energies
Article
Techno-Economic Analysis of Rooftop Photovoltaic System
under Different Scenarios in China University Campuses
Xingyu Zhu 1,2 , Yuexia Lv 1,2, * , Jinpeng Bi 1,2 , Mingkun Jiang 3 , Yancai Su 1,2 and Tingting Du 4
1
2
3
4
*
Citation: Zhu, X.; Lv, Y.; Bi, J.; Jiang,
M.; Su, Y.; Du, T. Techno-Economic
Analysis of Rooftop Photovoltaic
School of Mechanical Engineering, Qilu University of Technology (Shandong Academy of Sciences),
Jinan 250353, China
Shandong Institute of Mechanical Design and Research, Jinan 250031, China
SPIC Qinghai Photovoltaic Industry Innovation Center Co., Ltd., Xi’an 710000, China
School of Energy and Power Engineering, Shandong University, Jinan 250061, China
Correspondence: yuexialv@foxmail.com
Abstract: The expansively unutilized rooftop spaces in the university campuses can provide an excellent opportunity for the installation of solar photovoltaic systems to achieve renewable electricity
generation and carbon dioxide reduction. Based on available rooftop areas and local solar radiation
situations, technical potential and economic benefits of rooftop photovoltaic system under seven
scenarios were carried out for three university campuses located in different solar zones in China. The
potential capacity of photovoltaic installations on building’s flat rooftops in Tibet University, Qinghai
University, and Qilu University of Technology reaches 11,291 kW, 9102 kW, and 3821 kW, corresponding to the maximum annual power generation of 28.19 GWh, 18.03 GWh, and 5.36 GWh, respectively.
From the perspective of economic analysis, PV systems installed in “full self-consumption” mode are
superior to those installed in “full-feed-into-grid” mode for all three study cases. The highest return
on investment of PV systems installed on flat and pitched rooftops can be achieved at 208% and
204%, respectively, in Tibet University. The payback period for PV systems installed on flat rooftops
is 1 year in Tibet University, and less than 8 years for both Qinghai University and Qilu University of
Technology, respectively. Results reveal that rooftop photovoltaic systems can significantly help the
universities to move towards sustainability.
Keywords: solar photovoltaic; university campus; technical potential; economic analysis
System under Different Scenarios in
China University Campuses. Energies
2023, 16, 3123. https://doi.org/
10.3390/en16073123
Academic Editors: Andrea Reverberi,
Valery Meshaklin, Petros Groumpos,
Alla Kravets and Antony Nzioka
Received: 7 March 2023
Revised: 23 March 2023
Accepted: 26 March 2023
Published: 29 March 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1. Introduction
According to International Energy Agency (IEA) report on Global Energy Review: CO2
Emissions in 2021, global CO2 emissions derived from fossil fuel combustion and industrial
processes was increased to a record high of 36.3 Gt from 2020 pushed emissions [1]. To
effectively limit the global average temperature rise to 1.5 ◦ C above preindustrial levels, it
is critical and urgent to explore the potential of renewable energy sources as an alternative
to traditional fossil fuels to provide a suite of energy services. Attributed to the clean,
abundant, and easily accessible characteristics, solar energy has been extensively utilized
in the fields of heating [2], natural lighting [3], photovoltaic (PV) electricity generation [4],
and solar fuels [5].
The integration of solar photovoltaic energy systems in various buildings has been
proven as a promising solution to reduce CO2 emissions by alleviating or eliminating
fossil fuel utilization in building sector. Ghaleb et al. [6] found that, with the overall
utilization factor of 0.49, an annual power production of 91,122 MWh and a reduction of
72,533 tons of CO2 were achieved by applying PV systems on the studied 105 commercial
buildings in Saudi Arabia. Furthermore, the levelized cost of electricity (LCOE) was
SR 0.16/kWh and the payback period was 13.6 years within the span life of 25 years.
Mohammed et al. [7] analyzed the performance and feasibility of a 10 kWh PV system
for residential buildings in Saudi Arabia and found that the levelized cost of energy in
Energies 2023, 16, 3123. https://doi.org/10.3390/en16073123
https://www.mdpi.com/journal/energies
Energies 2023, 16, 3123
2 of 18
Tabuk was 0.027 $/kWh, and the greenhouse gas reduction was 330.88 tons of CO2 per
year. Yang et al. [8] investigated the potential of solar PVs mounted on roofs of different
types of buildings in Sweden, and an approximately available roof area of 504 km2 could
yield the maximum installed capacity potential of 65 GWp–84 GWp in Sweden. According
to the International Renewable Energy Agency, the installed photovoltaic capacity in China
was increased from 1.0 GW to 204.3 GW over the past decade from 2010 to 2019, which was
mainly due to strong government supports and heavy industry investments [9].
University campuses have a variety of building types with large roof surfaces and
diverse utilization purposes including academic, research, residential, athletics, and administration. Serving as a multifunctional comprehensive infrastructure in the society, universities have been facing the urgent challenges relevant to the high energy consumption.
Switching to renewable energy is an alternative way to reduce campus-wide environmental
impacts in response to the commitment of carbon neutrality and peak carbon dioxide
emissions. Until 2020, more than 40 colleges and universities have already led the transition
to 100% renewable energy on campus by shifting to renewable electricity, adopting electric
vehicles, or repowering building with clean energy [10].
A variety of studies have been carried out to explore the potential of solar PV utilization
at the scale of university campus. Thai et al. [11] investigated the power generation potential
of solar PV panels in the University of California campuses based on utilization factors,
and estimated a combined potential capacity of 345 MW and 471 MW corresponding
to frozen building development cases and new buildings converted from parking lots,
respectively. The performance analysis of grid-connected PV systems installed at the
Hashemite University in Jordan revealed that, the annual final yield of two 7.98 kWp PV
systems with and without tracking elements was 2572 kWh/kWp and 1959 kWh/kWp,
corresponding to a total saving of $138,825 and $105,737 over 20 years, respectively [12].
A 42 kW PV system installed at the West Texas A&M University annually generated
71,000 kWh and saved around $6390 by reducing energy consumption from the electrical
grid [13]. A 67 kW PV system at the University of New Haven located in New England
could generate an amount of 82,800 kWh electricity and a cumulative cash flow of $360,000
over its 25-year lifetime [14]. PV systems installed at the Technical University of Madrid
provided an optimal power of 3.3 MW, approximate 77% of which was locally consumed to
cover 40% of the total electricity consumption of 0. Obeng et al. [15] designed a 50 MW gridtied solar PV plant with three PV systems at the University of Energy and Natural Resources
in Ghana, which had the capacity to supply more than 48% of the campus’ electricity
demand. Atri et al. [16] analyzed the technical and economic potential of installing a
solar PV plant in Manav Rachna education campus in India. The PV output could meet
85% of the electricity demand and 31,000 MWh of surplus energy was sold to the grid,
with the investment recovered in nearly 7 years. Low-rise residential buildings integrated
with solar PV systems had the potential to become net zero energy buildings, and the
designed nominal PV power for The Indian Institute of Technology Kharagpur could
meet the maximum residential energy demand in the studied academic campus in the
COVID-19 affected year [17]. Mokhtara et al. [18] applied grid-connected rooftop PV
systems in education buildings in an Algeria university campus, and their results showed
that 60% of the roof area was optimally appropriate for PV installations and that the highest
annual electricity output of 2333.11 MWh/year could be achieved. 1 MW rooftop solar PV
proposed for Purwanchal Campus in Nepal gave a return on investment of 190% within
its 25-year service life, with a levelized cost of energy of 0.069 USD/kWh and payback
period of 8.4 years [19]. Ali et al. [20] found that the payback period of grid-connected
PV systems installed in Zakho University in Iraq could be reduced to 4 years with the
use of local generators, demonstrating that the proposed PV systems were quite favorable
for university campuses in Iraq. Ahmed et al. [21] investigated the PV systems on the
building rooftops in NED University of Engineering and Technology in Pakistan. Based on
comprehensive analysis from the perspectives of technical feasibility, financial viability, and
environmental benefits, it was concluded that PV applications in universities’ buildings
Energies 2023, 16, 3123
of local generators, demonstrating that the proposed PV systems were quite favorable for
university campuses in Iraq. Ahmed et al. [21] investigated the PV systems on the building
rooftops in NED University of Engineering and Technology in Pakistan. Based on com‐
prehensive analysis from the perspectives of technical feasibility, financial viability, and
3 of 18
environmental benefits, it was concluded that PV applications in universities’ buildings
were a viable choice and building rooftops in university campuses should be capitalized
to solve their increasing energy demand.
were The
a viable
choice
and building
rooftops in
university
campuses
should
be capitalized
to
above
literature
review indicates
that
rooftop PV
systems
installed
in university
solve
their increasing
energy
demand. economic revenue, and environmental benefits.
campuses
present power
generation,
The above
review indicates
that rooftop
PVsystems
systemswith
installed
in configura‐
university
However,
mostliterature
relevant research
mainly focuses
on PV
a fixed
campuses
present
power
generation,
economic
revenue,
and
environmental
benefits.
