Table 3 Urban systems and nexus issues: A decarbonisation example

Systems understanding has practical implications for many urban challenges and missions. For example, transformational resolution of the four urban renewable energy issues below needs to appreciate their interdependencies, drawing on each of the knowledge themes in the KUST framework (Fig. 3). Transformation requires capacity-building including shared intent; broader and more strategic urban planning processes with evaluation of options’ co-benefits, trade-offs, and outcomes beyond decarbonisation; multiple demonstrations in cities; supportive policies at state and federal levels; and serious stakeholder and community engagement (Theme A in Fig. 3). Renewable options exhibit significant spatial differentiation across five ‘urban fabrics’ (central city walking, inner city transit, outer suburb automobile, peri-urban and rural bioregional, and remote settlement (Seto et al. 2021)), combined with urban process nexus interdependencies (Theme B). Options also reflect technology opportunities (Theme C) and resilience needs (Theme D). Solutions need support from ‘urban systems’ knowledge, and infrastructure for knowledge sharing (Theme E). With its high renewable energy potential and take-up, such issues are already significant for Australia.

1. Renewables and local storage opportunities in urban fabrics

Issue: Distributed solar storage options to help stabilise supply to the city-wide and regional grid include individual and community batteries and, in the rapidly emerging future, batteries in electric vehicles; smart technologies that are able to quickly turn appliances on or off; households and businesses with appliances that only turn on when solar is maxing out and have a tariff to reflect this; phase-change material attached to air conditioning that enables excess solar to be stored for later air conditioning; large hot water storage for use later; and even mini pumped-hydro storage in a back yard tank for multiple other local urban functions. Urban planning responses: Such transformational options vary with the part of the city and hence different urban fabrics could be enabled to have different storage functions. This avoids recourse to curtailing distributed solar, or else traditional large centralised grid solutions like pumped hydro which are costly and take years to build. Co-benefits: Greater decarbonisation, energy savings and supply resilience. (See further in Green and Newman 2022; Newman 2020a).

2. Electric vehicle automobile dependence and wastage of renewable power

Issue: Switching from diesel or gasoline cars to battery electric vehicles is likely to happen quite quickly as capital costs become equivalent from around 2023, while fuel costs and maintenance of EV’s will be lower. EVs can also contribute power to the grid. However, EV popularity could encourage even greater automobile dependence, which is associated with multiple sustainability issues. It would also waste solar and wind renewable energy that is desperately needed for replacing all fossil fuels including those used in industry for processing materials and making all kinds of products. Urban planning responses: Urban planning needs to focus on reducing automobile dependence as well as decarbonising all sources of power. This includes rebuilding the city with much greater e-transit, e-rideables and walkability around corridors, precincts and buildings that are net zero, based on solar PV’s, with solutions including closer integration of land use (housing type and densities, jobs, services, public space, biophilic design) and transport, tailored to different urban fabrics. Co-benefits: Greater decarbonisation; reduced congestion and travel times; improved liveability, productivity, and health outcomes. (See further in Seto et al. 2021; Newman et al. 2021).

3. Hydrogen-based wastage of renewable power

Issue: There is growing awareness that renewable energy based (green) hydrogen has major strategic value as a fuel for industrial processing of primary products due to its value as a reducing agent as well as a strong heat source; and for aviation, shipping and some long-distance trucking functions. Most other potential functions for hydrogen in buildings and transport, including in cities, can be better done by solar-based electricity as this is much cheaper than using the same power to make hydrogen, store it and transport it – each step involving significant thermodynamic losses. If hydrogen-based renewable power is being wasted then such practices are also reducing the ability of the world to rapidly decarbonise. Urban planning responses: Incorporating tools such as life cycle carbon and cost accounting assessments alongside spatial planning should evidence the above, and help spatially prioritise proximity of hydrogen production, industrial processing and nearby regional ports, to be transformed into regional hydrogen settlements and economies. Co-benefits: Renewable energy use optimised; new industry and economic growth in regional areas. (See further in Whitehead et al. 2022).

4. Biophilic urbanism and local renewable power

Issue: Biophilic urbanism has given new life to the planning of cities using natural processes and ecosystems built into and onto buildings and infrastructure. These systems are a major contributor to achieving SDG’s and enabling cooling in a warmer world. However, biophilics can be used to dominate roof spaces and street spaces so that solar energy potential is reduced. This is a nexus between two beneficial uses of urban space and needs to be worked out in every new development and every regeneration project. Urban planning responses: Analysis will provide multiple options: to plant in streets and use any associated buildings and spaces such as car parks for solar PV; to do biophilic planting and solar provision in spaces not directly on the site of the development but which can be certified as offsets on nearby land, and used by people living or working in the development; and/or by intricate design work that enables both biophilics and solar PV to be integrated into any spaces. Solutions will depend on the kind of urban fabric and many factors such as climate, to enable a systems-based solution. Co-benefits: Balancing biophilic with solar energy solutions provides multiple ecosystem services, health and wellbeing benefits alongside decarbonisation. (See further in Beatley 2017; McDonald et al. 2018).