Tintable Window Predictive Control Using Sunlight Penetration Depth
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Solution Overview
Problem
Electrochromic windows suffer from various issues that have limited their commercial potential, including inefficiencies in controlling tint levels for occupant comfort and energy conservation.
Innovation Solution
The implementation of predictive control logic in window controllers to dynamically adjust the tint levels of electrochromic windows based on occupant comfort, energy considerations, and actual irradiance levels, using modules that account for penetration depth of sunlight, predicted irradiance, and real-time sensor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If electrochromic windows are used to control tint levels, then energy savings and glare reduction are achieved, but occupant comfort and natural lighting requirements create control complexity
Solution Approach 1:
The control system performs preliminary calculations of penetration depth and predicts future irradiance levels before they occur. By computing the tint level needed for future conditions and accounting for window transition time, the system proactively adjusts tint levels to maintain occupant comfort and energy efficiency without complex real-time adjustments
Solution Approach 2:
The system uses sensor data and environmental parameters to automatically determine optimal tint levels without manual intervention. The control logic independently evaluates penetration depth, predicted irradiance, and window transition characteristics to self-regulate the electrochromic windows, reducing the need for complex external control mechanisms
2Object-affected harmful factors
If tint levels are adjusted to reduce direct glare and radiant energy, then occupant comfort is enhanced, but natural lighting into the area may be reduced
Solution Approach 1:
The system applies partial tinting rather than complete darkening by calculating the specific penetration depth and determining the minimum necessary tint level to achieve comfort. This partial action approach reduces glare and radiant energy while preserving sufficient natural lighting, avoiding the excessive action of complete tinting that would eliminate natural light
3Reliability
If predictive control logic is implemented to account for window transition time, then future tint levels are accurately controlled, but control system complexity increases
Solution Approach 1:
The control system calculates the future tint level needed based on predicted irradiance and determines the appropriate transition time required for the electrochromic window to reach that state. By initiating the tinting process in advance of when the desired tint level is needed, the system ensures accurate future control without requiring complex real-time adjustment mechanisms
Solution Approach 2:
The system uses sensor data to monitor actual irradiance levels and compares them with predicted values, using this feedback to refine future predictions and adjustments. This feedback mechanism improves control accuracy by learning from actual performance while maintaining a relatively simple control structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables electrochromic windows to effectively reduce direct glare and total radiant energy while allowing sufficient natural lighting, thereby enhancing occupant comfort and achieving energy savings that meet or exceed those of reference windows.
Implementation Method 1
Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in an optical property when placed in a different electronic state, typically by being subjected to a voltage change.
Implementation Method 2
Tungsten oxide is a cathodic electrochromic material in which a coloration transition, transparent to blue, occurs by electrochemical reduction.
Data Source
AI summary
A method of controlling tint of a tintable window to account for occupant comfort in a room of a building. The tintable window is between the interior and exterior of the building. The method predicts a tint level for the tintable window at a future time based on a penetration depth of direct sunlight through the tintable window into the room at the future time and space type in the room. The method also provides instructions over a network to transition tint of the tintable window to the tint level.