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Going Off Grid - Powering house and cars purely with renewable energy

Discussion in 'Blog Archive' started by NigelM, Aug 28, 2013.

  1. NigelM

    NigelM Recovering Member

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    This is my first attempt at a blog and one that will likely stretch over the next 18 months or so as I find my way through this project. During that time I'm going to see if it's possible to not only install solar power but also to get to a point where we can disconnect from the grid completely.

    Background

    At our previous house we installed solar PV panels with micro-inverters on a net-zero system. The full story was outlined in a TMC post about 2 years back and you can still find that here. At the time micro-inverters were the best option for us given the limited space we had and my obsessive desire to keep an eye on each individual panel.


    The net-zero system basically means that you spec the size of the system to cover your total power requirements and during daylight your meter runs backwards as you return power to the grid; the meter then runs forwards as you draw power from the grid at night. Hopefully, if you got your sums right you’ll net out owing the utility company zero.

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    Since that install we have moved house and technology has moved forward so I’m starting over on our new house with a different set of ambitions and circumstances.

    Ambition

    We now drive two electric cars, the Tesla Roadster and Model S, with a reservation on Model X (I’m not sure I can justify 3 cars, so the Roadster will likely go when Model X arrives) and I’d really like them to be powered totally by renewable natural resources. I want all our energy requirements to be covered by our PV system but ideally we’ll generate and store our own power to disconnect from the grid completely. I’ve investigated various alternatives for battery storage/back-up but didn’t find an option without replacement and recycling issues; however, as technology advances it’s looking like we have options to disconnect from the grid completely without fossil fuels and that is too good an opportunity to pass up.

    Current Set-Up

    Living in SW Florida we average 304 days of sunshine per year. Our new house is kind of colonial style but has a roof that could perhaps be described as a higgledy-piggledy; not conducive to nice rows of PV panels.

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    We have a barn/shop that has a perfect, sloping roof but less than ideal elevation and we have plenty of space with around 10 acres of pastures. We are planning on moving horses onto our property (my daughter rides competitively) and that’s going to require building stables (this becomes important).

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    The house is a fair size and we run 3 AC systems basically year round as well as pool pumps etc. so total electricity costs are around $5,400 annually. We currently have solar heating for the swimming pool and a roof based solar water heater for the bathrooms.

    pool solar.JPG

    Our water supply comes from an underground aquifer, is unlimited, and is free (this also becomes important).

    PoCo Meters & Rebates

    An oddity of our set-up is that we have two electricity meters. One residential meter for the main house and one business meter on the existing barn with load split between the two. Coincidentally this offers us the chance of substantial rebates which we could not otherwise access. We’re going to need to balance the loads between the 3 fuse boxes and 2 meters in order to gain maximum benefit but the cost of the electrical work will easily be outstripped by the rebates gained.

    Untitled.jpg

    As we have to bore some lines from the new stable and the existing barn/shop to the house we’ll just put an extra conduit at the same time and that will help keep those costs down.

    There are no state subsidies or rebates programs in Florida; but there has been a long-term rebate program operated by Florida Power & Light (FPL) our local utility provider. The next round of the rebate lottery takes place in October and grants rebates of up to $20,000 for residential systems and up to $50,000 for commercial systems. Needless to say, there were big smiles around here when we discovered that we are eligible for both grants due to our dual meter set-up.

    The Idea


    1. Generate power from a solar PV system
    2. Use that energy to separate hydrogen from water via electrolysis
    3. Use a hydrogen fuel cell to power the house

    This graphic which I’ve borrowed from Verde LLC demonstrates the idea nicely:

    Untitled.jpg

    If we size our PV system appropriately we will have the ability to generate excess hydrogen during daylight hours and then store it to use it at night and during low-light periods. Residential hydrogen generation and fuel cell use are at early stages of development but we’re already in contact with 3-4 different potential vendors; however, the FPL rebate plan requires us to run a net-zero connection for at least a year prior to going off grid completely, so we have plenty of time to explore this.

    First Steps, First

    Water coming out of the ground was not really suitable for drinking; it wouldn’t kill you or even make you sick but there were high levels of iron, a light sulphurous smell and very hard water which left water spots and stains on every surface.

