Smart Energy Buildings: PV Integration and Grid Sensitivity for the

Case of Vietnam

Wolfram Heckmann

, Duc Nguyen Huu

, Dayana del Carmen Granford Ruiz

Siddhi Shrikant Kulkarni

and Van Nguyen Ngoc

Electric Power University, Hanoi, Vietnam

Fraunhofer IEE, Kassel, Germany

Keywords: Self-consumption, PV Facade Systems, Reactive Power, Feed-in Tariff, Battery Storage System, Electric

Vehicle, Cooling System, Distribution Grid, Energy Management System, Rooftop PV.

Abstract: The Vietnamese government is pushing for higher implementation of distributed photovoltaic (PV) generation

through various policies. Due to the decreasing trend in feed-in tariff (FIT) prices, self- consumption of energy

is an increasingly viable option. The increased PV penetration in the distribution grid also leads to changes in

the voltage profile on the distribution line, which needs to be regulated. The paper discusses a study where an

energy management system (EMS) is implemented for a commercial building in Hanoi after modelling the

respective generating units. As a next step in the study, the self-consumption behaviour of the building is

analyzed and the voltage regulation for a sample distribution grid in Vietnam is implemented.

1 INTRODUCTION

1.1 Status and Objectives of Renewable

Energy Integration in Vietnam and

Germany

In Vietnam, solar power is an increasingly attractive

electricity generating option for the country. Recent

reduction in investing cost, quick construction and

incentive policies from the government are

accelerating the development of PV power in total

capacity, number of projects and penetration rate.

Regarding solar power development in the urban

areas of Vietnam, rooftop PV systems have been

booming recently, especially at locations with high

solar irradiation. Compared to rooftop systems, PV

facade systems, although they have great potential, do

not get enough attention.

In Hanoi, by October 2020, 1,138 rooftop solar

power projects were installed, interconnected and

brought into operation with total capacity reaching 12

MWp, Vietnam Electricity Group Hanoi [EVN

Hanoi] (2021). By comparison, 1,672 customers

installed rooftop PV systems in Da Nang city,

comprising a total capacity of 20 MWp (by the end of

August 2020) as mentioned by Lam, Ky, Hieu and

Hieu (2021). However, the highest total installed

capacity was seen in Ho Chi Minh City with 365

MWp by the end of August 2021 (Vietnam

Electricity, 2021).

Noteworthy, most of the rooftop PV projects in

cities of Vietnam have less than 15 kWp in capacity.

In Hanoi, among 1,138 projects, only 79 projects have

the capacity of over 20 kWp. The number of projects

which have capacity higher than 100 kWp is 12, most

of which are concentrated in Thanh Tri and Dong Anh

districts and are mainly located on the roofs of large

factories (EVN Hanoi, 2021).

Additionally, in Vietnam, although the integration

of the distributed PV rooftop systems might promise

many technical and economic benefits, these systems

are mainly invested, installed, operated with the

purpose of self-consumption and selling surplus

electricity to the grid. Self-consumption is the share

of locally generated electricity that is consumed in

house as defined by Luthander, Widén, Nilsson and

Palm (2015). Most of these systems do not adopt

energy storage devices or only integrate small

capacity lead-acid batteries providing a small amount

of energy for power outages. This means that, surplus

PV electricity, which has uncertain and intermittent

characteristics, is injected into grid without caring for

its impacts on power quality as well as the distribution

system operation. The impacts might be more serious

Heckmann, W., Duc, N., Granford Ruiz, D., Kulkarni, S. and Van, N.

Smart Energy Buildings: PV Integration and Grid Sensitivity for the Case of Vietnam.

DOI: 10.5220/0011068900003203

In Proceedings of the 11th International Conference on Smart Cities and Green ICT Systems (SMARTGREENS 2022), pages 117-124

ISBN: 978-989-758-572-2; ISSN: 2184-4968

117

when a higher share of distributed PV generation

participates in the existing low voltage (LV) grid.

