|Yusuf Latief||Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia|
|Mohammed Ali Berawi||Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia|
|Ario Bintang Koesalamwardi||Construction Engineering and Management, Faculty of Engineering, Universitas Agung Podomoro, Jakarta 11470, Indonesia|
|Leni Sagita||Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia|
|Ayu Herzanita||Department of Civil Engineering, Faculty of Engineering, Universitas Pancasila, Srengseng Sawah, Jagakarsa, South Jakarta 12640, Indonesia|
Housing development, as part of economic development, must be supported by energy availability in order to achieve sustainable growth. One of the approaches to supporting renewable energy promotion is to design and build energy efficient housing. However, the optimal design of such buildings faces two conflicting requirements, namely the consideration of cost effectiveness and minimum environmental impact. The high costs of energy efficient buildings, such as the near Zero Energy House (nZEH), are due to the high price of the materials and equipment used, such as photovoltaic (PV) panels, insulation and other supporting materials. Indonesia is situated on the equator and benefits from sunlight throughout the year. Nonetheless, this potential has not been fully realized, as the solar-generated energy technology for housing comes at a high price. Therefore, the objective of this study is to find the cost optimum combination of validated design variables for an nZEH which suit the tropical climate conditions of Indonesia. Experiments and a case study are employed in the study to validate the design variables for an optimum nZEH design, which include building orientation, PV panels, fenestration, and passive design. The study finds that the cost optimum nZEH design achieved 72 percent site-energy savings and 21 percent savings in the total Net Present Value (NPV) of life cycle costs, with insignificant incremental initial construction costs in enhancing the design.
Design optimization; Near Zero Energy House; Sequential search
As its population continues to grow, Indonesia is currently facing increasing demand for housing and electricity production. A by-product of such rapid development is greenhouse gas emissions. The Centre of Energy Studies at the University of Indonesia has projected that these emissions will grow continuously to an alarming level by 2025 (PEUI, 2006) if Indonesia continues to develop a business-as-usual (BAU) scheme. In the Paris Accord 2015, Indonesia signed a commitment to reduce its greenhouse gas emissions by up to 29% by 2030 (United Nations Framework Convention on Climate Change, 2016); however, to date it has only been able to achieve a 1.49% reduction (INDC, 2015). To maintain social welfare by meeting the basic needs of adequate housing and energy and continuing to keep the enviromental impact at a minimum level, the development of the housing and energysectors needs innovation.
The energy performance of a building is the key element in reducing greenhouse gas emissions and making energy savings. Improving such performance is a cost-effective solution to overcoming climate change and improving energy security. Energy conservation in the building sector has attracted the interest and concern of the world community with respect to environmental conservation (Koesalamwardi, 2014).
In practice, it is very difficult to achieve zero energy consumption in a building. Buildings that consume just a little more energy than that generated are called near zero energy buildings (nZEBs), while an nZEH is a residential building that consumes a little more energy than it produces. Buildings that can generate energy usually use solar panels on their roofs and facades. By collecting energy from the sun, an nZEH can use its own generated energy and minimize energy consumption from outside sources (Marszal et al., 2011). Indonesia's tropical climate provides the potential for the development of nZEHs integrated with photovoltaic (PV) panels. However, this potential has not been fully explored due to the expensive technology of solar power generation systems (Dhany, 2013).
Reducing energy consumption without compromising living standards, e.g. indoor room temperature and comfort, is an important issue in the building construction industry. In addition, this problem also creates a contradiction for energy-efficient building design, which typically uses expensive materials and technology, and which directly affects the overall cost of construction (Milajic et al., 2013). This requires optimal use of green technology and attention to construction costs, so that energy-efficient building technologies will be economically feasible.
Buildings with high energy performance, such as the nZEH, should also be economically viable. Strategies and solutions are needed to reduce energy consumption for such buildings and to continually provide energy from renewable sources (Milan et al., 2012). In recent years, many energy conservation technologies have been developed, but the use of these tools does not guarantee optimal energy savings. This is because energy consumption is highly dependent on the combination and use of these tools, so these factors should be planned and optimized in order to obtain the best levels of energy saving (Ooka & Komamura, 2009). The purpose of this research is to develop an nZEH design with optimal costs using a sequential search optimization algorithm.
To conclude, this study has determined an nZEH design at optimum cost, using nZEH design variables such as PV panels, azimuth (building orientation), fenestration (window-to-wall ratio), and glazing for windows. The design variables were combined and simulated using sequential search numerical rules, with the help of building performance simulation software. The results show that common construction materials, e.g. concrete hollow bricks and terracotta roof tiles, are suitable and represent low-cost heat insulation materials for tropical houses. Comfortable indoor room temperatures can be achieved with minimal usage of air conditioning, by positioning the house so it is not directly facing the sun, and applying 60 cm eaves and overhangs on all windows. The application of these can also reduce the initial construction cost by not having to use expensive glazing. The optimum window-to-wall ratio, which ranged from 15% to 40%, can provide adequate natural lighting, while minimizing heat radiation from the sun. By applying PV panels, electric consumption can also be reduced significantly. The electric power generated by the PV panels can also be exported to the central power grid, thus cutting electricity bills thanks to the net-metering incentive scheme.
The design optimization algorithm will sequentially search for the optimum combinations, thus generating maximum cost savings. Therefore, the optimization process will also eliminate unnecessary, unsuitable, and/or expensive design variables for tropical climates; for example, boilers, asphalt roof shingles, fiberglass wall insulations and LED lighting. Based on the cost optimum design parameter selection, the incremental construction cost for upgrading the design towards nZEH design concept is less than 5% to the initial construction cost of conventional design. The optimized design of the nZEH shows a significant annual maintenance and operational cost reduction, resulting in a lower NPV of cost compared to the conventional house design of up to 21%.
The authors would like to acknowledge the research grant from the Ministry of Research, Technology and Higher Education Republic of Indonesia (Kemenristekdikti) as funding support for the research project (Hibah Penelitian Unggulan Perguruan Tinggi 2016 Nomor:1181/UN2.R12/HKP.05.00/2016).
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