Author Topic: Supplemental Solar  (Read 1340 times)

russb

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Supplemental Solar
« on: December 21, 2017, 09:51:39 AM »
To preface this, I am just trying to get started with some more concrete thinking on an idea I've had for a while.

We live in an old farmhouse, built before electricity considerations. The electrical system has been upgraded over time, everything works well, but there's a conspicuous lack of outlets and ceiling fixtures. I'd like to rectify this, but I'd also like to go solar, at least partially. Cutting the electric bill and environmental impact of our usage down would be great.

I'd also like to not tie into the grid, ideally, although here in NJ there seem to be a lot of incentives for doing that. I want power when the grid is down, and just plain independence from the electric company.

My "plan" (scare quotes because so far it's really just something I've daydreamed about):

Initial setup:
1. We have lawn space with no trees blocking the southern exposure. Panels on the ground (roof peak is 32+ feet high, hate the idea of drilling into it, as well).
2. Put a second circuit panel in the basement, supplied entirely by the off-grid solar panels.
3. Initially, do not use battery storage. This would be a supplemental system that would expect sudden power outages.
4. Add several outlets to the house, tied into the new solar circuit panel. Mark outlets as being supplied by solar.

Later:
5. Add battery storage and more panels, if desired. Add the other necessary components as well.
6. Transition a couple of the electricity hogs (washer/dryer/dishwasher/water heater) and the light fixtures to the solar system, as the available power would allow.

I'd really never see the need to abandon the grid entirely, but a supplemental system that eventually transitions to supply 50+% of our power, maybe even powering a couple A/C units during the day, would be really nice.

My initial questions:

Is it technically feasible? Links to resources are welcomed.
Is it likely to be cost effective?
Is there likely to be insurmountable red tape and restrictions?
Is the initial plan sound, for leading to the later improvements?

And any other naysaying or encouragements you have would be appreciated. I've not done any specific research yet, just brainstorming. I have yet to find an example of someone who installed a system like this (off-grid, supplemental, battery-free system). There may be reasons for that.

ChpBstrd

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Re: Supplemental Solar
« Reply #1 on: December 21, 2017, 02:14:04 PM »
The challenge would be those energy hogs, such as the A/C and other appliances. These require a big burst of amps for a relatively short time, and you'd have to scale up your entire solar system to match their intermittent demands, wasting your solar production when appliances are not in use. Oh, and you'll sometimes be using multiple appliances at once, so scale it up again. As you can see, things get pricey fast, all due to those appliances.

Check to see if NJ is a "net metering" state where the electricity you put into the grid makes your meter run backwards. This is a more economical solution, though it leaves you connected to the grid.

Also, if you are rewiring anyway, you could dedicate/separate circuits to low-amperage purposes powered by your solar system and/or batteries. E.g. make all the (LED of course) lights in the house run on solar/batteries. This would leave you on the grid but also not cost tens of thousands to build. I'd expect the ROI to be much better than a full off-grid implementation.

I've also heard ideas about using relatively small solar arrays to power supplemental electric baseboard heaters or to run an extra heating element in your water heater - both high-payback but low-amperage applications requiring minimal investment and using inexpensive separate circuitry from the house/grid.

russb

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Re: Supplemental Solar
« Reply #2 on: December 21, 2017, 02:56:07 PM »
Yeah they do net metering here, which is probably why I see so many grid tied panels around me.

robartsd

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Re: Supplemental Solar
« Reply #3 on: December 21, 2017, 03:10:14 PM »
Solar really wouldn't work for much of anything without a battery or grid tie.

Dusty Dog Ranch

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Re: Supplemental Solar
« Reply #4 on: December 21, 2017, 03:12:13 PM »
Solar panels alone without a battery bank or a grid tie won't get you much if you are looking for power during a grid service interruption. The energy has to go somewhere and the panels don't generate anything at night or on very cloudy days.

ChpBstrd is correct that the energy hogs and other loads are crucial to consider. There is no point in trying to use solar to say, power an electric water heater, because the load it draws is so high. That's the reason I only vacuum on sunny days in the winter! Ah, the off-grid life.

I recommend going to Backwoods Solar's Learning Center to do some research. They are also extremely helpful over the phone. http://www.backwoodssolar.com/learning-center. You need to figure out what loads you want to run off the solar and then size your system accordingly.

