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To recover thermal energy from different sources, its quality and possibilities for utilisation are essential. The wide range of engineering solutions includes a direct connection to the district heating (DH) system and the integration of low-quality heat using heat pumps to increase the temperature level of recoverable heat. Therefore, this article compares waste heat valorisation strategies for integration into existing DH networks, low-temperature DH, and ultra-low heat supply systems using the multi-criteria assessment method. In addition, a local scale assessment was performed to identify the waste heat role in existing RES-based DH systems. The results show that the highest waste heat valorisation rate could be reached when integrated into low-temperature DH systems due to high waste heat potential and suitable temperature conditions. However, a local scale assessment shows a significant impact on the already implemented solar technologies, as waste heat could cover around 70% of the summer heat load. [ABSTRACT FROM AUTHOR]

The EU power sector is under increasing pressure due to rising electricity demand and the need to meet decarbonisation targets. Member states have been active in investing in renewables and building capacity to increase their share of renewables in electricity generation. However, it is important to examine what progress each member state has made in the deployment of renewable energy for electricity generation and what factors influence gross electricity generation from renewable energy. In this study, logarithmic mean Divisia index (LMDI) analysis was used to examine the changes in EU-27 countries' gross electricity generation from renewable energy sources (RES), wind, and solar PV from 2012 to 2021. The results show that the RES deployment per capita effect and the RES share effect were the main positive factors for the total gross electricity generation from RES in the EU. In contrast, the RES capacity productivity effect and the energy intensity effect had negative contributions. Population growth had a positive influence but was less significant than the other factors. The deployment of RES per capita effect was the main factor in the overall growth of gross electricity generation from RES in Northern Europe, Central Western Europe, and Central Eastern Europe, according to comparisons between the regional groups. RES share effect was the main driver in Southern Europe. The decrease in RES capacity productivity was the second most important factor influencing the variation in the amount of energy generated by RES in Northern Europe and Central Western Europe. The results could be used to develop more effective and tailored renewable energy policies that take into account the existing main drivers of RES, wind, and solar energy in each of the EU-27 member states. [ABSTRACT FROM AUTHOR]

European Union (EU) Member States have agreed to limit their greenhouse gas (GHG) emissions from sectors not covered by the EU Emissions Trading Scheme, including emissions from agricultural sector. The aggregated GHG emission rate (i.e. t CO 2 eq. from agricultural sector per country) is commonly used to measure the overall size of agriculture’s influence on climate. And indeed, since 2005, EU has managed to decrease its aggregated GHG emissions by 3.1%. However, the question is—does that mean that EU’s agriculture has become less emission intensive? This paper answers the question by providing a different perspective for the assessment and comparison of the agricultural GHG emissions in 28 EU Member States. It is done by applying three different approaches, including creation of derived indicators and application of multi-criteria analysis (TOPSIS), which is a novel approach for comparison of agricultural GHG emission mitigation performance. The results show that each EU Member State performs very differently in emission intensities. Even more, the emission intensity results show an alarming tendency of increase in most of the EU Member States, which indicates that the measured changes in aggregate agricultural GHG emission rates are misleading. Therefore, the paper suggests reconsidering the policy targets for GHG emission limits. [ABSTRACT FROM AUTHOR]

In this paper we study development patterns of Latvian electricity market. It is done based on a newly developed computer-aided simulation model. System dynamics approach was used to simulate long-term development of electricity sector in the region under the existing policy design. Results demonstrate that renewable energy sources have a high potential to integrate in the electricity generation balance. Important preconditions for this to happen are: presence of appropriate support measures, a continuous technological progress and fossil fuel price increase. Under such scenario around 70% carbon dioxide emission savings can be achieved by 2050. [ABSTRACT FROM AUTHOR]

Abstract: Sustainable residential energy consumption involves a complex, socially embedded and socially constructed market. A system dynamics approach has been used to explore the short, medium and long term impact of different national consumer-oriented energy efficiency policies in the residential building sector. In this paper the system dynamics model has been validated by a case study using historical data from a subsidy scheme and accompanying policy measures in Latvia. Results obtained by the validity tests showed that the model generated behaviour is consistent with available data and is capable of generating “the right behaviour for the right reasons”. Simulation results show that national energy efficiency goals cannot be met by 2016 and the absence of major consumer-oriented policy tools slows down the diffusion process of energy efficiency projects. It also highlights that system dynamics has a high potential to be used for sustainable end-use energy policy planning at both national and sub-sectoral levels. [Copyright &y& Elsevier]

The manufacturing industry is often caught in the sustainability dilemma between economic growth targets and climate action plans. In this study, a Log-Mean Divisia Index (LMDI) decomposition analysis is applied to investigate how the amount of industrial energy-related CO2 emissions in Latvia has changed in the period from 1995 to 2019. The change in aggregate energy-related CO2 emissions in manufacturing industries is measured by five different factors: the industrial activity effect, structural change effect, energy intensity effect, fuel mix effect, and emission intensity effect. The decomposition analysis results showed that while there has been significant improvement in energy efficiency and decarbonization measures in industry, in recent years, the impact of the improvements has been largely offset by increased industrial activity in energy-intensive sectors such as wood processing and non-metallic mineral production. The results show that energy efficiency measures in industry contribute most to reducing carbon emissions. In the future, additional policies are needed to accelerate the deployment of clean energy and energy efficiency technologies. [ABSTRACT FROM AUTHOR]

• GDP growth is the main contributor to GHG emissions increase in low-income countries. • Decreases in energy intensity had the highest impact on GHG emission reductions. • Greater RES and EE efforts are necessary to offset effects from growing economy. • Current climate policies in the Baltics are not sufficient to achieve 2030 targets. The global economy is on the verge of one of the greatest transitions in modern history. The ability to ensure sustainable economic development and prosperity while significantly reducing consumption of energy resources and generated greenhouse gas emissions is a global challenge that affects every country in the world. To assess whether economies are ready for this challenge, there is an urgent need to examine this dual relationship between economic growth and climate change measures. European Green Deal strategy has set the ambitious goal of Europe becoming the first climate-neutral continent by 2050, boosting competitiveness and long-term prosperity of the economy. Kaya identity and LMDI decomposition is applied to examine how European Union countries have been coping with these countereffects historically. The decomposition analysis is conducted for the EU-28 (including the UK) countries for a 10-year study period from 2010 to 2019. This study analyses the main drivers of changes in GHG emissions in European Union and estimates the progress made in implementing the Green Deal targets. The results show that in the EU, energy efficiency improvements have twice the effect on reducing GHG emission compared to RES strategies. The effect of economic growth was the main offsetting factor hindering the achievement of larger GHG emission reductions. More in-depth ex-ante and ex-post investigation is performed for the Baltic States. A novel forecasting technique is applied to project GHG emissions under three different development scenarios, such as the scenario with existing measures, the scenario with additional measures, and the business-as-usual scenario. The results show that the current climate policies in the Baltic States are not sufficient to achieve the 2030 emission reduction targets and that greater efforts should be made to enforce climate mitigation measures in the economies. [ABSTRACT FROM AUTHOR]

