## 3 Results and Discussion
### Operational Functionality of Micro-Installations  
Improving the operational functionality as a result of optimizing the biogas cogeneration unit eliminates significant technical limitations and difficulties in operating the research installation by an individual farm and improves its energy efficiency [39]. Automatic synchronization of the cogeneration unit (Figure 7) with the public network and operation as a prosumer micro-installation in accordance with the Act on RES demonstrates the \"storage\" of temporary surpluses of electricity in the network. Before optimization, the control system of the cogeneration unit only enabled its operation in island mode on a separate energy network of the biogas plant with variable rotational speed (i.e., frequency of the generated electricity) and possible synchronization with the public network using a troublesome frequency converter. Moreover, such a mode of cooperation with the network is not permitted by the IRiESD of national DSO for recipients with micro-installations generating electricity, including the ENEA Operator, which is responsible for recipients in Ocieszyn. Figure 7: Control and monitoring system of the cogeneration unit after optimization: (**a**) diagram; (**b**) view of control cabinet (from the left) and unit cooler (from the right) (photo by [PERSON]). Optimization of the biogas cogeneration unit using the advanced Woodward controller of the easYgen 2500/easYgen 2800 series (made available for testing, installed and commissioned by Woodward Poland) enables automatic synchronization of the cogeneration unit with the public network (with the power factor required by the OSD usually as tg\(\varphi\) = 0.4) ENEA Operator and operation of the biogas installation as a prosumer micro-installation in accordance with the Act on RES of 20 February 2015 (Journal of Laws of 2015, item 478 as amended). In addition to eliminating the need to use a troublesome frequency converter and the parameters of cooperation of the cogeneration unit with the network of national with the IRiESD, the optimization made enables the use of all benefits for an individual farm as a prosumer in accordance with the Act on RES. This includes, among other benefits, ensuring the \"storage\" of temporary surpluses of electricity in the network and their collection during periods of increased demand for electricity on the farm:  
* For micro-installations with an electrical power of up to 10 kW, 80% of the surplus electricity supplied to the network can be downloaded free of charge (including the costs of electricity distribution) during the period of increased demand for electricity on the farm;
* For micro-installations with an electrical power of up to 50 kW, 70% of the surplus electricity supplied to the network can be downloaded free of charge (including the costs of electricity distribution) during the period of increased demand for electricity on the farm. For the research biogas installation in Ocieszyn with a cogeneration unit with a maximum electrical power of approx. 16 kW\({}_{e}\), due to the current average daily biogas production capacity of the fermentation tank and the average daily demand of the farm for electrical power of approx. 4-6 kW, the appropriate setting is registration as a micro-installation with an active electrical power of 9.9 kW in parallel operation with the public network. There is no need to compress biogas to power the cogeneration unit. Simplified high-pressure biogas supply system for a cogeneration unit engine (with a high-pressure reducer typical for applications in non-stationary engines--with low durability and expensive regeneration, additionally requiring heating with fluid from the combustion engine cooling system--i.e., for vehicles powered by compressed gas natural CNG) before optimization, required powering the unit with high-pressure biogas and the need to use energy-intensive biogas compressors feeding the unit.