Facade Integrated Photovoltaic Systems: Potential Applications for Commercial Building in Vietnam

Abstract

In this paper, we investigate the facade photovoltaic systems (facade PV) integrated into commercial building in Vietnam context. Comparing to the rooftop solar, the facade solar system can install a larger total number of solar panels on the vertical wall of building. In addition, it also helps to reduce the energy consumption of building by decreasing the workload for air condition system, lighting system. However, the comprehensive study of facade solar system is still lacking in Vietnam. Therefore, in this study we present the general design process of facade PV for building, including choosing suitable solar panel, facade PV wall, and propose softwares to simulate the result on photovoltaic energy production and building consumption. Our study will open a new room of applicating facade PV system for the commercial building in Vietnam.

Full text

Facade integrated Photovoltaic systems: Potential
applications for commercial building in Vietnam
Luan Duy Le Nguyen, Sang Dinh Ngoc, Dinh Truong Cong, Du Le Thuong,
Son Nguyen Van, Vu Nguyen Hoang Minh, and Ngoc Thien Le
Dept. of Urban Engineering
University of Architecture Ho Chi Minh City
Ho Chi Minh City, Vietnam
Abstract—In this paper, we investigate the facade photovoltaic
systems (facade PV) integrated into commercial building in
Vietnam context. Comparing to the rooftop solar, the facade
solar system can install a larger total number of solar panels
on the vertical wall of building. In addition, it also helps to
reduce the energy consumption of building by decreasing the
workload for air condition system, lighting system. However,
the comprehensive study of facade solar system is still lacking
in Vietnam. Therefore, in this study we present the general
design process of facade PV for building, including choosing
suitable solar panel, facade PV wall, and propose softwares
to simulate the result on photovoltaic energy production and
building consumption. Our study will open a new room of
applicating facade PV system for the commercial building in
Vietnam.
Index Terms—facade PV, facade wall, micro inverter configu-
ration, building-integrated photovoltaic (BIPV),
I. INTRODUCTION
Building-integrated photovoltaics (BIPV) has been consid-
ered as the best strategy to harness solar power and increase
building energy efficiency in recent years due to its potential
advantages: (1) low consumption of materials; (2) save labor
and O&M costs; (3) high performance of electricity genera-
tion; (4) efficient thermal insulation; and (5) good noise and
weather protection. Being a multifuctional technology which
transform buildings form energy consumptions into energy
producers, BIPV has been used as alternative constructive
and insulative materials for building envelopes or as a sup-
plementary power source of buildings. It is allowed to be an
energy-related part of all kinds of building such as residential
homes, commercial buildings, offices, schools, hospitals and
so on. Those useful applications and advantages have made
BIPV become one of the most rapid-developing segments in
renewable energy industry.
BIPV products are initially introduced into commercial
market in the early 1990s as an integrated material which can
be installed directly into the building roofs, shading devices,
skylight and facades. Passing almost 10 years-experience
to be assessed its economic value for trading [1] and 20
years in-research to overcome significant technical challenges
related to energy-conversion efficiency and structural form,
it is currently recognized to be a competitive solution with
This work was supported by the National Research Grant Program No.
RD-49-17 in 2017 from the Ministry of Construction, Vietnam
traditional photovoltaic panels. However, BIPV is still facing
with numerous shortcomings in comparison to conventional
photovoltaic panel system including: (1) higher investment
cost but lower efficiency; (2) more complex and requires
higher labour charges; (3) difficult to be implemented to exist-
ing buildings; and (4) requires more solar-related factors to be
concerned [2] (i.e. photovoltaic module temperature, shapes of
shading devices, solar irradiance, installation orientation and
angles, etc.). In addition, another big obstacle which prevents
BIPV penetrating into commercial market is social barriers.
Building owner has a tendency to conserve their culture of
building and does not willing to change them, especially in
cases of high-density cities.