Abstract: The outcomes of biohydrogen from photosynthesis processes are still small, however different development methods and laboratory studies are carried out to increase the production yield and meanwhile optimize the process to lessen the negative impact on the environment and climate change. The Life Cycle Assessment (LCA) gives the possibility to compare different biohydrogen production approaches using different photosynthesis methods and, at the same time, identify the environmental “hot spots” of the whole process. Inventory analysis and the results of different researchers in this field allow to find values of selected ecoindicators in order to evaluate the biohydrogen production efficiency with the selection of the best initial data for life cycle analysis. These ecoindicators weigh the resources needed for biohydrogen production whole system. This paper presents the first aspects for the implementation of a life cycle assessment. [Copyright &y& Elsevier]

Abstract: A life cycle assessment was performed to quantify and compare the energetic and environmental performances of hydrogen from wheat straw (WS-H2), sweet sorghum stalk (SSS-H2), and steam potato peels (SPP-H2). Inventory data were derived from a pilot plant. Impacts were assessed using the impact 2002+ method. When co-product was not considered, the greenhouse gas (GHG) emissions were 5.60kg CO2eq kg−1 H2 for WS-H2, 5.32kg CO2eq kg−1 H2 for SSS-H2, and 5.18kg CO2eq kg−1 H2 for SPP-H2. BioH2 pathways reduced GHG emissions by 52–56% compared to diesel and by 54–57% compared to steam methane reforming production of H2. The energy ratios (ER) were also comparable: 1.08 for WS-H2, 1.14 for SSS-H2 and 1.17 for SPP-H2. A shift from SPP-H2 to WS-H2 would therefore not affect the ER and GHG emissions of these BioH2 pathways. When co-product was considered, a shift from SPP-H2 to WS-H2 or SSS-H2 decreased the ER, while increasing the GHG emissions significantly. Co-product yield should be considered when selecting BioH2 feedstocks. [ABSTRACT FROM AUTHOR]

Solar energy has become a reasonable solution for power and heat production due to the continuous advancements of solar technologies. There are several solar system technologies available for heat production in district heating (DH) – solar thermal collectors (SC), photovoltaic (PV) panels for power production and self-power consumption coverage of heating plants, as well as photovoltaic thermal panels (PVT) which can generate both power and heat energy. In addition, the authors of this research consider the integration of heat pumps, which can convert surplus solar power from PV and PVT panels to heat when it is economically beneficial. The article presents a methodology for the comparison of different solar system designs for DH application and energy management strategies by developing hourly-based, mathematical solar system models, identifying several criterions and applying two multi decision-making methods. Sensitivity analyses is performed to evaluate the impact of the main variables changes – solar technology costs, DH heating network temperature, energy and heat tariffs. The results show that implementation of SC collectors is the most desirable solution in most of the analysed scenarios. However, if the DH heating network temperature is lowered by 10 °C, the combination of a solar power system adjusted with a heat pump is the most beneficial solution for self-power consumption coverage of a DH plant and surplus power conversion to heat. • Article presents the methodology for comparison of different solar system designs for DH application. • Integrated heat pump converts the surplus solar power to heat when it is economically beneficial. • The impact of changes in solar technology costs, DH heating network temperature, power and heat tariffs is evaluated. • Implementation of SC collectors are the most desirable solution in most of analysed scenarios. [ABSTRACT FROM AUTHOR]

Latvia's industrial energy efficiency policy imposes the implementation of mandatory energy audits and energy management systems in large industrial enterprises and large industrial electricity consumers to improve industrial competitiveness, to move towards a carbon-neutral economy and to increase the security of supply. Companies affected by this energy efficiency policy are obliged to report to the national energy efficiency monitoring system on energy efficiency measures indicated in energy audits or energy management systems with the highest savings or economical potential. The purpose of this study was to assess the initial outcomes of the first industrial energy efficiency program in Latvia, using data from the national energy efficiency monitoring system, including an analysis of individual energy audit reports, and benchmarking it with findings from a similar program, thereby revealing untapped energy efficiency and CO2 emission reduction potential. Although the national monitoring system made it possible to ascertain results of the energy efficiency program, the statistical analysis of the data did not allow for a robust conclusion on the technical or economic industrial energy efficiency potential. This study suggests that Latvia's energy efficient policy should continue its course in implementation and provides recommendations for improvements on the national energy efficiency monitoring system. [ABSTRACT FROM AUTHOR]

Optimal performance parameters must be found in order to organize efficient heat and mass transfer and effective flue gas cooling using a wet scrubber. Mathematical models are widely used for system optimization. However, a significant number of the available models have application limitations. This study presents a universal model for heat and mass transfer simulation in a scrubber called a fog unit, which has been developed and validated. Validation was performed by comparing the experimental and calculated results. Good agreement was achieved among the data, with differences between results not exceeding 10%. The model facilitates an investigation of the effects of gas flow, droplet size, and sprayed water on heat recovery from flue gas. An experimental matrix for fog unit capacity which included five main variables was designed and analyzed. The boundaries of the parameters are set considering the results of the experiments. The optimization method used is the path of the steepest ascent. The obtained results show the parameter change steps to achieve higher capacity of the condenser. In the studied unit, the maximum condenser capacity is limited by a flue gas flow value of 0.01 Nm3/s. The condenser optimization study that was conducted is viewed as a basis for further studies. [ABSTRACT FROM AUTHOR]

