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Abstract High-temperature heat pumps (HTHPs) based on vapour compression can be used for industrial low-grade waste heat valorisation, which can aid in mitigating climate change. Currently, the performance of HTHPs operating at high-temperatures lifts is limited; therefore, advanced configurations become an opportunity for their utilisation. This paper presents an HTHP cascade with configurations of internal heat exchangers (IHXs) that uses low GWP refrigerants in both high-stage (HS) (HCFO-1233zd(E), HFO-1336mzz(Z), HCFO-1224yd(Z), and pentane) and low-stage (LS) (HFO-1234yf, HFO-1234ze(E), butane, isobutane, and propane) cycles. Prior to the analysis and presentation of results, an optimisation of the operating conditions is performed based on intermediate temperature and IHX effectiveness in both stage cycles. Results indicate that butane and isobutane appear to be the most convenient working LS fluids from the point of view of coefficient of performance (COP). The highest system performance is obtained using pentane and HFO-1336mzz(Z) in the HS cycle. Compared to third-generation refrigerants (HFC-245fa/HFC-134a), a slight COP improvement is obtained using HCFO-1233zd(E), and HCFO-1224yd(Z). A comparable or even lower volumetric flow rate at the HS compression suction is also observed. The use of pentane/butane achieved maximum COP (3.15), which is a 13% improvement compared to COP obtained when HFC-245fa/HFC-134a is employed. Highlights • A high-temperature heat pump cascade with the IHXs is proposed and optimised. • Synthetic and natural refrigerants with low GWPs are proposed for both stages. • The higher effectiveness of both IHXs in similar proportions increases total COP. • Pentane/butane presents maximum COP and minimum HCFO-1224yd(Z)/HFO-1234yf. • A few refrigerant pairs are comparable with HFC-245fa/HFC-134a in the stages of V ˙ s u c . [ABSTRACT FROM AUTHOR]

Limiting global warming well below 2 °C requires substantial increase in the installation of low-carbon electricity generation technologies (EGTs). EGTs however require several critical materials and materials associated with considerable energy, water and CO 2 emissions. This paper assesses the implications of materials and energy efficiencies for climate change mitigation potential of global energy transition scenarios (GETS). The analysis is carried out using a dynamic material flow-stock model for 21 materials and 15 scenarios combining GETS developed by international organizations including International Energy Agency (IEA) and Greenpeace (GP), materials scenarios, and energy, water, and emissions intensities scenarios. Materials related CO 2 emissions are expected to constitute between 4% and 14% the emissions reported in the IEA Sustainable Development scenario, while expected to be between 10% and 28% in GP Advanced Revolution scenario. Increasing material efficiency and reducing emissions intensities (driven by increasing energy efficiency, renewable technologies in energy supply mix, and recycling) reduce cumulative emissions by 73.2% and 26.3% respectively, while both reduce emissions by 79.5%. Increasing materials efficiency in EGT, energy and water efficiency in mining activities mainly for iron, aluminium, and nickel, and recycling, combined with careful selection of EGTs are significant to realize the full potential of GETS in climate change mitigation. • Materials and energy efficiencies implications for climate change mitigation potential of energy scenarios are assessed. • Dynamic material flow-stock model for 21 materials and 15 combined materials and energy scenarios are used. • Materials related CO 2 emissions constitute between 4% and 14% of emissions reported in IEA Sustainable Development scenario. • Increasing material efficiency and reducing emission intensities reduce cumulative emissions by 79.5%. • Increasing materials efficiency and recycling, and careful selection of EGT are significant for climate change mitigation. [ABSTRACT FROM AUTHOR]

The goal of this paper is to showcase a modelling exercise, conducted for the Republic of Macedonia, a non-Annex I country under UNFCCC and a candidate for EU membership, by making use of MARKAL energy system model. Baseline Scenario and three groups of mitigation scenarios have been developed until 2050, reflecting different types of targets with different levels of ambition regarding CO 2 emissions reduction: (1) EU scenarios – end-year targets compared to 1990 level; (2) QELRC (Quantified Emission Limitation and Reduction Commitment) scenarios – a range of targets over the period 2021–28 and for each subsequent 8-year period, and (3) Baseline deviation scenarios – deviation compared to baseline emission level. The comparative assessment of mitigation scenarios, based on the cumulative emissions, cumulative total system costs and incremental specific reduction cost, has generated a basis for setting the national mitigation contributions and formulating the most appropriate national mitigation action plan. [ABSTRACT FROM AUTHOR]

