A Brief Description of the SGH
The SGH is located on the Southern Oregon Coast, at Latitude 42.4 degrees, Longitude –124.4 degrees (approximately). The Structure is oriented with the plane of the South wall normal to the azimuth of the solar zenith.
The SGH has glazing on the South-facing wall only. The glazing material is single-pane 1/8 in. tempered window glass. The glazing is installed at an angle of 60 degrees from the horizontal. The remaining 3 walls are opaque and heavily insulated, as is the floor and the roof. The SGH floor surface is of masonry construction, ¾ in. thick.
A single row of fifty-five gallon flat black-painted plastic drums is located on the floor, closely-spaced, along the entire length of the North Wall. These drums are connected together as a single reservoir, to hold a water-based nutrient solution for hydroponic plant culture. The solution also acts as a heat storage medium, to moderate diurnal temperature variation.
Plants are grown in containers located on benches placed along the South wall. The planting medium is pea gravel (1/8 to 3/8 in. dia. “River Run”). The base of each container is plumbed to a solution distribution system. A timer-controlled pump (located in the reservoir) runs until the containers are nearly full. When the pump shuts off, the nutrient solution gravity-flows through the pump back into the reservoir. The containers thus fill from the bottom up, displacing air. The draining of the containers pulls air (and thus oxygen) into the root areas. This process is repeated a number of times during daylight hours.
Supplemental heating is provided by electric heaters. The ventilation system consists of a motor-driven set of air intake louvers on one end of the SGH and a motor-driven exhaust fan on the opposite end. The exhaust fan is never operated without the air intake being “open”. The air intake is only opened when running the exhaust fan. Separate small fans are operated to circulate inside air when the ventilation system is not running.
The SGH is instrumented with sensors to measure interior and exterior temperature and relative humidity (RH). There are also sensors to measure nutrient solution temperature. These sensors are connected to a network that is controlled by a dedicated computer. The computer has two functions: (1) Logging the measured data and (2) controlling the SGH Heating and Ventilation System.
There is a digital Input/Output (I/O) board located in the SGH and connected to the network. The I/O board is used to input heater and ventilation system status to the computer and to output commands to the heating and ventilation systems.
The SGH has two heating and ventilation control systems. One control system consists simply of a conventional electromechanical thermostat for the electric heaters and a separate thermostat for the ventilation system. This system operates independent of the computer, although the computer logs measurements when either control system is running.
The second control system is implemented using the computer and the networked sensors. The computer is located in a building separate from the SGH.
The computer is a conventional PC, running WINDOWS xp. All SGH sensors and the I/O board are purchased “1-wire” network devices. Data is transferred from the sensors and the I/O board to an EXCEL spreadsheet, using the DDE (Dynamic Data Exchange) function in WINDOWS. Two software packages are used to accomplish this: DDEView, a commercially-available program and a VBA (Visual Basic for Applications) program written by L. Vincent Nash.
The SGH has glazing on the South-facing wall only. The glazing material is single-pane 1/8 in. tempered window glass. The glazing is installed at an angle of 60 degrees from the horizontal. The remaining 3 walls are opaque and heavily insulated, as is the floor and the roof. The SGH floor surface is of masonry construction, ¾ in. thick.
A single row of fifty-five gallon flat black-painted plastic drums is located on the floor, closely-spaced, along the entire length of the North Wall. These drums are connected together as a single reservoir, to hold a water-based nutrient solution for hydroponic plant culture. The solution also acts as a heat storage medium, to moderate diurnal temperature variation.
Plants are grown in containers located on benches placed along the South wall. The planting medium is pea gravel (1/8 to 3/8 in. dia. “River Run”). The base of each container is plumbed to a solution distribution system. A timer-controlled pump (located in the reservoir) runs until the containers are nearly full. When the pump shuts off, the nutrient solution gravity-flows through the pump back into the reservoir. The containers thus fill from the bottom up, displacing air. The draining of the containers pulls air (and thus oxygen) into the root areas. This process is repeated a number of times during daylight hours.
Supplemental heating is provided by electric heaters. The ventilation system consists of a motor-driven set of air intake louvers on one end of the SGH and a motor-driven exhaust fan on the opposite end. The exhaust fan is never operated without the air intake being “open”. The air intake is only opened when running the exhaust fan. Separate small fans are operated to circulate inside air when the ventilation system is not running.
The SGH is instrumented with sensors to measure interior and exterior temperature and relative humidity (RH). There are also sensors to measure nutrient solution temperature. These sensors are connected to a network that is controlled by a dedicated computer. The computer has two functions: (1) Logging the measured data and (2) controlling the SGH Heating and Ventilation System.
There is a digital Input/Output (I/O) board located in the SGH and connected to the network. The I/O board is used to input heater and ventilation system status to the computer and to output commands to the heating and ventilation systems.
The SGH has two heating and ventilation control systems. One control system consists simply of a conventional electromechanical thermostat for the electric heaters and a separate thermostat for the ventilation system. This system operates independent of the computer, although the computer logs measurements when either control system is running.
The second control system is implemented using the computer and the networked sensors. The computer is located in a building separate from the SGH.
The computer is a conventional PC, running WINDOWS xp. All SGH sensors and the I/O board are purchased “1-wire” network devices. Data is transferred from the sensors and the I/O board to an EXCEL spreadsheet, using the DDE (Dynamic Data Exchange) function in WINDOWS. Two software packages are used to accomplish this: DDEView, a commercially-available program and a VBA (Visual Basic for Applications) program written by L. Vincent Nash.
posted by Larry Nash at 3:19 PM
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