This document discusses four possible scenarios for incorporating household solar PV systems into the power grid. Case 1 involves a utility grid connected to loads and private battery storage, with no power fed back to the grid. Case 2 has no battery storage, so any excess power is fed back to the grid. Case 3 uses communal battery storage at the grid level. Excess power is fed back to the grid. Case 4 adds a DC network connecting communal storage to homes, so excess power is stored rather than fed back via AC. Each case is evaluated based on technology, complexity, efficiency and flexibility. An effective system can be chosen based on requirements.

1. Incorporating Solar Home Systems for Smart Grid
Applications
B. Alipuria (*), B. Asare-Bediako (*), R.J.W. de Groot (*), J.Sarker (*), J.G. Slootweg (*), W.L. Kling (*)
(*) Eindhoven University of Technology, Den Dolech 2, Eindhoven, The Netherlands
B.Alipuria@student.tue.nl; B.Asare.Bediako@tue.nl; R.J.W.d.Groot@tue.nl; J.Sarker@student.tue.nl; J.G.Slootweg@tue.nl;
W.L.Kling@tue.nl
Abstract- Smart Grids have been one of the prime focuses of
studies for the past few years on power systems. The goal is to
make the power infrastructure more reliable and effective to
cater for the needs of the future. Another goal for improving the
power infrastructure is to incorporate renewable energy sources
in an efficient and cost-effective manner. The popularity of solar
PV has increased in recent times which has lead to exponential
growth in the installed solar PV. This paper compares four
possible scenarios for incorporating household solar PV systems
into the power grid. It discusses the properties of each scenario
along with their advantages and disadvantages. An effective
system layout can be obtained by choosing the suitable case for
incorporation of solar home systems according to the
requirements.
Index Terms-- DC Micro-grids, Distributed generation,
Energy management system, Smart Grids, Solar home system
I.
INTRODUCTION
The last few years have seen considerable increase in
energy demand in the world [1]. This is due to the increasing
population and the rising standards of living. A concern in
this regard is that the conventional resources for power
generation are limited and are depleting rapidly. Additionally
there is a great requirement to find alternative ways to
generate power due to climate change problems and
increasing anthropological CO2 levels. This has led to a major
development in renewable energy sources (RES) [2]. Despite
many efforts, RES are still struggling to replace conventional
generation sources. One of the prime reasons is the
uncertainty and “uncontrollability” of these sources. One of
the solutions to incorporate renewable energy sources as a
major part of power system is to have multiple buffers to
compensate for their uncertainty [3].
Smart Grids is a much discussed concept for future power
systems. It incorporates the functioning of components of the
grid in an intelligent and flexible manner for optimal
operation of the grids [4]. The various components i.e.
generation sources and loads are monitored and a local or
central control co-ordinates the power flow according to set
rules, priorities and preferences. Information is collected,
processed and managed for monitoring and controlling of
various components. Such ideas are also incorporated in this
paper.
Keeping in mind the need for renewable energy and the
need for power grids to be smart, in this paper an attempt has
been made to design a system that could meet the
requirements of the future. This has been primarily done by
integrating the solar home systems into the power grid with
effective controls and information transfer. Advanced
technologies have been acknowledged that could enhance the
performance of such a system to accomplish effective and
competent electric power scheme.
II.
SOLAR HOME SYSTEM
The most preferred renewable source of energy by the
consumers, particularly in sunny parts of the world, is the
solar photovoltaic system [5]. Due to its easy installation and
almost no maintenance, it is very easy to incorporate within
the home system. It provides local generation source for
every household which can be used in various ways and also
avoids transmission losses. The home system can also consist
of batteries that store energy for future/emergency use along
with the controllers and converters required in accordance to
the type of use. Energy storage acts as a buffer to increase
system’s reliability and improve control for the network. The
conventional system layout for a Solar Home System (SHS)
is shown in Fig. 1.
