Integrated Heat Pump Research Articles

Determination of the maximum LV grid hosting capacity for a rapid integration of photovoltaics, electric vehicles and heat pumps

Determination of the maximum LV grid hosting capacity for a rapid integration of photovoltaics, electric vehicles and heat pumps

EVALUATION OF ENERGY SAVING EFFICIENCY OF BOILER COMBINED WITH HEAT PUMP FOR SUPPLEMENTARY FEED WATER HEATING

This paper investigates the integration of heat pumps for heating boiler feedwater and evaluates the impacts of feedwater temperature and condensate recovery rates on fuel consumption, energy efficiency, and CO2 emissions. The results show that using heat pumps significantly reduces boiler fuel consumption, especially when the feedwater temperature increases and the condensate recovery rate is high. The COP (Coefficient of Performance) of the heat pump gradually decreases as the water temperature rises; however, heating the water at lower temperatures yields better economic and energy efficiency. Economically, heat pumps provide substantial benefits, with maximum cost savings achieved at a water temperature of 75°C. Additionally, integrating heat pumps reduces CO2 emissions, particularly in boilers without condensate recovery, with the highest emission reduction reaching 17.8 kgCO2 per ton of steam. These findings demonstrate that using heat pumps is not only energy-efficient and cost-effective but also contributes to environmental protection by reducing greenhouse gas emissions.

Scaled Designs of Solar Chimneys for Different Locations

A global motivation to reduce reliance on fossil fuels and transition to cleaner, renewable energy sources propels studies of innovative technologies to harness solar energy. This paper investigates the viability of a promising renewable energy technology, solar chimney power plants (SCPPs), in a domestic context. Using a scalable mathematical model, including thermodynamic processes within the collector, chimney, and turbine generator, the power output of SCPPs is assessed across five global locations with varying annual energy requirements: Aswan, Egypt, Cornwall, UK, Melbourne, Australia, Quito Ecuador, São Paulo Brazil. This research predicts a plant’s performance under differing plant geometries and meteorological inputs such as ambient temperature and solar irradiance, revealing that Aswan, Quito, and São Paulo can reliably produce year-round power, while Cornwall and Melbourne may need a supplementary energy supply in the winter months. The model establishes a linear relationship between collector radius and chimney height for each region to minimize geometry whilst fulfilling annual energy requirements, demonstrating that reducing one component size increases the other to maintain the required output. These geometries inform discussions of technology implementation, including the integration of an air-source heat pump (ASHP) to enhance performance, though it was found that the SCPP may not meet the power demand of the ASHP in Melbourne winter. Some lifecycle factors of the Melbourne and Quito plants are considered to assess the environmental viability of the technology.

Techno-Economic Comparative Assessment of High-Temperature Heat Pump Architectures for Industrial Pumped Thermal Energy Storage

Abstract The industrial sector is a key global source of wealth, but it is also recognized as a major challenge toward worldwide decarbonization. Today, the industrial sector requires more than 22% of the global energy demand as thermal energy and produces for this about 40% of the total CO2 emissions. Solutions to efficiently decarbonize the industrial sector are deemed. This work presents a comparative techno-economic performance assessment of a high-temperature heat pump (HTHP) integration within a molten salts (MSs) based power-to-heat system for industrial heat flexible generation. The main system performance is reported in terms of required working conditions and temperature for the heat pump and thermal demand size as well as reduction of the attainable levelized cost of heat (LCoH) against nonflexible electric boiler based systems. The impact of different industrial load profiles, electricity prices, heat pump capital cost, and heat pump real to Carnot efficiency ratio are also presented. The results highlight that the proposed system can be cost-competitive, particularly for thermal demand around 10 MW and waste heat temperatures above 80 °C. Under these conditions, LCoH reductions higher than 15%, with respect to the considered nonflexible electric boiler alternative, are attainable. These LCoH reductions are primarily driven by savings in electrical consumption as high as 30%. This study sets the ground for further power-to-heat techno-economic investigations addressing different industrial sectors and identifies main system and components design strategies, integrations, and targets.

