Battery bank for a 12kw solar system

[Beanyboy57]

Update.

The 10kw system has now been running without a hitch for a few months producing an average of 40kw/h per day. We are charged at 42 cents per unit (kw/h) by our provider and they will give us 48 cents per unit that we provide to the local generator powered grid.

[Beanyboy57]

New 10kw system with smoothing solution installed and operating.

After a long delay we finally have our solar system plus smoothing solution installed. In the end we had to settle for a 10kw system which we are satisfied with now that it is working efficiently. We can upgrade to 12 kw when more funds are available later this year.
We had a few teething problems, the main issue being that the power from the grid was at a too high voltage. We use 240v but the power from the step down transformer to our premises was reading at 260 and was causing issues for the inverter according to the installer.
Since the electricity supplier adjusted this we have had no issues.
Generally we are getting around 10 hours of generation each day, the weather was overcast when these photos were taken, but we still get a modest amount of generation even when the sky is totally grey.


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[russ]

From your previous post I had guessed that you are a teacher.

[Beanyboy57]

As usual - Beanyboy going green and wasting others money. WTF do you need to analyze etc?

We are a school that uses real life data from our surroundings to give a local context to our studies, after all we are 1000km from the nearest city so we don't have many options. The data we will gather is very useful for math lessons and we can also use the PV installation as a means of studying the technology and learning how it works. Learning mathematics by measuring and analysis of data in a real life situation gives meaning to otherwise abstract concepts. Producing a multi-media video will be another off shoot of the project
The fact that we will have our own solar array with live data to use is the main purpose of this project.
If it turns out to be not cost effective then that is what the students will learn.
We could do the whole thing on a whiteboard but I can guarantee that these kids will learn a whole lot more from a real life hands on experience.
By the way hundreds of Perth metropolitan schools have grid tie systems that have greatly reduced their power costs because they cut power costs during the day and pump out power to the grid during the school holidays (12 weeks per year) and weekends (104 days per year).
Yes our system out here in the desert may be different but I am still working on gaining an exception to the 'smoothing solution'.

[russ]

As usual Russ you shoot your mouth off without checking any of the facts.
Our environmental awareness program will check the data to see if solar power is in fact useful to the school. We go in with an open mind, gather data, analyse it and then come to a conclusion.
There is no direct cost to the school as the whole project is fully funded by a multinational mining conglomerate but we will still use the purchase and installation costs in our analysis.

As usual - Beanyboy going green and wasting others money. WTF do you need to analyze etc?

[Beanyboy57]

Smoothing Solution? WTF?

I can only guess from your description they are talking about Walk-In, Walk-Out feature on large scale UPS systems on generators which means the rectifiers turn on/off in smaller steps over a period of time so as not to load/unload generator with too much energy at one time cause it to slow down or over speed which could cause a Black Out. What I am having a hard time with is to live somewhere using diesel generators are so small a 12 Kw load somewhere switching on/off would cause the utility a problem. I have dozens of data centers with dual 2 MW generators and a 12 KW load switching on/off is nothing. I mean that is not but only 1 of many chilled water air handlers for cooling or a couple of racks of equipment.

I am not sure what size the generators are or how to find out but I can tell you that it is a very small town with a population of 350 people (on a good day). I do know that the poco have discouraged town residents from installing any solar arrays in the past.
I can tell you that the poco is building a new generating plant that combines diesel power with a large solar array. Not sure how it will work but I am interested to find out.

[Beanyboy57]

Hi Jon - Sounds more like your "how to piss money away awareness program". Wonderful lesson for the kids - be green and damn the cost!

As usual Russ you shoot your mouth off without checking any of the facts.
Our environmental awareness program will check the data to see if solar power is in fact useful to the school. We go in with an open mind, gather data, analyse it and then come to a conclusion.
There is no direct cost to the school as the whole project is fully funded by a multinational mining conglomerate but we will still use the purchase and installation costs in our analysis.

[Beanyboy57]

That may be similar to what is going on in Hawaii. The Power Co has been refusing to allow people to connect their solar pv systems. They say that because the POCO didn't have enough "hot back up" power available to cover the loss of the home solar generation due to clouds there would be fluctuations on the grid affecting all customers. The idea was for some type of power storage system to "ride through" a short outage which would help the Power co maintain the grid.