From the urban’s points of view, among various challenges
that a city has to deal with, meeting the energy demand
and support urban energy transition are identified as the
most importances. Since the majority of old buildings in a
city cannot meet the energy performance requirements as
stipulated in current regulations; while the investment cost for
retrofitting those buildings to increase their energy efficiency
are still expensive but the need to retrofit them is increasing
dramatically in recent years, integration of a modern renewable
energy system is an urgent solution. At the same time, due
to the rapid development of economy worldwide, the energy
demand has jumped significantly and continuously by years in
all sectors in economy including old commercial buildings. It
is required to figure out reasonable strategies for dealing with
the increasing demand but do not damage the architectural,
structural, and cultural designs of building in cities. In this
case, an integrated alternative energy producer such as BIPV
could be considered.
Vietnam has a huge potential to harness solar power for
future demand with a year-round average direct normal irradi-
ance radiation (DNI) of 4to 5.2kWh.m2 per day in most areas
of country despite the differences between various locations
around the country. The estimated technical solar potential
is approximately 56,000 MWp. As of July 2018, Vietnam
Government has approved more than 70 solar projects with a
total capacity recorded as over 3,500 MWp; in which 1,342.5
MWp has been connected to the national grid, 1,126.6MWp
is under construction phase, 667 MWp has just finished their
groundbreaking and 835 MWp has recently approved. Also,
over 1,500 solar rooftop projects have been operated with

total capacity of 30 MWp, approximately. A recent conference
hosted by EVN on March 22nd 2019 informs that by June
2019, the total grid-connected capacity will reach about 4,244
MW. However, there is still no appearance of thin-film solar
power in Vietnam [3], [4].
There are two types of BIPV, named as rooftop PV and
facade PV systems [5]–[8]. While the former has been installed
for a long time in many cities in Vietnam, the latter one is still
in an initial phase. Facade PV system exploits the vertical wall
of building to install solar panel and hence deploys larger solar
panel area, hence it can gain more energy production [6]. Many
Asian countries have been attracted by the facade PV system
for BIPV in recent years [9]–[16]. In Vietnam, the Ministry of
Construction has supported research grant for applying BIPV
in building. However, the comprehensive study about applying
facade PV for commercial building in Vietnam is still limited.
In this paper, we propose the suitable components of the
PV system integrating to the wall of commercial building in
Vietnam to generate energy from the sun and also improve
the overall energy efficiency of buildings. In Section II, we
represent the thin-film technology and suggest the suitable
types for building in Vietnam. In Section III, we suggest the
type of solar panel and the PV wall for building. The inverter
configuration used for facade PV is considered in Section IV.
We also introduce the essential simulation softwares for plan-
ning and designing facade PV system and the overall building
energy simulating for BIPV in Section V. Finally, we conclude
our work and suggest further research in Section VI.
II. TH IN -FIL M SO LA R PH OTOVO LTAIC T EC HN OL OG Y
Traditional rigid photovoltaic panels have been proliferated
significantly in the market over the last decade with various
designs for multifunctional purposes such as smooth-plate,
roofing tiles, shading-mounting, exterior wall cladding, etc.
Most of traditional forms are designed to be mounted directly
onto architectural sub-devices or through a hard-frame before
attaching onto building’s elements. With a high mechanical
durability, the PV cells of traditional panel are allowed to
be made from crystalline silicon (c-Si). However, the rigidity
of these products has led to the increase of load-bearing
capacity of building elements. Therefore, many researches
in recent years have been made with focusing on flexible
forms of PV modules, (hereinafter called as thin-film solar
PV). Numerous publications have shown results that thin-
film technology has remarkable advantages over the traditional
silicon PV technology, including: (1) lower consumption of
materials; (2) independence from the lack of silicon supply;
(3) simple manufacturing process; and (4) simplified materials
handling; (5) lighter weight; and (6) more flexible. That is the
reason why thin-film solar PV has been used in a variety of
buildings.
The categorization of thin-film solar PV technologies can be
made according to manufacturing materials as: (1) amorphous
silicon (a-Si) thin-film; (2) cadmium telluride (CdTe) thin-film;
(3) copper indium gallium deselenide/sulfide (CIGS) thin-film;
and (4) silicon thin-film. In terms of market sharing and
commercial efficiency, all thin-film technologies are currently
accounted for 4.5% of the global total production (about 97.5
GWp) in 2017; in which CdTe, a-Si, and CIGS technology
is accounted for 2.3%,0.3%, and 1.9%, respectively. The
highest efficiency recorded from laboratory of thin-film is
22.9% for CIGS solar cells, while the practical number
recorded from commercial project is 19.2%. These numbers
for CdTe technology are 21% in lab and 18.6% in field test.
