With scale comes savings
No matter how efficiently designed, high rises with limited roof
space and energy-intensive hospitals (to name two examples)
can find it impossible to meet annual energy needs through on-
site generation. In addition, researchers and developers looking
for new ways to make net zero more affordable are discover-
ing that spreading capital costs across multiple buildings and
maximizing economies of scale can make energy targets more
affordable and, possibly, add resilience to facility operations.
“Any time you can put in bigger systems, spread across sev-
eral buildings, there are economies of scale on a whole range
of systems,” said Shanti Pless, a manager with the Commercial
Buildings Research Group at the National Renewable Energy
Pless cites load diversity—buildings with different use pat-
terns that can benefit from sharing resources—as an advantage.
“On the mechanical side, up to 30 percent less cooling ton-
nage can be required across a larger group of buildings, versus
individual buildings,” he said.
Victor Olgyay, a principal with Rocky Mountain Institute
(RMI), said some more specifics to the diversity a mixed-use
development could have in its loads.
“Restaurants often have large loads—warehouses, not so
much,” he said. “Some buildings are used during the day, oth-
ers at night. When you put this mix together, you get a much
better chance of getting the overall development to balance out
to a zero-energy district.”
Optimizing a multibuilding development for net-zero per-
formance begins early in the planning stages, especially if new
buildings are part of the effort. Site planning, for example, can
be critical to a project’s future success in meeting energy goals,
according to Olgyay.
“When beginning at a larger scale, lots of site goals can be
coordinated, and often, passive or bioclimatic approaches can
be designed in,” he said.
For example, buildings can be positioned to foster cool
breezes or create sunny garden areas. Also, how buildings are
massed—whether tall and slender or long and low-slung—can
affect on-site energy production.
“On a recent project, we increased solar electricity production by 25 percent, simply by arranging the building massing
for optimal solar access to solar panels,” Olgyay said. “Of course,
this planning can reduce energy use by providing access to daylighting of buildings, as well.”
Building an energy budget
As with individual buildings, getting to net zero on a district
basis begins with maximizing efficiency of all buildings within
the boundaries and understanding how much generation
capacity is available on-site. Massing issues can complicate
this process because each tweak in building orientation can
affect everything from solar heat gain and daylighting availability to solar exposure for photovoltaic panels. Energy-modeling
software capable of considering all of these variables is an
important tool for designers during this process.
“One of the big concerns at a district scale is about ensuring
that we are designing to a realistic energy and financial budget,”
Olgyay said. “If a site has a certified capacity for generating
electricity, we use that to determine the energy-use intensity of
the planned development. The idea is that the solar electricity
generation capacity modeling, energy-load modeling and finan-
cial modeling all inform each other.”
NREL has taken a role in bringing what is now a maturing
building-level modeling-software industry into district-level
projects. There are several issues to deal with, from building
massing to where a solar array might be placed.
“As a national lab, we’re looking at what’s happening next,”
Pless said. “The really interesting opportunity is interfacing
that modeling process with utility distribution-system loads;
there are a lot of opportunities for
a district system to support a more
efficient utility distribution system.
That’s the next front in these inte-
grated modeling tools.”
NREL is exploring district-wide
modeling in two Denver projects
that are in the planning stages.
The National Western Center is a
reimagining of the city’s National
Western Stockshow Complex, a
130-acre site that is home to the
annual National Western Stockshow. Planned to grow to 250
acres, the new center is intended
to add nine new buildings and
operate as an agricultural education extension of Colorado State University.
The second NREL project, the Sun Valley EcoDistrict,
will involve a redevelopment of a low-income neighborhood dominated by the subsidized Sun Valley Homes housing
project, along with a variety of light-industrial and warehouse
buildings. Also, the community is home to a legacy district
steam power plant, which could prove helpful to developers,
plus a new light-rail station will give the anticipated 3,000 residents new emissions-free transit options.
Pless said NREL’s involvement in these two local developments is a win-win situation for both NREL and developers.
“Because they’re trying to do things that have never been
done before, they’re going to come up against barriers,” he
said. “By partnering with these local projects, we get a sense
of those barriers.”
Free energy for life
At a much larger scale, the New York City-based consulting
firm Terrapin Bright Green, co-founded by longtime energy
efficiency and environmental advocate Bill Browning, is aiding
the master planning of a Florida community that could include
up to 170,000 homes. Browning started his career helping with
Buckminster Fuller’s last experimental structure and went on
development for net-
begins early in the
especially if new
buildings are part
of the effort.