We have built and installed a simple 100% DC off grid solar power system in our house that uses NO charge controller and NO inverter. It has been operating 24×7 for the past few months with zero problems. Several years of testing and research are behind this project.
The system has the following features and capabilities:
NO Charge Controller: direct DC into the battery bank, through electromechanical ideal blocking diode (EIBD) with OVP/UVP functions.
Benefits: lower startup costs, lower complexity, less electronics to fail
NO Inverter: all appliances use 55V DC (Direct Current) natively with no switching or voltage conversion.
Benefits: no switching noise (EMI/EMF), lower startup costs, lower complexity, less electronics to fail
DC Kitchen Appliances: we have the ability to cook food 24x7x365 without fuel using clean renewable PV solar power. If no battery is available, cooking can still take place during the day use PV2L / Direct Drive DC solar power.
Residential DC Wall Outlets: NEMA-15R receptacles are used to distribute power to each room in the house.
PV2L / Battery Optional Mode: the system can operate with or without a 51.2v LiFePO4 baattery. I call this Direct-PV, PV2L (PV-To-Load) mode. All wall outlets, appliances and devices are literally powered directly from the PV solar panels themselves!
Benefits: ability to bring the system online immediately without a battery, lower startup costs
Battery Integration Control: assuming a battery is available, after it is charged to 80% SoC it is simply switched off of the DC bus. During the day when there is plenty of solar power, the battery is not used, and everything in the house operates on direct-drive DC solar power!
Benefits: system does not need a battery immediately at system installation, lower startup / installation costs, fewer battery cycles required
Super Capacitors: the system can leverage supercapacitor banks (optional) if desired when running in PV2L mode. This makes it even less likely that the battery would get cycled during the day.
Benefits: less battery cycling, fewer PV2L-Battery transition events, ability to handle large surges without using the battery at all, easier to avoid the battery alltogether if needed
Space Heating: simple resistance space heaters can be powered from individual DC wall outlets throughout the house, either on Direct PV DC (PV2L) or in combination with 51.2v battery banks.
Benefits: easy and accessible conversion of excess PV solar power into supplemental and/or primary space heat at very low costs
Other features include presence detection, linking multiple buildings together in a DC micro grid, setting node priority, simple electromechanical controls, strong system resilience and fault tolerance, fault current protection, and much more.
There is so much more to this system design than I have had time to present, BUT I hope to write more about it later! Thanks for reading, take care! -Dave, SPE
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