH₃ in wastewater flow from the biogas tank, and for heating the biogas system to enhance the efficiency of methane production. A biochar filter was attached to the economizer for adsorption of released ammonium, and the biochar after adsorption was combined with sludge from the biogas tank to produce a solid biofertilizer.

Background

New regulations and market conditions in Germany affect the profitability of biomethane upgrading as a repowering option for existing biogas plants following on-site CHP utilization. These conditions present trade-off challenges between higher sustainability requirements, maintaining production capacity and new revenue opportunities. Optimization methods, such as linear programming (LP), are essential for determining the ideal substrate mixture and profitable solutions amidst multiple market conditions, plant-specific process constraints, and substrate properties.

Methods

We updated a substrate mixture optimization model within an assessment framework for the repowering of existing biogas plants (BGPs), which focuses on the operator’s perspective. By integrating multiple German biomethane markets for various BGPs, we assessed changes in the substrate mixture, GHG emissions, contribution margins, and constraint parameters to derive conclusions for operators and future framework design.

Results

Integrating market revenues and constraints can increase contribution margins by 12–55%. Additional gains can be achieved by considering multiple markets simultaneously but limited to a few BGPs. The plant-specific LP solution space and used benchmark market are decisive. The former limits the potential of high substrate-specific contribution margins, which has a significantly higher impact than the relation between plant-specific characteristics and process constraints. The advanced fuel market is currently the lead market for biomethane, incentivizing GHG-emission extensive substrates, decreasing gas production and GHG emissions but increasing levelized cost of energy (LCOE) and partially CO₂ abatement costs.

Conclusions

The key to improve profitability and to supply an increasing biomethane demand while fulfilling new requirements is a large LP solution space. Increasing market options, substrate availability, and digestion system capacity achieve this on the operator’s side. Policy makers could reduce normative requirements such as the maize cap or double counting of advanced fuels and favor high but uniform GHG requirements. Operators can prepare robustly for the future substrate mixture by adding digester volume and pre-treatment tech, ensuring long-term and diverse substrate availability, and contracts with flexible components. Although current market conditions can improve specific GHG emissions, they do not necessarily increase manure usage when other options, such as straw, are viable. Other regulatory support systems will be required to do so.

Background

Article 12 of the Paris Agreement summons the signing parties to co-operate in improving the education of their citizens on climate change and related matters. The article thereby acknowledges the importance of citizens’ support and understanding of climate change and needed measures to fight climate change. This work aims to inform European citizens on how climate change-related policies affect the power sector in Europe. For this purpose, a serious game, based on sound principles of energy systems analysis, has been developed to allow players to explore how key policy decisions affect capacity mix, investment needs, and electricity costs.

Results

The game is based on more than 1700 scenarios run through an open-source and accessible, yet technologically detailed, myopic energy system optimisation model for the electricity supply in the EU27 + 3. The game allows the user to take the role of a decision-maker and make decisions in 2020, 2030, and 2040 regarding the usage of CCS, biomass imports, cross-border electricity transmission and the pace of emission reductions. The user is then presented with economic, social, and environmental impacts of these choices. These impacts are, for example, measured and illustrated in the development of accumulated CO₂ emissions per capita, levelised cost of electricity, and investment need per citizen.

Conclusion

The Power Decisions Game provides a first-of-its-kind open-source infrastructure that allows non-modellers to explore the impact of key decisions and preferences on the design of the future European power system. Furthermore, it provides insights on the consequences of short-sighted decision making. The game can be used to facilitate policy-science discussions.