Howtion, without considering the tradeoff between technical performance and economic
as‐
ever,
most
relevant
research
mainly
focuses
on
PV
systems
with
a
fixed
configuration,
sessments of PV systems with different configurations. In addition, to our knowledge, a
without
considering
the tradeoff
technical performance
and location,
economictechnical
assessments
comprehensive
assessment
frombetween
the perspectives
of geographical
po‐
of
PV systems
with different
configurations.
Insystems
addition,
to our knowledge,
a comprehentential,
and economic
benefits
for rooftop PV
installed
in universities
campuses
sive
assessment
perspectives
of geographical
location,oftechnical
potential,
and
in China
has notfrom
beenthe
published.
Therefore,
the main objective
the present
study is
to
economic
benefits
for
rooftop
PV
systems
installed
in
universities
campuses
in
China
has
qualitatively and quantitatively evaluate the rooftop solar PV systems installed in univer‐
not
published.
Therefore,
thesolar
main
objective
of the
present study
is installation
to qualitatively
sity been
campuses
located
in different
zones
in China,
considering
seven
sce‐
and
quantitatively
evaluate
the
rooftop
solar
PV
systems
installed
in
university
campuses
narios for PV systems mounted on flat and pitched rooftops, and two electricity
selling
located
in different solar zones in China, considering seven installation scenarios for PV
strategies.
systems
mounted
on flat the
andrest
pitched
rooftops,
two electricity
selling
strategies.
After
introduction,
of this
study isand
organized
as follows.
Section
2 presents
After introduction, the rest of this study is organized as follows. Section 2 presents the
the research methodology which describes the data acquisition, PV module spacing rele‐
research methodology which describes the data acquisition, PV module spacing relevant
vant with flat and pitched rooftops, and energy potential and economic indicators for the
with flat and pitched rooftops, and energy potential and economic indicators for the
proposed PV system. Section 3 gives a detailed description of three study cases located in
proposed PV system. Section 3 gives a detailed description of three study cases located in
three different solar zones, as well as seven installation scenarios. Results and discussion
three different solar zones, as well as seven installation scenarios. Results and discussion
for technical potential and economic performances are given in Section 4. Finally, Section
for technical potential and economic performances are given in Section 4. Finally, Section 5
5 summarizes the main conclusions of the present study.
summarizes the main conclusions of the present study.
2. Methodology
Methodology
2.
The methodology
methodology flowchart
flowchart in
in the
the present
present study
study is
is shown
shown in
in Figure
Figure 1.
1. This
This study
study
The
starts
with
the
estimation
of
available
rooftop
areas
for
photovoltaic
systems
deployed
on
starts with the estimation of available rooftop areas for photovoltaic systems deployed
university
buildings
with
the
help
of
LocaSpace
Viewer
software
and
the
Meteonorm
da‐
on university buildings with the help of LocaSpace Viewer software and the Meteonorm
tabase. Then
technical
potential
under seven
seven
database.
Then
technical
potentialand
andcomparative
comparativeanalysis
analysisisis carried
carried out
out under
scenarios for
forphotovoltaic
photovoltaic
systems
different
configurations.
scenarios
systems
withwith
different
configurations.
Finally, Finally,
economiceconomic
analysis
analysis
is conducted,
lifetime
netreturn
income,
return on investment,
present
is
conducted,
includingincluding
lifetime net
income,
on investment,
net presentnet
value,
and
value,
and
levelized
cost
of
energy.
levelized cost of energy.
Figure 1.
1. The methodology flowchart
flowchart in
in this
this study.
study.
Figure
2.1.
2.1. Data
Data Source
Source
The
annual
system
mainly
depends
on the
PV panel
effiThe annual power
powerproduction
productionbybya PV
a PV
system
mainly
depends
on the
PV panel
ciency,
system
performance
ratio,
meteorological
parameters,
PV
panel
orientation,
and
efficiency, system performance ratio, meteorological parameters, PV panel orientation,
layout
[22]. [22].
In the
study,
hourly
globalglobal
horizontal
radiation,
diffusediffuse
horizontal
radiaand layout
Inpresent
the present
study,
hourly
horizontal
radiation,
horizontal
tion,
tilted
plane
global
radiation,
ambient
temperature,
and
wind
speed
data
were
acquired
radiation, tilted plane global radiation, ambient temperature, and wind speed data were
from METEONORM Global Meteorological Database [23]. Satellite images of the studied
acquired from METEONORM Global Meteorological Database [23]. Satellite images of the
cases were obtained from Local Space Viewer, and the utilizable rooftop area available for
studied cases were obtained from Local Space Viewer, and the utilizable rooftop area
the application of PV systems was manually measured to exclude unusable areas.
2.2. PV Module Spacing
Two types of roofs with different appearances, named flat roofs and pitched roofs, have
both been widely utilized in typical univerisity buildings depending on the surrouding
climate and building types. The schematic diagram of the a PV module installed on a
flat roof is shown in Figure 2. In this case, the PV module spacing is calculated using the
available for the application of PV systems was manually measured to exclude unusable
available for the application of PV systems was manually measured to exclude unusable
areas.
areas.
Energies 2023, 16, 3123
2.2. PV Module Spacing
2.2. PV Module Spacing
Two types of roofs with different appearances, named flat roofs and pitched roofs,
Two types of roofs with different appearances, named flat roofs and pitched roofs,
4 ofthe
18
have both been widely utilized in typical univerisity buildings depending on
have both been widely utilized in typical univerisity buildings depending on the
surrouding climate and building types. The schematic diagram of the a PV module
surrouding climate and building types. The schematic diagram of the a PV module
installed on a flat roof is shown in Figure 2. In this case, the PV module spacing is
installed on a flat roof is shown in Figure 2. In this case, the PV module spacing is
sun’s
azimuth
angle
3 pmazimuth
on the local
winter
solstice
in order
to minimize
theinimpact
calculated
using
theatsun’s
angle
at 3 pm
on the
local winter
solstice
order of
to
calculated using the sun’s azimuth angle at 3 pm on the local winter solstice in order to
mutual
shading
among
modules
[19]:among PV modules [19]:
minimize
the impact
of PV
mutual
shading
minimize the impact of mutual shading among PV modules [19]:
𝑠𝑖𝑛 𝜀
𝑠𝑖𝑛 cosϕ
𝜀 𝑐𝑜𝑠𝜑
𝐷 f = 𝐿Lcosε
𝑐𝑜𝑠 𝜀+ L𝐿sinε
(1)
D
(1)
𝐷
𝐿 𝑐𝑜𝑠 𝜀 𝐿tanβ
(1)
𝑡𝑎𝑛𝛽 𝑐𝑜𝑠𝜑
𝑡𝑎𝑛𝛽
is the spacing
spacing between adjacent
adjacent PV modules installed
installed on
on aa flat
flat roof,
roof, m; LL isisthe
the
where Df is
where
the spacing between
between adjacent PV modules
modules
roof, m;
m; L is the
where D
Dff is the
length
of
a
PV
module,
m;
ε
is
the
title
angle
of
PV
array,
°;
β
is
the
sun’s
altitude
angle
at
◦
length
; ββis
length of
of aa PV
PV module,
module, m;
m; εεisisthe
thetitle
titleangle
angleof
ofPV
PVarray,
array, °;
is the
the sun’s
sun’s altitude
altitude angle
angle at
at
3
pm
on
the
winter
solstice,
°;
φ
is
the
sun’s
azimuth
angle
at
3
pm
on
the
winter
solstice,
°.
◦
◦
33 pm
solstice, °; ;φϕisisthe
thesun’s
sun’sazimuth
azimuthangle
angleatat3 3pm
pm
the
winter
solstice,
pm on the winter solstice,
onon
the
winter
solstice,
°. .
Figure 2. Schematic diagram of PV modules installated on a flat roof.
Figure 2.
2. Schematic
Schematic diagram
diagram of
of PV
PV modules
modules installated
installated on
onaa flat
flatroof.
roof.
Figure
As shown in
in Figure 3,
3, a pitched roof
roof isaaroof
roof comprisingaasloping
sloping surface with
with an
As
As shown
shown in Figure
Figure 3, aa pitched
pitched roof is
is a roof comprising
comprising a sloping surface
surface with an
an
angle
usually
over
20
degrees
relative
to
the
ground.
