Solutions For Heat Recovery Research Articles

EMB3Rs: A game-changer tool to support waste heat recovery and reuse

At a time when European countries try to cope with escalating energy prices while decarbonizing their economies, waste heat recovery and reuse arises as part of the solution for sustainable energy transitions. The lack of appropriate assessment tools has been pointed out as one of the main barriers to the wider deployment of waste heat recovery projects and as a reason why its potential remains largely untapped.The EMB3Rs platform emerges as an online, open-source, comprehensive and novel tool that provides an integrated assessment of different types of waste heat recovery solutions, (e.g. internal or external) and comprises several analysis dimensions (e.g. physical, geographical, technical, market, and business models). It has been developed together with stakeholders, and tested in a number of representative contexts, covering both industrial and heat network applications. This has demonstrated the enormous potential of the tool in dealing with complex simulations, while delivering accurate results within a significantly lower time-frame than traditional analysis.The EMB3Rs tool removes important barriers such as analysis costs, time and complexity for the user, and aims at supporting a wider investment in waste heat recovery and reuse by providing an integrated estimation of the costs and benefits of such projects. This paper describes the tool and illustrates how it can be applied to help unlock the potential of waste heat recovery across European countries.

Industrial waste heat potential and heat exploitation solutions

The industrial waste heat potential in EU countries and UK is assessed using the most recent data, based on an established methodology that allows to estimate this underexplored resource per country, temperature level and industrial branch. This methodology is applied here combining two previous studies using the most recent energy balances data from Eurostat and other indicators of 2021. The waste heat potential and heat demand are then estimated, in order to identify the progress towards reduction of waste energy. It has been revealed that this progress is significant in terms of energy intensity, leading to a reduction of waste heat from 2015 to 2021, but still this heat amount is large and equal to 221.32 TWh/year in 2021. The second part of this work concerns the assessment of three mainstream solutions to exploit this waste heat: direct heat recovery, heat-to-power conversion, and heat upgrading with high-temperature heat pumps. The heat and electricity production potential of these solutions is identified, followed by the estimation of greenhouse gas emissions savings introduced by each one. It has been shown that the direct heat recovery solution brings the highest savings of almost 50 million CO2-eq. tonnes/year, followed by the heat upgrading one.

Enhanced Selective Ion Transport in Highly Charged Bacterial Cellulose/Boron Nitride Composite Membranes for Thermo-Osmotic Energy Harvesting.

Significant untapped energy exists within low-grade heat sources and salinity gradients. Traditional nanofluidic membranes exhibit inherent limitations, including low ion selectivity, high internal resistance, reliance on nonrenewable resources, and instability in aqueous solutions, invariably constraining their practical application. Here, an innovative composite membrane-based nanofluidic system is reported, involving the strategy of integrating tailor-modified bacterial nanofibers with boron nitride nanosheets, enabling high surface charge densities while maintaining a delicate balance between ion selectivity and permeability, ultimately facilitating effective thermo-osmotic energy harvesting. The device exhibits an impressive output power density of 10 W m-2 with artificial seawater and river water at a 50 K temperature gradient. Furthermore, it demonstrates robust power density stability under prolonged exposure to salinity gradients or even at elevated temperatures. This work opens new avenues for the development of nanofluidic systems utilizing composite materials and presents promising solutions for low-grade heat recovery and osmotic energy harvesting.

Hybrid Ventilation Systems for Reduced Lifetime Emissions in Cold Climates

Heating, ventilation, and air conditioning systems are notable sources of emissions in buildings. In cold climates, mechanical ventilation systems are characterized by significant initial embodied emissions but benefit from reduced operational emissions related to heating energy. On the other hand, natural ventilation systems have the advantage of lower initial embodied emissions but will use more heating energy, in cold climates, for the same atmospheric quality, due to the general lack of efficient heat recovery solutions. Hybrid ventilation systems are hybrids of these, using a combination of driving forces. This study utilized a life cycle assessment (LCA) to compare lifetime emissions of hybrid and mechanical ventilation systems in a Nordic climate. Findings suggest that hybrid ventilation systems can yield lower lifetime emissions, provided upfront emissions are reduced without significantly increasing energy consumption. Reduction potential in upfront emissions is more substantial in open landscape offices than classrooms due to higher person density in classrooms necessitating more fresh air, limiting reductions that can be achieved without thermal discomfort during the winter season. Our study shows the feasibility of reducing the carbon footprint of ventilation systems by employing hybrid climatization strategies.

