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Water, water everywhere....and a power update.

Discussion in 'Blog Archive' started by NigelM, Sep 13, 2013.

  1. NigelM

    NigelM Recovering Member

    Apr 3, 2011
    Northern Virginia
    blog start 2.jpg

    Continuing the story of our journey to go off-grid that started over here.

    Solar Hot Water

    Our local utility provider is pretty adamant that water heating contributes to approximately 28% of household power usage; that seems a little high to me but I'm guessing that they don't take into account households with electric vehicles. In any case, we got the option to apply for, and were granted, a $1,000 rebate for an additional solar water heater. We already have a solar heater for the master bathroom and with our move to full solar it seemed to make sense to add an extra heater for the kitchen and laundry and my daughters bathroom.

    Somehow it was kinda ironic seeing that big panel being hoisted up over our back-up generator:

    water roof.jpg

    I was surprised to learn that the panel only holds 1.6 gallons of water with another ~1.5 gallons in the pipes going from the garage to the roof. The collector is so efficient that the water is being heated by the sun to ~170F so it cycles quickly down into the insulated holding tank. We installed a thermal valve on water going to the kitchen to mix back in cold water and reduce the temperature to 140F, which should prevent any scalding accidents. The install went well and within 24hrs we were all connected and signed off by the code inspector:

    solar tank.jpg

    We'll recycle the old tank, which was in good condition but too small, back into the new stables so that we can have occasional hot water there.


    The total install cost for the new system was $5,500 minus the PoCo rebate. We are paying an average of $400 monthly for electricity right now and I estimate that hot water (directly and from the dishwasher/washing machines) accounts for 20-25% of our total bills. Given our elevation, popular wisdom here is that we should save at least 80% of the current electricity usage and that seems to have been borne out by watching our meter usage during the last two weeks. The worst case finances look like this:

    Install Cost = $5,500 - rebate $1,000 = Total cost $4,500

    Power costs $400 x water heating @ 20% = $80 x savings @ 80% = $64 monthly = Annual Savings of $768

    Amortization in 5.8 years.


    When an average solar water heater replaces a conventional electric water heater, the electricity saved over 20 years represents a reduction of more than 50 tons of greenhouse gases. That significantly reduces the environmental impact of our hot water activities.


    Stables Update

    We broke ground this week and withing minutes were greeted by a torrential rainstorm that came out of nowhere:

    photo 4.JPG

    This has been one of the wettest Florida summers in living memory and we are now the proud owners of a perfectly square 40' wading pool. Further work was suspended for 3 days to allow it to drain out naturally...

    photo 8.JPG

    However, the building hiatus did allow us to hold a site meeting at which we discovered that the building contractor is married to the niece of the solar engineer; it's really amazing how smooth and easy it was for these guys to work together and come up with ways to incorporate everything we want to do.

    Hydrogen Update

    My research work continued and following up on a comment on my previous post from Slackjaw I emailed Mike Stritzki in New Jersey who did the very same thing several years ago. Mike was kind enough to call me that same night and we had a great chat about all things green and what the true potential was. Mike was a real ground breaker and spent a fortune developing ideas to make them work. From that discussion I took away two key points:

    1. What I had in mind was absolutely possible to achieve today.
    2. Although the costs have been coming down, it could still push up to $200,000.

    Now the question is how fast do I expect costs to continue falling? We're definitely not looking at a Moore's Law situation but there's no sign of an amortization that makes financial sense. We have discussed that money shouldn't be the only determining factor so it makes sense to continue investigating what I expected would be a two year project as well as looking at battery development as an alternative.

    Battery Update

    I had initially battery backup as an off-grid alternative due to the ongoing environmental recycling costs and the problems involved with power draw spikes caused by a house with 3 HVAC systems (welcome to Florida!). When I wrote the first blog I had put out questions with various folks and was also interested in dpeilow's previous comment link that he found in the UK. Getting the guys together for a site visit today for a brainstorming turned up some new alternatives...

    Firstly, Mike Stitzki had told me that he avoids the power spikes by using a series of intuitive timers that prevent certain items items operating at the same time; turns out our electrician has a simple way of connecting our AC systems via contact switches to prevent them starting up simultaneously. One problem solved!

    Secondly, we have some new options on different types of batteries which have much longer expected life, better recycling opportunities and are deep cycle so that we could reduce the quantity of batteries needed. There are still two physical issues but both are manageable:

    1. Air-conditioned storage space. I have a 12' x 12' area in my existing barn that I can wall in and add a small AC unit to house the batteries and the inverters.
    2. Weight. Batteries at up to 100lb apiece means we'll need some custom racking and check the floor load capacity.

    Thirdly, there is a company here in Florida that builds custom batteries and where we might find Li-Ion alternatives. Conversations have started.

    Lastly, we got creative with evening out our loads between the various meters and came up with a plan to incorporate our existing generator as a final back stop for any unlikely apocalyptic battery failure. It'll be a manual switch that would still provide power for lighting, AC, refrigerators and water pump.

