By Kehinde Temitope Alade, Akinloye Fatai Lawal and Daniel Akinyele
In the face of increasing human population around the world, it is likely that the global energy demand is doubled by the year 2050. Globally, reducing greenhouse gases and increasing energy efficiency in the household sector is the reason for developing and testing new solutions in private and public buildings, based on the Information and Communication Technologies. A great deal of groundwork has been done, and is still in motion to develop and implement energy-efficient technologies to meet the users’ increased energy needs.
Over the years, buildings represent a significant and rapidly growing energy-consuming sector. As temperatures are rising, globally, weather is becoming extreme and less predictable, thus, posing increased danger for communities with energy passive buildings.
Studies have shown that buildings in most developed countries consume up to 40 percent of electricity, with more than 70 percent of that primarily used for heating, cooling, and lighting. Furthermore, about 20 percent of the energy used by buildings can, potentially, be saved by handling faults, including malfunctions and unnecessary operation (e.g., keeping lights on when not in use). On the other hand, the use of inefficient appliances has been identified as the major factor responsible for increased energy consumption in developing countries. Though energy-efficient lighting systems such as compact fluorescent light and light emitting diodes have been introduced in several parts of developing countries, there is still the need to ensure that other appliances are also energy-efficient in order to minimize energy consumption. These are some of the factors that make the energy conservation, efficiency and sustainability a progressively crucial global subject.
Although the term “smart” materials and technologies may be difficult to explain, the following features will be their distinctive characteristics:
- Immediacy – they respond in real-time.
- Transiency – they respond to more than one environmental state.
- Self-actuation – intelligence is internal to rather than external to the ‘material’.
- Selectivity – their response is discrete and predictable.
- Directness – the response is local to the ‘activating’ event.
All materials, both the traditional and the “smart”, conserve energy. However, energy-exchanging “smart” materials are uniquely capable to recover internal energy in a more “usable” form. Among the materials in this category are smart roofs, piezo-electrics, thermo-electrics, photo-voltaics, pyro-electrics, photo-luminescents and others. This article focuses on the smart roof applications and photovoltaic technologies.
Smart materials are directly effective in various types of energy (i.e. they can yield luminous, thermal or acoustic energy). In addition, studies have shown their indirect effects on systems (enhancement of energy generation, reduced wear of mechanical equipment, etc). The aforementioned features are very useful to the designer who can evaluate the use of smart materials and systems in relation to the design of environments.
Although the energy conversion efficiency for smart materials such as photovoltaics and thermoelectrics is typically much less than for more conventional technologies, the potential usability of the energy is much greater. For example, the direct relationship between input energy and output energy renders many of the energy-exchanging smart materials, including piezo-electrics, pyroelectrics and photovoltaics, as excellent environmental sensors. The form of the output energy can further add direct actuation capabilities such as those currently demonstrated by electrostrictives, chemoluminescents and conducting polymers.
There is a great deal of discussion in the roofing industry about cool roofs, green roofs, garden roofs, vegetated roofs and other roof systems that are expected to be more energy efficient and ecologically friendlier than conventional roofs. In the past, a typical residential homeowner would be mostly concerned with the appearance and durability of the roof, while issues of energy efficiency were often ignored. In recent times however, the concept of smart roofs has emerged. For instance, in mixed climates with both significant heating and cooling loads, the high reflectance that helps in the summer, hurts in the winter by turning away solar energy that would otherwise heat the building. The use of a smart surface that changes reflectance with temperature can now be applied as a clear sheet to the existing steep-slope roof product. The smart roof is also adaptable to concrete and clay tile, cedar shake and painted metal residential roofing.
Photovoltaics (PV) are common energy-exchanging smart materials. They convert solar irradiation energy to direct current (DC) electricity. The generated electricity is then utilized based on the type of appliances in the building, e.g. alternating current (AC) or DC. For DC appliances, the electricity is used directly with the connection of a charge controller and a battery bank to the PV modules, while an inverter is required in order to power the AC appliances.
The PV materials include the silicon crystalline, thin film, hybrid, organic and the nano technologies. The organic and the nanotechnology materials are currently regarded as the new generation technologies.
The solar PV materials are important part of the energy efficiency initiatives or plans in buildings as they are currently used in many parts of the world as roofs and facades. Such an application implies that they are able to serve dual purpose – as part of the building materials as well as clean energy generating systems, which helps to reduce materials of the building infrastructure.
Depending on the building design, the PV systems can be used as building integrated photovoltaic (BIPV) or building attached photovoltaic (BAPV). The common examples of the BIPV are the roof-mounted and facade configurations, while the example of a BAPV is the ground-mounted configuration but also attached to the building. The intent of the BIPV and the BAPV is to ensure sustainable energy supply while the users minimize the grid- energy consumption. This process, together with the use of energy efficient appliances and the demand response has the potential to reduce the energy demand and greenhouse gases (GHGs) around the world.
In conclusion, the widespread application and use of energy-efficient materials, technologies and appliances in all human activities is expected to accelerate the achievement of energy sustainability in the future.
Kehinde Temitope Alade currently lectures at the Department of Project Management Technology in the Federal University of Technology, Akure in Nigeria. His research interests include design management, construction management, energy management in buildings, and infrastructure project management. He has a bachelor's in architecture from Nnamdi Azikiwe University, Awka, Nigeria and a master's in construction management from Loughborough University in the United Kingdom.
Akinloye Fatai Lawal is a fellow of the Nigerian Institute of Building (NIOB). He is also an associate professor of construction project management with specialization in energy management in buildings. He is currently the acting head and the Department of Project Management Technology in the Federal University of Technology in Akure, Nigeria.
Daniel Akinyele is a lecturer at the Department of Electrical & Computer Engineering, Elizade University in Nigeria. He holds a national diploma (distinction) and a bachelor's (first class) in electrical and electronic engineering from the Osun State Polytechnic and the University of Ibadan, Nigeria, respectively. He also holds a master's (distinction) in renewable energy systems technology and a Ph.D. in renewable energy from Loughborough University, United Kingdom and the Victoria University of Wellington (VUW), New Zealand, respectively. He was a senior engineer at the National Agency for Science and Engineering Infrastructure (NASENI), Abuja, Nigeria. Subsequently, he joined the Department of Electrical and Information Engineering in Covenant University, Nigeria as an assistant lecturer. He is registered with the Council for the Regulation of Engineering in Nigeria (COREN).