Techno-economic assessment of biogas-fed CHP hybrid systems in a real wastewater treatment plant

The integration of solid oxide fuel cell (SOFC) systems and micro gas turbines in a reference wastewater treatment plant is proposed. The main scope is to utilize the available biogas in a real wastewater treat- ment plant (WWTP) to feed both the SOFCs and micro gas turbines (MGTs) to produce electrical power while covering the digester thermal demand of the plant. To do so, two cases namely SOFC-WWTP (in which the SOFC system is the only CHP unit), and SOFC-MGT-WWTP (integration of both SOFCs and microturbine systems) are proposed. Results show that use of microturbines along with the SOFC systems can increase the share of electricity covered by self-generation within the WWTP by up to 15% while keeping stable the coverage of the thermal load. Also, the energy efficiency of the novel system (SOFC- MGT-WWTP) is calculated to be 7% more than that of the SOFC-WWTP. Economic analysis results reveal that using microturbines, the payback time for whole the system could be reduced about 4 years. Also, for the short term scenario, the levelized cost of electricity for the SOFC-MGT-WWTP system is found to be 0.118 $/kWh which is about 12% less than that for the SOFC-WWTP system. However, for the long term scenario, the difference becomes remarkably les

Solutions for improving the energy efficiency in wastewater treatment plants based on solid oxide fuel cell technology

Polygeneration configurations for small power generation systems offer significant potential for energy saving and reducing carbon emissions in wastewater treatment facilities. In this work, a biogas-fed solid oxide fuel cell system operating in a wastewater treatment plant (located in Turin, Italy) is analyzed in terms of its potential improvements through novel polygeneration systems. In its present combined heat and power configuration, along with electrical power, thermal energy from the exhaust gas is recovered to provide required heat to the plant’s anaerobic digester. The analysis is focusing on different energy efficiency solutions for this type of plant by using solar thermal collectors, microturbines, a trilateral Rankine cycle, and an absorption chiller. Results reveal that, despite of higher efficiency for the trigeneration case using both trilateral Rankine cycle and absorption chiller (up to 88.4%), the solar integrated system results in the lowest natural gas consumption, which is 38.5% lower than the baseline scenario. This same scenario is also the worst in economic terms due to the high capital costs of solar collectors. In a short-term cost trajectory of the solid oxide fuel cell technology, the most economically favorable scenario is the microturbine integrated case in which the calculated levelized cost of electricity is 0.11 €/kWh, lower than grid electricity price, and with payback time of 6.5 years. Long-term cost trajectory is indeed generating effective investments for all of the four scenarios with payback time between 3 and 5 years in all cases. The analysis has been developed to the entire European Union area: the most suitable market conditions are found in Germany, Denmark, Slovakia, and Italy

Technology review and thermodynamic performance study of a biogas-fed micro humid air turbine

Biogas is a proven and valuable energy source today for the combined production of heat and electricity (CHP). One of the most reliable and efficient technologies for the CHP application using biogas is represented by microturbine (MT). This prime mover not only shows a very flexible behavior towards change in the fuel composition, but it also sticks out for its reliability, small size, and low weight. Moreover, micro humid air turbine (mHAT) cycle, which is still under development, provides a relatively simple and inexpensive solution to increasing the power output of the microturbines. In this paper, the thermodynamic model of a novel CHP system based on a 500 kW micro humid air turbine (mHAT) in a wastewater treatment plant (WWTP) is presented and discussed. Furthermore, some considerations regarding an appropriate biogas treatment system and heat recovery module are discussed. The results presented in this paper show how the proposed biogas-fed plant can achieve an electrical efficiency of 46.6% together with a CHP efficiency of 81.2%. The impact of integration with WWTPs is beneficial where both biogas and required water for inlet air humidification are available

Solar-assisted integrated biogas solid oxide fuel cell (SOFC) installation in wastewater treatment plant: Energy and economic analysis

A unique cogeneration system integrating a biogas fed Solid Oxide Fuel Cell (SOFC) and a Concentrating Solar Thermal (CST) system for a reference Waste Water Treatment Plant (WWTP) in Italy is proposed. Biogas – which is locally in the WWTP from the anaerobic digestion (AD) of the collected sludge – can be used to produce electricity using SOFC power modules. The thermal power recovered from the SOFC exhaust stream is used to meet part of the digester thermal load. However, the rest heat loads are provided by using the integration with the CST system and an auxiliary boiler. Energy analysis is performed to determine the effect of using the solar heating system on the system performance. Also, the economic performance is evaluated through a cash-flow analysis and the calculation of the Levelized cost of electricity (LCOE). It is observed that installing 300 m2, 700 m2, 1100 m2 of solar collectors could cover 8%, 18% and 30% of total digester heat load, respectively. Results show an overall beneficial effect of the solar installation, both from an energy and economic standpoint of view. For all the scenarios analyzed, the LCOE is lower than the grid electricity price and, with increasing solar integration, the value is further reduced showing that, despite the investment return time, the electricity production during the entire system lifetime is competitive against grid electricity prices

Solutions for improving the energy efficiency in wastewater treatment plants based on solid oxide fuel cell technology

Polygeneration configurations for small power generation systems offer significant potential for energy saving and reducing carbon emissions in wastewater treatment facilities. In this work, a biogas-fed solid oxide fuel cell system operating in a wastewater treatment plant (located in Turin, Italy) is analyzed in terms of its potential improvements through novel polygeneration systems. In its present combined heat and power configuration, along with electrical power, thermal energy from the exhaust gas is recovered to provide required heat to the plant's anaerobic digester. The analysis is focusing on different energy efficiency solutions for this type of plant by using solar thermal collectors, microturbines, a trilateral Rankine cycle, and an absorption chiller. Results reveal that, despite of higher efficiency for the trigeneration case using both trilateral Rankine cycle and absorption chiller (up to 88.4%), the solar integrated system results in the lowest natural gas consumption, which is 38.5% lower than the baseline scenario. This same scenario is also the worst in economic terms due to the high capital costs of solar collectors. In a short-term cost trajectory of the solid oxide fuel cell technology, the most economically favorable scenario is the microturbine integrated case in which the calculated levelized cost of electricity is 0.11 €/kWh, lower than grid electricity price, and with payback time of 6.5 years. Long-term cost trajectory is indeed generating effective investments for all of the four scenarios with payback time between 3 and 5 years in all cases. The analysis has been developed to the entire European Union area: the most suitable market conditions are found in Germany, Denmark, Slovakia, and Italy.Flight Performance and Propulsio