    More news to come on batteries in the next installment but there's no doubt it would be much more affordable and definitely short term attainable. There is a small level of added urgency as a battery back-up system would affect our choice of inverters versus those we would use for a longer-term hydrogen plan. The rebate program that takes place in October requires us to detail what we want to do and that's only 4 weeks away....
  2. gjunky

    gjunky Trifecta: Solar and both cars are EVs

    Mar 26, 2012
    Scottsdale, AZ
  3. Denarius

    Denarius Active Member

    Apr 27, 2013
    I tried googling for a bit, but could not find a solid numbers comparing the efficiency of compressed air vs hydrogen end to end. Anyone know the numbers?
  4. rolosrevenge

    rolosrevenge Dr. EVS

    Feb 7, 2009
    You know, if your backup generator is diesel and can run on used cooking oil, you could build up a large reserve of that potentially to further reduce your battery load. I think there are companies that sell home energy managers that can keep your total power usage lower. Based on the size of your compound, it could be a full on microgrid. There may be other grant opportunities for something like that, especially if you have some specific test objectives.
  5. AnOutsider

    AnOutsider S532 # XS27

    Apr 3, 2009
    Good read, Nigel, thanks. I hadn't heard that high of a number for water heaters, but we installed 2 solar units here (and got a state rebate). Unfortunately, I won't be able to tell how much they help since we had them from the beginning.

    Interesting re: @rolo's comment of the cooking oil generator. Could be a nice way to stay off grid and somewhat renewable.
  6. VolkerP

    VolkerP EU Model S P-37

    Jul 6, 2011
    Um I think we can forget Compressed Air Energy Storage (CAES) in a residential application. Air is not an ideal gas - helium would be much closer to that. What this means is you have energy losses compressing air in form of heat - that you can do little with - and you need heat when expanding the air again, or your apparatus will freeze to a stand still.

    There are only two CAES utilities in the world: one in Germany (Huntsdorf), and in McIntosh, Washington County, Alabama. Both use the compressed air in combination with burning natural gas to drive a turbine, compensating the temperature loss from expansion. Overall efficiency is 40% and 54% resp.

    Nigel hone your German skills, as the wikipedia articles on both plants are in German. :cool:
  7. constraint

    constraint Member

    Sep 17, 2012
    While not my area of expertise, I came across this ESS system that may be worth looking at. For 12 grand this ESS is 34kwh meaning $350 per kwh. This is the cheapest price I have ever seen for pack configuration. I am sure if you could tie a couple of these babies together they may be an suitable alternative to Lead Acid's issues.

    Looks like their website is screwed up and I can copy the URL and go back to that same spot.
    Go to
    Click on the top nav for "Lithium Batteries"
    Click on the "Energy Storage" link at the bottom of the page
    There should be a 34kwh ESS (3 week lead time) that will get you to the product page.

    • Nominal Capacity : 34 Kwhr
    • Battery Type : Lithium Iron Phosphate
    • Battery Voltage : 48 Volt DC
    • Operating Voltage: 42 Vdc to 60 Vdc
    • Cycle Life 3000 Cycles
    • Charge Voltage: 52.5 Vdc Bulk Charge | 57.0 Vdc Absorption Charge | 55 Vdc Float Charge
    • Discharge Voltage: 45 Vdc Max
    • Max Discharge Current : 500 amps at 80% DOD | 1000 Amps at 50% DOD
    • Max Charge Current : 700 Amps
    • Operating Temperature -45 deg C to 65 Deg C
    • Warranty : 5 Years Prorated
    • Dimensions : 44.25 X 43 X 34.50 inches ( L X W X H)
  8. jcstp

    jcstp Active Member

    Feb 7, 2011
  9. jcstp

    jcstp Active Member

    Feb 7, 2011
  10. nwdiver

    nwdiver Well-Known Member

    Feb 17, 2013
    United States
    Depending on your location it may be more economical to go with Solar PV + a heat pump hot water heater like the GE Geo Spring. You can get a Geo spring at Lowes for ~$1000 and it uses 70% less energy than a traditional hot water heater.
  11. adiggs

    adiggs Active Member

    Sep 25, 2012
    Portland, OR
    I appreciate that link to balqon - it looks like they are working on some of the things I would like to see happen, like BEV tractors and trucks. More reading there about the available home battery systems.

    Nigel - for backup power generation, have you done any research into a generator that burns something other than petrocarbons? One thought I had recently would be along the lines of a wood heated steam engine. The real purpose is to put the backup power source into a form that I could produce in a reasonably local fashion (such as through firewood).

    You are much further down the path than I am (heck, for me, I'm still in the wishing and wanting stage for the most part), but I have this idea that I would like to live in a fully electric/biomass (no petrocarbons) home that is off-grid. I guess the ultimate outcome I'd like to achieve is to have all of the modern conveniences and without petrocarbons.

    I also realize that I live in a climate where I'll spend more time worrying about heating in the winter, rather than cooling in the summer :)
  12. solarchad

    solarchad New Member

    Mar 23, 2014
    Saranac, Michigan
    NigelM, I have sent you a private message because I was not sure how to navigate this blog. In that message I explain that I build custom high voltage inverters that work at such voltages as Prius, Leaf and Tesla use in their main traction batteries. These inverters can be built in any capacity from 4 kw to 40 kw with 120 and 240 a.c. output at 167 amps a.c.(40KW) and surges to 80 KW! I have been designing and installing high voltage OFF GRID Home and Business Systems since 1982. solarchad
  13. MBS

    MBS Member

    Feb 5, 2015
    Tempe, AZ
    Nigel - Just curious how you are doing now well into your second year "off the grid." I went solar about a year ago, but sitting smack dab in the center of a metro area of 5m folks, we are still connected to the grid. LOVE my solar and am looking at other sustainable alternatives. BTW, I have also have a business in Utah and we made a variety of sustainable choices to keep things within our little 5 acre piece of land.

    Peace brother,

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