## 3 Results and Discussion
### Operational Functionality of Micro-Installations
The biogas was compressed (and stored in cylinders), creating additional threats, only to be expanded in a reducer at the entrance of the generator to a pressure of approximately 1 bar, feeding a simplified mixer for preparing the air-gas mixture to power the engine of the cogeneration unit. Optimization of the biogas supply system for the cogeneration unit engine using a low-pressure power supply system (including a zero-pressure reducer and a low-voltage cut-off solenoid valve available for testing) allows the cogeneration unit engine to be powered with biogas at a low pressure of at least 20 mbar (i.e., 2 kPa), which prevails at the outlet of the fermentation tank of the biogas plant. As a result, after optimization, the need to use the following in the biogas plant was eliminated:  
* Energy-consuming biogas compressors feeding the unit;
* Cylinders supervised by the Office of Technical Inspection;
* Heating the high-pressure reducer. Increasing the energy efficiency of a micro-installation by reducing its own needs for the generated electricity. The energy system of the research biogas plant before the optimization of the cogeneration unit is characterized by the significant demand of the biogas plant for the electricity generated by the cogeneration unit:  
* High electricity consumption before optimization by the variable speed control system of the cogeneration unit and the biogas plant operation control systems;
* Large losses of electrical energy through the frequency converter;* Large losses of thermal energy before optimization by the heating system with direct heat collection from cooling the engine of the cogeneration unit without a plate exchanger;
* Large losses of electrical energy before optimization by biogas compressors and losses of thermal energy from cooling the engine of the cogeneration unit when heating the reducer and expanding the biogas in the unit. Optimization of a biogas cogeneration unit using an advanced Woodward controller of the easYgen 2500/easYgen 2800 series with automatic synchronization of the cogeneration unit with the ENEA Operator public network (eliminating the need to use an energy-intensive frequency converter and a serious loss of efficiency when the cogeneration unit engine operates at variable speed rotation) allows for a significant reduction in the biogas plant's own demand for electricity generated by the cogeneration unit. Optimization of the biogas supply system of the cogeneration unit engine using a low-pressure system (with a zero-pressure reducer and a low-voltage cut-off solenoid valve) instead of the high-pressure system used before optimization allows for the elimination of the need to use energy-intensive compressors of biogas supplying the unit and to heat the reducer expanding the biogas in the unit, thus resulting in a significant reduction in the biogas plant's own demand for electricity generated by the cogeneration unit and thermal energy losses from the cogeneration unit engine when heating the reducer. Optimization of the heating system of a cogeneration unit using a separation plate heat exchanger (provided for testing by the manufacturer of heating equipment WOMIX) allows for avoiding heat energy losses from the unit engine caused before optimization by the heating system with direct heat collection from cooling the engine of the cogeneration unit without an exchanger plate-wise. The above-described significant reduction in the biogas plant's own demand for electricity generated by the cogeneration unit and the reduction of heat energy losses from the cogeneration unit engine makes it possible to significantly improve the energy efficiency of the research biogas plant:  
* Increase the amount of electricity supplied to an individual farm;
* Increase the amount of thermal energy supplied in the winter and transitional seasons to heat the fermentation tank, increasing the efficiency of biogas production and, as a result, increasing the power of the cogeneration unit powered by it.