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    Light transmission, heat retention and mechanical strength property evaluation of film plastic cladding materials available in New Zealand : a thesis submitted in partial fulfilment of the requirement for the degree of Master of Horticultural Science in horticultural engineering at Massey University
    (Massey University, 1990) Heatley, Philip Reeve
    This study was conducted on film plastic cladding materials commercially available from distributors in New Zealand. Laboratory scale experiments were applied to test and evaluate the optical, thermal and mechanical properties of each of the film plastics. Optical properties tested included PAR transmissivity and the degree of UV radiation transmission through the film plastics. The radiant heat retention property of each product was evaluated through thermal transmission tests. Mechanical property evaluation required application of tear resistance, tensile strength, impact resistance and water vapour permeance tests. It was recognised that an evaluation and comparison of each of the film plastics as a full functional cladding material would be useful to both greenhouse designers and growers. Consequently, each of the products were ranked according to specific optical, thermal or mechanical properties. Upon combining these rankings, recommendations on the best film plastic cladding material, for specific applications, were supported and presented in tabular form. Experimental data and analysis consistently indicated that a PVC film plastic, a double layer co-extruded film plastic, woven PE and reinforced EVA film materials and a specific EVA type film plastic, available in New Zealand at the time of this research, will perform particularly well as greenhouse cladding materials. Purchasing evaluation, of any of the film plastics tested in this study, should further involve the cost and the susceptibility of each product to UV degradation as selection criteria.
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    An evaluation of the economic benefits of active cooling and carbon dioxide enrichment of greenhouse cucumbers (Cucumis sativus L.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science at Massey University
    (Massey University, 1996) Van Heijst, Marcus Johannes Aart Everardus
    Cooling a greenhouse with a refrigeration system rather than conventional ventilation makes it possible to maximise the fractional enrichment time for carbon dioxide, and more importantly enrich during periods of high photosynthetically active radiation. Using conventional climate control methods, enrichment is limited to periods when the greenhouse is not being ventilated, thus reducing the potential enrichment time of the crop. The objective of this study was to develop a simulation model of a greenhouse crop growing with a closed cycle climate control system, using a heat pump, with a reversible (dual) cycle, for heating and cooling. A computer implemented mathematical model developed by Wells (1992) was modified to simulate cucumber crop growth in a greenhouse of commercial size and allowing certain parameters to be set. These parameters included: two types of control system, four levels of enrichment, three crop periods, and at two locations, Auckland and Christchurch. The three crop periods chosen were 26 Jan to 26 April, 25 May to 23 August, and 20 September to 19 December. The two types of control involved conventional fan ventialtion and electric heating, and closed cycle climate control using a reverse cycle heat pump. Greenhouse carbon dioxide enrichment levels used were 350, 600, 900, 1200 μ1.1-1 . The two locations chosen were Auckland and Christchurch. An economic analysis of the results was carried out calculating Annual Marginal Return (AMR) and Internal Rate of Return (IRR) for treatments compared to control. It was concluded that carbon dioxide enrichment combined with conventional control is a worthwhile investment in Christchurch but less so in Auckland. Due to the high capital cost, carbon dioxide enrichment combined with closed cycle climate control is a less attractive investment. However, as considerable energy savings are possible with closed cycle climate control, it is worthwhile investigating other less expensive forms of closed cycle climate control. The economic feasibility of the application of this technology to other, higher value, crops is worthwhile investigating.
