Heating Costs Research Articles

Natural refrigerant mixtures in low-charge heat pumps: An analysis of the potential for performance enhancements

The study investigated the characteristics of different natural refrigerants and their mixtures in a residential heat pump with low refrigerant charge. Three main evaluation criteria were utilized for comparing different mixtures: Coefficient of Performance (COP), Volumetric Heating Capacity (VHC), and a newly proposed indicator, the heating capacity at charge limit. Propane was used as a reference refrigerant. It was found that some mixtures significantly improved both COP and the heating capacity at charge limit while maintaining similar volumetric heating capacity and operating conditions. Alternative multi-criteria decision-making techniques were adopted to rank the best refrigerant mixtures. Mixtures rich in Dimethyl Ether (DME), such as DME-CO2 [0.96-0.04] and DME-Propylene [0.75-0.25] were found consistently among the best options. Those were followed by Propylene-rich mixtures such as Propylene-CO2, Propylene-Isobutane and Propylene-Butane. The levelized cost of heat (LCOH) could be improved by up to 12 %. To accelerate the transition to natural refrigerants, without compromises on efficiency and costs, further research and certification activities on non-fluorinated refrigerants based on Dimethyl Ether (R-E170), CO2 (R-744) and Propylene (R-1270) are recommended.

Performance comparison of air source heat pump coupling with solar evacuated tube water heater and that with micro heat pipe PV/T

Air source heat pump (ASHP) has been generally regarded as energy saving devices for winter heating, yet for low-income households, the operational costs for heating in low-temperature conditions may be prohibitively high. Solar evacuated tube water heater (SETWH) and photovoltaic/thermal are economical solar energy conversion devices. Integrating them into ASHP has been proven globally to significantly reduce heating costs. However, a performance comparison between the SETWH combined with ASHP (SETWH-ASHP) and of micro heat pipe photovoltaic/thermal (MHP-PV/T) combined with ASHP (MHP-PV/T-ASHP) heating systems remains unexplored. Therefore, for a 120 m2 building with underfloor heating water pipe, SETWH-ASHP and MHP-PV/T-ASHP heating systems were respectively developed on the TRNSYS software platform. Their accuracy was confirmed using prior experimental data, followed by performance simulation for the heating season. The result is that MHP-PV/T-ASHP heating system outperformed SETWH-ASHP heating system, showing a 19 % increase in solar fraction, a 2.2 boost in system energy efficiency ratio, a 12.3 % rise in primary energy saving rate, a 0.9-year shorter payback period, and a reduction of 494.7 kg in CO2 emissions over the heating season. The results offer practical guidance for the promotion and application of heating systems that combine efficient and low-cost solar conversion devices with ASHP.

АВТОМАТИЗАЦІЯ ПРОЦЕСІВ КЕРУВАННЯ МІКРОКЛІМАТОМ ЖИТЛОВИХ ПРИМІЩЕНЬ

This paper is devoted to the research of the important issue of increasing the efficiency and optimization of microclimate management processes in residential premises. The purpose of this study is to create an automated system for accurate setting and control of the main parameters of the microclimate in the room, which will make it possible to increase comfort and energy efficiency. To achieve the task, the Arduino platform is used, which is an open hardware and software system with a wide range of opportunities for developing embedded systems. The study includes an analysis of the principles of creating a programmable timer using the Atmel AVR microcontroller, covering the selection of necessary hardware and modules, software development and user interface. The main functions of the programmable timer provide the ability to set a satisfactory microclimate according to the individual needs of the user and adjust parameters such as temperature, atmospheric pressure and humidity. The research results confirm that the developed programmable timer based on the Arduino platform provides effective control of the microclimate in the living room. Implementation of such a system will reduce heating and air conditioning costs, increase indoor comfort, and reduce overall energy consumption.

