One approach to modernize and improve the efficiency of electrical
grids is marked by the term
Smart Grid, which can be defined as “a set of software and hardware tools
that enable generators
to route power more efficiently” [1]. In more detail, the efficiency
gains can be achieved by
additional functionalities of electrical grids, enabling two-way
communication between power
providers and customers and sensing along transmissions lines. Therefore
a Smart Grid is characterized by a high grade of automation and the use
of digital technology, that enables the grid
to respond to changes in power demand [2].
Traditional
electrical grids grew over decades to it’s current size and can be
constituted as
patchwork, which is the reason for inefficiencies. The electrical grid
of the United States of
America experienced a growth in peak energy demand since 1982 and was
expanded to keep up
with the increasing transmission [3]. At the time the grid was
designed it was not necessary
to consider environmental aspects or energy efficiency. To meet today’s
requirements a modernization of the electrical grids of industrial
nations all over the world is needed. Therefore ICT
technology can be integrated throughout the grid to optimize them. From
an environmental view
an increase of efficiency of electric grids would be big step towards low
carbon emission goals:
Only a 5 percent efficiency gain of the electrical grid of the USA would
equate the greenhouse
gas emissions of 53 million cars. In total the USA produce 25 percent of
global greenhouse gas
emissions, while half of U.S. power production is still based on fossil
fuels [3]. These numbers illustrate the enormous savings potential of
optimizing power generation and transmission
processes.
Beside the U.S. government the European
Union communicates the important role of Smart
Grids for future energy management and fulfillment of Europe’s energy and
climate goals in
compliance with the EU2020 agenda. The Smart Grid will give energy
consumers strong incentives to save energy, because of the distribution
of smart meters and information and communication systems: “It opens up
unprecedented possibilities for consumers to directly control and manage
their individual consumption patterns, providing, in turn, strong
incentives for efficient
energy use if combined with time-dependent electricity prices” [4].
According to the communication of the European Comission there are
projects which show that households which have
been equipped with smart meters reduced their energy consumption by as
much as 10 percent.
The Smart Grid is considered as “the backbone of the future decarbonised
power system” [4],
as it enables the integration of renewable energy sources. A study by
the European Bio Intelligence Service detected a possible reduction in
carbon emissions by 9 percent by the year 2020
due to Smart Grids [5].
Figure 1 illustrates the
features of a Smart Grid. Electricity is increasingly generated from
renewable sources and distributed by the Smart Grid to private and
business customers. All over
the grid intelligent ICT systems are implemented, enabling faster
failure detection and increasing
reliability. There are control centers for management and operation,
which are analyzing information on energy consumption from the grid in
real-time to forecast demand peaks. Customers
are provided with smart meters and Intelligent Building Systems to
monitor and control their
energy consumption. The power generators of customers’ homes are
connected to the Smart
Grid and can deliver power to the community that is not needed locally.
The Smart Grid also
provides plug-in functionality for electric cars to reload their
batteries [6].
Figure 1: Smart Grid [6]
The advantages of a Smart Grid, arising from the use of ICT to enable bidirectional energy
and information exchange, support the development towards a more sustainable energy management [2]:
- Reduced losses in transmission of electricity and therefore a higher level of energy efficiency.
- A higher grade of automation and more efficient technical equipment
will decrease operation, management and maintenance costs, resulting in
lower power costs.
- Quicker electric recovery in case of outages, because of automatic rerouting by the Smart
Grid. Failures will occur less often and can be detected and isolated faster, avoiding large-scale blackouts.
• Reduced power outages imply improved security.
- Integration of large-scale renewable energy power plants.
- Smart Grids also enable the integration of distributed small-scale sources of renewable
energy, like customer-owned power generators (e.g. photovoltaics).
- Increased consumer participation and control, due to real-time
information on power consumption and cost control functionality (smart
meters).
Figure 2: Grid connected solar home system [7]
In contrast to traditional centralized energy generation by large-scale power plants, using
fossil or nuclear sources, the trend in renewable energy production is towards decentralized
small-scale energy generators. This brings new requirements for electricity grids, in order to
integrate various types of generators with partly wider spatial distribution. Energy generators
using sun or wind power can be installed as part of buildings, to cover part of the local energy
demand and to supply energy to the grid at times when some part of the produced energy is not
needed locally. Figure 2 shows a schema of a home photovoltaic (PV) system that is connected
to the electrical grid. The solar PV system generates electricity that is used to power building
appliances and also can be stored in backup batteries to partly balance supply shortcomings due
to the dependence of PV systems on weather conditions. If needed additional power can be
purchased from the grid, while it is also possible to feed electricity back to the grid.
The
approach of small-scale distributed power generation allows parts of
the electricity network to operate in separation from the main grid,
assuming that enough power is generated
to cover the local energy demand. Such areas are called Micro Grids,
which are based on the principle that energy customers can supply their
own demand by distributed small-scale power
generators, as well as serve exceeding power to their local neighbors
[8]. Micro Grids enable the development of more sustainable energy
generation and management, and could create
stronger incentives for the distribution of small-scale power generators
to gain a certain level of
independence from the main electricity grid and decrease energy costs.
The financial effort of
investing in micro generation systems is much lower in comparison to
large scale power plants,
which could be an important aspect for public participation. Another big
environmental advantage of Micro Grids is the reduction of energy
losses and thereby greenhouse gas emissions.
Today’s centralized power generation and distribution suffer from losses
of 7 to 10 percent of
total energy generation due to long distances of transmission [8].
Concepts based on the idea of buildings as small-scale power plants require Smart Grids
to integrate them into large-scale electricity grids [2]. Therefore applications are needed to
coordinate different energy sources and adjust energy demand and supply to gain maximum
efficiency from generators. Such systems for modeling, analysis and control of multiple energy
sources are a current research topic [9]. The main feature of a control system for multiple
energy sources is the adjustment of energy production, energy consumption and energy storage
(cf. figure 3). By designing a system for this purpose following features and circumstances
have to be considered: [9]
- Energy production by wind and solar generators is stochastic since
intensity of wind and
sunlight varies in relation to the weather situation. Therefore the
system needs an applicable model to assume and predict the produced
amount of energy.
- To optimize the alignment of energy demand and supply, also an assumption of energy
demand is needed.
- In consideration of these requirements the system has to achieve a optimum balance of
energy production, consumption and storage.
Figure 3: Control system for multiple energy sources [9]
References
[1] The Climate Group. Smart 2020: Enabling the low carbon economy in the information age. Technical report, The Climate Group on behalf of the Global e-Sustainability Initiative (GeSI), 2008.
[4] European Commission. Smart grids: from innovation to deployment, April 2011.
[7] B. Metz. Controlling climate change. Cambridge University Press, 2010.
[8] R. M. Kamel. Carbon emissions reduction and power losses saving besides voltage profiles improvement using micro grids. Low Carbon Economy, 01(01):1–7, 2010.
[9] A. Naamane and N. K. M’Sirdi. Macsyme: Modelling, analysis and control for systems with multiple energy sources. In Robert J. Howlett, Lakhmi C. Jain, and Shaun H. Lee, editors, Sustainability in Energy and Buildings, pages 229–238. Springer Berlin Heidelberg, 2009.
