UTILITY MASTER PLAN PROCESS
In 2014, Carleton embarked on a utility master-planning process, following
publication of a comprehensive Campus
Master Plan. The Utility Master Plan aimed
to replace the aging and outdated central
plant equipment and controls, to provide
for future loads outlined in the Campus
Master Plan and to reduce cost and carbon emissions. The college’s utility master-planning process consisted of seven
Step 1: Update the Campus Master Plan
Carleton recognized a well-vetted
and thoughtful Campus Master Plan must
be established before launching a comprehensive Utility Master Plan. This was
key to assuring the utility planning efforts
aligned with an accurate projection of
future energy use. Carleton’s Campus
Master Plan forecast building plans over
the next 20-30 years and a timeline of
how campus square footage, and therefore energy use, would evolve. Fortunately, this thoughtful space-planning
process revealed a focus on replacement
and renovation, rather than campus
growth, allowing the subsequent utility
planning to focus on quality, not just
CARLETON’S CAMPUS MASTER PLAN
ALLOWED SUBSEQUENT UTILITY PLANNING
TO FOCUS ON QUALIT Y, NOT JUST EXPANDED
Step 2: Hire a design team
Carleton selected MEP Associates
LLC based on the firm’s experience with
district utility-scale geothermal systems.
MEP’s work as the lead designer of Ball
State University’s campus geothermal conversion project had inspired Carleton’s
team to think about geothermal not just as
an individual building solution but rather
as a part of the overall district energy system. Carleton’s Climate Action Plan had
identified ground source heating and cooling as well as combined heat and power as
potential carbon reduction options.
MEP then partnered with Burns &
Step 3: Develop campus energy profiles
McDonnell to address Carleton’s desire to
also evaluate the feasibility of CHP tech-
nologies. Collaborative Design Group and
TKDA out of Minneapolis-St. Paul provided
architectural, structural and civil support.
Carleton also partnered with McGough
Construction to develop market-tested
construction estimates that not only cap-
tured full costs represented by the design
but also tested construction means and
methods, site logistics, and phasing.
Carleton shared campus history,
three years of utility bills, planning documents, as-built building prints, wind generation records, building meter data and
other pertinent documentation, which
was used to create an energy model for
the existing campus. The model generated annual electrical, heating and cooling energy profiles for the physical plant
(fig. 1), which emphasized the high heating demand in winter and opportunities
to take advantage of some year-round
simultaneous heating and cooling. The
model was then verified and calibrated,
based on the actual consumption data.
Using the calibrated model, future energy
profiles were generated in five-year increments to reflect the impact of future campus construction milestones outlined
in the Campus Master Plan. This energy
demand timeline became the basis for
the design team to formulate and test-drive various campus utilities options.
Step 4: Perform a conceptual study
The analysis began with a high-level
conceptual study investigating several
options before diving into a detailed engi-
neering analysis. This process gave the
team an initial sense for the long-term per-
formance of different strategies, the rela-
tive influence of study parameters and
ways to optimize the options warranting
further investigation. To start this process,
a business-as-usual case was defined to
model investments in the existing cam-
pus systems required to meet changing
energy demands of the Campus Master
Plan over the next 20-30 years. The various
options were all based on converting the
district steam distribution system to a 120
degree F hot water supply. Different sizes
of ground source heat pump (geothermal)
systems were developed.
Concept study options included the
1. Option A – Base case: maintain existing
2. Option B – Ground source heat pump
system sized to meet 100 percent of
campus heating and cooling loads.
3. Option C – Ground source heat pump
system sized to meet 100 percent of
peak cooling demand with condensing
boilers to supplement peak heating load.
4. Option D – Ground source heat pump
system sized to meet 50 percent of peak
cooling demand and approximately
20 percent of the peak heating load.
Condensing boilers supplement peak
heating demand, and existing chillers
supplement peak cooling demand.
For the initial screening, the business-as-usual condition was compared
to the hot water options over a 30-year
period. The cost analysis compared the
30-year net present value of cumulative
capital, operation, maintenance and utility costs. The team also compared per-
FIGURE 1. Current heating and cooling load profile, Carleton College.
Source: Carleton College.