Programmable Thermostat Droop Control for Comfort-Economy Heating
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Solution Overview
Problem
HVAC systems face challenges in balancing comfort and economy, particularly when using auxiliary heat sources, which are more expensive, and existing control methods fail to efficiently manage the trade-off between these factors.
Innovation Solution
A programmable thermostat with a user interface and memory that allows for the adjustment of droop values, enabling the controller to activate auxiliary stages only when the temperature deviation from the setpoint exceeds a certain threshold, depending on the operating condition, thereby optimizing the use of primary and auxiliary heat sources based on user preferences for comfort versus economy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If auxiliary heat is used to maintain setpoint temperature, then temperature control precision is improved, but energy cost increases
Solution Approach 1:
The system applies partial action by using auxiliary heat not continuously, but only when the temperature deviation exceeds the droop threshold. This partial application of auxiliary heating achieves acceptable temperature control while avoiding excessive energy consumption during minor fluctuations.
Solution Approach 2:
The system changes the control parameter by introducing a droop value that modifies the traditional setpoint temperature. Instead of maintaining exactly the setpoint temperature, the system allows temperature to vary within a droop range, changing the control parameter from fixed setpoint to variable setpoint with hysteresis.
2Stability of the object's composition
If auxiliary heat is activated early to prevent temperature drop, then temperature stability is improved, but energy consumption increases
Solution Approach 1:
The system prepares for potential temperature drops by monitoring the droop condition, but only takes preliminary action (activating auxiliary heat) when the threshold is actually exceeded. This avoids premature activation while still being ready to respond when needed.
Solution Approach 2:
The system uses feedback by continuously monitoring the temperature deviation from setpoint and comparing it against the droop threshold. The auxiliary heat activation is based on real-time feedback of the temperature condition, ensuring activation only when necessary for stability.
3Use of energy by moving object
If droop value is increased to avoid auxiliary heat use, then energy cost is reduced, but temperature control precision deteriorates
Solution Approach 1:
The system makes the droop value dynamic rather than fixed, allowing it to be adjusted based on operational conditions, user preferences (comfort vs. economy mode), and system state. This dynamic adjustment enables optimization of both energy cost and temperature control precision for different scenarios.
Data Source
AI summary
A programmable thermostat may be configured to control one or more pieces of HVAC equipment in accordance with a programmable schedule. The HVAC equipment may be capable of modifying a temperature of an inside space with at least a primary stage and an auxiliary stage. The programmable thermostat may include a memory for storing operating parameters of the programmable thermostat, a user interface configured to accept modification of operating parameters, including one or more droop values, and a controller coupled to the memory and the user interface. The controller attempts to control the temperature of the inside space with the primary stage of the HVAC equipment, but if the temperature of the inside space deviates from a desired setpoint temperature value by more than or equal to a programmed droop value, the controller may activate the auxiliary stage. In some instances, the user interface of the programmable thermostat may be configured to allow a user to selectively override one or more of the applicable droop values. In some instances, the droop value that is used may depend on the current operation condition of the controller.