The EU's energy sector depends heavily on fossil fuels, which contribute to climate change. This is why climate mitigation targets for energy production have been set, including an increased biomass use requirement. In Finland, biomass is commonly utilised but its capital, Helsinki, is still dependent on fossil fuels. With the ambition of becoming climate neutral by 2050, Helsinki is testing, inter alia, low-share wood pellet and coal co-combustion in a CHP (combined heat and power) plant. The objectives of this paper were to assess the net environmental impacts of the co-combustion and changes in urban air quality connected to pellet transport, and to identify environmental hotspots relevant to possible future higher-share co-combustion. The applied methods were screening LCA (life cycle assessment) and fine particle dispersion modelling. The results prove that low-share wood pellet co-combustion in CHP production leads to net environmental impact reductions and does not deteriorate air quality in the urban environment. If higher-share co-combustion were to be implemented, the environmental hotspots to focus on would be the operational issues of a power plant and the origin and sustainability aspects of wood pellet production. [ABSTRACT FROM AUTHOR]

Strengthening capacity for cross-sectoral coordination has a crucial role in enabling ambitious climate mitigation. This research work integrates the Sustainable Development of Energy, Water and Environment Systems Index into a policy framework with three main components to compare possibilities for improving urban system performance. Tiers of integration are defined and compared with the index results for more transformative action. The levels range from unintegrated urban sectors and emerging integration, including those with urban land use and spatial planning, to advanced integration across the urban system. The case study is based on a municipality that is benchmarked to receive an index score of 27.783, placing the urban area in rank 79 among 120 other cities. The measures in the existing action plan are compared with opportunities that would support the municipality in reaching higher tiers of urban integration in the future. Policy learning from other urban areas to which the index is applied is foreseen to support collective action in addressing synergistic opportunities for mitigation. The results have implications on considering urban system integration in the transition to net-zero targets, missions for climate-neutral cities, and the realization of 100% renewable energy systems. • Urban climate mitigation action can focus on integrating across the urban system. • A framework that involves benchmarking is developed in a broader policy context. • The case study receives a benchmarked score of 27.783 as a solution-seeking city. • Tiers of urban system integration are defined with comparisons to opportunities. • Net-zero emission targets can be supported with more transformative urban action. [ABSTRACT FROM AUTHOR]

As climate change is likely to alter regional water availability via shifted precipitation patterns that affect agricultural practices, the analysis of the effectiveness of bioenergy promotion policies and efficiency of bioenergy development requires a thorough consideration of the interrelationships among water, agriculture, and renewable energy development in the context of climate change. We propose a stochastic, price-endogenous mathematical programming with recourse model by linking a well-established water resource model to a bioenergy production framework to investigate the aggregate economic and environmental effect of bioenergy production. This study theoretically analyzes the optimal resource allocation and production conditions of the model, and empirically tests the goodness of the proposed model with observed data. The results show that the proposed framework is likely to reflect the actual bioenergy production in the face of climate-induced impacts, and at small to moderate climate impacts the bioenergy production is likely to be more influenced by the energy and emission prices than by climate-induced yield changes. In addition, while the reduction in precipitation would not result in significant effects on bioenergy production, a substantial change in land use and cropping decisions might occur. • A bioenergy production–water allocation model under climate change is presented. • Optimal resource allocation and production conditions were analyzed and tested. • Uncertain supply of water can substantially influence bioenergy production. • Water supply–agriculture relationship must be aggregated for bioenergy potential. [ABSTRACT FROM AUTHOR]

Energy consumption in the residential sector has grown significantly over the last 30 years. In recent years, a large number of authors have analysed the determinants of behaviour related to climate change. However, in this paper, referring to the behaviour and consumption level, we focused on energy consumption and direct household CO 2 emissions. Thus, the objective of this study was to evaluate the determinants of energy consumption and CO 2 emissions in the Lithuanian residential sector. Energy consumption was evaluated referring to the residential bills based on the official energy prices; CO 2 emission equivalent was calculated employing the emission factors for separate energy resources. The regression analysis revealed that attitudes were significant only in the case of energy consumption for heating, but not in the case of heating-related CO 2 , which depended solely on the housing area, the type of fuel, and home heating (centralized). Meanwhile, concerning electricity consumption and related CO 2 emissions, the pro-environmental behaviour was one of the factors along with the type of house, the number of children, family size, and gender. Results indicated that a complex of different factors needed to be considered to increase energy savings and CO 2 reduction inthe residential sector regarding heating and electricity consumption. • Paper focused on energy consumption and direct household CO 2 emissions. • Attitudes significant influenced energy consumption for heating. • CO 2 emissions are affected by the house characteristics. • Pro-environmental behaviour and the attitudes make limited impact on energy consumption. [ABSTRACT FROM AUTHOR]