Excess Heat Recovery Research Articles

Innovative Fixed-Bed Reactor Integrated with Heat Transfer System for Lean Methane Mixture Removal

A new type of compact, portable fixed-bed reactor integrated with a heat transfer system was developed for the removal of volatile and flammable air pollutants such as lean methane and volatile organic compounds (VOCs). The reactor may operate in catalytic or thermal combustion conditions with the purpose of achieving autothermal processes with the possibility of energy recovery. An excess heat recovery point was designed behind the reactor bed at the place where the gas temperature is the highest to enable its usage. The mathematical model is presented together with a number of simulation calculations performed for the assessment of the developed reactor. The case study in this paper was for catalytic methane oxidation at a temperature of 400 °C, a methane concentration between 0.1% and 2% by weight, a gas flow rate of 1 m3/s STP, and a heat exchange surface for the assumed plate exchanger from 10 to 200 m2. The calculations show that the thickness of the insulation is of little importance for the operation of the equipment, and a sufficient thickness was about 20–50 mm. The optimal area for the considered case is 80–100 m2. It was found that recovery of thermal energy is possible only for higher methane concentrations, above 0.3% by weight. Using an appropriate surface for the exchanger, it is possible to recover even 50% of the combustion enthalpy at a methane concentration of 0.45% by weight. For an exchanger area below 50 m2, the recoverable energy drops rapidly. It was found that the exchanger area is the most important equipment parameter under consideration.

Environmental and economic assessment of industrial excess heat recovery collaborations through 4th generation district heating systems

The external use of excess heat from industrial processes is an important factor in the energy transition and 4th generation district heating is an enabling technology. This paper presents a calculation tool for assessing the economic feasibility and the environmental impact of collaborations between potential industrial sources and users. The tool supports the sizing of district heating pipe diameters, pumps, heat pumps, and heat storage systems. A distinctive feature of the model is the possibility of calculating carbon and blue water footprints, alongside economic indicators, for both existing stand-alone systems and potential collaborative configurations. Excess heat recovery from water-cooled condensers of refrigeration systems is evaluated for two case studies involving the space heating of offices in a food logistics hub and the heating of a greenhouse from a frozen pizza factory, respectively. Only the second collaboration is profitable with the baseline price of natural gas (0.04 €/kWh) and electricity (0.12 €/kWh), provided that the distance between the source and the user is less than 2 km. For higher gas prices, distances of approximately 8 km would be viable. However, for source-user distances above 5 km, the water footprint of the collaboration would be higher than that of stand-alone systems.

Design and 4E Analysis of a Hybrid Air Supply System for Blast Furnaces Driven by Excess Pressure and Waste Heat Recovery

Design and 4E Analysis of a Hybrid Air Supply System for Blast Furnaces Driven by Excess Pressure and Waste Heat Recovery

Stakeholder interfaces for excess heat-based urban heat supply— Input from Swedish cases

Excess heat is generated from different industrial processes and from urban infrastructure (sewage water, transport, datacentres and buildings). Thirty-five percent of the European energy demand for heating and cooling could be met by excess heat. Today, however, this energy reserve is barely exploited. There are known barriers to excess heat recovery but limited information on stakeholder interactions in the early stages of excess heat collaborations and on successful collaborations. Sweden is world champion in terms of excess heat recovery into district heating systems, and the country has a long tradition in this field (dating back to the 1970 s). By studying two cases, we shed light on success factors in the early stages and in successful collaborations. We identify that the main success factors for excess heat recovery are (i) trust between the collaborating partners, (ii) the involvement of as many stakeholders across the DH (District Heating) value chain as possible (in the decision-making process), (iii) the establishment of joint goals, and (iv) the identification of a business model allowing for a win-win solution that prioritizes excess heat recovery and secures funding for the necessary investments. Excess heat recovery investments have features similar to those of other investments in climate change mitigation, making the success factors relevant to applications beyond the case of excess heat recovery.

