Tintable Window Control Using Sunlight Penetration Prediction
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Solution Overview
Problem
Electrochromic windows, despite advances in technology, have not fully realized their commercial potential due to various issues, including inefficient control methods that fail to effectively manage tint levels for occupant comfort and energy conservation.
Innovation Solution
The implementation of predictive control logic in building management systems that adjusts tint levels of electrochromic windows based on occupant comfort, energy considerations, and actual irradiance, using sensors to determine the optimal tint levels for different times and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If electrochromic windows are used to control light transmission, then energy savings can be achieved, but occupant comfort may be compromised due to direct glare and insufficient natural lighting
Solution Approach 1:
The system performs predictive control by calculating future solar positions and penetration depths in advance, determining optimal tint levels before glare becomes an issue. The controller proactively adjusts window tinting based on predicted solar trajectories rather than reacting to current glare conditions.
Solution Approach 2:
The system dynamically changes the optical parameters of the electrochromic windows by adjusting tint levels continuously. By varying the tint level parameter in response to calculated penetration depths and solar positions, the system optimizes both energy savings and occupant comfort throughout the day.
2Object-affected harmful factors
If the window tint is darkened to reduce glare, then direct sunlight penetration is reduced, but natural lighting into the room is also reduced
Solution Approach 1:
The system applies different tint levels to different windows or portions of windows based on local conditions. By calculating penetration depth for each window's specific orientation and position, the system tailors the tint level locally to balance glare reduction with natural lighting requirements for each space.
Solution Approach 2:
The window tinting system dynamically adjusts its optical properties in real-time based on changing solar positions and room conditions. The tint level is not static but continuously adapts to maintain optimal balance between glare reduction and natural lighting throughout the day and across different seasons.
3Productivity
If predictive control logic is implemented to account for transition time, then future tint levels can be optimized, but system complexity increases
Solution Approach 1:
The system calculates and determines optimal tint levels in advance based on predicted future solar positions and transition time requirements. By performing these calculations proactively rather than reactively, the system achieves optimized control without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
The predictive control system autonomously performs calculations of solar positions, penetration depths, and optimal tint levels without requiring external intervention or complex user input. The system self-regulates the window tinting based on environmental data and pre-programmed algorithms, simplifying the user interface despite the sophisticated control logic.
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 approach allows for improved occupant comfort by reducing direct glare and allowing sufficient natural lighting while achieving energy savings that meet or exceed those of reference windows, thereby enhancing the energy efficiency of buildings.
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.
Data Source
Figure 1A~1B
Figure 1C
Figure 2A
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.