Modeling of a Solar Thermal Plant to Produce Hot Water and Steam for a Brewery Factory

The environmental impact caused by the intensive exploitation of fossil fuels to generate heat and electricity has already reached a critical level. Also, as the industrial sector is the largest energy consumer, mainly in the form of heat, it has then become compulsive to implement the use of renewable solar heat in industrial processes, such as those found in the food processing and beverages industries, which do not require high temperatures. Consequently, this study examines the viability of supplying heat as hot water at 80 °C and saturated steam at 160 °C to a medium-sized brewery factory through a hybrid solar plant composed of flat plate and parabolic trough collectors and sensible thermal energy storage. The study was conducted numerically using the meteorological conditions of a city different from that where the factory is located because it benefits from higher insolation levels. The mean annual solar fractions achieved were 49.9% for hot water production and 37.3% for steam generation, at a levelized cost of heat of 0.032 USD/kWh, which can be considered competitive if compared against the values reported in other similar solar projects. Also, the decrease in fossil fuel consumption allowed an annual reduction of 252 tons of carbon dioxide emissions.

Uniform Modeling of Heat Production Costs in Single-Family and Multi-Family Houses

To ensure a fair and extensive comparison of different heating systems four representative buildings including their heat demand for space heating and domestic hot water were defined. A model for the heat production costs has been developed based on existing methods like the VDI 2067 part 1 [1] and the simplified approach for the calculation of the "Levelised Cost of Heat" (LCoH) of the IEA SHC Task 54 "Price Cost reduction in solar thermal systems" [2]. The developed model includes the costs of purchase, installation, operation, maintenance and disposal and was implemented in an EXCEL calculation tool which enables the calculation of the total life cycle costs (LCC), the levelized cost of heat (LCoH) and the CO2 emissions over the lifetime of the system.

Energetic and financial evaluation of a district heating network under varying supply temperatures and booster technologies

Low-temperature district heating (LTDH) enables the use of various renewable energy sources, reduces heat losses and increases the energy efficiency of the distribution network. LTDH is especially applicable in energy-efficient buildings as the supply temperature for space heating can be reduced. However, urban areas consist of energetically refurbished and non-refurbished buildings. In these scenarios a LTDH network with a central heat pump (HP) and decentral booster units, such as a booster HP or electrical heater, can be a solution. This study investigates and compares the energetic performance and levelized cost of heat (LCOH) of eight concepts for refurbished and non-refurbished buildings for a district heating network in the city of Ghent, Belgium. The simulations consider supply temperatures ranging from 10 °C to 75 °C. Results show that the primary energy use is lowest when using booster HPs, for both refurbished buildings (402 MWh/year) and non-refurbished buildings (139.6 MWh/year). The LCOH, however, is lowest when booster units are not necessary as the LCOH is mainly driven by the high investment cost of the network and the booster units. This results in a LCOH of 213 €/MWhth for non-refurbished buildings at a network temperature of 75 °C and 297 €/MWhth for refurbished buildings at 55 °C.

A novel heating strategy and its optimization of solar–air source heat pump heating system for rural buildings in northwest China

In the rural areas of Northwest China, the utilization of clean and renewable energy is deemed a crucial measure for reducing building energy consumption and environmental pollutant emissions. This paper focuses on constructing a simulation platform for a solar-assisted air source heat pump heating system. A rural residential building in Yongshou County, Shaanxi Province, serves as an illustrative example. A novel flexible temperature control method with a feedback controller in sub-area and period is proposed in this paper, alongside the selection of three distinct objective functions aimed at optimizing the heating system. The simulation results indicate an average temperature of 17.0 °C throughout the heating cycle, with a peak temperature of 18.7 °C. Moreover, the solar fraction is measured at 25.11%, underscoring the significance of collector area and heat storage tank volume as primary factors in system design. The results also demonstrate that across various optimization objectives, the life cycle cost optimization scheme yields greater economic benefits, while the target building unit heating cost optimization scheme boasts the shortest static payback period and lowest unit heating cost. Conversely, the solar fraction optimization scheme stands out for its superior environmental benefits. These findings offer valuable insights for the design of heating systems tailored to diverse objectives.

