Heat Pump Technology Research Articles

Energy-efficient and environmentally friendly technology for producing fatty acid esters

We implemented heat pump technology of obtaining esters of fatty acids (of tolivia biodiesel) from vegetable oils, providing for the transesterification of oil with alcohol supercritical fluid and supercritical CO2-extraction of the cooled reaction mixture, its separation by centrifugal force to separate the glycerin from the target product, the separation of carbon dioxide gas-liquid separation with obtaining a purified biodiesel and the return of carbon dioxide to the extraction stage in closed loop thermodynamic cycle. A steam-ejector heat pump is used to prepare energy carriers of different temperature potentials. The physical and chemical parameters of the obtained biodiesel fuel corresponded to the regulatory documentation. The energy and environmental efficiency of using rapeseed ethyl ether (REE) obtained using the proposed technology and its mixtures with mineral diesel fuel when performing agricultural work with the Kirovets K-701 tractor was checked. During the test, it was found that in the same operating conditions, the tractor when working on REE and its mixtures with mineral diesel fuel at maximum power develop the same traction force. The use of biodiesel and its mixtures reduces environmental pollution and increases the purity of the exhaust compared to the operation of a tractor unit using mineral diesel fuel.

Design and Thermodynamic Analysis of Waste Heat-Driven Zeolite–Water Continuous-Adsorption Refrigeration and Heat Pump System for Ships

Strict International Maritime Organization (IMO) rules enable ships to maximize fuel consumption and compliance with the climate. Cooling and heat-pumping technology powered by waste heat makes a substantial contribution to lowering ship gas emissions. This study explores, technically studies, and thermodynamically analyzes the efficiency of ongoing adsorption refrigeration and heating systems using a zeolite–water pair onboard a naval surface ship. An updated Dubin-in-Astakhov equation calculates the equilibrium adsorption potential of the operating pair used in the system. The coefficient of performance (COP) and specific cooling power (SCP)/specific heating power (SHP) values were between 0.109 and 0.384 and between 69.13 and 193.58 W kg−1 for cooling mode, and between 66.16 and 185.26 W kg−1 based on exhaust gas temperature and regeneration, respectively. Up to 27.64% and 52.91% met the cooling and heating load of the case vessel at a full load by the zeolite–water-adsorbed refrigeration/heat-pumping system. The COP of the heat pump and cooling systems was compared to that of adsorption cooling/heat pumps in the literature.

Field study on heat pump monitoring: challenges and opportunities

In view of the decarbonisation targets in the building sector, heat pump can play a key role, marking the shift towards all-electric buildings. Although the heat pump technology is well known, and its use is ever increasing, some issues (practical and operative) are still open in the assessment of the main aspects that influence the efficiency. These complexities emerge when heat pump monitoring is carried out, allowing to assess the real performance. Therefore, in this work, the challenges and opportunities of heat pump monitoring are presented, from a field study of the tertiary sector. The monitoring of an air-to-water heat pump allowed to: (i) assess its real operating performance; (ii) compare the correlations of results with climate data and load profile; (iii) highlight some critical points, as the importance of data mining and data cleaning phase for the reliability of the results; (iv) assess and identify which is the temporal scale needed for a proper data elaboration.

Solar thermal control system based on variable frequency heat exchanger control technology

Frequency conversion exchanger control is the critical technology of solar water heaters. It can integrate solar thermal technology and heat pump technology and makes solar thermal energy conversion efficiency higher. Based on this research background, the paper first discusses the principle of the technology. Then, it optimizes the system control strategy based on maximizing the utilization of heat energy and the highest efficiency ratio. Finally, the article established a deep learning model of solar radiation based on different time-sharing. The experimental simulation confirmed that the thermal energy control optimization algorithm model proposed in this paper could effectively predict thermal energy exchange.