Reliable heat and power supply are among the basic household needs nowadays. It is especially topical in rural or distant locations that may be cut off from the energy grid due to extreme weather or other events. Nonetheless, the sustainability of our power production systems has to be considered to sustain our planet's long-term abilities to provide energy resources and a viable environment. Renewable energy resources must be prioritized in rural and remote areas, simultaneously strengthening distributed production ability and self-sufficiency. In this context, the use of the Stirling engine for heat to power generation in households, on the scale of small communities, and by using only renewable resources is becoming increasingly topical. Therefore, this research aims to identify the current state-of-the-art for Stirling engine applications using biomass as a renewable energy source, in the context of sustainability and energy security. The paper summarizes the current research tendencies at the household level in the use of biomass-based Stirling engines for renewable heat and power generation in decentralized energy systems. The methodology applied is a structured literature review and content analysis. The research results corroborate the progress towards the use of renewable resources and towards increased energy efficiency because the keyword and overlay analysis showed more frequent publishing in these areas. The content analysis on two more specific sub-directions of interest, i.e., biomass-fuelled Stirling engine use in households and Stirling engine implications on energy security, showed that though research activity in these directions has increased lately, more profound research is needed, especially on aspects of energy security and independence. The content analysis revealed a lack of in-depth analysis on the effects of Stirling engine use on energy security or energy independence, which is suggested as a topical subject for future research. [ABSTRACT FROM AUTHOR]

Solar energy is an important alternative energy source that leads to sustainable development of district heating (DH) systems. The aim of this paper is to analyze optimal integration of photovoltaic thermal hybrid (PVT) technology in DH systems by covering industrial power consumption and heat demand of buildings in the Northern European climate. The article compares several different scenarios for the particular case study in order to find the optimal solar system design. The scenarios differ with the size of the installed PVT area as well as an excess power utilization setup. The hourly load and solar energy generation alignment analysis determines the total achievable solar fraction and other parameters for each scenario. The results show that it is economically beneficial to convert excess power to heat when the market price of electricity is lower than the DH heat tariff. This is done with the restriction that the heat demand is higher than solar heat generated. The higher solar fraction is obtained in scenario of maximal PVT area (3000 m 2 ) installation with a power accumulation added. Solar fraction reaches 38% of total heat and power consumption. However, this scenario also has the highest costs and incomes. The calculated value of levelized costs of energy (LCOE) for all scenarios is lower than used reference costs of energy. The total avoided emissions are higher for the scenarios without power accumulation. The specific avoided CO 2 emission costs show that the optimal scenario is with 2000 m 2 PVT area installed. [ABSTRACT FROM AUTHOR]

This article analyses the indicators that describe the overall efficiency of the district heating system and restrictions for its transition towards a 4th generation district heating system. The object of this case study is a district heating company with a modern biomass combined heat and power plant – “Fortum”, in Jelgava. Possible development scenarios for the district heating company moving towards a 4th generation district heating system were analysed. The scenarios were compared via technological, economic and bioeconomic indicators and evaluated for their restrictions for limiting long-term sustainable development. The scenarios which include production of new biomass products (bio-oil) are the most sustainable solutions that allow to increase the added value from 58 €/t wood to 80 €/t wood . The heat tariff was analysed in order to identify the economic feasibility of the development scenarios. Reducing tariffs by improving district heating’s operation is the only unsustainable solution for the district heating company because it reduces the company’s possibility to invest in future developments. It is concluded that bioeconomic development scenarios can support sustainability of the district heating systems. Development decisions need to be taken in due time before the consumption decreases because of energy efficiency measures. [ABSTRACT FROM AUTHOR]

A significant increase in the use of solar energy can be observed. Solar energy is not, however, widely used in Latvia. The aim of this paper is to devise an algorithm to evaluate the possibility of integrating solar energy into the district heating system (DHS) of Latvia for both space heating and the supply of domestic hot water. The methodology was tested on a district heating system in a municipality in Latvia with 20 000 inhabitants. The existing DHS operation data were processed for the analysis and optimization of the system. Optimization of the system includes energy efficiency measures (EEM). Results show the possible energy production from solar energy depends on the area of different solar collector fields and thermal water storage tank volumes, as well as the probable costs of the system. It would be necessary to install solar collection fields of 9000 m 2 to 72 900 m 2 with a properly sized TES in order to produce from 6000 MWh/year up to 23 700 MWh/year. With this system it would be possible to supply 10% to 78% of the total heat demand with solar energy in any given DHS. If EEM have also been implemented, solar energy share can be increased. [ABSTRACT FROM AUTHOR]

The explicit tendency to increase the power generation from stochastic renewable resources forces to look for technological solutions of energy management and storage. In the recent years, the concept of power-to-gas, where the excess energy is converted into hydrogen and/or further methanized into renewable methane, is gaining high popularity among researchers. In this study, we assess the power-to-renewable methane system as the potential technology for power grid balancing. For the assessment, a mathematical model has been developed that assists in understanding of whether a power-to-renewable methane system can be developed in a region with specific installed and planned capacities of wind energy and biogas plants. Considering the varying amount of excess power available for H 2 production and the varying biogas quality, the aim of the model is to simulate the system to determine, if wind power generation meets the needs of biogas plants for storing the excess energy in the form of methane via the methanation process. For the case study, the Baltic States (Estonia, Latvia, and Lithuania) have been selected, as the region is characterized by high dependence on fossil energy sources and electricity import. The results show that with the wind power produced in the region it would be possible to increase the average CH 4 content in the methanized biogas by up to 48.4%. Yet, even with a positive H 2 net production rate, not in all cases the maximum possible quality of the renewable methane would be achieved, as at moments the necessary amount of H 2 for methanation would not be readily available, and the reaction would not be possible. Thus, in the region, the wind power capacities would not meet the biogas plant capacities nor now, nor until 2020. For the system’s development, two potential pathways are seen as possible for balancing the regions’ power grid. [ABSTRACT FROM AUTHOR]

This study explores the causes of changes in energy intensity and energy use in Latvia by applying logarithmic mean Divisia index decomposition and mean-rate-of-exchange index analysis for energy sectors. Analysis on the latest data (2008–2012) reveals if any technological or structural changes have occurred during and after economic downturn in Latvia. The study explored effect of economic activity on final energy use. The results show that the reduction in energy intensity before the year 2008 can be largely attributed to decline in energy intensities within sectors, but the increase in energy intensity after the year 2008 is regarded to expansion of energy demanding sectors. [ABSTRACT FROM AUTHOR]