In
this
case,
the
spacing
between
two
angle
angle usually
usually over
over 20
20 degrees
degrees relative
relativeto
tothe
the ground.
ground. In
In this
this case,
case, the
the spacing
spacing between
between two
two
adjacent PVmodules
modules
installed
on
a pitched
roof
can
be expressed
by the following
adjacent
installed
on aon
pitched
roof can
be can
expressed
by the following
equation:
adjacentPV
PV modules
installed
a pitched
roof
be expressed
by the following
equation:
equation:
sinε
− tanθtanβ
)
𝑠𝑖𝑛 (𝜀cosϕ
𝑐𝑜𝑠𝜑
𝑡𝑎𝑛 𝜃𝑡𝑎𝑛𝛽
Db = Lcosε + L 𝑠𝑖𝑛
(2)
𝜀
𝑐𝑜𝑠𝜑
𝑡𝑎𝑛 𝜃𝑡𝑎𝑛𝛽
(2)
𝐷
𝐿 𝑐𝑜𝑠 𝜀 𝐿 tanβ − cosϕtanθ
(2)
𝐷
𝐿 𝑐𝑜𝑠 𝜀 𝐿
𝑡𝑎𝑛𝛽 𝑐𝑜𝑠 𝜑 𝑡𝑎𝑛 𝜃
𝑡𝑎𝑛𝛽 𝑐𝑜𝑠 𝜑 𝑡𝑎𝑛 𝜃
where
roof,
m;m;
θ is𝜃
thespacing
spacingbetween
betweenadjacent
adjacentsolar
solarmodules
modulesinstalled
installedonona apitched
pitched
roof,
whereDDbbisisthe
is the spacing
between
adjacent
solar
where
Db between
◦ . modules installed on a pitched roof, m; 𝜃
the
angle
the
roof
and
the
ground,
is the angle between the roof and the ground, °.
is the angle between the roof and the ground, °.
Figure
Figure3.3. Schematic
Schematicdiagram
diagramof
ofPV
PVmodules
modulesinstallated
installatedon
onaapitched
pitchedroof.
roof.
Figure 3. Schematic diagram of PV modules installated on a pitched roof.
2.3. Potential Capacity and Working Eficiency of PV System
2.3. Potential Capacity and Working Eficiency of PV System
2.3. Potential
Capacity
and Working
EficiencyPV
of PV
System
The potential
capacity
of the installed
system
(kW) can be expressed as:
The potential capacity of the installed PV system (kW) can be expressed as:
The potential capacity of the installed
PV system (kW) can be expressed as:
area
potential
Capacity
==
××PF
Capacity
PF××PP
Capacity = area PV
× PF × P
(3)
(3)
(3)
where packingfactor
factor PFisisthe
the ratioofofPV
PV arrayarea
area to theoccupied
occupied roof
area; area
potentialis
is
where
potential
wherepacking
packing factorPF
PF is theratio
ratio of PVarray
array
areatotothe
the occupiedroof
roofarea;
area;area
area
potential is
2; areaPV is the area of PV modules, m
2; and P is
the
potentially
available
area
of
the
roof,
m
2
2
the
the potentially
potentiallyavailable
availablearea
areaofofthe
theroof,
roof,mm;2;area
areaPV
PV is
is the
the area
area of
of PV
PV modules,
modules,m
m2;; and
and PP is
is
thewattage
wattageof
ofthe
thePV
PVmodules,
modules,W.
W.
the
the wattage of the PV modules, W.
The working efficiency of the installed PV system can be calculated using open-source
code OptiCE [24] by the following equation:
ηPV = ηPV −STC (1 +
µ
9.5
NOCT − 20
µ
(1 − ηPV −STC ) GT )
( Ta − TSTC ) +
ηPV −STC
ηPV −STC 5.7 + 3.8v
800
(4)
where ηPV is the actual working efficiency of the PV module, %; ηPV −STC is the working
efficiency of the PV module under standard working conditions, %; µ is the temperature
coefficient, %/◦ C; Ta is the ambient temperature, ◦ C; TSTC is the temperature of the PV
Energies 2023, 16, 3123
5 of 18
module under standard working conditions, ◦ C; v is the actual wind speed, m/s; and
NOCT is the nominal operating cell temperature, ◦ C.
The dependency of power generation of a PV system on the PV module efficiency can
be expressed by the following equation [17]:
Pi = area a × GT × ηBOS × ηPV
(5)
where Pi is the hourly PV output, kWh; areaa is the PV array area, m2 ; GT is the hourly
global incident solar irradiation, kWh/m2 ; and ηBOS is the balance of system efficiency, %.
The output of a PV system is deteriorated due to the aging of PV modules; the total output of the studied PV system over its lifetime can be calculated by the following equation:
25
EP25 = ∑i=1 EPi K i−1
(6)
where EP25 is the total output of the photovoltaic system during its lifetime, kWh; EPi is the
PV output in the first year, kWh; and K is the annual degeneration rate of the PV module,
taking 0.98 at the second year and 0.9945 for rest years in this study.
2.4. Economic Analysis
A variety of economic indicators have been used to investigate the economic performance of the PV systems, including life cycle cost (LCC), net present value (NPV), lifetime
net income (NI), return on investment (ROI), and LCOE.
The life cycle cost (CNY) of a photovoltaic system can be derived from the
following equation:
Cequipment,i +CO&M,i ×Capacity
25
LCC = ∑i=1
(7)
1.05i
where Cequipment,i is the unit equipment investment and replacement cost in year i, CNY;
CO&M,i is the Operations & Maintenance (O&M) cost in year i, CNY.
The PV system revenue during its lifetime can be expressed by:
25
Revenuek = ∑i=1
Epi × Pk
1.05i
(8)
where Revenuek is the lifetime income under scenario k, CNY; Pk is the electricity price
under scenario k, W.
Considering the discount at the given interest rate, the net present value (CNY) of the
PV system can be determined by Equation (9):
i
NPV i = ∑t=1
Ri
1.05i
(9)
The lifetime net income (CNY) can be calculated by Equation (10):
NI = Revenuek − LCCk
(10)
The return on investment refers to the effective returns that investment would generate
throughout the life of the solar PV system, which can be expressed by Equation (11):
ROI =
NI
× 100%
LCC
(11)
Energies 2023, 16, x FOR PEER REVIEW
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Energies 2023, 16, 3123
ROI =
NI
× 100%
LCC
6 of 18
(11)
The LCOE (CNY/kWh) is another metric that is frequently used to assess the
Theviability
LCOE (CNY/kWh)
anotherwhich
metriccan
that
frequently used
assess the(12):
economic
economic
of solar PVissystem,
beisdetermined
usingtoEquation
viability of solar PV system, which can be determined using Equation (12):
Cequipment,i CO&M,i
Capacity
25
LCC ∑i 1 25 {(Cequipment,i1.05
i
+CO&M,i
× Capacity}
)
LCOE
∑ i =1
LCC
25
i 1i
1.05
E
∑
E
K
LCOE = p25 =
i 1 Pi
E p25
i −1
∑25
i =1 EPi K
(12)
(12)
3. 3.
Study
Case
Study
Case
The
efficiency,
Thepower
powergeneration
generation
efficiency,the
thelocation,
location,and
andthe
thearray
arraylayout
layoutofofPV
PVsystems
systems
depends
on
the
solar
radiation
received
on
the
solar
panel
surfaces.
Due
to
a
depends on the solar radiation received on the solar panel surfaces. Due to avast
vastland
land
mass
with
diverse
meteorological
conditions,
four
major
solar
radiation
zones
have
been
mass
with
diverse
meteorological
conditions,
four
major
solar
radiation
zones
have
been
identified
from
Zone
I toI to
Zone
IV IV
in China
for targeting
solarsolar
energy
utilization
[25]. [25].
In
identified
from
Zone
Zone
in China
for targeting
energy
utilization
order
to evaluate
the technical
feasibility
and economic
benefit
of university
campus
PV
In order
to evaluate
the technical
feasibility
and economic
benefit
of university
campus
systems,
Tibet Tibet
University
in Lhasa
City,City,
Qinghai
University
in Xining
City,
and
PV systems,
University
in Lhasa
Qinghai
University
in Xining
City,
andQilu
Qilu
University
of
Technology
in
Jinan
City
are
selected
as
study
cases,
with
the
location
and
University of Technology in Jinan City are selected as study cases, with the location and
satellite
images
shown
inin
Figure
4.4.