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    Evaluating the economic feasibility of thermal screens in New Zealand using a mathematical model : a thesis presented in partial fulfilment of requirements for the degree of Master of Horticultural Science in Horticultural Engineering at Massey University
    (Massey University, 1991) Newman, Todd Litchfield
    A mathematical model of the greenhouse environment was developed to ascertain the annual savings in heating expenditure achieved by thermal screens. Thirteen materials with thermal screening potential were investigated. Each material was modelled within glass, Agphane, and twin skin Agphane covered greenhouses, 300m2 and 1000m2 in floor area, heated with diesel, coal, electricity, natural gas, or L.P.G., to set points of 15°C and 20°C, in Auckland and Christchurch. The model consisted of two phases. Phase 1 was a steady state model of the greenhouse environment based on a series of energy and mass balances. The temperatures within the greenhouse and the quantity of heat required to hold the house at a specified set point were predicted by solving these balances simultaneously. This process enabled the average U-value for each greenhouse to be estimated. In Phase 2 of the model the annual heat load for combinations of each house size and type, cover, screen, set point, and location were estimated using average U-values from Phase 1 and meterological data indicative of Auckland and Christchurch. Using current fuel prices, annual heat loads were converted into annual heating expenditures. Using annual heating expenditure, screen life expectancy, and screen installation cost an economic analysis was conducted using internal rate of return as a measure of thermal screen feasibility. In terms of savings in heating expenditure, Black Polythene, Infrane, and Clear Polythene recorded the highest internal rate of return. It was decided that before a formal recommendation could be made further research was required to evaluate screens as summer shading or photoperiod control devices and to consider the practical problems associated with some of the screens. It was shown that returns from thermal screening were greater in Christchurch than Auckland, greater at a 20°C set point than at a 15°C set point, greater for a 1000m2 house than a 300m2 house, greatest with diesel heating in Auckland, and greatest with diesel and L.P.G. heating in Christchurch.
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    Modelling and performance study of large scale Zigbee based green house monitoring and control network : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Electronics and Communication Engineering at Massey University, Albany, New Zealand
    (Massey University, 2013) Hoque, Iftekharul
    Zigbee wireless sensor networks, known as IEEE 802.15.4 standard, have become quite popular in recent years due to its low power consumption, long battery life and security management. Academic and networking industries have taken interest in Zigbee (IEEE 802.15.4) due to its capability for multiple applications. In this thesis, we have studied Zigbee wireless sensor networks in geographically distributed greenhouses, which are a vital component in agriculture industry today. However due to the complexity and scattered nature of the proposed large scaled network, we only simulate the scenarios in an industry standard and powerful simulator called OPNET to achieve the perfect design and high percentage success. We investigate the performance parameters such as throughput, end-to-end delay, packet loss, traffic sent and traffic received depending on the network topology under various layouts and node conditions based on specific features and recommendations of the IEEE 802.15.4/ZigBee standards. Since the network delay is the most important characteristic, we investigate this parameter first. We find that the delay increases as the number of greenhouses increases e.g. the delay for 20- greenhouse (GH) scenario is higher than 50- GH scenario. This is contrary to generally perceived understanding however our initial delay was also greater for 50- GH scenario but later due to many un-joined nodes, the delay fell suddenly. The next parameter we investigate is MAC throughput which is seen as increasing when there is communication between maximum nodes. The 20- GHs scenario is shows maximum MAC throughput whereas the scenario with 50- GHs stays way below 20- GHs. We also observe that the number of packets drops significantly in case of 50- GHs. This is attributed to the possibly of the routers dropping the joining or relay requests from end devices while they are too busy in processing requests from other end devices. We can conclude from the above that if the setup is as big as 50 GHs, we can’t rely on single coordinator setup as it is too far for the nodes to hop all the way. On the other hand, the traffic sent in scenario with 20- GH reaches the IEEE 802.15.4 industry specification of 250 kbps showing that the data is being sent at maximum possible rates in this scenario. So, real life implementation of this setup is possible for small number of GHs like 20- GHs. The scenario with 20- GHs and nodes spaced at 20 m has shown favorable results for all the parameters such as throughput, delay and traffic even for a single coordinator. Though our simulations worked and have been able to get reasonable results there are many challenges that need be met to improve the outcome of this as well as any other study involving simulation of the geographically dispersed very large scale Zigbee-based wireless sensor networks. Another challenge in this design is that the simulation of 50- GH with nodes close to 1000 takes large amount of time execute. Nonetheless, based on the findings from this work, it will be helpful to design the GH/nodes layout of the implementation in OPNET. The most important achievement of the work is that we have been able to develop a simulation model for the geographically dispersed very large scale Zigbee-based wireless sensor network representing networked greenhouses. Considering the results of throughput, end-to-end delay, packet loss, traffic sent and traffic received it looks the network can support optimally a 20- GH setup for remote monitoring and control application.