Integration of deep geothermal energy and woody biomass conversion pathways in urban systems

Abstract

Urban systems account for about two-thirds of global primary energy consumption and energy-related greenhouse gas emissions, with a projected increasing trend. Deep geothermal energy and woody biomass can be used for the production of heat, electricity and biofuels, thus constituting a renewable alternative to fossil fuels for all end-uses in cities: heating, cooling, electricity and mobility. This paper presents a methodology to assess the potential for integrating deep geothermal energy and woody biomass in an urban energy system. The city is modeled in its entirety as a multiperiod optimization problem with the total annual cost as an objective, assessing as well the environmental impact with a Life Cycle Assessment approach. For geothermal energy, deep aquifers and Enhanced Geothermal Systems are considered for stand-alone production of heat and electricity, and for cogeneration. For biomass, besides direct combustion and cogeneration, conversion to biofuels by a set of alternative processes (pyrolysis, Fischer-Tropsch synthesis and synthetic natural gas production) is studied. With a scenario-based approach, all pathways are first individually evaluated. Secondly, all possible combinations between geothermal and biomass options are systematically compared, taking into account the possibility of hybrid systems. Results show that integrating these two resources generates configurations featuring both lower costs and environmental impacts. In particular, synergies are found in innovative hybrid systems using excess geothermal heat to increase the efficiency of biomass conversion processes. The application to a case study demonstrates the advantages of using a system approach for the analysis over a stand-alone comparison between options.

RES Implementation in Urban Areas: An Updated Overview

“…Ground source heat pump technology, transferring heat stored from the ground to heating/cooling systems in buildings, can meet the requirements of low-temperature heating, which constitutes the largest share of heat demand in cities [78]. Moret et al [79] studied the dependence of geothermal potential on local geology and groundwater depth, with a positive assessment of integration of geothermal energy in urban systems. Nevertheless, as discussed in Bauer et al [80], geothermal sources have some constraints, in particular in highly populated urban areas where competition for land is strong.…”

A Mixed-Integer Linear Programming Formulation for Optimizing Multi-Scale Material and Energy Integration

“…Bolliger (2010) described an integrated toolbox and explained the methodology behind it. Moret et al (2016) summarized an MILP formulation in a compact form, covering the main sets, parameters, and variables. Computational burdens for large problems have led to increasingly more efficient implementations of the framework in various languages, such as Lua (Miller et al, 2009).…”

Is the Fischer-Tropsch Conversion of Biogas-Derived Syngas to Liquid Fuels Feasible at Atmospheric Pressure?

“…System analysis is an approach that addresses a subject in terms of interlinked subsystems to create a broader understanding of the key factors affecting the success of the system [28]. Although a systems approach has been used to analyze aspects of biogas and FT fuel production [29][30][31] and optimization [32], no literature was found on liquid fuel production from biogas and none of the literature adopted a systems approach to investigate the effect on overall activity and liquid fuel selectivity of sudden interruptions during operation as could occur in an AD plant, such as feed gas shutdown, temporary electric cut-off, loss of continuous heating, and feed ratio alterations, for more than six days of continuous operation. This knowledge is needed to inform the real-world application of the technology, and this paper addresses this novel area of research.…”