The sizing of various components is done according the
requirement of the user and its installed function [6-7]. Users
can manage their energy by choosing between power from
grid or PV panels as the primary source and the other as
backup. The user can control the load operation to match the
time of generation so include the ideas of demand side
management [8]. This reduces the stress on the grid and
makes it stable. In the case of excess energy during day time,
it can either be stored in batteries to be used later or supplied
back to the grid. The batteries are often expensive hence large
power storage is difficult. Supplying back to the grid has
some challenges like low feed-in tariffs, and power quality
standards [9]. With generation at distribution level, often the
conventional power infrastructure is challenged. On the other
Fig. 1. Layout for conventional solar home system

2. hand, it enables ‘bottom-up principl
les’ by use of
decentralized generation sources in the power system. It
makes the system more robust and reliable. The SHS needs to
.
be incorporated within the future grids in
nfrastructure. There
are certain conditions that it must satisfy along with giving
sufficient comfort to the user.
III.
SMART GRIDS
disturbance in the main netwo
ork. Then affected component
will be isolated automatically a the rest of the system shall
and
function in limited capacity. Th would reduce the affected
his
area and make the network more robust.
In this paper, we will ma
ainly consider on designing a
micro-grid with SHS acting as distributed generation.
g
Multiple micro-grids can be c
combined to cater to a larger
network bringing in stability a modularity to the system
and
[14].
er
It is important to redesign the powe infrastructure to
integrate the various new and developing technologies within
IV.
HOME ENERGY MANAGEMENT SYSTEM
the system. These include the technologies on generation,
storage and efficient use of power. Also th incorporation of
he
Controlling an interface of loads and grids would require
communication technology within the pow system would an effective energy managemen system that would empower
wer
nt
lead to a more efficient, versatile a
and user friendly the user to control its power f
flows. This unit is called the
infrastructure. Hence the concept of Sm Grids is being Home Energy Management Sys
mart
stem (HEMS). It does not only
researched to integrate such various advan
ncing technologies monitor and control the power f
flows but also enables the user
in the infrastructure [4]. A variety of ways have been used to to customize his power accordi to his needs. The user can
ing
define such a system, but for this paper we have used the select what source of power he/
/she prefers. It can control the
comprehensive definition of Smart grid by Smart Grid load devices using the HEMS t
ds
thus enabling him to prioritize
dictionary [10].
the demand according to cond
dition [15]. This can be done
The Smart Grid is a bi-directio
onal electric and using the principles of demand s management of power.
side
communication network that improves the reliability,
s
The HEMS can function in various modes according to
n
security, and efficiency of the electric sy
ystem for small to the needs of the user and the best suitable environmental
e
large-scale generation, transmission, distribution, and condition. Various scenarios can be programmed in the
re
er
storage. It includes software and hardwar applications for system to control such a powe system. It also acts as the
dynamic, integrated, and interoperable optimization of intelligent centre for the house that operates on the basis of
e
e
electric system operations, maintenance, and planning; information signals it receive from the grids and loads
es
distributed generation interconnection and integration; and respectively. It optimizes the power usage of the home
according to the instructions of the user. HEMS plays a major
feedback and controls at the consumer leve
el.
One of the most important distinction in a smart grids role in empowering the user. G
ns
General architecture for Home
infrastructure is the inclusion of Informatio Communication energy management is shown in fig. 2.
on
n
Technology (ICT) at various positions of th systems. It plays
he
V.
INTELL
LIGENT LOADS
an important role to monitor system at v
various points and
With the advancing techno
ology, loads are developed to
evaluate the state of various parts of the system. It should
d
communicate this information to other par so the effective integrate into the evolving grid network. This would include
rts
action can be taken by the other parts of the system if intelligent control that would enable them to work more
effectively and synchronies themselves in accordance
required.
se
Such ICT based network ensures re
eliability in power network conditions [16]. Thes devices can be controlled
supply and better power exchange within the grid. Also it from the HEMS or individual controls within the device.
n
would be able to incorporate all kinds o generation, both Such devices would be capable of automated operation under
of
y
small and large within the system in an effi
icient manner. This required conditions. They may even have the capability to
can
would greatly improve the ability of inte
egrating distributed store energy. Electric vehicles c be considered as one such
e
generation and local RES. Such an advan
nced system would load that can store energy hence acting as a buffer if required
need to include additional software and har
rdware for efficient [17].
working [11]. In total, the system would ea the pressure on
ase
environment by promoting renewable gen
neration sources at
various points on the grid. The network would be easy to
xtent autonomous.
monitor and operate and to a great ex
Another important feature would be to em
mpower the user to
participate in the power grid in an effect
tive with a deeper
understanding of the system [12].