    I installed an Iron Curtain system from Hellenbrand to deal with the iron and sulphur, a chlorinator to kill the bugs, carbon filters to remove the chlorine again, a water softener and finally a Sterlight UV tube to kill anything that might have escaped the rest of my firewall. End result is water that is purer than Evian, crystal clear, no stains, no calcification and a happy wife. It’s also perfect for electrolysis.

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    Total cost for this was $5,600 but I’d have installed that anyway as we’ll recoup the savings on more efficient laundry and dishwashers as well as much longer life for those and other appliances. I’m also finally able to wash the Teslas at home without leaving hard water spots all over them.

    Minor Aside

    Having improved the water quality 1000%, I’m installing a second solar water heater this week which will provide hot water to the kitchen and laundry room.


    The Stables

    As we were planning the construction of our new stables, the architect asked what the elevation should be and it occurred to me that we had an opportunity to site it perfectly for maximum power generation for a PV system. I brought in a solar expert to look at the location and we’ve chosen an ideal spot, close to the existing barn and well away from trees.

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    Working with the architect we increased the pitch of the roof slightly and sized the rafters to be 2”x8” with 48” spacing to make it ideal for the PV install. Being able to specify things down to fine detail will also make later installs cheaper and faster.

    IMG_0135.JPG

    All permits are now in and we expect to break ground in about 10-14 days. It’s masonry construction so preparation and the foundation will take two weeks, the walls another two and then two weeks for the roof. Once the roof is up, PV installation can commence, even while interior finishing and fitting takes place.

    Solar PV Panels

    Having reviewed available products, we’re almost certainly going with AXITEC 60 cell, polycrystalline modules. These German panels have a 12 year manufacturer’s warranty, guaranteed positive power tolerance and incredibly strong frames (this is hurricane country after all). They also guarantee 90% of the nominal performance for 15 years and 85% for 25 years on a linear scale.

    solarmodul-mehrwert-0d60fc5b.png

    The final size of the system will likely depend on exactly what rebates we can get our hands on in the FPL lottery but there will be an option to add more later if needed to support the hydrogen fuel cell concept.

    Inverters

    I mentioned earlier than technology has moved on since our previous install and we also have more space now. With a large barn/shop and a generous two car garage there’s plenty of room to locate a couple of large inverters.

    IMG_0129.JPG

    This definitely means a cheaper system/install over the micro-inverters but with the latest technological developments I will still be able to track and monitor system and module performance.

    I’ll blog more on the details of the PV Modules and the Inverters as we move forward. Costs for both are being worked on as I write, but I’m expecting something around the $100k level in total with around $70,000 in rebates. I’ll also write up a more detailed post on the total finances as it all starts to pan out.

    Florida is still a patchwork of small vendors when it comes to PV systems, no SolarCity here, so we’re likely to be using RegionSolar based in Sarasota which also happens to be owned and run by a personal friend.

    Hydrogen

    This is going to be a feature of follow-up blogs. Discussions are still preliminary but promising. The technology is there and the whole concept is feasible. One of the best examples is Verde LLC in Braintree, MA. However, we're also looking at Ballard, Horizon and ClearEdge.

    We have a few issues still to figure out with regard to load spikes e.g. when AC systems start up, and what options we have in managing load requirements for charging the cars.

    Watch this space....

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    :smile:
     
  2. doug

    doug Administrator / Head Moderator

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    Very cool. I'm particularly curious about the residential hydrogen system and how that works out. Several questions come to mind:

    1. What's the expected round trip efficiency?
    2. What's the energy storage capacity?
    3. Does the H2 get compressed?
    4. What's the physical size of the system?
    5. What's the expected lifetime of the fuel cell?
    6. How does this compare with a battery based system?
    7. How "green" is this compared to a net-zero system that uses the "grid" as the battery?

    Looking forward reading further installments!
     
