Increased COP and flexibility

 

State of the art

 

In the adsorption heat pump field, only few theoretical studies were reported on the combination with a compression unit. Apart from the improved Coefficient of Performance (COP) and Energy Efficiency Ratio (EER) at the machine level, the hybrid heat pump concept offers substantially improved flexibility compared to conventional mechanical compression heat pumps in terms of continuous regulation of power consumption. While conventional mechanical compression heat pumps rely on a variable speed compressor for continuous power regulation, the hybrid heat pump offers important additional regulation of all circulatory pumps and fan speed for all thermal circuits. In addition, the hybrid heat pump may be controlled to shift its driving energy from electrical to thermal and vice-versa, which allows to prioritize one form of energy and support the operation of the overall system.

 

The GEOFIT solution

 

GEOFIT will feature the first ground source hybrid machine based on a cascading architecture, composed of an adsorption module whose cold output is used for the cooling of the condenser of a vapour compression unit.

An experimental campaign has been conducted for the validation of the benefits achievable with the cascade configuration for air conditioning (chiller) applications. The performed measurements have experimentally validated an increase in electrical EER (i.e. cooling COP), in cooling mode, which can reach values up to 7.0. This clearly confirms an advancement beyond the state of the art, considering that electrically-driven heat pumps for the same applications have COPs in the range of 3.0 to 3.5. The sorption heat pump will employ water as refrigerant, having zero Global Warming Potential, thus further decreasing the polluting potential of this technology.

 

The GEOFIT contribution

 

The configuration of a hybrid heat pump prototype with nominal cooling capacity of 10 kW has been already tested in a lab-controlled environment. The prototype will be scaled-up to 50 kW. The cascade unit is composed of an adsorption module whose cold output is used for the cooling of the condenser of a R410A vapour compression unit. The system is based on a commercial silica gel adsorption unit with two absorbers working in counter-phase, with a nominal thermal COP of 0.6.

 

Technology readiness level improvement: From TRL5 to TRL7