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Advancing waste heat potential assessment for net-zero emissions: A review of demand-based thermal energy systems

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  • Oh, Jinwoo
  • Han, Ukmin
  • Jung, Yujun
  • Kang, Yong Tae
  • Lee, Hoseong

Abstract

Amid the global energy and climate crises, research on waste heat recovery has become imperative, with extensive studies focusing on assessing waste heat potential and evaluating recovery technology performance. However, few studies have addressed the crucial relationship between waste heat potential and recovery technology concerning energy demands, essential for efficiently harnessing energy from waste heat sources. In this study, a comprehensive review of the latest research on waste heat potential and recovery technologies is conducted, and an overall roadmap for waste heat utilization is newly presented based on the key findings. The types and temperature ranges of waste heat sources and sinks are redefined based on recent research outputs. In addition, various methods for estimating the waste heat potential and specific considerations for each step are discussed in detail. Waste heat recovery technology is classified into four sections according to the final energy produced: power generation, heating, cooling, and desalination. The working principles and characteristics of each system are described and compared, with each conclusion followed by a thorough investigation regarding efficiency, operating temperature, capacity, capital cost, and technology readiness level. The proposed framework is expected to address knowledge gaps and provide guidelines for constructing a more accurate and useful waste heat potential map that aligns with the energy demands of a region of interest.

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  • Oh, Jinwoo & Han, Ukmin & Jung, Yujun & Kang, Yong Tae & Lee, Hoseong, 2024. "Advancing waste heat potential assessment for net-zero emissions: A review of demand-based thermal energy systems," Renewable and Sustainable Energy Reviews, Elsevier, vol. 202(C).
  • Handle: RePEc:eee:rensus:v:202:y:2024:i:c:s1364032124004192
    DOI: 10.1016/j.rser.2024.114693
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    1. Maki, Seiya & Fujii, Minoru & Fujita, Tsuyoshi & Shiraishi, Yasushi & Ashina, Shuichi & Gomi, Kei & Sun, Lu & Budi Nugroho, Sudarmanto & Nakano, Ryoko & Osawa, Takahiro & Immanuel, Gito & Boer, Rizald, 2022. "A deep reinforced learning spatiotemporal energy demand estimation system using deep learning and electricity demand monitoring data," Applied Energy, Elsevier, vol. 324(C).
    2. Cai, Benan & Long, Chengjun & Du, Qiaochen & Zhang, Wenchao & Hou, Yandong & Wang, Haijun & Cai, Weihua, 2023. "Analysis of a spray flash desalination system driven by low-grade waste heat with different intermittencies," Energy, Elsevier, vol. 277(C).
    3. Shu, Gequn & Wang, Rui & Tian, Hua & Wang, Xuan & Li, Xiaoya & Cai, Jinwen & Xu, Zhiqiang, 2020. "Dynamic performance of the transcritical power cycle using CO2-based binary zeotropic mixtures for truck engine waste heat recovery," Energy, Elsevier, vol. 194(C).
    4. Li, Ligeng & Tian, Hua & Shi, Lingfeng & Zhang, Yonghao & Huang, Guangdai & Zhang, Hongfei & Wang, Xuan & Shu, Gequn, 2022. "Experimental investigation of a splitting CO2 transcritical power cycle in engine waste heat recovery," Energy, Elsevier, vol. 244(PB).
    5. Wu, Wei & Wang, Baolong & Shi, Wenxing & Li, Xianting, 2014. "An overview of ammonia-based absorption chillers and heat pumps," Renewable and Sustainable Energy Reviews, Elsevier, vol. 31(C), pages 681-707.
    6. He, Tianbiao & Lv, Hongyu & Shao, Zixian & Zhang, Jibao & Xing, Xialian & Ma, Huigang, 2020. "Cascade utilization of LNG cold energy by integrating cryogenic energy storage, organic Rankine cycle and direct cooling," Applied Energy, Elsevier, vol. 277(C).
    7. Dai, Baomin & Liu, Xiao & Liu, Shengchun & Wang, Dabiao & Meng, Chenyang & Wang, Qi & Song, Yifan & Zou, Tonghua, 2022. "Life cycle performance evaluation of cascade-heating high temperature heat pump system for waste heat utilization: Energy consumption, emissions and financial analyses," Energy, Elsevier, vol. 261(PB).
    8. Oluleye, Gbemi & Jiang, Ning & Smith, Robin & Jobson, Megan, 2017. "A novel screening framework for waste heat utilization technologies," Energy, Elsevier, vol. 125(C), pages 367-381.
