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Energy
MASSACHUSETTS
INSTITUTE OF
TECHNOLOGY
Futures
MIT
ENERGY
AUTUMN 2021
INITIATIVE
Using nature’s structures
in wooden buildings p. 5
Two-way trade in green electricity:
Canadian hydro and U.S. decarbonization p. 10
MIT Energy Initiative launches Future Energy
Systems Center p.3
Study provides suggestions for keeping
classroom air fresh during Covid-19 pandemic p. 24
Energy
Futures
Energy Futures is published twice yearly
by the MIT Energy Initiative. It reports
on research results and energy-related activities
across the Institute. To subscribe, please visit
energy.mit.edu/subscribe.
Copyright © 2021
Massachusetts Institute of Technology.
For permission to reproduce material
in this magazine, please contact the editor.
Nancy W. Stauffer, editor
stauffer@mit.edu
Kelley Travers, assistant editor
ktravers@mit.edu
Tom Melville, MITEI communications director
MIT Energy Initiative podcast thomasme@mit.edu
In our two most recent podcast episodes, we explore the energy transition with two prominent ISSN 1942-4671
leaders, one from the business world and one right here at MIT. Our podcast is currently on pause, (Online ISSN 1942-468X)
but you can explore all episodes at energy.mit.edu/podcast.
MIT Energy Initiative
Episode #40: Carbon and the cloud Episode #39: Starting from space
The MIT Energy Initiative is MIT’s hub for energy
Guest: Maud Texier, head of energy Guest: Maria Zuber, vice president for research, education, and outreach. Our mission is
development at Google research and E.A. Griswold Professor of to develop low- and no-carbon solutions that
Producer and host: Jenn Schlick, digital project Geophysics at MIT will efficiently meet global energy needs while
manager at MITEI Producer and host: Jenn Schlick, digital project minimizing environmental impacts and mitigating
manager at MITEI climate change.
We don’t often think about the energy we
consume and the carbon we emit into the Maria Zuber grew up in Pennsylvania coal
atmosphere when we are moving about the country, where both of her grandfathers worked
Internet. Maud Texier does think about these in the mines and suffered from black lung MIT Energy Initiative
things. She has led the teams responsible for disease. As a child she studied the stars and Massachusetts Institute of Technology
developing and scaling 24/7 carbon-free energy dreamed of outer space. Her career would take 77 Massachusetts Avenue, E19-307
for Google’s data centers around the world. her to a prominent position at NASA and later Cambridge, MA 02139-4307
We explore with her the carbon footprint of to MIT, where, in her portfolio of duties as vice
the Internet, the role of data centers, and how president for research, she leads the Institute’s 617-258-8891
Google and other organizations are working to efforts to help the planet achieve net-zero
make the Internet carbon-free. carbon emissions. In this podcast episode we For more information and the latest news
from MITEI, go to energy.mit.edu.
hear the story of her journey and of MIT’s
response to the climate crisis. You can read
excerpts of this episode on page 38.
Design: Ink Design, inc.
Copy editing: Kathryn M. O’Neill
On the cover Printing: Signature Printing
The construction industry is moving to use
sustainable timber in place of concrete and Printed on paper containing
steel. But when timber is harvested, irregular 30% post-consumer recycled content,
sections such as knots and forks are rejected. with the balance coming from responsibly
MIT researchers have developed methods managed sources.
that enable architects to quickly allocate a
pile of discarded forks among the Y-shaped
nodes in an architectural design and then
to cut and mark them to match up with
straight timbers, making assembly of the final
structure fast and easy. Read more on page 5.
Image: Wing Ngan, Ink Design, inc.
Autumn 2021
Massachusetts Institute
of Technology
5
mitei updates 22 Making the case for hydrogen perspectives
2 A letter from the director in a zero-carbon economy: 38 “Starting from space”: MITEI
Hydrogen-generated electricity podcast interviews MIT
3 MIT Energy Initiative for backing up wind and solar Vice President for Research
launches the Future Energy 24 MIT study provides suggestions Maria Zuber
Systems Center for keeping classroom air fresh
during Covid-19 pandemic
research reports
26 Coupling power and hydrogen
5 Using nature’s structures in sector pathways to benefit
wooden buildings: Tools for decarbonization goals
designing with forked tree
branches focus on faculty
10 New England renewables + 28 MITEI appoints Professor 40
Canadian hydropower: A Christopher Knittel as deputy
pathway to clean electricity director for policy
in 2050 40 3 Questions: Daniel Cohn on
29 Andy Sun announced as new the benefits of high-efficiency,
15 Chemical reactions for the
Iberdrola-Avangrid Professor flexible fuel engines for heavy-
energy transition: New insights
of Electric Power Systems at duty trucking
reveal pathways to improvement
MIT Sloan
42 3 Questions: Massachusetts
research news education Secretary of Energy and
18 MIT Energy Initiative awards Environmental Affairs
31 Francesco Benedetti: Building
seven Seed Fund grants for Kathleen Theoharides on
communities, founding a
early-stage energy research climate and energy
startup with people in mind
20 MIT-designed project 33 Latifah Hamzah ’12: Creating
achieves major advance members
sustainable solutions in
toward fusion energy Malaysia and beyond 44 Listing of MITEI members
MITEI’s role facilitating and affiliates
important research 35 Preparing global online learners
collaborations for the clean energy transition
report from cop26
36 Energy Studies Minor graduates,
June 2021 45 Robert Stoner: Home from
COP26—and optimistic
37 Energy Fellows, 2021–2022
20
MITEI Energy Futures | Autumn 2021 | 1
mitei updates
A letter from the director
Dear friends,
UN Secretary-General António Guterres Laboratory for Information and Deci-
struck us all when he called the Intergov- sions Systems, who has designed a new
ernmental Panel on Climate Change edX course: Principles of Modeling,
report “a code red for humanity.” Yet at Simulation, and Control for Electric
the MIT Energy Initiative we also see Energy Systems (page 35). It’s one of an
reason for hope. On our campus, there is expanding set of online courses MITEI
great progress being made toward the has funded to provide global learners with
energy transition. In Washington, a view of the shifting energy landscape.