Greater Energy Independence with Sustainable Steel Production

Global energy market price volatility and an upward trajectory of prices per unit of electricity have sent all industrial sectors and many economies to the brink of recession. Alongside the urgent need for decarbonisation of all industries, achieving a globally higher level of energy independence across all sectors seems imperative. A multi-disciplinary approach with a proposed system of CO2 emissions reduction and capture technologies has the potential for short-term emissions reduction to near-zero in the steel industry—although some of the mechanisms can be implemented across most heavy industries. The findings of this research show a CO2 emissions reduction of ~30% from 977 t of CO2 to 684 t in one single blast furnace production cycle (based on 330 tonnes of liquid iron production capacity, with the mean of 2.1–3.2 tonnes CO2/t of steel and chemical reactions emissions applied), by switching the electricity provider for operating the electric heaters to providers generating energy exclusively from renewable sources. Replacing coal with biomass and adding post-combustion capture units to the blast furnace operation, will add carbon neutrality into the process—resulting in CO2 emissions reduction to near-zero. Carbon capture from biomass utilisation (BECCS) will add the benefit of carbon-negative emissions to the cycle. Simultaneously, energy-saving and process improvement measures implementation (up to 60% efficiency increase), excess heat recovery <30% of energy savings, and retrofitting renewable energy technology resulted in an energy independence of 88%. Engineering solutions, partly subsidised in the UK, are readily available for implementation in the iron and steel manufacturing industry.

Exploring the location and use of baseload district heating supply. What can current heat sources tell us about future opportunities?

The decentralization of energy production and recovery of excess heat (EH) to reach climate targets is essential for renewable and fully decarbonized heating systems. This paper identifies current and potential industrial EH sources providing baseload capacity for district heating (DH) systems. These sources are evaluated by sector and process for supplying baseload capacities explored for current 3rd generation district heating (3GDH) and 4th generation district heating (4GDH) systems with lower grid temperatures and losses, with and without expansions. The method combines geographical analysis and available baseload capacity estimations for 360 Danish DH systems scenario-making and an additional sensitivity analysis evaluating baseload capacity full-load hours. It is found that 80 % of Danish DH systems have an unmet baseload capacity of 50 % or higher. Half of the systems have geothermal capacity available and up to 20 % of industrial EH baseload capacity potential, which sums up to 5 PJ of EH potential within a 2 km distance. The findings also suggest that there is an additional opportunity for the placement of future energy infrastructure able to supply EH, which is highly contextual and strategic in heat planning, particularly considering the future development of sustainable and energy-efficient DH systems.

Techno-economic optimization of the industrial excess heat recovery for an industrial park with high spatial and temporal resolution

With increasing heating and cooling demands, decarbonisation of the heating and cooling sectors is key to achieving a carbon–neutral energy system. Using industrial excess heat in heating systems helps offset emissions by reducing the use of fossil fuels. While several studies have analysed the temperature of heat availability, the cost of extending or constructing the heating network and techno-economic feasibility, it is important to consider all aspects together to achieve a comprehensive design of industrial excess heat recovery. This study proposes a method to link an energy system optimisation tool with a spatial analysis tool and an exergy analysis tool to achieve a comprehensive design. An iterative soft link is implemented between the energy system model and the spatial analysis tool for high spatial and temporal resolution. The developed method is applied to a case study of an industrial park in Greece. Scenarios are developed to assess the robustness of the developed method and the system profitability of excess heat recovery. The scenarios indicated that the profitability of excess heat depends heavily on the price of natural gas with the share of excess heat increasing from 10% to 45% with a 20% increase in natural gas prices in cases where heat pumps are needed for temperature boosting. In cases where heat pumps are not needed, excess heat indicates higher system profitability with a share of around 40% and reduces the emissions by around 50 times. The method provides robust results in considered scenarios with convergence within four iterations.

Techno-economic evaluation of solar-driven ceria thermochemical water-splitting for hydrogen production in a fluidized bed reactor

Thermochemical water splitting (TCWS) is an attractive and promising approach for hydrogen fuel production to replace fossil fuels and address climate change. The novel approach used in this study is the indirect irradiation of the ceria particle with solar-heated nitrogen in a fluidized bed reactor which improved the ceria thermo-reduction and increased hydrogen yield. The TCWS plant featured additional units for oxygen co-production, and excess heat recovery to generate electricity and reduce the saleable hydrogen price. Two fluidized bed reactors for ceria thermo-reduction and oxidation using steam were modelled in Aspen Plus for hydrogen production at a 70% capacity factor. A photovoltaic (PV)-battery module in addition to the solar parabolic dish collector (PDC) was then used to deliver operation-round electricity supply and drive mechanical and control systems, reducing overall plant energy cost. Three minimum selling prices of hydrogen were considered based on the achievable products of the TCWS plant: (i) pricing based on no co-products, (ii) pricing including oxygen revenue, and (iii) pricing including oxygen and electricity revenue. The TCWS plant achieved a minimum selling price (MSP) of 3.92 USD/kg H2 (including oxygen and electricity revenue) at a 10% discount rate which is the lowest for solar-driven TCWS hydrogen compared with other similar studies. Sensitivity analyses showed that discount rate, steam Rankine cycle, power block, cost of ceria and hydrogen storage, and price of oxygen, respectively, had the highest impact on the MSP of the TCWS hydrogen plant. The switch value analysis (SVA) was used to determine the potential of achieving the global target hydrogen price of 2 USD/kg based on a single parameter assessment. The TCWS plant proposed in this work provides a promising approach toward achieving future hydrogen prices below 2 USD/kg when a lower discount rate of 5% is utilised. It was established that the choice and size of concentrated solar power (CSP) technology integration, co-generation, and heat recovery are critical to the system efficiency and economic viability of a solar-driven TCWS hydrogen production. This work demonstrated the use of ceria as a metal oxide feed suitable for solar TCWS hydrogen production with a promising economic potential for a global target price of less than 2 USD/kg H2 based on the choice of process-CSP configuration.