This paper is devoted to the development of the non-Emissions Trading Scheme for the district heating systems. To select indicators characterizing overall operation of the non-Emissions Trading Scheme district heating system, the article analyses various aspects (type of fuel, temperature regime, level of building energy efficiency) that impact the development of a district heating system model, which strives to reach 4th generation district heating system and to reduces greenhouse emission gases. To determine efficiency rating of the district heating system, a multi-criteria model is developed using selected indicators. The most suitable temperature regime of district heating systems is analyzed for a new buildings and exiting dwelling area depending on end-user heat energy consumption. Research methodology includes algorithm with several modules. The multi-criteria analysis evaluates different district heating systems and identifies optimal solution of 12 scenarios taking into account different criteria. The TOPSIS tool is integrated to find the optimal solutions. Results of the multi-criteria analysis confirm that scenario that is the closest to the ideal solution from the point of view of district heating company, sharply differs from the best scenario of the developers. From the point of view of district heating company the optimal solution is the lowest temperature regime 60/30 and wood chips as energy source. [ABSTRACT FROM AUTHOR]

The energy transition from inefficient fossil-based to sustainable energy systems can face various lock-ins. There are no pathways that are free of stress. However, many routes are possible. A good understanding of the dynamic behavior of systems is crucial, and proper support tools are needed to assess the outcomes of every selected pathway. This study aims to develop an Internet-based interface tool for the national energy simulation model as a tool for a "hybrid forum"; study energy transition lock-ins in one of the Eastern European countries; and apply the interface tool to study different pathways to Latvia's climate and energy goals. System dynamics are used to reach the goals of the study. A causal loop diagram is applied to study feedback loops and lock-ins, a stock-and-flow structure is used to build a simulation model, and a user interface tool is built on top of it. The results show that the developed interface tool is user-friendly and can be used as a discussion platform. The results from the case study reveal how the soft power of Russia can lock in the energy transition in Eastern European countries by creating policy choices with additive effects and what pathways towards energy transition can be used to lock-out. [ABSTRACT FROM AUTHOR]

This paper analyzes the results of providing smart meters and appropriate feedback on electricity consumption in a pilot study involving around 1 000 households in latvia. The findings from our study have shown that smart meter roll-out and provision of appropriate feedback information can provide significant energy savings for household customers. in comparison with the control group the average consumption of the target group fell by 19% year by year. additionally, there was identified in the consumption group 0-399 kWh per month that feedback enabled by smart meters motivated to consume less electricity those customers who recognize options how to change their energy consumption behavior. it was also identified that customer willingness to receive additional information does not necessarily correspond with later actions to reduce consumption. This could be related to actual or desired behavior that together with feedback induced motivation results into energy saving actions. [ABSTRACT FROM AUTHOR]

This study investigates the possibilities how to utilize the combined heat and power plant (CHP) excess heat in the industry during the hot periods of time when the heat demand is limited. in order to maximize the CHP electricity production the efficient heat load has to be increased. The goal of this article is to present the solution for the industrial CHP excess heat utilization for the local cooling. The study introduces the method and model of how to evaluate the industrial CHP plant potential and economical benefit for the production of local cooling from the excess heat. [ABSTRACT FROM AUTHOR]

Abstract: This paper is based on the analysis of the solar combisystem installed in a 4-storey apartment building in Sigulda, Latvia. The combisystem consists of: 42m2 of flat plate solar collectors, a 2.35m3 accumulation tank and a 100kW pellet boiler as the auxiliary heater. This paper focuses on the optimisation of the thermal performance of the pellet boiler. During laboratory tests on the 25kW pellet boiler, the influence of the supply ratio of the combustion air, the chemical and heat losses in the flue gases on the performance of the boiler was established. The results demonstrate the optimum thermal performance, CO emissions, chemical and heat losses, which are related to the amount of free oxygen (O2) in the flue gases. The results of the laboratory tests were then applied to optimise the operation of the 100kW pellet boiler. The flue gas measurements for the 100kW boiler were performed in order to identify the O2 concentration, CO emissions and flue gas temperature. The results showed that what is required to optimise performance is to reduce the amount of air supplied to the boiler’s combustion chamber. Changes were made to the boiler’s control algorithms to achieve the desired result. Additionally, boiler performance was improved by changing the location of the air intake point. Decreasing temperatures in the heat accumulation tank were achieved by making modifications to the boiler’s control algorithms. [Copyright &y& Elsevier]

Abstract: The aim of this study is to develop a method that allows selecting appropriate measures for reductions in negative environmental impacts on a regional energy system. In this paper a sophisticated screening method based on theoretical and practical basics of decision-making is proposed. The proposed method is applied and tested on the energy system of a typical rural middle-sized region in Latvia. The starting point for energy system analysis was evaluation of DSM (demand side management) options but later authors chose to include also primary energy to evaluate the whole regional energy system. The proposed method foresees different aspects: not only technical and economical possibilities, but also political and social factors that are very important in the decision-making process are taken into account. [Copyright &y& Elsevier]

• Benchmark analysis as mathematical regression model for bioeconomy performance. • Multi-criteria analysis as quantitative approach. • Triple nexus for policy, research & innovations, and technology. • Case study for EU countries. The transition to a sustainable bioeconomy by a customized approach would speed up its development and make it more targeted. There is still no common international method for determining, measuring and comparing the extent of sustainability. The aim of this research is to develop a methodology for the assessment of bioeconomy-influencing factor interlinkages, and creation of benchmarks through a top-down approach. The main output is the assessment of factor interlinkages that could be further used for composite index creation. A case of triple factor nexus is presented: policy, research and innovations, and technology nexus for EU countries. As a result, the empirical model presents the mathematical description of policy, research and innovation, and technology link benchmark. [ABSTRACT FROM AUTHOR]