Germany aims at a climate-neutral system in

2050. For the electrical energy consumption, the

share of renewable generation in 2019 was about 42%

and the milestone for 2030 is set to 65% according to

the Federal Ministry for Economic Affairs and

Energy [BMWi] (2019), the objectives are currently

updated. According to a scenario developed by

Fraunhofer Cluster of Excellence ‘Integrated Energy

Systems’ [CINES] (2020), the installed PV capacity

has to increase by a factor of 4 from today to 200-300

GW in 2050 to achieve the political objectives. The

power demand will increase due to sector coupling

technologies, amongst others with electric vehicles

and decentralized heat pumps for residential purposes

(Fraunhofer CINES, 2020, p. 12). A high share of the

overall PV in Germany is residential and commercial

PV rooftop systems with a strong tendency in a

combination with battery systems to foster PV self-

consumption. In 2020, 184,000 PV systems with a

capacity of 4.8 GWp were registered according to the

Bundesverband Solarwirtschaft e.V. [BSW Solar]

(2021). Moreover, the number of installed home

storage systems increased by 88,000 to overall

272,000 as a result leading to 50% of the new

installed PV (capacity up to 10 kWp) combined with

a battery storage (capacity 7 kWh on average) (BSW

Solar, 2021 (2)). These trends mark potential

challenges for the distribution grid and, at the same

time, opportunities for energy management to

mitigate them.

1.2 Load Development in Urban Areas

Related to Space Cooling or

Heating

Apart from PV rooftop together with battery systems

and electric vehicles, the increased use of cooling

systems in southern countries and electrical heating

systems (e.g. heat pumps) in northern countries will

define the future power demand. The International

Energy Agency [IEA] (2018, p. 36) expects the

cooling degree days, a measure of potential space

cooling demand, to increase worldwide by roughly

25% from 2016 to 2050. Furthermore, (IEA, 2018, p.

37) describes cooling mainly as challenge in urban

areas, partially because temperatures are generally

higher in urban areas than in the surrounding

countryside (so-called heat island effect), and cooling

demand often coincides with the peak load of urban

grids. In (IEA, 2018, p. 33) as well as Ershad,

Pietzcker, Ueckerdt and Luderer (2020) and in Sultan

and Glusenkamp (2021); cooling systems as well as

heat pumps together with thermal storage are seen

also as technologies that can effectively be used in

demand side management concepts thus potentially

mitigating load peaks in urban distribution grids.

1.3 Challenges for the Distribution

Grid

As in Paatero and Lund (2007) and in Lavalliere,

Abdelsalam and Makram (2015), in some cases PV

can help with load shaving. However, peak loads of

residential customers usually do not happen at peak

hours of PV output. With the Vietnamese government

not renewing the support mechanisms for grid-tied

PV, the development of grid-tied solar power has

been stalled. The use of a battery system provides a

key solution in this regard by storing the excess

energy generated by the PV system during the day for

use at night and continuing the use of installed rooftop

PV which cannot be fed into the grid due to the rules.

In contrast to the booming growth of rooftop PV,

facade PV integrated into buildings is still limited in

Vietnam. Until now, there is no literature focusing on

the generation profile and energy yield from facade

integrated PV systems in the urban areas of Vietnam.

The participation of PV systems in the distribution

grids can affect the voltage profile along the power

line. Additionally, according to Walling, Saint,

Dugan, Burke and Kojovic (2008) and Matkar,

Dheer, Vijay, Doolla (2017), since integration of PV

systems can contribute to the change in the voltage

profile, they can affect the operation of voltage

regulators such as voltage regulator (VR), static

compensator (SC) and on-load tap changer (OLTC).

At high PV penetration, the voltage at the point of

common coupling (PCC) can increase, resulting in

the OLTC control to reduce voltage across the line. If

a group of PV systems is disconnected or suffers a

sudden reduction in the power output, a voltage drop

may occur, which would trigger the protective relays.

In summary, Vietnam is pursuing the sustainable

development policy by adopting PV systems in urban

areas. The study mentioned in this paper therefore

addresses and aims to solve the above-mentioned

challenges by: a) investigating the benefits of facade

integrated PV in addition to rooftop solar in Vietnam

for a commercial building, followed by implementing

an energy management system and evaluating the

self-consumption behaviour of this building and b)

controlling the negative effects of increasing PV

penetration on the distribution grid voltage profile

through reactive power control.

The rest of the paper is organized as follows:

Section 2 describes the state of the art and on-going

SMARTGREENS 2022 - 11th International Conference on Smart Cities and Green ICT Systems

118

related research on facade PV integration towards the

context of Vietnam. Objectives and first results of the

study are presented in Section 3. Our conclusions and

further research steps in this study are summarized in

Section 4.

2 STATE OF THE ART AND

ONGOING RESEARCH

2.1 Facade Integrated PV

This section shows some works in the area of PV-

building integrated systems.

As indicated in Bot, Aelenei, Gomes and Santos

Silva (2021), a Building Integrated Photovoltaic

Thermal (BIPV) system developed for electrical

generation and for heating recovery purposes as well

showed that the needs for separate cooling and

heating are reduced compared to the configuration

without a BIPV thermal system. Another interesting

investigation is managed by Brito, Freitas,

Guimarães, Catita and Redweik (2017). Outcomes in

this study revealed that, even though, the facade

systems received less solar radiation in comparison to

rooftop type systems they have the potential to

increase the power generation for the load and are

able to spread the peak PV production throughout the

day, especially for the early and late hours.

