Is it time to embrace building integrated Photovoltaics? A review with particular focus on Australia
Introduction
The concentration of carbon dioxide (CO2) in the atmosphere has been increasing in an alarming rate over the past century. A report by Kang et al. (2016) showed that the CO2 concentration was 40% higher in 2016 than that in mid-1800s. The changes in the concentration levels of nitrous oxide (N2O) and methane (CH4) are also significant (Kang et al., 2016, Mathy et al., 2018, Sreekanth, 2016).
There are a number of human activities that have resulted in the generation of GHG such as electricity generation, agriculture and industrial processes. Among all these activities, the production of electricity represents by far the largest source of GHG emission. The contributions by different sectors to the GHG emission are illustrated in Fig. 1 (C2ES, 2017).
The energy sector produces electricity in various ways; among these burning of fossil fuel dominates the GHG emissions. The fast-growing world is constantly increasing its demand for energy to keep up with the economic growth and development. According to the TPES, the demand for energy increased by 150% between 1971 and 2015 globally, and unfortunately the majority of the energy companies still depend on traditional electricity sources (e.g. coal-fired power plants).
Burning of fossil fuels to meet the energy demand due to the unprecedented economic growth and development plays the key role in the upward trend of CO2 emissions, which already have significant influence on the environment. The amount of CO2 emissions per year since the industrial revolution has gone up dramatically from near zero to over 36 GtCO2 in 2018 (IEA, 2018) (Fig. 2). The UNFCCC decided to curb the overall greenhouse gas emissions to keep the global temperature rise below 2 °C for this century (COP-21, 2015).
Looking at the trend of economic growth, it is undeniable that the demand for energy is rising and the fossil fuel sources are depleting. Facing this challenge, the search for alternative energy sources and the development of smart technologies to utilise these sources have been a centre of discussion during the last few decades. Acceptable sources are those which have less/zero impact on the environment, and renewable in nature. It is beyond doubt that sustainable energy practices will help to secure future energy supply, technological advancements, employments and regional development.
Solar energy is a reliable source to produce power. It is incredible to see how much solar irradiation is received by the earth every year. Quantitatively the amount of energy is 10,000 times more than the energy required for mankind in a single day (Liu et al., 2012, Zhang et al., 2013). However, the real challenge is how to harness that energy at a reasonable cost. A solar PV system converts solar energy into electrical energy. Electricity generation using a PV module contributes less (20–30 g carbon dioxide equivalent (CO2-e)1/kWh during production of materials considering an operational lifetime of 25 years including some degradation) to environmental pollution and is easy to install on a building roof (Frischknecht et al., 2015). The interest for this technology is growing since the cost is dropping substantially, and with this, electricity can be supplied to remote areas (Rawat et al., 2016, Rodrigues et al., 2016, Sahoo, 2016). A scenario of price reduction of PV panels across the world is shown in Fig. 3 (Council, 2016). As we can see, in Australia, the cost for solar power generation dropped to a level which was even lower than the previous year projection. The progress in this field is remarkable, especially in the development of building integrated photovoltaics (BIPV) systems, where PV panels are part of construction such as roof, windows, façades and shading devices (Kumar and Kumar, 2017, Ram et al., 2017, Zuo et al., 2017).
Recent advancements in technologies have substantial impacts on the research and development of PV systems. A few decades ago, only small scale PV panels were studied for serving some specific purposes. Nevertheless, these days the focus has been shifted to large scale grid-connected PV systems (IEA, 2013, Timilsina et al., 2012). At present, about 90% PV systems are grid-connected. The current share of BIPV in PV market is about 2.5% and it is predicted that this will rise to 13% by 2022 (Masson and Kaizuka, 2018).
Employment of a BIPV system on a building surface does not only serve as the envelope but it also generates electricity (Azadian and Radzi, 2013). Another benefit compared to a non-integrated system is that the installation of BIPV does not need any additional space (Cucchiella et al., 2015, Kim et al., 2017, Tripathy et al., 2017). The integrated design can ultimately reduce the total material cost as well since BIPV does not need assembly components such as brackets and rails.
The objective of the study is to review recent progress in BIPV technology and their sustainability and economic feasibility in terms of EPT and economical payback time, respectively. A scenario of the current carbon emission in Australia and how the country is progressing in reducing the GHG emissions to fulfil the promise in Paris Agreement are illustrated. In addition, the major challenges that Australia are facing to adopt this technology is identified. Last but not the least, an attempt is made to explore current limitations of BIPV technology and pinpoint openings for further research.