Permitting varies by locality, but you will need the electrical inspector to sign off no matter what system you come up with. Especially if it's grid tie b/c of the risk to linepeople if your system backflows onto the grid after a power outage.

Personally I love being off-grid-yesterday it snowed like crazy and people were posting all about how their power was out. Not mine!


russb

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Re: Supplemental Solar
« Reply #5 on: December 21, 2017, 03:21:29 PM »
This is good advice so far, thanks guys. I guess it's probably not real useful to have an off-grid and battery free installation. Sounds like my initial effort should simply be a smaller set up including battery storage, that can be scaled up.

I may prototype a setup by putting in a panel or two to run an an outlet, and maybe a light, out by my shed/chicken coop.

Cadman

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Re: Supplemental Solar
« Reply #6 on: December 21, 2017, 04:16:09 PM »
I have a 10kW grid-tied system I designed and installed myself (really the only way to get the ROI back in a reasonable amount of time without rebates here) so I can offer a few pointers.

The minute you start looking at batteries for 'realistic' storage, the game is lost. You've then got ongoing maintenance, charge controller(s) and replacement costs to look forward to besides a number of technical limitations. The numbers never work out. If you were to try to use solar without any storage, not only do you have the problem others have mentioned about cloudy days or night, but voltage regulation becomes a problem, even on sunny days. If you were relying on a simple inverter, you'd have constant cycling.

When the going gets tough, an off-grid battery system can be workable (especially when there's no other option), but it means watching every Watt, ditching usual 'power hungry' electrical loads, and being deliberate and conscientious of your power use.

I did build a 12V system using cheap, readily available parts and a single deep cycle batt for my off grid garage, which I then equipped with LED lights, and even modified a garage door opener for 12V DC use, which was the original impetus. I'm on year 2 or 3 and it's been working well. But it might only see a few minutes of low current use a day, and gets all day to recharge.

The smart money with a photovoltaic system is to take advantage of the grid-tie and use the power company as your battery bank. I don't know if the Fed Credit was extended for 2018, but you might consider that. And there is at least one company out there making inverters that offer a fixed outlet you can plug into which is powered even if grid power is lost, but without storage, you're at the mercy of the sun at that instant.

BudgetSlasher

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Re: Supplemental Solar
« Reply #7 on: December 21, 2017, 04:35:39 PM »
I have a 10kW grid-tied system I designed and installed myself (really the only way to get the ROI back in a reasonable amount of time without rebates here) so I can offer a few pointers.

The minute you start looking at batteries for 'realistic' storage, the game is lost. You've then got ongoing maintenance, charge controller(s) and replacement costs to look forward to besides a number of technical limitations. The numbers never work out. If you were to try to use solar without any storage, not only do you have the problem others have mentioned about cloudy days or night, but voltage regulation becomes a problem, even on sunny days. If you were relying on a simple inverter, you'd have constant cycling.

When the going gets tough, an off-grid battery system can be workable (especially when there's no other option), but it means watching every Watt, ditching usual 'power hungry' electrical loads, and being deliberate and conscientious of your power use.

I did build a 12V system using cheap, readily available parts and a single deep cycle batt for my off grid garage, which I then equipped with LED lights, and even modified a garage door opener for 12V DC use, which was the original impetus. I'm on year 2 or 3 and it's been working well. But it might only see a few minutes of low current use a day, and gets all day to recharge.

The smart money with a photovoltaic system is to take advantage of the grid-tie and use the power company as your battery bank. I don't know if the Fed Credit was extended for 2018, but you might consider that. And there is at least one company out there making inverters that offer a fixed outlet you can plug into which is powered even if grid power is lost, but without storage, you're at the mercy of the sun at that instant.

Cadman. I would love to hear more about your setup; would you happen to have any pictures? I have been day dreaming a 6-7.6 kw ground mount grid tied system; I might do a 10kw inverter for future expansion and/or transitioning some of our heating needs or our next car to excess electric.

Did you go with a string inverter, micro-inverters or DC optimizers? Is yours a ground mount or roof mounted? Do you have any recommendations on site assessment tools in terms of seasonal shading and compensating in the array size.

