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This article discusses the problems of exhaust gas emissions in the context of the possibility of their reduction through the use of fuels with hydrogen as an additive or hydrotreatment. These fuels, thanks to their properties, may be a suitable response to more and more demanding restrictions on exhaust emissions. The use of such fuels in reactivity controlled dual fuel engines (RCCI) is currently the most effective way of using them in internal combustion (IC) engines. Low-temperature combustion in this type of engine allows the use of all modern fuels intended for combustion engines with high thermal efficiency. Thermal efficiency higher than in classic engines allows for additional reduction of CO2 emissions. In this work, the research on this subject was compiled, and conclusions were drawn as to further possibilities of popularizing the use of these fuels in a wide spectrum of applications and the prospect of using them on a mass scale.

Increasing biogas production in the Three Seas Initiative countries (3SI) is a good way to reduce greenhouse gas emissions and to increase energy self-sufficiency by replacing some of the fossil energy sources. An assessment of the biogas production potential carried out for the 3SI at the NUTS 1 and NUTS 2 level shows that the potential of this energy carrier was stable for the period (from 2010–2021). The results showed that it can cover from approximately 10% (Hungary, Slovakia) to more than 34% (Estonia, Slovenia) of natural gas consumption; moreover, there is strong variation in the value of potential at the regional level (NUTS 2) in most of the countries studied. The biogas production forecast was carried out with the ARIMA model using four regressors, which are GDP, biogas potential utilisation, natural gas consumption and investments in RES (renewable energy sources) infrastructure, including changes in the EU energy policy after 24 February 2022. In the most promising scenario (four regressors), the results obtained for the period from 2022–2030 predict a rapid increase in biogas production in the 3SI countries, from 32.4 ± 11.3% for the Czech Republic to 138.7 ± 27.5% for Estonia (relative to 2021). However, in the case of six countries (Bulgaria, Lithuania, Hungary, Austria, Poland and Romania) the utilisation of 50% of the potential will most likely occur in the fifth decade of the 21st century. The above results differ significantly for those obtained for three regressors, where the highest rise is predicted for Bulgaria at 33.5 ± 16.1% and the lowest for Slovenia, at only 2.8 ± 14.4% (relative to 2021).

This paper describes a study of the relative influences of different system design decisions upon the performance of an organic Rankine cycle (ORC) used to generate electricity from foundry waste heat. The design choices included concern the working fluid, whether to use a regenerator and the type of condenser. The novelty of the research lies in its inclusion of the influence of both the ORC location and the auxiliary electricity used by the pumps and fans in the ORC power system. Working fluids suitable for high temperature applications are compared, including three cyclic siloxanes, four linear siloxanes and three aromatic fluids. The ORC is modelled from first principles and simulation runs carried out using weather data for 106 European locations and a heat input profile that was derived from empirical data. The impact of design decisions upon ORC nominal efficiency is reported followed by the impact upon annual system efficiency in which variations in heat input and the condition of outdoor air over a year are considered. The main conclusion is that the location can have a significant impact upon the efficiency of ORC systems due to the influence of climate upon the condenser and auxiliary electricity requirements.

The results in this work show the influence of long-term operation on the decomposition of working fluids in eight different organic rankine cycle (ORC) power plants (both heat-led and electricity-led) in a range of 900 kW el to 2 MW el . All case study plants are using octamethyltrisiloxane (MDM) as a working fluid; the facilities are between six to 12 years old. Detailed analyses, including the fluid distribution throughout the cycle, are conducted on one system. All presented fluid samples are analyzed via head space gas chromatography mass spectrometry (HS-GC-MS). Besides the siloxane composition, the influence of contaminants, such as mineral oil-based lubricants (and their components), is examined. In most cases, the original working fluid degrades to fractions of siloxanes with a lower boiling point (low boilers) and fractions with a higher boiling point (high boilers). As a consequence of the analyses, a new fluid recycling and management system was designed and tested in one case study plant (Case Study #8). Pre-post comparisons of fluid samples prove the effectiveness of the applied methods. The results show that the recovery of used working fluid offers an alternative to the purchase of fresh fluid, since operating costs can be significantly reduced. For large facilities, the prices for new fluid range from € 15 per liter (in 2006) to € 22 per liter (in 2013), which is a large reinvestment, especially in light of filling volumes of 4000 liters to 7000 liters per unit. Using the aforementioned method, a price of € 8 per liter of recovered MDM can be achieved.

Towards a carbon-neutral society, the building sector has a pivotal role with still a great potential for improvement. A new generation of buildings is rising but, to set a more ambitious shift in the paradigm and to fully justify the additional efforts (technological and economic) needed to fill the gap between net zero and plus energy performances, it is essential to consider not only the direct effects, but also all the indirect impacts. However, research conducted in the last decade solely focuses on the direct effects, mainly energy savings, while the indirect impacts neither have a clear identity nor terminology and a defined list of the impacts and methodologies for their quantification is still missing. With these premises, a systematic literature review on the current state of the art was performed in this work, with the aim of (i) investigating the heterogeneous terminology used for such indirect effects, (ii) identifying a final potential list of impacts both at the household and at the community level and (iii) their macro-categorizations, and (iv) exploring the current implemented methodologies and indicators for an economic quantification. As a final result of the analysis, the authors propose a unique terminology for addressing the indirect effects of high-performance buildings. This paper sets the needed basis and common ground for future research in this field, meant to economically quantify the indirect effects in the building sector.

Finland has approximately 150,000 oil-heated private homes. In 2020, the Finnish government launched subsidies for private homeowner energy renovations. In this study, we examine the impact of two new energy renovation subsidies, the ELY grant and the ARA grant, from an energy efficiency point of view. Data from these subsidies reveal that a typical energy renovation case is a building from the 1970s where the oil boiler is replaced with an air-to-water heat pump. With additional data from the Finnish Energy certificate registry, a reference 1970s house is constructed and modelled in the building simulation programme, IDA ICE 4.8. Combinations of several renovation measures are simulated: air-to-water heat pump, ground-source heat pump, ventilation heat recovery and improved insulation. We found that resorting mainly to air-to-water heat pumps is not the most energy-effective solution. Ground-source heat pumps deliver a more significant reduction in delivered energy, especially with additional measures on insulation and heat recovery. Ground-source heat pumps also demand slightly less power than air-to-water heat pumps. Onsite solar PV generation helps supplement part of the power needed for heat pump solutions. Subsidy policies should emphasize deep renovation, ventilation heat recovery and onsite electricity generation.

The development of collective and industrial energy systems, based on wood biomass, knows a significant increase since the end of the 90’s in France, with more than 6000 power plants and heating plants developed currently. Because these systems are built for a minimal duration of 30 years, it is relevant to assess the availability of wood resources according to the potential impacts of global warming on five tree species mainly used in such a supply chain. The assessment of the potential spatial distribution of the suitable areas of these trees in 2050, by using the IPCC (Intergovernmental Panel on Climate Change) RCP6.0 scenario (Representative Concentration Pathway), shows an average decrease of 22% of the plots in comparison with the current situation. The results also point out that mountain areas would maintain a high probability of the development of four tree species. The assessment of the Net Primary Productivity (NPP) underlines a potential decrease for 93% of the plots in 2050, and an increase of this parameter in mountain areas. According to these assumptions, the proposed ecosystem based methodology can be considered as a prospective approach to support stakeholders’ decisions for the development of the wood energy supply chain.