Cold Climate Challenges: Analysis of Heat Recovery Efficiency in Ventilation Systems

As building energy consumption gains ever-increasing attention worldwide, the focus on addressing it through the examination and optimization of efficient heat recovery solutions continues to intensify. With well-insulated and airtight buildings, the proportion of heating needs attributed to ventilation is growing, leading to the widespread integration and optimization of heat recovery solutions in mechanical ventilation systems. Heat recovery in ventilation is a highly efficient strategy for reducing heat losses and conserving energy. This study involves the investigation of a ventilation unit installed in an apartment situated in Riga, Latvia, as a practical examination of heat recovery system efficiency within the Latvian climate conditions, representing a cold climate region. The objective of this study was to examine the heat recovery efficiency of the ventilation system in the Latvian climate with variable outdoor and exhaust air parameters, given that the dry heat recovery efficiency is different from the actual heat recovery efficiency. The ventilation unit was equipped with a plate heat exchanger at an airflow rate of 105 m3/h. To evaluate heat recovery efficiency, extensive measurements of air temperature and relative humidity were conducted. The collected data was analyzed, employing statistical regression analysis to ensure measurement reliability and assess correlations. The findings indicated a strong correlation between variables such as heat content, moisture content, and sensible air parameters. It was observed that the actual heat recovery efficiency was 6% higher than the calculated dry efficiency, emphasizing the importance of considering real-world conditions in heat recovery assessments. Additionally, regression analysis demonstrated a positive linear correlation with a coefficient of 0.77, highlighting the dependency between actual measurements and the theoretical model. These quantitative outcomes provide essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments. Moreover, this study highlights the strong correlation between variables such as heat content, moisture content, and sensible air parameters. Findings offer essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments.

Recovery boiler back-end heat recovery

Sustainability and efficient use of resources are becoming increasingly important aspects in the operation of all industries. Recently, some biomass-fired boilers have been equipped with increasingly complex condensing back-end heat recovery solutions, sometimes also using heat pumps to upgrade the low-grade heat. In kraft recovery boilers, however, scrubbers are still mainly for gas cleaning, with only simple heat recovery solutions. In this paper, we use process simulation software to study the potential to improve the power generation and energy efficiency by applying condensing back-end heat recovery on a recovery boiler. Different configurations are considered, including heat pumps. Potential streams to serve as heat sinks are considered and evaluated. Lowering the recovery boiler flue gas temperature to approximately 65°C significantly decreases the flue gas losses. The heat can be recovered as hot water, which is used to partially replace low-pressure (LP) steam, making more steam available for the condensing steam turbine portion for increased power generation. The results indicate that in a simple condensing plant, some 1%–4% additional electricity could be generated. In a Nordic mill that provides district heating, even more additional electricity generation, up to 6%, could be achieved. Provided the availability of sufficient low-temperature heat sinks to use the recovered heat, as well as sufficient condensing turbine swallowing capacity to utilize the LP steam, the use of scrubbing and possibly upgrading the heat using heat pumps appears potentially useful.

Thermoelectric Generator Using Low-Cost Thermoelectric Modules for Low-Temperature Waste Heat Recovery

One of the most significant problems in industrial processes is the loss of energy according to the sort of heat. Thermoelectrics are a promising alternative to recovering this type of thermal energy, as they can convert heat into electricity, improving the industrial efficiency of the process. This article presents the characteristics of low-cost thermoelectric modules typically used for generation (SP1848-27145SA (TEG-GEN)) and refrigeration (TEC1-12706 (TEC-REF)), both utilized in this research for heat recovery. The modules were evaluated against various configurations, source distances, and distributed systems in order to determine optimal recovery conditions. The experiments were conducted both at the laboratory level and in a large-scale furnace of the traditional ceramics industry, and they revealed that even refrigeration modules are suitable for energy recovery, particularly in developing countries, whereas other generators are more expensive and difficult to obtain. These thermoelectric generators were tested for low-temperature heat recovery in regular furnaces, and the results are to be implemented elsewhere. Results show that even the thermoelectric refrigeration modules can be a solution for heat recovery in many heat sources, which would be particularly strategic for developing countries.

