Help me design the most efficient system

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heynow999
heynow999 Solar Expert Posts: 80 ✭✭✭✭
in Advanced Solar Electric Technical Forum #1
Here in Ontario, Canada, we have a new government program where they will pay 80.2 cents for PV generated electricity. I am part owner of a company that installs solar panels. We mostly do solar pool water heaters. We have done a few (3) PV systems. We think the new program could be big and we want to install our own system for experience, to used as a showcase and just because it is a damn good investment. Up to 10kw gets approved with a rubber stamp so we want to do a 10kw system.

So the idea is to get the absolute most production out of a 10kw system. We a flat roof with due south orientaion and no shade. So what different ways are there to acheive this? What is the best direction and inclination of the panels? (43 deg N) We get a lot of clouds here, are there panels that perform better in cloudy weather? Would we be better to just use Sanyo's (+10,-0)? What about inverters? I have heard about a company called "Solaredge" that claims a 97% efficiency.

I am sure there are many things that I have not touched on

Thanks

Peter
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    Re: Help me design the most efficient system

    You can play with the Solar PV Watts website and see what it predicts for your system (fixed, 1 axis or 2 axis tracking, east of south, or west of south, etc.) based on historical weather patterns.

    I am assuming you mean $0.80 per kWhr--which is very high price paid for power.

    Just confirm that you have a contract for that price that is enforceable for the next 5-10+ years (whatever your payback period is)... I worry that the programs/subsidies around here (State of California and US Federal Gov) are unsustainable in the face of huge budget deficits.

    Also, California went to a system that required some sort of ceritification system that <10,000W systems would generate the power (old program, you could install the 10,000W system in your basement and still get the tax credits/rebates).

    For systems >10,000watts, there had to be an approved logging system (telephone or Internet Connection) to get the payments. For >100,000 Watt, the logging system had to meet additional requirements (as I recall).

    When you guys pay around $0.08 per kWhr RETAIL for electric power, somebody is getting a raw deal.

    Just heard a solar ad on the radio this evening. A local irrigation district installed some sort of solar PV setup... Saving them $400,000 a year in power costs, plus they get ~$6,000,000 (in cash?) over 5 years for the generated power. Money is coming from somewhere.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: Help me design the most efficient system

    a flat roof has a southern orientation?:confused: that is a new one on me. 10kw in pv will occupy a great deal of area so will that roof accommodate them all? in any case they will need mounts that can be adjusted to the correct elevation. if adjustable, then this could account for seasonal changes as well rather than a one size fits all angle of your latitude plus 15 degrees.
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  • heynow999
    heynow999 Solar Expert Posts: 80 ✭✭✭✭
    #4
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    Re: Help me design the most efficient system
    niel wrote: »
    a flat roof has a southern orientation?:confused: that is a new one on me. 10kw in pv will occupy a great deal of area so will that roof accommodate them all? in any case they will need mounts that can be adjusted to the correct elevation. if adjustable, then this could account for seasonal changes as well rather than a one size fits all angle of your latitude plus 15 degrees.

    Ok, I guess you are right!

    What I mean is that it is a rectangular shape roof, where the short side faces south. Ideally the long side would face south, but the way it points the racks can run side to side and not waste space. They don't have to be on a diagonal. The roof is about 22' x 80'. I think there would be enough space for 10kw

    -the contract is with the Ontario government of 20 years!
    -there is no need to qualify any system, because the only incentive is the 80.1 that they pay for electricty produced. There is no capital subsidy. I guess I could put it in my basement, but my payback might take a bit longer!
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #5
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    Re: Help me design the most efficient system

    For costs, get the best deal you can on price per watt, its a loser to go after for example the Sanyo HIT as its much more expensive per watt and that's all one cares about if return on investment is the primary concern.

    Evergreens can be had for under 2.40 watt, similar for Kyocera and other major brands

    I would suggest a dual 5kw system, the Xantrex GT5.0 is an excellent inverter and need no other extras as the disconnect and communications is built in.

    At 80 cents kWh, you will make a decent income, for your latitude, you should have the panels at a minimum of 43 degrees, flat would have some very poor performance

    And your roof is fine area wise .. I have 14kw on my roof and could fit more, buts its pointless as I already net out my usage.
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  • Green Building Solutions
    Green Building Solutions Registered Users Posts: 24 ✭
    #6
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    Re: Help me design the most efficient system

    If you have a SolarPathfinder and the software you can take photos and do a shade analysis on the system and the software can go through and tell you the best tilt and orientation for the system based on your location and shading obstructions.

