Measurement of natural convection heat transfer in an attic shaped enclosure

Heat transfer by natural convection in triangular enclosures is an area of significant importance in applications such as the design of greenhouses, attics and solar water heaters. However, given its significance to these areas it has not been widely examined. In this study, the natural convection heat transfer coefficients in an attic shaped enclosure were determined for Grashof Numbers over the range 107 to 109. It was found that the measured heat transfer coefficients could be predicted to within 5% by Ridouane and Campo’ (2005) equation (Eqn. 1) for natural convection in a triangular enclosure previously developed for Grashof Numbers in the range 105 to 106.

Nu=0.286*A-0.286*Gr1/4 (Eqn. 1)

As such, it is suggested that this equation may be suitable for predicting the natural convection heat transfer coefficients in full scale attic enclosures.

Enhanced properties in chemically polymerized poly(terthiophene) using vapour phase techniques

Poly(terthiophene) is an electronically conducting polymer with potential applications in solar energy devices. In the present study a series of poly(terthiophene) (PTTh) films are chemically polymerized (CP) at various temperatures and compared with a novel method of vapour phase polymerization (VPP). Utilizing the thiophene trimer (terthiophene) as the starting material, polymerization is achieved with Fe(III) tosylate. The films are characterized by their Raman and absorption spectra, in addition to differential scanning calorimetry (DSC), optical microscopy, electrochemical impedance spectroscopy (EIS) and four-point probe surface conductivity measurements. From the spectroscopy studies, increased conjugation length of the polymer chains with decreasing temperature or vapour phase polymerization is evident. More surprisingly, DSC results indicate the order of the polymer chains is dramatically enhanced by vapour phase polymerization and the D.C. conductivity is an order of magnitude higher for VPP compared with traditional CP films. Additionally, the optical micrographs reveal a significantly different morphology than the films cast from solution.

Assessment of thermal comfort near a glazed exterior wall

In many highly glazed buildings, the thermal comfort of the occupants will tend to be related to the incoming solar energy and the solar heat gain coefficient of the glazing. Many real buildings tend to be deep relative their height and therefore, areas close to the facade receive a much greater amount of the incoming energy than those farther from it. In turn, this imbalance leads to occupants near the facade experiencing a high dissatisfaction with their thermal environment (near-facade zone). This study experimentally examines the thermal environment of occupants near the facade of a glazed building wall. It presents results for Fangers’ predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD) and explores some options for improving the thermal environment in this near-facade zone.

Designing for thermal comfort near a glazed exterior wall

In many highly glazed buildings, the thermal comfort of the occupants will tend to be related to the incoming solar energy and the heat transfer behaviour of the glazing. In this study, several glazing systems were designed using the software tools VISION 3 (University of Waterloo 1992) and WINDOW-6 (Lawrence Berkeley National Laboratory 2011), with a view to improving thermal environment of occupants near the glazed wall of a commercial office. The systems were fabricated and experimentally tested to validate the software modelling results. Subsequently, the glazing systems were retro-fitted to the office and tested in situ for a summer month. Results of this testing, in the form of Fangers’ predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD), are presented, and some options for improving the thermal environment in this near-façade zone are discussed.

Experimental and simulation study of the impact of increased photovoltaic integration with the grid

The abundance, availability, and climate-friendly characteristics of solar photovoltaic (PV) energy encourage nations around the globe to adopt it to assist in overcoming global warming as well as build a sustainable society for the future. The intermittent nature of solar energy generation and the associated power electronic inverters with connected consumer loads creates a number of potential challenges in integrating large-scale PV into the grid that affects power quality of the distribution networks. This paper investigates the impacts of varying PV integration into the grid through experimental and simulation studies. Initially, several experiments were conducted with varying PV penetration and load conditions using the Renewable Energy Integration Facility at CSIRO, Newcastle, Australia. Later, a simulation model was developed that mimics the experimental facility used at CSIRO to investigate the adverse impacts on integrating large-scale PV into the grid using the power system simulation software PSS Sincal. Experimental and simulation analyses clearly indicate that integration of PV into the grid causes power quality issues such as voltage instability, harmonic injection, and low power factor into the networks and the level of these impacts increases with the increase of PV penetration. © 2014 AIP Publishing LLC.

Colour change on different body regions provides thermal and signalling advantages in bearded dragon lizards

Many terrestrial ectotherms are capable of rapid colour change, yet it is unclear how these animals accommodate the multiple functions of colour, particularly camouflage, communication and thermoregulation, especially when functions require very different colours. Thermal benefits of colour change depend on an animal's absorptance of solar energy in both UV–visible (300-700 nm) and near-infrared (NIR; 700-2600 nm) wavelengths, yet colour research has focused almost exclusively on the former. Here, we show that wild-caught bearded dragon lizards (Pogona vitticeps) exhibit substantial UV–visible and NIR skin reflectance change in response to temperature for dorsal but not ventral (throat and upper chest) body regions. By contrast, lizards showed the greatest temperature-independent colour change on the beard and upper chest during social interactions and as a result of circadian colour change. Biophysical simulations of heat transfer predicted that the maximum temperature-dependent change in dorsal reflectivity could reduce the time taken to reach active body temperature by an average of 22 min per active day, saving 85 h of basking time throughout the activity season. Our results confirm that colour change may serve a thermoregulatory function, and competing thermoregulation and signalling requirements may be met by partitioning colour change to different body regions in different circumstances.

Dust as an unalterable deteriorative factor affecting PV panel's efficiency: why and how

Electricity generation from solar energy has a great potential since it relies mainly on an abundant and clean source. However, there are many alterable and unalterable factors that can govern a PV module's efficiency. Dust is one of the location-dependent environmental factors that falls under the unalterable factors group. It can degrade the efficiency of a PV panel by causing physical damages, by attenuating the incoming solar radiation and by causing temperature rise, which results in changes in panel's electrical characteristics. Degree of degradation depends mainly on the deposition density, which is governed by various factors. Dust accumulation of 20 g/m2 on a PV panel reduces short circuit current, open circuit voltage and efficiency by 15–21%, 2–6% and 15–35% respectively. This work reviews, elaborates and summarizes the effects of dust on solar panel efficiency and the factors governing dust deposition on PV panel.