    9. González Grandón, T. & Schwenzer, J. & Steens, T. & Breuing, J., 2024. "Electricity demand forecasting with hybrid classical statistical and machine learning algorithms: Case study of Ukraine," Applied Energy, Elsevier, vol. 355(C).
    10. Forman, Clemens & Muritala, Ibrahim Kolawole & Pardemann, Robert & Meyer, Bernd, 2016. "Estimating the global waste heat potential," Renewable and Sustainable Energy Reviews, Elsevier, vol. 57(C), pages 1568-1579.
    11. Samimi, Mohsen & Moghadam, Hamid, 2024. "Modified evacuated tube collector basin solar still for optimal desalination of reverse osmosis concentrate," Energy, Elsevier, vol. 289(C).
    12. Albert, Max D.A. & Bennett, Katherine O. & Adams, Charlotte A. & Gluyas, Jon G., 2022. "Waste heat mapping: A UK study," Renewable and Sustainable Energy Reviews, Elsevier, vol. 160(C).
    13. Khosravi, A. & Laukkanen, T. & Vuorinen, V. & Syri, S., 2021. "Waste heat recovery from a data centre and 5G smart poles for low-temperature district heating network," Energy, Elsevier, vol. 218(C).
    14. Salemi, Sina & Torabi, Morteza & Haghparast, Arash Kashani, 2022. "Technoeconomical investigation of energy harvesting from MIDREX® process waste heat using Kalina cycle in direct reduction iron process," Energy, Elsevier, vol. 239(PE).
    15. Oh, Jinwoo & Park, Yunjae & Lee, Hoseong, 2022. "Development of a fully deterministic simulation model for organic Rankine cycle operating under off-design conditions," Applied Energy, Elsevier, vol. 307(C).
    16. Pallav Purohit & Nathan Borgford-Parnell & Zbigniew Klimont & Lena Höglund-Isaksson, 2022. "Achieving Paris climate goals calls for increasing ambition of the Kigali Amendment," Nature Climate Change, Nature, vol. 12(4), pages 339-342, April.
    17. González, Daniel & Amigo, José & Suárez, Francisco, 2017. "Membrane distillation: Perspectives for sustainable and improved desalination," Renewable and Sustainable Energy Reviews, Elsevier, vol. 80(C), pages 238-259.
    18. Brückner, Sarah & Liu, Selina & Miró, Laia & Radspieler, Michael & Cabeza, Luisa F. & Lävemann, Eberhard, 2015. "Industrial waste heat recovery technologies: An economic analysis of heat transformation technologies," Applied Energy, Elsevier, vol. 151(C), pages 157-167.
    19. Gao, Yu & He, Guogeng & Chen, Peidong & Zhao, Xin & Cai, Dehua, 2019. "Energy and exergy analysis of an air-cooled waste heat-driven absorption refrigeration cycle using R290/oil as working fluid," Energy, Elsevier, vol. 173(C), pages 820-832.
    20. Morciano, Matteo & Fasano, Matteo & Bergamasco, Luca & Albiero, Alessandro & Lo Curzio, Mario & Asinari, Pietro & Chiavazzo, Eliodoro, 2020. "Sustainable freshwater production using passive membrane distillation and waste heat recovery from portable generator sets," Applied Energy, Elsevier, vol. 258(C).
    21. Pinheiro, Joana M. & Salústio, Sérgio & Rocha, João & Valente, Anabela A. & Silva, Carlos M., 2020. "Adsorption heat pumps for heating applications," Renewable and Sustainable Energy Reviews, Elsevier, vol. 119(C).
    22. Fabian Bühler & Stefan Petrović & Torben Ommen & Fridolin Müller Holm & Henrik Pieper & Brian Elmegaard, 2018. "Identification and Evaluation of Cases for Excess Heat Utilisation Using GIS," Energies, MDPI, vol. 11(4), pages 1-24, March.
    23. Lei Wu & Zhichao Dong & Zheren Cai & Turga Ganapathy & Niocholas X. Fang & Chuxin Li & Cunlong Yu & Yu Zhang & Yanlin Song, 2020. "Highly efficient three-dimensional solar evaporator for high salinity desalination by localized crystallization," Nature Communications, Nature, vol. 11(1), pages 1-12, December.
    24. Yang, Xiaoshan & Yao, Lingye & Peng, Lilliana L.H., 2024. "Impacts of urban air temperature and humidity on building cooling and heating energy demand in 15 cities of eastern China," Energy, Elsevier, vol. 288(C).