Research on the experimental performance of gas-fired boiler based on the total heat recovery technology of absorption heat pump

Based on an example of a gas-fired boiler for an industrial user in Tianjin, the absorption heat pump technology was used to carry out energy-saving transformation of the above boiler. The actual test was carried out on the gas flow, exhaust gas temperature and other parameters from January 2, 2018 to February 26, 2018. And then, the thermal efficiency of the boiler was analysed. The results show that after the energy-saving transformation, the exhaust gas temperature of the gas-fired boiler can be reduced from 140 °C to about 40 °C, and the overall thermal efficiency of the boiler also rises from 89.5% to 101.3%, which is 13.2% higher than that before optimization. According to the economic analysis, the energy-saving reconstruction project can achieve an energy-saving economic benefit of 1.598 million yuan throughout the year, with obvious energy-saving and emission reduction benefits.

Economic Analysis of Heat Pump Recovery System for Circulating Water Waste Heat in Power Plant

The use of heat pump technology to recover the waste heat of circulating water from the power plant instead of steam extraction for heating can not only improve the thermal efficiency of the unit and reduce the loss of cold source, but also has great advantages in energy saving. This paper uses absorption and compression heat pumps to recover the waste heat of circulating water in the power plant to study its energy-saving benefits. Under the same heating load, the economics of the two heat pumps are calculated and analyzed. The results show that the energy-saving benefits of absorption heat pump units are far greater than compression units. But in terms of water saving, the water saving capacity of the compression heat pump unit is higher than that of the absorption heat pump.

BUILDINGS DESIGN INTEGRATION WITH GEOTHERMAL ENERGY SYSTEM TECHNOLOGIES AND AIR CONDITIONING APPLICATIONS

Nowadays global warming and thermal islands in modern cities are spending much energy on heating and cooling spaces. Geothermal energy considered a renewable energy technology for space heating and cooling. The ground source heat pumps (GSHPs) are increasingly interested in their expressive potential to reduce fossil fuel consumption and hence reduce greenhouse gases. Geothermal energy used for both electricity generation and direct use, depending on the temperature and the chemistry of the resources. Recently, direct utilization has varied significantly, and there are several methods available for temperatures typically ranging from 4°C up to 80°C. (Lund J.W., 2012). This paper presents a comprehensive literature-based review of ground source heat pump technology, cooling, and heating applications buildings to achieve precisely human thermal comfort. Subsequently, propose the influence factors of the system components that would undoubtedly reflect on the optimal design of the building. As a result, achieve precisely an integrated building.

Influence of the Thermal Energy Storage Strategy on the Performance of a Booster Heat Pump for Domestic Hot Water Production System Based on the Use of Low Temperature Heat Source

Energy recovery from a low temperature heat source using heat pump technology is becoming a popular application. The domestic hot water demand has the characteristic of being very irregular along the day, with periods in which the demand is very intensive and long periods in which it is quite small. In order to use heat pumps for this kind of applications efficiently, the proper sizing and design of the water storage tank is critical. In this work, the optimal sizing of the two possible tank alternatives, closed stratified tank and variable-water-volume tank, is presented, and their respective performance compared, for domestic hot water production based on low temperature energy recovery in two potential applications (grey water and ultra-low temperature district heating). The results show that the efficiency of these kind of systems is very high and that variable-water-volume tanks allow a better use of the energy source, with an 8% higher exergy efficiency and around 3% better seasonal performance factor (SPF), being able to provide similar comfort levels with a smaller system size.

Optimization and energy assessment of geothermal heat exchangers for different circulating fluids

One significant obstacle to the adoption of geothermal heat pump (GHP) technology is the installation costs of geothermal heat exchangers (GHE). Cost reduction through optimization of system parameter offers the potential for increased applications. In the current work, five major parameters are considered: length, radius, well numbers, the flow discharge inside the pipe, and the pipe's external radius for optimization using a genetic algorithm (GA) for a residential building in hot climatic conditions. In addition, system optimization is critical in determining values of design parameters for assessing the impact different circulating fluids on the energy consumption of GHP. A ten-year simulation is undertaken to evaluate the capacity of various circulating fluids and their effects on energy consumption reduction. The simulation shows a significant decrease in energy consumption based on varying levels of Ethylene glycol, Methanol, Potassium acetate, Sodium chloride, Freezium™ compared to pure Water in the GHP. The COP of the GHP system is also calculated with different circulating fluids. In addition, the circulating fluid with the highest performance loss during ten years of operation is identified. Based on the results, Ethylene glycol is selected as the preferred solution for use in the GHP. In the present study, we have also established the optimum configuration of GHEs according to a reliable evolutionary algorithm for investigating the effect of various circulating fluids on the system's energy consumption.

