How close can cities get to 100% renewable energy?

24 Oct 2018 Dave Elliott

(Courtesy: iStock/adrian825)

Around the world, cities are beginning to think in terms of meeting their energy needs from renewable sources, to limit air pollution and climate change problems. Over 100 cities now claim to get at least 70% of their electricity from renewables, compared to 42 in 2015, and many more are aiming for high proportions, as part of a drive to “100% renewables”. With cities responsible for over 70% of global carbon emissions from energy use, that is to be welcomed, but it’s worth being a little clearer about what’s meant by “100% renewable” cities.

For rural communities, the growing appetite of cities for their resources may be perceived as a threat. Rural areas very often do not meet their own needs with locally produced energy; so how could they consider supplying other territories?CLER, Energy Cities and Réseau Action Climat

Rooftop PV solar is ideally suited to use in cities but there are limits to the surface area available. Multiple occupancy high-rise buildings all share one roof, and land for ground-based units is scarce. Bio waste can provide some energy but, in general, given the spatial constraints and high urban energy use, it is unlikely that many cities can generate all their power from renewable sources within the city boundaries. They will have to import some of it from rural areas. That is nothing new. Cities already import most of their energy, as well as their food and water. Cities can reduce emissions by reducing energy use and generating some renewable energy from within their boundaries, but they will also have to import.

Internal ratio

Some idea of the relative ratio of the internal to imported energy that will be needed is provided by the results of the EU Energy Cities initiative. It found that, by 2013, the 13 cities involved in the programme could meet 44% of their energy needs from locally produced energy, some of that involving the use of fossil fuels. However, the renewable proportion (4.38 TWh) was only around 16% of the local generation total (26.77 TWh), or about 7% of total energy use. It should hopefully be possible to increase the “local generation” total, some of which can be low carbon, and, crucially, to boost the renewable proportion achieved by initiatives like this; these cities had, reportedly, tripled their renewables share since 2010. What’s more, with low-cost PV, it should now be possible to do much better than 7%, and even better in the future.READ MORE

Can we get to net zero emissions?

An updated Energy Cities/CLER/RAC report (PDF) did indeed suggest that by 2050 Frankfurt could be producing 25% of its energy from internal renewable sources and getting 25% from renewables in the wider metropolitan area. The report also noted that Malmö in Sweden was aiming for 50% from inside the city, with both these targets backed up by a 50% cut in energy use. Even more dramatically, Frederikshavn in Denmark was aiming for 100% from the greater Frederikshavn region by 2050.

These are ambitious, possibly optimistic, targets, with in most cases some power still imported. The report notes that when aiming for this sort of goal “in most cases, a city or metropolitan area, due to its density, will not be able to cover its energy needs with 100% renewable energy produced on its territory, even after markedly reducing them. It will therefore have to outsource wood, electricity and biogas, as it already does for food”.

Rural relationships

It seems likely that cities will need to build good relationships with their hinterland. The report warns that “for rural communities, the growing appetite of cities for their resources may be perceived as a threat. Rural areas very often do not meet their own needs with locally produced energy; so how could they consider supplying other territories? And rural or suburban territories which have had to put up with city annoyances in the past (installation of an incinerator, landfill site or the spreading of sewage sludge) are unwilling to see their environment spoilt to satisfy the needs of city dwellers.”

Rural or suburban territories which have had to put up with city annoyances in the past (installation of an incinerator, landfill site or the spreading of sewage sludge) are unwilling to see their environment spoilt to satisfy the needs of city dwellers.CLER, Energy Cities and Réseau Action Climat

Rural communities have always serviced cities, most obviously by producing food, and earned a living from doing so. When the latter has not been the case, or rural communities have not been otherwise compensated, there have sometimes been significant conflicts, for example, when rural valleys are inundated to create reservoirs primarily to provide water for cities, or when major hydro projects are built for large-scale energy production with power fed to the national grid. Local communities have strongly opposed some large hydro projects in developing countries as they stood to enjoy few of the benefits but incur most of the impacts. Battles like that are still occurring around the world.

Objection or win-win?

Conflicts on that scale have yet to occur in relation to UK wind and solar farms but there have often been objections to them and, if more are needed to service cities, local rural residents may ask why they are having to accept environmental and amenity loss in order to meet the needs of city dwellers.

The Energy Cities report faces up to this but, perhaps optimistically, says “here lies an opportunity to create a win-win relationship between urban and rural land areas. Cities have an interest in providing financial or technical support for the development of renewable energy production in neighbouring rural areas, thereby cementing local economic development and resilience. Likewise, rural communities, some of which are already engaged in a positive energy community approach, may also develop relations with cities, offering them access to their resources whilst keeping control of the projects and benefiting from locally generated revenue.”

These seem very reasonable as aims and aspirations, seeking out shared interests, but the devil will be in the detail. There will be many issues to resolve, not least the terms of trade, so as to maintain stable and reliable energy supply and cordial co-operative relationships. What the Energy Cities report calls a new social solidarity, rather than an exploitative relationship. It will be interesting to see how it goes. It won’t be easy for cities to get to 100% renewables, with transport probably the hardest issue to deal with, but technologically, it does seem possible to think in terms of renewables, from a range of sources and locations, supplying most of the energy needed by cities.

I have written a chapter developing the ideas above for a new book Sustainable Cities, out next year.

30/10/2018 FROM PHYSICSWORLD.COM