Implementing innovation and sustainable development of district heating requires sound energy planning at the national and local levels. However, a research gap still exists on technically and economically viable solutions for developing fully decarbonized heat supply systems and assessing their environmental impact to provide a holistic analysis. Therefore, the case study-based research includes in-depth analyses of the current situation and existing operating conditions of the solar field, biomass and natural gas boilers, and thermal storage tank. The future fossil-free scenarios analyze the additional thermal storage capacity, and integration of heat pumps and local waste heat sources to reduce fossil fuel consumption, increase energy efficiency and minimize heat production costs. The results show that the waste heat utilization and heat pump integration allow to phase-out of natural gas for the peak load coverage. However, increasing thermal storage capacity by more than 50 % is crucial to store the thermal energy for peak demand-supply. The increased thermal storage tank volume allows higher biomass production rates and aligns the heat production with the available waste heat sources. The total heat production costs in a low-temperature heat pump scenario decrease by 5 %. The environmental impact assessment shows that the low-temperature heat pump scenario decreases the resource category by 61 % and the climate change category by 17 % in comparison with the Reference scenario due to higher solar yield and higher overall efficiency. • Research analyses multi-source district heating system decarbonization by integrating waste heat. • The waste heat from flue gas condenser and wastewater treatment plant is considered. • The thermal storage capacity increase and network temperature lowering are basic conditions for cost-optimal solutions. • EnergyPRO simulation model and life cycle assessment are merged to develop a holistic methodology. • Waste heat integration and heat pumps bring environmental benefits compared to biomass and fossil fuel combustion. [ABSTRACT FROM AUTHOR]

The main aim of this study is to evaluate the results achieved by implementation of different support policies in form of subsidies for energy efficiency improvements and transition to renewable energy sources. The article compares the energy efficiency measures in district heating systems with other support program. In order to assess the effectiveness of implementation of different renewable energy technologies and energy efficiency projects, the levelized costs of saved energy for different support programs were determined. Authors compared different co-financed projects related to replacement of fossil fuel energy sources in district heating (mainly to biomass) and the installation of new biomass boilers, heat pumps, solar collectors and other local technologies in municipal buildings. Results show that financial support for energy efficiency measures in industrial enterprises and district heating systems has been most cost-effective, mainly due to the low co-financing rate (30%) and the high potential for energy savings in different production processes. Authors have identified the blind-spots within the funding allocation for different municipalities, which is not always dedicated to achieved energy savings. [ABSTRACT FROM AUTHOR]

Implementation of energy efficiency measures promotes energy consumption reduction, reducing impact on climate, ensuring energy security. A country's energy efficiency potential depends on the existing energy consumption, the overall technical possibilities and previously implemented energy efficiency measures. Availability of qualitative subsector level data is needed to determine country's energy efficiency potential. In Latvia such data in aggregate form have been lacking. Therefore, we collect the data from the mandatory energy audit program initiated in Latvia in 2016, to assess the energy end-use distribution, implemented and potential energy efficiency measures and the energy efficiency potential in industrial companies covered by the audit program. The specific costs of energy efficiency measures are analysed by energy efficiency cost curve method. The results suggest that corrections in implementation and data gathering of the mandatory energy audit program are required to achieve better data quality and wider application of obtained data. Average technical energy efficiency potential for assessed 111 industrial companies that had submitted their audits to the program until October 2019 was 6.35%. However, the true potential could be higher (e.g. for some companies the identified technical potential was up to 40%) if weaknesses in the implementation of the audit program would be corrected. • The results of first mandatory energy audit program in Latvia are analysed. • Energy efficiency cost-curves are calculated for 7 energy end-use categories. • Improvements to national energy audit program are suggested. [ABSTRACT FROM AUTHOR]

District heating (DH) systems present a great opportunity to increase the proportion of renewable energy used in both heating and cooling. Renewable energy can be integrated into DH to account for heat load and also for power production, which in cogeneration systems is used for both heat generation and transmission. The main aim of this research is to determine whether (and also how) to integrate solar PV panels into DH systems to achieve an economically feasible, flexible energy production solution by using a power-to-heat concept. To reach greater depth in this research, the system dynamics (SD) approach was used. The results show that it is not profitable to install larger PV panels than are needed to provide for summer electricity use. However, use of the power-to-heat concept can expand the flexibility of a solar power system and increase the overall efficiency or economic feasibility when the power generated exceeds consumption. When integrating a larger PV area, the surplus power can either be transferred back to the grid or used for heat production via a heat pump. On average, about 47% of excess power is converted into heat and 53% is sent to the grid. Results show that policies both in the form of subsidies for PV panels and increases in the price of heat can significantly influence the results. • Authors use the system dynamics approach for the PV integration analyses. • The hourly data of heat demand, power consumption and solar irradiation are used. • Use of the P2H concept can expand the flexibility of a solar power system. • Results shows that about 47% of excess solar power is converted into heat. [ABSTRACT FROM AUTHOR]

Abstract The aim of this review is to discuss how quantitative modelling of energy scenarios for sustainable energy transition pathways can be made more realistic by taking into account insights from the socio-technical and related literatures. The proposition is that an enriched modelling approach would focus not just on technology development and deployment, but also on feedback loops, learning processes, policy and governance, behavioural changes, the interlinkages between the energy sector and other economic sectors, and infrastructure development. The review discusses a range of socio-technical concepts with a view to how they can enrich the understanding and modelling of highly complex dynamic systems such as flexible energy systems with high shares of variable renewable energy. In this context, application of system dynamics modelling (SDM) for the analysis of energy transitions is also introduced by describing the differences between SDM and a traditional modelling approach that uses econometric and linear programming methods. A conceptual framework for this type of modelling is provided by using causal loop diagrams. The diagrams illustrate the endogenous approach of SDM – understanding and modelling the structure of a system, which is responsible for its dynamic behaviour. SDM can also capture the co-evolution of economic, policy, technology, and behavioural factors over sufficiently long time periods, which is necessary for the analysis of transition pathway dynamics. In this regard, the review summarises how socio-technical concepts can be approached in SDM and why they are relevant for the analysis of flexibility in energy systems. From a computational point of view, it could be beneficial to combine SDM with technologically detailed energy system optimization models and that could be a way forward for achieving more realistic, non-linear quantitative modelling of sustainable energy transitions. Highlights • Socio-technical factors can improve modelling of energy transitions pathways. • Transitions pathways involves technological, economic, and institutional domains. • Transitions pathways can be endogenously represented by co-evolving stocks and flows. • Co-evolving stocks represent complementarity of technologies and other factors. • Pace of transition and energy flexibility depends on interactions of these factors. [ABSTRACT FROM AUTHOR]

