Strategy vs Detail
How much detail should you put into strategy?
A few years ago an urban redevelopment project I was working on in the Middle East wanted to install district cooling (DC). The vendors insisted it would bring large energy and cost savings. They used equivalent full load hours, with a focus on the chillers, to demonstrate this. While it looked good at first blush, something seemed off.
Too much district cooling?
Equivalent Full Load Hours are the number of hours a system would need to operate at full load to use its annual energy consumption. At feasibility stage, when you don't have real-world data, it is calculated based on monthly averages, which is where it falls over. Chillers spend most of their time at part load, where COPs are much higher and where the gap between air cooled and water cooled chiller performance can narrow when it's humid. Part load is also when balance of system performance becomes comparatively more important.
So I analysed energy consumption hour-by-hour against the actual climate, included realistic load profiles, and factored in pumping energy, cooling tower performance and distribution losses for DC with and without thermal storage, against a range of water-cooled and air-cooled distributed systems. What I found was that, for most of the year in this instance, you could get comparable system-wide energy performance out of high efficiency air-cooled chillers without the water consumption (and the carbon footprint associated with desalination).
Based on this, I successfully made the case that dropping DC on this project reduced capex, lowered opex and freed up land.
I bring it up because I am currently reviewing another urban master plan project that is claiming DC as an energy-saving measure based purely on the assumption that it is.
Nor has thought apparently been given to the resilience of the wider development. DC presents a single point of failure that, if it coincides with life-threatening wet bulb temperatures, could lead to a public health catastrophe.
I'm not saying it's the wrong approach in this case, but I haven't yet seen anything to substantiate why it's the right approach.
The strategy part of urban development is not meant to be analysis-heavy, but without the fundamental understanding of how engineering systems work, it is all too easy to head down the wrong path. When something doesn't track, you need to go deeper, and challenge the received wisdom and rules of thumb. But you also need people who can see when something doesn't track.
Danu Consulting combines strategic approaches with technical knowledge to help you choose the right development pathway for optimised efficiency, resilience and regeneration. If you have something on your project that leaves you wondering, we'd love to talk.