PV-HoWoSan (Niedermeyer and Funtan (2019)),

is a project whose objective is the evaluation of PV

facade and rooftop systems in multi-storey residential

buildings. The goal of the project is to develop a

standardized procedure for design of PV facade

systems, which works in terms of building physics

and is safe in several respects.

In the project, a Python software tool was

developed for calculating the PV generation from

rooftop and facade systems and calculating the degree

of self-consumption of a residential multi-storey

building. For calculating the PV generation

consideration to the building characteristics (number

of floors, apartments, facade orientation) and the

irradiation data for the specific city the building is

located in is given (Axaopoulos, 2011). The tool can

therefore be used for PV related studies for a building

in any city for which the irradiation data is available.

The exemplary building configuration (results in

Figure 1 and Figure 2) in the city of Frankfurt consists

of 25 floors and 7 apartments per floor. The building

has an installed rooftop power of 75 kWp and facade

integrated PV systems ( maximum 31 kWp per floor).

The PV facade system is analyzed for four different

shares of facade covering: 7% density (installed

power of 2.2 kWp), 25% density (7.8 kWp), 50%

density (15.5 kWp) and 75% density (23.3 kWp) per

floor. The PV facade is implemented on the south,

west and east side of the building. Additionally, a

second implementation of the same configuration

with a 20 kWh battery storage system was considered.

For the city of Frankfurt, for the exemplary

building, the Python tool can also calculate the total

load per apartment according to the Verein Deutscher

Ingenieure [VDI] 4655 (2019) in Germany. The VDI

4655 provides a guideline on calculating the typical

load for a building in Germany based on the season,

weather conditions and day of the week data.

Figure 1: Percentage of self-consumption for the system

when there is no storage system depending on the facade

share covered with PV modules (Density).

Figure 2: Percentage of self-consumption with a 20 kWh

battery system for the entire building depending on the

facade share covered with PV modules (Density).

Figure 1 and Figure 2 present that the self-con-

sumption has a saturation tendency because there is

more surplus generated with increasing PV covered

facade. Comparing these two figures shows that the

Smart Energy Buildings: PV Integration and Grid Sensitivity for the Case of Vietnam

119

Table 1: Retail electricity price for households and commercial customers (MOIT, 2019(2)) and new proposed FIT price.

Customers Classification

Electricity Price

(exclusive of 10% VAT)

Rooftop PV

system

capacity

FIT price

VND/kWh € ct/kWh VND/kWh € ct/kWh

Households

Level 1: 0-50

kWh/month

1,678 6.40

Less than 20

kWp (most

PV systems

households

have the

capacity of

less than 20

kWp)

1,582.16 6.03

Level 2: 51-100

kWh/month

1,734 6.61

Level 3: 101-

200 kWh/month

2,014 7.68

Level 4: 201-

300 kWh/month

2,536 9.67

Level 5: 301-

400 kWh/month

2,834 10.81

Level 6: 401

kWh/month or

2,927 11.16

Commercial

customers (from

6 kV to 22 kV)

Peak hours 4,400 16.78

20-100 kWp 1468.82 5.60

ormal hours 2,629 10.02

Off-

eak hours 1,547 5.90

Commercial

customers (< 6

kV)

Peak hours 4,587 17.49

From 100

kWp to 1250

kWp

1362.41 5.19

ormal hours 2,666 10.16

Off-

eak hours 1,622 6.18

Note: EURO/VND exchange rate on Nov. 25, 2021 = 26,227.96 (State Bank of Vietnam)

presence of one battery for the building already

increases the self-consumption to approximately 90%

up to the 15-floor. For the first floor (marked in both

graphs), the self-consumption increases to 25% in

comparison with the case without battery.

2.2 Status of Electricity Pricing in the

Country of Vietnam

In Vietnam, the electricity price is different among

residential, commercial and industrial customers

Regarding electricity price for households, there are

six level of prices applying to different amount of

electricity consumption. The retail electricity price

for commercial customers depends on voltage level

and time of consumption with peak hours (9:30-

11:30am and 5:00-8:00pm, not including Sunday),

off-peak hours (10:00pm-4:00am) and other periods

for normal hours (Table 1).

