18 results for Anderson, T

  • Designing for thermal comfort near a glazed exterior wall

    Anderson, T; Luther, M (2012-08-17)

    Journal article
    Auckland University of Technology

    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.

    View record details
  • A simple sizing optimization method for wind-photovoltaic-battery hybrid renewable energy systems

    Rahman Tito, MS; Lie, TT; Anderson, T (2013-09-06)

    Conference item
    Auckland University of Technology

    This paper presents a simple methodology to optimize the size of a hybrid wind generator (WG), photovoltaic (PV) module and battery storage system for a given demand. The method utilizes typical meteorological year (TMY) data to calculate hourly power output of a PV module and a WG throughout the year. By changing the combination of PV and WG, the generated energy is matched with the hourly average load of a year. This is done in such a way that the maximum of the total energy deficit in a cluster of hours in between hours of excess energy generations becomes minimum. The required number of batteries is calculated from that maximum of the total energy deficit among these clusters. The combination of WG, PV and battery that satisfies the desired loss of power supply probability (LPSP) and has the lowest total cost is considered as the optimum. A case study has been carried out to size a hybrid renewable energy system (HRES) optimally. The size obtained by this method is verified using an iterative algorithm and a genetic algorithm (GA). It is found that all of these methods give the same result for the same demand.

    View record details
  • Experimental evaluation of low concentration collectors for façade applications

    Piratheepan, M; Anderson, T (2014-05-19)

    Conference item
    Auckland University of Technology

    In this study two possible configurations for a static low concentration ratio façade integrated concentrator were examined using optical ray tracing; the first incorporating a parabolic reflector and the second using a flat reflector element. Subsequently an experimental apparatus was developed and testing conducted to validate the findings of the ray tracing. It was shown that the illumination provided by a parabolic reflector was non-uniform and that this could result in premature failure of the absorber. Further, it was found that a flat booster reflector offered similar variation in concentration ratio to that observed with a parabolic reflector, but provided more uniform illumination. As such, it would appear that a flat reflector provides an ideal compromise for such building integrated solar systems.

    View record details
  • Mathematical modeling of a solar powered humidification dehumidification desalination prototype

    Enayatollahi, R; Anderson, T; Nates, R (2014-05-19)

    Conference item
    Auckland University of Technology

    In recent times the issue of fresh water shortages and salinity contamination of existing water sources has become a serious problem in a number of locations around the world. Hence, developing an environmentally friendly desalination technique is essential. In this work a theoretical model is developed in order to optimize a novel humidification-dehumidification desalination system. A sensitivity analysis was carried out, in order to find the optimum values for air and water flow rates. From this analysis it was found that a maximum of production rate of 1.5 kg/hr.m2 was achievable, however it was also found that this rate was particularly influenced by the incident radiation, the inlet water temperature and the water flow rate.

    View record details
  • Global solar radiation prediction using artificial neural network models for New Zealand

    Ahmad, A; Anderson, T (2014-05-19)

    Conference item
    Auckland University of Technology

    In this study, nonlinear autoregressive recurrent neural networks with exogenous input (NARX) were used to predict global solar radiation across New Zealand. Data for nine hourly weather variables recorded across New Zealand from January 2006 to December 2012 were used to create, train and test Artificial Neural Network (ANN) models using the Levenberg−Marquardt (LM) training algorithm, with global solar radiation as the objective function. In doing this, ANN models with different numbers of neurons (from 5 to 250) in the hidden layer as well as different numbers of delays were experimented with, and their effect on prediction accuracy was analyzed. Subsequently the most accurate ANN model was used for global solar radiation prediction in ten cities across New Zealand. The predicted values of hourly global solar radiation were compared with the measured values, and it was found that the mean squared error (MSE) and regression (R) values showed close correlation. As such, the study illustrates the capability of the model to forecast radiation values at a later time. These results demonstrate the generalization capability of this approach over unseen data and its ability to produce accurate estimates and forecasts.

