ASHRAE Journal - January 2014 - 30

TECHNICAL FEATURE
What's Next for District Energy
BY DAVID W. WADE, P.E., MEMBER ASHRAE, RDA ENGINEERING, MARIETTA, GA.
What's next for district energy? This technology was
commercially applied 135 years ago in upstate New York
to heat a group of buildings from a central plant. By
ASHRAE's definition, district energy provides heating
and/or cooling services to groups of buildings from a
central plant through a piping distribution network.
According to the latest DOE survey, of the 64 bil-
lion ft2 (6 billion m2) of commercial buildings in the
United States, 8.6% used district heating and 4.5%
used district cooling. Austria provides 21% of its citizens
with district heating, Germany provides 12%
of their energy needs by district energy and Danish
district systems serve 60% of all buildings. The reason
for the difference in use is largely institutional rather
than technical. Implementing district energy requires
considering the energy needs of multiple buildings
in a community setting. Most U.S. buildings are
conceived, designed and constructed by individuals
who rarely consider the energy characteristics of surrounding
buildings.
U.S. codes and design protocols deal with energy use
at a single building. We think "net zero energy buildings,"
not "net zero energy communities." Private utilities
in the U.S. reinforce this approach through their
focused marketing of electric or natural gas service.
The future may change though if the building industry
adopts a new paradigm that considers reducing
community energy use.
Even net zero buildings require a grid to balance
annual energy production and use. Designers think of
the grid as the electric utility; however, the possibilities
for energy efficiency expand greatly when a district
References
1. Griffith, B., et al. 2007. "Assessment of the Technical
Potential for Achieving Net Zero-Energy Buildings in the
Commercial Sector." 114 pp.; NREL Report No. TP-550-41957.
2. EIA. 2005. "Commercial Buildings Energy Consumption
Survey: Consumption and Expenditures Tables." U.S.
Department of Energy, Energy Information Agency. www.eia.
doe.gov/emeu/cbecs/.
3. Torcellini, P., et al. 2006. "Lessons Learned from Case
Studies of Six High-Performance Buildings." 151 pp.;
NREL Report No. TP-550-37542. www.nrel.gov/buildings/
pdfs/37542.pdf.
Paul Torcellini, Ph.D., P.E., is a principal engineer at the National Renewable Energy Laboratory, Golden, Colo.
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ashrae.org JAN UARY 2014
energy thermal grid is included. Thermal grids providing
low-temperature hot water for heating and chilled
water for cooling allow a community to use waste heat
from power production (combined heat and power),
heat generated from refuse incineration, solar energy,
and industrial low grade waste heat normally lost to
the atmosphere. Thermal grids can interface with heat
pump systems, natural cooling from lakes, geothermal
wells or deep ocean thermal sources. Both heating and
cooling grids can incorporate daily and annual thermal
storage as community energy requirements dictate.
District energy, along with micro-electric grids, allow
combinations of technologies to meet a building's
energy requirements through waste heat recovery storage
and the use of biomass, wind, solar or geothermal
on a community scale.
More than 8.5 million refrigeration tons (29 million
kW) of district cooling infrastructure will be in place by
the year 2015 in Middle East cities, helping to reduce
electric peak loads and provide for long-term integration
with multiple energy sources. In Germany, engineers
are mapping locations, temperatures and quantities
of waste heat available from industrial and power
plant facilities to develop hot water district networks
that will reduce greenhouse emissions.
Denmark has seen a private company develop a multi-
city grid that connects municipal district energy systems
to take advantage of installed boiler capacity and waste
heat availability. Here in the United States, a Midwest
college is installing a new low-temperature hot water
district system to replace an aging steam system. Energy
is provided by heat pumps connected with geothermal
wells installed under practice football fields.
David W. Wade, P.E., is president at RDA Engineering, Marietta, Ga.
Zeroing in on Future Energy Codes
BY HARRY MISURIELLO, MEMBER ASHRAE
ASHRAE has served the nation as a leading developer
of building energy standards since 1975. The Society
is unique in that federal law mandates ASHRAE/IES
Standard 90.1 as the benchmark for state energy codes
for most commercial buildings as well as setting national
performance standards for most types of HVAC equipment.
ASHRAE has been handling this responsibility
effectively.
From 1975 to 2013, Standard 90.1 has improved
new commercial construction energy efficiency by

ASHRAE Journal - January 2014

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