No abstract

Active shading systems in buildings have emerged as a high performing shading solution that selectively and optimally controls daylight and heat gains. Active shading systems are increasingly used in buildings, due to their ability to mainly improve the building environment, reduce energy consumption and in some cases generate energy. They may be categorized into three classes: smart glazing, kinetic shading and integrated renewable energy shading. This paper reviews the current status of the different types in terms of design principle and working mechanism of the systems, performance, control strategies and building applications. Challenges, limitations and future opportunities of the systems are then discussed. The review highlights that despite its high initial cost, the electrochromic (EC) glazing is the most applied smart glazing due to the extensive use of glass in buildings under all climatic conditions. In terms of external shadings, the rotating shading type is the predominantly used one in buildings due to its low initial cost. Algae façades and folding shading systems are still emerging types, with high initial and maintenance costs and requiring specialist installers. The algae façade systems and PV integrated shading systems are a promising solution due to their dual benefits of providing shading and generating electricity. Active shading systems were found to save 12 to 50% of the building cooling electricity consumption.

Similar to many fast growing countries, the United Arab Emirates (UAE) witnessed fast population and urbanization growth. The building sector accounts for a major share of its electricity consumption, reaching up to 70%. To encourage sustainable development and reduce energy consumption and emissions, the government introduced a sustainability initiative called “Estidama”, which employs the use of the Pearl Building Rating System (PBRS). Government buildings, which constitute 20% of the built environment, aim to lead the way, and are therefore required to attain a high level of achievement, based on their PBRS ranking (minimum of two out of five pearls). Schools, led by Abu Dhabi Educational Council (ADEC), are governmental buildings and aim to attain a higher level of achievement (three out of five pearls). The ADEC plans to build one hundred schools to be built by 2020, through its Future Schools Program. Over half of the schools have been completed, but only 20% reached the targeted rating (of three out of five pearls). The Renewable Energy (RE) application in the UAE is minimal, although it represents 25% of the local rating code. The objective of this paper is to explore the sustainable performance of one representative school that did not reach the desired green rating level, with the objective to assess opportunities for an enhanced performance. This is done through testing the performance and the application of three RE systems comprising of photovoltaics (PV) array, an absorption cooling system and a geothermal cooling system through Transient Systems Simulation (TRNSYS) software. Cumulatively, implementation of these options results in RE potentially contributing to 19% of the school’s annual energy consumption, enhancing the school’s performance by up to 14 additional credit points, and reaching the target level of achievement (a three pearl rating). Furthermore, system integration of RE into the existing school were also considered. Results indicate the significant potential of integrating RE systems in future schools in hot climatic contexts, for an improved energy performance.

Solar thermal-powered desiccant dehumidification systems are attracting attention for cooling load-dominated climates. However, their performance varies substantially from place to place depending on climatic conditions, which therefore warrants a tailored design and specification at each geographical location. The current article attempted to investigate the feasibility of extending an existing solar thermal system in a school building in Abu Dhabi to provide dehumidification for the existing air condition system through a desiccant system. The system performance was predicted through a Transient System (TRNSYS) Simulation model to determine the energy savings achieved by the solar-assisted dehumidification system. The current articles determined the effect of fluid flow rate, solar radiation concentration, and heat exchanger effectiveness at the dehumidification of the fresh air as well as energy saved by the proposed system. It was concluded that the system can remove 35% moisture from the air, simultaneously saving 10% of the building’s energy. The system cost and benefit analysis revealed a payback period of 7.5 years, considered slightly higher for an attractive investment in such systems.