Today, some in Europe are worried about rising energy prices, and even if all the fears associated with this disappear overnight, we will certainly see some price increases. As a hacker, you can take a good look at the energy-hungry devices in your home and even take action on them. So, [Peter] installed some solar panels on his roof, but couldn’t figure out how to legally connect them to the public grid, or at least to the 220V mains in his apartment. Of course, a good solution is to build a separate parallel LVDC network and put a bunch of devices on it!
He chose 48V because it’s high enough, efficient, easy to get things like DC-DC, safe when it comes to legal matters, and generally compatible with his solar panel setup. Since then, he’s kept devices like laptops, chargers, and lights on DC power rails rather than plugging them in directly, and his home infrastructure (including a rack full of Raspberry Pi boards) is perfectly content to operate 24/7. rail 48V. There is a backup power supply from the regular AC power supply in case of cloudy weather, and in the event of a power outage, two huge LiFePO4 batteries will power all connected equipment at 48V for up to two and a half days.
The device produced and consumed 115 kWh in the first two months – a huge contribution to the energy independence hacker project, and the blog post has enough detail for all your inspiration needs. This project is a reminder that low voltage DC projects are a good option on a local scale – we’ve seen viable pilot projects at Hackcamp, but you can also build a small DC UPS if you like. Perhaps soon we will find an outlet for such a network.
Cellular base stations currently use 48V. I need to set up something similar for a neighborhood watch project.
I was thinking about running some HP DL360 servers at home with solar panels and batteries without 48VDC power supplies that would fit these servers and avoid the inefficiency of the DC-to-AC inverter, but then I saw the price of these power supplies at 48 VDC. … MY GOD. Return on investment until 2050!
48V has been the bus voltage in telecommunications systems since Strowger’s time (with giant batteries) and carried over into fiber optic network equipment.
Yes, the entire telecom industry runs on 48VDC. From old analog switches to modern cellular base stations. IT data centers are typically powered by AC power.
GOOD The only bummer with this setup (assuming the other half is approved and kept in a safe place away from pets and children) is that once the local energy storage is full, the excess energy is wasted when you are this close to the grid. interconnects are going, it’s probably really a shame that that energy is spent on cheap ones. I don’t blame them for this situation, they’ve done a job for themselves and can’t find a legal/safe/affordable way around this last hurdle…bureaucrats are probably better off than lawyers and politicians. although they often resemble each other in life, perhaps they are all different states of the same life form…
I would say to make life easier for those non-tech people with DC you will probably live with or support the best option available today which is probably USB powered…although I hate it because the power supply over USB it’s a mess, getting it right seems like a huge problem, and it’s not likely to be as efficient as a 48V rail. It’s so ubiquitous that it’s understandable to non-technical people – because it’s pluggable and works (if configured correctly). Eliminate the need to find the right DC-DC converter for everything or actively monitor the “power supply” voltage every time you plug in a new device – I do this at my desk but haven’t fried anything yet…
But as an off the shelf battery pack with a solar tracking input, maybe even as an inverter for the AC pack you should have, and if you want to avoid building your own more annoying USB power supply, you can use the USB power negotiation thing. It’s not too hard for you to set up. Also, it’s more than enough for the hackers among us to install solar panels (preferably on sun-tracking mounts), provide status monitors, low-battery alerts, and neatly organize cables in the single most important place for fraudulent work. A little…
A good solution for excess energy is to dump loads such as electrical components into the water heater. Once the battery is fully charged, it can switch to using available solar energy to heat water.
Although the water heater can also “fill up” (hot enough) over time, unless it is very large.
The advantage of solar energy is that you don’t have to collect solar energy. You can safely place the panels under the sun’s rays without using potential energy.
Of course, this is a waste, and if it is to your advantage, feeding power to the grid is the first choice.
As CityZen says, it will fill up over time, it’s just another form of energy storage. Not to mention, if you already live in a hot area, your air conditioner will work harder if you have it, and if not, your life will be more unpleasant than it should be, because the tank is insulated just so… Water really is a very good energy store, but most homes don’t really need that much hot water, and a larger single tank setup means that when you don’t have free energy, you still have plenty of water to make full use of. higher for heating due to the huge surface area it causes.
