Use Of Heat Research Articles

CO2 Emissions Inventory and Its Uncertainty Analysis of China's Industrial Parks: A Case Study of the Maanshan Economic and Technological Development Area.

The Chinese government has pledged to peak carbon emissions by 2030 and achieve carbon neutrality by 2060. Industrial parks are the key to achieving the carbon peak and neutrality in industrial sectors. Establishing the CO2 emissions inventory is the first step to achieve the carbon peak in industrial parks. In this study, a comprehensive CO2 emissions inventory was established for industrial parks, including three parts: energy consumption, industrial process, and waste disposal. We considered scope 1, 2, and 3 emissions and established an uncertainty analysis framework. Accordingly, scope 1 covered the emissions within the park boundary, scope 2 emissions covered those resulting from electricity and heat usage inside the boundary, and scope 3 included those indirect emissions beyond the boundary. The Maanshan Economic and Technological Development Area (MDA), a typical booming national eco-industrial park of China, was chosen for this case study. The results showed that the MDA CO2 emissions increased yearly, from 376,836.57 tons in 2016 to 772,170.93 tons in 2021. From the industrial structure perspective, heavy industry contributed the highest emissions. By dividing the emissions into scope 1, 2, and 3, scope 2 could be identified as the largest emissions source. In addition, we conducted inventory uncertainty analyses incorporated by activity levels, emissions factors, and unspecific factors. Overall, these results may promote the establishment of greenhouse gas accounting standards for Chinese industrial parks.

Performance Evaluation of a Nearly Zero-Energy Office Building in Temperate Oceanic Climate Based on Field Measurements

This field study evaluated the building performance of a nearly zero-energy office building near Brussels, Belgium, located in the temperate climatic zone. The building’s thermal comfort and energy parameters were monitored from May 2018 to April 2019. The time-integrated thermal discomfort, primary energy use, and greenhouse gas emissions from the building were then analyzed using the monitored data. The case study evaluated the HVAC system performance with an air-cooled chiller with water cooling coils and a water boiler with water heating coils. The findings indicated an indoor overheating degree of 0.05 °C and an indoor overcooling degree of 0 °C for the observed period. The building’s primary cooling energy use was found to be 37.54 kWhPE/m2.a and primary heating energy use was found to be 46.08 kWhPE/m2.a for the monitored period. The cooling and heating greenhouse gas emissions were 10.14 kg.CO2e/m2.a and 8.34 kg.CO2e/m2.a, respectively. The observed data also indicated that the HVAC system in the building was operational throughout the monitoring period from May 2018 to April 2019, including a 24/7 schedule. Finally, the paper provided implications for practice and future work based on the study findings.

Operation optimization of a solar collector integrated with phase change material storage heating system

Making full use of renewable energy for building heating is inevitable if energy structures are to be transformed and emissions are to be reduced. A solar collector integrated with a phase change material storage heating (SC-PCM) system is a promising distributed building heating technology. However, the feasibility and economic efficiency of the system in practical applications have rarely been studied. In this study, on-site measurement and model development for a SC-PCM system constructed for a three-storey office building in Tianjin were carried out. The accuracy of a self-developed phase-change heat transfer module, Type 668, and of a TRNSYS simulation model was verified by data from a 45-day on-site measurement. The mean relative error (MRE) of the on-site measurement and simulated data for the heat supply of the phase-change module was 7.8%. The MREs for indoor temperature and total daily heat supply of the entire SC-PCM system were 2.2% and 8.3%, respectively. The verified model was then used for a system-optimization study. Nine control strategies designed by the orthogonal method were compared, and it was proved that the control strategy VI (3-WV conversion condition: T3 < 43 °C close, T3 > 48 °C open; 3-PDV set value: 36 °C; EHF heating period: 23:00–5:00) is the optimal strategy for the current SC-PCM system. The energy consumption of strategy VI was 21,470 kW·h for 28 days, 21.4% less than that of the original strategy. A four-factor, three-level orthogonal design test was conducted to determine the effects of various parameters on a nonspecific SC-PCM system. It was concluded that the area of the solar collector (SC) has the greatest impact on indoor temperature, while the power of the electric heating furnace (EHF) has the greatest impact on the levelized cost of heat (LCOH). The TRNSYS model was used in combination with optimization solution tool GENOPT to obtain the optimal parameters of the system for different cities in China. The LCOHs in Tianjin and Shenyang were 16.4% and 17.5% lower, respectively, than the local flat electricity prices. It was demonstrated that the system has great application potential in areas with high heat demand and a significant peak valley power policy.

