Terms Of Primary Energy Consumption Research Articles

Energy Assessment of Different Powertrain Options for Heavy-Duty Vehicles and Energy Implications of Autonomous Driving

Heavy-duty vehicles (HDVs) are responsible for a significant amount of CO2 emissions in the transport sector. The share of these vehicles is still increasing in the European Union (EU); nevertheless, rigorous CO2 emission reduction schemes will apply in the near future. Different measures to decrease CO2 emissions are being already discussed, e.g., the electrification of the powertrain. Additionally, the impact of autonomous driving on energy consumption is being investigated. The most common types are fuel cell vehicles (FCEVs) and battery-only vehicles (BEVs). It is still unclear which type of powertrain will prevail in the future. Therefore, we developed a method to compare different powertrain options based on different scenarios in terms of primary energy consumption, CO2 emissions, and fuel costs. We compared the results with the internal combustion engine vehicle (ICEV). The model includes a model for the climatization of the driver’s cabin, which we used to investigate the impact of autonomous driving on energy consumption. It became clear that certain powertrains offer advantages for certain applications and that sensitivities exist with regard to primary energy and CO2 emissions. Overall, it became clear that electrified powertrains could reduce the CO2 emissions and the primary energy consumption of HDVs. Moreover, autonomous vehicles can save energy in most cases.

Performance Evaluation of a Fuel Cell mCHP System under Different Configurations of Hydrogen Origin and Heat Recovery

Motivated by the growing importance of fuel cell systems as the basis for distributed energy-generation systems, this work considers a micro-combined heat and power (mCHP) generation system based on a fuel cell integrated to satisfy the (power and thermal) energy demands of a residential application. The main objective of this work is to compare the performance of several CHP configurations with a conventional alternative, in terms of primary energy consumption, greenhouse gas (GHG) emissions and economic viability. For that, a simulation tool has been developed to easily estimate the electrical and thermal energy generated by a hydrogen fuel cell, and all associated results related to the hydrogen production alternatives: excess or shortfall of electrical and thermal energy, CO2 emission factor, overall performance, operating costs, payback period, etc. A feasibility study of different configuration possibilities of the micro-CHP generation system has been carried out considering different heat-to-power ratios (HPRs) in the possible demands, and analyzing primary energy savings, CO2 emissions savings and operating costs. An extensive parametric study has been performed to analyze the effect of the fuel cell’s electric power and number of annual operation hours as parameters. Finally, a study of the influence of the configuration parameters on the final results has been carried out. Results show that, in general, configurations using hydrogen produced from natural gas save more primary energy than configurations with hydrogen production from electricity. Furthermore, it is concluded that the best operating points are those in which the generation system and the demand have similar HPR. It has also been estimated that a reduction in renewable hydrogen price is necessary to make these systems profitable. Finally, it has been determined that the most influential parameters on the results are the fuel cell electrical efficiencies, hydrogen production efficiency and hydrogen cost.

Integrated optimization of the building envelope and the HVAC system in nZEB refurbishment

