Gas sorption heat pump (GAHP)

There are two main types of sorption heat pumps: absorption and adsorption heat pumps. The first one is the most widespread and mature technology within TDHP on the market.

Absorption heat pump

Gas absorption heat pump technology is introduced over 20 years ago and currently available in different sizes and with different types of renewable energy supply (aerothermal, geothermal and hydrothermal).

Adsorption heat pump

Cooll has developed an adsorption heat pump. You can read all about this patented technology on this page.

Adsorption heat pump

Adsorption heat pumps can, for example, use water or ammonia as a refrigerant. Transfer of ambient energy to the system is achieved by evaporating the refrigerant. The refrigerant (water or ammonia) vapor is adsorbed at the surface of a solid (e.g., zeolite or activated carbon). This process releases heat at a higher temperature level. Once the adsorbent is saturated, the refrigerant is expelled in a desorption phase using heat from a fuel burner. Whereas absorption functions continuously, adsorption technology is a cyclic process (adsorption/desorption), which appears to be continuous due to the response time of the heating circuit and respective heat pump design (e.g. more than one adsorption module) and control.

A gas burner keeps a heater containing process water on the right temperature (about 180°C, with the pressurized process water remaining in the liquid phase). This hot water heats in turns two elongated beds filled with adsorption material. This results in a thermal wave moving in about five minutes from one end to the other end of the beds, heating it to 180°C from one end to the other end.

The adsorption material contains adsorbed refrigerant, e.g., ammonia. By heating the bed with the thermal wave, the refrigerant gas desorbs at high pressure from the adsorption material and feeds the heat pump cycle. At the same time the second bed is being cooled by the process water (green circuit) employing a similar thermal wave, giving off the heat via the sorption heat exchanger to the central heating water, for instance at 50°C. By cooling the bed with the thermal wave, the low-pressure ammonia coming from the heat pump flows back into the array and adsorbs back on the adsorption material. Using the thermal wave, roughly half of the heat needed for heating the bed can be recovered from the cooling bed. This is key to obtaining a good efficiency of this system.

Use of renewable energy and efficiency

Possible sources of ambient heat are air, water and ground as well as waste heat. Considering the primary energy, the performance is commonly declared as the gas utilisation efficiency (GUE) according to European Norm EN12309 or EN 16905. Additionally, a seasonal primary energy ratio is declared, that also takes into account the overall seasonal performance, the electrical consumption for pumps and control, and thus makes TDHP technology also directly comparable to other heating technologies.

A typical seasonal energy efficiency ratio for a TDHP used in average climate with high temperature emission systems (i.e. radiators) is greater than 1.1, and for low-temperature heating systems (e.g. floor heating) it is greater than 1.25, which is much higher than the respective values for traditional heating technologies. CO2 emissions are therefore reduced by the same factor as result of the high efficiency in the energy conversion. Likewise, all energy conversion appliances, also in the case of TDHPs a clean (or cleaner) energy vector (bio-methane, hydrogen, power gas) will result in a correspondingly clean heating function.