Something for Everybody
We are doing a solar project that will scale in stages to show how to do modern solar power projects from a simple cabin or small house off-grid, to a light industrial or commercial 3 phase system with all the stages in between. The intention is to demonstrate how versatile hybrid inverter system are and how far they can be scaled. We’re using the same inverter and battery system in this project for each stage.
While this might seem extremely ambitious, it’s really a way to simplify a project we have underway. We’re building a solar system to power my shop, which is supplied from the grid with three phase electricity. As I worked on the planning it occurred to me that it would be easier, and more useful, to build the system in stages, and that because of the versatility of the equipment I’ve selected, we can build what is essentially all of the kinds of systems any person or business would consider. We’ll cover this in deep detail, but people with a more casual interest can view the videos and understand the stages of the project. We’ll provide links to all the equipment and tools we use. Our links are affiliate links, which means we receive a small commission on anything you purchase. The links do NOT affect the price you pay.
The stages we have chosen to cover are:
Phase 1. Solar and battery off-grid system–a 120/240 volt AC system providing adequate power to run a small house off-grid. The inverter can manage 18000 watts of solar power and provide 12000 watts of 120/240 split phase AC with an additional 6000 watts of PV power to charge the battery. The battery we have chosen is a wall mounted 48V 280Ah 14.3kWh LiFePO4 All Weather Lithium (LiFePO4) Battery. A typical home in the USA uses 20KWh per day. A tiny home or cabin can use much less than that–some as little as 4KWh/day. Even if a tiny home or cabin was using a mini split heat pump to maintain internal temperature at 70 degrees, summer and winter, it would use about 9,000 BTUs of heating/cooling capacity. For a unit of this size, the power consumption would typically be in the range of 600-900 watts per hour when running, so 14KWh to 22KWh per day in the unlikely event it ran 24/7. We’ll be testing that by insulating the space our inverters will inhabit (about 20′ X 8′ = 160 square feet) and and installing a 13000 BTU mini-split heat pump. The inverter system we are using can manage a generator to provide continuous power when there is no sun. The Off Grid design we are building uses a surplus of solar generation to enable charging an EV while keeping up with daytime household loads and topping off the battery.
Phase 2. Solar and Battery Partial Home Backup, Grid connected –a 120/240 volt AC system providing adequate power to supply critical loads when the grid is down. The battery we have chosen is a wall mounted 48V 280Ah 14.3kWh LiFePO4 All Weather Lithium (LiFePO4) Battery. Critical loads in most homes require about 6 KWh per day (about 500 watts for 12 hours) so the system can supply those loads for about two days with no solar input. The inverter system we are using can manage a generator to provide continuous power when there is no sun, but in typical critical load situations with solar power available the system can easily manage the critical loads and charge the battery completely each day. In our demonstration the partial home backup will be simulated by describing how the wiring would be done and the equipment would be configured. We’re not actually going to create a critical loads panel which we would then have to abandon in phase 3.
Phase 3. Solar and Battery Full Home Backup, Grid Connected –120/240 split phase AC system providing adequate power to supply all house loads when the grid is down. The system uses two inverters which manage 36000 watts of solar power and provide 24000 watts of 120/240 split phase AC with an additional 12000 watts of PV power to charge the batteries. The two wall mounted 48V 280Ah 14.3kWh LiFePO4 All Weather Lithium (LiFePO4) Batteries provide 28.6KWh of reserve power. Typical loads in US homes require about 20 KWh per day so the system can supply those loads for about 1.5 days with no solar input. The inverter system we are using can manage a generator to provide continuous power when there is no sun, but with solar power available the system can easily manage all loads and charge the battery completely each day and charge an EV when there is adequate solar power.
Phase 4. Solar and Battery 3-phase Commercial/Light Industrial Grid Connected –a 120/208 volt three phase AC system providing adequate power to back up commercial/light industrial loads when the grid is down. The system uses three inverters which manage 54000 watts of solar power and provide 36000 watts of 120/208 wye connected three phase AC with an additional 18000 watts of PV power to charge the batteries. The three wall mounted 48V 280Ah 14.3kWh LiFePO4 All Weather Lithium (LiFePO4) Batteries provide 42.9KWh of reserve power. The inverter system we are using can manage a generator to provide continuous power when there is no sun, but with solar power available the system can easily manage critical loads and charge the battery completely each day.