Buildings consume 40% of the total primary energy use worldwide and it could increase if no energy efficiency measures are taken. Diffusion of nearly zero energy buildings is among building energy efficiency measures in many countries. Synergy of energy reduction in buildings and efficiency increase in district heating and cooling networks is part of Smart Energy Systems. Utilisation of solar energy is part of nearly zero energy buildings concept. The main aim of this research is to carry out numerical and experimental study of storage capacity and the dynamic behaviour of a solar facade module that can accumulate solar energy to reduce heating and cooling loads in nearly zero energy building. In this study, the first part of the climate adaptive facade element – solar facade module is developed: the point focus imaging Fresnel lens is employed for concentrating solar beam on copper plate with fins which is used as heat transfer enhancer to phase change material. Results show that the dynamics of heat flows and accumulation processes in the facade module are very complex due to highly changing outdoor and indoor conditions. The indoor temperature difference in the range of 0.5 °C and 9 °C is observed between the opaque reference wall and the solar facade module depending on the time of the day and season. [ABSTRACT FROM AUTHOR]

The number of regional and national power systems with a high share of wind and solar power in the world is quickly increasing. The background for this development is improved technology, decreasing costs, and increased concern regarding environmental problems of competing technologies such as fossil fuels. For the future there are large possibilities for increasing the renewable electricity share. However, variable renewable power production has to be balanced. Demand side flexibility offers an interesting approach to the balancing issues. The aim of this paper is to compare flexibility potentials and how they were estimated in seven Northern European countries in order to compare general challenges and results as well as the connection between used method and results. The total flexibility is estimated to 12–23 GW in a system with a total peak load of 77 GW. [ABSTRACT FROM AUTHOR]

The research identifies and describes administrative procedures for implementing RES electricity generation infrastructure projects in Baltic and Nordic countries. The administrative processes of installing small to large solar parks and onshore wind farms for electricity generation were assessed, looking at several criteria such as the timeline, complexity, information availability, impact of public opinion, and local authorities (municipalities). The methodology developed allows evaluating administrative procedures using a multi-criteria analysis method, resulting in a single-score quantification that can be further utilized in complex energy simulation models. The obtained results allow identifying the potential recommendations for process optimization in the analysed countries. For instance, the introduction of a single point of contact as in Norway, the consolidation of the environmental impact assessment and spatial planning phases as in Finland, and the simplification of the microgeneration and small-scale installation permitting process as in Lithuania. • Administrative processes for installing solar PV parks and wind farms were evaluated based on 11 criteria. • Methodology developed allows for evaluating administrative procedures in different countries using MCDA. • The analyses provide a single-score quantification which can be further utilized in complex energy simulation models. • Transparency for installing wind farms and solar PV parks could be increased trough publicly available guidelines. [ABSTRACT FROM AUTHOR]

This study analyzes the impacts of taxes, subsidies, and electricity transmission and distribution tariffs and heat storage on the operation and economic feasibility of district heating plants with different flexibility potentials in the Baltic countries. Under 2016 conditions, the lowest levelized cost of heat is achieved by a combination of wood chip boilers, electric boilers, and heat storage. Heat storage enables a higher utilization of least-cost technologies, resulting in greater cost efficiency for all considered scenarios. Current taxes and subsidies are found to have limited impact on the operation of combined heat and power plants and electric boilers. [ABSTRACT FROM AUTHOR]

The need for substitution of fossil resources with renewable alternatives, for an efficient use of the bio-resources, and for the development of knowledge-intensive sustainable economies call for the design of policies to create and govern biotechonomic systems. The goal of this study is to create a tool to facilitate such policy design, - aimed at the development of biotechonomic systems by use of a system dynamics model. This model constitutes a general framework for the representation of critical biotechonomic sectors; their land use, production and consumption of raw material, research and development, investments in and utilization of production capacities (i.e. capital investments), their utilization of labour, finances (value creation, capital and operating costs and profit), and sustainability. A sustainability index, based on emergy is applied to assess the environmental performance of the various sectors considered. Moreover, the model is operational and lends itself to the simulation of the development of these sectors, both past and future. This model may be applied to a variety of biotechonomic sectors and extends to the cyclical economy at large. As the purpose of this model is to facilitate the development and testing of policies, the model allows for the inclusion of structural components that represent such policies, including the extension of production lines, the utilization of taxes and subsidies to modify the land use and to encourage the redirection of materials, and support for the investment in research, development and capital. Model is applied to example of birch use as raw material. Results show that model framework can be applied to micro, meso and macro level planning and policy making. [ABSTRACT FROM AUTHOR]

The article examines the transition from conventional district heating (DH) system to a 4th generation DH (4GDH) system using system dynamics modeling and economic feasibility analysis. Six alternative scenarios are studied. Energy saving measures reduce energy consumption, CO 2 emissions and installed capacity of heating equipment thus facilitating the transition of the DH system towards zero emission system. Reduction of the required installed heating capacity allows implementing a low-temperature regime for heat distribution networks. For four of the analyzed scenarios this regime was achieved without increase of electricity consumption for heat supply. Results show that the implementation of 4GDH depends on the policies applied. The research identifies a balance point between the implementation of energy efficiency measures at the source and at heat consumers’ side. The article shows how the price of a fossil fuel influence the share of heat energy production and the balance point between investment at the source and heat consumers side. [ABSTRACT FROM AUTHOR]

The article analyzes district heating system efficiency by using benchmarking system. The 26 biggest Latvian DH companies were taken as case study for analysis. Two main components were distinguished from existing district heating systems tariffs: cost of fuel in tariff and other costs. Non-linear regression model is used for benchmarking analysis. Equation, which describes other costs as dependent variable, whereas fuel part of costs in tariff as independent variable was obtained. Performance of Latvian district heating companies were evaluated by using various efficiency indicators describing systems technical, scale, dynamic and financial parameters. Data envelopment analysis was used for measuring efficiency of these companies by taking into account multiple factors. In order to indicate main parameters that influence heat energy tariff and efficiency of all district heating system, sensitivity analysis by using system dynamic model developed in previous study was carried out. The model finds out the possibility to introduce the 4th generation district heating system in Latvia. Model includes the transition of heat network to the low-temperature regime at 80% share of the renewable energy. Moreover, matrix with district heating system efficiency parameters, which are most vital for optimization, was made. [ABSTRACT FROM AUTHOR]