It will probably remain the thing of day dreams until 2019; I have to finish a kitchen remodel and I would like to insulate the basement walls in 2018, but I would like to get in under the 30% federal credit. I estimate that between the basement and solar I can knock around 50% off of our utilities.
 

robartsd

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Re: Supplemental Solar
« Reply #8 on: December 22, 2017, 11:47:43 AM »
If I were designing the electrical system from scratch today, I'd have a DC microgrid in every home. 48 VDC wiring could power LED lighting, electronics, and small appliances with reasonable line loss. Major appliances would still use AC utility power. The simplest setup would simply include a single, efficient AC to DC converter powering the DC microgrid (this could be much more efficient than the individual small power converters we currently plug in for each electronic device). A battery could be added for uninterupted service to the DC circuits during minor utility outages. Then a suplemental solar system could start off just charging the DC battery to power these loads. Inverters wouldn't be needed until the solar system was large enough to supply more than the DC loads. Unfortunately such a system is not very practical today because there is no de-facto standard for producing consumer electronics that connect to such a migrogrid, so all consumer products are designed to connect to the AC outlets, 12 VDC car outlets, or 5 VDC USB outlets.

Cadman

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Re: Supplemental Solar
« Reply #9 on: December 27, 2017, 11:28:05 AM »
Hey BudgetSlasher,

Our location made ground-mount a no-brainer. Besides no penetrations in the roof, ground mount operates on a slightly less stringent set of installation rules. Plus I can clear snow build up and perform any maintenance without too much trouble.

I had initially considered several different solar 'packages' but ultimately decided to design my own system such that I could mix and match to get something I wanted that would perform well and was affordable. (there are ALWAYS panel closeout deals going on) I ended up with a three series string arrangement in parallel, 'non-grounded' with an SMA 10kw inverter. Having an open field in front of the panels, there was no concern about shading, so no need for micro-inverters. I'm sure some have had good luck with them, but to me they introduce one more failure point in the system x number of panels installed.

The one thing I'm glad I paid a little extra for was the SMA ethernet connectivity board. I can monitor KW output in real time from my phone app or work computer and aggregate the data to determine how much was used vs sold back to the power company. Also handy if the system drops offline for some reason as you might not have a tendency to check your physical inverter status every day.

The racking is Ironridge and was a breeze to put together, and I sourced the 3" galvanized pipe locally and cut the 21' lengths with a cheap chopsaw. Heavy stuff, but it all worked out.

One thing to consider is how much longer fed and state credits might be available; they can make a big impact on a project this size.

Fishindude

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Re: Supplemental Solar
« Reply #10 on: December 27, 2017, 01:24:22 PM »
I think you are smart to go ground mounted.   Roof mounted panels will eventually be a pain in the rear.  Why put unnecessary holes in your roof?  And what happens when it's time for a re-roof?
Tied into the grid is the way to go.   Like someone else said ... use the power company as your battery bank.

Syonyk

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Re: Supplemental Solar
« Reply #11 on: December 28, 2017, 06:31:46 PM »
I'm pretty familiar with solar - I don't (yet) have a system on my house, but I do make my living in a solar powered office (or, as more common in the winter, generator powered).

Off grid power, or semi-off-grid power, is painfully expensive.  Comically, absurdly, insanely expensive.  It's useful if you're unable to get grid power for under about $50k, it's useful if you're a goof who plays with this stuff for fun to get hands on experience, and it's useful if you value standby capability for your house/projects (a friend of mine has a pretty hefty inverter and an awfully large battery bank to run his lab equipment, because if his vacuum pumps shut down, he loses quite a bit of work).

That said, let's dive in!

We live in an old farmhouse, built before electricity considerations. The electrical system has been upgraded over time, everything works well, but there's a conspicuous lack of outlets and ceiling fixtures. I'd like to rectify this, but I'd also like to go solar, at least partially. Cutting the electric bill and environmental impact of our usage down would be great.

Split your projects.  Upgrading wiring and outlet count should have very little to with solar in a practical setup.

The only way you'll have an actual benefit for your power bill is a grid tied solar setup.  The same is true for environmental - off grid power is really quite dirty if you trace back to the batteries, and you have a generator... small generators are not very efficient.

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I'd also like to not tie into the grid, ideally, although here in NJ there seem to be a lot of incentives for doing that. I want power when the grid is down, and just plain independence from the electric company.

How important are the various aspects of the project to you?

