Power April 2022 Intl - 36

MICROGRID
Microgrids with Propane-Fueled
Backup Systems Deliver Reliable,
Resilient Power
With the increased value of distributed capacity in various energy markets, there
is a growing demand for generators in microgrids, which are local energy systems
that can be disconnected from the electric grid. Propane-powered generators will
continue to be an important part of the solution and a focus of ongoing policy discussions.
Gordon
Feller
W
henever extreme weather events
pound the U.S. (including hurricanes
and fires), utility safety
shutdown programs ramp up. These safety-driven
power shutoffs are pushing commercial
and industrial energy consumers
to seek solutions that not only meet corporate
sustainability objectives, but also
provide a greater measure of resiliency.
The U.S. Department of Energy's
Energy Information Administration published
an important piece of research in
2020, which carries this headline: " More
than 60% of energy used for electricity
generation is lost in conversion. " One
primary reason for the shift to cleaner
fuels for utility purposes is to gain important
energy efficiencies. According
to the study, " in 2019, of the 11.9 quads
of natural gas consumed for electricity
generation, natural gas plants converted
45% (5.4 quads) into net generation of
electricity. By contrast, of the 10.2 quads
of coal consumption, coal plants converted
32% (3.3 quads) into net generation. "
Benefits of Propane Over Natural Gas
Natural gas and propane are more energy
efficient than coal, and cleaner. Dr.
Christopher Baird, assistant professor of
physics at West Texas A&M University,
published an article several years ago
answering a simple question: Why is
propane stored in household tanks but
natural gas is not? The reason, he wrote,
is that propane has a much higher boiling
point (-44F at atmospheric pressure)
than natural gas, or methane, (-260F at
atmospheric pressure). That means a
much lower pressure is required to keep
propane in a liquid state at room temperature
(70F) than is required to keep
methane in a liquid state (about 123 psi
versus 4,641 psi, respectively). There36
fore,
a common household metal tank
can withstand the pressure required for
propane, but not for methane.
Propane storage offers at least three advantages
for power companies. They are:
■ In winter storms, such as Uri in 2021,
propane can be stockpiled next to a
power generation plant.
■ Because propane can be stockpiled, purchasing
it can be done when supplies are
high and costs are lower-it's a hedge.
■ " Peak shaving " with propane makes
sense. Stored propane is effectively
a battery that can be turned on when
the price of other fuels peaks or the
load on the grid peaks.
Microgrids Enhance Resiliency
As an increasingly viable option for
the future, microgrids have gained in
prominence as utility services have become
more fragile in the face of climate
change. Furthermore, some independent
system operators and regional transmission
organizations, such as the Electric
Reliability Council of Texas (ERCOT),
have shown that they can't be entirely
expected to successfully manage their
grids. In this kind of a world, it makes
sense to decentralize the grid so that it
can be run more efficiently, and more
safely, using an array of energy sources.
Microgrids are often a combination of solar,
wind, and propane.
California is clearly the hotbed of innovation
in this area. In recognition of that
fact, the U.S. National Science Foundation
awarded a $39 million grant in October
2020 to better integrate renewables
into the power grid. The funds are helping
a team of engineers and computer
scientists at the University of California,
San Diego build a first-of-its-kind testbed
to better understand how to integrate
www.powermag.com
1. The Blue Lake Rancheria microgrid
can operate islanded from the main utility
grid. A solar array, battery storage, and a
Siemens microgrid controller-the Spectrum
Power Microgrid Management System-are
integrated in the system. Courtesy: Siemens
distributed energy resources, such as
solar panels, wind turbines, smart buildings,
and electric vehicle batteries, into
the power grid. The goal is to make the
testbed available to outside research
teams and industry by 2025.
One emerging strategy for improving
the resilience of local electricity distribution
systems is the deployment of
microgrids. These represent a truly innovative
approach that help to solve a
number of the problems facing California's
cities. In the event of a larger-scale
emergency, microgrids can
" island "
their service area and continue providing
electricity until the larger grid is restored,
depending on their design.
Novel Microgrid Designs
Microgrids can be as small as a single
building or set of critical building functions,
or as large as an entire corporate
or academic campus, downtown
business district, or neighborhood.
Microgrids can be powered with traditional
combustion energy sources (such
as generators), by renewable energy
sources (solar, wind, or biogas), or a
combination of these and storage.
There are already several noteworthy
examples of microgrids in California. The
POWER | April 2022

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Power April 2022 Intl

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