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Building my own solar power system

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Re: Building my own solar power system

#331

Post by K0balt »

vhanda wrote: post #252
arwineap wrote: post #245

Earlier quoted context omitted.

Naive question, why run inverters? Wouldn't it be more efficient to run direct DC appliances? We have a building on our farm without power and it'd be ideal to be able to charge batteries and run lights at night It seems to me that we would have to upsize batteries in order to make up for the loss in converting to AC

Not who you're asking. I really don't see why we're still using A/C inside our houses / apartments. I understand that the transmission loss is lower when sending A/C, so it makes sense, but then nearly every device in my house has their own AC to DC converter. Just have one AC-DC converter per building. I'd like the future to just be USB-C sockets in my house. We have USB-C PD 3.1 which supports up to 48v, I imagine…

A lot of appliances need >1kw.

This requires higher voltage and robust connectors.

That level of DC is quite dangerous compared to AC for many reasons.

Also, unless you want to have 60lb extension cords the size of bratwurst, you need to go high voltage. High voltage DC is its own kind of devil, and is something I would not want in my household except in very isolated, self contained places.

High voltage, high current DC is on yet another level of mortal threat, able to do cool tricks like making extensions cords burn from one end to the other like cartoon dynamite fuses. Also, absolutely the best for accidental electrocution, severe burns and flash blindness, and setting otherwise fire resistant structures thoroughly aflame.

Re: Building my own solar power system

#332

Post by kragen »

kragen wrote: post #137
detaro wrote: post #53

Earlier quoted context omitted.

Wind generators really scale with size though. Small ones rarely make sense

If the objective is to reduce the number of hours you're not self-sufficient for a given battery size, or reduce the size of your expensive batteries, even a couple hundred watts could make sense. https://www.amazon.com/NINILADY-Vertical-Generator-Controlle... is a 600-watt-peak wind generator, designed for 11m/s winds, for sale in the US for US$300, presumably much cheaper in countries that aren't descending into kl…

Correction: according to what I found in https://news.ycombinator.com/item?id=44056971, 50¢ per peak watt would not be a terrible, uncompetitive price if you were a utility company considering how to build a wind farm. In fact, it's significantly cheaper than the prices they actually pay for big windmills.

Re: Building my own solar power system

#333

Post by K0balt »

jedahan wrote: post #146
K0balt wrote: post #144

I’ve been running a solar microgrid on my coffee farm for the last 7years. We started with a few golf cart batteries and 4 panels, these days we’re powering 4 houses, 7 cabins, water extraction, treatment, and RO processing, campus-wide fiber network and switches, path lighting, security systems, and a small server rack. We’re running 6 inverters on our primary system in a three phase configuration, 35kw of panels an…

Would love a write up or links to resources for water extraction and treatment if you’d oblige.

There is a few more details, especially of the early days, on my extremely neglected and out of date blog https://vivavistadelmar.wordpress.com/blog/

Also, yeah, I know. Wordpress wasn’t a great choice even years ago when I set up the blog, but I was going to self host as a static site “soon” anyway and I needed to get started… almost good enough is the mortal enemy of adequate.

Re: Building my own solar power system

#334

Post by K0balt »

arwineap wrote: post #245
K0balt wrote: post #144

I’ve been running a solar microgrid on my coffee farm for the last 7years. We started with a few golf cart batteries and 4 panels, these days we’re powering 4 houses, 7 cabins, water extraction, treatment, and RO processing, campus-wide fiber network and switches, path lighting, security systems, and a small server rack. We’re running 6 inverters on our primary system in a three phase configuration, 35kw of panels an…

Naive question, why run inverters? Wouldn't it be more efficient to run direct DC appliances? We have a building on our farm without power and it'd be ideal to be able to charge batteries and run lights at night It seems to me that we would have to upsize batteries in order to make up for the loss in converting to AC

As a parallel answer, for small systems this can make sense, although in anything larger than a single small cabin or small boat it probably is borderline these days. Modern inverters are quite efficient, and DC distribution carries a lot of issues, and gets downright dangerous at higher voltages necessary for large appliances.

20 years or so ago I rebuilt a 60’ schooner, and even on that scale AC was by far the best choice. Just the wiring for a DC system was more expensive then double Refund inverters, and most of the appliances were actually less efficient, since they had their own inverters inside them (DC-DC converters). In all there just wasn’t any justification, and corrosion is another issue on boats, so we went all AC.

Re: Building my own solar power system

#335

Post by K0balt »

networkisfine wrote: post #243
K0balt wrote: post #144

I’ve been running a solar microgrid on my coffee farm for the last 7years. We started with a few golf cart batteries and 4 panels, these days we’re powering 4 houses, 7 cabins, water extraction, treatment, and RO processing, campus-wide fiber network and switches, path lighting, security systems, and a small server rack. We’re running 6 inverters on our primary system in a three phase configuration, 35kw of panels an…

Very interesting. I'm looking to do something very similar on a farm. Would you mind sharing some more design details? Questions that come to mind: What products are you using? Are you doing any AC-coupling between inverters? If not, are you just running your PV wires between buildings? Are you stepping up your AC voltages to 480v or so to cover greater distances with less loss? Thanks!