The potential of agricultural and livestock wastes as a source of biogas in Vietnam: Energetic, economic and environmental evaluation

Many economies, including Vietnam, have substantial potential for producing energy from agricultural waste. However, the analysis of using agricultural waste as a renewable energy source and its associated economic and environmental benefits remain unclear. This study aims to a) estimate trends in greenhouse gas (GHG) emissions from livestock and crop residue burning; b) evaluate the environmental benefits of using biogas in substitution for coal, wood, and liquefied petroleum gas (LPG) under various scenarios; c) assess the economic viability of a household-scale biodigester, and d) propose recommendations for the effective exploitation and utilization of biogas. GHG emissions were calculated for livestock and crop residue burning (CRB) using activity data and emission factors. The environmental analysis was conducted to understand the role of biogas in reducing GHG by assuming 100 % exportation of biogas in substitution for fuels for electricity and heat generation. The economic benefits were assessed through internal rate of return (IRR), net present value (NPV), payback period, levelized cost of electricity (LCOE), and levelized cost of heat (LCOH). Results indicate that, between 2000 and 2050, CO2-eq emissions will rise from 38.5 to 95.2 Mt. Environmental analysis shows that replacing coal or wood with biogas can bring more benefits than LPG, in reducing GHG emissions by 68.2 and 67.9 Mt CO2-eq in 2020 and by 148.4 and 147.9 Mt CO2-eq by 2050. Economic analysis shows that investment in biodigesters is most viable when replacing LPG with biogas, with NPV = $4878, IRR = 57.2 %, PBP (simple) = 1.7 years, and LCOH = $0.029/kWh.

Environmental and economic impacts of photovoltaic integration in concentrated solar power plants

This study conducted an environmental and economic assessment of an innovative hybrid energy generation system, a CSP+ plant, which integrates photovoltaic (PV) panels in a concentrated solar power (CSP) setup. The CSP+ concept uses a beam splitter that transmits part of the incident solar spectrum towards the PV cells for electricity generation and reflects ultraviolet and infrared light to the receiver tube for heating. This system allows more efficient use of solar radiation in a compact system with optimal efficiency.The environmental impacts were assessed using the life cycle assessment (LCA) methodology, focusing on the climate change impact category. The economic impacts were calculated using the levelized cost of electricity (LCOE) and the levelized cost of heat (LCOH). Both assessments considered a cradle-to-grave perspective in three scenarios (SC). SCI considered only electricity generation, while SCII involved the combined production of electricity and heat. These scenarios were compared to conventional CSP and PV technologies (SCIII) and benchmark values from the literature.The LCA results showed SCII was the most preferable: the impacts on climate change were reduced by up to 83% for electricity production and up to 97% for heat production compared to benchmark values. In SCII, the LCOE and the LCOH in the CSP+ plant were lower than the average benchmark values, with reductions of up to 70% for electricity and 40% for heat. The sensitivity analysis showed that the environmental performance was strongly influenced by the operating lifetime. For economic performance, the weighted cost of capital was the most influential factor.

Sustainable Heat Supply for Greenhouses with Heatpumps

The heating of greenhouses in Germany is yearly responsible for the emission of about 3 million tCO2eq. In the small horticultural city of Straelen in North-west Germany, the possibility to partially replace the heat supply of greenhouses with heat pumps instead of CO2-intensive coal and oil boilers has been investigated. Different scenarios based on the power of the heat pump and the type of source (air or ground) have been simulated and compared economically and ecologically. Over the lifetime of the whole system, the levelized cost of heat for a combined heat pump & gas boiler heating system is lower than the reference case (coal & gas boilers). The installation of a heatpump covering at least 70% of the yearly heat demand would reduce the CO2-emission from minimum 70%.

Conversion of boiler houses to alternative fuel

THE PURPOSE. To justify the need to transfer boiler houses from fuel oil to furnace domestic fuel. METHODS. Comparative studies of the main indicators of the quality of fuel oil and domestic heating oil (DHO) (heat of combustion, kinematic viscosity, flash point, pour point, ash content, humidity, sulfur content) were carried out. The environmental parameters of pollutants formed during the combustion of fuel oil and domestic stove fuel are calculated and compared with the values regulated by the EkoNiP 17.01.06-001-2017 "Environmental protection and nature management. Requirements of environmental safety" and TCU 17.02-XX-2019 "Environmental protection and nature management". RESULTS. As a result of comparative studies of the main indicators of the quality of fuel oil and furnace household fuel (PBT), it was shown that combustion in PBT boilers in comparison with fuel oil is preferable in terms of environmental consequences in terms of emissions into the atmosphere. As a result of the comparative analysis, it was found that during the transition from fuel oil to furnace household fuel, compliance with the basic environmental standards regulated by these regulatory documents is ensured by reducing by 70 times the amount of sulfur dioxide released into the atmospheric air during 10 days of burning furnace household fuel, as well as reducing the concentration of this type of emission by 72.5 times. When switching from fuel oil to furnace household fuel, pollution and equipment wear are also reduced due to the ash content index for furnace household fuel being 7 times lower than that of fuel oil, as well as a 2-fold reduction in the formation of soot and 70-fold reduction in sulfur dioxide during ten-day use of a new reserve type of fuel. CONCLUSION. Thus, as a result of experimental and calculated studies, it was shown that combustion in DHO boilers in comparison with fuel oil is preferable in terms of environmental consequences in terms of emissions into the atmosphere, reducing corrosion, stopping boilers for repairs, reducing fuel heating costs to facilitate transportation, reducing steam and fuel costs. When switching from fuel oil to furnace household fuel, pollution and equipment wear are also reduced due to the ash content index for furnace household fuel that is 7 times lower than that of fuel oil, as well as a 2-fold reduction in the formation of soot and 70-fold reduction in sulfur dioxide during ten-day use of a new reserve type of fuel.

