Early each year, several things appear in Iceland as harbingers of Spring, such as the Loa. Iceland School of Energy students and their renewable energy compatriots worldwide clamber out of their coursework like groundhogs in wider search of advisors and appropriate thesis topics. How do they find them? It’s possible one might see one’s thesis topic candidates or career arc options in the swirling tendrils of a Sankey diagram, such as the Super Sankey diagram for the U.S. shown (partially) above. These energy diagrams can bring some order to chaos and help communicate priorities on a national, community/complex or individual level. What needs decarbonization attention? How can find a suitable prospect? You and everyone joining in on the Grand Alliance fighting climate change are in there somewhere. Let’s take a look at how thinking about problems using these diagrams might help you find and put your potential contributions in context.
Super Sankey – National Level
For those not familiar with Sankey diagrams, they show graphically the various flows of energy produced and consumed in a given setting. This particular Super Sankey shows flows for the U.S. Please open the hyperlink to view all its tangled mastery in the widest detail, rather than just the small image clip. This article describes how the data were compiled, makes observations about how much energy each sector consumes, and outlines how various decarbonization strategies for this country might play out. As the article states, it is convenient that the U.S. uses about 100 quads of energy per year, so consumption in quads is similar to the percentage of the total.
We can see the major fossil fuel production streams to the top left (natural gas, petroleum, coal) and then nuclear and renewable energy below. This diagram does not show the carbon intensity of the different sources, but clearly the 17.62 quads/year consumption of coal is one of the priority streams to decarbonize.
Where is your favorite energy source on this chart? Mine’s geothermal, contributing a whopping 0.37 quads of primary energy. Ok, so small at this point in the U.S., and not growing as fast as the solar or wind sectors, but every bit helps. Other countries have far higher proportions, to their credit. Perhaps you are interested in the “supply side”, developing innovative geothermal, wind, solar, hydro or other clean energy plants?
Streams flow from left to right as energy sources are diverted to different demands. If we click on “produced and distributed geothermal” we can see the various commercial, residential or industrial uses that it might be put to, displacing more carbon-intensive fuels.
Are you interested more in conserving or reconfiguring the “demand side” rather than working on the supply side? Waaaaayyyy over to the right we can see 0.02 quads of energy used annually for greenhouses and nurseries, and another 0.02 for aquaculture or other. We like our geothermal greenhouses and aquaculture in Iceland and Idaho. Not national game changers in the U.S. yet perhaps but worthwhile paths of study for communities.
Paths to solutions begin with identification and quantification. From a national policy perspective in the U.S., transitioning our electrical generation portfolio (38.5 quads) and transportation sectors (27.65 quads) to a lower carbon future are clearly the top priorities, and working on policies or technologies for those would be the most impactful. Reducing/decarbonizing hog and pig farming energy consumption (0.02 quads), less so. Stunning levels of detail in this chart, eh?
For a thesis topic you may be motivated to find a project that is impactful, sure, but more importantly is a fit for your country, talents and purpose. Scanning a Sankey diagram like this and considering how your background and potential next career path(s) might map into one or several of these streams might help you identify some good topic candidates.
Scanning this as a trial, hmm, well my origin and foresty state of Wisconsin has a lot of paper production. U.S. manufacturing consumes a lot of process energy (4.48 quads), and I like process thermodynamics. For me, working with a local mill or Forest Products Lab to identify creative ways to economize or decarbonize their facilities might be a productive thesis topic. Your country or region is going to have its own Sankey diagram, or could, and maps like these can help to see where your efforts may align.
Community Level
By community here we mean a city, town, or collection of them in a small region that is interested in mapping out a managed energy transition to the future. Could even be a large industrial complex that consumes a mixture of fuels and electricity and/or has a variety of products, with the same transition goal. In the U.S. much of the impetus for a move to clean energy comes not from the national government but from grassroots, community-based organizations or businesses.
Cities such as scenic Burlington, Vermont have defined a path and succeeded in getting 100% of their electrical demand provided by renewable energy. If we could see their Sankey diagram we could understand better their solutions and how much further they have to go in terms of transforming other energy consumption patterns (transportation fuels e.g.) over to cleaner sources.