The simulation and analysis of wood fuel low-grade heat

Modern wood fuel plants use freshly felled and chipped wood, so the flue gas contains a significant amount of vapour. Even after the condensing economizer, the flue gas carries out a considerable amount of heat ejected into the surroundings. It is impossible to use this heat for heating directly because it is too low grade. Additional energy and investment are needed for its utilization, e.g., using mechanical heat pump technology. The utilization effectiveness depends on the heat capacity that the flue gas carries out of the condensing economizer as well as on the temperature to which the gas is cooled down. These two parameters are interdependent and have to be calculated before designing the heat pump. The calculations and simulation of the wood fuel low-grade heat is quite sophisticated due to the fact that the composition of flue gas changes during its cooling process. This article presents a mathematic model of the calculations of flue gases. This model presents simulation and some results which could facilitate the evaluation of the effectiveness of the low-grade heat utilization using heat pump technology. The verification of results, presented in the article, shows correctness of the model and calculations’ accuracy.

Використання теплових насосів для опалення та гарячого водопостачання будівель підприємств на прикладі установок Helioterm

Heat pump - a device for transferring thermal energy from a source of low potential thermal energy to a consumer with a higher temperature. The thermodynamic cycle of a heat pump is similar to a refrigerating machine. Depending on the principle of operation, heat pumps are divided into compression and absorption. The most commonly used compression heat pumps. In recent years, numerous publications on the use of heat pump technology in heating and hot water supply facilities of various spheres - from individual homes to residential neighborhoods have appeared in various media. The authors of the publication have many years of experience in joint scientific and technical cooperation with leading technical universities and industrial organizations in the field of development and practical use of heat pump technology. The authors analyze the possibilities of introducing heat pumps at enterprises and organizations of the State Reserve System of Ukraine. It has been shown that the amount of expenses in comparison with central heating or operation of gas and electric boilers of similar power is several times smaller. It is noted that the implementation of heat pumps is a promising direction in the use of alternative energy sources to meet the heating, ventilation and hot water supply needs of buildings. The payback period from the introduction of heat pumps at enterprises is 4-9 years, depending on the location of the object and the type of source of low-temperature heat. The article meets the requirements of the State Tax Code of Ukraine and can be recommended for publication.

Application Research on deep recovery and utilization technology of flue gas waste heat of coal water slurry boiler

Coal water slurry boiler has attracted great attention in the field of urban heat system because of its efficient and clean coal combustion. The coal water slurry contains 35% moisture, which makes the waste heat recovery potential of flue gas greater. After the combustion of coal water slurry, the 100°Cunsaturated flue gas becomes 50°C saturated wet flue gas after Wet Desulfurization Process. The Direct Contact Thermal Storage System and Heat Pump technology are used to realize the deep recovery of low-temperature flue gas. The technology has been successfully applied in the 6×70MW coal water slurry boiler of La Shan Heat Source Company. After 120 days of operation, 393000 GJ of flue gas waste heat is recovered, about 23000 tons of coal water slurry is replaced, and 84000 tons of flue gas condensate is recovered. It has good economic and social utility. It is an effective way to recover and utilize waste heat from flue gas of coal-fired boiler, and has a broad application prospect.

