ISHS Acta Horticulturae 174: Symposium Greenhouse Climate and its Control
COMPONENT HARDWARE AND SOLAR HEATING SOFTWARE FOR A SECOND GENERATION GREENHOUSE COMPUTER |
| Authors: | G.J. Monk, J.M. Molnar, E.M. van Zinderen Bakker, A. MacKenzie |
| Abstract:
Agriculture Canada tested a fully programmable Argus Control Systems Ltd. computer during 1983–84 in a glass greenhouse range that includes two unique solar heated environments and four conventional environments (van Zinderen Bakker et al, 1983). The greenhouses are located in southwestern Canada where a mild climate is dominant. The solar shed greenhouse is an east-west aligned structure with an insulated north wall. A 3.7 kW electric fan circulates hot air that has risen from internal polyethylene collectors in two directions through rock storages beneath the floor. The earth thermal storage (E.T.S.) greenhouse is a standard gable-type structure aligned east-west. It is heated by circulating interior air in two directions through a network of thirty-four 10 cm diameter pipes buried longitudinally beneath the greenhouse floor. The hardware configuration will be decentralized to reduce installation costs and increase the flexibility of its applications. The mainframe has communicated serially with field modules (FMs) which distributed all input/output. The FMs are now being made intelligent with the capability to function as independent controllers. If advanced display, control and data-logging functions are required, a central operator's station will be interfaced with the controllers. The initial control algorithms used interior and storage air temperatures to operate the solar systems for first stage venting and heating. Electricity was wasted when the excess solar energy was insufficient to charge the storages for subsequent heat withdrawal and when the storages were kept fully charged even through nighttime heat loads didn't require the full capacity. New software will estimate heat loads based on the previous night's exterior temperatures. Storage temperatures will be used to balance | |
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