Heating energy implications of utilizing gas-phase air cleaners in buildings’ centralized air handling units

Ventilation systems are a vital component of buildings in order to ensure a healthy and comfortable environment for the occupants. In cold climate regions, ventilation systems are responsible for approximately 30% of building heat losses. In addition to outdoor pollutants (particulate matters, NOX, etc.), indoor emissions from materials in the form of gas pollutants and emissions from occupants are the principal indoor air quality metrics for securing an acceptable indoor concentration level. Therefore, it is of great interest to study the use of gas-phase air cleaning technologies in low-energy centralized air handling units. This study focused on reducing buildings' heating requirements by recirculating indoor air while maintaining an acceptable indoor air quality level. The heating performance of a typical residential and office building in the central Swedish climate was studied by dynamic building simulations. Indoor air recirculation rates and air changes per hour were the key parameters considered during the simulation of the building's heating demand and indoor gaseous air pollution concentration. We found that introducing indoor air recirculation reduces buildings' heating demand depending on the air change rates per hour. The results show that it is possible to reduce the energy use for heating by less than approximaytely 10% and 20% for residential and office buildings, respectively and maintain acceptable indoor air quality by using gas-phase air cleaning.

Decentralized ventilation unit for window frame integration

Swedish National Board of Housing, Building and Planning reported in “Energi i bebyggelsen” that 80 % of the detached houses in Sweden were under-ventilated, and had a flow of 0.23 l/(s·m2) on average instead of, by the code, required 0,35 l/(s·m2). Well known concerns here are lacking indoor environmental quality and a risk of moisture problems in certain rooms and in the envelope. The naturally ventilated houses have a higher airflow at low outdoor temperatures which increases the energy use for heating. Adding proper ventilation to all Swedish detached houses could according to Besmå’s pre-study “Potential för energieffektivisering i småhus (2019)” increase the annual energy need by 5.5 TWh. Many of these use electric heating resulting in a heavy pressure on the electricity production and distribution. One way to solve this problem is to install mechanical ventilation with heat recovery. Installing such system in older houses is however often costly and often carries technical and practical problems. Ducts must be installed in every room in the building, requiring space which often leads to reconstruction of walls and ceilings. Another way to solve this is reinforce the existing ventilation in the house with a decentralised ventilation unit with heat recovery. The technical solution is to mount several smaller ventilation unit with heat recovery in the building skin in order to ventilate individual rooms. The solution does not require any ducts to be installed. This simplifies the installation and reduces the maintenance. In this report we study a decentralised ventilation unit with heat recovery intended to be installed in window frame to lower the cost of the combination of ventilation and window renovation. In this report we measure draft, short-circuiting between inlet and outlet air, air mixing in the room, noise and heat recovery efficiency of the ventilation unit. The results show that no draft and no short-circuit occurs and that the mixing of the air in the room is high and an efficiency of the heat recovery of approximately 70 %.

Analysis of Major Temporary Electrical Equipment Consumption and Usage Patterns in Educational Buildings: Case Study

The energy use patterns of electrical appliances are more difficult to predict than energy use for heating, ventilation, and air-conditioning (HVAC) and lighting, as: (1) there are large varieties of electrical equipment (e.g., appliances, vending machines, etc.) in buildings and each serves a different function; thus, their energy consumption patterns are difficult to predict; (2) electrical appliances are scattered across buildings, most are not permanently fixed to a location, and they consume much energy. Appliances are also not centrally controlled, such as HVAC and lighting. Thus, energy consumption patterns are more difficult to predict. In addition, electrical appliances consume significant amounts of energy to influence energy consumption volatility. This case study focuses on understanding the energy consumption patterns of electrical appliances in educational buildings. This research analyzes the electrical appliances and energy consumption data from institutional buildings and the factors that drive energy consumption. The analyses show that: (1) energy consumption patterns are dependent on building characteristics and use; (2) the number of appliances in a building influences the peak electricity consumption; (3) vending machines and fridges consume significant amounts of electricity; it has been proven (by minimum building energy loads) that buildings that have more vending machines have significantly higher minimum loads than no or fewer vending machines; and (4) the energy-saving potential from desktops and monitors rose to 60 kWh during lunchtime and 500 kWh at night.