• The retrofit of the Mediterranean hotel is considered in the multi-objective optimization. • Excessive thermal insulation and oversizing of HVAC system can be avoided. • Water-to-water heat pump system is the most promising nZEB solution for year-round hotel operation. • Air-to-water heat pump system can be advantageous for seasonal hotel operation. • The implementation of RES and production of electricity by PV panels is mandatory. The research presents the method for optimization of a building with its heating, ventilation and air-conditioning (HVAC) system in the scope of achieving nearly zero energy building (nZEB) in the context of Energy Performance of Buildings Directive 2010/31/EU. The method is based on coupling the dynamic simulation models created in Trnsys software with the non-dominated sorting genetic algorithm (NSGA-II), as the engine which performs an optimization process to minimize global cost (GC) and primary energy consumption (PEC). The optimization comprises energy efficiency measures (EEM) on a building envelope with a parametrized model of the HVAC system. The procedure implements building simulations under design weather conditions for heating and cooling to establish the connection between building design and the HVAC system size. The analysis is performed using discrete equipment sizes and specifications according to manufacturers’ data, ensuring the selection of actual products with their sizes and costs. In continuation annual simulations using referent year data were performed. Several HVAC systems were considered, ranging from conventional natural gas-based systems to systems based on renewable energy sources (RES). The method is applied in the case study of the refurbishment of a representative hotel building on the Croatian Adriatic. The results reveal a large gap in terms of PEC between the nZEB system (biomass boiler, solar thermal collectors and absorption chiller, 138.9 kWh/m 2 ) and the cost-optimal system (natural gas boiler and compression chiller, 269.6 kWh/m 2 ). The most promising solution for a hotel with year-round operation character is water-to-water heat pump system using seawater as the heat source and sink (170.2 kWh/m 2 ). When the use of seawater is not possible, or when cooling energy prevails over heating energy use, air-to-water heat pump system appears to be suitable solution (176.4 kWh/m 2 ). It is found that in addition to HVAC system with low PEC, the application of solar photovoltaic (PV) system is required to reach Croatian nZEB target for a renewed hotel (115 kWh/m 2 ). Further analysis of the results shows that the optimal parameters of EEM vary depending on applied HVAC system. The results indicate that optimal solutions are achieved when the HVAC system size matches the design load. Therefore, excessive oversizing of the HVAC system may have negative impact on GC. Based on the results and the findings, conclusions and general guidelines for the refurbishment of a hotel building on the Adriatic coast are established.

Analysis on the Economic Feasibility of a Plant Factory Combined with Architectural Technology for Energy Performance Improvement

In this study, a comparative economic analysis was conducted for typical greenhouses, plant factories with natural and artificial light, and those with only artificial light, based on the insulation, artificial light, and photovoltaic (PV) installation costs. In addition, the results of research on primary energy consumption and greenhouse gas (GHG) emissions from the use of fossil fuels were presented. By comparing the case-wise annual energy consumption, when all energy sources were converted into primary energy consumption based on the applied coefficients for collection, transport, and processing, to unify calculations for different fossil fuel energy sources, the case of the installed PV systems exhibited large reductions, of 424% and 340%, in terms of primary energy consumption and GHG emissions, respectively. Furthermore, electric heating resulted in higher primary energy consumption and GHG emissions than oil. When the economic analysis included the plant factory installation cost used to maintain the temperature required for plant growth in winter, the PV installation exhibited the highest cost; additionally, all plant factories showed an investment payback period of seven to nine years, which is comparable to typical greenhouses. Based on these results, we aim to reduce the use of fossil fuels for sustainable energy by combining architectural technology for improved energy performance in the agricultural environment.

Determination of the inner forms of hollow blocks containing phase-changing material for different climate regions

Hollow blocks are used widely in buildings for their lightweight construction and high thermal resistance characteristics. When used with a phase change material (PCM), these blocks can reduce the heating and cooling loads of buildings compared to conventional hollow blocks. However, it is essential that the block inner forms and PCMs should be selected based on climate conditions. In this study, hollow blocks containing PCM in different climate types are thermally analysed. In the first step, ten different formed blocks are thermally analysed. In these blocks, the effects of hollow ratio (HR), inner form, and the number of cavities on heat flux and temperature distribution are investigated. The inner form of the hollow block with the least heat flux is determined in this step. The second step consists of optimization for the PCM melting temperature and layer thickness for the different provinces. The optimization results are evaluated on a building in terms of primary energy consumption and global costs. The best performing locations of the PCMs within the block are defined for all provinces in the last step. The results of the study are discussed in terms of the block surface temperatures and liquid fraction. The best PCM locations are found close to the block’s centerline in hot and warm climates and close to the indoor side in cold climates.

Clean heating in Northern China: Regional investigations and roadmap studies for urban area towards 2050

