The effect of building integrated photovoltaic system (Bipvs) on indoor air temperatures and humidity (Iath) in the tropical region of Cameroon

Ekoe a Akata et al. Future Cities and Environment (2015) 1:1 DOI 10.1186/s40984-015-0002-y TECHNICAL ARTICLE Open Access The effect of building integrated photovoltaic system (Bipvs) on indoor air temperatures and humidity (Iath) in the tropical region of Cameroon Martial Aloys Ekoe a Akata1*, Donatien Njomo1 and Blaise Mempouo2,3 Abstract The building sector accounts for around 40-50 % of the energy consumed in developing countries and contribute over 30 % of CO2 emissions. In Cameroon, the electricity access is less than 5 % in rural areas against 50 % in urban areas. All sectors combined the Cameroonian final energy consumption amounts to approximately 5235 kilo-tonnes of oil equivalent (Ktoe) and 73 % of this energy are assigned for residential use. This energy can be considerably reduced with the development of low energy buildings using Building Integrated Photovoltaic (BIPV), since it has been proven an effective solution to achieve significant energy savings and conservation. However, photovoltaic (PV) panels produce a substantial amount of heat, while generating power. Consequently, BIPV’s concept, where the photovoltaic (PV) panel is integrated on the building envelops has significant influence on the amount of heat transfer through the building fabrics, and could affect the indoor air temperatures and the comfort of the occupants, since, it changes the thermal resistance of the building envelops. In this paper, the effect of the BIPV on the indoor air temperatures and humidity (IATH) of a multiple storey buildings under the tropical climatic conditions of Yaoundé, Cameroon has been modelled and analysed. Two cases of BIPV made of 290 m2 area of PV have been considered, i) roof integrated and ii) façade integrated. In addition, building orientation, roof pitch and the building materials are also been explored and optimised to provide the best combination. It has been observed that for both cases, BIPV increases the building’s indoor air temperature by about 4 °C, when compare to a building of the same size without PV integrated. Keywords: Building Integrated Photovoltaic (BIPV); Passive design; Heat transfer; Energy conservation; Thermal comfort; Solar energy Introduction Whatever the building to build or manage, solutions to control energy consumption must be sought. This is true in the world for all types of buildings, industrial, commercial or residential. Before designing or improving a building, it is essential to study its energy needs and energy sources available, and then look for the best adequacy of management systems, distribution networks * Correspondence: 1 Environmental Energy Technologies Laboratory (EETL), University of Yaoundé I, Yaoundé, Cameroon Full list of author information is available at the end of the article and consumer equipment taking into account operating requirements. Energy demand The power industry emissions were 10.9 giga-tonnes of carbon dioxide equivalents (GtCO2e) per year in 2005, i.e. 24 % of global Greenhouse Gas (GHG) emissions, and this is expected to increase to 18.7 GtCO2e per year in 2030 (Jelle et al. 2012). The world population is estimated at 8.2 billion people for an energy consumption of15.3 billion-tone oil equivalent (toe) in 2030 (International Energy Agency (IEA) 2012). There is a statistically relation between © 2015 Ekoe a Akata et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Ekoe a Akata et al. Future Cities and Environment (2015) 1:1 population and economic growth, energy use, and CO2 emissions (Mohd Shahidan et al. 2013). The population growth increase energy use. An important part of this energy is use in the building sector, that represent about 40-50 % of the energy consumed in developing countries and will be responsible nearly 4300 toe of CO2 emissions for these country in 2030 (International Energy Agency (IEA) 2012). In Cameroon, the energy demand still remains unsatisfied and the access to modern energy is very low, in the national average range of 15 % for electricity and 18 % for domestic gas. In addition, the electricity access is less than 5 % in rural areas against 50 % in urban areas. All sectors combined, the Cameroonian final energy consumption amounts to approximately 5235 Ktoe in 2006 (SIE-Cam; AES-Sonel; CSPH, Nkutchet, 04). Tropical building low energy Energy is used for the building comfort that means cooling in tropical region. The construction of low energy buildings is an effective solution that achieves significant energy savings. Low-energy buildings use passive techniques, such as optimal solar gain, and advanced active systems, such as mechanical ventilation with heat recovery, to create comfortable internal environments that have low energy demand. Renewable heating systems including biomass boilers, active solar water heating and ground source heat pumps can be used to supply heating and hot water needs with reduced gas emissions. Solar photovoltaic can be used to provide electricity. Solar energy systems can play an important role in reducing building energy consumption (Hestnes 1999) in tropical region because of it abundance. The building integrated photovoltaic Building integrated photovoltaic (BIPV): The concept where the photovoltaic element assumes the function of power generation and the role of the covering component element has significant influence on the heat transfer through the building envelope. Kimura (Kimura 1994), Taleb and Pitts (Taleb & Pitts 2009), and (Zhai et al. 2008) have illustrated various methods of installing the PV modules into a building for a concept of green building. In modern buildings, windows play an important role in energy performance with respect to heating/cooling loads and artificial lighting requirements. The relationship between window design and building energy performance has been extensively researched (Stegou-Sagia et al. 2007; Iqbal & Al-Homoud 2007; Lee & Selkowitz 2006; Wong et al. 2005; Bodart & De Herde 2002; Zain-ahmed et al. 2002; Mehlika et al. 2000; Al-Homoud 1997). Ciampi et al. (Ciampi et al. 2003) show that carefully designed Page 2 of 10 ventilated facades, walls and roofs can reduce considerably the summer thermal loads. The advantage of integrated photovoltaic over nonintegrated systems is the reduction of construction costs of building materials. These advantages make BIPV one of the fastest growing segments of the photovoltaic industry (Park et al. 2010). For BIPV systems to achieve multifunctional roles, various factors must be taken into account, such as the photovoltaic module temperature, shading, installation angle and orientat (...truncated)