Analysing the Techno-Economic Viability of Different Solar Heating Systems in South African Beverage Plants

With ongoing real-term reductions in the cost of renewable energy technologies, opportunities to reduce carbon emissions within industry have improved. While the South African industrial sector has been investing in photovoltaics to meet electricity requirements, little has been done to replace fossil fuels used for the generation of process heat, representing two-thirds of the energy consumed. While previous studies have demonstrated the benefits and limitations of solar thermal (ST) energy solutions for industrial applications, recent developments in high-temperature heat pumps (HTHP) offer opportunities for novel configurations, including the use of renewable energy like photovoltaics (PV). This study compares the techno-economic benefits of solar thermal energy systems with PV-supported HTHP systems within the South African beverage sector. After a general consideration, simulation calculations are presented for selected applications. The cost of heat is determined for PV-heat pump systems operating on a stand-alone basis and with heat storage. The study finds that the levelised cost of heat of US$0.050-0.073/kWhth is at least twice that of coal-fired steam boilers. The study, therefore, calls for further work on optimising systems minimising steam requirements, and thereby improving the economics of heat pumps and for a coordinated effort to support the development and financing of high-temperature heat pumps for industrial applications.

Energy-economic-environmental analysis of a net-zero energy greenhouse with fan-coil units and hot-water pipes: Experiment and modelling

This study analysed the performance of a hot-water pipe (HWP) and fan-coil units (FCUs) in controlling microclimate conditions in a net-zero energy greenhouse (NZEG). The performance of a previously developed TraNsient SYstem Simulation (TRNSYS) model for the NZEG was enhanced to include a crop model and several HWP emission standards, and the improved TRNSYS model was used to analyse heating, ventilation and air-conditioning (HVAC) systems for different greenhouse sizes in the Republic of Korea. Further, an economic analysis was conducted. The model validation showed excellent agreement between the measured and simulated values, with Nash-Sutcliffe efficiency of 0.98. The presence of crop in the simulation model reduced the total heating load by 14.5 MWh and increased the cooling load by 4 MWh. The capacity of the FCU was increased as the outside temperature rose from 33.4[Formula: see text] to 36.4[Formula: see text] in summer, and the diameter of the HWP was decreased from 25A to 10A as the outside temperature rose from −21.7[Formula: see text] to −12.2[Formula: see text] in winter to maintain the greenhouse at the desired temperature of 15[Formula: see text]. Notably, the payback period was reduced by 9 years when the annual savings in heating energy costs and revenue from carbon trading were considered as a part of the net economic cash flow.

Investigating inefficiencies in the German rental housing market: The impact of disclosing total costs on energy efficiency appreciation

Energy efficiency and renewable energy are key pillars of the energy transition that is high on the political agenda of governments in face of the climate crisis. Germany, however, is underperforming in its emissions reduction goals. There is still room for improvement, especially in the building sector – but this is often associated with high upfront investments. There is evidence that the market for energy efficiency in the German rental housing market is inefficient, resulting in underinvestment. To investigate these inefficiencies, this study estimates a hedonic pricing model combined with a total-cost-of-use perspective based on the observation of warm rents for a sample of 3,903,473 rental offers from 2014 to 2021. In a “perfect world”, the effect of the energy performance score given in energy performance certificates as an indicator of energy consumption or demand, respectively, is expected to be zero, as corresponding costs are already included in the warm rent. If the coefficient is significantly different from zero, it can be interpreted as measure for inefficiencies. The study further investigates whether disclosing heating costs in real estate advertisements could lead to a better appreciation of energy efficiency in the rental market and thus contribute to closing the information gap. Results show that the market for energy efficiency is indeed inefficient; however, the disclosure of full information can help to overcome these inefficiencies. These results lead to several important policy implications.