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

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

Risk assessment of industrial excess heat collaborations – Empirical data from new and ongoing installations

Excess heat could meet approximately 25% of the heat demand in the European building sector. However, the recovery of excess heat is low, which has been attributed to financial, technical and organisational barriers. There is limited information on the perceived risk exposure of excess heat recovery at different points in time, before undertaking the investment or after having undertaken the investment, and at locations with existing district heating networks or not (greenfield). This is unfortunate because experience can enable new collaborations. In this paper, we compare the perceived risk exposure of four greenfield and two ongoing industrial excess heat recovery collaborations. In doing so, we confirm previously identified barriers, such as difficulty to agree on the value of excess heat, the risk of a single heat source and lack of regulation. We also find that, with experience, changes to the excess heat-generating processes are increasingly important, whereas, greenfield sites find the lack of ‘know-how’ to be risky. However, the main conclusion from this paper is that the risks of industrial excess heat recovery collaborations appear to be over-emphasised. In fact, risk exposure of industrial activity can be reduced through industrial waste heat recovery as excess heat is characterized by limited price fluctuations and new environmental requirements from customers and authorities can be met proactively. Combining experience with a standardised excess heat recovery policy should significantly reduce the risk exposure of new collaborations.

Impact of recent district heating developments and low-temperature excess heat integration on design of industrial energy systems: An integrated assessment method

One of today’s biggest challenges is taking effective measures to mitigate negative effects and consequences of human-made climate change such as sector coupling and excess heat valorization. In this work, sector coupling of residential and industrial heat supply are considered in an optimization-based design and operation evaluation for industrial energy supply systems with the aim of minimizing costs and determining the impact of on-going developments and progresses in district heating systems. The developed method is applied to a use case with a superstructure for the industrial energy system including a biomass-fired steam generation unit, two heat pumps and various thermal storages, generic industrial load profiles for steam, hot water and excess heat and simulation-based district heating load profiles. The most relevant results reveal that depending on the district heating setting total annual costs, including fuel costs and annualized investments, increase between 2 and 39% compared to no additional district heating supply by the industrial energy supply system. However, the lowest cost increase does not coincide with the lowest additional energy amount. Thus, synergies such as corresponding temperature levels between energy supply for all domains have been identified as crucial criteria for economic success. Also, unit integration for excess heat recovery occurs always combined with thermal storages adapting the temporal occurrence of excess heat. Results for the evaluated use case highlight the importance and relevance of combined considerations for sector coupling measures. Thus, methods, as presented in this work, can contribute crucial information for future assessments. However, further development of the model, e.g. a larger set of generation technologies, and further use cases with other temperature levels, demand profiles are identified as relevant next steps.

A techno-economic evaluation of low-grade excess heat recovery and liquid desiccant-based temperature and humidity control in automotive paint shops

The paint shop is the most energy-intensive process in an automotive manufacturing plant, with air management systems that supply air to paint booths consuming the most energy. These systems are crucial for temperature and humidity control, in which they ensure the quality of the final product by preventing paint defects and thus avoid the additional cost of reworking. This is especially true for water-based paints, in which evaporation and film formation processes are influenced by the temperature and humidity of the surrounding air. This study aims to investigate the incorporation of liquid desiccant technology into a conventional air management system for paint shops operating in different climates, which presents the novelty of the study. The technology is promising because it can regulate humidity, act as a dehumidifier or humidifier depending on the demand and stores energy in a thermo-chemical form. In addition, waste heat sources available in the paint shop can be used for the regeneration of the liquid desiccant solution. The techno-economic evaluation of this novel process indicates that the proposed system can control the temperature and humidity of the supply air within the range required for optimal painting and achieve significant energy savings in both cold and hot/humid climates, with a reduction of 44.4% and 33.6% of the energy cost compared to the conventional operation and a payback period of 6.15 and 5.74 years respectively, using calcium chloride as the desiccant solution. The sensitivity analysis investigates the effect of the energy and carbon price on the performance of the system. It is concluded that the integration of liquid desiccant technology into conventional air management systems for paint booths has a huge potential to increase the energy-efficiency of automotive painting.