However, there is a forecast that the market sharing of thin-
film technology may reach around 38% of the total production.
Also, CIGS technology is expected to be more popular than
other PV technologies due to its higher efficiency and lower
manufacturing costs. Other thin-film technologies, due to its
outstanding advantages over conventional PV technologies,
will be put in further research to reduce manufacturing costs
by faster and cheaper manufacturing technologies in the future.
Vietnam is currently considered as one of the most dynamic
economy in the world. International trading promotion policies
of Vietnam Government in the last two decades has given
to its economy a huge opportunity for reaching almost the
most modern technologies in the world. Additionally, with
mentioned policy strategies to promote the penetration of solar
energy into the country energy market, Vietnam investors
have full rights to choose what technology they want for
their projects. However, in current context of solar thin-film
market, it is suggested to use a-Si and CIGS technology in
the conditions of Vietnam. In this paper, a simulation will be
made for thin-film technology.
III. DESIGN FACADE PV C OM PO NE NT S
A. PV panels
There are two types of PV panels that are suitable for
commercial building in Vietnam. Example of those panels is
given in Fig. 1.
1) PV cladding crystalline: PV cladding crystalline tech-
nology is ideal for the buildings that seek maximum energy
production, and are well oriented towards the sun. Crystalline
silicon technology is popularly used on canopy and skylight
applications, spandrels glass, solid walls, and guardrails. This
PV cladding has the same mechanical properties as a conven-
tional, architectural glass used in construction. However, in
addition, it also generates free and clean energy for building.
Currently, the crystalline silicon glass efficiency can go up to
16% [17].
2) PV cladding thin-film: The thin-film is ideal for many
building integrated solutions to produce transparent or opaque
solar PV panels, ideal for facades, canopies, skylights or
curtain walls. Some benefits of PV cladding thin-film are [18]:
•PV thin-film can operate to a high efficiency at non-
optimal angles;
•PV thin-film operates down to 10% of sunlight, hence
higher the number of hours over the year in which to
produce electricity providing a more consistent energy
yield. Thin-film alignment also makes panels less affected
by shading;

Fig. 1. Examples of facade PV panels. Left: Crystalline panel; Right: thin-film
panel.
•PV thin-film are less affected by high temperatures so do
not require ventilation for optimal operation;
B. Facade PV walls
From an energetic perspective, the envelope of building acts
as a buffer or mediator between the interior and the exterior
environment wall cladding system. The idea of facade PV
wall is that utilizing the envelope of building to integrate solar
panels. There are many typical types that are suitable for the
climate in Vietnam as below:
1) Facade PV glazing: The glazed PV laminates for roof
of building are often made by crystalline silicon cell with
adjusted spacing or by laser grooved thin-film which provides
filtered vision, encapsulated within glazed panels (Fig. 2(a)).
In commercial buildings they are often found in envelope
systems together with extruded aluminum frames. They can
be used as part of a semi-transparent roof, termed as skylight.
The transparent functional glass is replaced with PV glazed
panels, whilst the load-bearing part is equipped for the electric
wirings passages. The solar cell pattern and assembly provide
the proper solar and daylighting control replacing the tradi-
tional external louvers and defining a particular architectural
appearance for building. These structures typically combine
glass-glass PV laminates with adjustable light transmission,
stimulating the architectural design of light and shadow and
performing a fundamental role for the energy balance of the
building. Facade PV glazing can be recommended in flat roof,
pitched roof, and sometimes also in curved surfaces.