With rapid urbanization, the building stock and related winter heating demands are developing fast in the urban regions of Northern China. In addition to the national strategy to alleviate the air pollution, China has also pledged to achieve carbon neutrality in the future. Although the planning of heating system has been studied from national level, bottom-level regional plans are still lacking, which is especially crucial for a huge country as China that has significantly different characteristics across regions. Therefore, this study examined the transitions of the heating sectors towards 2035 and 2050 for 1047 third-level urban units in Northern China. Future changes in heating resources under the low-carbon transitions and future heating demands with the urbanization trend were investigated. Through geographic mapping of resources and demands for county-level units, the regional differences in future scenarios owing to the uneven socioeconomic development of Northern China were presented, which fill in the knowledge gap. By combining supply-side investigations and demand-side forecasts, various roadmaps were evaluated in terms of primary energy consumption, pollution emissions, and economic benefits. Although significant pollution reductions can be achieved in all proposed roadmaps, the clean heating roadmap with the optimal utilization of available resources presents a lower annualized cost than the business-as-usual roadmap, which simply relies on biomass and supplementary sources such as natural gas. In 2050, the primary energy consumption can be reduced to approximately 3 kgce/m2, with an annualized cost of 6 CNY/m2. Balancing the carbon emissions and economic performance, the optimal renovation pattern, together with supply side technologies, were identified in this study.

Roadmap towards clean heating in 2035: Case study of inner Mongolia, China

District heating (DH) is rapidly expanding in China, which consumes a significant share of the national energy and aggravates pollution problems. Among the Northern provinces, Inner Mongolia Autonomous Region (IMAR) has a large area of district heating which relies heavily on coal boilers. In order to achieve the clean heating development goal, this paper first presents a detailed investigation and mapping of the clean heating resources at county levels in the IMAR. Combined with the different energy-saving strategies, four pathways for future DH were proposed. Considering the forecasted scenarios of DH for years 2025 and 2035, this study compares the proposed pathways in terms of primary energy consumption and economic benefits. It was observed that by replacing coal boilers with clean heating resources, the clean heating sources pathway could reduce coal consumption by about 41%, with 33% annual cost savings in 2018 compared with the reference pathway. However, when taking building renovation into account, the economically optimal renovation plan lies between the proposed SHRP and FHRP. The conclusions from this study provide valuable suggestions for clean heating developments in the IMAR and other parts of Northern China.

A Solar Thermal Application for Mongolian Detached Houses: An Energy, Environmental, and Economic Analysis Based on Dynamic Simulations

Ulaanbaatar (Mongolia) is the coldest capital city in the world with approximately 98% of its heating demand satisfied by means of coal-burning stoves. This leads to enormous air pollutant emissions, with Ulaanbaatar being one of the top five most polluted cities in the world. In this study, an innovative solar hybrid heating system for the Mongolian scenario was used, which was based on the operation of a solar field composed of four series-connected evacuated tube heat pipe collectors, coupled with a thermal energy storage. The solar hybrid heating system was simulated and analyzed using the software TRNSYS. The simulations were designed to satisfy the heating demand of a typical single-family detached house located in Ulaanbaatar and were carried out with and without considering the soiling effects on the solar system operation. The overall performance of the proposed plant was compared with those associated with different fossil fuel-based Mongolian conventional heating systems, in order to assess the potential energy, environmental and economic benefits. The results highlighted that the proposed plant allowed for the obtainment of significant reductions in terms of primary energy consumption (up to 34.6%), global CO2 equivalent emissions (up to 52.3%), and operating costs (up to 49.6%), even if the expected return on the investment could be unacceptable.

A carbon-free world – What is Russia’s response?

The article reviews the impact of decarbonization and the global Energy Transition on Russia, analyzing Russia’s position in relation to climate change and decarbonization agenda. Unlike some European countries, Russia has not yet made decarbonization of the energy sector a strategic priority. This is partially explained by the fact that there is a degree of skepticism among the stakeholders in relation to global climate change. Ranking fourth in the world in terms of primary energy consumption and the volume of carbon dioxide emissions, Russia continues to rely on fossil fuels, while its GDP energy intensity remains high amid relatively low energy prices and high capital costs. The share of RES in the energy mic (solar and wind power) is negligible and is not projected to rise above 1% by 2040. However, there is no denying that the Russian energy sector is beginning to feel the impact of increasing global competition, growing technological isolation due to sanctions and ongoing financial difficulties. Quite apart from the impact of global climate change agenda, these factors present Russia with the necessity to produce a new development strategy for its energy sector, which has been and remains crucial for its economy.

