DeCarbCH Wiki Technologies - Heat Pumps
Absorbtion Heat Pump
Heat pump is a group of technologies which is able to move heat from one source to a sink where sink and source have different temperature. Heat pump can be categorized into different way they work: Magnetic refrigeration, Stirling engine, Thermoacoustic heat engine, Thermoelectric cooling, Absorption heat pump, Vapor-compression cycle.
Principle of operation
Absorption heat pumps use thermal energy instead of mechanical energy for heat upgrade. They employ fluid mixtures with large differences in vapour pressures. A cyclical process of absorption (exothermic) and desorption (endothermic) is employed to make use of available heat to deliver heat at the temperature of interest. Different pairs of fluids used for the process such as, Ammonia (solute) and water (solvent) or water (solute) and Lithium-Bromide (solvent). The electrical power needed for pumps is very small compared to the heat transfer rates. There are two types of Absorption heat pumps.
In this case, heat is supplied from a high temperature source, e.g., by firing natural gas. Although, concepts employing solar thermal or geothermal heat source exist. The heat is mainly used for desorption process in the cycle. The cyclical process lifts the heat from a lower temperature and the total heat is then delivered at an intermediate temperature. This type of heat pump is typically used a chiller in industry. Typically, the coefficient of performance, that is the ratio of useful heat delivered to the heat input is about 1.7.
The cyclical process is reversed compared to type 1. This type of heat pump takes heat at an intermediate temperature and delivers a fraction (typical value of 0.48)of the heat to a higher temperature, while at the same time giving out the remaining fraction at a lower temperature. Thus, a fraction of waste heat can be upgraded to a higher temperature. This type of heat pump is also referred to as absorption heat transformer. Temperature upgrades up to 165°C have been reported in the literature. An online tool is available online (this tool was not made neither controlled by any of the DeCarbCH experts).
Advantages: low electricity consumption, longer life expectancy and lower operating costs.
Challenges: larger space requirements, higher investment costs, and long response times to dynamic loads.
Absorption heat pumps are mainly used in chemical industry a comprehensive [2]. In Switzerland, a ammonia-water absorption heat pump is announced to be employed in the district heating system in Basel. It uses Geomethermal energy as a heat source. The absorption heat pump has a Capacity of 30MW.
[1]: Case studies & references, cnim industrial systems, absorption heat pumps for district heating, 2019.
Note: for Basel heat pump, we need to verify that it is indeed absorption heat pump and not an heat pump employing ammonia as working fluid. [2]: CUDOK, Falk, et al. Absorption heat transformer-state-of-the-art of industrial applications. Renewable and Sustainable Energy Reviews, 2021, 141. Jg., S. 110757
Type 1
In this case, heat is supplied from a high temperature source, e.g., by firing natural gas. Although, concepts employing solar thermal or geothermal heat source exist. The heat is mainly used for desorption process in the cycle. The cyclical process lifts the heat from a lower temperature and the total heat is then delivered at an intermediate temperature. This type of heat pump is typically used a chiller in industry. Typically, the coefficient of performance, that is the ratio of useful heat delivered to the heat input is about 1.7.
Type 2
The cyclical process is reversed compared to type 1. This type of heat pump takes heat at an intermediate temperature and delivers a fraction (typical value of 0.48)of the heat to a higher temperature, while at the same time giving out the remaining fraction at a lower temperature. Thus, a fraction of waste heat can be upgraded to a higher temperature. This type of heat pump is also referred to as absorption heat transformer. Temperature upgrades up to 165°C have been reported in the literature. An online tool is available online (this tool was not made neither controlled by any of the DeCarbCH experts).
Pros and Cons
Advantages: low electricity consumption, longer life expectancy and lower operating costs.
Challenges: larger space requirements, higher investment costs, and long response times to dynamic loads.
Examples
Absorption heat pumps are mainly used in chemical industry a comprehensive [2]. In Switzerland, a ammonia-water absorption heat pump is announced to be employed in the district heating system in Basel. It uses Geomethermal energy as a heat source. The absorption heat pump has a Capacity of 30MW.
References
[1]: Case studies & references, cnim industrial systems, absorption heat pumps for district heating, 2019.
Note: for Basel heat pump, we need to verify that it is indeed absorption heat pump and not an heat pump employing ammonia as working fluid. [2]: CUDOK, Falk, et al. Absorption heat transformer-state-of-the-art of industrial applications. Renewable and Sustainable Energy Reviews, 2021, 141. Jg., S. 110757
Experts
DeCarbCH experts on this subject: OST-IES
Other Swiss experts: Swiss Admin Page, ETHZ-epse, HEIG-VD-IE