    View record details
  • Condensation in glazed flat plate solar collectors

    Anderson, T (2014-05-19)

    Conference item
    Auckland University of Technology

    Glazed flat plate solar collectors offer a simple and cost effective approach to heating water. However, on clear nights solar collectors can transfer a significant amount of heat to the atmosphere by radiation. In areas with a cool climate and high relative humidity the radiation heat loss can lead to the temperature of the glazing often reaching the dew-point of the surrounding air, this leads to condensation developing on the glazing. If water condenses on the inside of the glazing and repeatedly drips onto the solar absorber this could lead to damage of the solar collector surface thus shortening its operating life. Also, the build-up of condensation on the glazing can lead to the growth of mould, is visually displeasing to the owner, and means energy must be “wasted” to evaporate the moisture during the following day. This study aims to develop the understanding of the role that condensation plays on collector performance, as well as addressing ways of minimising the impact it has. In doing so, it uses numerical modelling and experimental testing to determine the frequency of condensation in glazed flat plate solar water heaters under typical operating conditions. It shows that climatic factors including relative humidity, ambient temperature and wind speed determine the frequency of condensation for any given location. However, it also reveals that the frequency of condensation can be modified by altering the convection heat transfer coefficient inside the collector and by using low emissivity coatings on the glazing layer.

    View record details
  • Natural convection heat loss from an open room

    Anderson, T; Gillen, JC; Norris, SE

    Conference item
    Auckland University of Technology

    Natural convection heat transfer in enclosures is an area that has particular significance to a wide range of applications. However natural convection heat transfer from enclosures with openings to the surroundings, such as open windows or doors in buildings, has received far less attention. In this regard, there is still a lack of generalised relationships that can be used in determining the heat transfer in partially open enclosures. The development of such relationships is particularly pertinent to the development of more accurate modelling tools that describe the thermal characteristics and indoor air quality in low energy buildings. As such, this work presents an investigation of the natural convection heat loss from a partly open room style enclosure, with a view to understanding the mechanism and also to developing relationships that describe it. It shows that heat transfer from the partly open enclosure is strongly influenced by both the Rayleigh number and also the opening size.

    View record details
  • Hourly electrical power consumption prediction for New Zealand residential houses using artificial neural network models

    Ahmad, A; Anderson, T

    Conference item
    Auckland University of Technology

    In this study several Artificial Neural Network (ANN) models were experimented to predict electricity consumption for a residential house in New Zealand. The effect of number of users in the house, day of the week and weather variables on electricity consumption was analyzed. Each model has been constructed using different structures, learning algorithms and transfer functions in order to come up with the best model which has better generalizing ability. Further each model has been experimented with different number of neurons in the hidden layers and different number of delays in the tapped layers, and their effect on prediction accuracy was analyzed. Subsequently the most accurate ANN model was used to study the effects of weather predictor variables on the electricity consumption. Actual input and output data were used in the training, validation and testing process. A comparison among the developed neural network models was performed to find the most suitable model. Finally the selected ANN model has been used to predict 24 hours in advance electricity consumption for a residential house in New Zealand.

    View record details
  • Modelling the performance of a Diffusion Absorption Refrigeration System

    Yousuf, N; Biteau, E; Anderson, T; Gschwendtner, M; Nates, R

    Conference item
    Auckland University of Technology

    The diffusion absorption refrigeration cycle was first identified nearly a century ago but until relatively recently its application had been limited to niche cooling applications such as camping refrigerators. The diffusion absorption refrigerator consists of several main components: a generator and bubble pump (a thermal pump), a condenser, evaporator, and an absorber. Unlike a vapour-compression cycle, the cycle operates at a single pressure level and uses three working fluids: a refrigerant, an absorbant and an auxiliary gas that is used in the system to equalize the pressure. Furthermore, where the ubiquitous vapour-compression refrigeration cycle requires work input to drive the compressor, the diffusion absorption refrigeration cycle is a thermally driven process. This characteristic has seen the cycle begin to receive the renewed attention due to the potential for it to operate using solar thermal energy to drive it. In this work the performance of an ammonia/water/hydrogen diffusion absorption refrigeration cycle is modelled for steady state operating conditions. The results show that the performance of the cycle is dependent on a number of variables including: the temperature and amount of heat added at the generator, the effectiveness of the heat recovery loops and the mass flow of the ammonia. Furthermore, it shows that the performance of the bubble pump plays a significant role in determining the performance of the system and is an area that requires further attention.