    -Michael
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #7
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    Re: Help me design the most efficient system

    I would use a well known string inverter maybe sma or fronius I was a fan of the Xantrex GT but i have had a 75% failure rate and many other installers are saying the same thing and we are now getting refurbished units as replacements.
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  • heynow999
    heynow999 Solar Expert Posts: 80 ✭✭✭✭
    #8
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    Re: Help me design the most efficient system

    I am glad more people have responded to my tread. I appreciate all the input.

    As for shade and orientation, that is pretty easy. We had a pathfinder with the software package, but there is virtually no shade on the site. Also 34 degrees and about 190 degrees is optimum for this area.

    I guess my question was more hardware related. Maybe I should have said "what is the most cost effective way to produce electricity by PV panels" or something like that.

    So I have been busy working on my question and it seems that at 80.2 cents a kw a tracker starts to make sense. I have also learned how to use "Retscreen" which is software that models PV systems. I found this single axis tracker that I can get locally for about $1,600 that will hold 1.260 kwatts. I would need 8 for ten Kw.

    http://www.degerenergie.de/downloads/toptraker-8.5-toptraker-25hd_en.pdf

    The best return I can get Retscreen to produce is the single axis tracker with the cheapest cost per watt panel, which is probably a Suntech 175 for about $2.50 Canadian/watt. I can get Sanyo's for about $4/watt, but the cheaper Suntech's produce a better result

    The returns are pretty amazing. I figure about $50k (CD) for the hardware with me doing the installation. It would produce $13,500 a year with a payback of 3.7 years and produce $270,000 worth of electricity over the 20 year contract

    Here's a huge two axis tracker that the tracker sales guy has in his backyard. We saw 4.8kw of Sanyos produce over 6 kw
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
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    Re: Help me design the most efficient system

    "Here's a huge two axis tracker that the tracker sales guy has in his backyard. We saw 4.8kw of Sanyos produce over 6 kw"

    whoa, stop right there.
    are you implying a tracker allowed the pvs to produce more? that won't happen as they are not concentrators. the pvs themselves can produce a bit more in sun conditions that are above the 1000w/m^2, but at the same time the temperatures will be acting upon the pvs and i find it a bit reaching to say it produced that much. it could've been in conjunction with edge of cloud events or receiving some other additional light input reflected from who knows where, but it sounds more like an inaccurate meter.
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  • heynow999
    heynow999 Solar Expert Posts: 80 ✭✭✭✭
    #10
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    Re: Help me design the most efficient system

    Sure it was several factors that caused the high output. It was really cold, there was snow on the ground that reflected the light, and there were scattered clouds. The reading was from the inverter. He had two 5kw inverters side by side, each one doing one side of the tracker, and we saw similar numbers on each inverter.

    This is exactly what I was asking. Because the program here in Ontario pays a lot of money for PV power, but only up to 10 KW, what is the best way to get the most bang for your buck out of 10kw. This tracker is obviously the best way, but it is a little big for my location! I think these are going to be popping up all over Ontario. I could do several small one axis trackers.

    The tracker owner liked the idea of using sanyos because he could fit more on the tracker. He can get 9.6 kW on each one, 48 x 200 watts. If he used a less efficient panel he could not get as many watts per tracker
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
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    Re: Help me design the most efficient system

    those events are not consistent and as said are not attributable to a tracker being used. there are really only a few ways of increasing output in terms of watt/hours and one is tracking. it will still require a great deal of room to turn and will cost allot so adding that much more in pvs cost-wise would add far more power than the tracker, that will fail due to mechanics. due to area constraints you may not add all of the cost difference in pvs, but i still believe the best is to add more pvs. one other way is to go with the highest module efficiency you can find in the largest pvs available. there is just no way to get around needing so much area to reap power from solar as you are talking minor area differences in your quest to cram as many watts (correction-watt/hours) in as possible for a given area.
    the method of using extra light reflected to the pvs must be naturalized lighting as you don't want to concentrate light that will degrade the life of the pvs and void warranties. ie mirrors and lenses. white paint is fine from a surface as long as it is not being focused towards the pvs.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #12
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    Re: Help me design the most efficient system

    Note:

    I have moved the SolarEdge discussion to its own thread:

    Solar Edge [from: help me design the most efficient system]

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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