Zone
IVIV
is is
not
taken
into
account
inin
the
present
study
satellite
images
shown
Figure
Zone
not
taken
into
account
the
present
study
◦ N,
due
totoless
coordinates
ofof
three
selected
universities
are
(29.647°
due
lesssolar
solarradiation.
radiation.The
The
coordinates
three
selected
universities
are
(29.647N,
◦
◦
◦
◦
◦
91.146E),E),(36.728°
(36.728 N,N,101.747°
101.747 E),
E),and
and(36.559°
(36.559 N,
N,116.804°
116.804 E),
E), representing
representing Zone
91.146°
Zone I,I,Zone
ZoneII,
II,and
andZone
ZoneIII
IIIirradiation
irradiationareas
areasininChina,
China,respectively.
respectively.
Figure 4. Location and satellite images of Tibet University, Qinghai University, and Qilu University
Figure 4. Location and satellite images of Tibet University, Qinghai University, and Qilu University
Technology.
ofof
Technology.
The main meteorological parameters of the three studied university are shown in
The main meteorological parameters of the three studied university are shown in
Figure 5. The annual outdoor average temperature at Tibet University, Qinghai UniverFigure 5. The annual outdoor average temperature
at Tibet University, Qinghai
sity, and Qilu University of Technology is 9.4 ◦ C, 6.3 ◦ C, and 14.9 ◦ C, respectively. The
University, and Qilu University of Technology is 9.4 °C, 6.3 °C, and 14.9 °C, respectively. 2
annual global horizontal irradiation of above three universities reaches 1983 kWh/m
,
The annual global
horizontal irradiation
of above three universities reaches 1983 kWh/m2,
2
2
1576 kWh/m , and 1342 kWh/m , respectively. It can be obviously observed that, Tibet
1576 kWh/m2, and 1342 kWh/m2, respectively. It can be obviously observed that, Tibet
University has the most solar irradiation, followed by Qinghai University and Qilu UniUniversity has the most solar irradiation, followed by Qinghai University and Qilu
versity of Technology, which is consistent with their located solar radiation zones. Tibet
University of Technology, which is consistent with their located solar radiation2zones.
University has the highest monthly global horizontal radiation of 228 kWh/m in June
Tibet University has the highest monthly2 global horizontal radiation of 228 kWh/m2 in
and the lowest radiation of 116 kWh/m in February. Both Qinghai University and Qilu
University of Technology reach the highest irradiation values in May with 181 kWh/m2
and 165 kWh/m2 , and the lowest irradiation levels in December with 74 kWh/m2 and
56 kWh/m2 , respectively.
radiation of 116 kWh/m2 in February. Both Qinghai University and Qilu University of
Technology reach the highest irradiation values in May with 181 kWh/m2 and 165
7 of 18
2,
kWh/m2, and the lowest irradiation levels in December with 74 kWh/m2 and 56 kWh/m
respectively.
Energies 2023, 16, 3123
Monthly global radiation in Tibet University
Monthly global radiation in Qinghai University
Monthly global radiation in Qilu University of Technology
Monthly temperature in Tibet University
Monthly temperature in Qinghai University
Monthly temperature in Qilu University of Technology
35
250
30
25
20
150
15
10
100
5
Temperature (℃)
Solar Radiation (kWh/m2)
200
0
50
-5
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
-10
Month
Figure 5.
meteorological
parameters
in three
campuses
(data source
Reference
Figure
5. Main
Main
meteorological
parameters
in university
three university
campuses
(datafrom
source
from
[26]).
Reference [26]).
The technical
technical feasibility
crucial
forfor
thethe
installation
of PV
The
feasibilityand
andeconomic
economicevaluation
evaluationare
are
crucial
installation
of
systems
[27].
Taking
improvement
of
the
technical
performance
into
consideration,
emPV systems [27]. Taking improvement of the technical performance into consideration,
bedding solar
trackers
into into
the PV
is an effective
strategy
to improve
the irradiaembedding
solar
trackers
thesystems
PV systems
is an effective
strategy
to improve
the
tion utilization
[26]. However,
solar trackers
also increase
the construction
cost and cost
ecoirradiation
utilization
[26]. However,
solar trackers
also increase
the construction
nomic
expenseexpense
of the relevant
PV systems.
If a PV system
with solar
trackers
and
economic
of the relevant
PV systems.
If a PV embedded
system embedded
with
solar
is installed
at an angle
of angle
more than
15° than
the roof
needs
to be
adjusted,
resulting
trackers
is installed
at an
of more
15◦ tilt
theangle
roof tilt
angle
needs
to be adjusted,
in an increase
the installation
cost [28]. cost
Therefore,
PV systems
with solar
resulting
in an in
increase
in the installation
[28]. Therefore,
PVembedded
systems embedded
◦
trackers
are
generally
mounted
at
an
angle
of
less
than
15°
and
on
relatively
flat
ground
with solar trackers are generally mounted at an angle of less than 15 and on relatively
[29].ground
In this study,
considering
balance between
technical
performance
and
economical
flat
[29]. In
this study,the
considering
the balance
between
technical
performance
evaluation,
seven
installationseven
scenarios
for PV systems
on flat and
pitched
and
economical
evaluation,
installation
scenariosmounted
for PV systems
mounted
onroofflat
and
rooftops
proposed
investigate
the optimal
of the studied
topspitched
are proposed
to are
investigate
thetooptimal
configuration
ofconfiguration
the studied university
camuniversity
campuses.
puses.
Scenario
onon
flatflat
rooftop
at the
optimal
tilt angle
without
adjustment;
ScenarioA:
A:PV
PVsystem
systemfixed
fixed
rooftop
at the
optimal
tilt angle
without
adjustScenario
B:
PV
system
fixed
on
flat
rooftop
at
the
optimal
tilt
angle
with
biannual
adment;
justment,
corresponding
summer
and
optimal
tilt
Scenario
B: PV systemto
fixed
on flat optimal
rooftop attilt
theangle
optimal
tilt winter
angle with
biannual
angle,
respectively;
adjustment,
corresponding to summer optimal tilt angle and winter optimal tilt angle,
Scenario C: PV system fixed on flat rooftop at the optimal tilt angle with monthly
respectively;
adjustment;
Scenario C: PV system fixed on flat rooftop at the optimal tilt angle with monthly
Scenario
adjustment; D: PV system with single-axis tracking module installed on flat rooftop;
Scenario
tracking
module
installed
onon
flatflat
rooftop;
Scenario E:
D:PV
PVsystem
systemwith
withdual-axis
single-axis
tracking
module
installed
rooftop;
Scenario
F:
PV
system
installed
parallel
to
pitched
rooftop
without
adjustment,
Scenario E: PV system with dual-axis tracking module installed on flat rooftop;at the
roof pitch of 25◦ ;
Scenario G: PV system installed on pitched rooftop at the optimal tilt angle with
no adjustment.
In comparison with Scenario A, the installation cost and adjustment cost in the case of
scenarios B and C are increased by 0.06 CNY/W and 0.0045 CNY/W [30], respectively. In
Scenario A
Scenario B
Scenario C
Scenario D
Scenario E
Scenario F
Scenario G
3500
3000
Solar Radiation (kWh/m2)
Energies 2023, 16, 3123
Scenario F: PV system installed parallel to pitched rooftop without adjustment, at the
roof pitch of 25°;
Scenario G: PV system installed on pitched rooftop at the optimal tilt angle with no
adjustment.
8 of 18
In comparison with Scenario A, the installation cost and adjustment cost in the case
of scenarios B and C are increased by 0.06 CNY/W and 0.0045 CNY/W [30], respectively.
In comparison with Scenario A, the initial investment in case of scenarios D and E is
comparison
with and
Scenario
therespectively.
initial investment
case ofstudy,
scenarios
and E is increased
increased
by 25%
50% A,
[29],
In theinpresent
it isDassumed
that the
by
25%
and
50%
[29],
respectively.
In
the
present
study,
it
is
assumed
that
the maintenance
maintenance and operation costs under all scenarios are 1% of the initial investment
[31].
andConsidering
operation costs
all policy
scenarios
are 1%
the initial
investment
[31]. of the three
theunder
pricing
of the
PV of
system,
economic
benefits
Considering
policy
of the
the“full‐self‐consumption”
PV system, economic benefits
of the three
studied
universitiesthe
are pricing
evaluated
under
and “full‐feed‐into‐
studied
universities
are
evaluated
under
the
“full-self-consumption”
and
“full-feed-intogrid” modes. In the case of “full‐self‐consumption” mode, the electricity generated by the
grid”
modes.
