Chapter 4: Dr. Strange Data or, How I Learned to Stop Worrying and Love the Hourly Emissions

Memoirs of an hourly emissions modeler: a six-part series by Karina Hershberg

As we saw in the Chapter 3 Northwest region comparison table, the annual average of the LRMER hourly emissions sets aren’t all that different from the single annual average emissions as reported by the utility or eGrid. All of this brings us to the fundamental question – does hourly building emissions modeling actually tell us anything new?

If efficiency, electrification, flexible loads, onsite renewables, and grid-adaptive systems are the answer, is there value in going through the steps knowing where the road will lead?

My biased opinion as a modeler is – yes, of course! But even my unbiased opinion simply as someone working in the green building world is still yes. I’m continually surprised by what I learn by going through the steps. When my colleague Forest Tanier-Gesner and I started adding the dimension of time to operating emissions modeling, we had no idea what we’d see the closer we started looking. Hourly emissions modeling might not alter the end result – efficient grid-adaptive electrification with renewables – but it adds depth to our understanding of how buildings can accelerate decarbonization of the larger energy sector, not just tag along.

Yet I propose this perhaps provocative thought – the greatest value of hourly emissions modeling is less about quantifying operating emissions with an exact number and more about designing better grid-adaptive buildings. Although we are constantly gaining a better understanding, hourly emission models are not precise. We don’t know to high precision what’s happening on the grids today or the future (Cambium documentation has a whole page on the limits of its accuracy!).

Yet modeling with hourly emissions helps us understand the levers we have to decrease operating emissions- which of those levers will have the most impact and how we might best use them. It provides insight in how we can design our buildings to reduce grid-dependance during times of peak emissions and turn buildings into grid-resources instead of just grid-users. Most regions don’t have access to real-time grid emissions signals yet so in many ways we are trying to design buildings that can dynamically participate in a future that doesn’t exist yet- but is most certainly coming.

I’ll offer up an example for a recent study we did for Portland General Electric (the PGE without the “&”). PGE was interested in the potential for centralized hot water systems in multifamily housing to be a flexible load resource – essentially a thermal battery. The question was how much a project would need to oversize the tank so it could be used as a meaningful peak time flexible load without occupants knowing anything had happened.

By using hourly emissions, we were able to identify when, how often, and by how much we’d need the heat pumps to shut off to avoid times of peak emissions. This information allowed us to estimate the increased tank size that would be necessary to support that operating schedule without the system running out of hot water. The result was that with a reasonable increase in tank size, the system could be used as a beneficial flexible resource for PGE with beneficial economic incentives for the building owner and no impact on the occupants.

Without the benefit of an hourly emissions analysis, we would have struggled to confirm this opportunity beyond a theoretical “It’ll probably work….” The design best-practice is to right-size tanks as much as possible, so oversizing it for a hunch could be hard to justify. The total energy use impact was minimal so an annual average total wouldn’t have shown much of interest.

The easier solution to reduce peaks is add a battery to the project, but this brings cost, space, and embodied emissions implications - it isn’t a zero-sum game. In this case, the benefit of the hourly emissions analysis wasn’t an exact number for operating emissions, but a way to inform a design decision that might not have otherwise been made.

But can we come to these same conclusions through other approaches?

Quick note about batteries-
The easiest solution to reduce peaks is add a battery to the project, which is often the option I see our industry reaching for. Onsite storage is certainly one of the tools available to us in the energy decarbonization toolbox, but remember that with it comes cost, space, and embodied emissions implications - it isn’t a zero-sum game. On the other hand, the unique advantage of batteries is they also open up the potential for energy resiliency, an increasingly crucial need. I’d love to see our industry use all the tools in the toolbox for decarbonization, not just batteries, and when batteries are used to make sure they’ve been given the added purpose of resiliency.

Up next- Wearing nice glasses and designing beautiful spaces

Also published on LinkedIn by Karina Hershberg

Chapter 1: Not All That Glitters is Zero Carbon
Chapter 2: The Emissions Multiverse
Chapter 3: With Great Power Comes Great Responsibility
Chapter 4: Dr Strange Data, or, How I Learned to Stop Worrying and Love the Hourly Emissions
Chapter 5: Wear Nice Glasses and Design Beautiful Spaces
Chapter 6: No One is Net Zero Until Everyone is Net Zero