A METHODICAL APPROACH TO REDUCING HEAT ENERGY EXPENDITURES FOR BUILDING HEATING

The work provides a method of preventing the consumption of heat energy for heating the building. It is noted that the energy statistics of Ukraine foresee an increase in the use of primary energy resources in the period 2020–2030 mainly due to energy saving, which, in turn, will ensure a 30-40% reduction in emissions of harmful substances into the atmosphere and stabilize greenhouse gas emissions. In order to substantiate the ways of reducing money costs for electricity and heat consumption, certain measures are proposed in the work, which demonstrate the greatest economic effect in the shortest time. The evaluation of the quality of thermal protection of the building's enclosing structures was carried out. The analysis of thermograms of enclosing structures based on infrared scanning of surfaces is presented. The thermal imaging survey was carried out in two stages. With the help of a thermal imager, at the first stage, a scan of the enclosing structures was performed in order to identify areas of the enclosing structures that have different temperature fields. Based on the analysis of the thermograms of the previous scan, a program of detailed examination of the areas with temperature anomalies is planned and the reasons for their appearance are clarified. Based on the conducted research, recommendations are given to increase the combined heat transfer resistance of enclosing structures in order to prevent heat energy costs for heating the building.

Techno-economic analysis of latent heat thermal energy storage integrated heat pump for indoor heating

Latent heat thermal energy storage (LHTES) implemented in residential heating systems has attracted attention for its role in peak/load shifting. A novel layout integrating LHTES with a heat pump is proposed to store low grade heat during off-peak demand period, later used as heat source for the heat pump during on-peak demand period. This novel layout is assessed according to different seasons, LHTES height-to-diameter (H/D) ratios, mass ratios of inflow water to radiator return water, and levelized cost of energy (LCOE). The results show that an overall increased amount of power input is required when utilizing LHTES, while it can shift 2.8–3.6 kW electricity from on-peak to off-peak. The case with an H/D ratio of 1.7 shows slight reductions in heating costs and LCOE as compared to a H/D ratio of 0.6. Considering heating costs, a mass ratio of 50 % performs better in December 2022 and a mass ratio of 10 % performs better in January 2023 due to different operating conditions. The heating costs of the integrated system are 1.0 %–2.1 % higher than those of the typical system due to limitations in the rated capacity of the heat pump and lower effectiveness of the shell-and-tube heat exchanger.

Indoor environmental quality in schools: NOTECH solution vs. standard solution.

In many Danish schools, the indoor environmental quality (IEQ) is challenged and studies document a poor IEQ in a majority of existing schools. Municipalities cannot afford comprehensive renovations and expensive mechanical ventilation solutions, hence public schools often suffer from poor indoor environment conditions. This study tests a new façade based, demand-controlled ventilation solution called NOTECH in the renovation of school. The study tests NOTECH vs. existing mechanical ventilation solution, comparing performance of both solutions at Skovbrynet Skole in Denmark. The project investigates the effect of the NOTECH solution in a primary school classroom, comparing it to a similar classroom with conventional, mechanical ventilation. Methodically, indoor environmental quality and energy performance is monitored in the two identical classrooms during one school year 2018 - 2019. The results show that both systems keep the conditions within acceptable limits and CO2 levels below 1000 ppm, which is the requirement according to the Danish Building Regulations. In terms of costs, the NOTECH system has a lower overall cost than the mechanical ventilation system, with total estimated costs for installation, heating, electricity and maintenance amounting to approximately 35% of the mechanical system's costs. Finally, the results show that the NOTECH solution has a smaller embedded CO2 footprint for building materials, reducing the estimated carbon load by 95% compared to the mechanical ventilation solution. While the performance of the both systems complies to the Danish Building Regulations, the indoor environmental quality between systems differs significantly. Results showing a higher air-temperature and lower relative air-humidity in the classroom with mechanical ventilation during winter and lower CO 2 levels in the mechanically ventilated classroom during winter and summer. Costs for implementation, energy consumption for heating and CO 2 footprint for building materials are significantly lower for the NOTECH solution, compared to the mechanical solution.