"Independence from the electric company" is a pipe dream unless you're willing to pay 3-4x the price per kWh you pay now, perpetually.  You'll need a hefty generator in the winter, and I joke with people that "off grid" is an ancient Indian term for "likes generator maintenance."

If you put any sort of inverter on your home's power wiring, you're going to need to have grid tie agreements in place with your utility, and have to meet code, etc.  The wire cost alone to run a separate system is cost prohibitive.

You can design a solar power system that gives you limited grid independence (closer to a whole house UPS) that's still grid tied, but if you start thinking about this, you can forget cost savings.  There's no way to do a setup that runs grid-down cheaply enough to "pay off" in most areas - around the time you catch up, the battery bank is toast and needs replacement.  Yes, I've read the claims about lithium, and no, I don't think most of them will be met in home power systems.

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2. Put a second circuit panel in the basement, supplied entirely by the off-grid solar panels.
3. Initially, do not use battery storage. This would be a supplemental system that would expect sudden power outages.
4. Add several outlets to the house, tied into the new solar circuit panel. Mark outlets as being supplied by solar.

You can't make this work for any useful value of work.  Solar panels are a rather weird power source, and the only way you can run with no batteries is to run far, far below the rated power of the array.  Say, pulling 1kW off a 6-10kW solar array.  Some of the string inverters have this feature, but even then, power is unreliable.  Cloud?  Whoops.  It drops.  I've got a long blog post on this exact issue coming up, because it's complicated to explain why it doesn't work, but it doesn't.

So you're not utilizing your panels at all, practically.  They're pretty black plates sitting in the sun running, sometimes, at a tiny fraction of rated output.

There are very few inverters that will tolerate this, and I assume you're not planning to build your own power conversion equipment for this project.

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5. Add battery storage and more panels, if desired. Add the other necessary components as well.
6. Transition a couple of the electricity hogs (washer/dryer/dishwasher/water heater) and the light fixtures to the solar system, as the available power would allow.

Going from a direct panel powered inverter to a battery system typically involves totally different components.  You'll generally have a 48V battery bank (lead acid or lithium iron phosphate) for a home sized system, and will need the charge controllers and inverters for that, instead of the previous inverter.

How are you planning to tie light fixtures and such into this obscenely expensive system?  Remember, you can't touch your home's existing wiring without net metering agreements.

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I'd really never see the need to abandon the grid entirely, but a supplemental system that eventually transitions to supply 50+% of our power, maybe even powering a couple A/C units during the day, would be really nice.

You... seem to operate under the belief that this system will be cheaper or greener.  :)  It won't be. Not by a long shot.

Just buy community solar, or install a grid tie system.

For backup power, you want a generator and transfer switch.  Propane is a good option for a long term storage generator.

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Is it technically feasible? Links to resources are welcomed.

See above.  It's on the edge of technically feasible, in that I could put together systems that would do what you request, but... well, see below.

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Is it likely to be cost effective?

No.  Emphatically, no.  If you can get off grid power down to about 4x grid power, you've got an efficient system.

My current cost per kWh on my system is... oh, $1.50/kWh?  That'll go down, and I think I ballparked around $0.40/kWh by the time the battery pack needs replacing on my office.

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Is there likely to be insurmountable red tape and restrictions?

Yes, though you could avoid that if you had totally separate power wiring for the parts you run with the solar setup.  You can't do something like shut a breaker down, though - it would need to be totally separate.  Have you priced copper wire lately?

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Is the initial plan sound, for leading to the later improvements?

This is a bad way to achieve... whatever it is you want to do, unless the goal is to spend tens of thousands of dollars for hundreds of dollars of power.

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And any other naysaying or encouragements you have would be appreciated. I've not done any specific research yet, just brainstorming. I have yet to find an example of someone who installed a system like this (off-grid, supplemental, battery-free system). There may be reasons for that.

Quite.  That's because it's not technically feasible in a useful manner.  You can go battery free with grid tied, you can go off grid with batteries, but what you can do off grid and without batteries is so limited as to be nearly useless.

=============

Alright, that idea shot down, I'll give you an idea as to the feasible options out there.

In general, as someone else notes, the second you say "Battery," you've lost cost effectiveness on the system, at least at home scale.

If you want to save money with solar panels, and squint a little bit at being "green," go with a grid tied system with microinverters or string inverters.  That's about the only way you're going to actually save money.