High frequency flow and temperature measurements of domestic water in two office and education buildings

For a long period, the energy use for domestic hot water (DHW) in non-residential buildings has been neglected. As energy use for space heating, ventilation, and lightning has been reduced through the years, the energy share for DHW production has increased. With today’s focus on energy efficient buildings, the DHW systems must not be left behind the other fields to obtain a holistic approach to energy efficient buildings. To develop more energy efficient DHW systems for non-residential buildings, more knowledge is needed regarding draw-off durations, flow rates, and water temperatures from different draw-off types.This paper presents high frequency measurement results in two Danish office and educational buildings, which show that three DHW systems only utilize between 3.4 and 7.5 % of the total energy used for DHW production. Above 85 % of the total energy use is lost from the recirculation circuit to secure a high hot water temperature at the draw-off point. However, temperature measurements at the draw-off points show that a significant share of the heat is lost from pipes not covered by recirculation. One reason is draw-off durations are approximately 50 % of the time below 10 s at washbasins and kitchen sinks. Another reason is actual maximum flow rates are far from the calculated design flow.The high frequency measurements at multiple draw-off points give essential knowledge of use patterns for washbasins, kitchen sinks, and service sinks in non-residential buildings. This knowledge can contribute to developing energy efficient DHW systems and new types of DHW production.

Economic, technical, and environmental evaluation of retrofitting scenarios in a full-scale industrial wastewater treatment system

The use of mathematical models is a well-established procedure in the field of (waste) water engineering to “virtually” evaluate the feasibility of novel process modifications. In this way, only options with the highest chance of success are further developed to be implemented at full-scale, while less interesting proposals can be disregarded at an early stage. Nevertheless, there is still lack of studies, where different plant-wide model predictions (effluent quality, process economics, and technical aspects) are comprehensibly verified in the field with full-scale data. In this work, a set of analysis/evaluation tools are used to assess alternative retrofitting options in the largest industrial wastewater treatment plant in Northern Europe. A mechanistic mathematical model is simulated to reproduce process behavior (deviation < 11%). Multiple criteria are defined and verified with plant data (deviation < 5%). The feasibility of three types of scenarios is tested: (1) stream refluxing, (2) change of operational conditions and (3) the implementation of new technologies. Experimental measurements and computer simulations show that the current plant´s main revenues are obtained from the electricity produced by the biogas engine (54%) and sales of the inactivated bio-solids for off-site biogas production (33%). The main expenditures are the discharge fee (39%), and transportation and handling of bio-solids (30%). Selective treatment of bio-solid streams strongly modifies the fate of COD and N compounds within the plant. In addition, it increases revenues (+3%), reduces cost (-9%) and liberates capacity in both activated sludge (+25%) and inactivation reactors (+50%). Better management of the buffer tank promotes heterotrophic denitrification instead of dissimilatory nitrate conversion to ammonia. In this way, 11% of the incoming nitrogen is removed within the anaerobic water line and does not overload the activated sludge reactors. Only a marginal increase in process performance is achieved when the anaerobic granular sludge reactor operates at full capacity. The latter reveals that influent biodegradability is the main limiting factor rather than volume. Usage of either NaOH or heat (instead of CaO) as inactivation agents allows anaerobic treatment of the reject water, which substantially benefits revenues derived from higher electricity recovery (+44%). However, there is a high toll paid on chemicals (+73%) or heat recovery (-19%) depending on the inactivation technology. In addition, partial nitration/Anammox and a better poly-aluminum chloride (PAC) dosage strategy is necessary to achieve acceptable (< 2%) N and P levels in the effluent. The scenarios are evaluated from a sustainability angle by using life cycle impact assessment (LCIA) in form of damage stressors grouped into three categories: human health, ecosystems quality, and resource scarcity. The presented decision support tool has been used by the biotech company involved in the study to support decision-making on how to handle future expansions.