Performance analysis of a system with integrated CO2 heat pumps and a PCM tank in different charging standards

Performance investigation of a system with an integrated heat pump and a phase change material (PCM) tank is seldom conducted in current studies, and the issue of identifying the optimal setting values of key variables in different charging standards and combinations of criteria is ignored. Therefore, in this study, we consider a system that integrates air- and water-source CO2 heat pumps and a PCM tank as a case study to address this issue. Experimentally validated CO2 heat pump and PCM tank models were used to simulate the system, and T-charging, Q-charging, and t-charging standards were considered. We concluded that the system coefficient of performance reduced by 10.5 %, 12.2 %, and 14.4 % when the setting stored energy was increased from 2.1 kWh to 4.5 kWh, setting outlet water temperature of PCM tank was increased from 28 °C to 34 °C, and setting charging time was increased from 0.5 h to 1.7 h in the Q-charging, T-charging, and t-charging standards, respectively. Multicriteria optimization was performed in different cases to determine the optimal setting values of the key variables. The optimal setting charging time is 1.7 h when weight factors of charging time and stored energy are 0.3 and 0.7, respectively. Thus, this study provides a distinctive perspective for investigating a system by integrating a heat pump and PCM tank by considering different charging standards.

Novel sustainable design of pressure-swing distillation coupled with natural decanting and Organic Rankine Cycle for separating n-propanol/benzene/water mixture

The separation of ternary azeotropic mixtures is a common challenge in the chemical industry due to the unique properties of azeotropes. This phenomenon complicates the separation processes, as traditional distillation methods may not effectively separate the components. The present work introduces a novel pressure-swing distillation (NPSD) process integrated with natural decanting for the effective separation of an n-propanol/benzene/water mixture. By exploiting the liquid–liquid envelope characteristics of the mixture, phase separation prior to distillation significantly enhances the separation efficiency. The NPSD process was optimised using the NSGA-II, addressing economic, environmental, and energetic objectives. Key findings reveal that the implementation of decanting allows the NPSD process to operate without substantial pressure adjustments, thereby facilitating fine separation more efficiently than conventional pressure-swing distillation designs. The proposed NPSD process can achieve up to 25.76 % savings in TAC while reducing CO2 emissions and improving energy efficiency. Furthermore, the integration of mechanical vapour recompression heat pump and Organic Rankine Cycle systems enhances energy saving, resulting in a TAC reduction of up to 31 % and a decrease in CO2 emissions of up to 38 % compared to existing energy-efficient designs. These findings highlight the potential of the NPSD-MVR-ORC system for sustainable chemical separation processes.

High-temperature heat pumps in industrial heating networks: A study on energy use, emissions, and economics

Industrial heat significantly contributes to global primary energy use and primarily relies on fossil-fuel combustion. Recovering residual heat in the industry offers a means to reduce overall energy use. However, the temperature and amount of residual heat available varies widely across industrial sites. Some may have a large amount of residual heat available at relatively high temperatures, while others may not have any residual heat available. Furthermore, for most industries, the residual heat available is at temperatures below 100 °C, while the heat demands are at higher temperatures. Hence, clustering these industries by industrial heating networks, using high-temperature heat pump integration, could offer a promising solution. Research on this concept regarding energy use, emissions and economics is however lacking in the literature. This study however distinguishes and subsequently compares three different heat network configurations in terms of their energy use, carbon emissions and financial appraisal. These configurations include a ‘consumer based heat upgrading network’, a ‘supplier based heat upgrading network’ and a ‘supplier based heat upgrading network with an additional hot water network’. For this purpose a generic methodology is developed, using first and second law principles completed with empirical data for performance and costs. The methodology is applied to data collected from ten companies clustered within the North Sea Port, Ghent (Belgium). The results indicate that the first configuration exhibits the most efficient use of energy and consequently also has the lowest carbon emissions. In addition it also has the lowest levelized cost of heat. This configuration shows, depending on maximum supply temperature of the heat pump, a potential reduction in carbon emissions ranging from 70 % to 80 % in comparison to natural gas boilers. Considering low gas prices, a positive financial appraisal is difficult without carbon taxation. On the other hand, an evaluation during the energy crisis of 2021–2022 indicates that the even without carbon taxation, the levelized cost of heat decreases by 19 % compared to a gas boiler at a maximum heat pump temperature of 160 °C. It was also found that in scenarios of dynamic energy prices a hybrid configuration of a consumer based heat upgrading network and a natural gas boiler could lower the LCOH compared to the individual solutions, by up to 7.6 % compared to the best individual solution. This is done by activating the technology with the lowest operational cost in each time frame.