Energy Efficiency for Marine Application: Waste Heat Recovery Solutions and Photovoltaics in Long-Distance Shipping

This work investigates the potential of three different energy efficiency technologies on a Very Large Crude Carrier: Organic Rankine Cycle and adsorption chiller for waste heat recovery as well as photovoltaics for the integration of Renewable Energy Sources. The analysis uses operational data acquired from an energy management system. It shows that the impact of the weight of each technology is negligible when compared to fuel savings and emission reductions. Based on the sailing conditions identified from the operational data, the study presents an estimation of the theoretical and technical potential showing the overall savings, which can be achieved on an absolute scale. Moreover, the achievable improvement of EEOI and CII are presented. The available waste heat and the electricity demand of the vessel are identified as the limiting factors for the technology implementation.

Waste heat recovery solution based on a heat pipe heat exchanger for the aluminium die casting industry

An analysis of the end use of energy in the EU reveals that industry is one of the three dominant categories, which accounts for 26.1% of the final end use of energy. In the case of the aluminium industry, approximately 70% of energy consumption is due to heat and thermal processes, highlighting a vast potential for waste heat recovery technologies. Within the aluminium die casting industry, liquid aluminium is cast, formed, cooled, and further processed within a thermal heat process, which includes three sub-processes: solubilising, quenching, and ageing. In the case presented, a thermal heat process is the second most energy intensive process within the factory, and the ageing heat treatment furnace accounts for 15% of the thermal heat process. The thermal heat treatment generates a significant amount of waste heat. The recovery of that waste heat, with minimal risk of cross contamination between streams and reduced chance of equipment failure, has been achieved via the use of a heat pipe heat exchanger (HPHE). The HPHE has been designed, manufactured, and installed in the solution furnace exhaust stack. The HPHE was designed to recover up to 88.6 kW in steady state operating conditions at 400 °C. The return on investment has been evaluated at 35 months with an expected CO2 emissions reduction of 86 tCO2/year when best engineering practices are applied. Furthermore, a theoretical modelling tool to predict the thermal performance of the HPHE was developed and validated within a ±20% deviation from the experimental results. This paper further presents the development of the theoretical model to allow a characterisation of HPHE technology and will act as a guideline for the design of HPHEs within the aluminium industry.

Reversible high-temperature heat pump/ORC for waste heat recovery in various ships: A techno-economic assessment

An alternative waste heat recovery solution for ships is examined, relying on a reversible unit. This unit switches its operation between an organic Rankine cycle (ORC) for electricity production and a high-temperature heat pump (HTHP) for steam generation, using the refrigerant R1233zd(E), with the compressor/expander operating with a similar volume ratio that favors the performance. The waste heat of the engine's cooling water is exploited, when the ship is both at sea and at port, increasing the capacity factor. The performance of each mode has been examined at reference conditions in relation to the heat exchangers' sizing for the same compressor/expander, showing that the evaporator should be as large as possible to maximize the efficiency. The costs have been then assessed and compared with HTHP-only and ORC-only solutions, leading to the cost-optimal sizing that minimizes the discounted payback period (PBP). The reversible unit has been then up-scaled to match the steam needs and waste heat availability of several ship types, calculating the net fuel savings and PBP. The latter becomes much shorter than the one of the individual solutions, and ranges from 3.5 to 5 years, reduced to less than 4 years in case the fuel prices increase by 20%.

