The multifunctional environmental energy tower: Carbon footprint and land use analysis of an integrated renewable energy plant

The Multifunctional Environmental Energy Tower (MEET) is a single, vertical, stand-alone renewable energy plant designed to decrease the primary energy consumption from fossil fuels, to reduce greenhouse gas emissions, to maximize the energy production from renewable sources available in place and to minimize land use. A feasibility case study was performed for the city of Rome, Italy. Several technologies are exploited and integrated in a single system, including a photovoltaic plant, a geothermal plant and a biomass digester for urban organic waste and sewage sludge. In the proposed configuration, the MEET could cover more than 11% of the electric power demand and up to 3% of the space heating demand of the surrounding urban area. An LCA analysis evaluates the environmental impact in a cradle-to-grave approach for two impact categories: global warming (carbon footprint) and land use (land occupation and land transformation). The functional unit is a mix of electric (49.1%) and thermal (50.9%) energy (kWhmix). The carbon footprint is 48.70 g CO2eq/kWhmix; the land transformation is 4.058 m2/GWhmix; and the land occupation is 969.3 m2y/GWhmix. With respect to other energy production technologies, the carbon footprint is lower and similar to the best-performing ones (e.g., co-generation from wood chips); both of the land use indicators are considerably smaller than the least-impacting technologies. A systematic study was finally performed, and possible optimizations of the original design are proposed. Thanks to the modular design, the conceptual idea can be easily applied to other urban and non-urban scenarios