The apparatus for atmospheric water harvesting in an arid climate - Prototype design and testing in laboratory conditions

The paper describes the development of a prototype system for water extraction from the air. The aim was to develop a device that allows one to autonomously obtain, without the need for external energy, an annual average of 100 L of water per day during extreme desert conditions. In this paper, a mathematical model simulating the operation of the unit for extracting water from the air in any climatic conditions is presented. Psychrometric calculations for different climatic conditions were carried out for two basic principles: condensation and sorption. The analyses confirmed that devices based on the condensation of water vapour from the air can only be used to a limited extent in extreme desert conditions. The average water production of a condensation-based system is only 20 l/day in Riyadh, with an air flow rate of 2000 m3/h. A unit with a desiccant wheel and an integrated heat pump was designed for water harvesting from the air. The prototype of the unit was tested in a climate chamber with the possibility of adjusting the climatic conditions and the presented mathematical model was experimentally verified. The final prototype designed for a nominal outdoor air flow rate of 2000 m3/h will produce 168 l of water per day under dry desert conditions (Riyadh) with continuous operation. The verification of the computational model allows one to determine the real water production and the required unit performance. An analyses of energy requirements and evaluation of levelized cost of water (LCOW) have been performed. Sorption unit has lower LCOW in target arid desert climate and electricity prices under 0.1 EUR/kWh compared to direct condensation technology.

Combining energy generation and radiant systems: Challenges and possibilities for plus energy buildings

Radiant heating and cooling (RHC) systems are being more widely adopted considering the well-known technical advantages: increased thermal comfort, space saving, and reduced energy use. Since the building sector is currently one of the largest consumers of fossil fuels, many directives and regulations have been enacted to address the intense concern about energy use for space conditioning.Even though radiant systems are considered as an energy efficient technology for building heating and cooling, more effort is needed to fulfil the zero energy requirements outlined by recent standards and directives. Renewable Energy Sources (RES) are an effective solution to avoid using finite fossil fuels and related geopolitical issues enhanced by the recent world conflicts. Despite being primarily intermittent and subject to economic and regional constraints, RES offer suitable temperature levels to supply low temperature heating and high temperature cooling operation, a major advantage of RHC system.Although a limited number of studies directly report energy savings or CO2 emission reduction as the main outcomes of the research related to this combination, valuable insights have been obtained for the present review. Primary energy can decrease between 40% and 80% with different integration of RHC, photovoltaic, heat pumps and district heating. TABS can lead to load shifting up to 100%, allowing an increased self −consumption of renewable energy.This paper provides evidence on whether coupling radiant systems with renewables is a promising strategy for achieving nearly-zero annual energy balances in building stocks. It investigates recent trends, limitations and potential to support decarbonization goals.

Optimisation of Integrated Heat Pump and Thermal Energy Storage Systems in Active Buildings for Community Heat Decarbonisation

The electrification of residential heating systems, crucial for achieving net-zero emissions, poses significant challenges for low-voltage distribution networks. This study develops a simulation model to explore the integration of heat pumps within active building systems for community heating decarbonisation. The model optimises heat pump operations in conjunction with thermal energy storage units to reduce peak demand on low-voltage networks by using real-time measured electricity demand data and modelled heat demand data for 76 houses. The study employs an algorithm that adjusts thermal storage charging and discharging cycles to align with off-peak periods. Three scenarios were simulated: a baseline with unoptimised heat pumps, a fixed threshold model, and an active building model with daily optimised thresholds. The results demonstrate that the active building model achieves a 21% reduction in peak demand on the low-voltage substation compared to the baseline scenario; it also reduces the total electrical energy consumption by 12% and carbon emissions by 17%. The fixed threshold scenario shows a 16% improvement in peak demand reduction, but it also shows an increase in energy consumption and emissions. These findings highlight the potential of active buildings to enhance the efficiency and sustainability of residential energy systems, marking a significant step toward decarbonising residential heating while maintaining grid stability.

