Heating Technology Research Articles

Optimization and simulation of a novel multi-energy complementary heat pump system in cold regions

Solar-assisted ground source heat pump systems(SAGSHPSs) and solar- assisted air source heat pump systems (SAASHPSs) are recognized renewable energy technologies for clean and feasible heating and domestic hot water supply. However, in cold regions, the poor thermal comfort of SAASHPSs and the soil thermal imbalance of SAGSHPSs during heating periods must be resolved urgently. Therefore, to provide an efficient and stable heat source, a multi-energy complementary heat pump system(MECHPS) with seasonal heat storage was designed to meet the needs of building energy consumption. The system comprehensively utilizes solar energy and ambient air for seasonal heat storage during non-heating periods, and then directly provides heat coupled with the ground source heat pump during heating periods. The composition and control strategy of the system were introduced. The system was numerically modeled by the simulation software Transient System Simulation Program (TRNSYS), and the main MECHPS modules were experimentally verified. Additionally, to study the optimal capacity of MECHPS in terms of economy and energy savings, the Hooke-Jeeves algorithm was used for MECHPS capacity optimization with the objectives of minimising the annual cost and maximising the annual savings of standard coal. The results showed that compared with traditional SAASHPSs, the MECHPS exhibited better thermal comfort while maintaining the room temperature above 18 °C. Compared to SAGSHPSs, the MECHPS was able to achieve soil thermal balance, and its soil temperature remained largely constant after 15 years of operation. Finally, compared with the initial scheme, the annual cost reduction rate was 4.98 % under the annual cost optimization scheme and an additional 1310 kg of standard coal could be saved under the annual savings of standard coal optimization scheme. The proposed system provides a way to satisfy the building energy supply for widespread application in cold regions.

Exploring the Potential of Solar Energy for Electricity and Heat Production in Azerbaijan

Taking use of Azerbaijan's advantageous geographic and climatic characteristics, this thesis investigates the potential of solar energy for the generation of heat and electricity in the nation. In order to assess the viability of solar photovoltaic (PV) systems for electricity production and solar thermal technologies for heating, it evaluates important places with significant sun insolation. The report points up difficulties including geographical variations in solar radiation and infrastructural constraints, but it also implies that these obstacles may be addressed by technical innovation and strategic planning. Azerbaijan's energy security and sustainability may be enhanced by implementing hybrid systems, supporting policies, and infrastructural enhancements that optimize the use of solar energy.

System Design, Modelling, Energy Analysis, and Industrial Applications of Ohmic Heating Technology

AbstractThe food and drink industry is gradually gaining sustainability pressure due to the high carbon emissions rate and limited availability of traditional energy supplies. Thus, it is essential to consider energy efficiency and decarbonisation of the ever-expanding food and drink industry. Ohmic heating technology is a highly energy-efficient and quick method of electrically heating food products. It uses the resistance of the food material to convert electrical energy into heat. However, the heating rate of ohmic heating depends on several process variables, such as electrical conductivity, voltage gradient, and voltage frequency. Therefore, it is important to study and understand the effects of these process variables to optimise the modelling and control of ohmic heating systems to obtain desirable output from food products. Hence, this study presents a review of the effects of process parameters on nutritional and organoleptic qualities, product yields, and energy efficiency of ohmic heating, along with its various industrial applications. The technology shows promising advancements in colour and nutritional quality, increasing energy efficiency, shorter processing times, and higher product yields compared to conventional heating processes.

