According to the Federal Environment Agency (Umweltbundesamt UBA) the percentage of cooling capacity for the demand for electricity is about 14% and results in 5% of the direct and indirect greenhouse gas emissions. These numbers show the relevance to the climate of the cooling technology. Moreover, these numbers are responsible for the initial question of a study of the UBA: How can sustainable cooling supply look like in Germany?
Structure of the study
The publication of the UBA deals with a climate friendly supply of coldness for building climate control and industrial refrigeration. The first step observes the cooling demand of the single application sectors as well as a characterization of the used cooling technologies. Energy demand, greenhouse emissions and costs shall be determined via operational simulations for different systems of the building climate control and the industrial refrigeration. This is followed by an analysis of the market potential of climate-friendly cooling technologies as well as recommendations for the increase of this potential.
Industrial refrigeration and building climate control
The study has two subjects of discussion for two different application sectors for the provision of refrigeration in Germany: industrial refrigeration and building climate control. According to the definition of the UBA, industrial refrigeration includes process cooling, storage of initial, intermediate and final products, the climate control of mainframe computers for the industrial sector, and cabinet air conditioning. Climate control of office buildings, server rooms, computer centers and the climate control of clean rooms and production facilities fall under the category of building climate control.
Cooling technologies
There are various different technical system concepts for climate control. Ventilation technology and air conditioning are separated into their thermodynamic functions. DIN V 18599-7, which provides the rules for the realization of ENEV 2009, divides them into air conditioning, partial air conditioning and ventilation systems. These are distinguished by systems with central and decentral make-up air systems, the functions cooling, dehumidify and heat recovery are assigned to them. Another classification takes place in the sectors of only-air-systems, air-water-systems and air-refrigerant-systems. There are several approaches to the evaluation of the climate friendliness of the systems, which refer to different details of the system. Details of the system with high impact to the climate friendliness of air conditioning systems include the refrigerant, the quantity of refrigerant needed, and the surface of the heat exchanger.
Study results
The aim of the study of the UBA was the evaluation of the different technologies of refrigeration, according to ecological and economical point of views to determine if the impact to the climate was of paramount importance. As a result, it can be concluded that in the field of industrial refrigeration the decrease of the energy consumption played a predominant role as the system generally is operated all year round. In the field of building climate control, the avoidance of climate damaging partly fluorinated hydrocarbons (HFKW) as refrigerant should be given special consideration. If avoidance is not possible, the leakage of the refrigerant into the environment should be prevented as much as possible. Based on simulated calculations, the authors have been able to show that cooling units with non-halogen, natural refrigerants are much more climate-friendly. This is because they are more energy-efficient and they show none or an avoidable quantity of direct emissions (refrigerant emission) which are climate-relevant. Next to the comparison of the systems, the study also determined the percentage of the cooling demand in the fields of building climate control and industrial cooling, which can be covered by heat-driven cooling systems instead of compression refrigeration systems. In case of solar or waste heat, the absorption chiller is very energy-efficient and shows the least greenhouse gas emission of all systems that have been examined in the study.