A Different Approach to Develop a District Heating Grid Based on the Optimization of Building Clusters

Currently, reducing energy consumption and fossil fuel emissions are key factors placed in the first position on the European agenda. District heating technology is an attractive solution, able to satisfy the energy and environmental goals of policymakers and designers. In line with this, a different approach to planning a district heating grid based on the optimization of building clusters is presented. The case study is Wilhelmsburg, a district of Hamburg city. This approach also investigates the usage of industrial waste heat as the grid’s heat source, which is CO2-neutral. First, the data acquisition regarding the buildings’ location and heat demand are described in detail. Based on the derived data and the source of the industrial waste heat, the district heating grid is created by clustering the buildings and connecting the obtained nodes. Furthermore, the grid’s efficiency is improved by eliminating nodes, which are too distant from the heat source, or have lower heat demand. Finally, a single building is simulated in Matlab/Simulink, showing the energy-savings and ecological results. The usage of the district heating grid saves 97.32 GWh annually, which results in financial savings of €5.83 million, and avoided CO2 emissions of 19,585 tCO2.

A review on geothermal energy resources in India: past and the present.

By 2040, India hopes to have completed its energy supply to fulfill the country's rising energy demands. Renewable and conventional sources must be used in an environmentally acceptable manner to achieve sustainable growth. India must enhance its use of renewable and clean energy sources, including geothermal, wind, and solar, to satisfy its growing demand. While solar and wind energy output has increased significantly, geothermal energy has yet to be fully harnessed. Among the many forms of geothermal energy found on the surface are volcanoes, fumaroles, erupting geysers, steaming fields, and hot springs. A total of about 340 geothermal springs may be found in India, spread throughout both orogenic (in the Himalayas) and non-orogenic (in the Peninsula). There were 31 places extensively evaluated, and deep drilling was performed in sixteen of them. Average temperatures range from 35.0°C to the boiling point of water in these springs. Medium (100.0-200.0°C) and low (100°C) enthalpy geothermal energy resources/systems are found in India, with the latter being the most abundant. The essential component of a geothermal system is understanding the heat source and harnessing it. Studies so far have indicated that some geothermal areas have sufficient geothermal potential for direct heat usage and power generation. If the Puga (J&K) field is explored to a depth of at least 500 m, reservoir simulation studies have shown that it might produce more than 3 MW of power. India's diverse geothermal sites and the current status of exploration for future research are discussed in the paper.

Techno-economic assessment for heating cattle feed water with low-temperature geothermal energy: A case study from central Alberta, Canada

There are over 450,000 registered oil and gas wells in the province of Alberta, Canada. A recent increase of the number of inactive wells creates significant environmental risk and financial liability in cleanup costs. By retrofitting wells for direct use geothermal heat energy production, these wells can produce clean, renewable energy and offset these risks and liabilities. This research is the first to create a model of well retrofit costs and power/benefits and to consider direct use of heat energy for ranching applications in Canada. We estimate the average cost to retrofit a suspended well to be $50,000 less than an identical abandoned well. The cost of retrofitting suspended wells varies little (<$11,000). The greatest variance in cost (>$120,000/well) is related to the distance between the well and user and resulting pipe/materials necessary to transport the hot water. Our model of well retrofit costs can be expanded to other geothermal re-purposing projects in North America and worldwide.

Usage of excess heat for district heating - Analysis of enabling factors and barriers

The use of industrial excess heat can be an important factor for the expansion and decarbonization of district heating networks. However, the enabling factors and barriers to implement excess heat recovery projects for district heating are still uncertain. Here, drivers and barriers for the integration of excess heat into district heating networks are analysed and a public available database of 45 implemented projects in Germany, Austria and France is created. 5 hypotheses of enabling factors and barriers were formulated and tested through 13 expert interviews with excess heat producers. Unlike the current literature, expert interviews are combined with a literature review to test the hypotheses. Thus, both quantitative and qualitative data are used to verify or refute the hypotheses. The results demonstrate that projects are often implemented only thanks to individuals and that the communication and exchange between the necessary stakeholders is often insufficient. It is also evident here that relevant stakeholders are often unaware of excess heat recovery opportunities. Furthermore, the results show that financial aspects are often not the main reasons for excess heat recovery for district heating, but play an important role in the decision-making. In conclusion, there are many barriers that can be overcome through meaningful policy design or better information and support.