2) Curtain PV wall: A curtain PV wall is typically a
continuous building envelope system in which the outer walls
are non-structural (Fig. 2(b)). A curtain PV satisfies the
building envelope requirements such as load bearing, thermal
insulation, weatherproofing and noise reduction. Since PV is
integrated in a complex building skin system, when using
curtain walls, the energy parameters related to solar system
such as thermal and visual comfort are strictly related to the
PV design. Similarly to facade PV glazing, the transparent
functional layer is replaced with an active glazed panel includ-
ing PV, whilst the load-bearing part, represented by the PV
frame, is equipped for the electric wiring system. Different
technological solutions are included in this category such
as stick system with transforms, structural-sealant glazing,
suspended facade, or point fixed facade.
3) Rain-screen facade PV: This facade PV system typically
includes of a load-bearing sub-frame, an air gap and a cladding
panel. In summer, heat is dissipated due to the air cavity that
is naturally ventilated through the bottom and top openings.
This is the reason why it is also termed as cold-facade,
since it brings a cooling effect for the wall and improves the
efficiency of the PV modules. Many constructive models and
technological solutions are available for building. The solar
modules can be integrated as the outer of building cladding
like a conventional cladding system.
4) PV Accessories: Buildings always have solar acces-
sories integrated into the design. These components include
balconies, parapets, outdoor partitions, shading systems and
several other components. Among these, shading systems are
the most commonly used accessory. The control of the indoor
micro climate, usually requires the use of shading devices
aimed to select the solar radiation for ensuring the thermo-
hygrometric and visual wellbeing through a proper use of
the natural lighting. Shading devices may be of various type:
applied on roof or facade; external, interposed or internal; fix
or tracking (manually or electrically); vertical, horizontal or
oriented; curtain or blind; mobile screen or panels; with special
element (selective glass, solar thin-film, prismatic glass). Solar
panels can be easily laminated in these accessories to obtain
a perfect way to utilize the shadow function with energy
production.
IV. MIC RO INVERTER CONFIGURATION
Shading is the main issue to the facade PV system like other
PV systems. The shading of facade PV is unavoidable and
causes by many sources such as the trees, neighbor buildings
or even from the wall of building itself. Therefore, the string
inverter configuration which is common approach for rooftop
PV, is not applicable for facade PV system. Instead of this,
the micro-inverter configuration is a suitable approach since
the DC-AC conversion and maximum power point tracking
(MPPT) is performed at individual solar panel level, the loss
due to shading only one panel does not affect the overall
energy efficiency of system.
Figure 3 shows an example of micro-inverter configuration
for facade PV. Unlike the central inverter configuration, a
micro-inverter on the other hand, will take full advantage of the
production of each individual panel. Because micro-inverter
is integrated to the panel module. It will convert the power
generated by each panel to the grid voltage. The dimension of
micro-inverter is also smaller than others, for example Enphase
inverter in Fig. 4. In general, the benefits of using micro-
inverter are list as below:
•The core advantage of using micro inverter is that theo-
retically we can yield more solar electricity. The reason
for this is that there are slight differences in voltages
between solar panels. When the are in a string the voltage
is reduced to the value of the lowest voltage panel in the
string;

Fig. 2. Examples facade PV walls for building: (a) Facade PV glazing, (b) Curtain PV wall, (c) Rain-screen facade PV, and (d) PV Accessories [19].
Fig. 3. The micro-inverter configuration in facade PV system.
•If a facade PV system is facing multiple angles, meaning
that some panels are facing south, east, and west, then
micro-inverters are ready to produce energy. If we have
shading issues from trees or a large chimney, again micro-
inverters would be better than others. In these situations,
the solar panels will be producing different amounts
of electricity at different times of the day, but micro-
inverters will ensure harvest all of the energy;
•Optimizers are an option for standard inverters as well,
which function is very similarly to a micro-inverter.
With an optimizer, we have a standard inverter, but we
also have optimizers for each individual panel combating
production differences;
•Micro-inverters typically have 25 year warranties from
supplier while other inverters typically have 5or 10 years
warranty;
•Micro-inverters and the add-on optimizers both offer
an additional perk in system monitoring as well. With
either of these devices, the system has ability to track
the production of each individual panel, while with a
standard inverter only can track the production of the
whole system;
•If customer want to expand their PV system in future,
micro-inverters are easy to plug and run. Meanwhile, with
a standard inverter, it would be more costly to add another
full unit.
