Unsupervised image segmentation with neural networks

The segmentation of colour images (RGB), distinguishing clusters of image points, representing for example background, leaves and flowers, is performed in a multi-dimensional environment. Considering a two dimensional environment, clusters can be divided by lines. In a three dimensional environment by planes and in an n-dimensional environment by n-1 dimensional structures. Starting with a complete data set the first neural network, represents an n-1 dimensional structure to divide the data set into two subsets. Each subset is once more divided by an additional neural network: recursive partitioning. This results in a tree structure with a neural network in each branching point. Partitioning stops as soon as a partitioning criterium cannot be fulfilled. After the unsupervised training the neural system can be used for the segmentation of images

Warmte-overdrachtsprestaties van de OPAC106 warmtewisselaar

Zowel vanuit het oogpunt van een betere beheersbaarheid van het kasklimaat, als vanuit de toenemende behoefte aan laag temperatuur verwarmingssystemen zijn er de afgelopen jaren belangrijke ontwikkelingen in warmtewisselaars voor de tuinbouw in gang gezet. Er zijn systemen die boven in de kas worden geplaatst en systemen die onderin zijn gesitueerd. Er zijn installaties met en luchtverdelingsslurven, maar ook systemen met een vrije uitblaas. Door de veelheid aan toepassingsgebieden zijn warmtewisselaars moeilijk onderling vergelijkbaar. In dit rapport zijn de warmte overdrachtprestaties van een nieuw type compacte warmtewisselaar bestudeerd, de OPAC106 warmtewisselaar met dwarsstroom ventilator

A spectral selective lamellae concentrator system as BI-CPV/T System

In warm periods the excess of incoming solar energy into a greenhouse is more than required for the growth of the crop. In particular the near infrared radiation (NIR) part of the incoming radiation is not necessarily. In a previous research project a new type of greenhouse with an integrated concentrated photovoltaic system with thermal energy output (CPVT-system) was developed. This earlier system was based on a circular covering geometry and an integrated filter for reflecting the NIR of the greenhouse. The reflected radiation was used in a solar energy system. In this feasibility study the new CPVT-system is simplified so more economically by avoiding the asymmetric greenhouse construction with bended glass and the large construction for solar tracking. All parts of the solar concentrating system will be mounted inside a standard Venlo type greenhouse. The concentrator consists of lamellae which only focus the NIR-part of the spectrum onto the CPVT–module. This module is mounted to or integrated into the ridge or gutter of the greenhouse. With this spectral selection the heat load inside the greenhouse will be reduced. The target is a maximal total annual electricity production. The optimization is done with a ray tracing model fed with actual radiation data. Two types of lamellae are compared: flat lamellae and trough shaped lamellae which focus the radiation individually. Trough shaped lamellae have the advantage of reducing the number of lamellae in combination with a high concentration ratio. This will lower the costs for the servo drive of the lamellae. The reflected NIR radiation can be focused with a geometric concentration factor of 100x. The lamellae will not only reflect 49% of the NIR radiation but also a part of the whole solar spectrum. The total effective concentration ration factor will be 23x, including the transmission losses of the greenhouse and the efficiency of the concentrator. The high geometric concentration factor will limit the shadowing effect of the cultivation area by the PV-cells with only 1%. Further optimalisation in the energy yield were performed on determination of the optimal focal length of the trough shaped lamellae. The highest annual electrical output was found for lamellae with individual optimized focal lengths. In that case the annual output for Dutch climate conditions can be over 29 kWh/m

Feedback control of water supply in an NFT growing system

The paper explores a concept of irrigation control, where the supply of nutrient solution is controlled without the use of predictive uptake models but rather by the use of a direct feedback of a drain flow measurement. This concept proves to be a viable approach. Results are presented, showing the compensation of changes in water up-take due to variations in global radiation, with a very tight control of the drain flow, keeping it constant over long periods of time. A tipping-bucket type flow sensor and its use in controlled water supply to a to-mato crop is described. A calibration procedure for the tipping-bucket instrument is presented

PV-cellen op de ZonWindkas

De ZonWindKas bestaat uit een systeem van lamellen in de zuidkant van het kasdek die in de zon gedraaid kunnen worden op het moment dat de zon boven een bepaalde stralingsintensiteit schijnt. Deze lamellen dienden oorspronkelijk voor de productie van warm water, dat na opslag in een zeer goed geïsoleerde buffer kan worden gebruikt voor de verwarming in de winter. Deze lamellen zouden kunnen worden voorzien van PV-cellen voor de productie van elektriciteit. In dit onderzoeksproject is via metingen en een model berekend wat de potentie is van PV-cellen op de lamellen

