Barcelona Metropolis

The city, as a great guzzler of energy produced outside its borders, is committed to an energy transition that will allow for its decarbonisation. The first pillar is to move the mobility model towards a system of shared electric vehicles. However, buildings’ energy consumption must also be changed and gas must be relegated to a secondary role as a heat supplier. The solutions include the large-scale installation of photovoltaics on roofs and, in particular, aerothermal systems, which would be conceivable with economy of scale proposals such as citizen energy communities (CECs), an entity already covered in a European directive.

City and energy. It has been a binomial of two factors that, for as long as we can remember, have never gone hand in hand. Cities have always been holes that guzzled the energy produced elsewhere. From the grain brought from Egypt to ancient Rome, to industrial London, which consumed coal extracted from mines all over England and generated serious air quality problems in the 19^th century, to modern cities that consume energy brought in from all over the world to run heating systems and ensure mobility. Cities, synonymous with civilisation and culture, are also the manifestation of the separation between the biosphere and humankind, with their capacity to gobble up natural resources. The question we must ask ourselves is whether the city could become a physical space for reconnecting with nature. Beyond the need to create space for recreation and the introduction of biodiversity, might it be able to run on the generation of its own energy?

In the 20^th century, the energy transition was not part of the municipal agenda, because it was not a challenge that could be met. Resources, thinking and proposals were available for educational and cultural policies, and the urban planning model was thought out and rethought. But now they must also have an energy transition strategy, since the climate scenario demands it (cities generate 70% of greenhouse gas (GHG) emissions), and, for the first time, they can supply themselves with a significant proportion of the energy they consume. Not entirely and not at all times, but a significant proportion of it.

The first point to keep in mind is that mobility consumes a large amount of energy and generates most of the emissions produced in the city. According to the study The Future of Sustainable Cities: Urban Energy Transition to 2030, published by Deloitte in March 2019, in a Mediterranean city like Barcelona, 62% of GHGs come from mobility, while mobility accounts for 40% of energy consumption and the residential sector is responsible for 60%.

The conclusion is quite obvious: decarbonising the city calls for a courageous strategy aimed at traffic calming, greening the urban landscape and, at the same time, coming up with proposals for city access that allow for sustainable entry and exit. These measures must be accompanied by a proposal that can bring about the necessary change in culture with regard to the use of private vehicles. Throughout the 20^th century, Western societies have associated so-called freedom with car ownership. These vehicles, which are used only 2% of the time, take up 70% of public space. But the reality is that the inhabitants of big cities do not need a car for their day-to-day lives, but only for certain times.

A proposal needs to be widely implemented to move from a culture of ownership to one of service, in which private vehicles are used as a means of transport that is returned once the need is met. This model would undoubtedly imply more intensive vehicle use and less occupation of public space, and should be linked to a system of shared electric mobility. The fight for superblocks and for a change in the city model is, above all, a cultural battle; to bring it to fruition, improving the streets and neighbourhoods concerned is crucial. It must be backed by a proposal to move from the culture of vehicle ownership to one of vehicle service.

Retrofitting roofs with photovoltaic panels

The other major issue is buildings’ energy consumption. Cities need electricity, which until now has been brought in from elsewhere, and gas to heat homes and run industries. This source accounts for more than one third of energy consumption in the residential sector, which makes it clear that consumption needs to be reduced and that we need to move towards an electrification landscape that eliminates gas from homes. Today, greater efficiency comes from options such as hot and cold air pumps and aerothermal energy. In turn, in the climate change scenario, thermal comfort will increasingly be aimed at coping with heat waves, with a greater need to provide cooling, and to improve insulation to deal with high temperatures.

But the question we must ask ourselves is whether our cities can move from a scenario of absolute energy dependence to one that sees a large-scale roll-out of renewables. It is in this context that we must say that we need to bring about a change in the appearance of roofs and some public spaces. Today, the cheapest kWh comes from renewable sources and, particularly, from photovoltaic energy. The relevant regulatory framework (RD 244/2019) allowed for shared self-consumption through a low- or medium-voltage grid, within a radius of 500 metres between the installation and the consumption points. The Council of Ministers later extended it to 1,000 metres and last November Minister Teresa Ribera announced that it would be extended to two kilometres. This brings it closer to more advanced regulations, such as that of Portugal, where shared self-consumption may have a radius of two kilometres for low-voltage lines, four kilometres for medium-voltage lines and up to twenty kilometres for very high voltage lines.