Fig. 4. Example of micro-inverter from Enphase manufacturer [20].
V. MODELLING FACADE PV S YS TEM
As mentioned in Section I, the benefits of facade PV are
not only from generated energy from the sun, but also from
the overall building energy consumption aspect. The facade
wall helps to reduce the heat transfer into the building, hence
reducing the energy load for Heating, ventilation, and air
conditioning (HVAC) system. Beside that, transparent solar
panel allows the nature light goes through, reduces the energy
for lighting system. Therefore, we have to take into account
these potential benefits in planning and designing facade PV
system for building. We propose to use the following guideline
for using softwares in order to fully understanding the impact
of facade PV to the building as below steps:
•Designing facade PV wall prototype: In this step the PV
designer have to choose the suitable prototype of wall for
solar panel. The suggest types are as mentioned in the
Subsection III-B. The consultants from architecture and
civil engineer are essential in this initial step in order to
search a final decision for facade PV system;
•Facade PV simulation: In this step the PV designer
uses simulators to estimate the generated energy from
facade PV system. The input parameters of simulator
include all the features of PV system such as solar rated
power, the number of solar panels, power rated of micro-
inverter, the number of installed micro-inverters, and also
the environment parameters like average solar radiation,

TABLE I
EXA MPL ES O F SUG GES TE D SIM UL ATORS F OR E ACH S TEP O F FACA DE PV
SYSTEM PLANNING AND DESIGNING.
Step Description proposed softwares
1Choosing facade PV wall
prototype for building
Autodesk 3D [22];
Google Sketchup [23];
Rhinoceros3D [24]
2 Facade PV system simulation PVSites [21]
3 Building energy simulation EnergyPlus [25];
Edge [26]
Fig. 5. Facade PV glazing simulation using PVSites tool [21].
shading condition. The output can be the daily energy
yield, monthly energy yield, or even yearly yield;
•Building energy simulation: In this final step, the energy
efficiency of facade PV system should be counted in the
overall energy building system to show the interaction
between this system to other mechanical and electrical
system in building.
Table I summaries our proposed simulators that we should
use to plan and design the facade PV system for building.
In particular, we recommend the PV designer to use PVSites
software [21] in the second step since currently only this tool
accepts the database of thin-film and transparent solar panels
for energy simulation.
VI. CO NC LU SI ON A ND F URT HER WORKS
Building-integrated photovoltaic (BIPV) is a new approach
for commercial building in Vietnam in order to obtain the
energy efficiency and increase the penetration of renewable
energy. The utilization of facade PV on wall has been proven
as an effective approach to gain solar energy. The cost of thin-
film panel is gradually decreasing while its efficiency nearly
equals to mono-crystalline and polycrystalline solar panels.
Hence, we believe that facade PV system will popular in
Vietnam in near future.
To further our research we plan to implement many field
test prototypes of facade PV system to gather real datasets and
evaluate the results between these prototypes and simulation
softwares.
REFERENCES
[1] P. Eiffert, “An economic appraisal of building-integrated photovoltaics,”
Ph.D. dissertation, School of Architecture, Oxford Brookes University,
1998.
[2] C. Peng, Y. Huang, and Z. Wu, “Building-integrated photovoltaics
(BI PV) in architectural design in china,” Energy and Buildings, vol. 43,
pp. 3592–3598, 2011.
[3] L. D. L. Nguyen, Power Demand Forecasting in Smart Grid System
– Case Study of Vietnam. MSc Thesis, 2014, school of Science and
Engineering, Teesside University.
[4] V. H. M. Nguyen, C. V. Vo, L. D. L. Nguyen, and B. T. T. Phan, “Green
scenarios for power generation in vietnam by 2030,” Engineering,
Technology and Applied Science Research, vol. 9, no. 2, pp. 3719–3726,
2019.
[5] G. Quesada, D. Rousse, Y. Dutil, M. Badache, and S. Hall´
e, “A com-
prehensive review of solar facades. opaque solar facades,” Renewable
and Sustainable Energy Reviews, vol. 16, no. 5, pp. 2820 – 2832, 2012.