Liberalized market designs for district heating networks under the EMB3Rs platform

Current developments in heat pumps, supported by innovative business models, are driving several industry sectors to take a proactive role in future district heating and cooling networks in cities. For instance, supermarkets and data centers have been assessing the reuse of waste heat as an extra source for the district heating network, which would offset the additional investment in heat pumps. This innovative business model requires complete deregulation of the district heating market to allow industrial heat producers to provide waste heat as an additional source in the district heating network. This work proposes the application of innovative market designs for district heating networks, inspired by new practices seen in the electricity sector. More precisely, pool and Peer-to-Peer (P2P) market designs are addressed, comparing centralized and decentralized market proposals. An illustrative case of a Nordic district heating network is used to assess the performance of each market design, as well as the potential revenue that different heat producers can obtain by participating in the market. An important conclusion of this work is that the proposed market designs are in line with the new trends, encouraging the inclusion of new excess heat recovery players in district heating networks. • Development of pool-based, P2P and community-based market designs for DHN application. • Consumer preferences in heat trade — CO2 emissions, heat losses and network distance. • Competitive environment for multiple sources of waste heat recovery in DHNs. • Assessment and validation of market models within the EMB3Rs platform. • Analysis of DHN market participants considering economic and fairness indicators.

Optimal cost management of the CCHP based data center with district heating and district cooling integration in the presence of different energy tariffs

Data centers are expected to be one of the major prosumers in energy networks because of their high electricity demands as well as being a possible source of waste heat energy utilization. A combined cooling, heat, and power (CCHP) system can be a perfect match with a data center for supplying the data center's less fluctuated, uninterrupted power and cooling demand. Moreover, CCHP based data center integration with regional district heating and cooling system can gain data center's excess heat, improve the efficiency of the primary energy sources, and give flexibility to district energy operators. This paper aims to offer a comprehensive energy cost management for a CCHP based data center that considers power, heating, cooling, and data center's excess heat utilization in the presence of hourly energy prices and varying outdoor temperatures. Mixed Integer Linear Programming (MILP) is used to determine a cost-optimized operational strategy for the overall system. The result shows that CCHP and regional energy integration to the data center decrease the overall energy cost of the operation while providing more flexibility to the data center and district energy network operators. Optimized operation of the CCHP system with the data center's excess heat recovery, district heating, and cooling integration can cut its annual electricity costs by 40.3% compared to the local operation of the CCHP based data center. Return of investment (ROI) is estimated to be in 6.6 years for additional required systems for the conventional data center.

Analysis of Longitudinal Finned Pipes in Cross-Flow Heat Exchanger

In this case, the recovery of excess heat in the steel-making process becomes challenging to save energy effectively and efficiently. One way to help the process of heat recovery in the steel-making process is with a heat exchanger. This heat exchanger maximizes the production process work. However, in the application, the heat exchanger developed to date can still work optimally. Based on the literature study that has been done previously for the design of the heat exchanger, in this study, the addition of four longitudinal fins variations with the cross-flow flow was carried out. This research compares the heat exchanger performance finned pipes with pipes without fins design, where liquid and airflow rates are varied. This study evaluated whether the longitudinal fins configuration and the fluid flow rate affect the cross-flow heat exchanger performance. The results show that fins addition on the copper pipes increases the value of Nusselt number 2.56% in liquid fluid and 16.57% in air fluid and increases the NTU value of its effectiveness by 24.77%.