Congress passed an infrastructure bill On page 24, read about two undergradu-
addressing climate change. And in ates funded by MITEI through the
Scotland this fall, thousands of world Undergraduate Research Opportunities
leaders—with some 20 MIT representa- Program who contributed to a timely
tives among them—gathered to address MIT study showing how classroom
MITEI’s research, education, and
climate change at COP26. configurations may affect air quality and
outreach programs are spearheaded by Professor
Robert C. Armstrong, director. contribute to the spread of Covid-19.
Earlier this year, the Institute published Photo: Kelley Travers, MITEI
“Fast Forward: MIT’s Climate Action We also share the stories of remarkable
Plan for the Decade,” addressing climate high-temperature superconducting MIT graduates. Latifah Hamzah ’12 has
change on campus and around the globe. electromagnet, breaking magnetic field co-founded a nonprofit to find sustain-
An element of the plan is MITEI’s Future strength records for a fusion magnet able and empowering solutions to help
Energy Systems Center, a research (page 20). You’ll read about the potential disadvantaged populations in Malaysia
consortium with industry launched this role and economic value of hydropower in (page 33). Former MIT visiting student
fall to explore how best to navigate the Quebec in a future low-carbon power and postdoc Francesco Benedetti led a
energy transition based on multi-sectorial system in New England (page 10); how team that won the 2021 MIT $100K
analyses of emerging technologies, architects are using discarded tree forks as Entrepreneurship Competition for the
changing policies, and evolving economics. load-bearing joints in their structures startup Osmoses, which has developed a
Read more on page 3. (page 5); and how a new fundamental novel way to separate molecules (page 31).
understanding developed by MIT
We recently completed our three-day chemists can help speed the conversion of We welcome some new leadership to
annual research conference with the biomass into useful fuels and chemicals MITEI. Christopher Knittel, the George
theme “Getting to net-zero by 2050.” (page 15). You can also read about two P. Shultz Professor of Energy Economics
We explored a number of opportunities hydrogen projects. One shows that at the MIT Sloan School of Management,
and challenges in reaching net-zero— hydrogen-fired power generation can be has become MITEI’s deputy director for
potential technology solutions; hydrogen a more economical option than lithium- policy (page 28). Also at Sloan, in January,
in the energy transition; the power grid ion batteries as a source of clean we’ll welcome Andy Sun of Georgia Tech
of the future; and thermal energy storage electricity (page 22); the other shows as the inaugural Iberdrola-Avangrid
and conversion. Also this fall, with hydrogen as a pathway for decarboniza- Professor of Electric Power Systems
partners at Stanford, Texas A&M, and tion in hard-to-abate sectors such as (page 29). At MITEI, Andy will serve as
the U.S. Department of Energy, we transportation, buildings, and industry a faculty lead for the electric power
sponsored our tenth annual U.S. C3E (page 26). And MITEI awarded seven system focus area at our new Future
Women in Clean Energy Symposium, Seed Fund grants to early-stage energy Energy Systems Center.
focusing on equity and justice in the clean research by faculty and researchers (page
energy transition (c3e.org/2021). 18). Since it began in 2008, the MITEI Hoping you enjoy Energy Futures and
Seed Fund Program has supported 193 wishing you restful holidays,
As always, Energy Futures offers a energy-focused seed projects through
rich taste of research at MITEI and grants totaling more than $26 million.
MIT. In September, MIT’s Plasma
Science and Fusion Center and MIT As always, education is central to our Professor Robert C. Armstrong
spinoff and MITEI member Common- mission. In this edition, we feature Marija MITEI Director
wealth Fusion Systems demonstrated a Ilic, a senior research scientist in MIT’s November 2021
2 | MITEI Energy Futures | Autumn 2021 | energy.mit.edu/energyfutures
mitei updates
MIT Energy Initiative launches the Future
Energy Systems Center
The MIT Energy Initiative (MITEI) has announced earlier this year to address the electric power systems, energy storage
launched a new research consortium—the climate crisis. and low-carbon fuels, and carbon
Future Energy Systems Center—to management.
address the climate crisis and the role The Future Energy Systems Center
energy systems can play in solving it. This investigates the emerging technology, “The Future Energy Systems Center
integrated effort engages researchers from policy, demographics, and economics marries MIT’s deep knowledge of energy
across all of MIT to help the global reshaping the landscape of energy supply science and technology with advanced
community reach its goal of net-zero and demand. The Center conducts tools for systems analysis to examine how
carbon emissions. The Center examines integrative analysis of the entire energy advances in technology and system
the accelerating energy transition and system—a holistic approach essential to economics may respond to various policy
collaborates with industrial leaders to understanding the cross-sectorial impact scenarios,” says MITEI Director Robert
reform the world’s energy systems. The of the energy transition. The Center C. Armstrong, the Chevron Professor of
Center is part of “Fast Forward: MIT’s encompasses energy-consuming Chemical Engineering. “We must act
Climate Action Plan for the Decade” sectors—transportation, industry, and quickly to get to net-zero greenhouse gas
(climate.mit.edu/climateaction/ buildings—and key energy system areas emissions. At the same time, we have a
fastforward), MIT’s multi-pronged effort essential to decarbonization, including billion people around the world with
Future Energy Systems Center Focus Areas
Image courtesy of MITEI
MITEI Energy Futures | Autumn 2021 | 3
inadequate access, or no access, to energy’s consumer and supplier Focus areas of the Future
electricity—and we need to deliver it sides—to gain insights to help
to them.” researchers anticipate challenges and Energy Systems Center
opportunities of deploying technology
The overarching focus of the Center is at the scale needed to achieve decar- Transportation. Within the transporta-
integrative analysis of the entire bonization. “The Future Energy tion sector, the Center will examine how
energy system, providing insights into Systems Center gives us a powerful electrification, low-carbon fuels,
the complex multi-sectorial transforma- way to engage with industry to charging/fueling infrastructure, urban
tions needed to alter the three major accelerate the energy transition,” says mobility systems, shared mobility trends,
energy-consuming sectors of the Armstrong. “Working together, we can new technology, policy, and other
economy—transportation, industry, better understand how our current solutions can contribute to the decar-
and buildings—in conjunction with technology toolbox can be more bonization of ground, water, and air
three major decarbonization-enabling effectively put to use now to reduce transportation.