[6] A. K. Shukla, K. Sudhakar, and P. Baredar, “A comprehensive review
on design of building integrated photovoltaic system,” Energy and
Buildings, vol. 128, pp. 99 – 110, 2016.
[7] A. H. Fanney, B. P. Dougherty, and M. W. Davis, “Short-term charac-
terization of building integrated photovoltaic panels,” Journal of Solar
Energy Engineering, vol. 125, no. 1, pp. 13–20, 2003.
[8] L. Sun, W. Hu, Y. Yuan, X. Cao, and B. Lei, “Dynamic performance of
the shading-type building-integrated photovoltaic claddings,” Procedia
Engineering, vol. 121, no. 1, pp. 930–937, 2015.
[9] E. M. Saber, S. E. Lee, S. Manthapuri, W. Yi, and C. Deb, “Pv
(photovoltaics) performance evaluation and simulation-based energy
yield prediction for tropical buildings,” Energy, vol. 71, pp. 588 – 595,
2014.
[10] P. K. Ng, N. Mithraratne, and H. W. Kua, “Energy analysis of semi-
transparent bipv in singapore buildings,” Energy and Buildings, vol. 66,
pp. 274 – 281, 2013.
[11] H. Yang, G. Zheng, C. Lou, D. An, and J. Burnett, “Grid-connected
building-integrated photovoltaics: a hong kong case study,” Solar En-
ergy, vol. 76, no. 1, pp. 55 – 59, 2004, solar World Congress 2001.
[12] J.-H. Yoon, J. Song, and S.-J. Lee, “Practical application of building in-
tegrated photovoltaic (bipv) system using transparent amorphous silicon
thin-film pv module,” Solar Energy, vol. 85, no. 5, pp. 723 – 733, 2011.
[13] C. Peng, Y. Huang, and Z. Wu, “Building-integrated photovoltaics (bipv)
in architectural design in china,” Energy and Buildings, vol. 43, no. 12,
pp. 3592 – 3598, 2011.
[14] H. Radhi, “Energy analysis of fac¸ade-integrated photovoltaic systems
applied to uae commercial buildings,” Solar Energy, vol. 84, no. 12, pp.
2009 – 2021, 2010.
[15] L. Bueno, M. Ibliha, B. Vizcarra, G. M. Chaudhry, and M. K. Siddiki,
Eds., Feasibility analysis of a solar photovoltaic array integrated on
fac¸ade of a commercial building, Proceedings of the IEEE 42nd Photo-
voltaic Special Conference. The address of the publisher: IEEE, 2015.
[16] R. J. Yang, “Overcoming technical barriers and risks in the application
of building integrated photovoltaics (BIPV): Hardware and software
strategies,” Automation in Construction, vol. 51, pp. 92–102, 2015.
[17] PV glass. https://www.onyxsolar.com/product-services/crystalline-pv-
glass, (accessed Nov. 15, 2018).
[18] Thinfilm PV glass. http://www.polysolar.co.uk/Technology/thin-film,
(accessed Nov. 15, 2018).
[19] SUPSI, “Building integrated photovoltaics: Product overview for solar
building skins,” Swiss BIPV Competence Centre and Solar Energy
Application Centre, SEAC, Tech. Rep., 2017.
[20] Enphase Microinverter. https://enphase.com/en-us/products-and-
services/microinverters, (accessed Nov. 15, 2018).
[21] PVsites. https://www.pvsites.eu/software/, (accessed Nov. 15, 2018).
[22] Autodesk 3 D. https://www.autodesk.com/products/3ds-max/overview,
(accessed Nov. 15, 2018).
[23] Google Sketchup. https://www.sketchup.com/, (accessed Nov. 15, 2018).
[24] Rhinoceros 3 D. https://www.rhino3d.com/6/features, (accessed Nov. 15,
2018).
[25] EnergyPlus. https://energyplus.net/, (accessed Nov. 15, 2018).
[26] Edge Simulation. https://www.edgebuildings.com/, (accessed Nov. 15,
2018).