ASHRAE Journal - January 2022 - 61

REFRIGERATION APPLICATIONS
COLUMN
Andy Pearson
Energy Efficiency
Wrapping up the SDGs
BY ANDY PEARSON, PH.D., C.ENG., FELLOW ASHRAE
The UN Sustainable Development Goals (SDG) that have not yet been addressed in
this short series are: decent work and economic growth; responsible consumption
and production; peace, justice and strong institutions; and partnerships for the goals
(goals 8, 12, 16 and 17). However this month's column is not just a catch-all, sweeping
up the left-overs. These goals have a lot in common in the refrigeration context.
The thread that ties them together is energy efficiency.
I have been fascinated for several years-some of my colleagues
might even say fixated-by the remarkable range
in energy performance of cold storage buildings in the
logistics sector. I find it difficult to understand how the
average store in a pan-European survey could use ten
times more energy on an annual basis than the best-inclass.
This discrepancy is between the best and the average;
by definition half must be worse than average.
In studying this phenomenon I have come to some
surprising conclusions. The one that
gets most resistance from the refrigeration
community is that the best practice
metric I use is not dependent on the
design ambient for the site. I have studied
warehouses in northern Europe,
with a relatively cool climate, and in
northern Australia, well into the tropics,
and found if best practice design
principles are applied, the annual energy use per cubic
foot for the stores will not be significantly different.
This needs a little explanation. If the store is well
insulated, well maintained and well run-all features of
a " best practice " facility-the heat load imposed on the
building by the ambient will not be significant. If the
refrigeration system is well designed and well operated,
over the course of a year the peak ambient operating
condition becomes relatively unimportant. The key to
best practice in this regard is to allow the compressor
discharge pressure to float down as low as possible.
In this way the efficiency overnight and in cooler
months will dominate total consumption figures, and
Daily variation-a game of two halves.
the relatively few times it has to run flat out won't have a
massive effect on overall performance. This idea can be
extended to encourage operation during lower ambients
by adjusting the setpoint automatically a few degrees.
Soccer commentators sometimes talk about " a game of
two halves, " and the visual representation of the average
daily changes in ambient dry-bulb temperature in the
U.S. shown in this map paints a similar picture. On the
right, where daily variation is on average less than 14°F
(7.8°C) in July, the load shifting strategy is less necessary,
but on the left, where daily variation
can be as high as 45°F (25°C), a lot can
be gained by floating heads and shifting
loads.
My analysis of the SDGs reinforces
that this is a great time to be an engineer.
There is plenty of interesting and
useful " decent work " around and great
scope for economic growth in refrigeration.
We need to take our responsibilities in consumption
and production more seriously than in the past,
and we need strong institutions, like ASHRAE, emphasizing
the need for good engineering and encouraging
a greater understanding of these odd quirks of system
operation. Finally, we need to recognize that no segment
of the industry can achieve these goals alone; it requires
a higher degree of interdisciplinary collaborative work
than ever before. This extends beyond our comfort zone
of refrigeration engineering and needs to encompass
finance, risk management, education, mentoring and,
above all, communication skills.
Andy Pearson, Ph.D., C.Eng., is group managing director at Star Refrigeration in Glasgow, UK.
J A N U A RY 2022 ashrae.org ASHRAE JOURNAL
61
SOURCE: PRISM CLIMATE GROUP, OREGON STATE
UNIVERSITY; MAP FROM U.S. CENSUS BUREAU

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