Prototypical Biomass-Fired Micro-Cogeneration Systems—Energy and Ecological Analysis

• Main Author: Krzysztof Sornek
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Energies
• Subjects: cogeneration; thermoelectric generator; Rankine cycle; biomass; renewable energy
• Online Access: https://www.mdpi.com/1996-1073/13/15/3909

Combined heat and power systems dedicated to micro-scale applications are currently increasing in popularity. The use of such systems is beneficial from the standpoint of increasing the usage of renewable energy, increasing energy efficiency and reducing CO₂ emissions into the atmosphere. This paper shows two examples of prototypical micro-cogeneration systems powered by biomass. In the first, smaller one, electricity is generated in thermoelectric generators using heat from the wood-fired stove. The second one is equipped with a 100 kW_t batch boiler and operates according to a modified Rankine cycle. The energy and ecological analysis were conducted and discussed, including selected aspects of heat and power generation and gaseous pollutant emission. Measurements were performed using a dedicated control and measurement station with a PLC controller. As was shown, thermoelectric generators operated respectively with the power of 22.5 W_e in the case of the air-cooled unit and 31.2 W_e in the case of the water-cooled unit. On the other hand, the maximum power level of ca. 1145 W_e was obtained in the system with a batch boiler operating according to a modified Rankine cycle. The ecological analysis showed that the average amount of CO emission during the wood combustion in the tested stove was 1916 mg/m³ (in the combustion phase). In the case of straw combustion, it was characterized by lower CO₂ emissions compared to coal, but higher CO₂ emissions compared to gasoline and natural gas. Based on the obtained results, some outlines for the systems development were given.