Alternative Applications We are Not Covering: The equipment we are using can manage additional use scenarios such as Grid Connected No Battery systems managing both AC-coupled and DC-coupled PV arrays, and peak shaving systems with or without solar panels to supply homes or businesses when peak load charges apply. The sophisticated power management systems in the inverters we are using enables economical ways to reduce power bills.
Equipment: the links below are affiliate links. I earn a small commission if you use them to buy products from signature Solar. The price you pay is unaffected–the commissions help support our channel.
The hybrid inverter we have chosen after a substantial amount of research is the EG4 18kPV Hybrid Inverter that we purchased from Signature Solar, an all-an-one Solar Inverter with 18000 watts of Photovoltaic panel input and 12000W of 120/240V Split Phase AC Output. The 18K has three independent mppt controllers enabling mixing of panels and mounting locations. We’ll cover the full specifications later, but after months of research these are the systems we chose for this project. There are other solutions that make more sense for other projects, for example, more demanding three phase installations benefit from 300volt battery systems and larger inverters like Sol Ark commercial systems that are three-phase in single, scalable units–we’ll cover that later. https://signaturesolar.com/eg4-18kpv-hybrid-inverter-all-in-one-solar-inverter-eg4-18kpv-12lv/?ref=vzthklvr
The Batteries we have chosen, also from Signature Solar, are the EG4 PowerPro Wall Mount All Weather 48V 280Ah 14.3kWh LiFePO4 Lithium Battery. Other 48V solutions, paticularly rack mount systems, are more suitable for smaller installations or installations where smaller units of modularity is beneficial, but for our system, the lower cost per KWh, ease of installation, ability to scale rapidly, and appearance made wall mount batteries preferable. https://signaturesolar.com/eg4-powerpro-14kwh-all-weather-lithium-solar-battery-wallmount/?ref=vzthklvr
The solar panels we are using are Aptos 370 watt bifacial panels. These panels are 370W Bifacial Solar Panel (Black) and provide up to 480W with Bifacial Gain. We bought a full pallet (31 panels) and will be buying more. At $.28 per watt these are an amazing bargain, one pallet is 11470 watts (11.47KW) before bifacial gain. The panels are also available from signature solar in lots of ten. https://signaturesolar.com/11-47kw-pallet-aptos-370w-bifacial-solar-panel-black-up-to-480w-bifacial-gain-dna-120-bf26-370w-full-pallet-31-11-47kw-total/?ref=vzthklvr
For managing the wiring we are using the EG4 PowerPro Conduit Box which fits perfectly between the 18K inverter and both styles of wallmount battery that Signature Solar carries: https://signaturesolar.com/eg4-powerpro-conduit-box/?ref=vzthklvr
To connect the batteries in parallel we are adding EG4 paralleling cable which come with the high current plugs already installed: https://signaturesolar.com/eg4-powerpro-battery-paralleling-cables/
Our mounting system takes two approaches. One is a container mount we built our self from welded steel. It pivots on the edge of a 40 foot, high cube container we moved close to the shop. The panels are mounted on standard unistrut (superstrut) with end and mid panel mounting clamps modified to use 3/8″ bolts to connect to twist-lock nuts. The sections are a little over 10 feet long (127 inches) to accommodate the width of the Aptos panels (40.75″) plus the mid-panel and end clamp mounting hardware widths. The second approach is various ground mount systems that we are testing for durability and maintenance. We ignored roof mounting for two reasons–the roof on our shop is about 15 years old. I don’t want to poke holes in it and I don’t want to pull the panels off when the roof needs to be replaced. But the bigger reason is that ground mounts are gaining in popularity wherever they are feasible. The much greater access for maintenance or cleaning makes them preferable. The downside of course is that they take up ground space and many homeowners simply don’t have unshaded space the is suitable. I do, as do many suburbanites.
I have to say, the container rack is WAY more work than I expected. I’ve built two of the four ten foot racks and it took more time and effort for those two than I planned for the entire container part of the project. The 100+ degree heat didn’t help, but mostly it was simply that welding large racks is a lot of work, and with the weight of steel it seems I’m chasing the strength requirement–most of the strength required is for supporting the steel, not the panels. The ground mount approach will be simpler–I think. I hope.