specifying High school 15-20 kw system

bcguy

Hi, looking for advise on system components and configuration.
I am part of a volunteer group looking at installing a grid tie system on the local high school in BC Canada. The idea is that the money saved on the power bill will go into a scholarship for students following a renewable energy career path. The funds will come from donations and grants.
The service is 208 volt, three phase. The roof is standing seam metal. We plan to use clamps on the seams to install the rails, then the panels. A site survey has been done, and it looks good, no shading issues. The roof is approx. 26 degrees south facing. There is a 150 foot run to the utility room.
The goal is to maximize power delivered for the dollar, and long trouble free service life.
So far the best inverter solution that we have come up with is using 3 of the SMA sunny boy 6000-US-12 with built in AFCI which it seems we have to have.

Any thoughts or suggestions most appreciated.

Dave

Cariboocoot

Re: specifying High school 15-20 kw system

As a fellow BC resident I have a few thoughts. But they aren't what you want to hear.

Electricity here is really, really cheap. As such grid-tie makes no sense whatsoever. There are no incentives to make its cost even remotely competitive with BC Hydro generation. For many locations in the province the insolation is not great: short daylight in Winter, plenty of rain or snow or at least clouds.

Frankly such a venture is a waste of money, no matter where that money is coming from. It would be better spent on conservation measures. But I'm sure people want to do it as a trendy feel-good "we're-doing-something-for-the-environment" symbol.

Put the money that would be wasted on this effort to the scholarship directly. The only reason there will appear to be a savings on the hydro bill is because the capital expenditure amortized on the solar equipment will not be taken into consideration. It is a false economy.

bcguy

Re: specifying High school 15-20 kw system

Thanks, yes I actually agree with you somewhat, although with the govt. mismanagement of hydro, how long will the low rates last? Rates are already going up in the next few years. Also, this is an educational project, I find it empowering to produce your own electricity, and not be so dependent on the grid, hopefully more people will discover this. I also think that decline is the new normal for industrial society, things may not be as stable it the next 20 years as the past, so putting money into bonds or markets will become very risky. This is a hard asset that will continue to produce as energy prices keep rising.

Any suggestions on the tech side?

Cariboocoot

Re: specifying High school 15-20 kw system

So long as you understand the actual production cost will be approximately five times (or more depending on location) that of BC Hydro even with the upped rates.

Oh and note that a GT system most definitely is dependent on the grid; it produces nothing in an outage.

I agree with the choice of the SMA inverters, as they are top quality and are probably the best choice for a 3 phase standard GT system. But to power three 6kW inverters is going to require a huge amount of PV: 18kW worth (or a bit more). Have you got room for all that? Picking on a 255 Watt monocrystaline (more efficient) panel we see it is 66" long and 40" wide or 1.67 meters by 1 meter. To get ~6kW you'd need 24 of them; think 48 square meters of space per array. A polycrystaline equivalent would be slightly larger.

The 150 foot run to the inverter shouldn't be too much of a problem because the inverters run in the 400 Volt range.

I am also going to say that this is a big project, and really needs not only the inclusion of BC Hydro but a licensed professional electrician who understands commercial solar installations. I don't see what the students will be contributing and the extent of their learning will be to follow along. Maybe they could price out the numerous components needed? You know; find a good deal on $24,000 worth of solar panels and $9,000 worth of inverter?

bcguy

Re: specifying High school 15-20 kw system

Ok thanks,

A rough calculation says the yield will be about $1500/year at current pricing, so yes I will take a long time to pay it off.

The school has electricians who will do the wiring, so we are covered there at least. The roof is big, I did a quick cad sketch, and it will hold up to 96 250 watt panels. We are waiting on an engineers report on wind loading to see if there is a setback required, which would mean less panels.

The students probably wont be involved physically, having a bunch of teens up on the roof...

I looked at the new SMA inverters which supply emergency power in a power outage, but it looks like they are 2% or more less efficient, so it might be a hard sell to the bean counters.

Cariboocoot

Re: specifying High school 15-20 kw system

bcguy wrote: »

Ok thanks,

A rough calculation says the yield will be about $1500/year at current pricing, so yes I will take a long time to pay it off.

The school has electricians who will do the wiring, so we are covered there at least. The roof is big, I did a quick cad sketch, and it will hold up to 96 250 watt panels. We are waiting on an engineers report on wind loading to see if there is a setback required, which would mean less panels.

The students probably wont be involved physically, having a bunch of teens up on the roof...

I looked at the new SMA inverters which supply emergency power in a power outage, but it looks like they are 2% or more less efficient, so it might be a hard sell to the bean counters.

Well the kids may not be able to do any leg work, but there's nothing that says they can have all the data presented to them - and see what conclusions they draw. Sometimes they can surprise you.

I wouldn't bother with the EP SMA inverters either, as there small output in the even of an outage will mean nothing to a school.

Where in BC will this be? As there's a pretty big difference between one place and another sun-wise. (I spend a lot of time explaining to non-residents just how big this province is. They can't seem to get the idea of it. )

bcguy

Re: specifying High school 15-20 kw system

The location is Salt Spring island. I wonder about the EP SMA inverters. If the power was out for a few days or more, then charging cell phones etc could be important.

BB.

Re: specifying High school 15-20 kw system

Also, look at the billing plans that would be available to the school...

In many places in the US, commercial (including schools/government) have quite different billing tariffs vs residential... And in some cases, adding solar can actually increase the schools energy bill.

-Bill

bcguy

Re: specifying High school 15-20 kw system

Yes, thanks, we are in the process of getting our hands on that info.

mike95490

Re: specifying High school 15-20 kw system

and sometimes even huge installs, have faults. Bad panels installed, then removed after several years, at 24 schools in sunny San Diego, Calif. http://www.utsandiego.com/news/2012/Sep/13/sun-sets-on-solar-panels-at-24-schools/

And there is the other one that never got off the ground http://www.sandiegoreader.com/news/2012/jun/19/stringers-solar-power-company-sues-san-/

westbranch

Re: specifying High school 15-20 kw system

If the power is out on Saltspring, will it not be out for the Cell repeater?

niel

Re: specifying High school 15-20 kw system

westbranch wrote: »

If the power is out on Saltspring, will it not be out for the Cell repeater?

they should have battery backup and could last for a spell depending on usage and capacity present.

aside from what arguments were presented already about not going gt with this, it would be even worse to be able to power it fully in the absence of the grid and possibly dangerous to have that large of a battery bank to do it with. even if a miracle in batteries occurred i doubt the guy that kept school open because of the outage being avoided would not be the most popular person in the school. thinking smaller on the backup could fly so as to keep a minimum of lighting and power available so as to allow safe egress from the school and keep the school secure