  3. NigelM

    NigelM Recovering Member

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    Some if that is known and certain and some (a lot!) is up in the air pending developments:


    1. What's the expected round trip efficiency? Back of the envelope suggests anything from 40-75% Efficiency can increase to 80-85% if you recapture the heat (not that necessary in Florida unless we could come up with a way to heat water with it). The interesting things is that there seems enough potential for it to work.
    2. What's the energy storage capacity? Depends on weather studies. Theoretically we only need ~15hrs power back-up 95% of the time. We do have a whole house generator, which runs on propane, as storm back-up. Although I'd like the ideal to be zero fossil fuel usage the fallback plan would be the generator.
    3. Does the H2 get compressed? Technically easy and seems to be often incorporated into the electrolysis equipment.
    4. What's the physical size of the system? I'm told the hydrogen generator and fuel cell would be no bigger than 2 refrigerators side by side. For most folks that's big but I have spare space of 12'x12' in my existing barn and plenty of storage space.
    5. What's the expected lifetime of the fuel cell? Expected 25 years.
    6. How does this compare with a battery based system? I wanted to come back on batteries in a separate blog post. The issue is longevity of the batteries (3-5 years) and the need to recycle them. An open question is the re-use of e.g. Roadster batteries.
    7. How "green" is this compared to a net-zero system that uses the "grid" as the battery? Depends on your PoCo. Truth is that the stand-alone idea is always going to be more expensive that net-zero; but I'm not afraid of being an early adopter and as vendors realise there might be more of a residential market for this type of set up maybe cost/size will come down.
     
  4. AnOutsider

    AnOutsider S532 # XS27

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    Also interested in seeing how the fuel cell thing pans out. The longevity issue of batteries is a large reason we didn't go with it.
     
  5. zeron

    zeron Member

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    Why would you not just use the hydrogen/fuel cell setup for power at night and use the solar directly? I'm reminded of the "fool cell" comments...

    So essentially using the excess power over the day to create hydrogen for power at night and backup, but not take the efficiency hit all the time.

    (Also, of course, be very careful with hydrogen. It will not stay in those tanks forever, and at suitable concentration can be extremely dangerous. But I'm sure you have a handle on these safety things!)

    (Also, what kind of power output do fuel cells have these days? So many questions!)
     
  6. doug

    doug Administrator / Head Moderator

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    The "green" I meant was in terms of environmental impact. For example, if your system works (after the emissions associated with manufacture) you system should have zero CO2 emissions. But in the net-zero setup with the grid, did that help reduce your community's over all CO2 emissions? I guess it depends on the daytime versus night time grid energy mix.
     
  7. NigelM

    NigelM Recovering Member

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    That's exactly what I'd like to do; getting there is also going to mean finding suitable equipment so that the switching should be automatic and seamless.
     
  8. NigelM

    NigelM Recovering Member

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    I don't see the grid operating like a battery; the reason the PoCo operates these incentives is so that they don't have to increase capacity quite so fast and they can delay/avoid major step-costs. My daytime over-production will go into the grid but at night I'm pulling down power generated with whatever fuel the PoCo used. I guess I can claim zero CO2 emissions but it's actually a trade-off.

    I don't know if I'll succeed completely but I'll only be able to claim I'm truly CO2 free if the entire project works.
     
  9. Slackjaw

    Slackjaw Member

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    Nigel, very cool, thanks for writing it up, and I have to tip my hat to you for putting in the effort with this project. Thanks on behalf of the planet. We're building a house (in New Jersey) and I was hoping to go solar but it is completely walled in by 150 ft trees. We decided to follow the mantra "PS trumps PV" and not cut down trees to make sunlight. Since we're building from scratch we have gone with geothermal heat/cooling. These days you have to be a bit nuts to do that because natural gas is so cheap thanks to the accursed Shale Revolution; it will never pay for itself (the system will cost about $70,000 *after* a 30% tax credit). As it happens, I am a bit nuts.

    Also related - sure you know about this one already but might be of interest to other readers - there's a house here in NJ where the guy has tried to do this and has got a lot of press about it. I've driven past his house a few times while out joyriding in the Roadster, and almost requested a tour, but he drives a hydrogen car and I didn't want things to get, y'know ...confrontational. His project is well documented: Inside the Solar-Hydrogen House: No More Power Bills--Ever: Scientific American .

    It does strike me that an EV-to-Grid system might be more efficient round trip wise than using hydrogen, but just the load on the car batteries would probably be enough to put people off. And AFAIK Tesla has no plans for EV2G. Just a thought.
     
  10. davecolene0606

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    Hey Nigel,
    I am in pursuit of similar arrangements across the state. 2 questions, I am looking at Sunpower panels (X21). I now have Sharp panels, and although the SPWR panels are a little pricey it appears that their warranty is superior and the efficiency helps me with space constraints. SPWR also claims more power in hot conditions. Have you looked at them? and Your thoughts?