technologies—electricity, energy storage emissions, and what new technologies
and low-carbon fuels, and carbon and policies will ultimately be needed Industry. The industrial sector includes
management. “These six areas overlap to reach net-zero.” production of all materials needed for
and interact with one another, making infrastructure, buildings, vehicles, energy
a systems approach essential,” says A steering committee, made up of 11 production, energy storage, agriculture,
Martha Broad, MITEI’s executive MIT professors and led by Armstrong, etc. Although this sector of the economy
director. “The Future Energy Systems selects projects to create a research is large and diverse, a dozen materials
Center seeks to eliminate silos in research, program with high impact on decar- constitute more than half of the
in technology, and in policy so that we bonization, while leveraging MIT greenhouse gas emissions from the
can work quickly and collaboratively with strengths and addressing interests of industry sector.
one another to address the existential Center members in pragmatic and
crisis of climate change.” scalable solutions. “MIT—through our Buildings. Buildings currently account
recently released Climate Action for about 30% of greenhouse gas
Through techno-economic and Plan—is committed to moving with emissions based on the embodied
systems-oriented research, the Center urgency and speed to transition away carbon from building materials and
analyzes important interactions among from economy-wide emissions of construction as well as emissions due to
these areas. For example: greenhouse gases to help resolve the operations including heating, cooling,
growing climate crisis,” says Armstrong. humidity control, and lighting.
• Greater electrification of transportation, “We have no time to waste.”
industry, and buildings will require Electric power. The electric power
expansion of demand management MITEI has historically engaged with system is a vital part of any decarboniza-
and other solutions for balancing of industry, including through its group of tion strategy. It is currently one of the
electricity supply and demand across Low-Carbon Energy Centers leading sectors for decarbonization and
these areas. (LCECs). All existing LCEC projects yet electric power supply must grow
and memberships continue, having multifold to meet demand from greater
• Likewise, balancing of supply and been integrated into the Future electrification of transportation, industry,
demand will also require deployment Energy Systems Center. The Center and buildings.
of grid-scale energy storage and members to date are: AECI, Chevron,
conversion of the electricity to ConocoPhillips, Copec, Dominion, Energy storage and low-carbon fuels.
low-carbon fuels (hydrogen and liquid Duke Energy, Enerjisa, Eneva, Eni, Balancing supply and demand also
fuels), which can in turn play a vital ENN, Equinor, Eversource, Exelon, requires large-scale deployment of a
role in the energy transition for ExxonMobil, Ferrovial, Golden Spread, range of energy storage solutions
hard-to-decarbonize segments of Iberdrola, IHI, National Grid, Rio including electrochemical storage,
transportation, industry, and buildings. Tinto, Shell, Toyota Research Institute, mechanical storage, thermal storage, and
and Washington Gas. chemical storage (low-carbon fuels).
• Carbon management will also play
a critical role in decarbonizing For more information about the Center, Carbon management. Carbon manage-
industry, electricity, and fuels both as please visit energy.mit.edu/ ment will also play a critical role in
a carbon-mitigation solution and futureenergysystemscenter. decarbonizing industry, electricity, and
as a negative-carbon technology. fuels. The scope within this focus area is
MIT Energy Initiative extensive and includes power generation,
As a member-supported research biomass conversion, production of
consortium, the Center collaborates with low-carbon fuels, carbon capture from
industrial experts and leaders—from both industry, utilization of carbon, carbon
storage, and carbon removal.
4 | MITEI Energy Futures | Autumn 2021 | energy.mit.edu/energyfutures
research reports
Using nature’s structures in wooden buildings:
Tools for designing with forked tree branches
Nancy W. Stauffer, MITEI
Concern about climate change has are the most emissions-intensive parts of
focused significant attention on the buildings due to their large volume of
buildings sector, in particular on the high-strength materials. Using upcycled
extraction and processing of construction materials in place of those high-carbon
materials. The concrete and steel indus- systems is therefore especially impactful
tries together are responsible for as much in reducing emissions.
as 15% of global carbon dioxide emissions.
In contrast, wood provides a natural form Mueller and her team focus on tree forks,
of carbon sequestration, so there’s a move that is, spots where the trunk or branch of
to use timber instead. Indeed, some a tree divides in two, forming a Y-shaped
countries are calling for public buildings piece. In architectural drawings, there are
in brief to be made at least partly from timber, many similar Y-shaped nodes where
and large-scale timber buildings have straight elements come together. In such
been appearing around the world. cases, those units must be strong enough
Forks in tree trunks and branches are
to support critical loads.