Heating performance of PCM radiant floor coupled with horizontal ground source heat pump for single-family house in cold zones

As the energy demand for space heating increases, the necessity for innovative and energy-efficient heating technologies has become more urgent. This study proposes and evaluates a heating system that integrates a phase change material radiant floor with a horizontal ground source heat pump (PCM floor-HGSHP, Case 1), intending to maintain indoor comfort temperatures and enhance energy efficiency through the utilization of renewable energy sources. Despite the considerable potential of PCM floors, their combination with HGSHP requires further research to fully unlock their benefits. The study involved simulating the PCM floor using a validated TRNSYS component and developing an advanced rule-based control strategy with time-of-use tariffs as a key input to optimize system operation. To elucidate and quantify the advantages of the PCM floor-HGSHP system and verify its applicability in cold regions of China, a single-family house was used as a case study building, four representative cities were selected, and two comparative simulation cases were defined, along with three key performance indicators. The results indicate that, compared with the radiant floor heating system with HGSHP (RFHS-HGSHP, Case 2), the incorporation of PCM in the floor of Case 1 improves the indoor temperature stability by 8.6 %, enhances the load flexibility by 18.1 %, and reduces the total operating costs by 13.8 %. Furthermore, relative to the PCM floor with air-to-water heat pump system (PCM floor-AWHP, Case 3), the proposed system which substitutes the AWHP with the HGSHP, extends the duration of indoor comfort temperatures by 9.6 % and decreases the system electricity consumption by 33.7 %. The proposed system demonstrates excellent thermal and energy performance across all selected cities, proving to be both technically feasible and significantly beneficial for maintaining indoor comfort temperatures and reducing operational costs. This study offers valuable insights and technical support for designing and optimizing residential heating systems in cold regions, thereby promoting the development and application of renewable energy sources.

Modeling and operational characteristics analysis of a dual-source synergetic heat pump based on air energy and biomass waste heat

Air source heat pumps have gradually become a widely used heating solution worldwide due to their advantages of high efficiency, energy conservation, and environmental protection. However, air source heat pumps also face some challenges in practical applications, such as unstable heating and performance degradation in low-temperature environments. In order to improve these problems, based on the cascade heat technology, a new type of dual-source synergetic heat pump system is designed using air energy and biomass waste heat dual heat sources. In order to study its performance, a simulation model of the heat pump system was first constructed using distributed-parameter method. In order to verify the effectiveness of the model, an 18-kW heat pump experimental unit was constructed. By comparing the three key parameters of user side outlet water temperature, high-temperature compressor power, and system coefficient of performance (COP), the results show that the maximum error does not exceed 11 %; Secondly, in order to improve the stability and operational efficiency of the system, a three-level control strategy was designed based on considering the coordination of different grade heat sources; Finally, based on the above, the operating characteristics of the heat pump system were investigated through testing under different external input conditions. The research results indicate that by utilizing cascade heating and parallel heat exchange technology, the heat pump system can achieve stable heating even under large fluctuations in external working conditions. At the same time, compared with air source heat pumps, the COP can be improved by 69.7 % in low-temperature environments. The system results not only provide reference for the design and operation of new heat pump systems, but also provide practical and feasible solutions for the problem of decreased heat pump performance in low-temperature environments.

MICROWAVE THERMOLYSIS OF HEAVY OIL IN THE PRESENCE OF AN IRON-BASED CATALYST

Global demand for energy is growing every year, and there is also a decrease in reserves of traditional hydrocarbons. Today, the share of highly viscous and bitumen oil reserves is 25 % of the world. Production of extra-viscous oils will grow around the world.In order to solve the problem of developing highly viscous and bitumen deposits and increase oil recovery, we offer a technology for using aquatermolysis catalyst. Experience in the use of in-situ chemical conversion of organic matter has shown sufficient effectiveness in solving this problem.In this work, laboratory studies were carried out to improve the rheological characteristics of highly viscous and bituminous oils using microwave exposure using an iron-based catalyst precursor.The addition of a catalyst precursor containing iron nanoparticles provides more uniform and higher-speed heating when the formation is exposed to high-frequency electromagnetic radiation. This heating technology has been used in various fields to achieve environmental safety and high energy savings, in comparison with traditional methods that cannot achieve these indicators. The proposed technology simplifies the development process by eliminating the injection of coolants, thereby providing prospects for the processes of intensification of production and its subsequent transportation.In order to assess the possibility of effective application of high-frequency electromagnetic radiation to the formation in a particular field, first of all, data on the rheological characteristics of oil after exposure should be presented.These laboratory studies showed a decrease in viscosity under microwave exposure in the presence of a catalyst up to 1.8 times compared to the original oil sample. A decrease in viscosity characteristics was recorded already from a five-minute microwave exposure, as well as a change in the component composition of the oil, the tar content decreases by 27 % relative to the initial oil sample. This combination of the two methods of action provides new opportunities for the development of new technologies, as well as more efficient production of heavy oil.

