Before signing, what else?

lasitterlasitter Solar Expert Posts: 56 ✭✭
http://www.ncdm.com/74Knollwood/CCady-Contract.pdf

This is what I have in front of me at the moment, and I'd like to know what else I should have specified before signing on the dotted line.

Would you want to have more information about the rack system?

The system is not (yet) about batteries and charge management, or about adding a home generator later. What additional information would you ask to be added to the quote to make sure that components worked together easily later on, if added?

What extra metering equipment or things like transfer switches should I seriously consider adding at the same time?

Thanks.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,698 admin
    Welcome to the forum... I would suggest that you not post a lot of personal information on the web (name, addresses, etc.).

    But, anyway.

    I don't see anything to worry about in the contract (just took a quick look, and I am certainly no expert)--But I do wonder about what it is you want to do in the future.

    Grid Tied Solar power systems, in general, do not function if the grid/utility is down. You get an ice storm or car hit a utility pole, your solar power system is off line until the utility power is restored. There are limited exceptions to that rule--But the GT system you are getting is not one of them (not anything wrong with that--Just the limitations of the technology).

    Generator--More or less, the GT solar power system should be installed on the Utility side of a generator transfer switch. Home emergency gensets generally do not have steady enough line frequency for GT inverters to "sync with" and, if they did sync, the generator will not like being back fed energy from the solar GT inverter (line voltage may go too high, generator could be damaged).

    Then you asked about a battery and charge management... While it is possible to connect an off grid AC inverter with a GT power system--It is usually not the most cost effective and efficient method.

    If you want a battery backed solar power system--It is generally a good idea to start with a Hybrid AC inverter... Basically it is an off grid AC inverter with the capability to operate in Grid Tied mode and feed excess solar array energy back to the utility system (GT Mode). And if the AC mains fail, the inverter flips and internal transfer switch and starts feeding energy to your "protected" AC loads (standard off grid inverter mode).

    And, many of this Hybrid systems (and some pure off grid AC inverters) already have an AC2 connection that is intended for connecting to a genset. The Hybrid inverter has the ability to manage all three power (or more) power sources automatically (AC mains, Solar array, backup genset, etc.).

    If you are looking to save money. A pure GT solar system (no batteries) is the most efficient, cost effective, and least maintenance.

    If you occasionally (say less than 2 weeks a year) need backup AC power--Then a standalone genset + GT solar + Utility power is usually the best solution.

    If you have power outages that are more than 1 month long, mulitple times a year, little area to store fuel (or cannot/do not want to use natural gas), then perhaps a Hybrid power system is your best solution. However, in general, off grid and hybrid inverter systems (plus battery bank) do not save you money. The installation and maintenance costs (new batteries every ~5-8 years, new electronics every 10+ years, etc.) really run up the total cost of ownership.

    And lastly, but really firstly, you need to understand your utility's rate structure. Each utility has a unique billing structure. One that can range from very customer friendly (1 year net metering, you buy and "sell" power at retail power rates) to poor (you buy power at retail and sell it back at wholesale with 1 month net metering, and high "connection" fees) to illegal (utility does not allow GT solar). Utility rate plans/tarriffs can have a dramatic effect on the design of your system (and your power usage pattern too can have a large effect--I have time of use billing--and can avoid peak power charges from noon to 6pm--If you have AC/electric heat/different peak times, etc., you many not be able to).

    In general, I am a big believer in spending money on conservation first... For people that live in an older home and never have looked at conservation, it is possible for folks to save upwards of 50% of their energy bill.

    Generating your own power can be expensive (especially for generators and battery based systems)--Conservation is generally less expensive and can result in a nicer home (better insulation, less noise, cold spots; less heat from computers, refrigerators, lighting, etc. in the summer, etc.). I suggest reducing your power usage first, then design a solar/backup power system for your new, reduced usage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lasitterlasitter Solar Expert Posts: 56 ✭✭
    BB. wrote: »
    I would suggest that you not post a lot of personal information on the web (name, addresses, etc.).
    I completely agree, but it's a level of disclosure I can deal with at the moment. I also avoid requests for more information, as this is pretty much what there is.

    Finally, I'm going to delete the .PDF file after a day to two. That will help some.
    BB. wrote: »
    I don't see anything to worry about in the contract (just took a quick look, and I am certainly no expert)--But I do wonder about what it is you want to do in the future.
    First, I want to preserve options. There are decisions that one can make on the front end that close off options down the road.