In a Smart Grid are multiple se
ensors and relays
monitoring and operating the network Communication
k.
technologies shall be used to exchange required information
within system for efficient operation [13]. It includes storage
as energy buffers and smart load like elect vehicles. There
tric
is also a possibility of networks connected in such a manner
d
that it is possible to operate in island m
mode if there is a Fig. 2. Home energy management system architecture
m

3. VI.
SYSTEM DESIGN
To design the system for SHS integration, multiple cases
were formed and evaluated. The formation of the cases is
based on possible combination of various components that
could be used in a SHS. These cases are compared with each
other primarily based on the following parameters:
1.
3.
Technology
Efficiency
2.
4.
Complexity
Flexibility
A HEMS has been considered as a control unit in every
home and an interface to the network.
Case1: Utility grid connected to the load along with the
HEMS. Storage is personal and no energy is fed back to the
grid.
The case is formulated simply by combining the SHS
with utility grid infrastructure along with ICT enabled
controls monitored by HEMS as shown in Fig. 3. Due to
private storage availability, the house can work on island
operation if the grid fails. There are no changes in the
operation of the network and the smart features are
extensively applied within the home.
• Technology: The technology for the system is well
developed and is already in application.
• Complexity: There is some degree of complexity involved
in the operation. Various sources like PV power input,
battery SOC, load power and grid quality can be variables
for operation.
• Efficiency: The system is not very efficient due to the
need for a very large battery in order to store all the
excess energy for the household. There is limited need for
conversion of power between AC/DC.
• Flexibility: Limited flexibility for the user due to limited
storage and singular power source. No additional
flexibility is gained for the network.
Case2: There is no storage in the system. Any excess power
generated is fed back to the grid.
This case is formed by removing the storage from the
SHS to analyze its effects as shown in Fig. 4. Due to lack of
Fig. 4 System layout for case 2 - There is no storage in the system. Any
excess power generated is fed back to the grid
storage and unpredictable RES it becomes difficult to operate
the network with high efficiency. It can be overcome by the
prediction of RES and load as accurately as possible.
• Technology: The technology for the system is developed
to a great extent. The power quality at grid level is
affected adversely due to inverters but can be improved.
• Complexity: The system is really simple to manage as
there are not a lot of components reducing the number of
variables for operation. The complexity for operation is
prediction of load and generation accurately which can be
overcome by having a variable load or buffer system.
• Efficiency: It is difficult to predict the load and generation
precisely and with lack of storage. Any mismatch in
energy is influences power quality of the utility grid.
• Flexibility: There is no flexibility for the user or network
operator. The generation must meet the demand at all
times which is often difficult to predict.
Case3: Utility grid is connected to community storage and
the HEMS. Excess energy generated by PV is fed back to the
grid.
This case is formed by using communal storage at grid
level thus reducing the need for private storage as shown in
Fig. 5. The use of communal batteries is more effective
compared to individual batteries [18]. It provides a larger
storage to every household hence ensuring optimized usage.
These can be collectively maintained and the operation can be
monitored by the network operator, providing more
flexibility. Also, the storage can be used as a fast charging
station for electric vehicles or other purposes that requires
high power for short term.
The grid becomes more robust and certain parts can
operate in islanded mode if there is a fault. The storage helps
the network to integrate RES within the system with a higher
efficiency in comparison to a network with no storage [18].
Fig. 3. System layout for case 1 - Utility grid connected to the load along
with the HEMS. Storage is personal and no energy is fed back to the grid.
• Technology: There is a developed technology available
for this scenario as well. The power quality of the utility
grid is affected by the numerous feed-in inverters during
excess generation.
• Efficiency: System efficiency is reduced due to multiple
conversions of power between AC and DC at various

4. Fig. 5. System layout for case 3 - Utility grid is connected to community
storage and the HEMS. Excess energy generated by PV is fed back to the
grid.
levels of the grid. Many economically viable converters
are used that also affect the power quality.
• Complexity: The system is relatively easy to operate at
user as well as network level. There are not many
variables that need to be taken into account thus making
the system simple.
• Flexibility: The user has limited flexibility. Network
operator gains the needed flexibility for an efficient
operation due to the presence of storage.
Case4: Excess power is not fed back to the grid but stored in
a communal storage which is connected to the HEMS using a
DC network.
The case is formulated by adding an additional DC grid
that connects the HEMS to the communal storage as shown in
Fig. 6. This configuration allows the additional DC
technology to be integrated within the grid. It provides a lot
of advantages that DC has to offer along with making the
system more reliable by providing dual voltage network.
