Microprocessor controlled low-temperature corn drying system
Abstract Hardware, software and control criteria of microcomputer control of low-temperature corn drying are discussed. The ambient temperature and relative humidity were monitored by the microcomputer as a measure of the input conditions. A model of the low-temperature drying process stored in the memory enabled the microcomputer to calculate the grain moisture contents at assigned locations in the bin. Control decisions were then based on predicted moisture levels and on predicted or measured grain temperatures. Simulation results showed that the proposed system can save energy from 5 to 31% compared with high-temperature drying, depending upon the weather conditions.
Minimum energy to dry barley without mould growth in near ambient driers
Dynamic programming methods are used to calculate the minimum energy required by fans and heaters to dry barley without the risk of mould growth, in grain driers using near-ambient air. Minimum values are obtained for moisture contents (dry basis) in the range 0·24–0·34, with airflows of 0·05–0·2 m/s through grain, beds 1, 3 and 5m deep. However not all possible combinations of these parameters are considered; in particular, the extreme cases of large moisture content, deep bed and low airflow are avoided. Weather records for the years 1969–1978 from Turnhouse, near Edinburgh, were used. These minimum values of energy consumption cannot be attained in practice because they require a knowledge of future weather conditions. However, for beds 3 m deep a comparison is made between the minimum values of energy consumption and the values attained with three practical methods of control. No supplementary heat was used in these practical methods of control because it is shown that they cause a large increase in energy consumption and because heaters are not generally recommended in Britain. One of these control methods minimizes average consumption over the years. Another method uses relative humidity to control the drier. It is shown that with both these control methods the energy consumption is approximately 1·05–1·18 times the minimum value. Calculations for a continuous ventilation strategy show that this uses much more energy than the other two methods of control; approximately 1·11–1·54 times the minimum value.
Application of resource allocation optimisation to provide profitable options for dairy production systems
A linear program (LP) model analysed resource use on a 100 ha dairy farm. A single optimum-profit combination was established for resources which were either optimised or constrained. It was found that, with a fixed herd of 320 milking cows, when production increased from 305 kg milksolids per cow (kg MS/cow) to 415 kg MS/cow, cash profit increased by 65%. This required additional supplements. If, however, feed demand and supply were optimised at 415 kg MS/cow, the LP reduced milking cow number rather than buy in feed to meet the increased feed demand from higher production per cow. At all production levels chosen between 305 and 415 kgMS/cow, it was most economic to dry off and cull cows early in dry summers to optimise feed demand vs. feed grown; use nitrogen (N) fertiliser to avoid a feed deficit only when response rates of better than 10 kgDM to 1 kg N could be expected; not use N for growing supplements to harvest. Pasture cover, within defined constraint levels, provided a buffer for feed demand and supply fluctuations. The study highlights the importance of assessing production, income and cost in an integrated framework to identify the point at which individual resources become limiting.