POWER November 2020 - 31

ENERGY-WATER NEXUS
about 48 GW of nuclear capacity with elevated
exposure to combined rising heat
and water stress across the U.S. "
Hydropower, the cornerstone of many
states' and countries' decarbonization
plans, is especially vulnerable in the overall
climate change-related energy-water
nexus. In its preliminary root cause analysis
of the load shedding events this August,
for example, California grid operator
and regulatory agencies noted hydro conditions
in the state for the summer 2020
were below normal owing to heat and
drought. In Africa, where hydro accounts
for 22% of power generation (compared
to 16% globally), droughts or water scarcity
last year prompted blackouts in Zambia
and Zimbabwe, and prompted fresh calls
for countries to rethink major hydropower
projects, like the 6.4-GW Grand Ethiopian
Renaissance Dam (GERD). Escalating water
tensions between Egypt and Ethiopia
relating to the GERD project this summer,
notably, illustrated the geopolitical
impacts of the deep connection between
energy and water security. In Europe,
meanwhile, major utilities with large hydropower
portfolios, such as Electricité de
France SA and Energias de Portugal SA,
are shedding hydropower assets in a bid
to relieve " hydrological risks " posed by
climate irregularities.
Energy Needed to Ensure Water
Security
At the same time, however, general
uncertainties over water supplies and
diminishing water quality-including
for potable water and industrial purposes-are
prompting new energy projects
to meet increasing demand to move,
pump, and treat water. Interest in desalination
has flourished all over the world,
but most prominently in the Middle East.
In that region, desalination accounts
for just 3% of the water supply today but
5% of its total energy consumption, according
to the IEA. The agency projects
that by 2040, under the SDS, desalination
could account for roughly a quarter
of the region's water supply and almost
15% of total final energy consumption.
But close coupling of the power and
water sector comes with risks, too. As a
recent example, when Israel, which depends
on desalinated seawater for 80%
of its domestic drinking water, suffered
an extreme heat wave in May 2019, the
Israeli Electricity Authority urged large
consumers, including the nation's five
desalination plants, to shed load, even
though water demands in the national
system were also soaring.
November 2020 | POWER
2. Dutch researchers last year conducted a meta-analysis of how much surface or ground
water (blue water) is consumed in liters per megawatt-hour (L/MWh) over the lifecycle across
several energy generation types including photovoltaic solar (PV) and concentrating solar power
(CSP). The circles represent outlying influences on water consumption, while the dots represent
the average for each power type. mdn = median value of water consumption for each fuel
type. Source: Water use of electricity technologies: A global meta-analysis (November 2019)
As experts widely note, the sustainability
of desalination, which is still majority
owned by the power sector, remains
under question. Today, for example, twothirds
of the water produced from seawater
desalination in the Middle East is
derived from fossil fuel-based thermal
desalination, while the rest is from membrane-based
desalination that relies heavily
on electricity produced using natural
gas. However, several entities are also exploring
the use of renewables to produce
the power and heat needed for desalination.
So far, solar PV and solar thermal are
leading that charge, making up more than
half of the world's renewable desalination
capacity, followed by wind power.
What Can Be Done?
Beyond increasing installations of less-waterintensive
technologies like wind and solar
PV, the power sector has made substantial
gains in retooling facilities. Many have adopted
dry cooling, for example, or advanced
technologies that reduce water withdrawal
and consumption, such as plume abatement
equipment, which reduces cooling tower
auxiliary power loads and water vapor emissions.
Costs, however, remain a key challenge
to encouraging uptake of new cooling
technologies.
Alternative water
sources,
meanwhile, could negatively impact cooling
equipment, create regulatory compliance issues,
and limit siting locations.
Water management plans have also
gained prominence both at the state and grid
level. Today, some power plants in the western
U.S., for example, have their own water
plans to forecast and optimize water use.
On a larger level, however, how the
world should move to address the energywater
nexus in the climate context may
be impaired by crucial data gaps, as three
Dutch researchers, Paul Behrens and Arwww.powermag.com
nold
Tukker from Leiden University, and
Laura Scherer from the Netherlands Organization
for Applied Scientific Research,
pointed out. The researchers, who last year
surveyed the vast body of existing literature
on the nexus between power production
and water use, found that studies generally
present estimates of water uses " without
simultaneously presenting their influencing
factors, " leaving data gaps that may add to
planning uncertainty. If available data is considered
along with factors that lie outside
power plant lifecycle water consumption, a
new picture emerges that suggests a larger
range of water use across all energy types,
the researchers said (Figure 2).
Generally, the researchers found that
solar PV, wind power, and run-of-river hydropower
consume relatively little water,
but that CSP and geothermal consume
" intermediate " volumes of water. But
within the renewable energy category,
woody and herbaceous biomass, and reservoir
hydropower were shown to have
" extremely high " volumetric water footprints.
Coal, predictably, led water use
among non-renewables, while nuclear had
the lowest water consumption per unit of
power production (owing to its high electric
output over generally longer lifetimes).
As significantly, if thermal power plants
were outfitted with carbon capture and
storage, their operational water consumption
could increase up to 81%, they found.
The researchers also stressed that the
deployment location of power production
largely affects countries' water use of energy
systems due to different climate conditions
and water resources, as well as the
impacts caused by it due to water scarcity.
" However, the latter are rarely considered, "
they said. ■
-Sonal Patel is a POWER senior
associate editor.
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POWER November 2020

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