Electric Water Heater Control Using Two-Mass Reserve Capacity
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Solution Overview
Problem
Electric water heaters (EWHs) pose challenges in demand response due to uncertain operation, potential customer discomfort during grid service events, lack of available measurements for reserve capacity, and limited controllability, which hinder their participation in adjusting household power demand effectively.
Innovation Solution
Implementing a two-mass model-based control system that determines a reserve capacity and safe deferred time for an EWH, allowing it to delay heating based on historical power usage and stochastic predictions, ensuring customer comfort while contributing to grid service events by managing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If EWH operation is made controllable for demand response, then power demand adjustment capability is improved, but system complexity increases due to need for reserve capacity determination and safe deferred time calculation
Solution Approach 1:
The system performs preliminary determination of reserve capacity and safe deferred time before grid service events occur. By pre-calculating these parameters based on historical power usage and stochastic predictions, the system prepares the EWH for future demand response actions without requiring complex real-time decision-making during actual grid events.
Solution Approach 2:
The patent introduces an intermediary control layer that sits between the EWH and the utility company. This intermediary determines reserve capacity and safe deferred time, translating complex demand response requirements into simple on/off heating control decisions. This intermediary absorbs the complexity while presenting a simplified interface to both the EWH and utility company.
2Reliability
If safe deferred time is determined based on reserve capacity, then customer comfort is maintained, but measurement precision requirements increase due to need for accurate reserve capacity determination
Solution Approach 1:
The system implements feedback mechanisms that continuously monitor actual power usage and compare it against predicted usage patterns. This feedback allows the system to refine its reserve capacity determination over time, using historical data to improve accuracy without requiring ultra-precise measurements at any single moment. The feedback loop compensates for measurement uncertainties through adaptive learning.
Solution Approach 2:
The system determines reserve capacity in advance based on historical power usage patterns and stochastic predictions rather than requiring precise real-time measurements. By using preliminary determination based on accumulated historical data, the system reduces the immediate measurement precision requirements while still maintaining reliable customer comfort through proactive reserve capacity planning.
3Productivity
If EWH delays heating during grid service events, then aggregate power demand is reduced, but risk of water temperature insufficiency increases
Solution Approach 1:
The system performs preliminary heating of water reserves before grid service events by calculating safe deferred time based on determined reserve capacity. This preliminary action ensures that sufficient hot water is stored in advance, allowing the EWH to delay heating during grid events without risking temperature insufficiency. The preliminary action creates a buffer that decouples power demand reduction from water temperature reliability.
Solution Approach 2:
The patent implements beforehand cushioning by maintaining a reserve of hot water at safe temperature levels prior to grid service events. This cushioning buffer, determined through reserve capacity calculation and safe deferred time determination, protects against the risk of temperature insufficiency while enabling power demand reduction during actual grid events. The cushioning absorbs the shock of delayed heating without compromising service reliability.
Data Source
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AI summary
Control of an electric water heater based on a two-mass model may be provided. First, a reserve capacity of an Electric Water Heater (EWH) may be determined. Next, a safe deferred time for the EWH based on the determined reserve capacity may be determined. Then a grid service event initiation may be received. In response to receiving the grid service event initiation, the EWH may be caused to not heat water for the determined safe deferred time.