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  • Hello from Mid MO

    I'm a retired electrical engineer with a 40 year career working for a large investor owned electric & gas utility. All of my work was in distribution and transmission.

    For years I've had interest in pv systems however as with a lot of people, I've never found the system economically feasible. 30 years ago I built a solar water heater for a small swimming pool which worked well. I have two 100 watt panels on my shop I use for battery charging and topping off batteries on lawn and garden equipment. Some of this equipment doesn't get used on a regular basis so I've it cheaper to keep the batteries charged than to replace them. I'm presently building a small 12v pv system with a 22 watt panel, 8 amp controller and 35ah battery to power a string of led lights mounted in colored glass globes on our deck.

    Our present home has a geothermal heat pump and is surrounded by trees so solar is not an option. We are considering building a new smaller home and if we do it will have a metal roof with pv panels.

  • #2
    Welcome to the neighborhood. Sounds like understanding the electrical and the POCO billing ends of the process are manageable for you. How much do you know about the solar resource end of the process ?

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    • #3
      We have very similar backgrounds. I certainly hope your future home does not go off-grid, interactive OK, but no off-grid. Reason is simple and you will understand. Battery systems have negative EROI. That means any power from batteries will cost you many times more than you can buy from the POCO, and with a 10 to 50% negative EROI also means you are producing 2 to 5 times more emissions than the POCO are for a given unit of energy.

      There was an interesting report last year that got swept under the covers in the USA on Electric Vehicles. The Swedes are about the most environmentally conscious country in the world second on to Iceland. The Swedish government got a nasty surprise when they commissioned the Swedish Transport Administration and the Swedish Energy Agency to investigate litium-ion batteries climate impact from a life cycle perspective. What they found out was quite a shock. EV manufacturing of the cars and batteries are extremely heavy polluters and coupled with emissions from generating electricity to charge the batteries, an EV produces more emissions from cradle to grave than gas guzzlers. They found out what we already know about lead acid batteries, even lithium-ion batteries have negative EROI. All those folks who have bought EV and those that wil buy an EV and lying to themselves and in denial. They concluded the only way to make an EV emission free and economical is if the vehicles, batteries, and charging is done with nuclear energy. Sadly if we had nuclear power, there would be no need for EV or solar. Power would be cheap and plentiful with a fuel with proven reserves of 10,000 to 1,000,000 years depending on whose data you want to use.

      Now Jeff will be here shortly to dispute the report, but he works for Tesla so is extremely biased and wants the story buried. Here is the link to the study.
      Last edited by Sunking; 12-11-2017, 08:28 PM.
      MSEE, PE

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      • #4
        Originally posted by MegaWatt View Post
        For years I've had interest in pv systems however as with a lot of people, I've never found the system economically feasible.
        Welcome to the forum. I hope that your power consumption doesn't match your Forum name

        Cost has certainly been a problem in the past but as the prices of panels, batteries, inverters and electronics in general keeps coming down it is making economic sense for more and more to consider either grid-connect or fully off-grid systems.

        In our case it would have cost us at least AU$100,000 to get grid power to our property. The system I designed and installed seven years ago cost around AU$11,000. The same system today would cost around AU$8,000. I have also installed a system for a friend at the same time. In this case it was going to cost ~AU$5,000 to get grid power to their house. Due to their low power needs of around 5kWh/day and the high cost of power here (currently ~AU$0.30/kWh) and high supply charge of ~AU$1.00 per day it makes going off-grid viable. Assuming that their system will last ten years (which is conservative) I get a daily cost of their power of ~AU$3.00/day. If they has connected to grid power their costs would have been ~AU$2.50/day plus the ~AU$5,000 that they would have had to pay to connect to the grid, if we amortise that over ten years we get a cost of ~AU$4.50/day.

        In Australia I have seen costings of the Tesla PowerWall 2 coming it at around AU$0.23/kWh. Double this to add all the other equipment necessary to make an off-grid power system and you end up with a cost ~AU$0.50/kWh.

        Simon

        Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
        BMS - Homemade Battery logger github.com/simat/BatteryMonitor/wiki
        Latronics 4kW Inverter, homemade MPPT controller
        Off-Grid LFP(LiFePO4) system since April 2013

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        • #5
          Originally posted by Sunking View Post
          Now Jeff will be here shortly to dispute the report, but he works for Tesla so is extremely biased and wants the story buried. Here is the link to the study.
          Thanks for the link to that very interesting study. I am always interested in good quality information like this.

          I noticed that in the summary of the report that it states
          Energy use for battery manufacturing with current technology is about 350-650MJ/kWh battery.
          If we say 500MJ, unless I have miscalculated or misunderstood this equates to ~140kWh. From the data I have seen you should be able to cycle at least 3000kWh through a 1kWh lithium ion battery of the sort that you would use for off-grid or grid tied use. Doesn't this result in an EORI (Energy Delivered/Energy Required to deliver that Energy) of ~21.4?

          Originally posted by Sunking View Post
          They concluded the only way to make an EV emission free and economical is if the vehicles, batteries, and charging is done with nuclear energy.
          Surely the same would be true if all the energy is produced by emission free renewable energy like solar, wind and hydro. South Australia has got to sourcing over 50% of its electricity from wind and solar, this will only continue t increase.

          Simon

          Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
          BMS - Homemade Battery logger github.com/simat/BatteryMonitor/wiki
          Latronics 4kW Inverter, homemade MPPT controller
          Last edited by karrak; 12-12-2017, 02:37 AM.
          Off-Grid LFP(LiFePO4) system since April 2013

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          • #6
            hello I am new to this forum

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