If you want backup power, while you're doing that project, install a good transfer switch and a backup generator.  If you have natural gas, running it off that is a good idea (there's usually pressure in the lines for a while during a power outage), otherwise I'd suggest propane.  That's more expensive than gasoline, but it stores better and doesn't crud up the oil like gas does in a generator.  Five year old propane works fine.  Five year old gasoline is sort of a thick gel... it doesn't burn or flow and makes a mess of anything it's in.

Now, if you've abandoned the idea of saving money but really want reliable power, you can do a battery backed system.  There are a few ways to do this (AC coupled or DC coupled), but if you want high reliability power, you'll probably need to go with a DC coupled system.  This involves the panels running through charge controllers into the batteries, and an inverter that runs from the batteries.  You can set things up so you can sell to the grid this way if you have excess, but things can also run with the grid down indefinitely (or, at least, as long as you can charge things - solar panels in dark clouds are worthless).  The Outback Radian series inverters are a solid option for this, though there aren't many options because not many people want to do this.  You'll still want a backup generator with this setup.  But you can run most of the house post-inverter.  This is what I plan on doing.  I'll do most of the work myself, but it's still not going to beat grid power for operating costs.  It will, however, give me extended grid down capabilities and a nice batch of hardware to work with.

Hopefully that clarifies some of the issues.  I've got a few thousand words in progress talking about this exact issue, but that post isn't quite done.  However, https://arstechnica.com/civis/viewtopic.php?p=34054407#p34054407 has my first draft of that, which might be useful.
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boarder42

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Re: Supplemental Solar
« Reply #12 on: December 28, 2017, 07:18:02 PM »
Glad @Syonyk chimed in.

I think we're only 10 years or so away from solar and battery hitting the exponential ramp and around 2030 we won't even really be having this conversation it will revolve more around how to install these efficiently and cost effectively. Bc the math will make sense.  Communities will become microgrids large tlines will be over grown with vegetation but now we're talking 40 years into the future if solar is even the solution at that point.

But right now you have to want a fun science experiment to go off grid. Or live on a coast with high power costs and install a grid tied system and eek out some gains.

Syonyk

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Re: Supplemental Solar
« Reply #13 on: December 28, 2017, 07:47:39 PM »
Glad @Syonyk chimed in.

No problem.  I know my way around this stuff decently, and am one of relatively few people around with an actual off grid power system that talks about it on the internet a lot.

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I think we're only 10 years or so away from solar and battery hitting the exponential ramp and around 2030 we won't even really be having this conversation it will revolve more around how to install these efficiently and cost effectively. Bc the math will make sense.  Communities will become microgrids large tlines will be over grown with vegetation but now we're talking 40 years into the future if solar is even the solution at that point.

I disagree quite strongly.  Hyper-local power systems (even community scale) don't work unless you're willing to accept relatively long periods of dark and cold - or, on the flip side, a lot of generator use.  Small generators are really inefficient (my Kipor might manage 15% thermal-to-electrical, though it's an open item on my list to test it).  Community sized diesels can probably manage 35%, maybe a bit larger.  And large commercial combined cycle plants are running north of 60%.

You simply cannot build a solar/wind system that will keep a community in power cost effectively.  Even with magical battery ramping.  You need so much capacity to cover relatively few days of the year, especially if you're heating with electricity in some way or another.

I've got ~3kW of panels hung for my office.  I mistakenly believed this would let me power through winter via the miracle of overpaneling - it doesn't.  Idle draw in my office (60W 24/7 for the inverter, radios, etc) is about 1.5kWh/day, active draw with me in there is 3-4kWh/day.  That's with all thermals done on propane.  If I want to heat on electrons, add another few kWh/day, at least.  Call it 6000-8000kWh/day for heating on electrons.  A bad day for solar with dark clouds is 200Wh.  Not even remotely close.  If I wanted to run without a generator, I'd need a 50-70kWh battery bank, but I'd only use a few kWh out of it the rest of the year, because I have plenty of sun.  So most of that capacity (battery manufacturing isn't particularly environmentally friendly) is slowly wearing out from calendar time, without getting used in cycle life.  And that's stupid-expensive as well.

I can't heat on electric in the winter.  Even with all the panels I have, I struggle along to make my power demands without generator for about a month out of the year, and I run my generator for at least a week of that month (a few hours a day - I'm about 6 gallons of gas into the winter so far).

