|
The system was originally built because it was economical. With the federal tax credits available at the time and with the high cost of a natural gas
pipeline extension to compare it to, Ove said that solar was the most economical space heating option available. He credits it with keeping the electric utility bill down to ~US$200 (1998) dollars a month (~1500 kWh/mo)
for a 4800 square foot house. The house includes two all-electric kitchens, since the downstairs portion of the house has been rented separately.The control computer was based on an 8085-microprocessor development
board, designed for use as a training and prototyping tool for electronic engineers. Temperature measurement was supported using integrated-circuit temperature sensors (AD590) and a temperature measurement module
(AD2038) built by Analog Devices, Incorporated. Custom interfacing circuits built by Mike Kliment using the wire-wrap wiring technique allowed the development board to communicate with the
temperature measurement module, monitor the positions of the dampers, and command the dampers to change positions. The control computer failures that occurred were generally attributed to voltage surges from the various
pumps and motors feeding back through the power supplies and disrupting the control computer circuitry. Near the end of its period of operation, some of the less critical operations of the control computer stopped
functioning due to what appeared to be deterioration of electronic components. The thermostats failed in two ways: the thermostat units themselves failed, and their external relays burned out. Jade Controls
manufactured these thermostats, which were among the first programmable setback thermostats available. In 1998, Ove Floystrup contracted Endecon Engineering to replace the control computer with more modern,
off-the-shelf components, to re-write the control software for the new computer, and to document the resulting system. This document summarizes the approach and results of this work. |
