Off grid new house build.

[Hedges]

One of those Honda models is shown as 1kW, pretty ideal for the application.
I looked up natural gas/propane CHP (high temperature reformer) and while the concept seems great, actual efficiency numbers for an available product seemed no higher than ICE.

Wood-fired CHP (e.g. Sterling generator) could also be interesting.

Seen a price for the Honda?

It is sine wave inverter output. Have to be careful what inverter system you feed this into - only 8A at 120V available, so want something like Sunny Island that will pick up all excess load when using this generator as AC source. Probably easier to feed it through a battery charger, DC coupled.

 

[JayArr]

I don't know, maybe shut the main generator down and have a small unit that handles absorption? Sounds pretty awful, but would also give you a backup for times the main generator is down.

That's an interesting idea. I want the big generator up the hill at the utility building so we don't have to look at it or hear it. A small generac running off propane just beside the house could be a good answer for the absorbtion cycle in the darker months.

Edit:

Nov, Dec, Jan could be good months to go travelling to sunnier locations, maybe if we aren't in the thouse living there it could be put into a hibernation mode where the power required is low enough that panels are enough to keep the batteries charged.

 

[JayArr]

FLA batteries and ICE generator may be a poor match, if generator has to keep operating for 2 hours absorption. Better generator for bulk, PV for absorption middle of the day.

This has been in the back of my mind for a couple of days.

Does this mean I get around this by scheduling my generator?

If I ran my generator in the morning, say around 9:00AM and I charged the batteries up to 70% or 80% and then shut if off and let the PV top them up? That way the genny isn't running at low load and the cost can remain low. I'd have a full set of batteries by evening to last until morning.

 

[Hedges]

Yes, that approach should help.

 

[JayArr]

I've replaced the firewall and the PBX with small boxes and shaved 600W off my consumption.

Next up is to replace two servers running 8 SCSi drives down to one server running four SSDs.

New Question: Are there roof mount racking/brackets that allow the angle of the panels to be adjusted for seasonal efficiency?

 

[Hedges]

There are some struts that can be adjusted. I think tilt in same direction as roof slope could work, but tilting in other direction would tend to shade each other, unless spaced apart.

Some small ground mounts, especially home built, a seasonal tilt could be practical.
But for most installations, the low price of PV panels these days makes it more practical to just install a larger fixed array, e.g. for the roof just cover the whole face of the roof. I like multiple string of different orientation, wired in parallel.

 

[Rednecktek]

Next up is to replace two servers running 8 SCSi drives down to one server running four SSDs.

That'll make a difference for sure! You're almost gonna miss the whine thought.

 

[JayArr]

If I cover the entire roof I've got room for 150 panels. (2600 sq Ft)

At 250W/panel (what I can afford) Thats 37.5kW optimum.

Using numbers from the PVWatt site I calculate that I am still short in Nov/Dec/Jan and will need to run the genny and spend $460/year on diesel.

It also shows that I will produce three times as much as I need in the summer.

So maybe the solution isn't that I need to adjust them, perhaps I just need a better static angle. One that produces enough power in the three winter months at the expense of the extra power in the summer. It may take some convincing of the wife, she would like them to all be flat to the roof. The idea of not having to run a genny may be enough to change her mind.

If I get the angle right maybe I could even reduce the number of panels required.

Can anyone point me to the math that does the same thing as PVWatt? I want to add the "panel tilt" to my spreadsheet so I don't have to go through the whole PVWatt procedure each time.

 

[DIYrich]

New Question: Are there roof mount racking/brackets that allow the angle of the panels to be adjusted for seasonal efficiency?

Do you really want to climb on the roof twice a year? There are ground mount systems to do that. The conventional wisdom is: cheaper and easier to add a few extra panels to make up for the lost production in winter.

 

[Ampster]

If I get the angle right maybe I could even reduce the number of panels required.

in addition different orientations could spread out your production over a greater part of the day. That might not be enough to make enough winter production and it would also depend on how many charge controllers you have. Unless you have micros individual MPPT are easier than paralleling strings of different orientations.

At 250W/panel (what I can afford) Thats 37.5kW optimum.

Is that based on cost per Watt? Don't forget that smaller panels means more racking and fastening per Watt installed. If you went with 400 Watt panels that would only be 100 versus the 150 you calculated to get 37.5 kWs in panels.

 

[JayArr]

It's sort of based on $15000 budget for panels and covering the whole 2600 sqft roof. It's a very rough estimate based on used panels. When I looked at new the prices soared for the amount of KW I need in the array.

I'd prefer to climb my roof twice a year to having a huge solar panel array on my lawn.

 

[EastTexCowboy]

It's sort of based on $15000 budget for panels and covering the whole 2600 sqft roof. It's a very rough estimate based on used panels. When I looked at new the prices soared for the amount of KW I need in the array.