In the case consumed
of “full-self-consumption”
mode,
electricity
by
PV
systems
is completely
by the universities.
Thethe
tariff
of Tibetgenerated
University,
the PV systems is completely consumed by the universities. The tariff of Tibet University,
Qinghai University, and Qilu University of Technology is calculated according to the local
Qinghai University, and Qilu University of Technology is calculated according to the local
residential electricity tariffs, which is 0.49 CNY [32], 0.3964 CNY [33], and 0.555 CNY [34],
residential electricity tariffs, which is 0.49 CNY [32], 0.3964 CNY [33], and 0.555 CNY [34],
respectively. For the “full‐feed‐into‐grid” mode, due to no PV subsidy after 2021,
respectively. For the “full-feed-into-grid” mode, due to no PV subsidy after 2021, electricity
electricity generated by the PV system is all sold to the national grid at local benchmark
generated by the PV system is all sold to the national grid at local benchmark price of solarprice of solar‐powered electricity of 0.1 CNY [35], 0.3247 CNY [36], 0.3949 CNY [35] for
powered electricity of 0.1 CNY [35], 0.3247 CNY [36], 0.3949 CNY [35] for Tibet University,
Tibet University, Qinghai University, and Qilu University of Technology, respectively.
Qinghai University, and Qilu University of Technology, respectively.
The comparison of irradiation data for the three studied universities under seven
The comparison of irradiation data for the three studied universities under seven
scenarios is shown in Figure 6. It can be observed that, most solar irradiation is obtained
scenarios is shown in Figure 6. It can be observed that, most solar irradiation is obtained
under Scenario E, that is, a PV system with a dual‐axis tracking module installed on a flat
under Scenario E, that is, a PV system with a dual-axis tracking module installed on a flat
rooftop. On a pitched rooftop, Scenario F and Scenario G almost obtain the same amount
rooftop. On a pitched rooftop, Scenario F and Scenario G almost obtain the same amount
ofofannual
annualirradiation,
irradiation,with
withscenario
scenarioGGbeing
beingslightly
slightlyhigher
higherthan
thanthat
thatofofscenario
scenarioF.F.
2500
2000
1500
1000
500
0
Tibet University
Qinghai University Qilu University of Technology
Location
Figure 6. Annual solar irradiation obtained by PV systems under seven scenarios (data source from
Figure 6. Annual solar irradiation obtained by PV systems under seven scenarios (data source from
Reference[26]).
[26]).
Reference
4. Results and Discussion
4.1. Utilizable Area for PV Application
LocaSpace Viewer is a 3D digital earth software which integrates images and terrain
online services such as Google Earth and TIANDITU, to achieve the rapid browsing,
measurement, analysis, and marking of 3D geospatial information data. In the present
study, potentially utilizable areas for PV system application in the three studied universities
are obtained by LocaSpace Viewer software, while the rooftop areas inappropriate for PV
system installation are manually excluded. The total coverage area of Tibet University,
Qinghai University, and Qilu University of Technology is 0.77 km2 , 1.09 km2 , and 1.26 km2 ,
respectively. The potentially available areas for PV systems in the three universities are
shown in Figure 7. Available flat rooftop areas of Tibet University, Qinghai University, and
Energies 2023, 16, 3123
measurement, analysis, and marking of 3D geospatial information data. In the present
study, potentially utilizable areas for PV system application in the three studied
universities are obtained by LocaSpace Viewer software, while the rooftop areas
inappropriate for PV system installation are manually excluded. The total coverage area
of Tibet University, Qinghai University, and Qilu University of Technology is 0.77 km2,
18
1.09 km2, and 1.26 km2, respectively. The potentially available areas for PV systems 9inofthe
three universities are shown in Figure 7. Available flat rooftop areas of Tibet University,
Qinghai University, and Qilu University of Technology are 104,741 m2, 105,360 m2, and
2 , and 42,797 m2 , accounting for
Qilu
University
of Technology
are96.67%,
104,741and
m2 ,71.25%
105,360ofmtotal
42,797
m2, accounting
for 96.75%,
available areas, respectively.
96.75%,
and 71.25%
of total available
areas,
respectively.
On therooftops
other hand,
the
On the 96.67%,
other hand,
the potentially
utilizable
areas
on the pitched
of Tibet
2, 6585 m2,
potentially
on theand
pitched
of Tibet
University,are
Qinghai
University,utilizable
Qinghai areas
University,
Qilurooftops
University
of Technology
3485 mUniversity,
2 , and 13,577 m2 , accounting for
and
University
of Technology
are 3485
m2 , 6585
andQilu
13,577
m2, accounting
for 3.22%,
3.33%,
andm28.75%
of total potential areas,
3.22%,
3.33%, and 28.75% of total potential areas, respectively.
respectively.
Figure7.7. Satellite
Satellite images
imagesand
and area
area identification
identificationof
ofstudied
studiedcases
casesvia
viamanual
manualscreening
screeningby
byLocaSpace
LocaSpace
Figure
Viewer:(a)
(a)Tibet
TibetUniversity;
University;(b)
(b)Qinghai
QinghaiUniversity;
University;(c)
(c)Qilu
QiluUniversity
UniversityofofTechnology.
Technology.
Viewer:
4.2.
4.2.Installed
InstalledCapacity
CapacityofofPV
PV Systems
Systems
The
PV
output
in
the
three
studied
university
campuses
are calculated
using using
the input
The PV output in the three
studied
university
campuses
are calculated
the
data
shown
in
Table
1.
input data shown in Table 1.
Table 1. Input data.
Table 1. Input data.
Parameters
Parameters
η pv-stc (%)
ηpv‐stc (%)
µ (%/◦ C)
μ
◦
TSTC ( C) (%/°C)
TSTC (°C)
NOCT (◦ C)
P (kW)
NOCT (°C)
η BOS (%)P (kW)
PV system lifetime (year)
Value
Value
19.5
19.5
−0.27
−0.27
25
25
20
0.355
20
80.56 0.355
25
The dimensions of the PV modules used in the present study are 1.755 m (L) ×
1.038 m (W) × 0.035 m (T). The shading effect of adjacent PV modules is simplified by
assuming that packing factors under scenarios B–E are the same as that under scenario
A. For plat rooftops in scenarios A–E, it is assumed that the shadows between adjacent
photovoltaic modules can be ignored. In scenarios A–E, the distance between adjacent
photovoltaic modules is calculated by Equation (1) to obtain the same intervals. Thus,
the potentially installed capacity of the photovoltaic system on the flat rooftops in Tibet
University, Qinghai University, and Qilu University of Technology is 11291 kW, 9102 kW,
and 3821 kW, respectively. For the pitched rooftops, the potentially installed capacity of PV
systems installed under scenario F and scenario G is different due to different installation
intervals between adjacent photovoltaic modules. Under scenario F, the potentially installed
Energies 2023, 16, 3123
10 of 18
capacity of the photovoltaic systems on the pitched rooftops in Tibet University, Qinghai
University, and Qilu University of Technology is 679 kW, 1283 kW, and 2645 kW, respectively.
Under scenario G, the potentially installed capacity of the photovoltaic systems on the
pitched rooftops in Tibet University, Qinghai University, and Qilu University of Technology
is 628 kW, 1117 kW, and 2455 kW, respectively.
Figure 8 is the PV output during lifetime of three studied universities under seven
scenarios. For the same university, the annual power generation and total power generation
within a 25-year lifetime under scenario E > scenario D > scenario C > scenario B > scenario
A, because the scenario E shows the highest radiation intensity per area under the condition
of the same PV-installed capacity. For flat rooftops under scenarios A–E, Tibet University
has the highest annual power generation, following by Qinghai University and Qilu
University of Technology. This can be attributed to the highest solar radiation intensity
and most flat rooftop areas in Tibet University. The maximum of 28.19 GWh, 18.03 GWh,
and 5.36 GWh of annual power generation capacity can be obtained in Tibet University,
Qinghai University, and Qilu University of Technology, respectively. Under scenario E,
the annual power generation and total power generation within 25-year lifetime of both
Tibet University and Qinghai University are the highest in comparison with another four
configurations, which can also be attributed to the highest solar radiation under scenario
Energies 2023, 16, x FOR PEER REVIEW
16 of 24E.
The same conclusion can be drawn for Qilu University of Technology, but the increase rate
is much lower than another two universities due to lower solar radiation.