Heat storage by melting the organic material of Paraffin RT50 in a heat exchanger with eccentric pipes

In this paper, the heat transfer inside a heat exchanger containing paraffin phase change material is investigated and the latent heat energy efficiency of RT50 material is calculated. Also, the effects of acentric condenser position on heat transfer and work efficiency are investigated in order to evaluate the energy efficiency by reducing the time required to melt the phase change material. On the other hand, in order to increase the thermal diffusivity, we have tried to improve the thermal conductivity by dispersion of SWCNT nanoparticles. Finally, the thermal analysis of the thermal energy storage system is performed by examining the effect of temperature changes in the condensers. The condensers are in the x and plus shapes, and the innovation of this study is the use of latent heat energy of phase change materials based on the passive technique. The results show that with increasing the distance of hot tubes from the center of the heat exchanger, the heat distribution increases, and the thermal efficiency increases by about 19 to 32 %. Also, by placing the hot tubes in the x-mode, the process of melting paraffinic materials leads to a reduction of time by 9 to 16 %.

The effect of using phase change materials in solar panel cooling to provide green and sustainable energy of a building

The present study numerically investigates the use of solar energy for heating in a building using EnergyPlus and COMSOL. A solar panel with a size of 0.5 × 1 m was simulated. A rectangular chamber containing CaCl26H2O as a phase change material (PCM) was positioned below the solar panel. A pipe with an Al2O3-water nanofluid flow and fins was placed in the middle of the PCM chamber. The hot water outflow of the solar panel was employed to supply the hot water demand of a small residential building. Also, the amount of carbon dioxide production for this house in different months of the year for the house with and without solar thermal panel was compared. Furthermore, the panel temperature and melted PCM fraction below the panel were studied at different nanofluid flow velocities. It was found that a higher flow velocity (20 mm/s) led to a lower panel temperature than a lower velocity (5 mm/s). Thus, a higher nanofluid flow velocity would increase the fraction of energy demand supplied through the solar system during the day (up to 19.1%); however, a rise in the velocity at night diminished the energy fraction. In July, using a solar heating panel to supply hot water to the house reduced carbon dioxide emissions by 43%.

On Hourly Forecasting Heating Energy Consumption of HVAC with Recurrent Neural Networks

Optimizing the heating, ventilation, and air conditioning (HVAC) system to minimize district heating usage in large groups of managed buildings is of the utmost important, and it requires a machine learning (ML) model to predict the energy consumption. An industrial use case to reach large building groups is restricted to using normal operational data in the modeling, and this is one reason for the low utilization of ML in HVAC optimization. We present a methodology to select the best-fitting ML model on the basis of both Bayesian optimization of black-box models for defining hyperparameters and a fivefold cross-validation for the assessment of each model’s predictive performance. The methodology was tested in one case study using normal operational data, and the model was applied to analyze the energy savings in two different practical scenarios. The software for the modeling is published on GitHub. The results were promising in terms of predicting the energy consumption, and one of the scenarios also showed energy saving potential. According to our research, the GitHub software for the modeling is a good candidate for predicting the energy consumption in large building groups, but further research is needed to explore its scalability for several buildings.