Radiation model and thermal characteristics of OLED glass substrate using electric heating tube

Glass substrate (GS) heating is a fundamental but significant technology for organic light emitting diode (OLED), which is critical to OLED displaying quality and efficiency. A rapid and reliable theoretical model is intensely demanded to guide practical system design, simulation analysis and experimental research for GS heating, but present radiative models are improper or inconvenient. Therefore, this paper establishes a new and direct calculation model with the addition of correctional coefficient 0.5 to blackbody radiation power of electric heating tube (EHT) and the proposal of comprehensive angle coefficient X, which can solve single and multi-source radiation problems theoretically. The simulation and experiment are both conducted for comparison analysis. The temperature errors of theory and simulation for multi EHTs are all within 1 % when compared with experimental results, which well validates the reliability and accuracy of theoretical and simulation models. Large EHT radius r, small distance L between EHT and GS, and suitable EHT number n are suggested, which benefits to the improvement of radiation heating and temperature uniformity of GS. It is hoped that this study can provide a useful tool on thermal radiation analysis and also a valuable promotion for practical OLED heating technology.

Fervo Showed Fractured Geothermal Works, Now Must Do It Bigger, Cheaper, and Soon

Earlier this year, one of the founders of Fervo Energy announced that the geothermal innovator had reached its “Mitchell moment.” Jack Norbeck, chief technology officer for Fervo, likened a test where it used a pair of fractured wells to create water hot enough to generate electricity to the time when Mitchell Energy adopted slickwater fracturing to economically extract large amounts of gas from the ultratight rock in the Barnett Formation. “We have derisked all those core challenges, we reached the Mitchell Energy moment for geothermal,” Norbeck said. By doing all that and supplying 3.5 MW of electricity to the local grid that powers Google facilities, he announced that the firm’s enhanced geothermal system (EGS), had reached the highest level of technical readiness. Now comes the hard part—proving that technical triumph can be turned into something really big. The Mitchell moment in 1997 is remembered because it led to a series of innovations that allowed hydraulic fracturing and horizontal drilling to add enough oil and gas production to move global markets. What has been learned about fracturing in the decades since allowed oil industry veterans at Fervo to effectively use those tools to do what others had failed to accomplish—create high-volume EGS capable of generating power. One big difference between the moments is that Houston-based Fervo’s next step looks like a leap compared to Mitchell’s. After Mitchell’s moment, no innovation was required to sell shale gas from the Barnett or find the oilfield services needed to develop and produce it. Plus, it could learn from the many other companies working in tight rock plays. Its moment was the culmination of years of innovations by oil and service companies who continued finding ways to build on that advance. The endless arguments over who can claim credit for the innovations behind the Mitchell moment are evidence of the size of that support network. Today, Fervo’s efforts are also supported by the oil industry’s service sector and supply chain. Oil company Devon Energy, drilling contractor Helmerich & Payne, and pressure-pumping specialist Liberty Energy are among its early backers. And Fervo is benefiting from the government-funded research and site-evaluation work at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) site, which is the key site for geothermal testing funded by the US Department of Energy (DOE). But unlike Mitchell, the path to commercial success will require Fervo and others to show they can create large operations to convert the heat they harvest into a cost-competitive commodity in a fast-changing, highly competitive industry. Sage Geosystems recently was added to the short list of geothermal startups with big projects, signing a deal with Meta to build a 150-MW plant somewhere east of the Rockies. Also high on the list is Eavor whose first commercial project will use its closed-loop heating technology for home heating and electric generation in Germany.