Combined energetic, economic and climate change assessment of heat pumps for industrial waste heat recovery

The recovery of waste heat represents a promising opportunity to reduce greenhouse gas (GHG) emissions from industrial sectors. The current development of heat recovery technologies can provide industries with several options for retrofitting their heat generation systems. Although past studies estimated the resulting savings in GHG emissions for specific industries or facilities, work is still needed to fully substantiate the expected benefit and the competitiveness of these alternatives, taking into account data at country scale (e.g. long-term reduction targets, energy cost, etc.). Hence, in this study, a new methodology is developed to determine the minimum conditions for waste heat recovery solutions to enable compliance with the targets from the Paris Agreement, taking 2030 and 2050 as reference years. It is applied to several industrial sectors for 24 EU countries, focusing on mechanical heat pump solutions (MHPs). Results indicate that all countries are compliant in 2050 for MHP integration with low temperature lift (like ammonia production) and 21 countries are compliant for high temperature lift (like food industry). The main constraint to the development of the MHP technology in 2030 is found to be economic, while in 2050, the main barrier for countries that do not reach the reduction targets is a too high carbon intensity of electricity generation. To accommodate the relatively long lifetime of the heat production system, the future MHP roadmap should therefore anticipate these potential barriers including carbon footprint of electricity network, working fluids and gas to electricity price ratio. In addition to meeting the 2030 requirements by a large margin, this strategy would factor in constraints associated with the long-term investments in MHPs. To further expand such foresight analysis, our methodology can be duplicated to other technologies than MHPs, so it can help industry decision-makers select the most suitable waste heat recovery options for a given industrial process in a specific country.

Novel designs of thermoelectric generator for automotive waste heat recovery: A review

<abstract> <p>Many worldwide scientists have concentrated on using waste heat recovery technology in automotive applications because of increasingly strict fuel consumption. The thermoelectric generator (TEG) has garnered significant interest in the automobile sector as a viable waste heat recovery solution over the past several decades. A short survey of thermoelectric materials and heat exchangers for TEG systems is initially presented in this paper. To overcome the heat exchanger's current shortcomings, some previous studies designed a variety of the heat exchanger geometry of the TEG system. They suggested concentric cylindrical TEG system utilizes an annular thermoelectric module instead of the traditional square-shaped one. It uses the heat pipe's benefits to improve radial heat transmission. A comparison of the water-inside and gas-inside arrangements indicated that the water-inside concentric cylindrical TEG system provided a greater power output in our simulations to test the performance of the proposed system.</p> </abstract>

Conceptual design and performance evaluation of an innovative high temperature ceramic heat exchanger

The development of an innovative and highly efficient heat exchanger (HE) solution for gas-gas heat recovery is one of the major objectives of the HYDROSOL-beyond project which aims at enhancing the process efficiency for producing H2 from water dissociation with concentrated sunlight. Because of the very high temperature level of the process (up to 1’400°C), an innovative ceramic HE was proposed with an integrated lattice structure, as secondary surface, to maximize the heat transfer. To assist the design of the HE, a multiscale approach was adopted: a 1D model based on global correlations was developed and a 3D computational fluid dynamics model of the secondary surfaces were generated. The former was applied to assess the performance of the entire HE; while, the latter was exploited to study in detail the thermo-fluid dynamics behavior of a HE core element and to provide the global correlations to be integrated into the 1D model. The effect of the number of lattice layers, located into each channel, on the HE effectiveness was evaluated showing that reducing the height of the secondary structure allows to improve the HE effectiveness from 72% up to 94%.

Costs vs. Flexibility of Process Heat Recovery Solutions Considering Short-Term Process Variability and Uncertain Long-Term Development