Oh, and wind?  An inversion ranges from "dead calm" to about "2 knots."  There's no wind to speak of for many of those days.

I simply don't see what you're proposing as being at all feasible.  The only way to have reliable power without individual backup generators is a power grid, and I am all for things that keep our power grid operational.  I intend to work with my power company to make sure I have the newest spec inverter firmware when I get stuff installed so I can at least contribute somewhat to grid stability with my setup, but I recognize that a grid tied setup is basically pushing the costs onto other users of the power grid while I reap the benefits.  I can write an awful lot on grid stability issues, but that's probably for another thread.  Suffice it to say, it's not simple, and it's definitely not a solved problem.  However, industrial solar is much more useful because you can operate it such that you don't have the awful transients of a typical rooftop system.

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But right now you have to want a fun science experiment to go off grid. Or live on a coast with high power costs and install a grid tied system and eek out some gains.

Grid tied systems without battery backup make financial sense a lot of places, though at the cost of other grid users and, I think, at the cost of the long term maintenance of the grid.

Off grid makes sense if you're far beyond the reach of the power grid or, as you note, up for a fun challenge.
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boarder42

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Re: Supplemental Solar
« Reply #14 on: December 28, 2017, 07:57:38 PM »
I disagree with your take on batteries. I think they will get small enough and cheap enough we can store massive amounts of energy efficiently.

And yes currently grid tied is largely supplemented at the expense of the power company and other users. I don't think this will be the case much longer net metering is not fair as you're not paying for the infrastructure that supports you when you have extra power to give back or need power in the depths of winter.

Syonyk

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Re: Supplemental Solar
« Reply #15 on: December 28, 2017, 09:52:08 PM »
I disagree with your take on batteries. I think they will get small enough and cheap enough we can store massive amounts of energy efficiently.

At an individual house or community scale, you're still proposing a massive amount of battery cycled only a few times a year, or small (inefficient) backup generators scattered around.

My house (modern energy star, heat pump, pure electric everything) uses 60-80kWh/day in the winter.  To store a week's worth of energy use, I'm looking at a 500kWh pack.  Even at $100/kWh, that's $50k in battery costs alone, for a pack that is unlikely to last past about 15 years (regardless of technology).  That pack buys me, at $0.12/kWh, 416MWh of energy from the grid.  My house uses about 15MWh/yr (that'll go up a bit with an electric car), so that $50k buys me... uh, 27 years of energy.  For a 15 year battery pack.  Not counting solar panels/charge controllers/etc.

The math doesn't work, even if you accept that batteries keep getting cheaper.  I can go with a smaller pack and cycle it better, but I won't make it through a winter week without charging.  Plus, even with that size pack, I'd need a truly massive solar array to charge it on winter clouds.  Meanwhile, in the summer, I'd be able to run decorative arc welders on the surplus of energy I had with nowhere to put it.

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And yes currently grid tied is largely supplemented at the expense of the power company and other users. I don't think this will be the case much longer net metering is not fair as you're not paying for the infrastructure that supports you when you have extra power to give back or need power in the depths of winter.

Correct.  Net metering relies on a quirk of residential rate pricing, and would look a lot worse on an industrial rate schedule.  Me pushing 10kW into the grid is still using the grid, even if it's going to my neighbors.  It's not "free" in any meaningful sense of the word, it's just that nobody is paying for the grid maintenance on that chunk of power.  On top of the horror show that residential inverters tend to be (obscene ramp rates, and empty VARs injected into the grid, plus the bulk of the ones installed are really eager to trip off for frequency or voltage excursions).  Newer specs (the -SA stuff) are better, but they still won't run a stable grid on their own.

And, even with batteries, it simply doesn't make sense for most areas.

I'm a big fan of industrial scale solar/wind, preferably paired with batteries, but that's utility scale and utility owned equipment, not individual rooftop solar.  Spreading the source over a large area helps a lot.

But I work within my own energy budget, for the most part, and I'd need a ton more battery (given that I run flooded lead acid, almost literally) to survive through the winter without generator use, and that's with propane providing my thermals.