Performance assessment of deep borehole heat exchanger heating system under different heating modes

Abstract With the transition towards renewable energy sources, particularly as we move away from fossil fuels, there has been a constant evolution of deep borehole heat exchanger (DBHE) coupled heat pump heating technology. On the basis of the heat-exchanging properties of circulating fluid in the DBHE heating system, this paper clarifies the setup forms of this system, and elucidates the influence of heat extraction performance. After analysis and research, it can be concluded that the direct supply mode shows a more prominent decline in water temperature compared to the coupled heat pump and coupled plate heat exchanger modes. The imported and exported water temperatures when heating ends were recorded as 9.98°C and 16°C, respectively. The imported and exported water temperatures for both the direct supply and the coupled plate heat exchanger modes tend to be similar at 19.6°C and 25.5°C at a temperature of 7°C. Heat pump not only enhances the heat exchange features of ground source heat pump (GSHP) heating system, but also defines the configuration of heat extraction performance of DBHE. The system power consumption in the coupled plate heat exchanger mode is lower than that in the heat pump mode which is conducive to stable operation. Therefore, the best design form of the DBHE Heating System is the heat pump coupled plate exchange mode.

Enhanced coalbed methane recovery by microwave-induced thermal fracture

Abstract The investigation on microwave-induced permeabilization and response of coal under microwave heating is of great significance for the industrial application of microwave heating technology instead of traditional heating in coalbed methane mining. Santanghu coal is used as a sample to measure the permeability and porosity of coal samples before and after microwave heating. The fracture changes of coal samples before and after heating are compared to observe the penetration effect of microwaves on coal samples. Based on the technology of directional drilling and continuous tubing technology in petroleum engineering, a technology of increasing the production of coalbed methane by microwave heating in a wide range of coal seams is proposed. The feasibility of this enhanced production method is validated through COMSOL Multiphysics simulations, which model the temperature field distribution within coal seams under various microwave parameters. This approach highlights the potential of microwave technology in coalbed methane recovery. The results show that: (1) the thermal field of coal samples under microwave heating is inhomogeneous. The average length and area of the cracks of the coal samples increased under microwave radiation, and the cracking of the coal samples confirmed the cracking effect of microwaves on the coal samples. (2) With prolonged microwave heating, coal samples exhibit an initial decrease followed by an increase in porosity and permeability, a trend attributed to the expansion of solid particles that occupy and reduce pore spaces. (3) The in-situ microwave heating technique for coalbed methane extraction overcomes the challenges of long-distance microwave transmission loss and methane backflow in transmission pipelines, utilizing continuous pipelines for extensive microwave heating of coal seams. (4) The microwave power and intermittent heating duration have a significant effect on the temperature field distribution of the coal seam, and when the heating duration is 60 days, 1600 W is used to have an effective temperature field distribution while avoiding the waste of heat. When the power is constant at 1600 W, the effective temperature range is wider when the intermittent heating duration is 60 days.

One-step ultrafast Joule heating synthesis of EuB6 ceramics and their electronic transport and magnetic properties

The synthesis of high-performance rare-earth borides (e.g., RB2, RB4, R2B5, RB6, RB12, and RB66) typically necessitates sintering at high temperatures and high pressures for prolonged durations. Traditional methods, such as hot-pressing sintering and spark plasma sintering, are marked by high production costs and low efficiency. Here, using EuB6 as an example, we demonstrate the successful synthesis of rare-earth boride ceramics utilizing the one-step ultrafast joule heating technology. Using this method, we optimized the sintering temperature and duration and synthesized EuB6 ceramics with superior electronic and magnetic properties at 1600 °C in just 5 min. The EuB6 ceramics prepared under optimized conditions show distinct paramagnetic to ferromagnetic phase transition, significant negative magnetoresistance, and enhanced magnetization. The combination of the one-step ultrafast Joule heating technology and boron thermal reduction method offers a simple and fast synthesis approach for fabricating polycrystalline EuB6 and may be extended to prepare other rare-earth and transition-metal borides.