Optimum Design and Control of Heat Pumps for Integration into Thermohydraulic Networks

Germany has become one of the leading players in the transformation of the electricity sector, now having up to 42% of electricity coming from renewable sources. However, the transformation of the heating sector is still in its infancy, and especially the provision of industrial process heating is highly dependent on unsustainable fuels. One of the most promising heating technologies for renewable energies is power-to-heat, especially heat pump technology, as it can use renewable electricity to generate heat efficiently. This research explores the economic and technical boundary conditions regarding the integration of heat pumps into existing industrial thermohydraulic heating and cooling networks. To calculate the optimum design and control of heat pumps, a mixed-integer linear programming model (MILP) is developed. The model seeks the most cost-efficient configuration of heat pumps and stratified thermal storage tanks. Additionally, it optimizes the operation of all energy converters and stratified thermal storage tanks to meet a specified heating and cooling demand over one year. The objective function is modeled after the net present value (NPV) method and considers capital expenditures (costs for heat pumps and stratified thermal storage tanks) and operational expenditures (electricity costs and costs for conventional heating and cooling). The comparison of the results via a simulation model reveals an accuracy of more than 90%.

Scientific priorities for the use of alternative energy sources in railway transport

Alternative energy sources, mostly related to “green” energy, are one of the promising trends in the development of energy generation, including for the global railway sector. This is due, firstly, to its desire to preserve its environmental advantages by reducing carbon dioxide emissions into the environment and increasing energy efficiency, and secondly, to a reduction in the use of such sources as oil and coal as fuel resources in the coming decades.In a world where 95 % of motorized vehicles use oil as fuel, the greenhouse gas emissions per passenger-kilometer for rail transport are five times less than for road transport and 20 times less than for air transport. Therefore, one of the key tasks in the development of railway transport is the creation of high-speed highways that will serve as an alternative to road and air communications over short distances.In addition to the well-known alternative energy technologies, the railway transport traditionally conducts scientific research to improve energy-saving technologies, which include the use of excess recuperation energy when rolling stock braking.Also, projects for the use of renewable energy sources — heat pump installations — have proved their effectiveness in railway transport: heating switches from the ground, use of heat from compressors of hill complexes to heat electrical centralization posts and heat transformers of traction substations for its own needs.The role of alternative energy sources in railway transport is constantly growing. The efficiency of using alternative energy sources at the Russian Railways is largely determined by a scientific approach that allows, based on own experience or experience in introducing innovations in related industries, to determine the place, time and degree of their implementation, taking into account technical and technological features of production processes inherent in a particular structural unit companies. Among the innovative technical solutions in railway transport, the most priority ones are solutions aimed at the development of high-speed lines, recuperation systems, as well as heat pump technologies.

Обзор особенностей внедрения теплонасосного оборудования при создании энергоэффективной жилой среды

Heat pump systems become very promising equipment saving energy and improving overall energy efficiency and environmental protection in the residential sector. This review paper provides an update on current specifics of heat pump implementation in Russian residential sector. The paper also reviews major technical and supporting measures promoting broad distribution of the heat pump technology. In a computational part of this paper, heat pump refrigerant evaporation temperature and its influence on fuel consumption were analyzed for a heat pump system arrangement option with parallel evaporators.

A Novel Ground-Source Heat Pump with R744 and R1234ze as Refrigerants

The energy-saving potential of heat pump technology is widely recognized in the building sector. In retrofit applications, especially in old and historic buildings, it may be difficult to replace the existing distribution and high-temperature emission systems. Often, historical buildings, especially the listed ones, cannot be thermally insulated; this leads to high temperatures of the heat carrier fluid for heating. In these cases, the main limits are related, on the one hand, to the reaching of the required temperatures, and on the other hand, to the obtaining of good performance even at high temperatures. To address these problems, a suitable solution can be a two-stage heat pump. In this work, a novel concept of a two-stage heat pump is proposed, based on a transcritical cycle that uses the natural fluid R744 (carbon dioxide) with an ejector system. The second refrigerant present in the heat pump and used for the high-temperature stage is the R1234ze, which is an HFO (hydrofluoro-olefin) fluid. This work aims to present the effective energy performance based on real data obtained in operating conditions in a monitoring campaign. The heat pump prototype used in this application is part of the H2020 Cheap-GSHP project, which was concluded in 2019.