To significantly decrease fossil carbon emissions from oil refineries, a combination of climate mitigation options will be necessary, with potential options including energy efficiency, carbon capture and storage/utilization, biomass integration and electrification. Since existing refinery processes as well as many of the potential new processes are characterized by large heating demands, but also offer large opportunities for process excess heat recovery, heat integration plays a major role for energy efficient refinery operation after the implementation of such measures. Consequently, the process heat recovery systems should not only be able to handle current operating conditions, but also allow for flexibility towards possible future developments. Evaluation of the flexibility of process heat recovery measures with both these perspectives enables a more accurate screening and selection of alternative process design options. This paper proposes a new approach for assessing the trade-off between total annual cost and potential operating flexibility for the heat exchanger network in short-as well as in long-term perspectives. The flexibility assessment is based on the evaluation of a flexibility ratio (similar to the conventional flexibility index) to determine the range in which operating conditions may vary while at the same time achieving feasible operation. The method is further based on identification of critical operating points to achieve pre-defined flexibility targets. This is followed by optimization of design properties (i.e., heat exchanger areas) such that feasible operation is ensured in the critical operating points and costs are minimized for representative operating conditions. The procedure is repeated for a range of different flexibility targets, resulting in a curve that shows the costs as a function of desired flexibility ratio. The approach is illustrated by an example representing a heat exchanger network retrofit at a large oil refinery. Finally, the paper illustrates a way to evaluate the cost penalty if the retrofit is optimized for one operating point but then operated under changed conditions. Consequently, the presented approach provides knowledge about cost and flexibility towards short-term variations considering also changes in operating conditions due to long-term development.

Comprehensive numerical model for the analysis of potential heat recovery solutions in a ceramic industry

Abstract Heat recovery opportunities and total plant energy efficiency improvements need to be evaluated before manufacturing the real components when addressing the energy and economic effectiveness in industrial applications. Numerical modelling of the complete energy systems can be a key design tool in order to investigate the potential solutions to improve the performance of the considered system. In this study, a 0D/1D numerical analysis and transient system simulation analysis are adopted to investigate the energy efficiency enhancement given by the application of a heat pipe-based heat exchanger in the ceramic industry. The thermal power is recovered from the exhaust gases of the kilns used to fire the tiles. The numerical model includes all the main components of the heat recovery system: the primary side of the exhaust gases, the heat exchanger, the secondary circuit of the heat transfer fluid and the heat sink where the thermal power is exploited. Particular care is devoted to the modelling of the heat pipe-based heat exchanger and the necessary control strategy of the system; a specific model for the simulation of the secondary side pump is also accounted for in the analysis. The numerical results of the primary circuit are validated against experimental measurements carried out on the real ceramic facility. The good agreement between the numerical and experimental results demonstrates that the numerical model is an appropriate tool for investigating the energy efficiency enhancement of an industrial plant and for evaluating different configurations and solutions in order to fulfil the industry requirements.

A user workflow for combining process simulation and pinch analysis considering ecological factors

Abstract This paper aims to develop an innovative and practical method to accelerate Pinch Analysis problems using a combination of process integration, process simulation tools, and life cycle assessment techniques to design effective industrial energy efficiency measures rapidly. Data extraction and analysis is accelerated using the workflow, reducing pinch analysis duration, and therefore cost. This lowers financial barriers and is expected to help facilitate an increase in the number of conducted pinch analyses each year. An innovative ecological targeting step has been included in the workflow, which represents the option for end-users to further their CO2 savings, once energy targeting has been completed on a purely cost basis. It is expected that optimizing for costs first will enable the implementation of heat recovery solutions in industry. The methodology is applied to an example case study, and the learnings from industrial application is reported.

Simulation and Economic Research of Circulating Cooling Water Waste Heat and Water Resource Recovery System

Industrial circulating cooling water contains a large amount of low-quality energy, which is lost to the environment through cooling towers. It is of great significance and potential to recover the waste heat to improve energy-saving effects and economic efficiency. However, the effect of common water harvesting and energy saving devices is not significant. Heat pumps have been shown to be effective in improving low-quality heat energy in energy conversion systems, although there are not many applications of heat pump scenarios in engineering practice. Based on this, a recovery solution of circulating cooling water waste heat and water resource using lithium bromide absorption heat pump has been put forward. The energy-saving performance of the recovery system was simulated and analyzed using Aspen Plus V10.0 (Bedford, MA, USA) to explore the effects of the parameters of the working medium in evaporators, condensers, absorbers, generators, heat exchangers, etc., and the modelling results indicated that the evaporation pressure and temperature have a great influence on the system COP (coefficient of performance) and can raise the thermal economy of the system. The heat from driving steam and heating capacity both increased with the increase in generating temperature, while the increase in temperature difference between evaporation and condensation inhibits the COP of heat pump systems. Furthermore, economic analyses and comparisons of the recovery solutions were conducted and the recovery solution of circulating cooling water waste heat with heat pump had the best economic performance due to the annual income from the recovery of waste heat and water resource. The static payback period results indicate that the recovery solution from circulating cooling water waste heat with a heat pump has better economic performance than the scenario with a cooling tower. The waste heat recovery solution with a heat pump can improve the thermal economy of the system and has a great guiding significance for engineering practice.