Energy analysis of a direct expansion heat pump assisted by a thermal photovoltaic panel for hot water production in several regions of Brazil

This study focused on evaluating the energy performance and economic viability of a direct expansion photovoltaic-Thermal Heat Pump (PV-T/HP) system for residential heating applications in various regions of Brazil. A detailed mathematical model was implemented to compare the PV-T/HP system with other solar heating technologies, as photovoltaic with solar evacuated tubes collector (PV+TSC) and photovoltaic with electrical heat water (PV+EHW), analyzing key metrics such as electrical efficiency, thermal efficiency, and levelized cost of heat (LCOH). The study revealed variations ranging from 7.5 to 2.5 in the Coefficient of Performance (COP) of the heat pump under different solar irradiation and ambient temperature conditions, emphasizing the necessity for future optimization to enhance the system performance. Results indicated that cities with the lower ambient temperature such as Belo Horizonte and Porto Alegre exhibited favorable conditions for the PV-T/HP system, leading to increased energy generation and positive net electricity production. The study highlighted the need for tailored strategies to control system operations, limit compressor consumption, and improve overall efficiency. These findings contribute to the understanding of PV-T/HP systems in residential heating applications, showcasing their potential for sustainable energy solutions in Brazil.

Comparison of Parabolic Troughs and Solar Photovoltaic as Solar Field Technology in Dispatchable Solar Power Plants

The use of thermal energy storage (TES) technologies, as means to provide dispatchability to thermally driven solar power production, has long stood as the main argument for the interest and potential competitiveness of Concentrated Solar Power (CSP) when compared to other non-dispatchable alternatives. Whereas reductions of the Levelized Cost of Electricity (LCOE) are observed for CSP in recent years, the notable LCOE reduction observed along this decade in large-scale solar photovoltaics (PV) plants is set to break the taboo of "power-to-heat-to-power" approaches, as its potential economic performance outcasts the associated thermodynamic inefficiency. The possibility of using available resistive heating technologies and components in PV-TES combinations, renders the configuration of a conventional CSP plant suitable for the replacement of a thermal conversion solar field by a photovoltaic field presenting further the possibility of delocalization and/or spatial distribution of the solar field (e.g. on a Carnot Battery configuration). As dispatchability no longer stands as an exclusive argument in favor of CSP over PV, the present article addresses the boundary conditions for the competitiveness of each technology as the champion of dispatchable solar power fields. The impact of both land and electrical heater costs variation in the variation of LCOE for PV-TES plants is much more modest than that observed for the impact of CSP solar field cost variations in the variation of LCOE for CSP plants, which leans for the latter and at present costs, towards better competitiveness for plant designs with a storage capacity in excess of 10.0 FLH (for GHI values in excess of 2100-2200 kWh∙m-2∙year-1).

Understanding the thermodynamic effects of chemically reactive working fluids in the Stirling heat pump

Within the realm of sustainable heating technologies, this study examines the performance of a Stirling heat pump employing chemically reactive working fluids in contrast to conventional inert counterparts. Reactive working fluids are energy vectors that enable the conversion of not only thermal but also chemical energy within the heat pump. The investigation spans a wide range of theoretical reactive gaseous mixtures, leveraging the ideal gas mixture thermodynamic model. Each fluid is characterized by an equilibrated chemical reaction, denoted as A2(g)⇄2A(g), and distinguished by a set of reaction coordinates: the standard entropy change of reaction and standard enthalpy change of reaction. The chemical reaction evolution and thermodynamic properties are observed in each transformation, and the overall coefficient of performance (COP) of the system is evaluated and benchmarked against that of comparable inert working fluids. It is observed that the exothermic reaction during isothermal compression significantly increases the thermal energy supplied to the heat sink, as well as the thermal energy density per unit maximum volume, by up to 269 %, compared to an inert gas system. However, for the majority of reactive fluids studied, chemical reactions introduce irreversibility in the internal regenerator due to heat transfer across a finite temperature difference, contrary to the case of inert working fluids, penalizing the COP. Consequently, a reduction of up to 28 % in the COP is observed. Nevertheless, there exists a range of reactive fluids, characterized by reversible heat exchange in the internal regenerator, offering increased thermal energy transfer to the heat sink without compromising the COP.