    View record details
  • Experimental evaluation of natural heat transfer in Façade Integrated Triangular Enclosures

    Piratheepan, M; Anderson, T

    Conference item
    Auckland University of Technology

    The use of building integrated solar concentrators is an area of developing interest within the field of energy-efficient building technology. One way of achieving such a device could be through the use of a flat static reflector used in conjunction with a photovoltaic/thermal absorber and glazing, thus forming a triangular enclosure similar to a single sided V-trough enclosure. Such systems may be well suited to adoption in façade applications. However, in order to precisely predict the performance of such building integrated façade collectors, it is crucial to understand the heat losses from the absorber. Unlike a flat plate collector, the glazing is not parallel to the absorber plate hence we need to develop a relationship that describes the thermal losses through the vertical glazed cover. As the air between the collector and the glass is isolated from the atmosphere, the thermal loss from the absorber to the glass cover will be due to natural convection and radiation. The radiation heat transfer can be readily determined using view factors, however there is no relationship in the literature to describe the natural convection heat transfer in triangular enclosures similar to the one illustrated. In this study, a relationship to describe the natural convection heat transfer in such triangular enclosures was experimentally determined. The relationship shows that the heat transfer, expressed in terms on the Nusselt number, is strongly dependent on the Rayleigh number and can be expressed by a relationship of the form of Nu=a〖Ra〗^b.

    View record details
  • Wind flow around a parabolic dish solar concentrator

    Uzair, M; Anderson, T; Nates, R

    Conference item
    Auckland University of Technology

    Wind flow around parabolic dish solar concentrators can significantly affect the loss of heat from the receiver, and thus the performance of these systems. Numerous studies have examined the heat loss from various receiver geometries under natural and forced convection conditions; however there is a marked absence of studies that take into account the effect that the dish may have on the heat loss, particularly for forced convection conditions. Given that forced convection can greatly increase the heat loss from such systems, there is a need for an improved understanding of the effect of the wind velocity and flow structure around parabolic dish solar concentrators. In this work, computational fluid dynamics is used to model the flow of air around a parabolic dish concentrator operating at varying angles of attack. The results show that the orientation of the dish has a significant effect on the flow structure near the receiver. For flows normal to the surface of the dish, fore or aft, the dish acts much like a bluff body, or pressure blockage, “shielding” the receiver from the flow, such that the air velocities near the receiver are relatively low. However, other operating conditions exhibit recirculation areas near the receiver that could lead to increased heat loss. Further work is required to determine the magnitude of this effect and subsequently the overall effect on the performance of parabolic dish solar concentrators.

    View record details
  • Natural convection heat transfer in façade integrated solar concentrators

    Piratheepan, M; Anderson, T

    Journal article
    Auckland University of Technology

    The use of facade (wall) integrated concentrating solar collectors is an area of developing interest within the field of energy-efficient building technology. One way of achieving such a device could be through the use of a static flat or parabolic reflector used in conjunction with a photovoltaic/thermal absorber and a vertical glazed aperture. However, to precisely predict the performance of such facade integrated collectors, it is essential to understand the heat losses from them. In general the thermal losses from these collectors can be calculated using existing relationships for flat plate solar collectors and fundamental heat transfer concepts. However there is no relationship in the literature to describe the natural convection heat transfer in the asymmetric enclosed air gap formed by a façade integrated concentrator as described. Hence, in this study, a relationship to describe the natural convection heat transfer in such enclosures was developed using an experimentally validated computational fluid dynamics analysis. The relationship shows that the heat transfer, expressed in terms on the Nusselt number, is strongly dependent on the Rayleigh number and the aspect ratio (A/H), and can be expressed in the form Nu = a Rab (A/H)c.