There really is no good “offload” on an individual scale, a large network with large plants can easily run a few extra shifts and increase production beyond demand to make the most of “free” energy. But personally, it’s just an excuse to play loud and rock 24/7, carefree use of energy while it lasts or until the neighbor kills you.
However, in warm to hot weather, absorption cooling can help use excess heat to cool apartments.
You can also run a small room air conditioner with an inverter if you have a lot of excess power to turn off and it’s hot. Maybe the inverter is outside… It would be very interesting to see if you can make a heat pump that uses outside air as a heat source/radiator. Sure, it’s really inefficient, but if your problem is too much power, the inefficiency will almost help.
@smellsofbikes Just because you sometimes have too much power and can build something inefficiently doesn’t mean you should. What happens when you’re low on energy right now but still have to go through a very inefficient process? Like my giant water tank example above, you have to find a reasonable balance so that when you’re low on energy and when you have enough energy for a heavy metal concert, important/useful things can be completed… . ..
When you can not give for money or why not give for free **? Then all the excess you can create is just the potential that you are not using, and it is not the end of the world, just a shame.
** Assuming this doesn’t require you to make any active costs – which is a major issue here, the “flat fee” for a network connection is significant, so even if you don’t use most of your connection it will probably cost more . than they send it to you. They pay you for excess – not that I’m against giving away excess, it works for some people in this giant network and I don’t need it. But paying a company that much for the privilege of making more money from other people…
As USB powered devices become more common, I thought of something similar for 5V. Even better would be multiple 5V USB C ports and multiple AC ports. From there, you can use 5V for low power devices and USB C for high power devices. The downside is that USB C ports have to handle voltage per port while USB A 5v is just a 5v rail.
At the very least, I’m pretty sure I’ll end up building an office with 5V USB powered mains. I’d probably do 12V too, as my electronic projects that require more than 5V almost always require 12V. (Also, I’m pretty sure every router I own uses 12V, and it would be nice to have simple individual outlets for each device instead of a wall transformer!)
I’m sorry to tell you that 5V (or even 12V) is bad for power distribution: just a meter or two of dragging cable with losses of 10% or more is practically unusable. Cars struggle with 12v all the time, but since they’re small they can handle it, but trucks and big boats use 24v, so yes, 48v is the best value: still a safe range rating as long as you don’t lick it . standard voltage, sufficient equipment and the ability to transport a certain length without much loss.
Power conversion losses are more important than cable losses. For example, in the case of this article, assuming that each DC-to-DC conversion is 90% efficient, we end up losing 27% of the power we get from a 5V USB charger. If the converter is slightly worse, by 85%, then the losses will reach 39%. Charge controllers and converters in practice typically achieve around 80% efficiency, so it’s not uncommon to lose up to half the energy just for voltage regulation. If the system demand is low, idle equipment losses can consume almost all power.
Unless you’re using thick cables, cable losses can be quite high at 5V, and you’ll probably spend more on those cables than you would for an efficient 24V conversion.
If you have two dozen 5W USB ports, you need a 120W power supply. If the power supply had a constant base load of 10W, the nominal “efficiency” at the specified load would be 92%, but when the average USB port utilization is about 5%, the overall real system efficiency is about 60%. .
Anything below the absolute minimum of 36V should not be used over long distances. Especially not 5v. Power adapters are so cheap, copper is expensive and heavy. Batteries are also expensive and power loss is a problem.
Personally, I wouldn’t make any kind of LVDC microgrid at all (I used to play with it and hated it so much I made a whole video about it).
I always say put the battery at the load point and use an extension cord if you need power. The exception is PoE, which is practically free for Ethernet and you may need it for other purposes.
USB-C for all your projects, powered by external batteries and wall adapters as needed. Be aware that USB-PD trigger modules exist, you can get 9, 15 or 20 if you like (12V is obsolete and probably won’t work with newer adapters IIRC)
If you want to use solar power, 12V is good for small runs up to 100W for a few feet, and is also more common than 5V and 48V etc, go for it. Or just buy a commercial LifePO4 solar generator, they are fantastic.