Effects of solar field design on the energy, environmental and economic performance of a solar district heating network serving Italian residential and school buildings

In this paper a centralized hybrid renewable district heating system based on the exploitation of solar energy and integrated with a seasonal borehole thermal energy storage is investigated with reference to a 5-year period by means of the dynamic simulation software TRNSYS. The plant is devoted to satisfy the energy demand for heating purposes and domestic hot water (DHW) production of a small-scale district composed of six residential buildings and three schools under the climatic conditions of Naples (south of Italy).Four configurations of the solar field consisting of different combinations of solar thermal collectors (SCs) and photovoltaic/thermal panels (PVTs) are analyzed upon varying both (i) the technology of SCs (flat plate or evacuated tube heat pipe) as well as (ii) the control logic of solar circuit (operation with constant or variable flow rate of heat carrier fluid).The simulation results have been compared with those associated to a conventional decentralized heating system in terms of primary energy consumption, carbon dioxide equivalent emissions and operating costs in order to assess (i) the potential energy, environmental and economic benefits as well as (ii) the impact of solar field design on the overall system performance.

Parametric Analysis of Solar Heating and Cooling Systems for Residential Applications

In this paper, a parametric analysis of two solar heating and cooling systems, one using an absorption heat pump and the other one using an adsorption heat pump, was performed. The systems under investigation were designed to satisfy the energy requirements of a residential building for space heating/cooling purposes and domestic hot water production. The system with the absorption heat pump was analyzed upon varying (i) the solar collectors’ area, (ii) the volume of the hot water storage, (iii) the volume of the cold water tank, and (iv) the climatic conditions. The system with the adsorption heat pump was evaluated upon varying (i) the inlet temperature of hot water supplied to the adsorption heat pump, (ii) the volume of the hot water storage, (iii) the volume of the cold water tank, and (iv) the climatic conditions. The analyses were performed using the dynamic simulation software TRNSYS in terms of primary energy consumption, global carbon dioxide equivalent emissions, and operating costs. The performance of the solar heating and cooling systems was compared with those associated with a conventional system from energy, environmental and economic points of views in order to evaluate the potential benefits.

Effects of the Digital Transition in Passenger Transport - An Analysis of Energy Consumption Scenarios in Europe

The transport sector has rarely seen disruptive evolutions after the diffusion of the internal combustion engine, and today the European mobility is still heavily relying on oil derivates and on private cars. However, there is a significant push in cities towards more sustainable mobility paradigms, and digital technologies are playing a major role in unleashing possible alternatives to a car- and fossil-based mobility. Three major digital trends can be highlighted, with different levels of maturity and some potential synergies among them: Mobility as a Service, Shared Mobility and Autonomous Vehicles. The effects of these trends are also related to the strong push towards electric mobility, which currently appears as the most supported solution by companies and regulators to decarbonize the transport sector. This working paper discusses an investigation of the potential effects of digital transition, by means of a data-driven model for the calculation of the impacts of mobility demand in Europe in terms of primary energy consumption and CO2 emissions. The results show that digitalization may have a positive effect on energy consumption and CO2 emissions for passenger transport, given the strong efficiency improvements expected by technological development in the vehicles powertrains. The benefits are maximized if digital technologies are used towards a collective optimization, by increasing the share of available mobility options. Conversely, if digital technologies are limited to increase the quality of private mobility, the environmental benefits will likely remain very limited. Thus, there is a need of tailored policies supporting the right mobility models to fully exploit the potential benefits of digitalization.

Performance of Different Back-up Technologies for Micro-Scale Solar Hybrid District Heating Systems with Long-term Thermal Energy Storage

In this paper the performance of a solar heating network devoted to satisfying the heating demand of a micro-scale district composed of 6 typical single-family houses and 3 typical schools under the climatic conditions of Naples (south of Italy) is investigated by means of the dynamic simulation software TRNSYS over a 5-year period. The proposed system is composed of a solar collectors array, a short-term thermal energy storage, a long-term double U-pipe vertical borehole thermal energy storage and a heat distribution network. Three different technologies are investigated as back-up devices to be included in the district heating system: (i) a natural gas-fired boiler, (ii) a vapor-compression electric heat pump and (iii) a natural gas-fuelled internal combustion engine-based micro-cogeneration unit.The simulation results are compared with those associated to a conventional heating system in terms of primary energy consumption, operating costs as well as simple pay-back period in order to identify the best option in terms of back-up system and assess the potential energy and economic benefits associated to each technology.