Analysis of the CO2 + C2Cl4 mixture in high temperature heat pumps: Experimental thermal stability, liquid densities and cycle simulations

Transcritical heat pumps working with CO2-based mixtures with a low-volatility dopant are found to achieve good performances in thermally integrated heat pumps, especially when sensible heat sources and heat sinks are considered. This paper introduces in literature tetrachloroethylene, C2Cl4, as CO2-dopant for the mixture to be adopted as working fluid in high temperature heat pumps. To calibrate the thermodynamic model used in the cycle simulations, an experimental characterization on the mixture is proposed: liquid densities of the mixtures are measured, in a wide range of concentration, optimizing the binary interaction parameter of the Peng Robinson equation of state. Moreover, the thermal stability of pure C2Cl4 is experimentally evaluated, identifying the maximum allowable compressor outlet temperature between 200 °C and 250 °C, with a decomposition rate below 1 %/year if the fluid is kept at temperatures around 200 °C. Then, the potentialities of this very high temperature heat pump are assessed in spray dryer applications: a coefficient of performance around 3.38 is obtained for a conventional spray dryer plant, corresponding to 73 % of second law efficiency, considering an air flow heated from ambient temperature to 200 °C as the sink, while cooling the sensible heat source, available at 76 °C, below 30 °C. As term of comparison, the same system adopting propane, instead of the CO2 + C2Cl4 mixture, would achieve a coefficient of performance and second law efficiency of 2.94 and 64 %, respectively.

Benefits of zeotropic mixture for heat pump water heater with phase change material thermal energy storage

Integrating heat pump water heater (HPWH) into latent heat thermal energy storage (LHTES) with phase change material (PCM) has been recognized as a promising way to mitigate the energy use for heating water in the building sector. This paper uses zeotropic mixture R1234yf/R1234ze(Z) in HPWH and spherical PCM encapsulations in LHTES. The mathematical model is established and validated. Effects of zeotropic mixture composition, working fluid flow rate and heat transfer fluid (HTF) flow rate are discussed to reveal the instantaneous behaviors and overall performance of the integrated system. The results indicate that as the charging process progresses, the condensing pressure of the system steadily increases, leading to a decline in COP. By employing zeotropic mixtures, the system performance can be effectively improved, with the highest COP of 2.68 when the mass fraction of R1234ze(Z) is 70 %, which represents an 18.1 % and 6.8 % improved COP compared to R1234yf and R1234ze(Z), respectively. A smaller refrigerant flow rate or a larger HTF flow rate contributes to a higher COP. For heat storage capacity in LHTES, a higher mass fraction of R1234ze(Z) and a larger refrigerant flow rate are preferable, while a smaller HTF flow rate is beneficial. Finally, a multi-objective optimization is carried out. Results suggest that the best overall performance is achieved with a COP of 2.70 and a heat storage capacity of 629.24MJ, under conditions of the mass fraction of R1234ze(Z) at 70 %, a refrigerant flow rate of 0.28 kg/s, and an HTF flow rate of 0.46 kg/s.

