Can solar system act like off-grid system, "on demand"?

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Can solar system act like off-grid system, "on demand"?

Postby Opribution on Tue Mar 12, 2019 12:04 pm

I want to install a solar system to replace utility company power.

My idea is to have the solar system run everything and "bypass" the utility company power, as long as the solar system is functioning but, in the event of a solar system failure (or lack of sunshine ie. in winter) I'd like the utility company power to take over automatically, rather than have a backup generator take over.

Then, when the solar system is functioning again (either failure fixed or, sunshine is adequate again etc.) have the solar system automatically bypass the utility company power to take over again.

Is this possible?

If so, does anyone have any suggestions as to the solar system I should get?

It's a typical 4 bedroom house at around 2000 sqft.

Thanks.
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Re: Can solar system act like off-grid system, "on demand"?

Postby Mike Curran on Thu Mar 21, 2019 9:41 am

Opribution wrote:My idea is to have the solar system run everything and "bypass" the utility company power, as long as the solar system is functioning but, in the event of a solar system failure (or lack of sunshine ie. in winter) I'd like the utility company power to take over automatically, rather than have a backup generator take over.

Then, when the solar system is functioning again (either failure fixed or, sunshine is adequate again etc.) have the solar system automatically bypass the utility company power to take over again.

Is this possible?
Very possible. Page 34 of Outback's Mate3s programming guide (link here http://outbackpower.com/downloads/docum ... de_web.pdf) describes 2 such operating modes for Outback's equipment, HBX and Minigrid. Note each has different requirements, especially with regard to size of your PV source vs. size of your house loads. You will also need to consider battery sizing if you intend to run your house as if it were off grid most of the time.

Take a look at the link/manual, then post back with further questions.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221
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Re: Can solar system act like off-grid system, "on demand"?

Postby SandyP on Thu Mar 21, 2019 6:51 pm

Opribution wrote:....Is this possible?
If so, does anyone have any suggestions as to the solar system I should get?....


Yes, it is .
Do you have a budget for the cost of a system?
What is your electricity usage (per month) in Winter?

It will always be a balance between system cost and how grid independent you want to be.
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Re: Can solar system act like off-grid system, "on demand"?

Postby pss on Thu Mar 21, 2019 7:16 pm

I looked at your post.

IMO, I would proceed as follows: Find your last 12 months of electric bills. Add up the total killowatt hours used by the month and for the entire year. Generally, March, April and May are low use months and September/October too. These are usually the months when you probably are not running the AC or the furnace. Now, look at your highest months. if you want to eliminate bills for those months, you will have to size your system to do that. I would advise that if you are using 1500 kWh on a peak month (could even be over 5000 kWh for a hot month depending on your property), then you would take say 5000 divided by 30 days/month. That is 167 kWh per day. So you would need about a 30,000 watt system. In a hot environment, the system will actually produce about 70-75% of the power on the solar panels nameplates. So 10k watts of solar panels would really produce 7k watts of power in the heat. But in the winter they could produce 13k watts of power. Cold is good, heat is bad for solar. So begin here and lets us all help you to size up your system. make sure you know the hottest temps in the summer and coldest temps in the winter for your installation location.
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Re: Can solar system act like off-grid system, "on demand"?

Postby scottmr1 on Thu Mar 21, 2019 8:21 pm

I am running the way you describe for 6 years now. The PV array provides my power until the batteries get low then system switches to utility power until the sun comes out the next day and charges my batteries up sufficiently. Once I reach about 52v the HBX drops the utility and takes over powering my house loads. Works like a charm if you ask me ... we generate 70-90% of our needs depending on weather and if we have visitors. Electric bill used to be $350 and is now under $100. Basically configured as off grid and using the utility as most folks would use a generator, ie, when batteries are low and the sun is not shining. System paid for itself in less than 5 years, pretty happy with it.

There are two of us that work from home fulltime. We have a normal refrigerator and do use the microwave now and again but all LED lighting. I have 4.2kw worth of panels in 6 strings, the 3500w 48V inverter, and just replaced my 8 L-16s with 2 of the 3.5kwh Simplify 48V batteries. I will say this, if you are pumping your own water make sure you use a low amperage pump, that was my single biggest power draw.
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Re: Can solar system act like off-grid system, "on demand"?

Postby Greg T Fordan on Fri Mar 22, 2019 9:42 am

Hi Scott,
Nice to know that you are satisfied with how the HBX feature works in your system.
Just for other Users' info, the "Grid Use" feature can also do the "on demand" trick. The user can just pick the times to connect and disconnect from the grid. There are options for weekdays and weekends.
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Re: Can solar system act like off-grid system, "on demand"?

Postby gtarolli on Fri Mar 22, 2019 10:42 am

So long as you do not want to sell to the grid, I think it is fairly easy - there are various ways you can run on RE (e.g. solar) and batteries until low voltage or high load triggers connecting to the grid, e.g. HBX or Load Transfer mode. Selling when you have fully charged batteries in addition to the above is tricker and may require an external relay depending on your requirements.
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