CloudFridge

Renewable energy sources such as solar energy or wind energy are characterized by a high degree of variability. This poses great challenges for the power grid, which must compensate for the variability of the sources and loads. In addition to balancing by conventional power plants, this can be achieved by storing energy – for example, using storage power plants in the form of potential energy. An alternative approach of storing energy in the form of heat (or even cold) has hardly been used so far.
Given the large number of refrigeration circuits in refrigerators, heat pumps, air conditioners, etc. (in Europe alone, around 22 million new refrigerators are sold per year according to the APPLIA Home Alliance Europe Report 2020; according to the IEA, 16% of the global demand for electrical energy will be used for cooling and freezing in 2050), these in their entirety represent a considerable potential for energy storage – especially using phase change materials. Cooling/heating can be “produced in stock” so that storage can be filled during energy peaks in the grid and emptied during load peaks. However, this requires accurate determination and knowledge of the operating states of the refrigeration circuits in the grid.
The present project deals with sensors for the determination of these operating states. In addition to the usage of refrigeration circuits as energy storage devices, sensors enable further improvements in the efficiency of the devices by optimized control of operating states, which represents a considerable savings potential per year due to the enormous number of devices.
Besides temperature, pressure and vibration sensors, the modular sensor concept also provides sensors for icing detection, which means that deicing cycles can be optimized, resulting in additional and considerable energy savings potential.
The major challenge in this area is the enormous cost sensitivity of such products for the mass market, since despite the new EU labeling regulation for new equipment, initial costs continue to be a major factor in consumers’ purchase decisions. Thus, the costs for individual sensors, including installation and connection, must be in the order of magnitude of well under ten euros. In the case of wired sensors, the costs for cables, cable feedthroughs (through insulation) and cable connections would already be too high such that the requirements can only be met by wireless sensors. In addition, many installation situations require miniaturized sensors. Maintenance-free operation is also only possible if the energy supply to the sensors can be self-sufficient by means of energy harvesting and durable rechargeable energy storages.
Pressure and temperature measurements are of most interest from within the compressor housing; at the same time, the normative and safety situation prevents the additional implementation of feedthroughs. Therefore, a self-sufficient solution is mandatory. Energy harvesting systems such as solar, pyroelectric or HF based systems are not suitable due to the lack of electromagnetic transmission or too low temperature differences. Battery powered solutions have the disadvantage of limited lifetime and do not meet desired aspects of sustainable living. Thus, systems that can use the mechanical vibration energy of the compressor are a preferred option. In principle, piezoelectric and inductive systems can be used; the piezoelectric element can also be used as a sensor and tends to have a more favorable form factor for the application.
The present project therefore aims to develop a modular concept for sensors that can be integrated into refrigeration circuits and to precisely determine the resulting energy-saving potential and possibilities for net/grid balancing during production and load peaks. In addition to the reduction of CO2 production and energy savings, the project will also enable new business models for manufacturers as well as end customers, which can offer an additional economic advantage and incentive to support a rapid broad application of the technology.