Regarding rooftop PV feed-in tariff in Vietnam,

the price of 2,086 VND/kWh (7.95 € ct /kWh) (FIT1)

has been expired since 2019-06-30 (Prime Minister

[PM] (2019)) and Ministry of Industry and Trade

[MOIT] (2019)). After that, a new policy (FIT2) was

issued on 2020-04-06 (PM, 2020). The FIT price for

rooftop solar systems was reduced to 1,943 VND/

kWh (7.41 € ct/kWh). However, the FIT2 price has

officially expired on 2020-12-31 and currently a new

draft FIT price has been submitted to the Prime

Minister. The draft still proposes a fixed price, but it

is expected to decrease by 18-27% depending on the

project capacity and project type (Table 1).

While the average price of retail electricity in

Vietnam has recently increased, the FIT price tends to

reduce and is lower than the lowest retail price. This

builds a barrier for using the FIT mechanism.

However, it could encourage households having PV

systems to increase self-consumption.

2.3 Hybrid Storage Systems:

Stationary and Mobile Batteries,

Thermal Storage (Cooling)

In Huang, Hsu, Wang, Tang, Wang, Dong, Lee, Yeh,

Dong, Wu, Sia, Li and Lee (2019), deployment of PV

systems increased the necessity of creating new

storage technologies for either self-consumption or

control strategies. A PV system for self-consumption,

comprising the PV modules, inverter and loads, a

stationary battery and a thermal storage is proposed.

In case of PV surplus, first, the battery is charged and

then the thermal hot water storage system. This

hybrid storage system is found to be more

SMARTGREENS 2022 - 11th International Conference on Smart Cities and Green ICT Systems

120

economically viable compared to exporting

electricity to the grid.



In Niedermeyer, Dreher, Degner and Heckmann

(2020)pooled electrical vehicles are used as frequen-

cy control reserves, and the relation between power

variation and voltage change in LV grids are ana-

lyzed. From a pool of electric vehicle (EV), control

reserves are provided in accordance with the

regulations of the Frequency Restoration Reserves

(FRR) without violation of the voltage bands in the

LV feeder.



2.4 Voltage Management

Several papers demonstrate strategies for controlling

the voltage in the power system. As mentioned by Li,

Disfani, Pecenak, Mohajeryami and Kleissl (2018),

traditionally, the OLTCs and voltage regulators are

employed to address voltage issues in the distribution

system. OLTCs always consider a voltage drop along

feeder lines and rule-based control techniques have

proven to lack scalability and cannot be applied to

feeders with multiple OLTCs. Mainly due to the

increase in PV penetration in the medium or low

voltage grid, there is a rise in voltage at the PCC.

According to Phochai, Ongsakul and Mitra (2014)

strategies such as limitation of active power feed-in

and fixed power factor method are first suggested

where remote control utility is not possible. Dynamic

control techniques are preferred because they do not

curtail the active power from PV generation unless

voltage control needs to be implemented.

In Geibel, Degner, Seibel, Bülo, Tschendel,

Pfalzgraf, Boldt, Müller, Sutter and Hug (2013)

voltage control strategies in low voltage grids with

high PV penetration are explored. New voltage

control strategies were developed and applied in

active, intelligent LV networks utilizing reactive

power control capabilities of PV inverters and OLTC

functionalities of secondary substations. The grid

voltages are dynamically regulated to ensure that the

voltage limits are adhered to. The developed compo-

nents were field tested in a German LV grid near

Kassel. As part of the implementation, the smart

secondary substation with an OLTC transformer

(630kVA, 20/0,4kV, ± 3x 2%) controlled the reactive

power provision of three independent PV systems

(Geibel et al., 2013).

3 FIRST RESULTS FROM THE

PV VIETNAM PROJECT

Driven by political incentives, such as the

Vietnamese government’s commitment to energy

availability there is already an increased operation of

grid connected PV systems in the distribution grid in

Vietnam as presented by Do, Burke, Nguyen,

Overland, Suryadi, Swandaru and Yurnaidi (2021).

The study presented in this paper contributes a system

study considering rooftop and facade integrated PV to

observe the potential for self-consumption for a

commercial building in Hanoi, Vietnam. The usage of

mobile (electric vehicles) and stationary batteries and

thermal storage (cooling) to avoid peak load

situations is implemented. The consideration of peak/

off-peak tariffs can provide insights into the econo-

mic viability of such systems and the potential of

grid-interactive buildings for load and voltage

management in distribution grids.

