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Oklahoma State University Geothermal Smart Bridge. Quarterly Progress Report. Quarter ending 11/31/01 Task 4.3.1.3 - Integrated Control Strategies Stone/Spitler/Elliott. Accomplishments. Alternative controller (SC2) developed for the model bridge Bridge deck wetness sensor developed
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Oklahoma State University Geothermal Smart Bridge Quarterly Progress Report Quarter ending 11/31/01 Task 4.3.1.3 - Integrated Control Strategies Stone/Spitler/Elliott
Accomplishments • Alternative controller (SC2) developed for the model bridge • Bridge deck wetness sensor developed • Preliminary communications infra-structure plan for Smart Bridge control systems developed
Issues driving development of alternative controller • The model bridge heating system uses a single heat-pump and is configured for an ON/OFF controller. • The minimum OFF time after the model bridge heat-pump has been engaged is 5 to 20 minutes. This severely limits modulation of heat into the bridge by controlling length of ON cycles. • The existing simulated MPC controller optimizes heating time by manipulating loop temperature into the deck and is not easily modified to control the model bridge. • Typical warm-up time to 0 0C for the bridge deck is 6-12 hours which is approximately best forecast lead time. • The existing MPC controller does not handle the situation where there is no precipitation, the deck is wet, and the deck surface cools below freezing. • A controller that implements ON/OFF action with dead-band has been implemented successfully (Smith et. al.) on the model bridge.
SC2 Concept • Based on icing prevention through: • Bridge deck wetness prediction • Bridge deck wetness sensing • Bridge deck temperature control. • Uses NWS RUC product • Detect threat of a wet bridge surface • Precipitation • Dew events • Up to 12 hours lead-time. • Existing ON/OFF controller for temperature control. • “leaf wetness” type sensors for deck wetness sensing.
SC2 Algorithm • The ON/OFF controller is engaged during the threat of a wet bridge deck surface. • Once the threat of a wet bridge deck surface has passed, the ON/OFF controller is allowed to disengage. • The ON/OFF controller does not disengage until the bridge deck surface is dry. • If the bridge deck surface is wet and the deck temperature falls near freezing, the ON/OFF controller is engaged.
Plans for Next Quarter: • SC2 will be implemented on the model bridge and monitored during the following quarter. • Bridge deck wetness sensor will be tested and performance validated. • A strategy will be identified for implementing adaptivity for the Smart Bridge controller.