Willingness-to-pay for low-carbon residential heating systems: A discrete choice experiment among Dutch households

Most studies on decarbonizing space and water heating focus on the potential of low-carbon heating technologies from a top-down perspective, while there has been limited research on consumer preferences for low-carbon heat. To address this gap, we conduct a discrete-choice experiment among 1797 individuals in the Netherlands to estimate the willingness-to-pay (WTP) for residential-heating systems. Our results from the latent-class logit (LCL) model indicate that, on average, Dutch households are willing to pay a premium on their current monthly energy bill of 33% for electricity and 29.4% for hydrogen relative to using gas for heat production, 15.3% for reducing the amount of CO2 emissions per kWh of heat with 100 g and 16% for having the option to switch between energy retailers. In contrast, they require a discount of 28.4% for district-heating systems relative to standalone home appliances. Additionally, the class-profiling analysis indicates that individuals with higher education and income levels in the Northern Netherlands have the highest WTP for low-carbon electricity and hydrogen. These findings suggest that policymakers should favor decentralized heating solutions over district-heating systems to facilitate an energy transition in the residential sector. If district-heating systems are implemented, combining them with electricity or hydrogen instead of natural gas is recommended to realize higher consumer welfare.

Simulation study on thermal performance of solar coupled air source heat pump system with phase change heat storage in cold regions

The development of efficient and clean heating technologies is profoundly significant for the reduction of carbon emissions in cold regions. This paper puts forth a novel solar-coupled air source heat pump system integrated with phase change heat storage technology, which is well-suited for regions with such climatic conditions. A numerical model of the components and coupled systems is established using the lumped parameter method, and an iterative method is employed for the computational solution in MATLAB software. A variety of system performance aspects are then simulated and analysed following the configuration of component structural parameters and initial operating conditions. The results of the simulations indicate that an increase in the phase change temperature interval of the phase change materials leads to a higher average heat release power. In particular, a 2 °C increase in the phase change temperature interval results in an increase in the heat release power of over 10 %. Furthermore, when the system is applied in typical cold regions, including Kunming, Hangzhou, Lhasa, and Harbin, the average coefficient of performance is 10.23, 8.87, 8.49, and 7.70, respectively. The proportion of solar energy input contributes to an increase in system efficiency across all regions. A case study of Hangzhou reveals that the incorporation of solar energy into the system results in an increase in efficiency of 70.91 %. This research provides valuable operational methods and site selection recommendations for engineering practices, laying a theoretical foundation for its widespread application in cold regions.

Design-Point Techno-Economics of Brayton Cycle PTES for Combined Heat and Power

Abstract Pumped thermal energy storage (PTES) systems are grid batteries that use heat pumps to create both hot and cold thermal energy stores when there is excess electricity and then use a power cycle to convert the thermal energy into electricity when there is demand for electricity. In normal operation, Joule-Brayton PTES discharges low-grade heat at temperatures useful for thermal energy consumers like district and industrial heating. Furthermore, PTES designs, like conventional combined heat and power (CHP) technology, can be modified to sacrifice some round-trip efficiency (RTE) to increase the temperature of heat rejection. This paper uses design-point performance and cost models that provide a detailed understanding of the efficiency and cost trade-offs of rejecting heat at various temperatures in ideal-gas Brayton PTES configurations. First, we keep the heat rejection in its nominal location in the PTES system. Next, we move the heat rejection to the discharge turbine exit. We define design-point metrics that isolate both the cost and performance penalty associated with the hotter heat rejection and attribute it exclusively to the heat economic metrics. We find that the levelized cost of heat, including the cost of thermal energy storage (TES) buffering the PTES and heat off-taker, compares favorably versus electric technologies and is less than the cost of natural gas for low temperature scenarios and competitive with the cost of natural gas in some regions of the contiguous United States in high temperature scenarios.

