Photovoltaic-Assisted Heat Pump Water Heater Integrates Use of Solar and Conventional Energy Sources

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As shown in the example, the PV-Assisted Heat Pump Water Heater system has a residential compressor-refrigerant-based storage type water heating system with (A) PV modules and microinverters, (B) a programmable smart controller, and (C) a resistance heating circuitry that allows the resistance heater to work with varying levels of electrical power.
Carlos Colon
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Issa Batarseh, Ph.D.
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Danny S. Parker
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Provisional Patent Application Filed

Energy-Saving System Provides Steady, Reliable Supply of Hot Water by Dynamically Switching Between Solar Energy and Electricity from a Power Grid

UCF researchers have developed a heat pump water heater (HPWH) system that enables homes and businesses to maintain a steady supply of hot water while optimizing energy usage from both solar panels and conventional power sources. Cost-efficient and easily implemented, the new Photovoltaic-Assisted Heat Pump Water Heater system operates with standard heat pump water heaters and PV modules. Key to the system is a customizable and programmable controller that allows extended thermal energy storage that can displace, shift and save electricity.

To operate efficiently, current HPWHs require a steady supply of electrical power, such as electricity provided by a local power plant. As a result, such HPWHs cannot interact efficiently with a variable source of electrical power, such as direct power from a solar PV system. The invention resolves the problem by providing a hybrid and highly efficient process that integrates solar power usage and conventional electric energy from a grid. For instance, when running on solar power, the system stores thermal energy in the form of hot water. Thus, residential homes and commercial sites can store and use optimal levels of hot water both day and night. The new system also yields a cooling byproduct that provides supplemental cooling or dehumidification to a living or non-living space (garage)—an added benefit for hot-humid climates.

Technical Details

The invention comprises the following:

  • At least two PV modules and microinverters for collecting sunlight and producing solar power
  • A commercially available heat pump water heater ( electricity from a power grid)
  • An electronic, customizable smart controller with a unique algorithm that enables the system to interface with and dynamically switch between solar resources and the resistive heating system connected to the conventional power grid. The controller works to consume or store all energy into the system as hot water to avoid having to export power back into the grid.
In one example use of the system, its 1-year averaged coefficient of performance (COP) was 5.4 and a daily average grid-energy consumption of only 1.2-kilowatt hours per day. The system easily provides hot water for a family of four (59 gallons per day) regulating delivery temperatures to 125 F.


  • Simple to manufacture and install
  • Highly energy efficient, reliable and cost-effective
  • Consumes less grid power than standard HPWHs and sends less PV power to the grid


  • Residential or commercial water heating (such as single-family homes, hospitals and restaurants)
  • Supplemental cooling/dehumidification

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