Evaluation of the Energy Efficiency Improvement Potential through Back-End Heat Recovery in the Kraft Recovery Boiler

Sustainability and energy efficiency have become important factors for many industrial processes, including chemical pulping. Recently complex back-end heat recovery solutions have been applied to biomass-fired boilers, lowering stack temperatures and recovering some of the latent heat of the moisture by condensation. Modern kraft recovery boiler flue gas offers still unutilized heat recovery possibilities. Scrubbers have been used, but the focus has been on gas cleaning; heat recovery implementations remain simple. The goal of this study is to evaluate the potential to increase the power generation and efficiency of chemical pulping by improved back-end heat recovery from the recovery boiler. Different configurations of heat recovery schemes and different heat sink options are considered, including heat pumps. IPSEpro simulation software is used to model the boiler and steam cycle of a modern Nordic pulp mill. When heat pumps are used to upgrade some of the recovered low-grade heat, up to +23 MW gross and +16.7 MW net power generation increase was observed when the whole pulp mill in addition to the boiler and steam cycle is considered as heat consumer. Combustion air humidification proved to yield a benefit only when assuming the largest heat sink scenario for the pulp mill.

Defrosting and Frost Protection Measurements of Heat Recovery in Cold Climate

The installation of technical solutions for heat recovery from the ventilation air is a very important step, both with respect to improving the indoor climate and as an energy-saving measure. Ventilation without heat recovery use a substantial part of an entire building’s heating use, especially if the building is a low energy building. To realize a large implementation of heat recovery property owners must increase their knowledge about how these systems work and they must be able to rely on them functioning properly. The function and performance of a ventilation system when it comes to heat recovery can be a problem as soon as temperatures drop far below zero. When freezing occurs some form of defrosting is required and this can lead to indoor climate problems and to little or no heat recovery being obtained, which will reduce the energy efficiency and, at the same time, may compromise moisture safety. The goal of this project is to increase knowledge about how heat recovery systems for residential buildings with respect to defrosting and frost protection measures in heat exchangers. The knowledge can thereafter be used to develop effective defrosting strategies and frost protection measures so that the energy use and power requirements are minimized. Measurements were performed for heat recovery systems placed in dwellings in north Sweden to investigate occurrence of frost formation. The paper will present these measurements and some comparing simulations which can serve as a basis for further development of good defrosting strategies.

Potential for energy recovery from internal combustion engines driving electrical generators in Iraq cities

ABSTRACT Distributed power generation may become an important segment in the energy sector in Iraq. The main objective of this paper is to estimate the potential of heat recovery from the Internal Combustion Engines (ICE) driving electric generators in Iraq. The heat recovery solution considered here is based on Organic Rankine Cycles (ORCs). A model has been developed for an ORC-based system recovering heat from a small/medium size ICE (37.7 kW), which is appropriate for large-scale implementation in Iraq. The model has been validated against results reported in the literature. The main steps of the procedure used to design an ORC-based system are presented, with proper illustrations. They include working fluid selection, performance analysis for each component of the system (evaporator, condenser, and expander) and sizing the main components of the system (evaporator and condenser). The heat recovery efficiency is higher in the North of Iraq and ranges between 8% and 11% in January and between 4% and 7% in July, depending on working fluid and geographical location. R134a provides the highest efficiency, while the second-best working fluid is R1234ze. We adopted the hypothesis that 20% of the power capacity to be installed in Iraq until 2020 is provided by electric generators driven by ICEs of medium power (37 kW). 125000 units should be installed and the investment is about 1.5 billion Euro while heat recovery units may cost about 500 million euro, if manufactured in dedicated factories. Heat recovery may save about 7.5% of the installed power. The government should prepare appropriate policies to stimulate distributed power generation and heat recovery.