Multi-objective optimization and influence degree analysis of the thermally integrated HP-ORC carnot battery based on the orthogonal design method and grey relational analysis

Thermally integrated heat pump (HP)-organic Rankine cycle (ORC) Carnot battery is a promising solution for efficient energy storage and waste heat utilization. Firstly, in order to research the influence degree of the operating parameters on the system performance, single-objective optimization is conducted by the orthogonal design method. Then, multi-objective optimization is conducted by combining the grey relational analysis (GRA) and orthogonal design method to assess the comprehensive performance of the system. The importance order and contribution rates of the operating parameters and the optimal operating combinations are determined. Finally, in order to explore the influence mechanism of the parameters on the system performance, the influence of the parameters on the subsystems and the subsystems on the whole system is quantitatively analyzed. The results show that thermal storage temperature difference, waste heat temperature difference and cold source temperature are the most important parameters affecting the comprehensive performance of the whole system. Under the optimal operating conditions, round-trip efficiency, exergy efficiency, energy storage capacity (ESC), energy storage density (ESD) and levelized cost of storage (LCOS) are 47.05 %, 22.66 %, 1943 kW, 2.90 kWh/m3 and 0.38$/kWh, respectively. Compared to the ORC subsystem, the HP subsystem is more important to round-trip efficiency and exergy efficiency.

Multilayer decoupling control of photovoltaic integrated heat pump based on expected value

Abstract In this paper, a multilayer decoupling control method for photovoltaic heat pumps based on expected values is proposed, which aims to achieve the optimal operation of the photovoltaic heat pump system and photovoltaic heat pump system. This method predicts the output energy of photovoltaic photovoltaic system and realizes multilayer decoupling control based on the load demand of the heat pump system. In order to adapt to the change in environment, the adaptive fuzzy PID compound control method is adopted to optimize the control strategy. Experimental results show that this method can effectively improve the system efficiency, reduce energy consumption, and demonstrate good adaptability and stability.

Integrated heating and cooling system with borehole thermal energy storage for a greenhouse in Romania

The IDA Indoor Climate and Energy (IDA ICE) simulation tool is used to model a research greenhouse in Bucharest, Romania, equipped with a recently implemented energy system that includes an integrated heat pump system, Air Handling Units (AHUs), a dry cooler, and boreholes for thermal energy storage. The integrated heat pump system is designed to provide year-round heating and cooling of the greenhouse. The performance of the system is assessed through simulations conducted for one week in summer (July 2023) and one week in winter (December 2023), using recorded weather data for each respective period. Results from the IDA ICE model are compared with values derived from onsite sensor measurements. During the summer week, the model generally aligns with measured air temperatures in the greenhouse compartment. The total cooling simulated in the model is 26.5 kWh/m2, compared to 27.2 kWh/m2 calculated from onsite measurements. Hourly discrepancies were observed, potentially due to the heat pump system operating at reduced capacity during this summer. In the winter week, the measured and simulated temperatures fall within a comparable range. The calculated and simulated cumulative heating show excellent agreement, both at 15.1 kWh/m2.

An analytical solution to optimal heat pump integration

Heat pump integration has a large potential for reducing carbon emissions and operating costs of industrial processes. The Break-even COP method determines the maximum economically- or environmentally feasible heat pump temperature and the level of process heat electrification under specified economic conditions. However, this method fails to capture the optimal heat pump temperature and the possible emissions- and costs reduction in sensible heat processes. The present work introduces an analytical equation based on the Lorenz efficiency approach to determine the optimal heat pump sink temperature, maximizing the operating costs savings or the emission savings. Furthermore, it advances the break-even method to account for heat pumps with a temperature glide by applying a Lorenz efficiency approach. The method is applied to a spray-drier case study, showing a reduction on operation costs of 7.8 % and emissions by 11.9 % by a partial process electrification of 32 %. A parameter study is conducted, underscoring the importance of accurate predictions of the Lorenz efficiency factor and the electricity-to-fuel price and emissions ratios in heat pump integration studies.

