Comparing Geo to Solar PV

Discussion in 'General Discussions' started by Palace GeoThermal, Feb 19, 2011.

  1. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    The $16,800 was just for drilling at a cost of $14 /ft.

    I guess we really should add in the cost of the heat pump since the solar system is a complete package.
  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Here it is. Tell me what you think

    Last edited: Feb 21, 2011
  3. Looby

    Looby Member Forum Leader

    I like it! ...uhh, except for one glaring-but-common error:

    "kilowatts per year" is dimensional nonsense.

    The correct units are "kilowatt-hours per year."

    Last edited: Feb 21, 2011
  4. Designer_Mike

    Designer_Mike Member

    I started on the other end

    I started on the other end.
    We installed a 10.12kW solar PV system in November.
    Similar to others, our system cost about $60K and about 50% was covered by incentives.

    PVWatts is the place to figure out how much you'd get out of an array of panels.
    We have (44) 230watt panels. I think they cover about 840 sq feet of my roof.
    Last week I had one day production of 54 kWhr and our target production average should be slightly over 1000 kWhr per month but if I'm breaking 50kwhr in February, I'm hoping for more!
    Using those numbers, I SHOULD generate over 12,000 Kw-hr for the year

    My next step is completion of Solar water heating system to take that electricity hog water heater off the system. This is actually the biggest bang for the buck>> Water heating panels run ~85% efficiency compared to ~18% from PV panels. It makes no sense to generate electricity with 18% efficient panels only to heat water. Initial calcs show I use about 350 sq ft of panel just to heat my water by electricity from PV panels but if I heat the water directly, I can use less than 90 sq feet of water heater panel.

    The geothermal heat pump will hopefully get me somewhat close to net-zero. I may need to add more PV panels and replace some windows but I'm keeping my fingers crossed.

    Theoretically, you could heat water with solar and circulate that through a heating system for the house but it would take a tremendous amount of panels to harvest enough BTU in the dead of winter and they would be useless in the summer while PV panels will power the heat pump year round and the power grid is nothing but a huge battery for me.

    I'm just running the numbers to see how many kW-hr of electricity it will take to heat the house with the heat pump.
    I have three years of oil usage to know how many BTU it will take and I know that the cooling from the heat pump will be much more efficient than my air-source compressor unit....but the cooling numbers are a bit harder to calculate since I don't have any hard usage numbers to plug into the spreadsheet.
  5. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Thanks for saving me from myself
  6. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    That comparison is not entirely fair

    (1st of all - the proper unit is kiloWatt-hour)

    The energy the geo extracts is thermal. The energy a PV array converts and outputs is electrical. Subjectively speaking, electricity is a higher grade, more versatile form of energy to us in our homes. Not too many of us would be content to have the Btu equivalent in coal piled up next to the electricity meter.

    I don't know but I strongly suspect that a solar thermal array of equivalent capacity could be had for much less than the geo system. Of course it's not as versatile at delivering the Btus - sun's gotta shine.

    The best of all worlds would be just enough solar PV to power the geo system (via using the grid on a net zero basis).
  7. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I stepped away from this thread for some steak and beer and was beaten to the punch.
  8. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I agree that this is an apples and oranges comparison. I put this together to show people when when they question the cost of a geo system.
  9. grist for the mill...

    What is typically left out of ROI analysis by PV folks is verifiable life cycle costs. Degradation of panels, life of inverter and batteries if used all have a short life at out of the box efficiencies.

    If the consumer views geo vs solar PV then they don't understand the difference between supply side vs demand side energy usage management.

    Installing PV in a building without first maximizing envelope performance and HVAC energy efficiency(geo) is a poor use of public and private resources.

    PV has a place but only after sound demand side energy management efforts are included in the project.
    Last edited: Feb 22, 2011
  10. arkieoscar

    arkieoscar Member

    Grid tie solar

    Go here, input your location, etc. and you have a good idea of what you can produce for your area on a daily, monthly or yearly basis.
    PVWATTS v. 1
    Just like geo, solar installs and total costs will vary with the area so it's hard to use a rule of thumb on it. For a sunny, southern location ROI would be much different than some other locations. It's kind of ironic that people who make the same case for geo would dismiss another technology with the same tired arguments they rail against.
  11. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I think I know you from another planet. I agree there are very productive systems available to get the same goal. Save the space ship. I think it was Kurt Vonnegut, (SP), said something about the planet's immune system having a problem with mankind.

    Do you have a space guys program?

    I say things that only the voice in my head hears like solar thermal. Still those numbers are short of a free lunch for heat.

  12. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    While you may have to factor in life cycle costs for solar PV, you must also factor SREC's or Solar Renewable Energy Credits which can now be sold in the residential market. This significantly reduces the ROI on solar PV systems. Don't get me wrong, geothermal still will make the most sense, but the numbers will not be skewed apart by the same distance.
  13. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Thanks for the input on ROI.

    I will sell that $12,000.00 hot water tank, and by then may need an installer.

  14. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    PV panels last decades; many are warranted to produce 90% rated power for 20-25 years. A well-designed, cooled and installed inverter ought to be similarly moving parts.

    Batteries are an Achilles heel - pricey, inefficient, high maintenance, and shorter-lived.

    Net metering via the grid is THE way to go unless you and the grid are far apart.
  15. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Two words, solar thermal.
    Last edited: Feb 22, 2011
  16. griffin 6

    griffin 6 New Member


    If you can install a geo unit you can install solar , considering it is about 10 times easyer. Go to sun electric in arizona or florida. buy a pallet 20 solar panels for around 7200.00. Go to sunnyboy or fronius web sight use there config tool . figure out what inverter you like best. You can get 1 on ebay for half of what they sell for. 20 solar panels is about 4k. I would do solar before wind. solar installers are ripping people off in a bad way. I dont want to slam all of them though as im sure there are good ones. just not around here.
    Last edited: Feb 24, 2011
  17. Designer_Mike

    Designer_Mike Member

    Good luck trying to get the utility company to approve a DIY solar project or explaining to the insurance company why your house is now a pile of ashes because you tried to install a solar PV system.
    It is NOT something to mess with. If not done correctly, BAD things will happen.

    IF you are a licensed electrician, get the proper permits and have experience with high voltage DC go for it.

    The panels produce DC current. Wiring 500V of DC power to an inverter live is not something to be taken lightly. There is no way to shut the power off from the panels down to the disconnect switch.

    I have a friend that's an electrician and he wouldn't do it since he never messes with DC.
    The experienced electrician that wired my system politely asked me to leave him alone so he could concentrate on what he was doing and not kill himself.
  18. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Solar thermal

    Uses water not electrons.
  19. griffin 6

    griffin 6 New Member

    mike if your panels are ul and your inverter is ul. any local electr can inspect your work . you get the laws and codes in your area and you talk to your utility company. ,, my utility company is great. . Its pretty dam simple. I ground mounted mine. becouse we get alot of snow here.. I installed 2 systems 1 is 4 k the other is 3 . and i have 2 windmills. . my total cost on both systems is14 thou. Sun electric will give you a picture design. for free. doesnt get any easyer then that. My first install took 1 day. . Almost all towns have the codes they print out in about 5 seconds. . everyone is really nice about helping a guy. . just like the folks on here and geo. my geo worked great when it was 17 below and i did not run my heat strips... there was 10 times more work with my diy geo.
  20. griffin 6

    griffin 6 New Member

    also .the guys on here are not your everyday run of the mill factory or office workers. These guys know there shit and are very well rounded.
    Last edited: Feb 25, 2011

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