# A Review of Worldwide Strategies for Promoting High-Temperature Heat Pumps
## 3 Heat Pumps: Technological Principles, Challenges, and Potential
### Strengths and Barriers  
IHPs offer several advantages to the industrial sector, such as a long annual operating time, maximizing their utility and return on investment. Additionally, they are designed as large units with a small distance between the heat source and the heat sink, which reduces thermal losses. IHPs are also highly efficient because the production of waste heat and the demand for heat often occur simultaneously, ensuring that the heat generated is immediately utilized, further enhancing their operational efficiency [62]. Due to their efficiency, IHPs can help in reducing the energy CP demand associated with many industrial processes. For example, in the USA food industry, studies estimate potential energy savings of 280 PJ per year in 2021 and around 325 PJ per year by 2050 from electrifying processes like meat processing, beer production, vegetable and fruit caning, and cane sugar refining. The heat demand for vegetable and fruit caning can be entirely met by IHPs. Moreover, HPs are an excellent technology for providing flexibility to the power system while delivering efficient heating and cooling solutions. The installation is generally easy, and they require minimal maintenance while guaranteeing high safety standards [27]. However, transitioning to HP technologies is not straightforward. Several factors can discourage or complicate the adoption of this technology. High upfront capital costs and long payback periods--typically four to five years or more--pose significant barriers to the adoption of HTHPs [34,64]. For example, replacing a 2 MW steam boiler with a 2 MW HP could cost five to eight times more than installing a new boiler, with a payback period likely exceeding five years. However, it is also important to note that an HP of 500 kW or smaller may be sufficient when replacing a steam system, potentially lowering both the initial investment and payback time [65]. Furthermore, the viability of an electric solution hinges on the relative prices of electricity versus the fuel it would replace, along with any necessary changes to the electricity infrastructure to increase supply. Currently, the electricity-to-fuel cost ratio remains too high, necessitating efforts to enhance the competitiveness of HP technologies [62]. A crucial element to take into account is the need to redesign the industrial processes in order to adapt the heat generation and its distribution to the processes in a new way that enables the integration of P2H technologies as well as the enhancement of the recuperation of industrial waste heat. Therefore, assessing the available excess heat resources is essential for effectively integrating IHPs into a process. However, the quantity and quality of excess heat in an industrial plant are highly dependent on the specific site. The degree of process heat integration is influenced by a variety of techno-economic factors unique to each plant, such as the volume and temperature of excess heat and its alternative uses, plant complexity, space limitations, energy costs, and external agreements. Due to these unique site-specific factors, creating generalized composite curves for an industrial process and estimating pinch temperatures from these curves involve a high degree of uncertainty. Consequently, the IHP integration design based on generalized data may not be optimal for every individual plant, creating challenges because the commonly available data are typically generalized [37,66,67]. In addition to the importance of integrating sensors and systems to collect as much data as possible at a local level, it is important to generate knowledge about the industrial processes and IHP technology integration. To effectively raise awareness of the available options and to make informed selections among them, a high level of expertise in system design, process integration, and planning is essential. Design software for process integration and system design is crucial at this stage [62].