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Spanish scientists have proposed combining anaerobic digestion plants with photovoltaic-thermal panels and have discovered that this combination can reach an LCOE of $0.045/kWh in several locations in Europe and North America.
Researchers from the University of Valladolid and the Polytechnic University of Madrid (Spain) have proposed hybridizing biogas and biomethane production systems from the anaerobic digestion (AD) of bovine manure with photovoltaic-thermal energy (PVT) ).
An anaerobic digestion plant is an energy facility capable of producing methane from manure.
“Decentralized energy production systems offer opportunities for local resource exploitation, along with energy self-sufficiency in remote communities,” the scientists explained, noting that the use of solar panels for both electricity and heat in the Anaerobic digestion of organic waste could be suitable for isolated areas. “The decentralization strategy will require that new digester configurations be able to operate with minimal operating costs in areas with limited energy connectivity, where organic substrates are produced.”
The PVT system conceived by the group is connected to a combiner box with batteries, and is used to operate the digester, pumps, mixers and biogas upgrading unit. The latter is used to produce biomethane and is turned off during periods of low irradiation levels.
The thermal energy collected by the panels is used to increase the temperature of the digester until optimal conditions of 35ºC are reached. The heat is then transferred through a network of tubes, allowing hot fluid from the solar panels and cold fluid inside the anaerobic digester to circulate.
To analyze the novel decentralized production system, scientists have assumed that it works on a medium-sized pig farm with 2,000 heads, using its manure. According to scientists calculations, this operation will have a daily electricity consumption of 38.3 kWh. The improvement unit, according to them, will require 0.125 kWh/m3 of biogas.
Using a series of equations, the research group has evaluated the production of the installation in varied climatic conditions in five locations around the world: Soria (Spain), Iowa (United States), Odense (Denmark), Santa Catarina (Brazil) and Laixi (China). Their irradiance values ??and ambient air temperatures were obtained from Solargis software.
The analysis showed that Odense had the lowest irradiance and was the only place where the system was unable to meet the necessary electricity demand. “In the rest of the locations, only a part of the production, in greater or lesser quantities, would be used to maintain the temperature of the digester, but in any case, ensuring its operation and the generation of biomethane throughout the year,” the scientists explained.
The annual volumes of biomethane were between 14,107 m3 in Odense and 29,607 m3 in Santa Catarina. Annual production in Soria and Laixi is similar, with an average of 25,000 m3. Regarding the use of biomethane in these areas, the annual biomethane savings were up to 65%.
An economic analysis of the levelized cost of electricity (LCOE) over 20 years of operation found an average value of $0.045/kWh for the five locations. “The economic study revealed that the PV/T hybrid solar technology proposed to improve the conventional anaerobic digester presents a remarkably competitive LCOE value compared to other technologies in the energy sector,” the researchers noted.
They presented their evaluations in the article “ Hybridization of anaerobic digestion with solar energy : A solution for isolated livestock farms,” published in Energy Conversion and Management: X. |