Electricity Generation from Low and Medium Temperature Industrial Excess Heat in the Kraft Pulp and Paper Industry

The recovery and utilisation of industrial excess heat has been identified as an important contribution for energy efficiency by reducing primary energy demand. Previous works, based on top-down studies for a few sectors, or regional case studies estimated the overall availability of industrial excess heat. A more detailed analysis is required to allow the estimation of potentials for specific heat recovery technologies, particularly regarding excess heat temperature profiles. This work combines process integration methods and regression analysis to obtain cogeneration targets, detailed excess heat temperature profiles and estimations of electricity generation potentials from low and medium temperature excess heat. The work is based on the use of excess heat temperature (XHT) signatures for individual sites and regression analysis using publicly available data, obtaining estimations of the technical potential for electricity generation from low and medium temperature excess heat (60–140 °C) for the whole Swedish kraft pulp and paper industry. The results show a technical potential to increase the electricity production at kraft mills in Sweden by 10 to 13%, depending on the level of process integration considered, and a lower availability of excess heat than previously estimated in studies for the sector. The approach used could be adapted and applied in other sectors and regions, increasing the level of detail at which industrial excess heat estimations are obtained when compared to previous studies.

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.

Liberalized market designs for district heatingnetworks under the EMB3Rs platform

Current developments in heat pumps, supported by innovative business models, are driving several industry sectors to take a proactive role in future district heating and cooling networks in cities. For instance, supermarkets and data centers have been assessing the reuse of waste heat as an extra source for the district heating network, which would offset the additional investment in heat pumps. This innovative business model requires complete deregulation of the district heating market to allow industrial heat producers to provide waste heat as an additional source in the district heating network. This work proposes the application of innovative market designs for district heating networks, inspired by new practices seen in the electricity sector. More precisely, pool and market designs are addressed, comparing centralized and decentralized market proposals. An illustrative case of a Nordic district heating network is used to assess the performance of each market design, as well as the potential revenue that different heat producers can obtain by participating in the market. An important conclusion of this work is that the proposed market designs are in line with the new trends, encouraging the inclusion of new excess heat recovery players in district heating networks.

Double Loop Network for Combined Heating and Cooling in Low Heat Density Areas

This study investigated a double loop network operated with ultra-low supply/return temperatures of 45/25 °C as a novel solution for low heat-density areas in Denmark and compared the proposed concept with a typical tree network and with individual heat pumps to each end-users rather than district networks. It is a pump-driven system, where the separate circulation of supply and return flow increased the flexibility of the system to integrate and displace heating and cooling energy along the network. Despite the increased use of central and local water pumps to operate and control the system, the simulated overall pump energy consumption was 0.9% of the total energy consumption. This was also an advantage at the design stage as the larger pressure gradient, up to 570 Pa/m, allowed minimal pipe diameters. In addition, the authors proposed the installation of electrically heated vacuum-insulated micro tanks of 10 L on the primary side of each building substation as a supplementary heating solution to meet the comfort and hygiene requirements for domestic hot water (DHW). This, combined with supply water circulation in the loop network, served as a technical solution to remove the need for bypass valves during summer periods with no load in the network. The proposed double loop system reduced distribution heat losses from 19% to 12% of the total energy consumption and decreased average return temperatures from 33 °C to 23 °C compared to the tree network. While excess heat recovery can be limited due to hydraulic issues in tree networks, the study investigated the double loop concept for scenarios with heat source temperatures of 30 °C and 45 °C. The double loop network was cost-competitive when considering the required capital and operating costs. Furthermore, district networks outperformed individual heat pump solutions for low-heat density areas when waste heat was available locally. Finally, although few in Denmark envisage residential cooling as a priority, this study investigated the potential of embedding heating and cooling in the same infrastructure. It found that the return line could deliver cold water to the end-users and that the maximum cooling power was 1.4 kW to each end-user, which corresponded to 47% of the total peak heat demand used to dimension the double loop network.

The role of data centres in the future Danish energy system

Data centres (DCs) are expected to satisfy the rising demand for internet services. Denmark alone is expected to host several large-scale DCs, whose demand for electricity in 2040 may reach 33% of 2017 national electricity consumption. Understanding the operation and interactions of DCs with energy systems is key to understanding their impacts on installed capacities, costs and emissions. The present paper makes three contributions in this regard. First, we introduce a thermodynamic model that relates the power consumption of DCs to their production of excess heat (EH). Second, the results are scaled up to represent DCs in a national energy-system model for the analysis of different scenarios. Third, scenarios are generated and analysed to quantify the impact of DCs on the Danish energy system until 2050. The results show that DCs might have significant impacts on Denmark’s power and district heating (DH) sectors. First, the power demand from DCs translates into an additional 3–6 GW of offshore wind capacity. Second, EH from DCs is beneficial to the whole energy system, the entire quantity of EH being utilized in four out of five scenarios. EH recovery from DCs is economically beneficial, providing from 4% to 27% of Denmark’s DH after 2040.