Long-Term Evaluation of Comfort, Indoor Air Quality and Energy Performance in Buildings: The Case of the KTH Live-In Lab Testbeds

Digitalization offers new, unprecedented possibilities to increase the energy efficiency and improve the indoor conditions in buildings in a cost-efficient way. Smart buildings are seen by many stakeholders as the way forward. Smart buildings feature advanced monitoring and control systems that allow a better control of the buildings’ indoor spaces, but it is becoming evident that the massive amount of data produced in smart buildings is rarely used. This work presents a long-term evaluation of a smart building testbed for one year; the building features state-of-the-art monitoring capability and local energy generation (PV). The analysis shows room for improving energy efficiency and indoor comfort due to non-optimal control settings; for instance, average indoor temperatures in all winter months were above 24 °C. The analysis of electricity and domestic hot water use has shown a relevant spread in average use, with single users consuming approximately four times more than the average users. The combination of CO2 and temperature sensor was sufficient to pinpoint the anomalous operation of windows in wintertime, which has an impact on energy use for space heating. Although the quantification of the impact of users on the overall energy performance of the building was beyond the scope of this paper, this study showcases that modern commercial monitoring systems for buildings have the potential to identify anomalies. The evidence collected in the paper suggests that this data could be used to promote energy-efficient behaviors among building occupants and shows that cost-effective actions could be carried out if data generated by the monitoring and control systems were used more extensively.

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.

Investigation of Process Parameters for Optimum Thermal Energy Distribution in Spark Erosion Process

In the Spark Erosion machining process, the electrical energy in the inter-electrode gap gets converted into thermal energy. Whatever thermal energy generated in inter electrode gap gets distributed among anode, cathode and the dielectric fluid. The workpiece in spark erosion process is kept as anode and the fraction of the total energy which is going to the anode (workpiece) should be maximum. As this thermal energy is responsible for the melting of material on the workpiece. This fraction of energy is the important parameter used to predict the effective use of total heat energy generated between tool and workpiece. The fraction of energy that is going to workpiece changes with change in machine parameter. It has been observed from the literature that the researcher simply considered a variation of spark voltage in analysis as a significant parameter in deciding material removal rate. In this work is variation of fraction of energy is experimentally determined with process parameters by using heat transfer equations during the spark erosion process of EN-31. The results showed that the ratio of amount of energy going to workpiece and total energy generated at inter electrode gap ranges from 9.56% to 18.97%. So, fraction of energy which is going to workpiece at different machining process parameter changes significantly, which proves that the it has significant impact on material removal rate and should be considered in study of spark erosion process.

Performance assessment of a novel combined heating mode integrated greenhouse and closed drying system with a dual-temperature steam jet heat pump

Waste heat recovery can significantly reduce energy consumption and greenhouse gas emissions in agricultural production. This study proposes a novel combined heating mode (CHM) integrated with a dual-temperature steam jet heat pump (DTJP) system with greenhouse (GH) and closed drying system (CDS) used in agricultural drying. The new system using water vapor as the working fluid significantly improves the performance by utilizing waste heat resources effectively. Compared with the individual heating mode (IHM), the new system reduces the usage of ancillary equipment, land occupancy, initial costs, and underground heat. The coefficient of performance (COP) and annual steam consumption are the main indicators for comparing the CHM using the proposed heat pump system with the IHM using a conventional jet heat pump. The thermodynamic analysis results show that the new system significantly enhances the COP under the given operating conditions. There is a 13–15.8% reduction in the annual steam consumption. This study provides a new idea for applying a jet heat pump system.

Development of Flow-Based Heating Supply Water Temperature Control for Apartment Building Using District Heating System

In the heating supply systems in apartment buildings utilizing district heating, the supply water temperature setting is a critical control for providing sufficient heating and effective usage of the heating energy. Conventional water temperature control methods such as fixed temperature (FT) control can result in energy wastage and outdoor air temperature reset (OTR) control cannot reflect the variation in the heating demands of households because it only considers the outdoor air temperature. Therefore, this study proposes an advanced control method called flow-based residential energy demand (f-RED) control, which sets the supply water temperature based on the outdoor air temperature and household heating demands (i.e., the changes in the circulated heating water flow). To determine the performance of the proposed method compared to the conventional one, this study utilizes building energy simulation. The simulation analysis results confirm that the f-RED control method appropriately sets the supply water temperature based on a combination of the two factors, supplies heat according to heating demands, and reduces the energy consumption of the circulation pump by approximately 1.6% and that of the secondary pump by 4.2%. Thus, the f-RED control method is able to utilize heat energy more effectively and efficiently than the conventional control method.