DC Microgrid Inverter Elimination for Building Energy Efficiency
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Solution Overview
Problem
Current AC building systems inefficiently utilize locally-generated renewable energy, requiring reliable utility grid connections and incurring excess life-cycle costs and energy security concerns due to AC-DC and DC-AC conversion losses, and lack effective management of peak power demands.
Innovation Solution
A DC microgrid system that powers DC devices without inverters, utilizing energy storage like batteries to efficiently manage and optimize power sources and loads, reducing reliance on grid electricity and incorporating solar synchronized load and maximum power point tracking control for efficient energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If AC building systems are used with conventional PV arrays and inverters, then grid connection reliability is maintained, but energy conversion losses increase and total cost of ownership increases
Solution Approach 1:
The patent extracts and removes the inverter component from the system by implementing a DC microgrid architecture that eliminates the need for AC-DC conversion. DC-powered devices are directly connected to the DC bus, bypassing the inverter entirely and eliminating associated conversion losses and hardware complexity
Solution Approach 2:
Instead of converting DC power to AC power (the conventional approach), the system inverts the approach by maintaining DC power throughout the building and directly powering DC devices. This reversal of the conversion direction eliminates the harmful AC-DC conversion step
2Reliability
If PV arrays are integrated with AC building systems, then renewable energy generation is achieved, but energy security decreases during grid outages
Solution Approach 1:
The system performs preliminary action by pre-charging batteries during grid-outage-prone periods using PV generation. The energy storage system is prepared in advance to immediately supply power when grid failure occurs, ensuring continuous operation of critical DC loads without interruption
Solution Approach 2:
The patent introduces an intermediary element (battery energy storage system) between the PV array and DC loads. This intermediary enables the system to decouple from the grid while maintaining power supply, allowing PV-generated energy to be stored and dispatched independently of grid availability
3Use of energy by moving object
If AC-to-DC conversion is implemented for DC loads, then compatibility with AC grid is achieved, but energy efficiency decreases
Solution Approach 1:
The system changes the electrical parameter from AC to DC throughout the building infrastructure. By maintaining DC voltage levels from the PV array through the DC bus to the loads, the system eliminates unnecessary AC-DC conversion steps while ensuring all connected devices are DC-compatible, thereby improving overall energy efficiency
4Productivity
If conventional PV systems are implemented with full grid connection, then maximum power utilization is achieved, but demand charge management capability is limited
Solution Approach 1:
The patent implements feedback control through the DC microgrid controller that continuously monitors PV generation, battery state of charge, and load requirements. This feedback mechanism enables real-time optimization of power flow, allowing the system to respond to demand charge signals by adjusting PV export and battery discharge rates to minimize peak demand charges
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 DC microgrid system achieves reduced total cost of ownership, increased energy security, and improved efficiency by minimizing conversion losses and enabling backup power during outages, with potential for 15%-25% improvement in Savings to Investment Ratio over 25 years compared to AC systems.
Implementation Method 1
DC microgrid offers more efficient use of DC power generated by a Photovoltaic (PV) solar array
Implementation Method 2
A DC microgrid system that powers DC devices without inverters, utilizing energy storage like batteries to efficiently manage and optimize power sources and loads
Data Source
AI summary
A DC building electrical system includes a DC power consuming device connected to a DC bus. A source of DC power is connected to the DC bus and powers the DC power consuming device. An energy storage device is connected to the DC bus and to a DC emergency load. The energy storage device powers the DC power consuming device in conjunction with the source of DC power, and powers the DC emergency load when source of power other than the energy storage device is available to the DC power consuming device.