Reading through a couple of pieces recently about heat mapping for district heating systems and another about rethinking city resilience took me back to Sarajevo during the Bosnian conflict and some real-life lessons in innovation and resilience from a city under siege.

I was a cub reporter at the time and Sarajevo was under blockade. Heating oil was not getting into the city, which meant that the district heating plants were effectively redundant. On the other hand, a quirk of political geography meant that some parts of the city were still linked to a functioning gas supply.

At this point, someone hit on a bright idea: drain all the water from the radiator systems in the apartment blocks; tap into the functioning gas lines and run the gas through the streets into the apartment buildings; and then connect the whole thing up so that each resident could tap their radiators for gas they could use to cook and provide heating.

If you appreciate the gravity of the situation – and completely ignore the obvious health and safety issues (and yes, there were a fair few explosions) – it was a solution worthy of the kind of innovative, yet practical, thinking in which Arup specialises.

However, it also demonstrates some of the practical issues that engineers have to think about when they consider what resilience really means in practice.

Key among these considerations is adaptability, such as finding simple and cost-effective ways to transfer between power sources, as shown in my Bosnian example.

Adaptability is fundamental to effective resilience in any design. Allowing for redundancies that cost little, yet can yield a great deal should they be needed.

A great example of an adaptable system is the diesel engine, which some people still seem amazed to find can run on biofuels made from used cooking oil, despite the fact that Rudolph Diesel was already using vegetable oil and peanut oil when he developed his engine in the late 19th century.

As David Singleton says in his excellent piece on resilience, the real challenge is to think creatively in terms of total systems, rather than sector-wide or specific systems.

If you get this right, you design in choices about what fails and when, which can provide a critical breathing space for taking mitigation measures or making rational choices about least-bad outcomes.

Of course, good design always has to balance resilience against cost as some redundancies can be horrifically expensive – or sometimes plain redundant. Having a spare car in case the first one breaks down is quite resilient, but it is expensive and redundant if the first car doesn’t work because the petrol stations have all been closed for a week.

However, getting away from cars for a minute and back to district heating where I started, it is easy to see that there are real merits in putting in the effort to think about balancing cost, resilience and innovation.

And if you really want to make it interesting, you can also add climate change and carbon reduction into the resilience mix.

Thinking about district heating in the context of whole system resilience throws up a real mix of issues that would challenge any of the big brains at Arup as you can see from touching on just a few of the variables:

  • district heating that can use a mix of energy sources is good on resilience... if you don’t lose too much efficiency
  • micro-generation from wind power is great... if the wind blows
  • waste-to-energy is brilliant... if the residents don’t object to the power plant
  • economies of scale favour big, single energy source power plants... but are poorer on resilience and depend on the distance from source to use
  • and a broad mix of traditional and renewable energy sources are perfect for supporting resilience... if the capital costs aren’t completely unsustainable.

That’s just a few top-line considerations off the top of my head. The list could be expanded greatly, but the key point is that balancing technology, cost, resilience and all the other trade-offs is what makes being an engineer so interesting. And the bigger you think, the more interesting it gets (especially in a war zone).

The great thing is that for every scenario in every sector across every geography, the solutions are likely to be quite different.

The fun part is figuring it all out – so if anyone wants to share good examples, we’d love to hear from you in the comments section below so we can put it out there for discussion.