Smart Grids

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.

[2] U.S. Department of Energy. What is the smart grid? http://www.smartgrid.gov/the_smart_grid. Accessed: 2013-02-12.

[3] U.S. Department of Energy. The Smart Grid: An Introduction. http://energy.gov/sites/prod/files/oeprod/DocumentsandMedia/DOE_SG_Book_Single_Pages%281%29.pdf, 2008. Accessed: 2013-02-12.

[4] European Commission. Smart grids: from innovation to deployment, April 2011.

[5] Bio Intelligence Service. Impacts of information and communication technologies on energy efficiency, final  report. ftp://ftp.cordis.europa.eu/pub/fp7/ict/docs/sustainable-growth/ict4ee-final-report_en.pdf, September 2008. Accessed: 2013-02-12.

[6] Consolidated Edison, Inc. Smart Grid Initiative. http://www.coned.com/publicissues/smartgrid.asp. Accessed: 2012-01-06.

[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.