DC power is used all the time in the tiny floating houses we call boats.
Many people live on barges, sailboats and power boats of various kinds, either in harbours or in remote locations. Or, of course, travelling between the two. Another off-grid use like this is remote living on land.
Depending on exactly how close you’d like to get to urban life, this lifestyle requires the use of a lot of batteries, big inverters, and consequently plenty of charging capability. Boaters have different approaches to the issue: some use an AC generator and divert some power to battery charging so that the generator does not have to be on all the time; some use a small diesel DC generator to charge the batteries and everything runs off them, using inverters to create AC mains power; many, especially sailboats in transit, use multiple types of small renewable power sources such as solar, wind and towed turbines to charge their batteries, or to assist the main charging device such as a diesel generator of some kind.
The battery banks at this time are mostly variants on the 12 volt battery theme as this is currently the cheapest amps-per-dollar electrical storage system at small scale. Battery banks (groups of batteries connected together) can be 6v or 12v cells, and organised to provide 12, 24 or 48 volts for the inverters. 24 volts is a good solution for up to 3 kW inverters, to run for example a domestic washing machine for clothes.
Li-ion cells are making headway though, and if Tesla’s Powerwall gains a reputation for reliability we might see it (or similar offerings) used for remote marine applications; then, the 12 and 6 volt traction batteries currently the best choice will have a competitor. The lithium cell approach is more compact and much lighter, but at higher cost.
Marine-based users will first want to see a history of 99% reliability with Li-ion packs, as is available with lead-acid. Only the worst cases of bad luck or breakdown wreck lead-acid power banks: a full-on lightning strike or an alternator malfunction that cooks the batteries, for example. These don’t happen often. Battery failure might in the worst case lead to a life or death situation on boats, so going the Li-ion route is a real leap in the dark currently.
I’ve been part of a community that has used small Li-ion power banks extensively since 2010, and the most common feature of that use has been fires and explosions. Progress is quick though, so what applied 5 years ago (never use power banks based on Li-ion or any similar technology, it’s far too dangerous) has changed to: use lithium-associated technology with caution: thermal runaway issues must be very carefully countered by cryogenic or similar cooling plant, and the charge and discharge parameters must be controlled about a million times more carefully than for lead-acid or similar technologies.
It’s not easy to get right. If your lithium power bank is designed by idiots without a clue, like the Boeing Dreamliners’ were, expect numerous fires and failures. You need real expertise to design lithium systems properly and it’s far from universal. They don’t even know how to do it at Boeing, despite the vast funds available, which should give you a clue about the problems.
The two things you’d need to know before going the off-grid route – as this is basically what you’re talking about – are:
- Even if you cut back a bit compared to mains electrical power use in a house, a normal urban lifestyle uses a ginormous amount of electricity. Going off-grid in any way, on land or water, demands economies in that area. You just can’t afford to squander power as if it is an endless and infinite resource.
- In order to support a battery-powered lifestyle, you need a lot more batteries and more charging capability than you’d think. Generally, a very great deal more. Big charging capability (diesel or solar/wind etc.), big battery banks, and big inverters. Actually a range of inverters, as you want to be running the smallest you can use at any time, as they have an overhead (a small drain current) proportionate to size, whether or not AC is being drawn.
The other thing is the investment cost. Using AC mains has a convenient monthly payment plan. Using DC power takes an investment of hundreds, to thousands when doing it properly.