These have been discussed further in the paper.
• Technology: The technology involved in the system
would be new and needs to be perfected with time. The
technologies that are in play for the network already exist
but have to be improved upon according to the needs.
• Flexibility: Due to multiple power sources, the system has
a high degree of flexibility. Both AC and DC power are
available for the user to choose from. There is a storage
system for excess generation. There is a lot of freedom for
both the network operator as well as user within the
system.
• Efficiency: The presence of both AC and DC encourages
reduced power conversions. This improves the efficiency
of the system. Power quality for the grid is enhanced.
Incorporating storage allows efficient integration with
RES.
• Complexity: The operation of the system can be really
complex due to the large number of variables in the
system. This is a trade-off between flexibility of the
system. This can be overcome using effective ICT control
strategies by both user and network operator.
With the advancement in power electronics, it might be
important to consider DC systems as a part of the network.
There has been great progress in electronics technology.
Various modern day devices work on DC. With only AC
networks, there is a need to convert the power to DC for such
devices that reduces system efficiency. A DC-powered local
grid can reduce the conversion losses [19-20]. Apart from the
load devices, there are also DC generation sources like PV
panels which are really simple to implement. The formulation
of a DC power network would reduce the need for many
AC/DC conversions improving the efficiency of the system.
The absence of frequency function makes a DC network
simpler to control, monitor and operate. Power transmission
with DC is also more effective than AC transmission [21].
Another major advantage that incorporation of DC lines
could provide for the network would be their ability to carry
information signals along with DC power [22]. Since DC
current is a constant voltage line, information signals can be
easily superimposed on the line. Telecom technology like
Asymmetric digital subscriber line (ADSL) technology can
be used for transmission of data in the network over short
distances on these DC lines. This reduces the need for
separate channels for data transfer making the communication
more secure [23].
DC networks are already applied in various niche areas.
Many ships and submarines are powered by DC networks
[24]. People have started employing total DC technology to
power off-grid house [24-25]. Many commercial data centres
have also been suggested to switch to DC power mode which
can be up to 20% more efficient than using AC power [20].
Even though the use of DC has many advantages, there
are still many barriers it must overcome. The most important
one would be standardization of DC. There are no standards
of DC voltages, so manufacturers can’t products to connect to
a DC grid network directly. Another concern is the safety and
regulatory aspect of DC networks. Since it is a new
technology, large scale implementation must be regulated to
safeguard society. Once standardization is done, the
technology on networks can advance much faster.
Fig. 6. System layout for case 4 - Excess power is not fed back to the grid
but stored in a communal storage which is connected to the HEMS using a
DC network

5. Fig. 7. Proposed system layout – Integrating solar home systems to smart grid infrastructure (Exten
nsion of Case 4)
A micro-grid can be formed by c
connecting various
HEMS systems to the communal storage to
ogether as shown in
Fig. 7. This could even enable large renew
wable sources like
wind farms and solar farms to be conne
ected to the grids
without any problem. The ICT infrast
tructure could be
embedded within the network omitting t need for extra
the
communication network. The system would be reliable, more
flexible and futuristic.
VII.
REFERE
ENCES
[1]
[2]
[3]
CONCLUSION
The Solar Home Energy Managemen System can be
nt
easily incorporated in the new Smart Grid design giving the
d
user multiple options to choose from. The system keeps the
e
user informed about the state of the netw
work so he/she can
make intelligent decisions regarding opera
ation. It is possible
to include DC technology and a communal battery within the
l
design which makes the system more flex
xible and robust in
use. ICT incorporation within the system m
makes it smart and
futuristic. Standardization of DC is requir for mass scale
red
integration in the system. With advancing technologies, the
g
system can be used to its best capacity m
making the power
infrastructure much more reliable and versatile. Comparison
of various cases for integration of SHS wit
thin the system has
been given in Table I.
[4]
[5]
[6]
[7]
[8]
[9]
IEA, “World Energy Outlo
ook”, 2010 – Available Online:
(http://www.iea.org/publication
ns/freepublications/publication/name,
18027,en.html), April 2012
M. Wolsink, ”The research agenda on social acceptance of
rt
distributed generation in smar grids: Renewable as common pool
resources”, Renewable and Su
ustainable Energy Reviews, vol. 16.1,
pp 822-835, January 2012
J. Liantao, Z. Jiancheng, “An e
effective hybrid energy storage system
based on battery-EDLC for d
distributed generation systems”, 5th
IEEE Conference on Indus
strial Electronics and Applications
(ICIEA), pp 819-824, June 2010.