    Also, any feedback (credible) as to if or when TSLA might do the system to,utilize the cars as a back up/capacitor type supplement ala what Nissan has done? Sitting with 145kw of batteries in the garage already payed for in combination with the Hyd fuel cell solution could be the sweet spot to take slack for power spikes and temp back up.

    And, you pursued 4x8", was it just wind load or weight as well?

    Cheers
    Dave
     
  11. NigelM

    NigelM Recovering Member

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    You might find it interesting to talk to ModelS1079; Jim has a geothermal system that he loves.

    Thanks for the link also.
     
  12. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I'll be watching for the future installments - interesting project, Nigel!

    Also:
    Technical term?
     
  13. NigelM

    NigelM Recovering Member

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    The guarantees between SPWR X21 and the Axitec look virtually identical. the SPWR ones do seem to come out a little pricier though. I read up and couldn't find anything about performance in hot conditions. You're probably aware that PV works optimally with plenty of light but not to hot, so if there's something that can be substantiated I'll take a look; we haven't made a final decision on panels yet.

    I have no insight as to Tesla's plans, if any, to allow PV2G. What I have been thinking about is direct DC charging and how that might work; I'm far from an expert and there's several threads on TMC and the TM forums which make it look tough/expensive to do. As technology moves on that may get more feasible.

    We're going with 2"x8"s on the new building for both wind and load weight; 2"x6" would have been acceptable for permitting but the builder switched it up for me at no extra cost so it was a no-brainer decision.
     
  14. dpeilow

    dpeilow Moderator

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    I'm surprised you are expecting 3-5 years lifetime from batteries. I calculated 13 years from a set of carbon electrode lead acids for a similar application I was designing.

    http://www.tayna.co.uk/product-detail/ElecsolAGMBrochure.pdf


    Also, I've never heard of a fuel cell lasting anywhere like 25 years.
     
  15. wycolo

    wycolo Active Member

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    Interesting project but my eyes glazed over when I read about the 2 meters and then about the rebates. Gonna be very difficult to remove these two major skewings from the economics but we'll try. It's our job, not yours! Good luck with getting it all going.
    --
     
  16. tander

    tander Member

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    Nigel,

    Really interesting to see someone doing this. Have you looked into doing a battery storage system instead of going by grid at night? Seems like that will be the natural direction for the industry to go?
     
  17. tander

    tander Member

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    Also, I don't mean to pry I'm trying to wrap my head around the project, but why does the barn have a business meter?
     
  18. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Because much of your electrical load is for air conditioning, have you considered ice storage to store the the energy that you make while the sun shines for cooling other times of day. This may be easier, simpler, and/or less expensive than hydrogen storage.

    Most of these articles talk about making ice at night when rates are cheap, but for you it will be make ice when you have solar power.

    Ice storage air conditioning - Wikipedia, the free encyclopedia
    Air Conditioning With Ice | GreenBuildingAdvisor.com
    Ice Bear Energy Storage System | Distributed Energy Storage
     
  19. J&R Housing

    J&R Housing New Member

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    Yesterday I stood in the spot provided for the charging of 6 Tesla Model S cars from nearby I 90 at Worthington MN. The construction was very neat and finished with the only hint that it is new, being the need of charging cords and the missing covers on 5 of the 6 units. The site is located in the parking lot of the Ground Round with other eating options nearby as well as lodging and shopping. 12/1/13 J&R Housing
     
  20. Lindsay

    Lindsay New Member

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    Hi my name is Lindsay ,

    I am a student at College of the Canyons and part of the broadcast journalism department, and our local station Cougar News. I am saving up for a Tesla because they are amazing cars.

    My friend Leif and I are passionate about the environment and would like to do a story featuring a Tesla owner and see how it is affected your transportation, gas payments, and your carbon footprint.

    Our school is located in Santa Clarita but we are able to travel to anywhere in the L.A area.

    Here is our schools website.

    http://cougarnews.com/

    Please contact me ASAP if you are interested in being interviewed.

    I didn't know how to make a new blog post, so I apologize that I had to post on this.

    [email protected]

    Thank you ☺
     

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