Operation optimization in large-scale heat pump systems: A scheduling framework integrating digital twin modelling, demand forecasting, and MILP

The integration of large-scale heat pumps and thermal energy storage can facilitate sector coupling, potentially lowering heating and cooling costs in industries and buildings. This cost reduction can be extended by optimizing the utilization of the available thermal energy storage capacity in accordance to fluctuating electricity prices. Although the literature offers methods for optimizing the operation of these integrated systems, they often overlook the impact of heat pump performance degradation over time, such as from fouling. This oversight can lead to suboptimal system performance and inaccurate operational cost estimates. The present study addresses this gap by introducing a novel operational scheduling framework that aimed to reduce the operational costs of a commercial large-scale heat pump system. The system comprised an open cooling tower, a thermal storage tank and two heat pumps affected by fouling. The framework incorporated a mixed-integer linear programming (MILP) model, thermal demand forecasting, and heat pump performance maps that account for varying fouling levels. These maps were obtained from online calibrated simulation models used as digital twins of the heat pumps. The results demonstrated that the proposed framework enhanced the thermal energy storage utilization in response to variable electricity prices and adjusted the heat pump operation based on the influence of fouling. This resulted in a reduction of operational costs of up to 5% compared to the conventional operation of the system. These savings were observed to vary depending on the forecasting accuracy and the prevailing fouling levels. Overall, this study demonstrates the potential of using the proposed framework for cost reduction in large-scale heat pump systems.

Performance simulation and analysis of a solar-assisted multifunctional heat pump system for residential buildings

ABSTRACT As building electrification is recognised as an important opportunity to reduce greenhouse gas emissions, the integration of solar energy and heat pump represents a promising solution towards net-zero carbon buildings. This paper presents a hybrid multifunctional solar-assisted heat pump (SAHP) system that can provide space heating, space cooling, domestic hot water, and onsite electricity generation. Photovoltaic-thermal collectors are used for electricity generation, heat collection, and radiative cooling. The system design and controls support fourteen operational modes involving different components. TRNSYS software is used to model and simulate the multifunctional SAHP system. With a 2-m3 storage tank and 30-m2 PVT collectors, the multifunctional SAHP system has a seasonal performance factor of 2.7 in Baltimore and 3.7 in Las Vegas. The onsite electricity generation can cover 53% of the building’s electricity needs in Baltimore and 83% in Las Vegas.

Urban energy transition: Sustainable model simulation for social house district

Energy communities (EC) play a crucial role in driving the transition towards renewable energy sources within urban areas. This study focuses on the implementation of EC within linear mass housing in Rome, with particular attention given to the Tor Bella Monaca district. The research proposes and simulates six energy community distinct scenarios using the Urban Modelling Interface (UMI) and Simulink in order to advance understanding of this topic. These scenarios evaluate the integration of photovoltaic systems, heat pumps, and energy storage systems to determine their comprehensive effect on renewable energy production, CO2 emission reduction, and the enhancement of self-consumption. The study findings show that higher electrification levels in an energy community lead to greater consumption of renewable energy and reduced reliance on the grid. The integration of heat pumps and energy storage further enhances energy consumption and self-sufficiency creating sustainable energy models in urban environments. With an increase in self-consumption factor and self-sufficiency factor of 0.15–0.30 and 0.11–0.13, respectively, depending on the scenario. The research highlights the importance of a thorough assessment of technology sizing and integration in order to enhance self-consumption and decrease CO2 emissions. It proposes investigating the incorporation of both thermal and electrical storage to optimize self-consumption. Finally, the simulated scenarios underwent flexibility analyses to determine the precise energy flow capacity and the optimal setting identified through economic evaluation.

Analysis on integration of heat pumps and thermal energy storage in current energy system: From research outputs to energy policies

This paper presents a comprehensive examination of the integration of heat pumps and thermal energy storage (TES) within the current energy system. Utilizing bibliometric analysis, recent research trends and gaps are identified, shedding light on the evolving landscape of this dynamic field. The study delves into the research outputs since 1969, offering insights into the global scholarly contributions shaping the discourse. Furthermore, an extensive policy analysis is conducted, focusing on seven countries with the highest research output. The interplay between research advancements and energy policies is explored, providing an understanding of the practical implications of the integration of heat pumps and TES. An understanding is tried to reach as how research and policy sector influence each other. This analysis contributes not only to the academic understanding of the subject but also informs policymakers about potential pathways for enhancing energy efficiency and sustainability in heating and cooling sector.