Section snippets
Energy and CO2 emissions in Australia
The combustion of any carbon-containing substance results in the generation of CO2. Petter Jelle et al. (2012) gave an alarming prediction that the power industry emissions would increase from 10.9 to 18.7 Gt of CO2-e from year 2005 to 2030. In Australia, the majority of CO2 emission comes from the combustion of fossil fuels, such as coal, oil (petrol & diesel) and natural gas (methane) (Azzi et al., 2015, Buckman and Diesendorf, 2010). Fig. 4 shows the annual CO2-e emission in Australia
Solar irradiation in Australia
A location suitable for harnessing solar energy should meet certain criteria, such as enough solar irradiation, close to the load centre and availability of installation sites. In Australia, solar irradiation is a fortune since it receives the highest amount of irradiation per square metre in the world. It is reported that the amount of irradiation received by Australia annually is a few thousand times higher than its annual energy consumption (Geoscience-Australia). Though solar radiation is
Building integration of PV cells
Table 2 summarises the efficiencies of different solar cell materials and their practical applications. As we can see, mono and polycrystalline cells are considerably efficient among the listed PV cells. They are the typical cells for most of the applications.
The idea of integrating PV cells on a building surface is to replace part of the construction such as roof, skylights or façade with photovoltaic materials which can convert solar energy to electricity. Therefore, the system not only acts
Standards for BIPV
The major BIPV tests specified by IEC (IEC 61215, 2016) and UL (UL 1703, 2002) are listed in Table 4. As can be seen, the US standards are more thorough compared to the IEC standards. Some tests such as impact, push, temperature cycling and fire hazard are very important but not included in the list of IEC – 61215. On the other hand, useful tests like UV and low irradiance are not included in the UL 1703 list. It is recommended for new manufacturers to develop their products based on the market
EPT and economical payback time for PV systems
To develop a PV product, it is very important to conduct a cost-benefit analysis and life cycle assessment which includes determination of the EPT and economical payback time. These two parameters would help to evaluate the sustainability, feasibility and financial benefits of the system. Two steps can be taken to conduct the EPT analysis (Alsema and Nieuwlaar, 2000, Laleman et al., 2011, Pacca et al., 2007):
Step 1: Determination of yearly energy output from the system. This can be calculated
Steps involved in selecting a BIPV system
Choice of appropriate PV modules for a building is crucial which can be made based on certain selection criteria. There are many different products in the market but not all of them are suitable for a specific building application. This section will discuss the aspects that need to be taken into consideration when choosing a system.
The first step involves selecting the appropriate location for the BIPV installation. In Australia, a north facing position is considered suitable since it will
Future prospects of solar energy in Australia
As mentioned in Section 3, Australia receives the highest amount of solar irradiation per square metre in the world. It is no doubt that solar energy has great potential in Australia. A recent article published in Renew Economy (Parkinson) released the data of solar generated power from 13-Sep-2018 to 19-Sep-2018 to compare with the energy generated from other sources. The data suggest that in Victoria, solar is generating more power between the hours of 10:00–14:00 than brown coal fired power
Low efficiency
The biggest problem of every PV system is its low energy conversion efficiency and the dependency on weather conditions. The performance is determined by the amount of electrical energy produced by the system against the amount of solar irradiation received by the system. Currently the solar-to-electrical energy conversion efficiency is approximately 25% and the scenario is very unlikely to change soon (Obeidat, 2018, Peng et al., 2017, Sukumaran and Sudhakar, 2018). The poor efficiency of a
Discussion
The aim of this study is to present the current situation of carbon emission in Australia and how renewable energy systems, particularly BIPV, can contribute to the reduction of the current level of CO2-e emission. Recently, a report suggested that Australia is categorised among the countries that are performing worse in developing energy efficient buildings (Thorpe, 2017). In Australia, buildings account for 20% of the total energy consumption and are responsible for 21% GHG emission.
Conclusions and future research needs
In Australia, limited attention has been gived to the BIPV system despite its wider application across the world. We have reviewed recent advancements in BIPV systems in terms of sustainability, and financial and environmental benefits. Although a particular focus is placed on Australia, the development of BIPV systems in this country also provides lessons to many other countries in a similar situation.
Based on our literature review, the following concluding remarks can be made:
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Australia is
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