exceptionally strong, yet they are Observing those trends, Caitlin Mueller
rejected in timber construction because ’07, SM ’14, PhD ’14, an associate “Tree forks are naturally engineered
they are not straight. MIT researchers professor of architecture and civil and structural connections that work as
environmental engineering in the cantilevers in trees, which means that
have developed an approach that
Building Technology Program at MIT, they have the potential to transfer force
enables architects to use discarded tree sees an opportunity for further sustain- very efficiently thanks to their internal
forks as load-bearing joints in their ability gains. As the timber industry fiber structure,” says Mueller. “If you take
seeks to produce wooden replacements a tree fork and slice it down the middle,
structures. Using digital and computa-
for traditional concrete and steel you see an unbelievable network of fibers
tional methods, the MIT process elements, the focus is on harvesting the that are intertwining to create these often
distributes a collection of discarded straight sections of trees. Irregular three-dimensional load transfer points in
tree forks among the Y-shaped nodes sections such as knots and forks are a tree. We’re starting to do the same thing
turned into pellets and burned, or ground using 3D printing, but we’re nowhere
in an architectural design, allocating
up to make garden mulch, which will near what nature does in terms of
them so as to maximize the use of the decompose within a few years; both complex fiber orientation and geometry.”
inherent strength in the wood fiber— approaches release the carbon trapped in
the wood to the atmosphere. She and her team have developed a
and reallocating them instantly if the
five-step “design-to-fabrication workflow”
architect changes the design geometry. For the past four years, Mueller and her that combines natural structures such as
Computer-driven robotic machining Digital Structures research group have tree forks with the digital and computa-
adjusts and marks the forks for easy been developing a strategy for “upcycling” tional tools now used in architectural
those waste materials by using them in design. While there’s long been a “craft”
assembly with straight wooden elements. movement to use natural wood in railings
construction—not as cladding or finishes
Using recovered material from felled city aimed at improving appearance but as and decorative features, the use of
trees, the MIT team used this process to structural components. “The greatest computational tools makes it possible to
value you can give to a material is to give use wood in structural roles—without
create part of a wooden pavilion
it a load-bearing role in a structure,” she excessive cutting, which is costly and may
destined for installation at the site of says. But when builders use virgin compromise the natural geometry and
the felled trees. materials, those structural components internal grain structure of the wood.
MITEI Energy Futures | Autumn 2021 | 5
Above This photo shows some of the processed tree forks in the researchers’ an approach to sustainability that calls for “upcycling” such waste materials,
inventory. Their goal is to support the so-called circular economy of materials, in this case, by using them as structural joints in timber buildings.
Photo: Felix Amtsberg
Given the wide use of digital tools by School. Among the heavy equipment on produce isolated tree forks, some of which
today’s architects, Mueller believes that site was a chipper, poised to turn all the are shown in the photo above. They then
her approach is “at least potentially waste wood into mulch. Instead, the created a 3D scan of each fork. Mueller
scalable and potentially achievable workers obligingly put the waste wood notes that as a result of recent progress in
within our industrialized materials into the researchers’ truck to be brought photogrammetry (measuring objects
processing systems.” In addition, by to MIT. using photographs) and 3D scanning,
combining tree forks with digital design they could create high-resolution digital
tools, the novel approach can also support In their project, the MIT team sought representations of the individual tree
the trend among architects to explore not only to upcycle that waste material forks with relatively inexpensive equip-
new forms. “Many iconic buildings built but also to use it to create a structure that ment, even using apps that run on a
in the past two decades have unexpected would be valued by the public. “Where I typical smartphone.
shapes,” says Mueller. “Tree branches live, the city has had to take down a lot of
have a very specific geometry that trees due to damage from an invasive In the digital library, each fork is repre-
sometimes lends itself to an irregular or species of beetle,” Mueller explains. sented by a “skeletonized” version
nonstandard architectural form—driven “People get really upset—understandably. showing three straight bars coming
not by some arbitrary algorithm but by Trees are an important part of the urban together at a point. The relative geometry
the material itself.” fabric, providing shade and beauty.” She and orientation of the branches are of
and her team hoped to reduce that particular interest because they determine
Step 0: Find a source, set goals
animosity by “reinstalling the removed the internal fiber orientation that gives
Before starting their design-to-fabrication trees in the form of a new functional the component its strength.
process, the researchers needed to locate a structure that would re-create the
source of tree forks. Mueller found help atmosphere and spatial experience
Step 2: Find the best match between the
in the Urban Forestry Division of the previously provided by the felled trees.”
initial design and the material library
City of Somerville, Massachusetts, which
maintains a digital inventory of more With their source and goals identified, Like a tree, a typical architectural design
than 2,000 street trees—including more the researchers were ready to demonstrate is filled with Y-shaped nodes where three
than 20 species—and records information the five steps in their design-to- straight elements meet up to support a
about the location, approximate trunk fabrication workflow for making spatial critical load. The goal was therefore to
diameter, and condition of each tree. structures using an inventory of tree forks. match the tree forks in the material
library with the nodes in a sample
Step 1: Create a digital material library
With permission from the forestry architectural design.
division, the team was on hand in 2018 The first task was to turn their collection
when a large group of trees was cut down of tree forks into a digital library. They First, the researchers developed a
near the site of the new Somerville High began by cutting off excess material to “mismatch metric” for quantifying how
6 | MITEI Energy Futures | Autumn 2021 | energy.mit.edu/energyfutures
well the geometries of a particular tree increased—up to a point. In general, the each design includes a limited number
fork aligned with a given design node. researchers concluded that the mismatch of critical parameters, such as bar length
“We’re trying to line up the straight score was lowest, thus best, when there and bending strain. Using those parame-
elements in the structure with where the were about three times as many forks in ters, the designer can manually change
branches originally were in the tree,” the material library as there were nodes in the overall shape, or geometry, of the
explains Mueller. “That gives us the the target design. design or can use an algorithm that
optimal orientation for load transfer and automatically changes, or “morphs,” the
Step 3: Balance designer intention with
maximizes use of the inherent strength of geometry. And every time the design
structural performance
the wood fiber.” The poorer the alignment, geometry changes, the Hungarian
the higher the mismatch metric. The next step in the process was to algorithm recalculates the optimal
incorporate the intention or preference fork-to-node matching.
The goal was to get the best overall of the designer. To permit that flexibility,
distribution of all the tree forks
among the nodes in the target design.
