Heating is currently one of the major sources of greenhouse gas (GHG) emissions, accounting for 25% in the UK alone. In China, heating is mainly provided by coal-fired boilers, which not only act as major energy users, but are also responsible for GHG emissions and air pollution.
Research into the decarbonisation of this sector has, therefore, significantly increased in recent years and the role of heat pump technologies to reduce carbon dioxide (CO2) greenhouse gas emissions arising from industrial process heating has become an increasing focus.
Heat pumps are commonly used for domestic space heating and are making inroads into district heating. They use ambient air, soil, a local lake, or sea as a heat sink and produce heat at about 50°C, which is ideal for heating buildings. High temperature industrial heat pumps (HTIHPs) are based on a similar operating principle and have been recognised for their potential to generate steam for process heating in the food, paper, metal, and chemical sectors. Heat pumps are commonly considered as HTIHPs when operating with supply temperatures above 100°C. Some of the main challenges that HTIHPs face are their integrability into these process industries and their ability to match the available heat source to the required heat demand.
To generate steam, an HTIHP requires a heat sink at a temperature of 60-120°C, which is widely available as waste heat from many processes. The heating capacities of current HTIHPs range from 20 kW to 20 MW. A coefficient of performance (COP) of up to 5.8 can be achieved at a 30°C temperature lift. A lower COP between the range 2.2 to 2.8 occurs when a 70°C lift is produced from a heat sink temperature of 120°C.
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