Every aspiring do-it-yourselfer always wants to do something with the DC bus, but that’s usually a bad thing because consumer devices aren’t designed for it and you lose the “just works” aspect of the USB wart that ends up all over the place. It’s bulky cables and a bunch of non-standard connectors that don’t fit the rest of the world and are just a hassle for your DIY system.
The best implementation I’ve seen is the ARES standard for ham radio, but even then… it’s only good for short runs.
For 5V power in the office, I just use a wall outlet with a built-in transformer and a USB port.
For 12V for routers and other things to clear up, I would just buy a big 12V 5A transformer and a 2.1mm Y-cable (make sure you get decent ones) or wait until the trigger module is available PPS for 12V, take 12V. USB from newer devices – port C.
Or better yet, phase out non-USB power whenever possible. Spending a little more on an upgrade to get all USB-PDs will solve the whole problem when you need a new router or any high-end router that is likely to be USB powered.
If I really wanted a 12V outlet, I would consider putting a Mean Well wired transformer in a service box next to the outlet instead of actually using 12V. No single point of failure, power loss in thick or thin cable, simple and obvious repair.
120V DC is fine to power most “AC” sources, but that’s the lowest limit of what they’re happy with. They prefer 160VDC or higher.
No, in my experience they cut off around 65Vdc, but you should also derate below 130Vdc, I haven’t measured, but I’m assuming a 100-0% linear drop from 130-65Vdc.
Strange assumption. I am assuming that the input circuit is handling some fixed current. This means that when the voltage reaches 130V to 65V, the rating is reduced to 50%, and below 65V, some other voltage blocking circuit is triggered.
Many substations have a battery that powers the safety relays and allows circuit breakers to operate (open and charge) in the event of a power outage. The standard voltage is 115 VDC. It runs 100% on battery and has an AC->DC charger to ensure the battery is always fully charged, so there is no solar in this case.
According to Motzenbocker’s book “Reclaiming the Power” https://yugeshima.com/diygrid/ 120vdc only
The problem of DC power distribution was solved with the help of 802.3af (aka PoE) – Power over Ethernet. There is really no need to use the Ethernet part of the equation. Ubiquitous adapters, secure power distribution and excellent reporting/management tools. It’s not even expensive – you can get a 100Mbps 48-port data center level hub for as little as £30.
The Marcel Hotel in New Haven has 164 rooms, all powered by solar and wired DC power. Here is a good overview: https://www.youtube.com/watch?v=J4aTcU6Fzoc.
I was going to mention it, they use POE. The losses caused by operation must be less than the losses when switching from DC to AC and back to DC. Also gives you built-in analytics about what you are using.
Sometimes I forget that I live offline. I have a 48VDC to 220VAC inverter in my setup that puts out about 5kW continuously, although it has never been heavily loaded. A 220 volt water pump, a refrigerator, a freezer, appliances, tools, lighting, all this is standard for swamps. I have separate 12V and 24V DC and/or most other types of power settings. Run a steel structure business in the same facility and pump drinking water for the big horse. The batteries are from a large UPS system that I get when I change batteries on a schedule. Do a voltage test on the batteries, select the best ones, then insert a resistance heater, again monitoring the voltage, select the best ones again and buy them.
Yes, most devices with a “universal” AC input can run on DC power. Multiply the AC input voltage by 1.4 to get the equivalent DC voltage. However, their internal fuses are not DC rated. Replace them with a DC fuse or use an external fuse. Don’t set fire to the house!
> “This means that the maximum circuit voltage is about 0.80 V. In the event of a fire (hopefully never), this would not pose a significant danger to the fire brigade.”
The ELV standard considers 120 VDC “safe” without ripple, but the EU General Safety Standard limits it to 75 VDC, while the Low Voltage Directive applies to any voltage in the 75-1000 VDC range. You can still break the law and need a permit to install such a system, but it’s hard to find a clear answer or any documentation of exactly what you can do as a solo builder without special training.
Post time: Jul-19-2023