## 4 Conclusions  
MainBox prototype units were designed and built. The solution is optimized in terms of greenhouse gas emissions by maximizing energy efficiency and using natural refrigerant in refrigeration and freezing systems. The innovative food box solution is a breakthrough in the food market, as it has a huge commercial potential while reducing the negative effects of civilization (food waste) and climate change. The device uses a working fluid with low greenhouse effect creation potential; this will enable practical implementation of legislative requirements (national and international) regarding the so-called greenhouse gases. The following innovative solutions have been introduced in the MainBox device:  
* The refrigeration unit was adapted to work in external conditions by installing additional elements (pressure switches for protecting compressor, pressure switch for condensing pressure control).
* Temperature control in individual boxes correlated with temperature of return air to cooling unit was designed and heating of chambers was ensured.
* Optimum access to the boxes was ensured.
* Propane as a natural refrigerant was used (high energy efficiency, low GWP), eliminating its amount and sealing the device, thus reducing the risk of explosion (the device met the requirements of fire and safety regulations).  
The correct MainBox device operating parameters were maintained with a properly functioning system for the cooling units control and a temperature monitoring system.  
At the beginning, the identified structural imperfections in the modules made it possible to react quickly and performed modifications to the insulation that would ensure appropriate storage conditions and reduce the need for cold. Summarizing the conducted  
Figure 13: Thermograms of the freezing module—thermal bridges on the side wall of the module and insulation caused leakage between the module and the monoblock.  
therm provision examinations, it was found that there were no anomalies in the operation of the equipment, no anomalies of the MainBox insulation, and no anomalies related to overheating of wires, excessive load on electrical connections. Thermal imaging studies of the temperature of food stored for 24 h in refrigeration and freezer furniture showed optimal temperatures of these products.  
Thermal imaging tests and temperature monitoring have confirmed that the designed and manufactured food storage devices allowed maintaining optimal temperature conditions inside the chambers. MainBox is a device that allowed to safely receive food products at any time, which was a specific need during an epidemic time. Rational use of energy in the agro-food industry through optimization of thermal processes translated into ensuring food safety throughout the entire cold chain.  
The developed new product MainBox is an advanced food device that enables remote ordering and collection at any time of food products, previously delivered by a selected supplier. MainBox customers can easily and quickly make current purchases without unnecessary storage at home and pick up the ordered purchases (e.g., on their way home from work), preventing their expiration, spoilage and, consequently, wasting. MainBox will contribute to rational food management.