Abstract
Nowadays, residential hybrid energy systems are moving from being a pure theoretical exercise to real applications for new urban areas. The growing interest related to the needs of reducing pollution, the phasing out of fossil fuel resources and the need to safeguard the environment, have led to a large number of studies and solutions to reduce fuel consumption and to manage energy sources in a better way, leading to an innovative concept of the city where smart infrastructures are in place. In this chapter we introduce the concept of hybrid energy systems, namely buildings that can exploit both renewable energy sources and the grid. On top of it, a system manager schedules the usage of electrical appliances to minimize the electricity bill while providing peak shaving and load balancing services to utilities and service providers.
TopIntroduction
A city becomes smart whenever investments in ICT referred to human and social capital ensure sustainable economic progress, a high quality of life and an efficient management of natural resources (Seisdedos, 2012). Indeed, with the term smart city we define a set of urban planning strategies aimed at optimizing and innovating public services in such a way as to connect infrastructures with human/intellectual/social capital. This result can be achieved thanks to new communication technologies, mobility innovations and environmental safeguards/energy efficiency: the common objective is to improve the quality of life, satisfying the needs of citizens, businesses and institutions. A marked line between smart cities and digital cities can be defined, due to the profound difference between a city which leverages on environmental & social capital and a city with a huge technological infrastructure. Urban performances are not only measured with the pure presence of infrastructures, but also with the availability and quality of communication, knowledge and social infrastructures which determine urban competitiveness.
The expression Smart city is frequently used in different contexts. In economics, it describes smart industry, and especially industries related to ICTs in different forms. Moreover, smart city can be used in regard to the education of its inhabitants: a smart city definitely has smart citizens. In other cases it can be referred to associate governments, administrations and their citizens: “e-governance” and “e-democracy” are increasingly popular and widely-used terms these days. Furthermore, smart city is associated with modern transport technologies, i.e. smart systems capable of improving urban traffic and mobility. Finally, aspects related to quality of life are often associated with the word smart, in connection to sustainability, green energy and security in general terms. Above all, the level of innovation and problem-solving capabilities define smart cities: ICT technologies are the most important means of improving these characteristics. In this way, smartness is somehow an internal quality of a place, city or region in which innovation processes are simplified through information and communication technologies. The smartness level is mainly defined according to people, cooperation systems, digital infrastructures and the means provided by the community to citizens.
In this context, a pillar infrastructure of a smart city is the power distribution grid. When power distribution infrastructures exploit ICT for improving overall efficiency and sustainability, we can refer to them as fundamental components in the larger domain, better known as Smart Grids.
Smart cities and smart grids are strictly correlated: the majority of existing smart cities can leverage on smart grid technologies, including mostly energy-oriented objectives. While smart cities can make the user aware of energy efficiency and savings, smart grid components provide infrastructures capable of connecting different elements of the city itself.
A smart grid is based on a concept of bi-directional electricity flow where buildings can also generate and store electric energy, while some years ago they were simply supposed to be consumers. Now, the local generation of electric power could potentially transform households into energy producers and hybrid electrical residential systems could become a source of earnings and not only used for saving money. A smart grid must facilitate the optimal management of the load (offering demand-side management and other ancillary services), exploiting the information processed from the meter, and should avoid energy waste, overload and voltage drops.
Key Terms in this Chapter
Hybrid Energy Storage Systems (HEES): Electronic systems capable of storing electrical energy for non-immediate use. It may consist in a set of batteries of various technologies (lead-acid, lithium-ion and so on) arranged in a matrix to achieve the required storage capacity where the heterogeneity of technologies allows to mitigate the drawbacks and maximize the effectiveness.
Residential Load Scheduling: A control system (algorithm) interfaced with domestic appliances (washing machines, TV-sets and so on), the house and the electricity distribution grid (service provider) able to automatically manage the electronic devices according to several policies, integrating user habits, requirements from the service provider, time of the day and so on. For example in case of network maintenance the system can postpone the dishwasher from morning to afternoon, automatically, while the user is at work, at the same time fulfilling the requirement to get the service complete by 6pm. In the same way it is possible for the user to turn on all his appliances (oven, dishwasher, washing-machine) and the system will take care of the overload limit by scheduling them based on previously set preferences.
Photovoltaic Systems: Electronic modules able to convert solar irradiance into electrical energy, usually arranged in arrays or matrices to fulfill the electricity demand of single houses (12 to 14 modules), buildings (matrices with up to hundreds of modules) or cities (set of matrices usually placed in the country).
Hybrid Residential Electrical Systems (HRES): Buildings where photovoltaic or other renewable sources are installed along with the traditional connection to the electricity grid, these are active entities in the network, also referred as prosumers.
Building Management Systems (BMS): A control system (algorithm) integrated with modern buildings heavily equipped with sensors and automatic systems (heating, ventilation, air conditioning, surveillance, alarms, electronic doors...) able to collect, process and extract knowledge from the building itself and the surrounding environment and capable to take the optimal actuations to automatically fulfill the comfort and quality of life requirements for the inhabitants, maximize the building lifetime, lowering its environmental impact, operational costs and maintenance.
Smart Grid: The electric energy network of the future, where bidirectional flow of energy will be possible both at transmission and distribution levels, where end users will become prosumers (double role of producers and consumers of electrical energy) and information about network health, power flows, statistics and consumption will be exchanged and be available in real-time.
Renewable Energy Sources: Sun, wind, waterfalls, tides and other natural energy reservoirs, naturally replenished, that can be exploited to generate electrical energy and have a low environmental impact with respect to fossil fuels thus reducing wastes, carbon emissions and global warming.