Does it exist?  Power source mixer - Page 1
Forum section: electronics / general

author: GabYoung92
author_rank: Regular Contributor
timestamp: February 22, 2015, 11:37:03 pm
content: I've been searching but unable to find any information...I have a server that runs 24/7... To off set some of the power consumption I would like to some how feed some power from a solar panel. I have thought about a constant inverter mode UPS and feeding it in but not sure about this.Does anyone know of something that will prioritize the solar power and use mains when there isn't enough available (IE cloudy or night)?

author: SL4P
author_rank: Super Contributor
timestamp: February 22, 2015, 11:54:32 pm
content: Your UPS should do that automatically.Use the solar to charge the batteries (not the mains), and let the online UPS supply the load.In this (generic) diagram - you would replace the AC/DC charger with your solar charger

author: GabYoung92
author_rank: Regular Contributor
timestamp: February 23, 2015, 12:01:45 am
content: If the AC/DC charger is removed and replaced with a solar charger, correct me if I'm wrong, but wouldn't it die over at night because it's not being charged?

author: SL4P
author_rank: Super Contributor
timestamp: February 23, 2015, 12:03:35 am
content: Quote from: GabYoung92 on February 23, 2015, 12:01:45 amUse the static transfer switch to revert to mains if it's still available - if not you have a flat battery either way.

author: RJFreeman
author_rank: Regular Contributor
timestamp: February 23, 2015, 12:41:01 am
content: The nearest commercially available product I can think of is Grid interactive inverter, this would be effectively in parallel with the AC feed to your server and feeds power into the grid when sunlight is available.Oddly I am in a not dissimilar position to you and having had my UPS fail several months ago have been pondering setting up a dual 48V battery bank, charged from Solar (when available, still pondering the detail, but maybe run one bank off Solar, with the second bank charging from mains and then prioritise power from Solar with the other bank as backup? - this involves switching though, rather than usual dual DC feed via diodes and switching appreciable currents at 48V DC can be a challenge if you are not careful) and then feeding that into an inverter to run my server rack.but while I have a few ideas (maybe going for an open hardware/modular approach?) I have not had time to push this project along as I ahve been busy with other things....

author: SL4P
author_rank: Super Contributor
timestamp: February 23, 2015, 12:46:14 am
content: Just a side point for onlookers - which you have already appreciated:::OPTIONS:Run the load off asingleinverter and switch the DC - avoids the need to synchronise the mains and inverter outputs and alternate of large bangs.Use an ACtransfer switch- but make sure your inverter output is in phase with the mains - or similar large noises and flashes. Use a 'real transfer switch for minimal changeover 'transfer' time.

author: RJFreeman
author_rank: Regular Contributor
timestamp: February 23, 2015, 12:49:17 am
content: Quote from: RJFreeman on February 23, 2015, 12:41:01 amI forgot to point out, a Grid Interactive inverter needs to be installed by folk licensed to do such a thing and is NOT a DIY project.....

author: GabYoung92
author_rank: Regular Contributor
timestamp: February 23, 2015, 04:13:31 am
content: Quote from: RJFreeman on February 23, 2015, 12:49:17 amDon't worry, won't be wiring it. I do have a grid-tie here ready to go but it needs a 180V + input.I was looking for something to plug into a GPO (or have an IEC socket), have a GPO socket on the output and can accept a 12/24V panel as a secondary power source. Looks like it doesn't exist

author: TMM
author_rank: Frequent Contributor
timestamp: February 23, 2015, 04:32:46 am
content: Ghetto solution is to have two battery chargers / DC powersupplies - one mains powered and one solar powered. Have them diode connected to the battery bank - the batteries will charge from the higher voltage source so you have your solar charger supply a slightly higher voltage. Then just plug a DC to mains inverter into your battery bank and away you go.The disadvantage of using a system like this is that the mains will keep the batteries topped up when the sun isn't shining, so you don't use as much solar power as you could. A 'smart' system would allow the batteries to drop to a discharged state before the mains charger kicked in, while the solar charger charges them at every opportunity. You could simply drop the mains charger voltage (to say 10.5V for a 12V lead acid battery bank) to emulate this but it's not as kind on the batteries as having a system which can predict when it can expect solar charging and when it should just charge the batts to full voltage. I.e. you don't want to run your batts at 10.5V all night when there is zero chance of solar charging kicking in, so just charge them up to 13.5V until the morning.Another issue is efficiency - if you are only running on solar power for 5% of the day, your mains charging/inverting scheme needs to be more than 95% efficient to break even.

author: RJFreeman
author_rank: Regular Contributor
timestamp: February 23, 2015, 04:37:42 am
content: Quote from: GabYoung92 on February 23, 2015, 04:13:31 amThat's what I had been pondering, but haven't found anything yet....It did occur that something like a TAS5630 would happily run off 50V and could be used to drive a 36V transformer to bump up to 230V, In theory that would be 600W but you would probably want to de-rate it to some extent (and might need to abuse them to see how they like having a transformer as a load) then as I suggested, run a dual 48V battery pack, one from solar, and one from mains but that requires development and testing time.....