India is one of the largest developing countriesacross the world, and currently real estate sector (in residential and commercial building’s area) growing approximatelyby 10% annually. The energy demand is increasing in space heating and cooling field because of not only on the growing real estate but also due to high variation between peak seasonaltemperatures. The passive heating and cooling system playing animportant role to meet such energy demand. Earth air tunnel heat exchanger is one of the passive systems, which utilises the undisturbed earth temperature to heat and cool the buildings. Authors feel its importance for space heating and cooling of the building, and rigorouslyreviewed the energy conservation aspect of EATHE.The mathematical modelling, optimization, and economic viabilityare presented in this paper. The review also focuses on the design and layout of earth air tunnel heat exchanger for a residential building.

For this themed issue of Nanomaterials and Energy (NME) we had the opportunity of conducting an interview with Dr. Todd G. Deutsch. Dr. Deutsch is a Senior Scientist in the Hydrogen Technologies & Systems Center at the National Renewable Energy Laboratory in Golden, Colorado. He has been a member of the Turner photoelectrochemicalhydrogen production group at NREL since August 2006. He works on identifying and characterizing appropriate materials for generating hydrogen fuel from water using sunlight as the only energy input. Recently, his work has focused on ternary nitride materials grown by molecular beam epitaxy and corrosion remediation strategies for high-efficiency III-V photoelectrodes. In each of the past six years he has been honored as an Outstanding Mentor by the United States Department of Energy, Office of Science in recognition of his work as an advisor to over 25 students in the Science Undergraduate Laboratory Internship program at NREL.

This article features the application of electrochromic (EC) devices for displays and the efforts made to improve the switching speed and contrast performance of these devices. The article primarily focuses on the layer-by-layer (LbL) assembly deposition technique to deposit thin films of EC materials ranging from organic, inorganic and conducting polymers. Device sizes were varied for comparison of the performance of the lab-made prototype device with the commercially available “small pixel” size displays. EC devices fabricated by LbL assembly, as shown with poly(3,4-ethylenedioxythiophene) results, obtained with a switching speed of less than 30 ms and make EC flat-panel displays possible by adjusting film thickness, device size and type of material. The high contrast value (84%) for ruthenium purple suggests that its LbL films can be used for low-power consumption displays where contrast, and not fastest switching, is of prime importance.

Carbon nanotubes (undoped CNTs) and nitrogen-doped CNTs (N-CNTs, 2·6 and 5 at.%) were synthesized using a floating catalyst chemical vapor deposition (CVD) method with ferrocene and xylene, pyridine, or acetonitrile. The CNTs were further treated in acid (3:1 HNO₃:H₂SO₄ mixture for 24 h) or in oxygen plasma for 10, 30, or 50 min. The as-produced and acid/plasma treated CNTs were characterized by microscopic and spectroscopic techniques to understand the modification of structures by different treatment procedures. Electrochemical surface areas of the doped and undoped CNTs before and after acid/plasma treatment were studied. It was observed that the electrochemical surface area was significantly low (∼10^-5 to 10^-6 m²) due to limited exposure and wettability of the CNTs on the exposed electrode area. Cyclic voltammetry was also performed to evaluate the effects of these treatments on the capacitance behavior of electrodes. The specific capacitance of CNTs based on the electrochemical surface area was in the order of ∼0·3–8·0 F/g or ∼2000–18000 F/m², which could be attributed to double layer or Faradaic reactions. It was observed that optimized plasma oxidation or surface modification conditions are necessary to achieve maximum specific capacitances. Plasma duration of 10, 30 and 10 min led to maximum specific capacitance for undoped CNTs, 2·6% N-doped CNTs and 5% N-doped CNTs, respectively. Further improvements in specific ca-pacitances necessitate suitable electrode design, selection of electrolyte and charging/discharging conditions. Overall, such low specific capacitances of CNTs in a physiological electrolyte are of critical importance for applications in energy storage in low-powered microreactors or implantable biomedical devices. Supplementary information is available at http://www.icevirtuallibrary.com/upload/10.1680nme.12.00033_SupplementaryInformation.pdf

The progress of graphene research is growing very fast after the discovery of graphene in 2004. This is no doubt that commercialization of graphene will center in the future of graphene. The key challenge is the scale-up production of graphene or graphene-based materials. The hope has been lightened by several breakthrough results introduced above. However, the reproducibility is still concerned, as it is difficult to control the uniformity of individual graphene sheets from “top down” method. It also may be affected by the irregular edge of graphene and randomly dispersed functionalities on graphene sheets. The state-of-the-art techniques are also needed to achieve well-controlled microstructure of functionalized graphene and its derivatives. The article reviewed graphene functionalization and its application to polymer composite materials.

The authors have developed a silver-nanoparticle-based ink formulation for aerosol-jet-based printing technique called "Maskless Mesoscale Material Deposition" or M³D™. A wet chemistry precursor-based approach was used to prepare ligand-capped silver nanoparticles where the reduction of silver salt was carried out in a controlled organic media. This synthesis yields 4–5-nm particles, which were characterized using transmission electron microscopy, X-ray diffraction, UV-Vis Absorption spectroscopy and thermogravimetric analysis (TGA). TGA results show weight loss and sintering at low temperature (~170ºC) due to the burning off the ligands. Low-temperature sintering makes the use of this ink attractive for printing conductive patterns on flexible substrates such as Kapton or photo paper. A four-point probe resistance measurement was done on printed tracks, which yields conductivity ~40% of bulk silver.

Renewable energy is the key to creating a clean energy future for the world. Energy conversion cells play important roles in realizing this goal. In this review article, the authors addressed the issues regarding energy conversion cells in a fresh and broad perspective. The authors checked different energy conversion paths from solar energy to electrical energy and showed a simple picture of energy conversion. The authors then went through the working principles of solar cells in terms of charge carrier generation, separation and transport/collection. The comparison between different energy conversion cells, including solar, thermoelectric, electrochemical and photoelectrochemical cells by exploring the working principles of each kind of these cells was studied. It was shown that the working principles behind these cells are quite similar, following a simple energy conversion picture. The aim of this article is to explore the close connections between different energy conversion cells and the essence behind.

Organic solar cells are considered as low-cost photovoltaic technology driven by potentially reduced cost production via high throughput processes, such as printing and lower cost of starting materials. However, commercial realization of this technology is hindered by poor device lifetimes due to environmental degradation of the devices. Under standard test conditions, these devices show lifetimes much shorter in comparison with conventional silicon or other inorganic thin-film solar cells. The lifetimes of organic solar cells are strongly dependent on device processing, measurement (temperature, humidity and light intensity) and encapsulation conditions in addition to intrinsic nature of the constituent materials and their reactivity with each other. Recently, there has been a conscious effort to improve the lifetimes of organic solar cells and strategies such as incorporation of oxide buffer layers, change in the device architecture to inverted geometry and improved materials have been demonstrated to result in improved device lifetimes. In this manuscript, the authors present a review of the degradation in organic solar cells and associated mechanisms, approaches undertaken to improve the device reliability characteristics and lifetimes, the methods to study degradation and finally a brief discussion on encapsulation of the devices.