Swing Tank Step Modulation for Heat Pump Water Heater Efficiency
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Solution Overview
Problem
Heat pump water heaters experience reduced efficiency and heating capacity in low ambient temperatures, necessitating a system that can efficiently switch between heat pump and electric resistance heating based on ambient conditions to maintain optimal performance.
Innovation Solution
A swing tank with adjustable electric resistance heating elements controlled by an outdoor temperature sensor, activating one, two, or all three banks of heating elements based on ambient temperature to maintain efficient hot water supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If heat pump water heater is used to provide efficient heating, then energy efficiency is improved, but heating capacity deteriorates in low ambient temperatures
Solution Approach 1:
The system dynamically adjusts the configuration of swing tanks based on ambient temperature conditions. When ambient temperature is high, the heat pump operates efficiently with swing tanks in a first configuration. When ambient temperature drops below a threshold, the system automatically reconfigures the swing tanks to a second configuration, transitioning from static to dynamic adaptation to maintain optimal performance across varying conditions.
Solution Approach 2:
The system changes operational parameters by switching between different swing tank configurations based on ambient temperature. The controller monitors temperature and adjusts the system configuration accordingly, changing the operational state from heat pump-dominated at high temperatures to a mode that incorporates electric resistance heating elements at low temperatures, thus adapting to maintain heating capacity while preserving energy efficiency when possible.
2Power
If electric resistance heating elements are activated to provide heating in low temperatures, then heating capacity is improved, but energy efficiency deteriorates
Solution Approach 1:
The system applies partial action by selectively activating only the necessary heating elements based on ambient temperature conditions. Rather than continuously operating all heating elements, the controller activates electric resistance heating elements only when ambient temperature falls below a predetermined threshold and only to the extent needed to maintain water temperature, thus providing sufficient heating capacity while minimizing energy waste.
Solution Approach 2:
The system performs self-service through automatic temperature monitoring and control. The controller continuously monitors ambient temperature and automatically adjusts the activation of heating elements without manual intervention, enabling the system to self-regulate and switch between efficient heat pump operation and necessary resistance heating based on real-time conditions.
3Reliability
If heat pump is deactivated in low temperature conditions, then system reliability is improved by avoiding inefficient operation, but heating capability deteriorates
Solution Approach 1:
The system implements beforehand cushioning by pre-configuring backup electric resistance heating elements that are ready to activate when the heat pump becomes inefficient. Rather than allowing the heat pump to operate in inefficient low-temperature conditions, the system has predetermined backup heating capacity available to immediately take over or supplement when needed, thus maintaining heating capability while avoiding unreliable inefficient operation.
4Quantity of substance
If swing tank capacity is increased to maintain hot water supply, then hot water availability is improved, but system complexity increases
Solution Approach 1:
The system applies segmentation by dividing the hot water storage function across multiple swing tanks rather than using one large tank. The swing tanks can be configured in series or parallel arrangements, allowing the system to achieve the necessary total storage capacity while maintaining manageable individual tank sizes and simplifying installation, maintenance, and control compared to a single large complex system.
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
The system maintains efficient hot water supply across varying ambient temperatures, optimizing energy use and providing backup heating when the heat pump is offline.
Implementation Method 1
heat pump water heater which adjusts the level of supplemental heat provided in a heat pump water heater system under changing ambient air conditions
Implementation Method 2
Three banks of three electric resistance heating elements each are positioned within the swing tank
Implementation Method 3
controller connected to an exterior outdoor temperature sensor mounted in the vicinity of the heat pump water heater to receive measured ambient air temperature levels
Data Source
AI summary
A water heating system has an exterior heat pump water heater supplying heated water to a storage tank connected to a recirculation loop with a swing tank. A controller receives measured ambient air temperature from an outdoor temperature sensor mounted exterior to the building near the heat pump water heater. The swing tank has three banks of resistance heating elements arranged into first, second and third heating sectors controlled by the controller. When ambient temperatures are more than about 8 degrees Fahrenheit above freezing, only the first heating sector heating elements are activated when heating is called for. When ambient temperature is less than this level and greater than about 8 degrees Fahrenheit below freezing, the heating elements in the first and second heating sectors are activated. When the ambient temperature is less than this, all heating sectors are activated, thus providing advantageous levels of hot water heating efficiency.