Device and method for converting solar PV energy into thermal energy storage using combined heat-pump and resistive heating elements in water heater
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional electric water heaters are inefficient in terms of energy consumption, and alternative methods like gas water heating and 'wet' solar panels have limitations in availability and suitability, while heat pump-based systems face challenges in starting surge requirements and power balancing with solar PV energy.
Innovation Solution
A system that combines photovoltaics with an MPPT DC/DC converter to power a DC bus, using an electric heat pump and a resistive heating element, controlled by a microcontroller to optimize energy use based on available solar power, switching between heat pump and resistive heating depending on power availability, and incorporating energy storage to manage starting surges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If heat pump-based water heater is used to reduce energy consumption, then energy efficiency is improved, but starting surge requirements cannot be met with limited solar PV power
Solution Approach 1:
The heating system is segmented into two independent heating elements: a heat pump for efficient heating and a resistive heating element for supplemental heating and starting surge support. This segmentation allows each component to address specific requirements without compromising the other.
Solution Approach 2:
A dual-power water heater system acts as an intermediary between solar PV power and the heating load, incorporating both heat pump and resistive heating elements. The controller mediates power distribution, using the resistive element to provide starting surge power when solar power is insufficient, enabling the heat pump to operate efficiently during adequate solar conditions.
2Adaptability or versatility
If heat pump is operated with variable frequency drive to match solar power availability, then adaptability to solar power fluctuations is improved, but device complexity increases
Solution Approach 1:
The heat pump motor is equipped with a variable frequency drive (VFD) that dynamically adjusts operating frequency based on available solar power. The controller continuously monitors solar PV power availability and modulates the heat pump motor frequency accordingly, enabling the system to adapt to fluctuating solar conditions and maximize energy utilization.
Solution Approach 2:
The system changes operational parameters by adjusting the frequency of the heat pump motor via VFD based on solar power availability. When solar power is sufficient, the heat pump operates at higher frequencies for maximum efficiency; when solar power is limited, the frequency is reduced or the resistive heating element is activated, optimizing system performance under varying conditions.
3Reliability
If resistive heating element is used when solar power is insufficient, then heating reliability is improved, but energy efficiency deteriorates
Solution Approach 1:
The resistive heating element provides partial heating action when solar power is insufficient, supplementing the heat pump rather than replacing it entirely. This partial action ensures continuous hot water supply and heating reliability while minimizing the use of less efficient resistive heating, thereby balancing reliability requirements with energy efficiency considerations.
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 system efficiently utilizes solar PV energy to heat water, reducing energy consumption by operating the heat pump when sufficient power is available and using the resistive element otherwise, thereby achieving faster water heating and minimizing energy waste.
Implementation Method 1
A system uses photovoltaics and an MPPT DC/DC converter to power a DC bus
Implementation Method 2
The heat pump principle is well known and is mainly used for air conditioning and refrigeration systems, where heat is a nuisance product of the process and is rejected into the environment
Implementation Method 3
Traditional electric water heaters are based on a resistive element that converts electric energy into the heat
Data Source
AI summary
Photovoltaics and an MPPT DC/DC converter powers a DC bus of a controller. It uses an electric heat pump to heat a mass like water, and also has a resistive heating element to heat the mass. A microcontroller controls a variable frequency (VFD) motor drive to power the electric heat pump when sufficient solar power is available to run the heat pump and uses the resistive element to heat the thermal mass when insufficient solar power exists for the heat pump or when excess solar power is available. A controller has an MPPT input for solar power and a VFD to provide power through an output to a heat pump-based water heater and an output to power a resistive water heating element. A microcontroller determines solar power available and runs the heat pump when possible and the resistive element when insufficient power is available or when excess power is available.