Senior Design Expo 2019

Retrofitting Heating and Cooling Systems
with Variable Refrigerant Flow System
on Columbia University’s Morningside
Campus
Ji Ho Jeon, Iris Lin, Yueli Liang, Yukun
Yang
Advisor: Robert Farrauto
Variable Refrigerant Flow (VRF) is an airsource
heat pump (ASHP) technology that
can be used to heat and cool spaces. ASHPs
are high-efficiency electric appliances that
transfer heat rather than generate it.
Compared to conventional steam boiler
system, ASHPs save energy, reduce
greenhouse gas emissions, and greatly
improve resident comfort, offering
multifamily buildings a path to
electrification.
This retrofit project aims to analyze the
possibilities of implementing ASHP systems
to McBain Hall, a residential building for
Columbia undergraduate students. A number
of different heat pump models are selected
based on the building conditions and weather
conditions of New York City. From assessing
the energy consumption of the building,
conducting an economic feasibility study of
ASHPs, and calculating CO2 emissions, a
specific VRF system design will be
suggested.
Calendar Year 2016-2018 electricity bills
from Con Edison were used for the energy
usage analysis. Electricity and natural gas
consumption and demand profiles were used
as the primary source to evaluate the
capacities of selected ASHPs and estimated
installation costs. Furthermore,
environmental impact analysis was
conducted to calculate CO2 emissions
reduction of converting heating source from
natural gas to electricity.
OpenStudio 2.7.0 was used to run the ASHP
simulation on EnergyPlus. The model was
built using SketchUp Pro 2017 with the
Legacy OpenStudio Plug-in. Local weather
data, energy constructions, loads, space
types, facility information, geometry, thermal
zone, and HVAC systems were adjusted to
match the real world conditions for this
simulation.
The coefficient of performance varies from
2.05 to 3.20 for air source heat pumps based
on different models and temperatures, and 1
for the steam heating system. Therefore,
when the ambient temperature is at 47°F, by
implementing the air source heat pump, the
carbon dioxide emission will decrease by 54-
69% or 475-602 kilograms; and when the
ambient temperature is at 17°F, the carbon
dioxide emission will decrease by 50.5-
52.3% or 1187-1230 kilograms.
An electricity grid update would be needed
before installing high capacity heat pumps on
the rooftop of McBain. After the renovation,
old radiators and conventional ACs would be
replaced by multi-zone indoor unit
connecting to heat pumps.
Acknowledgments
This work was supported in part by Columbia
University’s Department of Facilities and
Operations. The authors thank Dominick Chirico,
Tak Eng, and Robert Kishun for discussions and
granting access to McBain Hall’s utility data and
floor plans. We also thank Noah B. Rauschkolb
for his help with building energy simulation.
Furthermore, the Energy Usage Analysis tool was
provided by EN-POWER GROUP, an energy
engineering firm located in New York City. We
thank Amalia Cuadra, Sean Lee, and Griffin Teed
for granting access to their tool and providing
guidance in designing the VRF system.
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