Having such a diagram available would make conversations about prioritization and technology options easier. As a member of a Climate Action Coalition for my community I wish we had this kind of data readily on hand. Where should our own communities’ efforts be best directed? Is electrifying buses a lower or higher value project? Is electrifying home heating a high priority/best path to move away from natural gas? Is there ample market opportunity to introduce other options such as solar thermal, geothermal heat pumps or geothermal direct use?
A Sankey diagram also gives us a clue to who the major stakeholders for developing a clean energy transition plan would be. For our little mountain valley it was quite a long list: community leaders, local utilities, large businesses, school district, faith organizations, agricultural organizations, other environmental and social justice NGOs, etc.
Developing the U.S. Super Sankey was clearly a massive effort, but it would seem developing even rudimentary Sankey diagrams for your region of interest would be a worthwhile goal to plot out transition strategies. When we look at the Energy Future plan for our neighboring hamlet of Boise, it has some simple pie charts (sample following), but these do not capture energy flows such as transportation, or have the granularity that people could find more insightful. If I were a student at Boise State University, having a community Sankey would help one pick out preferred projects with greater clarity.
Which brings us to an interesting quote, forgot the source:
“That which obstructs your project, IS the project.”
If a lack of clarity on energy production and consumption impedes you from finding preferred solutions, then collecting data and building a Sankey diagram might make a good first step for a project.
Individual Level
If motivated, you could think of Sankey diagrams even on an individual level as a way to scope out supplies and demands. I have a small camper van for boondocking, liking to stay out for days without access to shore power but wanting to run some amenities like electronics, refrigerator and lights. There are other thermal demands such as cooking and space heating that can be accommodated with electricity, solar, propane…or warm blankets. How much is needed? When?
Depending on solar or other fuel availability, battery state of charge, time and weather, I mix and match what I can to satisfy demands. At the same time I’m trying to simplify and decarbonize consumption, thinking of ways to use less or no fuel. Visualizing items using a Sankey (or admittedly, just a table) helps size gear, plan recharging or eating strategies, defer consumption or substitute sources.
As a micro example, consider heating water for tea. One can make 0.5 L of tea-grade water in about:
- 10 minutes consuming 50 Wh. I use a 300 W AC immersion heater.
- <1 hour using a 12V electric kettle while driving.
- 1 hour using a portable solar oven (also makes good frittatas).
- <5 minutes using a 5000 Btu/h (~1500 W equivalent) propane stove. There clearly is a ton of thermal energy that goes to places other than creating hot water (air, vapor).
The end product (right side of the Sankey diagram) is the same: a Contigo full of tea-grade hot water. Depending on your energy situation (batteries charged/not charged, sun out/not, in a hurry/not, driving/not) one can rearrange the sources appropriately (left arrows) to conserve fuel or time. You’re out there to relax anyway, what’s the hurry?
An individual Sankey perspective makes sense for home capital investments as well. Our Idaho Power grid has a large share of electricity from hydro, a bit of geothermal, increasingly economical wind and solar and a small dwindling share of coal. When my home was built it came with a mix of electrical and natural gas appliances, now some 15+ years old. Looking forward to a decarbonized future, my plan is to electrify the gas users (stove, water heater, boiler) as they need replacement in the near future. This would give the home a very “Simple Sankey,” and avoid being stuck with new gas appliances and larger bills as the customer base dwindles over the next decades. I’d also be able to leverage some backup solar/storage options in case the grid goes down entirely.
Find ways to cut off the heads of Sankey Snake carbon-intensive energy flows and replace them with something cleaner and more effective.
Sankey Summary
As engineers you can see the math, understand the options, and make choices to use resources wisely. Those choices and the magnitude of the impacts may not be as evident to non-engineers. Data visualization techniques can help us communicate effectively.
Seeing a nation or community’s energy usage “top-down” using a Sankey diagram helps identify priorities. Working out your energy streams at an individual “bottom-up” level can then help you appreciate your personal options and better understand the challenges we will need to make the transition at the community or national level. Combine both perspectives, and consider if Sankey diagrams would be useful tools for you to identify projects worthy of your effort.
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