Research on day-ahead optimal dispatching of virtual power plants considering the coordinated operation of diverse flexible loads and new energy

Large-scale new energy access to the power grid poses significant challenges to its stable operation. Differentiated user-side power consumption patterns further widen peak-valley differences in power demand. This paper focuses on operation scheduling problems of virtual power plants with coordinated optimization of diverse flexible loads and new energy, through efficient aggregation and optimization control of new energy and demand-side resources, improving power supply and demand mismatch. Firstly, Long Short-Term Memory and Latin Hypercube Sampling were employed for predicting the day-ahead output of wind and photovoltaic power. Secondly, wind and photovoltaic power, batteries and a pumped storage plant were aggregated into a virtual power plant, and the day-ahead optimization scheduling model was constructed considering system operation costs, energy curtailment costs and demand response costs. Finally, a simulation analysis was conducted. The results show that when large-scale new energy accesses to the power grid, traditional “Generation varies with Load” regulation modes will cause massive energy waste, while the “Generation-Load Interaction” regulation mode can achieve the linkage optimization between the generation side and the demand side, enhancing the system acceptance of new energy. Demand response can optimize users’ power consumption behaviors, reducing the charging costs by 52.13 % and heating costs by 0.84 %.

Research on the optimization of the clean heating system for regional residential buildings based on the multi-objective optimization strategy

For the residential building district heating (RBDH) system, choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency. In this study, three climatic regions in China were selected, namely, a hot summer and cold winter region, cold region, and severe cold region. Among them, Nanjing, Tianjin, and Shenyang were selected as typical representative cities in the hot summer and cold winter region, cold region, and severe cold region, respectively. Taking the levelized cost of heat (LCOH) as the economic evaluation index and considering the carbon emission cost of the system operation, the energy consumption and the CO2 emissions were analyzed. TRNSYS software was used to simulate and analyze the system performance. The multi-objective optimization based on a genetic algorithm was proposed to optimize system parameters. From an economic point of view, the SA system was suitable for the hot summer and cold winter region, the SAS system was suitable for the cold region, and the SE system was suitable for the severe cold region. The operation control strategy based on quality adjustment can reduce heating energy consumption and maintain indoor temperatures at approximately 20°C. The proportion of clean energy heating in the optimized heating system decreased after the multi-objective optimization strategy. However, the initial investment and maintenance costs of the system were reduced, which reduced the LOCH of the system. Therefore, the multi-objective optimization strategy can effectively reduce the heating costs.

Economic optimization of exterior wall insulation in Chinese office buildings by coupling artificial neural network and genetic algorithm

Envelope insulation is an essential measure to reduce building energy consumption and is the focus of many building energy codes. In China, the current standard (GB 55015-2021) only specified limit values for the thermal conductivity (U) of the exterior walls, and it ignored variations in building characteristics and internal parameters. Therefore, it is difficult for architects to quickly determine the exterior wall U-value in building design and retrofit. To address this issue, the exterior wall U-values of office buildings in China were economically optimized by TRNSYS, ANN, and GA. To begin with, the effect of enhancing exterior wall insulation on the heating and cooling energy consumption of office buildings was investigated by TRNSYS software, taking into account variations in building characteristics. Moreover, the exterior wall U-values of office buildings were optimized by coupling ANN and GA. The results showed that the design values of the GB 55015-2021 did not achieve the optimal results in China, and the most economical exterior wall U-value was 0.24 W/(m2·K) in Harbin, 0.24 W/(m2·K) in Beijing, 0.42 W/(m2·K) in Changsha, 1.82 W/(m2·K) in Guangzhou, 0.66 W/(m2·K) in Kunming. Compared with the pre-optimization, the annual life cycle cost of building heating and cooling reduced by 0.96 % in Harbin, 2.07 % in Beijing, 1.44 % in Changsha, 1.68 % in Guangzhou, and 7.37 % in Kunming. In addition, variations in building parameters should be considered in the design phase of new buildings or in the renovation of old buildings, such as internal heat gain, which may lead to different optimal results.