===========

Now, if you insisted on doing hyper-local energy grids, you could do it.  But it would involve much more awareness of the weather, heating on biomass (or fossil fuel), and, in a lot of areas, mostly shutting down for the depths of winter.  We know you can do it, because people lived like that for an awful long while before we had reliable power grids stuffed everywhere.  But I don't get the impression too many people talking about solar and wind as the renewable future are really envisioning a return the time when December and January were pretty much cold, dark, and shut in months because you didn't have the energy to go anywhere, and it wasn't like someone had the energy to clear the roads anyway.
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robartsd

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Re: Supplemental Solar
« Reply #16 on: December 29, 2017, 09:18:31 AM »
I think boarder42 is overly optimistic about battery technology.

NOVA had a good program on battery technology earlier this year. It did not give me hope that we will ever see batteries signficantly more efficeint or energy dense than current lithium batteries (though there is hope for making them safer). For an off grid home, the batteries designed to be inexpensive and non-toxic featured in the show may bring costs down to close to grid system costs if you have the space for the battery bank (no better than current deep cycle lead acid batteries for energy density).

Syonyk

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Re: Supplemental Solar
« Reply #17 on: December 29, 2017, 02:12:57 PM »
I think boarder42 is overly optimistic about battery technology.

I run across that a lot.  I assume a lot of it comes from, "We can't maintain our current power system availability on renewables without massive revolutions in energy storage, therefore we will see massive revolutions in energy storage."  Not considering that renewable energy and the laws of energy storage chemistry/physics are under no obligation to give us what we assert we want.

We can live perfectly fine within the "energy of the week," but it does tend to involve not using electricity for heat.  And accepting that some weeks just aren't going to involve running much of anything in the way of compute/communications/lighting.

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NOVA had a good program on battery technology earlier this year. It did not give me hope that we will ever see batteries signficantly more efficeint or energy dense than current lithium batteries (though there is hope for making them safer).

I expect we'll continue to see some incremental improvements in energy density, and there's some promising work on the way with regards to metallic lithium anodes (and making those actually work for long numbers of cycles), but it's not anything like an order of magnitude improvement.  And many of those energy density improvements have an impact on cycle life or calendar life.  Plus the various metals involved in the battery production - don't look too closely at cobalt use.

We might eventually see lithium-sulfur cells, but they've been trying to break out of the labs for years now, and aren't much closer than they were.  They've got some niche use cases, but the volumetric density is really bad on them, so I don't expect they'll be particularly popular for many applications.

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For an off grid home, the batteries designed to be inexpensive and non-toxic featured in the show may bring costs down to close to grid system costs if you have the space for the battery bank (no better than current deep cycle lead acid batteries for energy density).

Which technologies were they talking about?  Salt water batteries are often listed as the future for off grid storage, but seem to have trouble actually selling enough of them for a company to stay in business.  The various lithium packs show promise, but don't have any actual track record, and the most famous of them isn't for sale in any useful manner.  Lithium iron phosphate is a good option, though an awful lot of people are having trouble getting rated calendar or cycle life out of them.

I'm actually pretty excited by some of the developments in lead acid.  There's been a lot of work recently on various lead-carbon (or "carbon enhanced lead acid") combinations for the plates that resolve or significantly mitigate the main problem with lead acid, which is plate sulfation at partial state of charge (rather, the hard sulfation that doesn't break up - soft sulfation is literally how the chemistry works).  There's been a lot of progress in making it so a lead acid battery doesn't require regular full charges (or can tolerate infrequent full charges), which means they can run partial state of charge for long periods.  They're more efficient there (close to 100% Coulombic efficiency - not round trip power efficiency, but better than their efficiency in the absorb stage), and if you don't have to fully charge them as often, they're better suited to handling winter.  I've been more or less gambling that Trojan's Smart Carbon stuff works as advertised and that I can run my cells PSOC for a week or two at a time.  It saves generator time/wear/fuel, and supposedly works.  I'll see.  If I kill them early from sulfation, I'll know for sure... but they get pretty solidly charged the other 10 months of the year.

All that said, for 8-10 months of the year, lead acid is just fine for off grid power.  It likes to sit fully charged for long periods, and with solar, you'll do that most of the year (I've got something comical like 12-13 good sun hours during the summer).  Lithium chemistries do not like being fully charged, so you should really back off the charge state on them during the summer or you'll wear them out quickly.  But lead acid isn't going to store a month of power for reasonable costs, and neither is anything else we have around or that's floating around the labs I'm aware of.

