Unit-level analyses of the power sector

Unit-level analyses of the power sector

November 17, 2020Payne Institute

Colorado School of Mines

Steve DavisDept. of Earth System ScienceDept. of Civil and Environmental EngineeringUniversity of California, [email protected]@SteveDavisUCI

Outline

“Committed” CO2 emissions

Water use (Flexibility, intensity, and vulnerability)

Tong et al., Nature, 2019

Y. Qin et al., Nature Sustainability, 2019

Shearer et al., AGU Advances, 2020

Fofrich et al., Environmental Research Letters, 2020

Retirement schedules

Jackson et al., ERL, 2018

Ambitious emissions trajectories

2.6 W/m2

(avoids 2 °C)

1.9 W/m2

(avoids 1.5 °C)

Past

Steering mitigation by looking at annual emissions?

35-60 Years

Infrastructural inertia

Infrastructural inertia

15-20 Years

Future CO2 emissions if existing (in 2009) fossil fuel-burning infrastructure were retired on schedule.

Annu

al e

mis

sion

s (G

t CO

2)

Committed emissions, 2009 cumulative: ~500 Gt CO2

Davis et al., Science, 2010An

nual

em

issi

ons

(Gt C

O2)

Power Plants

Davis et al., Science, 2010

Committed warming, 2009

<1.5 °C

Committed emissions, 2018 cumulative: ~650 Gt CO2Including proposed: ~830 Gt CO2

Power Plants


Age distribution of global power plants(as of 2018)


Comparing with carbon budgets, sensitivity to assumptions


Associated economic value of emitting infrastructure



Looking on the bright side

Take-aways

• If operated as historically, future emissions from existing (and proposed) energy infrastructure will be ~650 (~830) Gt CO2

• This represents:• more than the entire carbon budget in scenarios that limit mean

warming to 1.5 °C (420-580 Gt CO2), and

• four-fifths of the budget required by scenarios that limit warming to 2 °C (870-1120 Gt CO2)

• Although there are many aspirations for a ”green” COVID recovery, stimulus may go the wrong way: China has permitted 17 GW of coal capacity since January, and construction has already begun on 11 GW.

U.S. power sector emissions

Between 2010 and 2018, U.S. power plant emissions declined by 24%

(from 2.39 to 1.76 Gt CO2).

The decline reflects a large-scale transition from coal to less carbon-intensive natural gas.


Age distribution of U.S. power plants(as of 2000)

Age distribution of U.S. power plants(as of 2018)


Age distribution of retired U.S. power plants(2000-2018)


Committed emissions perspective is thus different…

Whereas annual emissions declined by 24% 2000-2018, committed CO2 emissions decreased by only 12% (6 Gt).

The latter decrease is even less if methane leakage is considered (~4% decrease at 2% leakage).

Sensitive to assumed lifetime and CF. But note that CFs of gas have been increasing.


Take-aways

• If plants operate at average capacity factors, mid-century climate targets factors will require 300-400 GW of existing combined cycle gas capacity to retire (or retrofit with CCS) before reaching 40 years old.

• And of course that number increases with every plant we commission (according to EIA, 9.3 GW of new gas capacity was planned for 2020).


inconsistent

Inferring plant lifetimes (or stranded assets) from IAM mitigation scenarios

Fofrich et al., ERL, 2020

Integrated assessment models project fuel-specific electricity

demand.

In mitigation scenarios (i.e. that stabilize below 1.5 °C or 2 °C),

demand for fossil electricity often drops off quickly


But existing capacity may not be sufficient to meet the projected demand if it retires on schedule.



Thus, the scenarios imply new capacity.



However, some of the new capacity needed in the

short-term will outlive its usefulness given the sharp decreases in demand over

the longer-term.



As with estimates of committed emissions, the magnitude of excess capacity depends on expected retirement ages and capacity factors.


The most ambitious SSP scenarios imply very short plant lifetimes, especially for coal


(likely to stabilize at <1.5 °C) (likely to stabilize at <1.5 °C)


Less problems for gas in 2 °C scenarios, but still a big coal hangover

(likely to stabilize at <2 °C) (likely to stabilize at <2 °C)

Take-aways

• Climate mitigation scenarios rely on the early retirement of power plants.

• Quantifying lifetimes and operating limits of power plants consistent with climate goals may inform energy investments, permitting, and policies.


40% CF

Studies of water stress have tended to focus on water resources

But the major uses of water around the world are highly varied

Agriculture(annual crops)

Agriculture(perennial crops)

Cooling of thermal power plants

Evaporative losses from reservoirs

Direct human consumption

Livestock

Inflexible uses

Methods: Cooling of thermal power plants

(1) Geolocated all thermal generating units(2) Determined cooling technology of each(3) Analyzed water use for heat dissipation as a function of cooling technology,

thermal efficiency, estimated electricity generation, and meteorological conditions (MERRA-2 Reanalysis data of temperature, humidity, and wind speed).

Qin et al., Nature Sustainability, 2019

Methods: Evaporative losses from reservoirs

Based on reservoir location and surface area from the Global Reservoir and Dam (GRanD) database, we estimated yearly evaporation using same MERRA-2 Reanalysis data (e.g., temperature, humidity, and wind speed).


Inflexible and flexible water consumption have been increasing


Relative to other uses, cooling of thermal power plants is small, though water

evaporated from reservoirs is substantial.

Water stress index


There is a large range in water consumption intensities of power

In some cases, most water stressed basins

(yellows and reds) have both large generation (y-axis) and high water use

intensities (x-axis).


Take-aways

• Globally, some water basins are characterized by less flexible water uses

• A vulnerability index that includes such inflexibility shows that vulnerable (and sometimes highly exposed) basins are concentrated in the Western U.S., the Middle East, and Central and East Asia.

• Some of these vulnerable basins also have high consumption intensities, suggesting opportunities to reduce vulnerability by switching technologies/crops or relocating production.

Overarching take-aways

• Unit-level analyses of emissions and resource use in the power sector complement retrospective analyses and energy-emissions models:

1. Expected lifetimes and current asset values suggest future emissions (or stranded assets)

2. Specificity may support planning and policy interventions that high-level scenarios do not

3. Emissions or water use intensities can identify targeted mitigation opportunities

• Ongoing work in this theme:

1. Analyses of recent retirements and most ‘at-risk’ capacity.

2. A ‘capacity expansion’ model that adds unit-level granularity to integrated assessment model scenarios in order to project future criteria emissions-–and health impacts

Thank you.Acknowledgements

(My Group) Dan Tong (postdoc), Robert Fofrich (PhD student), Yue Qin (faculty at Ohio State), Chaopeng Hong (postdoc), Xinying Qin (PhD student), Christine Shearer (Global Energy Monitor)

(Collaborators)Amir AghaKouchak Jen Burney Ken CaldeiraKate Calvin Dabo Guan Rob JacksonNathan Mueller Joeri Rogelj Christine ShearerStefan Siebert Qiang Zhang Julie Zimmerman

Unit-level database of power plant emissions available here:http://www.meicmodel.org/dataset-gped.html

Unit-level analyses of the power sector

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