Informing on Best Practices Using Design Builder and RET Screen to Calculate Energetic, Financial, and Environmental Impacts of Energy Systems for Buildings

Buildings represent 32% of total final energy consumption. In terms of primary energy consumption, buildings represent around 40% in most IEA countries (International Energy Agency). For such reason, strategies that lead to energy savings and greenhouse gases reduction are needed.
 This research aims to provide a methodology able to identify the best system configuration from a technical, economic and environmental point of view by using at the same time two energy software: Design builder, which is able to calculate buildings energy needs under dynamic conditions, and RETScreen, which allows feasibility analysis of clean energy projects.
 In order to assess the effectiveness of this operating procedure, a historical building has been modelled and a Combined Cooling, Heat and Power system based on an internal combustion engine has been chosen to ensure environmentally sound way.
 In this study it shows the application of the procedure to a case study as an historical building located in Orte City which is near Rome in Italy; the methodology could get a real preliminary analysis for choose the best active or passive system for improve the energy efficiency and environmental sustainability of existing buildings, also allowing a cost-benefit analysis useful for the concrete realization of the interventions studied.

Comparison of the performance of two different DOAS configurations involving conventional and renewable energies

Spanish building regulations have increased the ventilation rates creating humidity control problems. Dedicated outdoor air systems (DOASs) including a desiccant wheel can dry the ventilation air so that the cooling units are relieved of the latent loads carried by the ventilation air and those generated inside the building. The purpose of this study was to compare the performance of two different DOAS configurations in terms of primary energy consumption under different Spanish climates. The DOAS comprising a desiccant wheel and a conventional refrigeration system was called DOAS-A. The DOAS comprising a desiccant wheel regenerated by solar air collectors and an indirect evaporative cooler was called DOAS-B. The performance of both DOASs was simulated with TRNSYS, and the models were validated with data from experimental setups built at the Miguel Hernández University of Elche (Spain) and at the Technical University of Cartagena (Spain). It was found that the DOAS-B configuration consumed less primary energy than the DOAS-A configuration for commercial use, that is, when the latent load coincides with the supply of solar radiation. These savings reached 68.3% in Seville owing to its high level of solar radiation. It was also found that the net sensible load supplied by the ventilation air to the conditioned space was negative for all climates. This sensible cooling capacity was shown to be greater at lower outdoor dry-bulb temperature and lower latent load.

Absorption and compression heat pump systems for space heating and DHW in European buildings: Energy, environmental and economic analysis

The selection of the proper device for space heating and domestic hot water for a building is crucial to achieve good energy and economic performances. For a single-family house, the most common heating device is the condensing boiler. Solar systems, electric heat pumps and gas driven sorption heat pumps represent suitable alternatives for improving the efficiency. Although the performances of each technology are well known, their ability to operate efficiently in bivalent heating plants depends on several variables and the choice of the most suitable heating system for a specific building is not straight-forward. The aim of this paper is to compare, under conditions typical of the European region, the seasonal performances of six system configurations that are obtained by combining the most commonly used heating technologies. The comparison is carried out in terms of primary energy consumption for three climatic conditions, changing the quality of the building envelope and the emission system typology. Although the results are sensitive to the primary energy factor for electricity, electric heat pumps generally result the most promising technology for conditions with low thermal lift, while gas heat pumps have the higher performances at high lift. Additionally, the systems are compared in terms of yearly CO2 emissions and economic feasibility, finding scattered results among countries, due to large differences in the local energy mix and energy prices.

Thermo-economic sensitivity analysis by dynamic simulations of a small Italian solar district heating system with a seasonal borehole thermal energy storage

Solar energy is a promising option for reducing both energy consumption and harmful gas emissions. Seasonal thermal energy storage is a challenging key technology able to minimize the mismatch between the availability of the solar energy and the thermal energy demand.In this paper, a solar district heating system (basically composed of a solar collectors array, a short-term thermal energy storage (STTES), a long-term borehole thermal energy storage (BTES), an auxiliary natural gas-fired boiler and a heat distribution network) has been analysed by means of dynamic simulations over a 5-year period when serving a district composed of 6 typical single-family houses under the climatic conditions of Naples (center Italy). A sensitivity analysis has been carried out by simulating 27 configurations obtained by varying solar collectors area, volume of STTES and volume of BTES.The simulations results have been compared with those associated to a conventional heating system in terms of primary energy consumption, carbon dioxide equivalent emissions, operating costs as well as simple pay-back period in order to (i) evaluate the potential benefits, (ii) explore the influence of the components size on the system performance and (iii) establish some simple rules for the initial design of the main subsystems.