... but this is getting pretty far off topic.
My random project blog - ebikes, DIY, fans, and more: http://syonyk.blogspot.com

robartsd

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Re: Supplemental Solar
« Reply #18 on: December 29, 2017, 09:01:13 PM »
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For an off grid home, the batteries designed to be inexpensive and non-toxic featured in the show may bring costs down to close to grid system costs if you have the space for the battery bank (no better than current deep cycle lead acid batteries for energy density).

Which technologies were they talking about?  Salt water batteries are often listed as the future for off grid storage, but seem to have trouble actually selling enough of them for a company to stay in business.
Yes, it was a salt water battery featured. I just looked it up: the company was featured on NOVA in February, filed chapter 11 bankruptcy in March, emerged from bankruptcy in July backed by new capital, and announced that they would return to the market in October (target date April 2018). We'll see how this round goes!

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Re: Supplemental Solar
« Reply #19 on: December 29, 2017, 09:31:43 PM »
Yes, it was a salt water battery featured. I just looked it up: the company was featured on NOVA in February, filed chapter 11 bankruptcy in March, emerged from bankruptcy in July backed by new capital, and announced that they would return to the market in October (target date April 2018). We'll see how this round goes!

Yeah, thought so.

You'll excuse me for not viewing a company that can't sell enough of their "revolutionary new battery" to stay afloat as the future of energy storage.

You can't store them outside because they'll freeze (charged lead acid doesn't freeze until -90F, and you can drain it pretty far before you have to worry about freezing point), and the peak power per cell is really low.  A lead acid (or lithium) bank doesn't complain particularly much about having to source a high current startup surge for a compressor motor, but I don't think those will do it unless you seriously overbuild the capacity or have a very large system.

I've looked at them, and they seem high on hype, low on execution.
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BudgetSlasher

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Re: Supplemental Solar
« Reply #20 on: January 01, 2018, 09:37:23 AM »
Thanks for your responses, would you happen to have any pictures of the array (more of an inspiration thing than any specific component)

Hey BudgetSlasher,

Our location made ground-mount a no-brainer. Besides no penetrations in the roof, ground mount operates on a slightly less stringent set of installation rules. Plus I can clear snow build up and perform any maintenance without too much trouble.

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These are all the reason that lead me toward a ground mount, plus better orientation and the cost of re-roofing our old, but otherwise fine, roof.

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I had initially considered several different solar 'packages' but ultimately decided to design my own system such that I could mix and match to get something I wanted that would perform well and was affordable. (there are ALWAYS panel closeout deals going on) I ended up with a three series string arrangement in parallel, 'non-grounded' with an SMA 10kw inverter. Having an open field in front of the panels, there was no concern about shading, so no need for micro-inverters. I'm sure some have had good luck with them, but to me they introduce one more failure point in the system x number of panels installed.

I'd love to be able to do string, but in reality my property does not afford a ideal spot for year round unshaded exposure.

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The one thing I'm glad I paid a little extra for was the SMA ethernet connectivity board. I can monitor KW output in real time from my phone app or work computer and aggregate the data to determine how much was used vs sold back to the power company. Also handy if the system drops offline for some reason as you might not have a tendency to check your physical inverter status every day.

Good point. I will keep ease of reviewing in mind as I plan.

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The racking is Ironridge and was a breeze to put together, and I sourced the 3" galvanized pipe locally and cut the 21' lengths with a cheap chopsaw. Heavy stuff, but it all worked out.

did you set it in concrete piers or ballast mount? And how did actual purchase prices compare with the cost sheets that you see online before you attempt to buy? I've read multiple people in the planning phases complain about the cost of the racking, only to be told the actual purchase price is less. But, I have yet to figure out how much less.

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One thing to consider is how much longer fed and state credits might be available; they can make a big impact on a project this size.

All I have is the federal incentives, there are no state, our changing this month from net metering to something more complicated rule. (I mostly understand it, but just don't feel like diving into it here).

If you wouldn't mind can you share your $/watt either before incentives or after the federal 30% credit? I don't need perfect math, I just want to be able to budget correctly and there are some many little pieces to think about.

Cadman

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Re: Supplemental Solar
« Reply #21 on: January 01, 2018, 12:17:31 PM »
Thanks for your responses, would you happen to have any pictures of the array (more of an inspiration thing than any specific component)

I'll shoot ya a PM....