    25. Yu, Zeting & Feng, Chunyu & Lai, Yanhua & Xu, Guoping & Wang, Daohan, 2022. "Performance assessment and optimization of two novel cogeneration systems integrating proton exchange membrane fuel cell with organic flash cycle for low temperature geothermal heat recovery," Energy, Elsevier, vol. 243(C).
    26. Zhang, Xinxin & He, Maogang & Zhang, Ying, 2012. "A review of research on the Kalina cycle," Renewable and Sustainable Energy Reviews, Elsevier, vol. 16(7), pages 5309-5318.
    27. He, Fang & Nagano, Katsunori & Togawa, Junya, 2020. "Experimental study and development of a low-cost 1 kW adsorption chiller using composite adsorbent based on natural mesoporous material," Energy, Elsevier, vol. 209(C).
    28. Olabi, A.G. & Elsaid, Khaled & Rabaia, Malek Kamal Hussien & Askalany, Ahmed A. & Abdelkareem, Mohammad Ali, 2020. "Waste heat-driven desalination systems: Perspective," Energy, Elsevier, vol. 209(C).
    29. Hanshik, Chung & Jeong, Hyomin & Jeong, Kwang-Woon & Choi, Soon-Ho, 2016. "Improved productivity of the MSF (multi-stage flashing) desalination plant by increasing the TBT (top brine temperature)," Energy, Elsevier, vol. 107(C), pages 683-692.
    30. Miró, Laia & Brückner, Sarah & Cabeza, Luisa F., 2015. "Mapping and discussing Industrial Waste Heat (IWH) potentials for different countries," Renewable and Sustainable Energy Reviews, Elsevier, vol. 51(C), pages 847-855.
    31. Miró, Laia & Gasia, Jaume & Cabeza, Luisa F., 2016. "Thermal energy storage (TES) for industrial waste heat (IWH) recovery: A review," Applied Energy, Elsevier, vol. 179(C), pages 284-301.
    32. Wang, Dabiao & Dai, Xiaoye & Wu, Zhihua & Zhao, Wu & Wang, Puwei & Hu, Busong & Shi, Lin, 2020. "Design and testing of a 340 kW Organic Rankine Cycle system for Low Pressure Saturated Steam heat source," Energy, Elsevier, vol. 210(C).
    33. Lu, Hongyou & Price, Lynn & Zhang, Qi, 2016. "Capturing the invisible resource: Analysis of waste heat potential in Chinese industry," Applied Energy, Elsevier, vol. 161(C), pages 497-511.
    34. Lin, Yuancheng & Chong, Chin Hao & Ma, Linwei & Li, Zheng & Ni, Weidou, 2022. "Quantification of waste heat potential in China: A top-down Societal Waste Heat Accounting Model," Energy, Elsevier, vol. 261(PB).
    35. Lenan Zhang & Xiangyu Li & Yang Zhong & Arny Leroy & Zhenyuan Xu & Lin Zhao & Evelyn N. Wang, 2022. "Highly efficient and salt rejecting solar evaporation via a wick-free confined water layer," Nature Communications, Nature, vol. 13(1), pages 1-12, December.
    36. Bao, Junjiang & Zhao, Li, 2013. "A review of working fluid and expander selections for organic Rankine cycle," Renewable and Sustainable Energy Reviews, Elsevier, vol. 24(C), pages 325-342.
    37. Brueckner, Sarah & Miró, Laia & Cabeza, Luisa F. & Pehnt, Martin & Laevemann, Eberhard, 2014. "Methods to estimate the industrial waste heat potential of regions – A categorization and literature review," Renewable and Sustainable Energy Reviews, Elsevier, vol. 38(C), pages 164-171.
    38. Grewal, Rahul & Kumar, Mahesh, 2022. "Performance evaluation of a concatenated stepped solar still system loaded with different masses of energy storage material," Energy, Elsevier, vol. 259(C).
    39. Tazi, Nacef & Safaei, Fatemeh & Hnaien, Faicel, 2022. "Assessment of the levelized cost of energy using a stochastic model," Energy, Elsevier, vol. 238(PB).
    40. Yuan, Xiaolei & Liang, Yumin & Hu, Xinyi & Xu, Yizhe & Chen, Yongbao & Kosonen, Risto, 2023. "Waste heat recoveries in data centers: A review," Renewable and Sustainable Energy Reviews, Elsevier, vol. 188(C).
    41. Yusuf, Aminu & Ballikaya, Sedat, 2022. "Electrical, thermomechanical and cost analyses of a low-cost thermoelectric generator," Energy, Elsevier, vol. 241(C).