What I didn't understand is how would the POCO know that the solar was not producing and the "ride through" or UPS was now supporting the loads. There will need to be very good communication between the end user with the "smoothing solution" and the POCO so they know when to ramp up the main generators to cover the loss.

I don't know what they are up to but they also said that if we install the smoothing solution they will pay us 40c a kw for power that we pump back into the grid. Given that school is closed for 12 weeks of the year and we are likely to average 50kw per day most days (not much cloud out here in the desert) we could reduce our power bill by around 17% which would save the school a fair bit of money each year.
Perhaps they believe that the cost of the smoothing solution will deter us from installing our 12kw array. Our array is so small compared to the output of their generators I don't believe we would make any impact if our array stopped producing for a short period.
A large mining company is funding the whole project, it will cost zero from our school budget.

[russ]

we are determined to install it as part of our environmental awareness program.

Hi Jon - Sounds more like your "how to piss money away awareness program". Wonderful lesson for the kids - be green and damn the cost!

[Mike90250]

Sadly, the utility is god, and you have to play by their rules, regardless how silly they are.

[SunEagle]

Lots of ways to do that. Today's Smart Meters have a com link, and their own dedicated slice of the cell telephone radio freq, or Ethernet right through their power lines if so equipped, or to the customer phone line. Back in TX I had a daily email graphing out power usage minute by minute, and on Sunday a weekly report. Scares the Hell out of me someone looking inside my home without my consent. I mean heck if that were a person looking through my windows at night or even day I can legally shoot them dead for doing that in TX.

I understand how a smart meter would know if a solar pv generation stopped and then the house would use the POCO, but if there is a something to "smooth over" the loss of the solar pv system like a battery then how would the POCO know there was an issue. The power would still be generated at the home site.

So unless they have telemetry on all of the generating points at the house (solar, battery, wind, etc.) they couldn't tell the difference as to where the local generation was coming from or if there was a problem with any of them.

[Sunking]

What I didn't understand is how would the POCO know that the solar was not producing and the "ride through" or UPS was now supporting the loads.

Lots of ways to do that. Today's Smart Meters have a com link, and their own dedicated slice of the cell telephone radio freq, or Ethernet right through their power lines if so equipped, or to the customer phone line. Back in TX I had a daily email graphing out power usage minute by minute, and on Sunday a weekly report. Scares the Hell out of me someone looking inside my home without my consent. I mean heck if that were a person looking through my windows at night or even day I can legally shoot them dead for doing that in TX.

[SunEagle]

Ok, so before you go further, you need to have the "official definition of smoothing solution" in your hands. You don't want to get model G installed, and they refuse the connection because you were supposed to have model H. It could be as simple as something like a backup UPS for your system, but that would have no effect on the Power Co.. So maybe they want something else. I've never heard of "smoothing solution".

That may be similar to what is going on in Hawaii. The Power Co has been refusing to allow people to connect their solar pv systems. They say that because the POCO didn't have enough "hot back up" power available to cover the loss of the home solar generation due to clouds there would be fluctuations on the grid affecting all customers. The idea was for some type of power storage system to "ride through" a short outage which would help the Power co maintain the grid.

What I didn't understand is how would the POCO know that the solar was not producing and the "ride through" or UPS was now supporting the loads. There will need to be very good communication between the end user with the "smoothing solution" and the POCO so they know when to ramp up the main generators to cover the loss.

[Sunking]

Smoothing Solution? WTF?

I can only guess from your description they are talking about Walk-In, Walk-Out feature on large scale UPS systems on generators which means the rectifiers turn on/off in smaller steps over a period of time so as not to load/unload generator with too much energy at one time cause it to slow down or over speed which could cause a Black Out. What I am having a hard time with is to live somewhere using diesel generators are so small a 12 Kw load somewhere switching on/off would cause the utility a problem. I have dozens of data centers with dual 2 MW generators and a 12 KW load switching on/off is nothing. I mean that is not but only 1 of many chilled water air handlers for cooling or a couple of racks of equipment.

[Mike90250]

Ok, so before you go further, you need to have the "official definition of smoothing solution" in your hands. You don't want to get model G installed, and they refuse the connection because you were supposed to have model H. It could be as simple as something like a backup UPS for your system, but that would have no effect on the Power Co.. So maybe they want something else. I've never heard of "smoothing solution".