    View record details
  • Natural convection heat loss from a partly open cubic enclosure

    Anderson, T; Norris, SE

    Conference item
    Auckland University of Technology

    Natural convection heat transfer in enclosures is an area that has particular significance to a wide range of applications. However, heat transfer from enclosures with openings to the surroundings, such as open windows in buildings or passively ventilated electronics enclosures, have received far less attention. In this regard, there is still a lack of generalised relationships that can be used in determining the heat transfer in partially open enclosures. As such, this work presents an experimental and computational investigation of the natural convection heat loss from partly open cubical enclosures, with various opening configurations, with a view to understanding the mechanism and developing relationships that describe it. It shows that heat transfer from the partly open enclosures is most strongly influenced by the Rayleigh number and the opening size.

    View record details
  • Excel Based Tool for Global Solar Radiation Forecasting Using Artificial Neural Network Models

    Ahmad, A; Anderson, T; Lie, TT

    Conference item
    Auckland University of Technology

    Building reliable solar energy systems regardless of whether the system is a photovoltaic or thermal solar energy system requires information about global solar irradiation (sum of direct and diffuse solar radiation projected on a plane (Wh m−2)) in the region where the system is sited. This can be achieved using various solar irradiation estimation techniques particularly for locations where there are no metrological station. Various studies have shown that artificial neural network techniques predict solar irradiation more accurately than conventional methods.

    View record details
  • Optical characteristics of low concentration ratio solar collectors for façade applications

    Piratheepan, M; Anderson, T (2013-09-06)

    Conference item
    Auckland University of Technology

    This work shows that there is significant scope for the development of static solar concentrators to be integrated into the façade of buildings. It has shown that solar concentrators using parabolic reflectors may be well suited to applications in mid-latitude locations, however, the non-uniform illumination they provide means they are perhaps better suited to thermal applications. Due to the non-uniform nature of illumination provided by a parabolic reflector, flat reflectors provide an ideal compromise for building integrated photovoltaic (BIPV) and photovoltaic/thermal (BIPVT) concentrators.

    View record details
  • Pneumococcal vaccine impact on otitis media microbiology: A New Zealand cohort study before and after the introduction of PHiD-CV10 vaccine

    Best, Emma; Walls, T; Souter, M; Neeff, M; Anderson, T; Salkeld, L; Ahmad, Z; Mahadevan, M; Walker, Cameron; Murdoch, D; Mills, N (2016-07-19)

    Journal article
    The University of Auckland Library

    We compared the microbiology of middle ear fluid (MEF) in two cohorts of children having ventilation tube (VT) insertion; the first in the era of 7-valent Streptococcus pneumoniae conjugate vaccine (PCV7) and the second following introduction of the ten-valent pneumococcal vaccine (PHiD-CV10). Methods: During 2011 (Phase 1) and again in 2014 (Phase 2) MEF and NP samples from 325 children and 319 children were taken at the time of VT insertion. A matched comparison group had NP swabs collected with 137 children (Phase 1) and 154 (Phase 2). Culture was performed on all NP and MEF samples with further molecular identification of Haemophilus species, serotyping of S. pneumoniae, and polymerase chain reaction (PCR) testing on all MEF samples. Results: In Phase 2 immunisation coverage with ⩾3 doses of PHiD-CV10 was 93%. The rate and ratios of culture and molecular detection of the 3 main otopathogens was unchanged between Phase 1 and Phase 2 in both MEF and NP. Haemophilus influenzae was cultured in one quarter and detected by PCR in 53% of MEF samples in both time periods. S. pneumoniae and Moraxella catarrhalis were cultured in up to 13% and detected by PCR in 27% and 40% respectively of MEF samples. H. influenzae was the most common organism isolated from NP samples (61%) in the children undergoing VT surgery whilst M. catarrhalis (49%) was the most common in the non-otitis prone group. 19A was the most prominent S. pneumoniae serotype in both MEF and NP samples in Phase 2. Of Haemophilus isolates, 95% were confirmed to be non-typeable H. influenzae (NTHi) over both time periods. Conclusion: Following implementation of PHiD-CV10 in New Zealand, there has been no significant change in the 3 major otopathogens in NP or MEF in children with established ear disease. For these children non-typeable H. influenzae remains the dominant otopathogen detected.