Selective recovery of antimony from Sb-bearing copper concentrates by integration of alkaline sulphide leaching solutions and microwave-assisted heating: A new sustainable processing route

The technical feasibility of leaching antimony from an antimony-bearing copper sulphide concentrate, using alkaline sulphide solutions and microwave-assisted and non-assisted heating technology, is investigated at a laboratory scale. The leaching test examines the influence of selective leaching reagent (Na2S and NaOH) concentrations, solid/liquid ratio, and temperature. The results indicate that antimony dissolution is highly selective (e.g. only Sb and As are leached), depending on the concentrations of leaching reagents and the leaching temperature. The influence of temperature on the mineral's dissolution, in the range 25–140 °C, is analysed from a thermochemical point of view using equilibrium databases. Under the optimal conditions: leaching agent: 250 g/L Na2S, 60 g/L NaOH, 2 h, 140 °C, with microwave assisted, the leaching efficiency of Sb reached 95.7 %. The antimony content in the copper concentrate is successfully reduced from 1.1 wt% to <0.2 wt% Sb, making it suitable for copper concentrate metallurgical processing. The study demonstrates that increasing temperature and NaOH/Na2S concentrations collectively enhance leaching efficiency, with a statistical significance, reducing both leaching time and the required temperature, compared to non-microwave-assisted leaching. Furthermore, it is established that excess free hydrogen sulphide ions ensure the efficient dissolution of the main impurities associated with penalties, such as antimony and arsenic, with limited copper and iron dissolution from the copper concentrate, predominantly chalcopyrite. Finally, an integrated hydrometallurgical process flowsheet for antimony removal and recovery from a sulphide copper concentrate is proposed.

A multi-valve flexible heat pump system with latent thermal energy storage for defrosting operation

There has been growing interest in using air-source heat pumps as an alternative to potentially replace fossil-fuel-based heating technologies for heat decarbonisation. One of the technical issues that hinders the wide uptake of air source heat pumps is the decreasing energy efficiency caused by frequent defrosting operations under low ambient temperatures. Currently, the most widely used defrosting method is the reverse-cycle defrosting but this operation would have to interrupt the heating supply during the defrosting process. The authors recently proposed, developed, and demonstrated a flexible heat pump concept that recovers partial of the subcooled heat from the hot refrigerant exiting the condenser and stores it in an integrated thermal storage. The stored heat could later be used to save compressor power and defrosting applications. In this paper, we proposed an innovative method by using a multi-valve design of the flexible heat pump to achieve the defrosting function. In this new concept, defrosting is achieved by condensing the refrigerant inside the evaporator and simultaneously ensuring uninterrupted heating during the heat storage discharge process. A model has been established to study the heat pump performance during a full charge/discharge cycle of the storage. Results indicated that with R410a, R134a and R1234yf, the proposed flexible heat pump has the potential to respectively save up to 11.2%, 10.8% and 13.2% of compressor power, in comparison with a heat pump using the conventional reverse cycle defrosting method. Concurrently with the defrosting operation, the same heating capacity is ensured without interruption by the flexible heat pump.

Research on the Application of New Energy and Low-carbon Technologies in the Repair of Concrete Surface Defects

Photovoltaic heating is a new energy technology, which plays an obvious role in concrete curing, which can shorten the curing time of concrete. However, the role of this technology in concrete surface repair is not clear. In order to expand the application scope of low-carbon energy, this paper takes concrete surface repair as the research object and conducts photovoltaic heating analysis. Firstly, the data of concrete surface depression were collected, and then the repair effect of photovoltaic heating technology on the concrete surface was analyzed with C30 # as the research object, such as compressive strength, curing time, complex spacing, repair cost and energy consumption. and analyze the range of variation of each indicator; The results show that the photovoltaic heating technology can shorten the curing time by 20% and improve the compressive strength to 50kg/m2 with a complex spacing of less than 20 microns. At the same time, the repair cost and energy consumption are reduced, and the reduction range is 15~18%. Therefore, new energy and low-carbon technologies such as photovoltaic heating can effectively repair concrete surface defects, build on the cost and energy consumption of repair, improve the repair time, and meet the overall requirements of concrete construction.