Therefore, the researchers needed to try
different fork-to-node distributions
and, for each distribution, add up the
individual fork-to-node mismatch errors
to generate an overall, or global, matching
score. The distribution with the best
matching score would produce the most
structurally efficient use of the total tree
fork inventory.
Since performing that process manually
would take far too long to be practical,
they turned to the “Hungarian algorithm,”
a technique developed in 1955 for
solving such problems. “The brilliance
of the algorithm is solving that
[matching] problem very quickly,”
Mueller says. She notes that it’s a very
general-use algorithm. “It’s used for
things like marriage match-making. It
can be used any time you have two
collections of things that you’re trying to
find unique matches between. So, we
definitely didn’t invent the algorithm, but
we were the first to identify that it could
be used for this problem.”
The figure at the right presents a sample
structure design with three possible
distributions of the tree forks in the
researchers’ inventory. The forks colored
green are well matched with their nodes;
the strings in the design pass through the
centerline of the fork. The red forks are
less well matched. The top option
includes many red forks, so it has lots of
mismatches and a high global mismatch
score. The bottom option achieves the
most green forks and thus the lowest
mismatch score of the three options.
Repeated tests showed that the matching This figure shows three possible distributions of the researchers’ tree fork inventory within a target
architectural structure. The green-colored forks are well matched with their design node; the red forks
score improved as the number of forks are poorly matched. The global matching score of the bottom option is lower than those of the top and
available in the material library middle options. The bottom option thus makes better use of the available forks as load-bearing joints.
MITEI Energy Futures | Autumn 2021 | 7
At the Autodesk Boston Technology Center Build Space, a robotic arm interface well with its neighboring straight timbers, with marks and drill holes
automatically pushes a tree fork through a band saw in different orientations, for the structural connections, making assembly straightforward.
guided by computer-generated instructions. Ultimately, each tree fork will Photo: Felix Amtsberg
“Because the Hungarian algorithm is remaining bark to reduce susceptibility to computer-generated instructions. The
extremely fast, all the morphing and rot and fire. robot also mills all the holes for the
the design updating can be really fluid,” structural connections. “That’s helpful
notes Mueller. In addition, any change To guide that process, they developed a because it ensures that everything is
to a new geometry is followed by a custom algorithm that automatically aligned the way you expect it to be,”
structural analysis that checks the computes the cuts needed to make a given says Mueller.
deflections, strain energy, and other tree fork fit into its assigned node and to
Step 5: Assemble the available forks and
performance measures of the structure. strip off the bark. The goal is to remove as
linear elements to build the structure
On occasion, the automatically generated little material as possible but also to avoid
design that yields the best matching score a complex, time-consuming machining The final step is to assemble the structure.
may deviate far from the designer’s initial process. “If we make too few cuts, we’ll The tree-fork-based joints are all irregular,
intention. In such cases, an alternative cut off too much of the critical structural and combining them with the precut
solution can be found that satisfactorily material. But we don’t want to make a straight wooden elements could be
balances the design intention with a low million tiny cuts because it will take difficult. However, they’re all labeled. “All
matching score. forever,” Mueller explains. the information for the geometry is
embedded in the joint, so the assembly
Step 4: Automatically generate the
The photo above shows the setup they process is really low-tech,” says Mueller.
machine code for fast cutting
use to prepare their tree forks. The team “It’s like a child’s toy set. You just follow
When the structural geometry and uses facilities at the Autodesk Boston the instructions on the joints to put all
distribution of tree forks have been Technology Center Build Space, where the pieces together.”
finalized, it’s time to think about actually the robots are far larger than any at
building the structure. To simplify MIT and the processing is all automated. The top photograph on page 9 shows their
assembly and maintenance, the research- To prepare each tree fork, they mount final structure, which they installed
ers prepare the tree forks by recutting it on a robotic arm that pushes the temporarily on the MIT campus. Mueller
their end faces to better match adjoining joint through a traditional band saw notes that it was only a portion of the
straight timbers and cutting off any in different orientations, guided by structure they plan to build. “It had
8 | MITEI Energy Futures | Autumn 2021 | energy.mit.edu/energyfutures12 nodes that we designed and fabricated
using our process,” she says, adding that
the team’s work was “a little interrupted
by the pandemic.” As activity on campus
resumes, the researchers plan to finish
designing and building the complete
structure, which will include about 40
nodes and will be installed as an outdoor
pavilion on the site of the felled trees
in Somerville.
In addition, they will continue their
research. Plans include working with
larger material libraries, some with
multi-branch forks, and replacing
their 3D-scanning technique with
computerized tomography scanning
technologies that can automatically
generate a detailed geometric representa-
tion of a tree fork, including its precise
fiber orientation and density. And in a
parallel project, they’ve been exploring
using their process with other sources of
materials, with one case study focusing
on using material from a demolished The researchers produced and installed this structure on the MIT campus using waste tree forks as
structural elements. In the future, they plan to use their process to design and build a complete outdoor
wood-framed house to construct more pavilion, which will be located at the site of the felled trees from which the wood forks were recovered.
than a dozen geodesic domes. Photo: Felix Amtsberg
To Mueller, the work to date already
provides new guidance for the well am I using available resources?” she n ot e s
architectural design process. With digital says. “With the Hungarian algorithm, we
tools, it has become easy for architects to can compute that metric basically in real This research was supported by MIT’s School
analyze the embodied carbon or future time, so we can work rapidly and of Architecture and Planning via the HASS
Award. In summer 2021, MIT Facilities
energy use of a design option. “Now we creatively with that as another input to
removed some campus trees prior to
have a new metric of performance: How the design process.” construction and gave all the material to
Mueller and her team to use in their research
(see photo at left). Further information about
the research can be found in:
F. Amtsberg, Y. Huang, D.J.M. Marshall, K.M.
Gata, and C. Mueller. “Structural upcycling:
Matching digital and natural geometry.”
