# A Review of Worldwide Strategies for Promoting High-Temperature Heat Pumps
## 2 The Decarbonization of the Industrial Sector
### Low-to-Medium-Temperature Heat Processes  
Numerous industrial sub-sectors depend heavily on processes that require heat and direct combustion. The demand for heat within the industry is highly diverse, characterized by a wide range of temperature requirements and varied applications. This diversity stems from the different needs across sub-sectors, whether it is for simple heat exchange or for more intensive processes that require direct combustion. For instance, the temperature requirements can vary significantly--from lower temperatures needed for processes like food processing to extremely high temperatures exceeding 1400 \({}^{\circ}\)C necessary for steelmaking and cement production. That is, industrial operating temperatures are dictated by different industrial processes, and they can be generally classified as follows [50]:  
- Ultra-low (<100 \({}^{\circ}\)C);  
- Low (<200 \({}^{\circ}\)C);  
- Medium (200-500 \({}^{\circ}\)C);  
- High (>500 \({}^{\circ}\)C). This manuscript focuses on the demand for low-to-medium-temperature heat, a significant portion of the overall energy requirement in the industrial sector, where HTHPs can be suitable. On average, this category accounts for approximately 44% of the final energy consumption dedicated to industry [51]. Notably, about 80% of this low-to-medium-temperature heat demand is concentrated within G-20 countries [50]. For instance, in the EU, a study estimated the total heat demand for industrial processes and space heating in the EU28+3 to be 2315.6 TWh. Approximately 39% of this demand, or 759.3 TWh, is attributed to process heat requirements up to 200 \({}^{\circ}\)C [29]. In China, the use of low-to-medium-temperature heat is widespread in light industries. These sectors represent over a third of China's industrial heat consumption but account for more than three-quarters of heat consumption below 200 \({}^{\circ}\)C. The potential for HPs to meet this demand is significant, with estimates suggesting a capacity of 175-280 GW, sufficient to cover about 15% of the current heat demand in these industries [45]. In Australia, around 48% of process heat is utilized at temperatures below 250 \({}^{\circ}\)C. This indicates a substantial opportunity for low-temperature heat to play a crucial role in reducing industrial energy consumption and emissions [52]. In the USA, almost 45% of the total industrial heat demand required by processes is under 200 \({}^{\circ}\)C [41]. However, assessing the potential use of HTHPs in some regions is challenging due to a lack of detailed data on the thermal ranges of industrial processes. For instance, comprehensive global data on low-to-medium-temperature heat demand for the Indian industry are not readily available in the literature. While specific data for certain sub-sectors, such as paper mills, do exist, there is a general gap in information for broader industrial applications [53,54]. A similar lack of data was also identified for Canada, Russia, Brazil, and Japan, which are among the largest global emitters. This data gap poses a significant barrier to the adoption of HTHPs, as their implementation requires a thorough understanding of an industry's thermal demand, both in terms of the power and temperature range. To address this issue, this paper provides an estimated range of heat demand for low-to-medium-temperature industrial processes in countries where such data are not readily available in the literature. We base these estimates on the premise that approximately 50-70% of a country's total industrial energy consumption is dedicated to process heat [46]. Figure 4 illustrates the demand for low-temperature industrial heat in some of the world's major emitters. In cases where direct data were not available in the literature, an estimated value was determined based on the available information, to offer insight into the potential significance of this thermal range within industrial energy consumption. It stands out that, at least from a theoretical point of view, HTHPs have a huge potential all over the world.