Ep25 of Tibet University
Ep25 of Qinghai University
Ep25 of Qilu University of Technology
Ep of Tibet University
Ep of Qinghai University
Ep of Qilu University of Technology
1400
50
Ep25 (GWh)
1000
4
90
3
45
60
2
40
30
1
0
0
F
G
35
30
800
25
600
20
Ep (GWh)
1200
120
15
400
10
200
5
0
A
B
C
D
E
F
G
0
Scenario
Figure8.8.PV
PVoutput
outputunder
underseven
sevenscenarios
scenariosininthree
threestudied
studieduniversities.
universities.
Figure
Annual power generation and total power generation within a 25-year lifetime in
Annual
generation
total
power
generation
within
a 25-year
lifetime
scenarios F power
are slightly
higherand
than
those
in scenarios
G for
three
study cases
dueinto
scenarios
F
are
slightly
higher
than
those
in
scenarios
G
for
three
study
cases
due
to
higher
higher packing factor. Even though the solar radiation both in Tibet University and
packing
Even though
thethan
solarthat
radiation
in Tibet of
University
and the
Qinghai
UniQinghaifactor.
University
is higher
in Qiluboth
University
Technology,
area of
the
versity
is
higher
than
that
in
Qilu
University
of
Technology,
the
area
of
the
pitched
roofpitched rooftops in Qilu University of Technology is 3.90 times and 2.06 times of that in
tops
inUniversity
Qilu University
of Technology
is 3.90
times and 2.06
times of that in
UniverTibet
and Qinghai
University,
respectively.
As demonstrated
inTibet
Figure
8, Qilu
sity
and Qinghai
University,
respectively.
As demonstrated
ingeneration
Figure 8, Qilu
University
of Technology
presents
the highest
annual power
and University
total power
ofgeneration
Technology
presents
the highest
generation
power generation
within
25-year
lifetimeannual
for PVpower
systems
installedand
on total
the pitched
rooftops in
within
25-year
lifetime
for
PV
systems
installed
on
the
pitched
rooftops
in
scenarios
F and
scenarios F and G, followed by Qinghai University and Tibet University. When the
PV
G,systems
followed
by
Qinghai
University
and
Tibet
University.
When
the
PV
systems
are
inare installed parallel to the pitched rooftop under scenario F, the annual power
stalled parallel to the pitched rooftop under scenario F, the annual power generation of
Tibet University, Qinghai University, and Qilu University of Technology is 1.23 GWh, 1.88
GWh, and 3.11 GWh, respectively.
Energies 2023, 16, 3123
11 of 18
Energies 2023, 16, x FOR PEER REVIEW
17 of 24
generation of Tibet University, Qinghai University, and Qilu University of Technology
is
1.23 GWh, 1.88 GWh, and 3.11 GWh, respectively.
4.3. Lifetime Net Income of PV Systems
University are, respectively, located in solar Zone I and solar Zone II with relatively abun9 presents
the net
PV systems
the lifetime
in case
of “fulldant Figure
solar energy
resources
toincome
achieveofhigher
lifetimewithin
net income.
For PV
systems
inself-consumption”
mode
and
“full-feed-into-grid”
mode
of
three
study
cases,
respectively.
stalled in Qilu University of Technology located in solar Zone III, the lifetime net income
For thethe
same
study
case, the
lifetimewith
net another
income two
of PV
system
“full-selfwithin
lifetime
is lower
compared
study
casesinstalled
due to ainlimited
inconsumption”
mode
is
far
higher
than
that
in
“full-feed-into-grid”
mode
due
to
higher
crease in solar radiation and high tracking investment. The highest lifetime net income
residential
electricity
lifetimeare
netinstalled
income in
of “full-self-consumption”
PV systems installed inmode
Tibet
can
be achieved
at andtariff.
when The
PV systems
University
even
becomes
negative
in
the
case
of
“full-feed-into-grid”
mode
because
the
for Tibet University, Qinghai University, and Qilu University of Technology, respectively.
local benchmark price of solar-powered electricity in Tibet is as low as 0.1 CNY/kWh.
Tibet University: full-self-consumption
Qinghai University: full-self-consumption
Qilu University of Technology: full-self-consumption
Tibet University: full-feed-into-grid
Qinghai University: full-feed-into-grid
Qilu University of Technology: full-feed-into-grid
Lifetime net income (million CNY)
160
20
10
120
0
80
-10
F
40
G
0
-40
A
B
C
D
E
F
G
Scenario
Figure9.
9.Lifetime
Lifetimenet
netincome
income of
of PV
PV systems
systems in
in the
the three
three studied universities under seven scenarios.
Figure
scenarios.
As demonstrated in Figure 9, for PV systems installed on the flat rooftops, both Tibet
University
Qinghai
University
have
the highest
lifetime
net income
under
scenario
For PVand
systems
installed
on the
pitched
rooftops
in scenarios
F and
G, the
highestE
with
biaxial
tracking
system
in
comparison
with
another
four
scenarios,
corresponding
to
lifetime net income can be achieved under scenario F for all three study cases, except the
117.85
million
CNY
and
42.33
million
CNY,
respectively.
However,
PV
systems
installed
in
PV systems installed in “full-feed-into-grid” mode in Tibet University. Although scenario
Qilu
University
of
Technology
shows
the
highest
lifetime
net
income
at
18.56
million
CNY
F has features of slightly lower solar radiation and higher investment cost compared to
under scenario
B whennet
theincome
tilt angle
is adjusted
every
halfhigher
a year.than
Compared
to scenario
scenario
G, the lifetime
under
scenario
F is still
that under
scenarioB,
the
biaxial
tracking
system
in
scenario
E
enhances
the
utilization
rate
of
solar
radiation
at
G, attributed to its higher installed capacity for PV systems and more generated electricity.
the
cost
of
increasing
equipment
investment.
Tibet
University
and
Qinghai
University
are,
When the PV systems are installed parallel to the pitched rooftop under scenario F, the
respectively,
locatedofinTibet
solarUniversity,
Zone I and Qinghai
solar Zone
II with relatively
abundant
solar
lifetime
net income
University,
and Qilu
University
ofenergy
Techresources
to
achieve
higher
lifetime
net
income.
For
PV
systems
installed
in
Qilu
University
nology is 5.33 million CNY, 4.83 million CNY, and 12.58 million CNY, respectively.
of Technology located in solar Zone III, the lifetime net income within the lifetime is lower
compared
with
another of
two
cases due to a limited increase in solar radiation and
4.4.
Return on
Investment
PVstudy
Systems
high tracking investment. The highest lifetime net income can be achieved at and when
Figure 10 presents the return on investment of PV systems under seven scenarios in
PV systems are installed in “full-self-consumption” mode for Tibet University, Qinghai
three
universities. Under seven scenarios, the ROI of PV systems installed in “full-selfUniversity, and Qilu University of Technology, respectively.
consumption”
mode installed
is alwayson
higher
in comparison
“full-feed-into-grid”
mode,
For PV systems
the pitched
rooftops with
in scenarios
F and G, the highest
which
can
be
attributed
to
the
fact
that
the
local
benchmark
price
of
solar-powered
eleclifetime net income can be achieved under scenario F for all three study cases, except
the
tricity is lower than the residential electricity tariff when the above two modes have the
same power generation capacity. Furthermore, the highest ROI can be achieved at 208%
and 101% under scenario B when the tilt angle is adjusted twice every year for both Tibet
Energies 2023, 16, 3123
12 of 18
PV systems installed in “full-feed-into-grid” mode in Tibet University. Although scenario
F has features of slightly lower solar radiation and higher investment cost compared
to scenario G, the lifetime net income under scenario F is still higher than that under
scenario G, attributed to its higher installed capacity for PV systems and more generated
electricity. When the PV systems are installed parallel to the pitched rooftop under scenario
F, the lifetime net income of Tibet University, Qinghai University, and Qilu University of
Technology is 5.33 million CNY, 4.83 million CNY, and 12.58 million CNY, respectively.
4.4. Return on Investment of PV Systems
Figure 10 presents the return on investment of PV systems under seven scenarios in
three universities. Under seven scenarios, the ROI of PV systems installed in “full-selfconsumption” mode is always higher in comparison with “full-feed-into-grid” mode, which
can be attributed to the fact that the local benchmark price of solar-powered electricity is
Energies 2023, 16, x FOR PEER REVIEW
of 19
lower than the residential electricity tariff when the above two modes have the same13power
generation capacity. Furthermore, the highest ROI can be achieved at 208% and 101%
under scenario B when the tilt angle is adjusted twice every year for both Tibet University
and Qinghai to
University.
