Building energy-consumption status worldwide and the state-of-the-art technologies for zero-energy buildings during the past decade

This article reviews the basic principles of and recent developments in electrochromic, photochromic, and thermochromic materials for applications in smart windows. Compared with current static windows, smart windows can dynamically modulate the transmittance of solar irradiation based on weather conditions and personal preferences, thus simultaneously improving building energy efficiency and indoor human comfort. Although some smart windows are commercially available, their widespread implementation has not yet been realized. Recent advances in nanostructured materials provide new opportunities for next-generation smart window technology owing to their unique structure-property relations. Nanomaterials can provide enhanced coloration efficiency, faster switching kinetics, and longer lifetime. In addition, their compatibility with solution processing enables low-cost and high-throughput fabrication. This review also discusses the importance of dual-band modulation of visible and near-infrared (NIR) light, as nearly 50% of solar energy lies in the NIR region. Some latest results show that solution-processable nanostructured systems can selectively modulate the NIR light without affecting the visible transmittance, thus reducing energy consumption by air conditioning, heating, and artificial lighting.

Switchable Materials for Smart Windows

Multifunctional smart windows are successfully fabricated by assembling inkjet printed CeO2/TiO2 and WO3/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) films as the anode and cathode, respectively. Large optical modulation (more than 70% at 633 nm), fast switching (12.7/15.8 s), high coloration efficiency (108.9 cm2 C−1), and excellent bistability are achieved by the assembled smart windows. The multifunctional smart window not only can be used as typical electrochromic window, which can change its color to dynamically control the solar radiation transmittance through windows or protect privacy during the day, but also can be used as energy-storage device simultaneously. The designed smart window releases the stored energy to light the bulbs and power other electronic devices at night while its color gradually reverts to transparent state. Moreover, the level of stored energy can be monitored via the visually detectable reversible color variation of the window. The fascinating multifunctional smart windows exhibit promising features for a wide range of applications in buildings, airplanes, automobiles, etc.

Inkjet Printed Large Area Multifunctional Smart Windows

In this study, a comprehensive review focusing on key strategies of energy saving and climate control technologies for greenhouses is presented. Following the brief and concise assessment of existing greenhouse systems in terms of their role in total energy consumption; cost-effective, energy-efficient and environmentally friendly technologies are analyzed in detail for potential utilization in greenhouses for notable reductions in energy consumption and emission levels. The technologies considered within the scope of this research are mainly renewable and sustainable based solutions such as photovoltaic (PV) modules, solar thermal (T) collectors, hybrid PV/T collectors and systems, phase change material (PCM) and underground based heat storage techniques, energy-efficient heat pumps, alternative facade materials for better thermal insulation and power generation (heat insulation solar glass, PV glazing, aerogel and vacuum insulation panel, polycarbonate sandwich panels), innovative ventilation technologies using pre-heating and cooling (high performance windcatchers) and efficient lighting systems. The findings from the research clearly reveal that up to 80% energy saving can be achieved through appropriate retrofit of conventional greenhouses with a payback period of 4–8 years depending on climatic conditions and crop type.

Renewable and sustainable energy saving strategies for greenhouse systems: A comprehensive review

This paper describes the application results of a previous and current EU-project on super insulating glazing based on monolithic silica aerogel. Prototypes measuring approx. 55×55 cm 2 have been made with 15 mm evacuated aerogel between two layers of low-iron glass. Anti-reflective treatment of the glass and a heat-treatment of the aerogel increases the visible quality and the solar energy transmittance. A low-conductive rim seal solution with the required vacuum barrier properties has been developed along with a reliable assembly and evacuation process. The prototypes have a centre heat loss coefficient below 0.7 W/m 2  K and a solar transmittance of 76%.

Super insulating aerogel glazing

Energy conservation in building arena is essential issue for achieving sustainable environment. However, buildings experienced significant amount of heat gain or loss through window and this will affect the thermal comfort of buildings׳ occupants. Building without window is able to save energy, but it is not recommended due to the benefits of natural light on visual comfort and the biological effect of natural light on humans. Hence, window design plays important role in building architect. One of the essential parts of window is the glazing. Selecting a window glazing is complicated when energy saving and daylighting aspects of a building are considered concurrently. Optimization techniques offer a balance solution for the contradictions in selecting a window glazing of energy-efficient building. This paper intended to reveal the impacts of window glazing on the energy and daylighting performances of building through the previous researches. Then, the optimization techniques used by various researchers in choosing a glazing are highlighted. The emerging glazing technologies were discussed as well.

W. J. Hee

Papers

The role of window glazing on daylighting and energy saving in buildings