Seaweeds are considered a viable feedstock for producing energy through the anaerobic digestion conversion process. Its exploitation and use as an alternative renewable energy source; however, remains marginal in the EU. This study aims to evaluate BMP in batch tests of the brown algae Fucus vesiculosus from the Baltic Sea and collected from the Latvian coast. The lab scale BMP tests were oriented towards the evaluation of the effects of mechanical and microwave pre-treatment methods, as well as the impact of a different algae-to-inoculum (A/I) ratio using: i) cutting blades together with mortar and pestle (C&PM) in combination with the use of a 700 W capacity microwave, ii) 1:3 and 1:5 A/I ratios. The cumulative CH 4 yields show a value in the range of 68 ± 21 mL CH 4 /g VS – a trial with no microwave treatment and A/I of 1:3) and 144 ± 28 mL CH 4 /g VS – a trial including a microwave treatment for 3 min, and A/I ratio of 1:3. The results show effectiveness in the range of 7.8%–43.7%, when the microwave pre-treatment is applied for 1.5 min, and a range of 37.2%–45.2% when the pre-treatment is applied for 3.0 min. The results of this study suggest promising potential for F. vesiculosus for biogas production, especially in the Baltic region. [ABSTRACT FROM AUTHOR]

• Transport decarbonization depends largely on the effectiveness of national policies. • Energy savings and switching to RES have difficulty offsetting economic growth impact. • Most countries lag behind in providing the infrastructure for zero-emission vehicles. • Different mechanisms should be used in Nordic, Western, and Eastern EU countries. Greenhouse gas (GHG) emissions are declining in all major sectors in the European Union, with the exception of one sector that has seen a significant increase in GHG emissions over the past decade - transport sector. The European transport sector faces a significant challenge in achieving the decarbonization goal set by the European Green Deal. Although the European Commission is planning to introduce a set of EU-level measures, such as the inclusion of road transport in the EU Emissions Trading System, the progress of greening the transport sector has so far largely depended on national policies. To understand whether European countries are committed to rapidly adapt to low-carbon transport systems, it is crucial to evaluate what progress have national policies achieved so far in moving towards a sustainable transport system. This study used a three-level assessment of transport sector sustainability across European countries. First, this study assessed the overall sustainability level of the transport sector in all European Union Member States and the United Kingdom using the composite sustainability index method for cross-country comparison. Countries were compared using 15 transport indicators grouped into four dimensions (mobility, sustainability, innovation, and environment) based on the latest available data from 2017 obtained from Eurostat, European Commission, and Odysee-Mure databases. Second, in order to identify the dynamics of progress, Logistic Mean Division Index (LMDI) decomposition analysis was conducted to assess the changes in greenhouse gas (GHG) emissions from the transport sector over ten years, taking into account the five main factors: emission intensity effect, renewable energy (RES) transition effect, energy intensity effect, economic growth effect, and population growth effect. Third, to analyse what has impacted the sustainability of the transport sector in countries, the study highlighted several key policies (directions) for decarbonizing transport from the analysis outlining the good practice policies from the best performing countries. The combined results of the composite sustainability index and decomposition analysis revealed significant differences between Nordic, Western, and Eastern European countries, suggesting that different approaches should be taken in developing effective sustainability policies for transport. [ABSTRACT FROM AUTHOR]

Some eco-innovations have already reached a mature state, but they diffuse slowly. There is little known about the importance of various factors on the diffusion process of eco-innovations. The aim of this research is to propose a conceptual model for eco-innovation diffusion, where particular case study of eco-innovation – micro-fibre cloth (MFC) for surface cleaning purposes – is given. The work will study the relative importance of various motivations on diffusion processes as well as the influence of information campaigns. This novel methodology has been developed under the system dynamics framework and is coupled with the logistic regression model. Structural validation tests were done for the proposed model. The methodology is proposed, then the integrated empirical study and system dynamics model are completed. The results of the logistic regression models show that the overall attitudes and social influence has the most dominant impact on intention to use the studied eco-innovation products. The most sensitive parameters in the system dynamics model were found to be the adoption faction of information received by word-of-mouth, households adopting micro fibre cloth at the beginning of the simulation, and the contact rate per household. The proposed methodology, and developed mathematical model can also be used as the basis for other studies of other diffusion processes, since system dynamics modelling is a white-box modelling approach, and the structure of the model can be enhanced with the latest results from other studies. [ABSTRACT FROM AUTHOR]

In the article, a possibility to introduce the 4th generation district heating (4GDH) in Latvia is analyzed with the system dynamic modeling. Three policy instruments were included into the system dynamic model: subsidies, instrument for risk reduction and instrument for efficiency increase, and their impact on the system operation was analyzed. Six development scenarios are examined in the article, two of which are supplemented with the transition of heat network to the low-temperature regime at a different share of the renewable energy (60%, 80%, 95%). The heat tariff was used as the main indicator determining the pace and structure of the technology change. In the model the existing natural gas technology was included and three technologies of the renewable energy – biomass combustion equipment, solar collectors with the accumulation and heat pumps. Results of the modeling shows that scenario, at which no policy instruments are used, reduce CO 2 emissions for 58.6% until 2030; but it is possible to achieve a zero emission level, in case political instruments are used. [ABSTRACT FROM AUTHOR]

The European Union has given a long-term commitment towards a low-carbon society. Power sector is to play an important role in achieving ambitious emission reduction goals. This article presents results of a research aimed at evaluating development of the Baltic power system under current framework conditions. Special focus is put on renewable energy analysis to estimate the potential of power sector decarbonization. A dynamic energy-economy model was developed by applying system dynamics modelling approach in order to evaluate changes in the energy system till 2050. Underlying structure of the model is based on energy resource flows according to the national electricity mix of each Baltic State. The model calculates energy generation costs of each technology taking into account national support schemes. Based on cost estimation, the installed capacity of each energy resource is determined. Modelling results suggest that wind energy has the potential to become dominant in the Baltic region. This is explained by increasing competitiveness of wind-generated power price compared to fossil-fuel-based generation. Solar energy has the potential to become popular from 2025 onwards due to decreasing investment costs. The market share of other renewable electricity technologies, such as hydro and biomass, will continue to increase reaching maximum between 2020 and 2030. Biogas plants are still not expected to play considerable role in electricity generation. [ABSTRACT FROM AUTHOR]