Advances in Architectural Geometry 2020,
April 2021. Online: bit.ly/structural-upcycling.
Y. Huang, L. Alkhayat, C. De Wolf, and C.
Mueller. “Algorithmic circular design with
reused structural elements: method and tool.”
Conceptual Design of Structures 2021, Interna-
tional fib Symposium, September 2021.
Online: bit.ly/circular-design-mueller, page 457.
In summer 2021, MIT Facilities took down a number of trees to make way for the new MIT Music
Building. Associate Professor Caitlin Mueller and her team received the material shown above to further
their research on the use of salvaged materials in architecture. Photo: Neil Patel of Lee Kennedy Co.
MITEI Energy Futures | Autumn 2021 | 9research reports
New England renewables + Canadian hydropower:
A pathway to clean electricity in 2050
Nancy W. Stauffer, MITEI
in brief
In general, the options being discussed low-carbon system in New England.
In planning for a carbon-free electric include nuclear power, natural gas with Their goal was to help inform policy
power system in 2050, U.S. states in carbon capture and storage (CCS), and makers, utility decision makers, and
New England have looked to hydropower energy storage technologies such as new others about how best to incorporate
imported from Quebec as one source of and improved batteries and chemical Canadian hydropower into their plans
clean electricity alongside wind and solar storage in the form of hydrogen. But in and to determine how much time and
the northeastern United States, there is money New England should spend to
and others. But engaging Canadian
one more possibility being proposed: integrate more hydropower into its
hydropower strictly as an electricity electricity imported from hydropower system. What they found out was
supplier may not be the best way to go. plants in the neighboring Canadian surprising, even to them.
An MIT analysis shows that two-way province of Quebec.
exchanges between the regions could The analytical methods
The proposition makes sense. Those plants
yield significant benefits. Under such an
can produce as much electricity as about To explore possible roles for Canadian
arrangement, Quebec sends electricity 40 large nuclear power plants, and some hydropower to play in New England’s
south to New England to meet demand power generated in Quebec already power system, the MIT researchers first
when wind and solar aren’t producing comes to the Northeast. So, there could needed to predict how the regional power
enough power. When they produce an be abundant additional supply to fill any system might look in 2050—both the
excess, New England sends electricity shortfall when New England’s intermit- resources in place and how they would be
tent renewables underproduce. However, operated, given any policy constraints. To
north to cover demand in Quebec,
U.S. wind and solar investors view perform that analysis, they used GenX, a
allowing the hydro systems to pause and Canadian hydropower as a competitor modeling tool originally developed by
reservoirs to refill with water. The hydro and argue that reliance on foreign supply Jesse Jenkins SM ’14, PhD ’18 and Nestor
system thus provides energy storage— discourages further U.S. investment. Sepulveda SM ’16, PhD ’20 while they
over hours or days or months—and both were researchers at the MIT Energy
Two years ago, three researchers affiliated Initiative (MITEI).
regions benefit: Two-way trading lowers
with the MIT Center for Energy and
the cost of decarbonization and acceler- Environmental Policy Research The GenX model is designed to support
ates the process. Based on their findings, (CEEPR)—Emil Dimanchev SM ’18, decision-making related to power system
the researchers suggest that such now a PhD candidate at the Norwegian investment and real-time operation
interregional cooperation could prove University of Science and Technology; and to examine the impacts of possible
beneficial wherever hydropower Joshua Hodge, CEEPR’s executive policy initiatives on those decisions.
director; and John Parsons, a senior Given information on current and
resources are available.
lecturer in the MIT Sloan School of future technologies—different kinds of
Management—began wondering whether power plants, energy storage technologies,
The urgent need to cut carbon viewing Canadian hydro as another and so on—GenX calculates the combi-
emissions has prompted a growing source of electricity might be too narrow. nation of equipment and operating
number of U.S. states to commit to “Hydropower is a more-than-hundred- conditions that can meet a defined future
achieving 100% clean electricity by year-old technology, and plants are demand at the lowest cost. The GenX
2040 or 2050. But figuring out how to already built up north,” says Dimanchev. modeling tool can also incorporate
meet those commitments and still have “We might not need to build something specified policy constraints, such as limits
a reliable and affordable power system new. We might just need to use those on carbon emissions.
is a challenge. Wind and solar installa- plants differently or to a greater extent.”
tions will form the backbone of a For their study, Dimanchev, Hodge, and
carbon-free power system, but what So the researchers decided to examine the Parsons set parameters in the GenX
technologies can meet electricity demand potential role and economic value of model using data and assumptions
when those intermittent renewable Quebec’s hydropower resource in a future derived from a variety of sources to build
sources are not adequate?
10 | MITEI Energy Futures | Autumn 2021 | energy.mit.edu/energyfutures8,000
6,000
(positive denotes north-to-south flow)
4,000
Transmission flows
2,000 Historical
(MW)
0
90% decarbonization
and current
transmission capacity
-2,000
-4,000
-6,000
90% decarbonization and
new transmission capacity
-8,000
0 1,752 3,504 5,256 7,008 8,760
Hours per year
Effects of transmission infrastructure change on flow of electricity New England and are capped by the transmission capacity limit of
between New England and Quebec 2,225 megawatts (MW). Model results for 2050 are shown in brown
This figure shows the level of electricity flow from north to south (positive and purple and assume current and expanded transmission capacity,
numbers) and from south to north (negative numbers) versus the number of respectively. In both cases, flow is at the maximum in both directions for
hours per year. The flows in 2018, shown in blue, are always from Quebec to many hours of the year.