Running the inverters in parallel synchronized in a three phase configuration, 2 per phase, 224/130. Since the power plant is centrally located, our longest run is about 270m. It’s at the edge of what we can do with the cable we have buried, so if we need to extend or add significantly more capacity we will probably go up to 440v for that segment, with a substation at the PED4 utility hut. Better efficiency in step up/step down is one of the reasons we chose 3 phase power.

The panels are mostly centralized with each string being a home-run to the power plant but we are building out an additional 10KW on a rooftop about 200 yards away, so that will be 600VDC buried cable.

We are testing small ( panel-back attached )grid-tie inverters for supplemental power at point of use, but we will see how much we can add before it results in stability issues. It would be great to be able to put a panel or two wherever it’s handy and just tie each panel separately into the ac distribution.

Re: Building my own solar power system

#336

Post by jmb99 »

kalleboo wrote: post #140
jmb99 wrote: post #15

Earlier quoted context omitted.

My hard drives alone pull 200W idle and I don’t have that many. Cooling fans (in servers) pull 150W total most of the time but can be up to 300W. Each 10GbE NIC pulls ~40W. PoE switch gives ~30W to each of my APs, and uses ~80W itself, so there’s another 300W. All of my RAM pulls about 250W (admittedly there’s nearly 2TB of it in the rack, but still). Start adding up CPUs idle/average/max power and the numbers get wa…

40W for a 10GbE NIC sounds crazy, my internet router has a dual 10 GbE Intel NIC with one 10GBaseT SFP+ and one 10G DAC and the whole router only draws 24 W (Lenovo ThinkCentre Tiny) My whole “rack” draws about 120W total with: aforementioned router, Synology NAS with 4 drives, 2x10G+4x2.5G PoE switch powering a Ubiquiti AP, 16-port 1G switch, and a PowerBook 540c running AppleTalk routing

Late response I know, but copper 10GbE nics pull lots of power, especially the old X540 ones.

Re: Building my own solar power system

#337

Post by jmb99 »

xarope wrote: post #59
jmb99 wrote: post #15

Earlier quoted context omitted.

My hard drives alone pull 200W idle and I don’t have that many. Cooling fans (in servers) pull 150W total most of the time but can be up to 300W. Each 10GbE NIC pulls ~40W. PoE switch gives ~30W to each of my APs, and uses ~80W itself, so there’s another 300W. All of my RAM pulls about 250W (admittedly there’s nearly 2TB of it in the rack, but still). Start adding up CPUs idle/average/max power and the numbers get wa…

I'm curious, are you getting this with a kill-a-watt (or equivalent), or are you adding up wattage by specifications alone? (I do have an epyc with a bunch of memory and storage, but never bothered doing the math since my UPS claims to be able to run with the average load for 30+mins)

Measured at the UPS, which has 1W resolution. Confirmed its accuracy with an amp clamp on the circuit when running the UPS in pass-through mode. Efficiency is even worse most of the time since it’s a double-conversion (online) UPS that I normally run in full conversion mode - something like 80-85% efficiency overall, but because I fall back to generator power relatively frequently I just leave it there for convenience (in case I’m not home to switch it when the generator’s turned on).

Re: Building my own solar power system

#338

Post by looofooo0 »

epistasis wrote: post #302
looofooo0 wrote: post #35

Earlier quoted context omitted.

Not so easy to reduce the grid load all the time, needs a big battery for every night and for multiple dark days you still need the grid a lot.

Big batteries are actually very easy, and getting cheap enough that they account for a significant chunk of new grid assets when there are enough renewables. Take the Texas ERCOT market, which is the closest thing to a free electricity market that exists in the US. A huge chunk of new grid assets are batteries, becuase they are one of the most profitable things to install right now (see the map at the bottom of the p…

Ok what do you do after 5 darkdays? You will need the grid.

Re: Building my own solar power system

#339

Post by devilbunny »

ploxiln wrote: post #267
brewtide wrote: post #229

Earlier quoted context omitted.

Similar here in Maine under CMP. Something like 12.5 cents/Kwh, but with the delivery aspect factored in it's basically 28 cents/Kwh. I always assume when people on here are talking their 'rates', that they are usually NOT factoring in the delivery fee unless stated. But maybe some places are just really THAT cheap.

I don't know why anyone would not include the "delivery" fee, I think it really is that cheap in many places in the US. Here in NYC the "supply" charge is much less than half of the total bill. If I add up all the fees and surcharges and taxes etc, the total ends up around 35 cents / KWh, which I thought was rather high until I heard about California ...

I pay around 10 cents per kWh in the southern US; we have a nearby nuclear plant. We do have a base fee just for the meter, but no separate transmission fee. My in-laws in Texas have an open market for generation but pay transmission separately.
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