New Offgrid, DC or AC Coupled, and components

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Re: New Offgrid, DC or AC Coupled, and components

Postby Privatteer » Sun May 27, 2018 3:04 pm

dakiller wrote:I still don't get why that is the case. If you are AC coupled.


From what I understand from reading the manual on a Victron unit for AC coupling the issue is the switching off and on for large loads.
The inverter controlling the offgrid system has to quickly ramp back and push any excess power into the batteries to prevent a voltage surge. At the same time its telling the AC coupled units to ramp back.
Vice versa for when the load is turned on.
Even if it takes just a second for the AC coupled units to respond there is still that time where there is a difference that the batteries are handling.
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Re: New Offgrid, DC or AC Coupled, and components

Postby dakiller » Sun May 27, 2018 3:09 pm

Privatteer wrote:
dakiller wrote:I still don't get why that is the case. If you are AC coupled.


From what I understand from reading the manual on a Victron unit for AC coupling the issue is the switching off and on for large loads.
The inverter controlling the offgrid system has to quickly ramp back and push any excess power into the batteries to prevent a voltage surge. At the same time its telling the AC coupled units to ramp back.
Vice versa for when the load is turned on.
Even if it takes just a second for the AC coupled units to respond there is still that time where there is a difference that the batteries are handling.

Thanks, that makes complete sense
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Re: New Offgrid, DC or AC Coupled, and components

Postby davidg » Sun May 27, 2018 6:36 pm

dakiller wrote:Insulation is well up in the list of priorities for this build. One of them is to ask our truss and framing designer about going with 120mm exterior frame over 90 for the added insulation.

Hmm, we are at minimum of R6 in the walls (300mm cavity for the insulation) in excess of R7 for the ceiling/roof (500mm cavity for the insulation), although the additional foils under roof metal etc it should be higher.
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Re: New Offgrid, DC or AC Coupled, and components

Postby TsaTsa2CV » Wed Jun 13, 2018 7:33 pm

Hi dakiller,

Looks like you are at the stage we were some years ago. New energy efficient, off grid house, shed workshop/ art studio, pool, water storage and general infrastructure to make it all work!

Our initial solar setup was 5.55kW of PV on shed facing slightly east of north to take advantage of longer winter sun hours. 1680ah of Raylite PB 24V battery setup. 4024 Latronic inverter and 2 Apollo charge controllers.

The house, double glazed e-glass, Argon filled optimized for cold climate mainly facing north and to stunning views of cathedral ranges with overhangs to self shade 100% in summer. Hydronic slabheating with Sophel boiler/fireplace with 400lt header tank incorporating a 45m heat exchange coil to preheat cold water inlet to Sanden heatpump hot water System when heating is required giving us endless how water. The Sanden uses on average 1-maximum of 3 kWh per day depending on using dishwasher and washing machine and comes on between 11am and 3pm. On cloudy days we can easily scrip a day. All lights are warm LED, the internet is always on. We cock with gas buried in an underground tank filled once every 12 month! We installed also an 7kW aircon for summer running straight of panels from first thing in the morning just ticking away drawing 500- 800w.
This year we installed a 60,000lt infinity pool with built in pool cover to retain heat and keeping it clean and safe.
We installed a second solar system , this time an SP PRO 7.5 and 12kW of lithium iron batteries. This DC coupled system now runs the House with the old AC coupled system the pool, workshop/studio.
We have set it up so should the house battery drop below 50% SOC we automatically charge from the old system to 70%. To date, this has happened only three times transferring some 2kWh across. Pool pump and Sanden heat pump are connected via Sonoff 15 switches and remote controlled via Wi-Fi at the moment from Thailand!. We will also hook up the 11kW pool heatpump to a Sonoff TH 15 for remote control.
We have deliberately incorporated some backup into our design if and when a component will fail and in order to split the load over two systems. The maximum we have ever drawn was 18kwh in 24h. After sunset we rarely use more than 3-4kwh with lighting and TV and hydronic circulation pump on.
On suny mornings in winter the sun will easily heat the house to 24°C by 9.30am with only a short 2-3h hot burn to top up at night. We have no need to smolder the fire all night polluting the pristine air up here.

We ablsoluly love the off grid life and the only difference is scheduling power consumption to an appropriate time. I feel confident that you will get away with a much smaller system!

Good luck and have fun seeing it turn into successful reality!

PS I have suggested Sanden to our architect for himself......he has specified them on every job since!
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Re: New Offgrid, DC or AC Coupled, and components

Postby Gordon-Loomberah » Wed Jun 13, 2018 7:46 pm

TsaTsa2CV wrote:We installed also an 7kW aircon for summer running straight of panels from first thing in the morning just ticking away drawing 500- 800w.


Who makes air conditioners operated directly from panels? I'd be interested in a DC aircon for my power shed, assuming it has a decent EER. What voltage does it operate at, and how is the PV voltage controlled?
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Re: New Offgrid, DC or AC Coupled, and components

Postby Privatteer » Wed Jun 13, 2018 8:39 pm

Coincidentally I had 2 pages open in my browser for this.
https://www.ecoworld.com.au/product-pag ... -panel-kit
A 48V DC version
https://www.coolairaustralia.com/copy-o ... er-systems
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Re: New Offgrid, DC or AC Coupled, and components

Postby dakiller » Wed Jun 13, 2018 8:47 pm

TsaTsa2CV wrote:Hi dakiller,

Looks like you are at the stage we were some years ago. New energy efficient, off grid house, shed workshop/ art studio, pool, water storage and general infrastructure to make it all work!

Thanks for sharing.

What size house is this all for? Number of people?

You also have about double the battery capacity that I'm planning here too.
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Re: New Offgrid, DC or AC Coupled, and components

Postby australsolarier » Thu Jun 14, 2018 8:47 am

Gordon,
the "solar air conditioners" privatteer linked still need mains. the americans however do sell a purely solar aircon. the problem is, they are really really expensive. so in the end having a larger inverter (or a small dedicated inverter) and the normal run of aircons comes to about the same, dollar wise. and the extra solar panels can be used somewhere else when they are not needed for the dc aircon.
i found in my power room the air conditioner doesn't use that much power at all. nothing compared to the house. if you really want to go cheap, look into those window boxes. they are quite cheap compared to the split aircons, though not so efficient. and no tradesmen needed.
your summers are a bit hotter though than where i am.
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Re: New Offgrid, DC or AC Coupled, and components

Postby australsolarier » Thu Jun 14, 2018 9:00 am

dakiller,
as Gordon mentioned, you might consider having your panels in different orientation. the problem is not when the sun shines. we have plenty and too much solar generation. it is in the winter when the sun does not shine that we need as many solar panels as possible. when it is overcast. in overcast weather flat (horizontal) panels bring the most. (in summer they bring as much as your 38 degrees, in the winter much less in sunny weather) however i have much flat roof areas.
most solar chargers, inverter/chargers and grid feed in inverters can be overpowered. solar panels are much cheaper than batteries.
in my case (ca 20kwp) most panels are flat. in sunny weather the 30 degrees bring more. however when overcast the flat arrays take over. there are still a few winter days where the wood stove is needed for back up. in your case the generator.
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Re: New Offgrid, DC or AC Coupled, and components

Postby dakiller » Thu Jun 14, 2018 9:05 am

australsolarier wrote:in overcast weather flat (horizontal) panels bring the most. (in summer they bring as much as your 38 degrees, in the winter much less in sunny weather) however i have much flat roof areas.

Have you got any links that show some data on this?
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