J.G. Slootweg, M.M.A.M. Van der Meijden, J.D. Knigge,
mart grids – Different concepts and
E.Veldman,, “Demystifying sm
connection with smart metering CIRED, June 2011
g”,
Live
Science
Survey
y
–
Available
Online:
(http://www.livescience.com/en
nvironment/090417-top10-alternativeenergy.html), March 2012
ye,
M. Bond, R.J. Fuller, L. Ay “Sizing solar home systems for
optimal development impact” Elsevier-Energy Policy, vol. 42,
”,
pp.699-709, March 2012
M.M.H. Bhuiyan, M.A. Asgar, “Sizing of a stand-alone photovoltaic
vier-Renewable Energy, vol. 28.6, pp.
power system at Dhaka”, Elsev
929-938, May 2003
M. Castillo-Cagigal, et al., “A semi-distributed electric demand-side
management system with PV generation for self-consumption
enhancement”, Elsevier-Energy conversion and management, vol.
52.7, pp. 2659-2666, July 2011
S.K. Kim, J.H. Jeon, C.H. Cho, E.S. Kim, ”Modeling and simulation
neration system for electromagnetic
of a grid connected PV gen
transient analysis”, Elsevier-So Energy, vol. 83.5, pp. 664-678,
olar
TABLE I
COMPARISON OF CASES FOR SHS INTEGRATION
Case
Main Components
Advantages
Disadvantages
1
PV Modules + HEMS +
Grid + Individual storage
•
•
•
Developed technology
Simple operation
High efficiency
• Private battery leads to high cost
y
• Limited flexibility
2
PV modules + HEMS +
Grid
•
•
•
Simple operation
Developed techolgoy
Cost effective operation
• Difficult to operate with RES
• Limited flexibility
• Grid power qu
uality affected
3
PV modules + HEMS
+Grid + Communal storage
•
•
Operational flexibility at grid level
Effective integration with RES
• Efficiency loss due to multiple conversions
ses
• Grid power qu
uality affected
4
PV modules + HEMS
+Grid + Communal storage
+ DC network
•
•
•
Backup DC grid structure
High flexibility
Higher efficieny
• Developing tec
chnology
• Complex opera
ation
• High investme cost for the DC-network
ent

6. [10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
May 2009
C. Hertzog, Smart Grid Dictionary, GreenSpring Marketing LLC,
2009
K. Moslehi, “A reliability perspective of the smart grid”, Smart Grid,
IEEE Transactions, vol. 1.1, pp. 57-64, June 2010
H. Dick, H. Eden, G. Fischer and J. Zietz, “Empowering users to
become designers: Using Meta-design environments to enable and
motivate sustainable energy decisions”, Colorado University, 2012
J. Gao, et al., “A survey of communication/networking in Smart
Grids”, Future generation computer systems, vol. 28.2, February
2012
J. Shah, B.F. Wollenberg and N. Mohan, ”Decentralized power flow
control for smart micro-grid”, IEEE - Power and Energy Society,
General meeting 2011, pp. 1-6, July 2011
B. Becker, et al., “Decentralized energy-management to control
smart-home architectures”, Architecture of computing systems, vol.
5974/2010, pp. 150-161, 2010
K. De Brabandere, et al., “Control of microgrids”, Power
Engineering Society – IEEE, pp. 1-7, June 2007
T. Sousa, et al, “Intelligent energy resource management considering
vehicle-to-grid: a simulated annealing approach”, IEEE - Smart
Grid, vol. 3.1, pp. 535-542, March 2012
I. Koutsopoulos, V. Hatzi and L. Tassiulas, “Optimal energy storage
control policies for smart grids”, IEEE – Smart grid communications
international conference, pp. 475-480, October 2011
Shah, K., Sehnai, K., “Smart DC micro-grid for efficient utilization
of distributed renewable energy”, IEEE - EnergyTech ; Cleveland,
OH, pp. 1-6, May 2011
Lawrence Berkeley National Laboratory, “DC power for improved
Data-Centre Efficiency”, Report, March 2008.