A first step in this work is the calculation of the

PV-energy yields for an identical building at the city

of Hanoi and Frankfurt for rooftop and south, east and

west oriented facade PV systems. A building area of

625 m

with 10 floors was chosen and the Python tool

developed in the PV HoWoSan project (Niedermeyer

and Funtan (2019)) was adapted for both cities. For

the city of Hanoi an optimal tilt angle of 10° and for

Frankfurt an optimal tilt angle of 30° were considered

for the rooftop PV systems. Table 2 presents the

energy yields of the rooftop and facade PV systems

(in kWh/kWp) and the percentage generation of the

facades as a share of the rooftop generation for each

of the two respective cities:

Table 2: Energy yields in the city of Hanoi and Frankfurt

for rooftop and south, east and west facade and ratio of

energy yield of facades with respect to the rooftop PV

system.

Hanoi Frankfurt

Roof-

top

1317 kWh/kWp,

(x)

949 kWh/kWp,

(y)

South

722 kWh/kWp,

55%x

640 kWh/kWp,

67%y

East

685 kWh/kWp,

52%x

517 kWh/kWp,

55%y

West

811 kWh/kWp,

62%x

541 kWh/kWp,

57%y

Smart Energy Buildings: PV Integration and Grid Sensitivity for the Case of Vietnam

121

The same building for the cities of Hanoi and

Frankfurt is considered and shadowing effects are

ignored. The energy yield contributions are higher for

the city of Hanoi. However, the percentage of energy

yield for the facades with respect to the rooftop

generation is higher for the city of Frankfurt. This is

due to the differences between the optimal tilt angles

of the rooftop in the respective city and the vertical

facade systems.

This next step in the study includes the assessment

of the PV generation profile in Hanoi (World Bank

Group (2018)) and the typical load profile of a

commercial building (10 floors and 625 m

rooftop

area) and the simulation of a simple EMS involving

stationary batteries, EV and thermal storage (cooling

systems). The load data is obtained from Electrical

Power University [EPU] (2016). The EMS functions

based on a peak-shaving process.

The EMS comprises the peak shaving

functionality. For reducing total costs, the charging

and discharging of the storage systems will be done

according to the peak/off-peak time. As an example,

Figure 3 and Figure 4 indicate flowchart diagrams of

the cold water storage/ cooling system charge and

discharge procedures.

Figure 3: Flowchart diagram for the cooling system

operation in the off-peak time.

Figure 3 indicates the flowchart diagram of the

cooling system at the off-peak time. The objective of

this approach is to charge the water storage to the

maximum capacity to prepare for the peak-times and

therefore to unload the grid. In this example, the

charging power is chosen as 25% of the discharge

power (d_power). This discharge power corresponds

to the supply power that the cooling system needs for

operating. In off-peak time, the grid can supply power

to the cooling system and is able as well to charge the

water storage. At the peak-times, as in Figure 4, the

goal is to discharge the water storage first to provide

the power supply to the cooling system thereby

avoiding the import of power from the grid. Thus, the

EMS can help to mitigate peak load in the grid, if

necessary.

Figure 4: Flowchart diagram for the cooling system

operation in the peak time.

4 CONCLUSIONS AND FURTHER

WORK

This study is in the field of integration of distributed

PV generation in urban areas in Vietnam. Because of

the ambitious political objectives of the Vietnamese

government, this topic is very important for the

sustainable development strategy of Vietnam.

This study presented in this paper is a first

investigation into the potential use of PV facade

systems for energy yield in Vietnam. A case for

increased PV facade implementation and self-

consumption is made through the calculation of the

irradiation data, modelling of generating units and

initial implementation of energy management.

Investigations on self-consumption are motivated by

the proposed decreasing FIT prices while retail

electricity prices are increasing.

SMARTGREENS 2022 - 11th International Conference on Smart Cities and Green ICT Systems

122

This project has considered irradiation data for

Hanoi and calculated the PV generation for rooftop

and facade installations for an exemplary commercial

building. An energy management concept is

developed after modelling of the generating units

such as a stationary battery, EV battery and the

cooling system as thermal storage. Actual load values

are considered for the calculations of the EMS.

Further steps in the project are: a) further

development of the EMS for the assessment of the

self- consumption behaviour, b) analysis of the

resulting electricity costs after implementing such an

EMS using time-of-use pricing mechanism and c)

development of voltage control strategies for the

Vietnamese distribution grid with high PV

penetration through modelling of the grid and

implementation of control.

ACKNOWLEDGEMENT

We acknowledge the support by the project “Reactive

Power Control 2” (FKZ 0350003A) funded by the

German Ministry of Economic Affairs and Energy

(BMWi) and the project “PV Vietnam” (FKZ

01DP19002) funded by the German Ministry of

Education and Research (BMBF). Only the authors

are responsible for the content of the publication.

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