    I also want to hear opinions about the panel specified, and whether I should get specific about the other mounting hardware.
    BB. wrote: »
    Grid Tied Solar power systems, in general, do not function if the grid/utility is down. You get an ice storm or car hit a utility pole, your solar power system is off line until the utility power is restored. There are limited exceptions to that rule--But the GT system you are getting is not one of them (not anything wrong with that--Just the limitations of the technology).

    This is why I mention the possibility of batteries, charge management, etc.
    BB. wrote: »
    Generator--More or less, the GT solar power system should be installed on the Utility side of a generator transfer switch. Home emergency gensets generally do not have steady enough line frequency for GT inverters to "sync with" and, if they did sync, the generator will not like being back fed energy from the solar GT inverter (line voltage may go too high, generator could be damaged).

    Good info!
    BB. wrote: »
    Then you asked about a battery and charge management... While it is possible to connect an off grid AC inverter with a GT power system--It is usually not the most cost effective and efficient method.

    If you want a battery backed solar power system--It is generally a good idea to start with a Hybrid AC inverter... Basically it is an off grid AC inverter with the capability to operate in Grid Tied mode and feed excess solar array energy back to the utility system (GT Mode). And if the AC mains fail, the inverter flips and internal transfer switch and starts feeding energy to your "protected" AC loads (standard off grid inverter mode).

    And, many of this Hybrid systems (and some pure off grid AC inverters) already have an AC2 connection that is intended for connecting to a genset. The Hybrid inverter has the ability to manage all three power (or more) power sources automatically (AC mains, Solar array, backup genset, etc.).

    If you are looking to save money. A pure GT solar system (no batteries) is the most efficient, cost effective, and least maintenance.

    If you occasionally (say less than 2 weeks a year) need backup AC power--Then a standalone genset + GT solar + Utility power is usually the best solution.

    If you have power outages that are more than 1 month long, multiple times a year, little area to store fuel (or cannot/do not want to use natural gas), then perhaps a Hybrid power system is your best solution. However, in general, off grid and hybrid inverter systems (plus battery bank) do not save you money. The installation and maintenance costs (new batteries every ~5-8 years, new electronics every 10+ years, etc.) really run up the total cost of ownership.

    And lastly, but really firstly, you need to understand your utility's rate structure. Each utility has a unique billing structure. One that can range from very customer friendly (1 year net metering, you buy and "sell" power at retail power rates) to poor (you buy power at retail and sell it back at wholesale with 1 month net metering, and high "connection" fees) to illegal (utility does not allow GT solar). Utility rate plans/tarriffs can have a dramatic effect on the design of your system (and your power usage pattern too can have a large effect--I have time of use billing--and can avoid peak power charges from noon to 6pm--If you have AC/electric heat/different peak times, etc., you many not be able to).

    In general, I am a big believer in spending money on conservation first... For people that live in an older home and never have looked at conservation, it is possible for folks to save upwards of 50% of their energy bill.

    Generating your own power can be expensive (especially for generators and battery based systems)--Conservation is generally less expensive and can result in a nicer home (better insulation, less noise, cold spots; less heat from computers, refrigerators, lighting, etc. in the summer, etc.). I suggest reducing your power usage first, then design a solar/backup power system for your new, reduced usage.

    -Bill
    All good points.

    Conservation: We've had the Mass energy audit with the wholesale changeover to LED lighting. We're getting an extra 8" of insulation over the top, which along with the (free!) sealing work is supposedly worth a combined $650 in savings per year.

    Utility net metering: We're going to get sRECs for the first 10 years that should more than pay for the system. I will run down the "net metering" thing, but I think that we're in the buy retail / sell wholesale after that period of time.

    Hybrid Inverter: Is that something that really needs to be done on the front end of the install process? How do you best plan for the current work to not conflict with the addition of such an inverter later?

  • BB.BB. Super Moderators, Administrators Posts: 29,698 admin
    You are looking at Enphase Micro inverters at the moment (one GT inverter per panel)... They are pretty much a "That is a GT system that ction later" annot be, simply, modified for hybrid operation later" sort of setup.

    The standard Hybrid type inverter is a 3-8 kWatt Off Grid/GT capable central inverter. You have two basic methods to connect the solar panels to your Hybrid system:

    1. You connect the Micro inverter's 240 VAC output to the 120/240 VAC output of the Hybrid inverter. When the utility power is up--The GT output is fed backwards through the Hybrid inverter to the AC mains... Pretty much normal operation. And your Hybrid inverter has to be able to mange the peak output of the GT inverters (i.e., if you connect all 8 kWatt of Micro inverters, you need a >8kWatt Hybrid inverter (of course, you can only connect 1/2 the strings to the hybrid inverter and get a 4-6 kWatt Hybrid).