a representation of the interconnected requires adhering to certain operating emissions between 80% and 100%
power systems in New England, New constraints. For example, to prevent relative to 1990 levels. The results of those
York, and Quebec. (They included New flooding, reservoirs must not be allowed runs show that, as emissions limits get
York to account for that state’s existing to overfill—especially prior to spring more stringent, New England uses more
demand on the Canadian hydro snowmelt. And generation can’t be wind and solar and extends the lifetime
resources.) For data on the available increased too quickly because a sudden of its existing nuclear plants. To balance
hydropower, they turned to Hydro- flood of water could erode the river edges the intermittency of the renewables, the
Québec, the public utility that owns and or disrupt fishing or water quality. region uses natural gas plants, demand-
operates most of the hydropower plants side management, battery storage
in Quebec. Based on projections from the National (modeled as lithium-ion batteries),
Renewable Energy Laboratory and and trading with Quebec’s hydropower-
It’s standard in such analyses to include elsewhere, the researchers specified based system. Meanwhile, the optimal
real-world engineering constraints on electricity demand for every hour of the mix in Quebec is mostly composed of
equipment, such as how quickly certain year 2050, and the model calculated the existing hydro generation. Some solar is
power plants can be ramped up and down. cost-optimal mix of technologies and added, but new reservoirs are built only
With help from Hydro-Québec, the system operating regime that would if renewable costs are assumed to be
researchers also put hour-to-hour satisfy that hourly demand, including the very high.
operating constraints on the hydropower dispatch of the Hydro-Québec hydro-
resource. power system. In addition, the model The most significant—and perhaps
determined how electricity would be surprising—outcome is that in all the
Most of Hydro-Québec’s plants are traded among New England, New York, scenarios, the hydropower-based system
“reservoir hydropower” systems. In them, and Quebec. of Quebec is not only an exporter but also
when power isn’t needed, the flow on a an importer of electricity, with the
river is restrained by a dam downstream direction of flow on the Quebec-New
Effects of decarbonization limits on
of a reservoir, and the reservoir fills up. England transmission lines changing
technology mix and electricity trading
When power is needed, the dam is over time.
opened, and the water in the reservoir To examine the impact of the
runs through downstream pipes, turning emissions-reduction mandates in the The figure on this page shows transmis-
turbines and generating electricity. New England states, the researchers ran sion flows north and south. Historically,
Proper management of such a system the model assuming reductions in carbon energy has always flowed from Quebec to
MITEI Energy Futures | Autumn 2021 | 11New England, as shown by the blue curve, The purple line in the figure on page 11 are roughly the same, but now there
which represents 2018. That curve shows the impact of expanding transmis- are imports as well. Thus, two-way
remains above the zero line, indicating sion capacity from 2,225 MW to 6,225 trading reallocates renewables from
that the flow is always north to south, and MW: Flows in both directions are greater, Quebec to New England, where it’s
it’s capped by the current transmission and in both cases the flow is at the new more economical to install and operate
capacity limit of 2,225 megawatts (MW). maximum for more than 1,000 hours. solar and wind systems.
The brown curve shows the model results Results of the analysis thus confirm The right-hand bars in the two panels
for 2050, assuming that New England that the economic response to expanded show the energy mix in New England
decarbonizes 90% and the capacity of the transmission capacity is more two-way and Quebec assuming two-way trading
transmission lines remains the same. Now trading. To continue the battery analogy, with expanded transmission capacity.
the flows go both ways. Looking at the more transmission capacity to and Comparing the middle and right-hand
right-hand side of the figure, there are from Quebec effectively increases the bars in the New England panel shows
nearly 3,500 hours where the curve is rate at which the battery can be charged that expanded transmission allows
below the zero line, so electricity is and discharged. wind, solar, and nuclear to expand
flowing from New England to Quebec. further; natural gas with CCS all but
As the flat section shows, for more than disappears; and both imports and
Effects of two-way trading on the
2,200 hours, the flow going north is at exports increase significantly. In the
energy mix
the maximum the transmission lines Quebec panel, solar decreases still
can carry. What impact would the advent of further, and both exports and imports
two-way trading have on the mix of of electricity increase.
The direction of flow is motivated by energy-generating sources in New
economics. When renewable generation England and Quebec in 2050? Those results assume that the New
is abundant in New England, prices are England power system decarbonizes by
low, and it’s cheaper for Quebec to import The figure on page 13 shows the energy 99% in 2050 relative to 1990 levels. But at
electricity from New England and mix in the two regions, with the panel on 90% and even 80% decarbonization levels,
conserve water in its reservoirs. Con- the left representing New England, and the model concludes that natural gas
versely, when New England’s renewables the panel on the right, Quebec. Here, the capacity decreases with the addition of
are scarce and prices are high, New researchers have included a second kind new transmission relative to the current
England imports hydro-generated of hydro plant—“run of river” (ROR), in transmission scenario. Existing plants are
electricity from Quebec. which whatever water is available on a retired, and new plants are not built as
river simply flows through a turbine and they are no longer economically justified.
So rather than delivering electricity, generates electricity. In Quebec, ROR Since natural gas plants are the only
Canadian hydro provides a means of plants are considered part of the overall source of carbon emissions in the 2050
storing the electricity generated by the reservoir system because they are situated energy system, the researchers conclude
intermittent renewables in New England. downstream of reservoirs, and their that the greater access to hydro reservoirs
output is thus partly controlled by made possible by expanded transmission
“We see this in our modeling because decisions at those reservoirs. would accelerate the decarbonization of
when we tell the model to meet electricity the electricity system.