Low frequency
of PV
modules
corresponds
corresponds
low operation
cost; thus,adjustment
PV systems
installed
under
scenario to
B low
can
operation
cost;
thus,
PV
systems
installed
under
scenario
B
can
effectively
utilize
the
effectively utilize the solar radiation of these two zones to enhance the ROI. For solar
Qilu
radiation ofof
these
two zoneslocated
to enhance
the ROI.
of can
Technology
located
University
Technology
in solar
ZoneFor
III,Qilu
the University
highest ROI
be obtained
at
in
solar
Zone
III,
the
highest
ROI
can
be
obtained
at
124%
under
scenario
A
thanks
to
124% under scenario A thanks to the lowest investment cost in comparison with other
the lowestWhen
investment
cost
comparison
other on
scenarios.
When
it comes
tohighest
the PV
scenarios.
it comes
toin
the
PV systemswith
installed
the pitched
rooftops,
the
systems
installed
on
the
pitched
rooftops,
the
highest
ROI
is
achieved
under
scenario
G
ROI is achieved under scenario G with the lowest PV system capacity and the highest PV
with
the
lowest
PV
system
capacity
and
the
highest
PV
power
generation
per
capacity,
power generation per capacity, which is 204%, 99%, and 123% in Tibet University, Qinghai
which is 204%,
123% inof
Tibet
University,
Qinghai University, and Qilu University
University,
and99%,
Qiluand
University
Technology,
respectively.
of Technology, respectively.
Tibet University: full‐self‐consumption
Qinghai University: full‐self‐consumption
Qilu University of Technology: full‐self‐consumption
Tibet University: full‐feed‐into‐grid
Qinghai University: full‐feed‐into‐grid
Qilu University of Technology: full‐feed‐into‐grid
240%
Return on investment‐ROI
200%
160%
120%
80%
40%
0%
‐40%
‐80%
A
B
C
D
E
F
G
Scenario
Figure 10.
investment
of PV
in thein
three
universities
under seven
scenarios.
Figure
10. Return
Returnonon
investment
of systems
PV systems
thestudied
three studied
universities
under
seven
scenarios.
4.5. Levelized Cost of Electricity of PV Systems
Figure 11
shows
the levelized
cost of electricity of PV systems installed in three
4.5. Levelized
Cost
of Electricity
of PV Systems
universities under seven scenarios. Tibet University and Qinghai University have the
Figure 11 shows the levelized cost of electricity of PV systems installed in three
lowest levelized cost of electricity in Scenario B, and Qilu University of Technology has the
universities under seven scenarios. Tibet University and Qinghai University have the
lowest levelized cost of electricity in Scenario A. Under the same scenario, the LCOE of the
lowest levelized cost of electricity in Scenario B, and Qilu University of Technology has
the lowest levelized cost of electricity in Scenario A. Under the same scenario, the LCOE
of the PV systems installed in Qilu University of Technology is the highest, following by
Qinghai University and Tibet University, corresponding to the solar Zone III, II, and I,
respectively. The results indicate that the LCOE of the proposed PV systems becomes
Energies 2023, 16, 3123
13 of 18
PV systems installed in Qilu University of Technology is the highest, following by Qinghai
Energies 2023, 16, x FOR PEER REVIEW
14 of 19
University and Tibet University, corresponding to the solar Zone III, II, and I, respectively.
The results indicate that the LCOE of the proposed PV systems becomes higher with the
decrease in solar radiation.
Levelized cost of energy‐LCOE (CNY/kWh)
0.35
Tibet University
Qinghai University
Qilu University of Technology
0.30
0.25
0.20
0.15
0.10
A
B
C
D
E
F
G
Scenario
Figure11.
11.Levelized
Levelizedcost
costofofenergy
energyininthe
thethree
threestudied
studieduniversities
universitiesunder
underseven
sevenscenarios.
scenarios.
Figure
4.6. Net Present Value of PV Systems on Flat Rooftops
4.6. Net Present Value of PV Systems on Flat Rooftops
NPV of PV systems is mainly affected by the cost, solar radiation, residential electricity
NPV
PVfactors.
systems
is mainly
affected
cost, under
solar five
radiation,
residential
tariff,
and of
other
Figure
12 is the
NPV ofby
PVthe
systems
scenarios
installed
electricity
tariff,
and
other
factors.
Figure
12
is
the
NPV
of
PV
systems
under
five
scenarios
on the flat rooftops of three universities. Obviously, under the same scenario, the
payback
installed
the
flat rooftops
ofself-consumption”
three universities. Obviously,
under
the same
the
period ofonPV
systems
in “full
mode is always
shorter
thanscenario,
that in “fullpayback
period
of
PV
systems
in
“full
self‐consumption”
mode
is
always
shorter
than
that
feed-into-grid” mode for all three studied universities. As shown in Figure 12a, the NPV of
inPV“full‐feed‐into‐grid”
for all three
studiedpositive
universities.
As shown in Figuremode,
12a,
systems installed in mode
Tibet University
is always
in “full-self-consumption”
the
NPV
of
PV
systems
installed
in
Tibet
University
is
always
positive
in
“full‐self‐
which indicates that the PV systems can recover investment in the first year. However, as
consumption”
mode,
indicatesnegative
that the for
PVPV
systems
caninstalled
recover in
investment
in the
shown in Figure
12b,which
NPV becomes
systems
Tibet University
first
year.
However,
as
shown
in
Figure
12b,
NPV
becomes
negative
for
PV
systems
due to a too-low local benchmark price of solar-powered electricity in “full-feed-into-grid”
installed
Tibet
Universityform
due Figure
to a too‐low
local
of solar‐powered
mode. Itincan
be observed
12c that,
thebenchmark
NPV of PVprice
systems
changes from
electricity
in positive
“full‐feed‐into‐grid”
It can
observed
form
Figure 12c
that,
NPV
negative to
during Year mode.
6–8 based
onbethe
scenarios,
indicating
that
thethe
payback
of
PV systems
changesinstalled
from negative
positiveinduring
Year
6–8 based
scenarios,
period
of PV systems
on flatto
rooftops
Qinghai
University
is on
6–8the
years
in “fullindicating
that the mode.
payback
period 12d,
of PV
rooftops
in Qinghai
self-consumption”
In Figure
thesystems
paybackinstalled
period ofon
theflat
same
university
becomes
University
is
6–8
years
in
“full‐self‐consumption”
mode.
In
Figure
12d,
the
payback
8–11 years in “full-feed-into-grid” mode. The same trend can be observed in Qilu University
period
of the same
becomes
in “full‐feed‐into‐grid”
mode.isThe
of Technology,
butuniversity
the payback
period8–11
of PVyears
systems
installed on flat rooftops
5–8same
years
trend
can years
be observed
in Qilu University of
Technology,
but the payback
period of PV
and 8–13
in “full-self-consumption”
and
“full-feed-into-grid”
mode, respectively.
systems installed on flat rooftops is 5–8 years and 8–13 years in “full‐self‐consumption”
and “full‐feed‐into‐grid” mode, respectively.
Energies 2023, 16, x FOR PEER REVIEW
Energies 2023, 16, 3123
14 of 18
120
100
20
Scenario A
Scenario B
Scenario C
Scenario D
Scenario E
(a)
Net present value‐N PV (million CNY)
Net present value‐NPV (million CN Y)
140
80
60
40
20
0
5
10
15
20
10
0
Scenario A
Scenario B
Scenario C
Scenario D
Scenario E
‐10
‐20
‐30
‐40
‐50
25
(b)
5
10
Year
Net present value‐NPV (million CN Y)
45
40
35
30
35
(c)
Scenario A
Scenario B
Scenario C
Scenario D
Scenario E
30
Net present value‐NPV (million CN Y)
50
25
20
15
10
5
0
-5
25
20
Scenario A
Scenario B
Scenario C
Scenario D
Scenario E
5
10
15
20
15
10
5
0
‐5
‐10
‐20
25
5
10
Scenario A
Scenario B
Scenario C
Scenario D
Scenario E
10
5
0
‐5
5
15
(e)
15
‐10
10
15
Year
15
20
25
Year
Net present value‐N PV (million CNY)
Net present value‐NPV (million CN Y)
20
25
(d)
Year
25
20
‐15
-10
-15
15
Year
20
25
10
Scenario A
Scenario B
Scenario C
Scenario D
Scenario E
(f)
5
0
‐5
‐10
5
10
15
20
25
Year
Figure 12. Net present value of PV systems installed on the flat rooftops in the three studied
Figure 12. Net present value of PV systems installed on the flat rooftops in the three
universities under five scenarios: (a) “full-self-consumption” mode in Tibet University; (b) “fulluniversities under five scenarios: (a) “full‐self‐consumption” mode in Tibet University; (
feed-into-grid” mode in Tibet University; (c) “full-self-consumption” mode in Qinghai University;
feed‐into‐grid” mode in Tibet University; (c) “full‐self‐consumption” mode in Qinghai Un
(d) “full-feed-into-grid”
mode in Qinghai University;
(e) “full-self-consumption”
mode in Qilu Uni- mode
mode in Qinghai
University; (e) “full‐self‐consumption”
(d) “full‐feed‐into‐grid”
versity of Technology;
(f)
“full-feed-into-grid”
mode
in
Qilu
University
of
Technology.