    42. Meha, Drilon & Novosel, Tomislav & Duić, Neven, 2020. "Bottom-up and top-down heat demand mapping methods for small municipalities, case Gllogoc," Energy, Elsevier, vol. 199(C).
    43. Oh, Jinwoo & Jeong, Hoyoung & Lee, Hoseong, 2021. "Experimental and numerical analysis on low-temperature off-design organic Rankine cycle in perspective of mass conservation," Energy, Elsevier, vol. 234(C).
    44. Alklaibi, A.M. & Lior, N., 2021. "Waste heat utilization from internal combustion engines for power augmentation and refrigeration," Renewable and Sustainable Energy Reviews, Elsevier, vol. 152(C).
    45. Ziemele, Jelena & Dace, Elina, 2022. "An analytical framework for assessing the integration of the waste heat into a district heating system: Case of the city of Riga," Energy, Elsevier, vol. 254(PB).
    46. Doračić, Borna & Pukšec, Tomislav & Schneider, Daniel Rolph & Duić, Neven, 2020. "The effect of different parameters of the excess heat source on the levelized cost of excess heat," Energy, Elsevier, vol. 201(C).
    47. Wu, Di & Hu, Bin & Wang, R.Z., 2021. "Vapor compression heat pumps with pure Low-GWP refrigerants," Renewable and Sustainable Energy Reviews, Elsevier, vol. 138(C).
    48. Luberti, Mauro & Gowans, Robert & Finn, Patrick & Santori, Giulio, 2022. "An estimate of the ultralow waste heat available in the European Union," Energy, Elsevier, vol. 238(PC).
    49. Luo, Ding & Sun, Zeyu & Wang, Ruochen, 2022. "Performance investigation of a thermoelectric generator system applied in automobile exhaust waste heat recovery," Energy, Elsevier, vol. 238(PB).
    50. Calama-González, Carmen María & Symonds, Phil & Petrou, Giorgos & Suárez, Rafael & León-Rodríguez, Ángel Luis, 2021. "Bayesian calibration of building energy models for uncertainty analysis through test cells monitoring," Applied Energy, Elsevier, vol. 282(PA).
    51. Shen, Wei & Chen, Xi & Qiu, Jing & Hayward, Jennifier A & Sayeef, Saad & Osman, Peter & Meng, Ke & Dong, Zhao Yang, 2020. "A comprehensive review of variable renewable energy levelized cost of electricity," Renewable and Sustainable Energy Reviews, Elsevier, vol. 133(C).
    52. Huang, Pei & Copertaro, Benedetta & Zhang, Xingxing & Shen, Jingchun & Löfgren, Isabelle & Rönnelid, Mats & Fahlen, Jan & Andersson, Dan & Svanfeldt, Mikael, 2020. "A review of data centers as prosumers in district energy systems: Renewable energy integration and waste heat reuse for district heating," Applied Energy, Elsevier, vol. 258(C).
    53. Wang, Zhe & Cai, Wenjian & Han, Fenghui & Ji, Yulong & Li, Wenhua & Sundén, Bengt, 2019. "Feasibility study on a novel heat exchanger network for cryogenic liquid regasification with cooling capacity recovery: Theoretical and experimental assessments," Energy, Elsevier, vol. 181(C), pages 771-781.
    54. Colmenar, J.M. & Hidalgo, J.I. & Salcedo-Sanz, S., 2018. "Automatic generation of models for energy demand estimation using Grammatical Evolution," Energy, Elsevier, vol. 164(C), pages 183-193.
    55. Li, Longquan & Liu, Zhiqiang & Deng, Chengwei & Xie, Nan & Ren, Jingzheng & Sun, Yi & Xiao, Zhenyu & Lei, Kun & Yang, Sheng, 2022. "Thermodynamic and exergoeconomic analyses of a vehicular fuel cell power system with waste heat recovery for cabin heating and reactants preheating," Energy, Elsevier, vol. 247(C).
    56. Thombare, D.G. & Verma, S.K., 2008. "Technological development in the Stirling cycle engines," Renewable and Sustainable Energy Reviews, Elsevier, vol. 12(1), pages 1-38, January.
    57. Miró, Laia & Brueckner, Sarah & McKenna, Russell & Cabeza, Luisa F., 2016. "Methodologies to estimate industrial waste heat potential by transferring key figures: A case study for Spain," Applied Energy, Elsevier, vol. 169(C), pages 866-873.
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