    2. You strip the GT micro inverters from the roof. You rewire the panels into DC strings and connect them to a solar charge controller (depending on the solar charge controller, typically around Vmp-array of other ~100VDC or 400VDC Vmp-a array-stc rating). The solar charge controller connects to the DC Battery bank. The battery bank + AC mains + AC Backup generator + Protected AC output all connect to the Hybrid inverter.

    3. You forget the Micro Inverter install and go straight to a Hybrid installation. It will cost similar amounts of money (if not less) and be a more standard installation (less, hmmm--I have never seen that happen before situations).

    4. GT inverters (per your quote) and a natural gas (or propane or diesel) backup genset. Of course, you need the natural gas or a large enough property where you can store propane/diesel for your needs (and not bother the neighbors with noise/smell of a large genset).

    #3 is the "standard" solution (array to charge controller to battery bank to AC inverter's DC input, etc.) off grid inverter system. Don't bother with the interim solution. #1 is a bit more rare and can be more complex in design and less than optimal operation (when in off grid mode).

    In either case, a 6-8kWatt Hybrid/Off Grid inverter system is large and complex. If you have never done anything like this before--I would highly suggest that you hire a person (or installer) with lots of experience and references to check.

    You, of course, have other options... For example install a 1.5 kWatt off grid inverter system + solar array + battery bank + small backup genset that can run a refrigerator, well pump, washing machine, LED lighting, laptop computer + cell phone chargers (possible central heat fans + oil/etc.)... All for around 3.3 kWH per day (heating may take more). Small, cost effective solar+genset for backup. Will keep the family warm and safe for a few weeks+ (winter is always difficult for solar "up north"). And don't plan on running the entire home from solar. If you need more power--Get a second large genset that can run (for example) your business for a few weeks--And give you time to find an alternate location.

    Things to remember--Generally you are not the only one without power. For example, no utility power for fresh water/black water pumping. Some cities have turned of fresh water because they did not have power for the black water pumps--And if you don't have regional power after a couple of weeks--Staying in your home may become more difficult (even if you are prepared).

    And, in any case, continue your education. It will help you when you work with others on your potential system design and install. You can understand their questions and be better informed so you can tell if their design will (most likely) meet your expectations.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BrluxBrlux Solar Expert Posts: 73 ✭✭✭
    I don't know what everyone opinions are of the SMA TL-US grid tie inverters but I would probably be going with one if I was doing a grid tied system. It gives you a 1500W outlet that works when the grid is down and the sun is shining. No maintenance and no batteries.

    http://www.sma-america.com/products/...7700tl-us.html

    https://www.youtube.com/watch?v=fF461YYNbtw
  • BB.BB. Super Moderators, Administrators Posts: 29,698 admin
    SMA is good quality, but generally not cheap in the US.

    Nice to have a 1,500 Watt 120 VAC solar powered outlet--But, from what I understand, it requires manual activation and plugging the load into the SMA outlet by the home owner each time it is used(?--I think). Here is a quick paper on the SMA Secure Power Supply:

    http://www.solar-electric.com/lib/wind-sun/SMA-SPS-technical-info.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BrluxBrlux Solar Expert Posts: 73 ✭✭✭
    Yes the 1500W is to a dedicated grid down receptical but it is better than nothing and nice to have that possibility without having batteries. The price of the inverters seems very reasonable compared to other grid ties inverters. For instance the 3K inverter can be had for about $1600, the 5K for about $2400. The 1500W off grid seems to be a regulatory vs technical limit. All the inverter sizes have the 1500W limit. Perhaps it would be better to have 2 3k inverters as opposed to one larger so that you can have 2 1500W power sources.
  • Belmont SolarBelmont Solar Registered Users Posts: 26 ✭✭
    Anything rather than Enphase. The Enphase systems are the only installed systems that we have that have almost nonstop service calls, & ongoing component failures. In the summertime especially.
    SMA, ABB & SolarEdge are much better choices.
  • skip21alskip21al Registered Users Posts: 9
    null

    Are you referring to the enphase 215 or the new 250s?
  • Ralph DayRalph Day Solar Expert Posts: 890 ✭✭✭✭
    I have an all enphase 10kw feed in tarriff system.  Installed in 2010, not one problem so far with the enphase 190's.  That is, once Enphase used the magic of the internet to reprogram the inverters to the upper design limit of 260vac (I think).  The line voltage was so high that they would drop in and out with a high voltage or frequency error.  Pushing the input voltage parameter up to the max (design limit) removed the problem.  

    Ralph
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