Improving the economy and energy efficiency of separating water/acetonitrile/isopropanol mixture via triple-column pressure-swing distillation with heat-pump technology

The separation of water/acetonitrile/isopropanol ternary mixture is difficult to achieve with conventional distillation. However, pressure-swing distillation (PSD) is one of the most effective methods. This study investigates two PSD processes with different separation order where the W-A-I separation sequence has a better performance in economy, energy consumption and environment. Several energy-saving methods, including heat integration, heat-pump and heat exchanger network, have been introduced for using the sensible heat and latent heat of the process. In addition, the T-S diagrams of overheads from each column in processes with heat-pump are utilized for discussing the feasibility of dry compression. Among all the processes, the PSD process with triple-heat-pump and heat exchanger network (PSD-THP-HEN) requires the lowest cost and energy and emits the lowest CO2, SO2 and NOx. Compared with the PSD-HEN process, 71.4% of TEC and 57.59% of TAC are saved in PSD-THP-HEN, respectively.

Performance Study of a Hybrid Heat Pump Dryer based on Numerical Analysis and Experimental Set-up

Seafood, especially sea cucumbers and oysters are an expensive delicacy in several Asian countries. Traditional sun-drying of these products takes 3 to 4 days and fetches a lower market price. Modern industrial drying machines used for seafood drying are unable to dry sea cucumbers and oysters without texture and color degradation as they are delicate, temperature-sensitive and have longer drying time. An economical drying system that does not cause texture or color degradation is the heat pump drying system and is commonly applied for agriculture and fabric drying. In this study, the heat pump technology is applied to develop two hybrid dryer models (bottom discharge and front discharge) to dry shellfish and sea cucumbers in large scale for storage and transportation. Each model is tested in a laboratory-scale with wet sponges as input material for its dehumidification capacity and the power consumed to attain the target dryness. The front discharge model is found to have rapid drying capability and economy. Computational fluid dynamic tools are used to study the hot air flow behavior and flow uniformity inside the drying chamber. The front discharge model showed smooth uniform flow over the trays with fewer losses in the flow velocity. The front discharge model with higher drying rate, lower power consumption and uniform airflow distribution over the trays is chosen for the industrial-scale design.

Heat pump technologies of low temperature drying of capillary-porous materials spherical shape

Heat pump technologies have become widely used in space heating and air conditioning systems, and the heat pump can be used for low-temperature drying of capillary-porous materials.
 Recuperative and condensing heat pumps, which allow both drying and cooling of the material, have become the most widespread.
 The developed condensing heat pump drying unit with a mine chamber implements a low-temperature drying process of spherical capillary-porous materials at a drying agent temperature of 40-50°C with a decrease in material humidity by 11% to a final humidity of 8%.
 Experimental studies on a heat pump drying unit for drying capillary-porous materials of spherical shape indicated a significant reduction in average energy costs per process up to 3700 - 4100 kJ/kg of evaporated moisture. The increase in energy consumption increases significantly in the second part of the second period, where heat consumption can reach 5000 - 5350 kJ/kg of evaporated moisture.
 The use of condensing heat pumps for low-temperature drying of capillary-porous materials has shown high energy efficiency compared to existing drying technologies.

Heating with wind: Economics of heat pumps and variable renewables

Abstract With the growth of wind and solar energy in electricity supply, the electrification of space and water heating is becoming a promising decarbonization option. In turn, such electrification may help the power system integration of variable renewables, for two reasons: thermal storage could provide low-cost flexibility, and heat demand is seasonally correlated with wind power. However, temporal fluctuations in heat demand may also imply new challenges for the power system. This study assesses the economic characteristics of electric heat pumps and wind energy and studies their interaction on wholesale electricity markets. Using a numerical electricity market model, we estimate the economic value of wind energy and the economic cost of powering heat pumps. We find that, just as expanding wind energy depresses its €/MWhel value, adopting heat pumps increases their €/MWhel cost. This rise can be mitigated by synergistic effects with wind power, “system-friendly” heat pump technology, and thermal storage. Furthermore, heat pumps raise the wind market value, but this effect vanishes if accounting for the additional wind energy needed to serve the heat pump load. Thermal storage facilitates the system integration of wind power but competes with other flexibility options. For an efficient adoption of heat pumps and thermal storage, we argue that retail tariffs for heat pump customers should reflect their underlying economic cost.