    View record details
  • What is behind the ear drum? The microbiology of otitis media and the nasopharyngeal flora in children in the era of pneumococcal vaccination

    Mills, N; Best, Emma; Murdoch, D; Souter, M; Neeff, M; Anderson, T; Salkeld, L; Ahmad, Z; Mahadevan, M; Barber, C; Brown, C; Walker, Cameron; Walls, T (2015-03)

    Journal article
    The University of Auckland Library

    Aim: This study aims to describe the microbiology of middle ear fluid (MEF) in a cohort of children vaccinated with Streptococcus pneumoniae conjugate vaccine (PCV7) having ventilation tube insertion. Nasopharyngeal (NP) carriage of otopathogens in these children is compared with children without history of otitis media. Methods: Between May and November 2011, MEF and NP samples from 325 children aged <10% of MEF samples but were PCR positive for 23.1% and 38.7%, respectively. H. influenzae was the most common organism isolated from NP samples (60%) in the grommet group, while M. catarrhalis (56%) was the most common in the non-otitis prone group. S. pneumoniae was more commonly found in the nasopharynx of children with ear disease (41% vs. 29%). 19F was the most prominent S. pneumoniae serotype in NP samples of both groups, but no serotype dominated in MEF. Ninety-five per cent of H. influenzae isolates were confirmed to be non-typeable H. influenzae. Conclusion: In this cohort of children with established ear disease requiring surgical intervention, non-typeable H. influenzae is the dominant pathogen in both the nasopharynx and MEF.

    View record details
  • Impaired sensorimotor integration in focal hand dystonia patients in the absence of symptoms.

    Wu, Che-Rong; Fairhall, Scott; MCNAIR, NA; Hamm, Jeffrey; Kirk, Ian; Cunnington, R; Anderson, T; Lim-Hamm, Vanessa (2010)

    Journal article
    The University of Auckland Library

    Background Functional imaging studies of people with focal hand dystonia (FHD) have indicated abnormal activity in sensorimotor brain regions. Few studies however, have examined FHD during movements that do not provoke symptoms of the disorder. It is possible, therefore, that any differences between FHD and controls are confounded by activity due to the occurrence of symptoms. Thus, in order to characterise impairments in patients with FHD during movements that do not induce dystonic symptoms, we investigated the neural correlates of externally paced finger tapping movements. Methods Functional MRI (fMRI) was used to compare patients with FHD to controls with respect to activation in networks modulated by task complexity and hand used to perform simple and complex tapping movements. Results In the ‘complexity network,’ patients with FHD showed significantly less activity relative to controls in posterior parietal cortex, medial supplementary motor area (SMA), anterior putamen and cerebellum. In the ‘hand network,’ patients with FHD showed less activation than controls in primary motor (M1) and somatosensory (S1) cortices, SMA and cerebellum. Conjunction analysis revealed that patients with FHD demonstrated reduced activation in the majority of combined network regions (M1, S1 and cerebellum). Conclusion Dysfunction in FHD is widespread in both complexity and hand networks, and impairments are demonstrated even when performing tasks that do not evoke dystonic symptoms. These results suggest that such impairments are inherent to, rather than symptomatic of, the disorder.

    View record details