demand using these resources, the model In each panel, moving from the left to the
decides that it is cost-optimal to use the center bar shows the impact of moving
Effects of transmission changes
reservoirs to store energy rather than from traditional one-way trading to
on costs
anything else,” says Dimanchev. “We two-way trading. In New England, that
should be sending the energy back and change increases both wind (dark blue) The researchers also explored how
forth, so the reservoirs in Quebec are in and solar (yellow) power generation and two-way trading with expanded transmis-
essence a battery that we use to store to a lesser extent nuclear (orange); it also sion capacity would affect costs in New
some of the electricity produced by our decreases the use of natural gas with CCS England and Quebec. The figure on
intermittent renewables and discharge it (navy blue). The hydro reservoirs in page 14 summarizes their findings
when we need it.” Canada can provide long-duration (assuming 99% decarbonization in New
storage—over weeks, months, and even England). The blue bar shows cost savings
Given that outcome, the researchers seasons—so there is less need for natural in the two regions, divided into fixed
decided to explore the impact of expand- gas with CCS to cover any gaps in supply. costs (investments in new equipment)
ing the transmission capacity between The level of imports (green) is slightly and variable costs (operating costs). New
New England and Quebec. Building lower, but now there are also exports England’s savings on fixed costs are
transmission lines is always contentious, (purple). Meanwhile, in Quebec, two-way largely due to a decreased need to invest
but what would be the impact if it could trading reduces solar power generation, in more natural gas with CCS, and its
be done? and the use of wind disappears. Exports savings on variable costs are due to
12 | MITEI Energy Futures | Autumn 2021 | energy.mit.edu/energyfuturesa reduced need to run those plants. the decarbonization target tightens. Addressing misconceptions
Quebec’s savings on fixed costs come At 99% decarbonization, the overall
These results shed light on several
from a reduced need to invest in solar New England-Quebec region pays about
misconceptions that policy makers,
generation. The increase in cost (orange $21 per megawatt-hour (MWh) of
supporters of renewable energy, and
bar)—borne by New England—reflects electricity with today’s transmission
others tend to have.
the construction and operation of the capacity but only $18/MWh with
increased transmission capacity. The net expanded transmission. Assuming 100%
The first misconception is that the New
benefit for the region (green bar) is reduction in carbon emissions, the region
England renewables and Canadian
substantial. pays $29/MWh with current transmis-
hydropower are competitors. The
sion capacity and only $22/MWh with
modeling results instead show that they’re
Thus, the analysis shows that everyone expanded transmission.
complementary. When the power systems
wins as transmission capacity
increases—and the benefit grows as
New England Quebec
250
150
200
100 150
Energy mix (TWh)
100
50
50
0
0
-50 -50
Current Current New Current Current New
transmission, transmission, transmission, transmission, transmission, transmission,
import only two-way trading two-way trading import only two-way trading two-way trading
Imports Existing ROR hydro Gas Existing reservoir hydro
Solar Gas with CCS Existing nuclear Exports
Wind
Energy mix in New England (left) and Quebec (right) under varied current capacity and two-way flows; and the right-hand bar assumes
assumptions about transmission capacity and operation expanded capacity and two-way flows. In Quebec, run-of-river (ROR)
This figure shows the impact on the energy mix in 2050 of expanding plants typically occur downstream of reservoirs, so their output is not
transmission capacity and operating transmission in an economically reported separately. All cases assume that New England’s electricity is
optimal manner. In each panel, the left-hand bar shows results assuming 99% decarbonized.
current transmission capacity and one-way flow; the center bar assumes
MITEI Energy Futures | Autumn 2021 | 13in New England and Quebec work hydro can provide storage, specifically for
n ot e s
together as an integrated system, the wind and solar. It’s a solution to the
Canadian reservoirs are used part of the intermittency problem that we foresee in This research was funded by the MIT Center
time to store the renewable electricity. carbon-free power systems for 2050.” for Energy and Environmental Policy Research
And with more access to hydropower (ceepr.mit.edu), which is supported in part
storage in Quebec, there’s generally more While the MIT analysis focuses on by a consortium of industry and government
renewable investment in New England. New England and Quebec, the research- associates. The GenX modeling tool is
ers believe that their results may have now being maintained jointly by teams of
The second misconception arises when wider implications. As power systems in contributors at the MIT Energy Initiative,
led by research scientist Dharik Mallapragada,
policy makers refer to Canadian hydro many regions expand production of
and the Princeton University ZERO Lab, led
as a “baseload resource,” which implies renewables, the value of storage grows. by Assistant Professor Jesse Jenkins SM ’14,
a dependable source of electricity— Some hydropower systems have storage PhD ’18. More information about this research
particularly one that supplies power all capacity that has not yet been fully can be found in:
the time. “Our study shows that by utilized and could be a good complement
viewing Canadian hydropower as a to renewable generation. Taking advan- E.G. Dimanchev, J.L. Hodge, and J.E. Parsons.
baseload source of electricity—or indeed tage of that capacity can lower the cost of “The role of hydropower reservoirs in
a source of electricity at all—you’re not deep decarbonization and help move deep decarbonization policy.” Energy Policy,
May 2021. Online: doi.org/10.1016/
taking full advantage of what that some regions toward a decarbonized
j.enpol.2021.112369.
resource can provide,” says Dimanchev. supply of electricity.
“What we show is that Quebec’s reservoir E.G. Dimanchev, J.L. Hodge, and J.E. Parsons.
Two-Way Trade in Green Electrons: Deep
Decarbonization of the Northeastern U.S. and the
Role of Canadian Hydropower. CEEPR working
paper WP-2020-003, February 2020. Online:
ceepr.mit.edu/publications/working-papers.
3
2
$/MWh
1
0
Benefits Costs Net benefits
Saving on fixed costs (New England) Transmission cost
Saving on variable costs (New England) Net benefit of transmission
Saving on fixed costs (Quebec)
Effects of two-way trading and expanded transmission on the cost of added transmission lines. The green bar at the right represents the net
electricity in New England and Quebec benefit of two-way trading and expanded transmission to the New
The blue bar at the left shows savings in 2050 from implementing two-way England-Quebec region. This analysis assumes 99% decarbonization in
trading and expanding transmission capacity. The orange bar in the center New England.
shows the additional cost to New England of building and operating the
14 | MITEI Energy Futures | Autumn 2021 | energy.mit.edu/energyfuturesYou can also read