Opportunities for heat pumps adoption in existing buildings: real-data analysis and numerical simulation

The space heating of buildings represents one of the most important causes of energy consumption in Europe. The necessity to increase the share of renewable energy within the sector is hindered by the difficulty to renew and refurbish the existing building stock. In this context, heat pumps can have an important role in helping increase the renewable share of thermal energy production for the civil sector, in particular in those countries in which the electricity generation mix has large contributions from renewable energy sources. The paper presents a real-data analysis and a numerical simulation to evaluate the opportunity to substitute traditional heat generation systems (natural gas boilers) with air-source heat pumps or hybrid solutions. Three buildings located in Turin (Italy) are taken as case-study, and the hourly profiles of outdoor temperature, water supply temperature and absorbed thermal power are used to simulate four heat generation scenarios, that are compared in terms of primary energy consumption. Results show that (1) the substitution of the traditional natural gas boiler with a heat pump (with backup electric resistance) is always favorable (18% to 32% of primary energy reduction); (2) the influence of water supply temperature of each building on the overall primary energy saving is very high; (3) the adoption of a hybrid system (heat pump and natural gas boiler working alternatively) provides advantages in terms of reduced primary energy consumption only if the required supply water temperature is high. Further studies will investigate the economic aspects and will introduce comparisons with condensation natural gas boilers.

The Potential of Hydrogen Enriched Natural Gas deriving from Power-to-Gas option in Building Energy Retrofitting

This paper deals with the role of Hydrogen enriched Natural Gas (H2NG) in Hybrid Energy Systems for energy refurbishment purposes. In detail, three different plant layout options were investigated. A photovoltaics (PV) array and two-stage electric heat pump (EHP), a hybrid photovoltaic thermal solar collectors combined to gas heat pump (GHP) fuelled with H2NG, and a CHP fuelled with H2NG connected to a two-stage EHP were compared. The required receiving surfaces of PV array were estimated for three different direct normal irradiation (DNI) values in Italy in order to assess how the available roof surface affects the layout choice. A sensitivity analysis was carried out with varying the building power to heat ratio (PTHR) and the hydrogen volumetric fraction in the H2NG mixtures to assess the primary energy consumption (PEC) and renewable energy fraction. When feasible, the PV+EHP shows the best performance in terms of PEC with a solar energy share equal to 65%. In other cases, the PV/T+GHP fuelled with H2NG @30%vol. can be suitable for PTHR higher than 0.2 approximately. Furthermore, the third layout CHP+EHP is not competitive with the other solutions but, it is the best option where no roof surfaces are available for PV or PV/T installation.

Building energy performance prediction using neural networks

The energy in buildings is influenced by numerous factors characterized by non-linear multi-interrelationships. Consequently, the prediction of the energy performance of a building, in the presence of these factors, becomes a complex task. The work presented in this paper utilizes risk and sensitivity analysis and applies artificial neural networks (ANNs) to predict the energy performance of buildings in terms of primary energy consumption and CO2 emissions represented in the Building Energy Rating (BER) scale. Training, validation, and testing of the utilized ANN was implemented using simulation data generated from a stochastic analysis on the ‘Dwellings Energy Assessment Procedure’ (DEAP) energy model. Four alternative ANN models for varying levels of detail and accuracy are devised for fast and efficient energy performance prediction. Two fine-detailed models, one with 68 energy-related input factors and one with 34 energy-related input factors, offer quick and multi-factored estimations of the energy performance of buildings with 80 and 85% accuracy, respectively. Two low-detailed models, one with 16 and one with 8 energy-related input factors, offer less computationally intensive yet sufficiently accurate predictions with 92 and 94% accuracy, respectively.