University of Technology; (f) “full‐feed‐into‐grid” mode in Qilu University of Technology.
4.7. Net Present Value of PV Systems on Pitched Rooftops
4.7. Net Present Value of PV Systems on Pitched Rooftops
Figure 13 is the NPV of PV systems installed on the pitched rooftops of three universiFigure 13 is the NPV of PV systems installed on the pitched rooftops o
ties. Similarly, like in Figure 12, the payback period of PV systems in “full self-consumption”
universities. Similarly, like in Figure 12, the payback period of PV systems in “f
mode is still always shorter than that in “full-feed-into-grid” mode for all three studied
consumption” mode is still always shorter than that in “full‐feed‐into‐grid” mod
universities both under scenarios F and G. In “full self-consumption” mode, the payback
three studied universities both under scenarios F and G. In “full self‐consumption”
period for PV systems installed in Tibet University, Qinghai University, and Qilu University
payback
period
for5PV
systems
installedInin“full-feed-into-grid
Tibet University, Qinghai
of Technology isthe
1 year,
6–7 years,
and
years,
respectively.
“ mode, Univers
Qilu
University
of
Technology
is
1
year,
6–7
years,
and
5
years,
respectively.
the payback period for PV systems installed in Qinghai University and Qilu University In “fu
“ mode,Figure
the payback
period
forNPV
PV systems
installed
in Qinghai
of Technology isinto‐grid
both 8 years.
13b shows
that
is always
negative
for PV Univers
Qilu
University
of
Technology
is
both
8
years.
Figure
13b
shows
that
systems on pitched rooftops of Tibet University, due to a too-low local benchmark price
of NPV is
solar-powered electricity in “full-feed-into-grid” mode.
Energies 2023, 16, x FOR PEER REVIEW
Energies 2023, 16, 3123
15 of 18
for PV systems on pitched rooftops of Tibet University, due to a too-low local benchmark
price of solar-powered electricity in “full-feed-into-grid” mode.
6
Scenario F
Scenario G
5
4
3
2
1
0
1
(a)
Net present value-NPV (million CNY)
Net present value-NPV (million CNY)
21 of 24
5
10
15
20
(b)
0
-1
-2
25
Scenario F
Scenario G
5
10
Net present value-NPV (million CNY)
5
Scenario F
Scenario G
4
3
2
1
0
-1
-2
4
(c)
Net present value-NPV (million CNY)
6
10
15
20
2
1
0
-1
25
5
10
Net present value-NPV (million CNY)
Net present value-NPV (million CNY)
8
(e)
10
5
0
10
15
Year
15
20
25
Year
Scenario F
Scenario G
5
25
(d)
Scenario F
Scenario G
Year
15
20
3
-2
5
15
Year
Year
20
25
(f)
Scenario F
Scenario G
6
4
2
0
-2
-4
5
10
15
20
25
Year
Figure
present
value
of PV
systems
on the
pitched
rooftops
in the
three
studied
universities
Figure
13. 13.
NetNet
present
value
of PV
systems
on the
pitched
rooftops
in the
three
studied
universities
under
scenarios:
“full-self-consumption”
mode
in Tibet
University;
“full-feed-into-grid”
under
twotwo
scenarios:
(a) (a)
“full-self-consumption”
mode
in Tibet
University;
(b) (b)
“full-feed-into-grid”
mode
in Tibet
University;
(c) “full-self-consumption”
in Qinghai
University;
(d) “full-feedmode
in Tibet
University;
(c) “full-self-consumption”
mode mode
in Qinghai
University;
(d) “full-feed-intointo-grid”
mode
in
Qinghai
University;
(e)
“full-self-consumption”
mode
in
Qilu
University of
grid” mode in Qinghai University; (e) “full-self-consumption” mode in Qilu University of Technology;
Technology; (f) “full-feed-into-grid” mode in Qilu University of Technology.
(f) “full-feed-into-grid” mode in Qilu University of Technology.
5. Conclusions
5. Conclusions
Installing
solar
systems
extensively
utilizable
building
rooftops
of university
Installing
solar
PVPV
systems
on on
extensively
utilizable
building
rooftops
of university
campuses
only
transforms
existing
infrastructure
sources
of on-site
energy
campuses
notnot
only
transforms
thethe
existing
infrastructure
intointo
sources
of on-site
energy
generation,
boosts
university
to reach
carbon
reduction
targets.
Three
typical
generation,
butbut
alsoalso
boosts
thethe
university
to reach
carbon
reduction
targets.
Three
typical
universities
located
in different
zones
in China
are selected
as study
in order
universities
located
in different
solarsolar
zones
in China
are selected
as study
cases cases
in order
to
to investigate
the technical
potential
and economic
of PV
rooftop
PV in
systems
in uniinvestigate
the technical
potential
and economic
benefitsbenefits
of rooftop
systems
university
campuses.
versity campuses.
2 available
2 available
rooftops,approximately
approximately104,741
104,741m
m22,, 105,360 m
areas
1. 1. ForFor
flatflat
rooftops,
m2,2,and
and42,797
42,797mm
areare
identified
which
correspond
to the
maximum
annual
power
generation
of 28.19
areas
identified
which
correspond
to the
maximum
annual
power
generation
of
28.19 GWh, 18.03 GWh, and 5.36 GWh for PV systems in Tibet University, Qinghai
University, and Qilu University of Technology, respectively.
Energies 2023, 16, 3123
16 of 18
2.
3.
4.
For pitched rooftops, potentially utilizable areas for PV systems are 3485 m2 , 6585 m2 ,
and 13,577 m2 , corresponding to annual power generation of 1.23 GWh, 1.88 GWh, and
3.11 GWh in Tibet University, Qinghai University, and Qilu University of Technology,
respectively.
Taking both technical potential and economic assessment into consideration, universities located in solar Zone I and Zone II with rich solar radiation are recommended
to install PV systems under scenario E (PV system with dual-axis tracking module
installed on flat rooftop). Scenario B (PV system fixed on flat rooftop at the optimal
tilt angle with biannual adjustment) is recommended for PV systems installed in
university campuses located in solar Zone III with less solar radiation.
From the perspective of economic analysis, PV systems installed in “full
self-consumption” mode are superior to those installed in “full-feed-into-grid” mode
for all three study cases. The ROI are significantly affected by the scenarios, with the
highest value at 208%, 101%, and 124% for flat rooftops and 204%, 99%, and 123%
for pitched rooftops in Tibet University, Qinghai University, and Qilu University of
Technology, respectively. In “full-self-consumption” mode, the payback period of PV
systems on flat rooftops in above three universities is 1 year, 6–8 years, and 5–8 years,
respectively.
In the present study, the shading effect of adjacent PV modules is simplified by
assuming that packing factors under scenarios B–E are the same as that under scenario A,
which can be further improved in future work. In addition, the present study ignores the
uncertainty and fluctuation of PV power under “full-self-consumption” mode. Our future
work will consider integrating energy-storage technologies with rooftop PV systems to
balance between PV power generation and campus electricity. China is targeting for the
commitment of achieving its carbon emissions to peak before 2030 and achieving carbon
neutrality by 2060. This study can benefit universities to focus on solar PV applications
om existing building rooftops to move towards sustainability by obtaining energy from
the sun.
Author Contributions: X.Z.: conceptualization, methodology, formal analysis, methodology, validation, writing-original draft preparation; Y.L.: conceptualization, methodology, funding acquisition,
project administration, supervision, writing-review and editing; J.B.: resources, writing-review and
editing, validation; M.J.: methodology, supervision; Y.S.: validation; T.D.: funding acquisition,
validation. All authors have read and agreed to the published version of the manuscript.
Funding: The research was carried out with the financial support of Natural Science Foundation
of Shandong Province of China (No. ZR2020ME178), Science-Education-industry Integration Pilot
Project (2022PX100) of Qilu University of Technology (Shandong Academy of Sciences), and Young
Innovative Talents Introduction & Cultivation Program for Colleges and Universities of Shandong
Province (Granted by Department of Education of Shandong Province, Sub-Title: Innovative Research
Team of Advanced Energy Equipment).
Data Availability Statement: Data are contained within the article.
Conflicts of Interest: The authors declare that there is no conflict of interest.
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