# A Review of Worldwide Strategies for Promoting High-Temperature Heat Pumps
## 1 Introduction
### State of Art  
High-temperature heat pumps (HTHPs) and large-scale heat pumps (HPs) are gaining traction in industrial process heating and district heating applications, and as a critical component in incorporating RESs into the electricity supply system. As a consequence, many studies focus on the integration of these devices in industrial processes, as well as their effect on the electricity grid and the possibilities to upgrade waste heat. [PERSON] et al. highlighted that HPs are crucial for integrating RESs into the grid, significantly enhancing wind power adoption by reducing grid electricity needs by up to 95%, mitigating feed-in-peaks, and improving self-consumption of PV electricity by 30-65% through real-time adjustments and variable speed technology [23]. Similarly, the study carried out by [PERSON] et al. emphasizes that HPs improve wind power generation and introduction to the grid [24]. The advantages of integrating a DC HP in an AC-DC distribution network have been reported by [PERSON] et al., highlighting that this approach, which connects PVs, batteries, and DC loads in a historical building in Cyprus, achieved over 85% RES usage and notably reduced imported energy [25]. On the other hand, [PERSON] et al. investigate the operational strategy of a DC inverter HP system in an office building equipped with a PV power system, analyzing PV power fluctuations and demand-side load characteristics [26]. The study carried out by [PERSON] et al. explores different HP configurations, covering aspects such as design, operation, recent advancements, and application potentials, to provide comprehensive insights into HP technology [27]. Similarly, [PERSON] et al. present a study on HTHPs, where they reviewed the market and application potentials in detail, providing a first classification of HTHPs [28], while [PERSON] et al. focus on the analysis of the EU HTHPs' potential market, with special attention given to the food and beverage, chemical, and refining sectors [29]. [PERSON] et al. consolidated the data about HTHPs available in the literature; providing a review on recent advances in the technology [30]. In the study conducted by [PERSON] et al., a new methodology for designing and sizing industrial HPs (IHPs) using annual process data is introduced, considering the time average model, the pinch analysis, and thermo-economic optimization [31]. [PERSON] et al. review the approaches of the IHP system in smart grids, highlighting their strengths and potential for energy flexibility [32]. [PERSON] et al. address the inefficiencies of the current waste-heat recovery methods in industrial parks with multiple heat sources and loads by developing an HP-centric network system and a two-stage optimization model for waste-heat utilization. The approach combines waste heat with HP combinations and users, showing a significant decrease in the energy consumption [33]. Figure 3: Global GHG emissions split by pollutants and by sectors. Self-elaboration based on [4; 5]. [PERSON] et al. state that HTHPs are a key technology in the decarbonization of industry, thus not neglecting to discuss the barriers that hinder the deployment of IHPs in this sector [34]. [PERSON] et al. examine the role of industry electrification within various 100% RES system scenarios, concluding that direct electrification of industrial process heat is generally preferable [35]. [PERSON] et al. dedicate their attention specifically to the importance of electrifying the energy-intensive basic materials industry [36]. As the main potential for IHPs is represented by their application in industrial sub-sectors where the majority of processes require low-to-medium temperature heat, many studies around the world focus on the analysis of the HP technologies in those sub-sectors, like the food and beverage, pulp and paper, and chemicals sub-sectors. For instance, [PERSON] et al.