ASHRAE Journal - November 2022 - 57

temperature only " approaches " the wet-bulb temperature.
How closely it approaches depends on tower size.
Evaporative cooling provides a substantially lower heat
sink via the cooled water stream and a better heat transfer
medium to remove heat from surfaces, such as the
heat exchangers, than air-cooled alternatives.
Use of this advantageous property is evident in many
industries including mass food production, grain milling,
metals extraction, oil refining, plastic synthesis and
chemical processing. Additionally, refrigeration for food
preservation has allowed life-sustaining expansion in
food production and most particularly food storage.
Power generation has also been enhanced by water's
unique cooling capability. The efficiency improvements
are dramatic and have allowed for the creation of mass
electrification. The survival of populations enduring
increasing temperatures and climate change may
depend on such advantages.
More recent developments in data and information
management are also facilitated by evaporative cooling.
Case studies detailed in this article show evaporative
cooling provides the most energy- and water-efficient
delivery of value in comfort cooling, power generation
and information server management.
Energy. Cooling in commercial buildings is the largest
category of consumer energy use, constituting more
than 30% of the U.S. electrical total. Commercial cooling,
at 14.8%, and refrigeration, at 15.7%, make up this
combined category of energy consumption in businesses.1
Cooling of commercial buildings during peak
load periods is likely an even higher percentage of electrical
demand than cited above. This further stresses
already overburdened power grids. Energy efficiency
achieved in cooling processes via evaporative mechanisms,
detailed in the " Specifics of Resource Utilization
in Cooling " section of this article, will most likely translate
directly into fossil fuel use reduction because coal,
oil and natural gas energy production still constitutes
79% of the U.S. total.4
From an environmental point of view, marginal energy
demand reductions would be expected to subtract from
the least environmentally friendly generation method,
typically derived from fossil fuel. For the few locations
that largely use renewable sources, energy demand
reduction would allow a smaller overall energy production
infrastructure, providing flexibility in capacity
utilization and investment choice. Evaporative cooling
FIGURE 1 Types and amounts of primary energy sources consumed in the U.S.,
2020.
Total = 92.94 Quadrillion British thermal units (Btu)
Petroleum
35%
Nuclear
Electric
Power
9%
Coal
10%
Renewable
Energy
12%
Natural Gas
34%
Total = 11.59 Quadrillion Btu
2%
11%
22%
26%
4%
17%
18%
Geothermal
Solar
Hydroelectric
Wind
Biomass Waste
Biofuels
Wood






Source: U.S. Energy Information Administration, Monthly Energy Review, Table 1.3 and 10.1,
April 2021, preliminary data.
Note: Sum of components may not equal 100% because of independent rounding.
is an excellent resource choice, providing energy
conservation.
To show how power is actually generated today,
sources of primary energy in the U.S. as of 2020 are still
primarily fossil fuel, with petroleum comprising 35% of
sources, natural gas 34% and coal 10% (Figure 1). Nuclear
and renewables- " non-greenhouse gas " sources-make
up about 21%, which includes the 9% nuclear portion of
the total.4
CO2 emissions. Significant CO2 emissions result
from the 79% of U.S. energy production that is provided
by fossil fuel (Figure 1). Energy reductions provided by
evaporative cooling have a substantial positive environmental
impact. Fossil fuels, of various types, produce
CO2 at levels shown in Table 1.5 These amounts of CO2 can
be reduced by energy-efficient cooling and refrigeration
process choices.
Water. Total water consumption can also be lowered
by using evaporative cooling. This is not intuitive.
Alternatives often use little to no water at the cooling
process delivery site, giving the illusion of a substantial
water use advantage. The hidden reality is that aircooled
or alternative systems consume more energy onsite
and use substantially more water at the power generation
site to produce the required energy premium.
The result is that the combined water use for evaporative
cooling on-site and at the point of power generation is
often lower than that of the cooling alternatives. This
concept is explored in depth in the studies detailed in
the next section.
N O V E M B E R 2022 ashrae.o rg ASHRAE JOURNAL
57
Biomass 39%

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