In case of opening the electricity market, various factors interact with each other. Although research has been done on various factors affecting the liberal electricity market, little attention has been paid to studying the dynamic relations between the actors involved in the liberal electricity market and projections on electricity consumption in households. The main aim of the research is to explore both short- and long-term effects on the electricity consumption at liberal market conditions by modelling various development scenarios. The electricity market in operation in Latvia was used as the case study. For the simulation of electricity market liberalization, system dynamics has been chosen. This method can determine electricity savings in case of electricity market opening, because system dynamics allows conducting simulation of complex systems and analysing the obtained data to forecast probability of the development of several scenarios. Obtained results show that cumulative electricity savings in households could reach 560 GWh by the end of 2020 due to the opening of the electricity market, implementation of energy saving measures and other reasons. In case of scenario analysis using the change of consumption behaviour, it was obtained that the cumulative electricity saving could be almost twice as big if the majority of households were guided by the environmental concerns. Although the system dynamics model was based on the Latvian case study, its general application to other countries and electricity markets is also possible. [ABSTRACT FROM AUTHOR]

Much study in recent years has focused on hazardous waste management, where one of the hazardous waste streams includes portable waste batteries. The main aim of the research is to explore both the short and long term effects of a collection scheme of portable waste batteries on the environment. To this end, a system dynamics model has been built to examine how the physical processes and information flows interrelate in the structure of a dynamic system, and how this structure generates dynamic behaviour over time. A collection scheme in operation in Belgium was used as the case study. The model developed sheds light on the structure of the system and shows that important feedback is missing compared to other types of battery collection models. Firstly, the model showed that the level of the levy on the price is not linked to the achieved collection goal. Secondly, the other missing feedback is between effectiveness of the information campaign and the costs related to these awareness-increasing activities. The model developed could be an important aid for policy makers in assessing the efficacy of policy tools. [ABSTRACT FROM AUTHOR]

Using biowaste as a resource is required in order to meet the EU common objectives for waste management. Biowaste management should be considered from the economic, environmental, and social perspectives. The resulting complexity constitutes an important barrier to the implementation of biowaste planning projects. The goal of this study is to propose an effective tool to assess, compare, and select the best biowaste management alternatives for stakeholders. In order to reach research goal a methodological approach based on the combination of Multi-Criteria Analysis and System Dynamics method is proposed. The aim of the proposed method implemented in a modelling tool is mainly addressed to policy and decision makers specifically (1) to evaluate biowaste management options, (2) to assess the sustainability of bioenergy projects, and (3) to find an optimal solution for biowaste treatment given the conditions in a particular region. The proposed method can help to structure and assess complex problems while both responding to the interests of multiple stakeholders and avoiding the weaknesses of other evaluation techniques. The method has been applied to a case study involving the three Baltic States – Latvia, Lithuania and Estonia. The results obtained showed that separate collection and Anaerobic Digestion of biowaste is the best solution in all three Baltic States. Other acceptable options include incineration with energy recovery and Mechanical Biological Treatment with Anaerobic Digestion. [ABSTRACT FROM AUTHOR]

Decarbonisation of transport has become central to European Union policy. Biofuels are expected to represent a substantial part of the overall strategy towards diversifying Europe's energy supplies and curbing greenhouse gas emissions in a cost-effective way. This research deals with the dynamic simulation modeling of a biodiesel market as a part of transportation fuel market and analyses of various policy support instruments on increasing the proportion of biofuel in total transport fuel demand. The study is carried out for Latvia's road transport sector. After it had experienced generous financial support from the government allowing the industry to develop, support was abruptly stopped creating stagnation in both biodiesel supply and demand. This threatened the national transport policy goals. The goal of this research is to find the most effective policy strategies for achieving the national transport policy goals by applying system dynamics modeling to the current market conditions of transport fuels.. Specifically, the primary focus of this paper is an attempt to gain insight into the long-term dynamic behavior of the biodiesel market in Latvia. The principal policy tools and mechanisms implemented can be summarized as: i) state subsidies at different levels and stages (i.e. the biodiesel production sector, the agricultural sector, and the end consumer sectors), ii) increasing the excise taxes on fossil fuels, iii) increasing the share of the biodiesel in the transportation fuel blend. The results obtained from model simulations confirm that promoting biofuel acceptance among end-users is the primary key issue. [ABSTRACT FROM AUTHOR]

The Latvian district heating system historically is characterized with a high share of imported natural gas. The paper looks at the situation where specific policy tools significantly increase the proportion of renewables, in particular of wood fuel, in the energy balance. Within this context a system dynamics model was developed to identify the most suitable policy from the long term perspective for the replacement of the fossil fuel with the local biomass at the district heating. The policy instruments included in the model are: national subsidies for replacement of fossil fuel technologies, short-term informative campaign to decrease the investment risks related to the use of wood fuel-based technologies, implementation of Research and Design strategies aimed at the increase of efficiency of the wood fuel technology, and implementation of the Emission Trading Scheme and the CO 2 taxation. The modelling results show that national level climate policy measures are substantial for promoting the use of renewable energy. The combinations of the above mentioned policy instruments significantly increase the share of wood fuel in the Latvian district heating system. In addition, the Emission Trading Scheme confirms its essential role in promoting the use of renewable energy within the district heating sector. [ABSTRACT FROM AUTHOR]

Highlights: [•] Historic buildings are the trademark of cities. They show a high level of energy inefficiency. [•] Saving energy by heating less and living in twilight would worsen living conditions. [•] It is reasonable to invest in the energy refurbishment of historic buildings. [•] Assessing of building modernization carried out is MCDM problem with not crisp values. [ABSTRACT FROM AUTHOR]

Power demand-side management has been identified as one of the possible elements towards a more flexible power system in case of increased capacities of variable renewable energy sources—solar and wind energy. The market coordinators or aggregators are introduced to adjust the electricity consumption by following the market situation. However, the role of aggregators is mainly analysed from the economic perspective, and the demand side management is performed to maximise the utilisation of low price power during off-peak hours. However, this research focuses on analysing the introduction of aggregators as a future player to increase the total share of renewable power and decrease the surplus solar and wind electricity occurrence. An in-depth system dynamics model has been developed to analyse the hourly power production and power consumption rates at the national level for the Latvia case study. The results show that introducing aggregators and load shifting based on standard peak shaving can increase the share of surplus power and does not benefit from increased utilisation of solar and wind power. On the contrary, demand-side management based on available RES power can decrease the surplus power by 5%. [ABSTRACT FROM AUTHOR]