I'd prefer to climb my roof twice a year to having a huge solar panel array on my lawn.

150 panels in 2600 sf is going to be tight. You're going to need some access space every other row, especially if you're going to be changing the tilt twice a year.

I have mine on a nearly flat shop roof and the production doesn't really change that much in winter during peak hours. Just much less peak hours. Of course that also depends on your latitude.

 

[Ampster]

Of course that also depends on your latitude.

The OP is in British Columbia which starts at Latitude 49 and goes up from there. Even a optimum summer tilt would be at least 45 degrees from horizontal so depending on how far North he is, it could be even steeper. In summer the days are longer but his real needs will be in winter when the days are shorter.

 

[Ampster]

It's sort of based on $15000 budget for panels

That is $0.40 per Watt. Does that include racking? My estimate for plain non tilt racking is about $0.16 per Watt. I don't know the market in your area but I bought four new 400 Watt panels for $0.64 per Watt and at the quantity you are talking about you should be able to get a reasonable discount. At 20 per pallet you are talking at least five pallets or more.

 

[JayArr]

Hi Ampster

That is the budget just for the panels, I have $2000 for hardware, $2500 for charge controllers and $5000 for installation.

Total budget would be $0.65 per Watt installed.

Am I dreaming?

 

[Ampster]

Am I dreaming?

It may all depend on resources in your area. If the hardware quote includes racking you are close to the number that I guessed at. I do not see a budget for inverters and some of those All In Ones include charge controllers so that $2,500 could go toward inverter{s} and charge controllers but is not enough for both or an All In One.
Another thought about solar panels if you are buying used, depending on charge controllers or inverters there may be an advantage to try and use all the same panels to make string sizing easier. Or phase the install based on the string sizes dictated by your charge controllers and the minimum size system you want to start with.

 

[JayArr]

I've got other amounts for the inverters, I want the charge controllers separate so they charge the batteries directly.

Here are my rough numbers for now:




I'm building this house new from scratch so I've got every opportunity to run the wires at the rough in stage rather than trying to retrofit a house later. I hope that saves me some $$.

 

[Hedges]

FLA - Today, some LiFePO4 cost less to purchase than lead-acid.
Also expected to last longer, unless battery bank is oversized for 3 days autonomy.

$2500 worth of charge controllers seems low for 37kW. Unless they are overpaneled to about 200% of rating, for more production on poor days.

$10,000 for 2x 5kW inverters is retail for Sunny Island (which I use), but there are still deals for about half that price.
What brand/model are you planning on?

10kW generator - maybe to entirely carry full load. Is that necessary, or could it be smaller with inverters charging and inverting to limit draw?

 

[JayArr]

I want to stick with FLA. Reasons explained earlier in thread.

I would like Schneider inverters if I can afford them, I'm very familiar with repairing Trace and Xantrex so Schneider seems like the natural choice.

I could get away with a smaller Genny and I'll buy that used from Craigslist or Marketplace so I'll get what I can get. I'm mechanically inclined so I can often buy whatever I need in a non-functional state and then take it home and repair it. This saves me a ton of money and then I know it inside out so I can maintain it forever. I'd like 10kW just so that it will quickly and efficiently charge the batteries in the dark months. 5kW seems kind of small for a house (I have a 4kW genny on my travel trailer).

 

[Hedges]

Since I use SMA, I would use 2x SI 6048US, 12kW to 24kW of earlier model Sunny Boy (5000US ... 8000US), balance of PV panels on Midnight charge controllers. Actually,, for off-grid, I would consider 3-phase 120/208Y.
If PV panels were of a couple orientations, 37kW of panels would peak around 24kW, so up to 100% could be AC coupled, but for all output to go to battery, half AC coupled and half DC coupled since 2x SI can charge about 12kW.

With some AC coupled, your loads would be powered PV direct, giving battery inverters a rest.

Schneider should be able to do the same thing, for models that support AC coupling.


4x SI https://www.ebay.com/itm/295247353891

2x SI & Midnight Classic 250 (the 150V model would handle more watts) https://www.ebay.com/itm/304667704930

SB (11kW model 240V only, not 208V) https://www.ebay.com/itm/125963032554


What do you think of Kubota? There should be many near-new ones from DC Solar trailers.

Here's an older 6.5kW for $2000 https://www.ebay.com/itm/125917758638
Brand new 11kW for $7800 https://www.ebay.com/itm/374562225550

While 5kW generator would be small for a house, if inverter can add its power then it supplements surge load, so generator only supplies average load & charging while it runs. FLA battery's desired charge current (0.12C?) plus simultaneous loads may be what you want, for proper charging during overcast.