A Fresnel lenses based concentrated PV system in a greenhouse

The scope of this investigation is the development and testing of a new type of greenhouse with an integrated linear Fresnel lens, receiver module and an innovative system for tracking to exploit all direct radiation in a solar energy system. The basic idea of this horticultural application is to develop a greenhouse for pot plants (typical shadow plants) that do not like direct radiation. Removing all direct radiation will drastically reduce the need for cooling under summer conditions and the need for screens or lime coating of the glass to reflect or block a large part of the radiation. The removal of all direct radiation will block up to 81% of the solar energy, which will reduce the needed cooling capacity. The second measure is the integration of a solar energy system. When the (linear) Fresnel lenses are designed between double glass coverings and integrated in the greenhouse, the focused solar energy on the Thermal Photovoltaic (TPV) cell in the focus point delivers electric and thermal energy. The TPV module mounted in the focal point requires cooling due to the high heat load of the concentrated radiation (concentration factor of 50×). All parts are integrated in a greenhouse structure with a size of about 36 m2 and the electrical and thermal yield is determined for Dutch climate circumstances

A concentrator system for BI-CPVT with static linear Fresnel lenses

A greenhouse with Fresnel lenses in the south facing roof and a receiver for concentrated Photovoltaic with water cooling (CPVT system) will result in electrical and thermal energy output from the solar energy excess entering a greenhouse. The PV system converts about half of the direct radiation into heat and electricity. During periods with direct radiation this will significantly reduce the heat load on the greenhouse For an optimal performance the roof elements must be asymmetric with a steep inclination at the north side (the exact angle of course depends on the latitude of the building site). The Fresnel lens structure is best oriented in upwards direction. In the current design, two lenses are placed in the inner space of a double glass. This prevents pollution and condensation on the lenses. By the upward facing of the lens structure, the focus quality is preserved over a much broader range of angles of incidence compared to a lens with downward facing structures. Each PMMA lens with a size of 1.20m x 1.52m is composed of 12 ‘tiles’ for easy production. The focal distance of the lens is 1,875m and the geometrical concentration factor is 50×. This means that in most cases the focus line is thinner than 3 cm. The performance of the lens with respect to the shape of the focal area and the position of the focal line has been analyzed with ray tracing techniques. From this analyses and by the development of a smart tracking system only two motors can bring the receivers in the required positions. One motor controls the distance between lens and receiver and the other controls the translocation of the receivers parallel to the lens. The second conclusion was that the positions of the focal line are within the bounds of the greenhouse construction for almost the whole year. Only in winter, in the early morning and at the end of the day, the focal line will be unreachable. The light sum is very stable in the greenhouse compared with the light sum outside. The 480 m2 greenhouse, with the LCPVT system based on Static Fresnel lenses and a 12 m CPVT-module and a 200 m CT-module, is designed by Bode Project Engineering and constructed by Technokas in Bleiswijk the Netherlands. An electrical power of 37W/(m2 greenhouse) is measured at an incoming global radiation of 870 W/m² (on a horizontal plane). The fraction collected thermal yield is about 20% of the total incident direct radiation

Cropscout II, a modular mini field robot for precision agriculture

In this paper a small agricultural robot named Cropscout II is described. Besides the objective to participate in the annual Field Robot Event competition Cropscout II operates as a modular test bed for autonomous robot control using sensor fusion techniques and artificial intelligence. The main challenge in this aspect is to cope with the poorly structured environment and the variation in shape, size and color of biological objects encountered in the open field. The very flexible and modular design of the system in both the electrical and mechanical way proofed to have many advantages. Unless some of the tasks to complete were solved very well the final conclusion is that it is still a big challenge to build a robot for the wide variety of different and unpredictable outdoor conditions. Future research on all aspects is essentia

A Prototype Sensor for Estimating Light Interception by Plants in a Greenhouse

Light interception is one of the most important factors for plant growth. The intercepted amount depends on the incoming radiation in the greenhouse and the percentage of interception by the crop and is directly related to the leaf area. Proper crop management requires the measurement of the most important growing factors. In case of application of crop growing models the simulation of the leaf area is one of the major uncertainties in the results of the models. Automatic calibration of the model based on radiation interception increases the accuracy of the model results. For the determination of the crop¿s light interception in a greenhouse, a radiation sensor was used which determines the ratio of the incoming radiation from the upper side and the reflection at a specific wavelength from the lower side. The ratio of reflected radiation versus intercepted radiation can be used to estimate light interception as well as leaf area. However, the measurement of this fraction can only be used after filtering out erroneous data due to technical errors, insufficient diffuseness, insufficient solar height, etc. This paper describes the boundary conditions to be taken into account for proper measurement of reflected radiation. Time series measurements of incoming, reflected and global radiation are used, to filter the data acquired by the sensor. The sensor functioned well during tests on a cucumber crop in a commercial greenhouse