question

Got a question, I heat my house with a wood fired boiler, I also have a 2panel hot water(domestic) thing going on(Thremo Dynamics). On sunny days there is an abundance of hot water for domestic use.
My question is: can I put a coil in my solar storage tank and run it into my boiler domestic inlet to "preheat" the boiler water? or is this just a farout idea?

Thanks,
Dave

Comments

  • System2
    System2 Posts: 6,290 admin
    Re: In hot water

    Can pool heater panels be used for solar hot water? I almost purchased 5 new panels on ebay for $100 but was out bid by $2.

    $4000 seems a bit high for a kit?
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: In hot water

    Pool heaters are not made for domestic hotwater, they are intended to only raise a few degrees over ambient ( no insulation ) and are designed for low pressure, pools are in the 15-25 psi range where street pressure is 60-80 psi
  • System2
    System2 Posts: 6,290 admin
    Re: In hot water
    Pool heaters are not made for domestic hotwater, they are intended to only raise a few degrees over ambient ( no insulation ) and are designed for low pressure, pools are in the 15-25 psi range where street pressure is 60-80 psi

    Well then I am glad I did not win the bid as I would of then had to install a pool!!!! :p

    So other then the $4000 systems is there a cheaper DIY way or is it just not worth the trouble?

    I am very GREEN (new) to this whole thing.

    I just purchased an 80watt solar panel and I am going to try some 12volt things around the house for starters and then grow from there.

    My house is all electric so with the hot water heater being a a big part of the electric bill I thought after getting all my 12 electronic items over to solar/battery power I would try and get my hot water heat a bit more energy efficient.

    Also my current 80 gallon heater is about 20 years old and could go any day so I thought now would be a good time to go green with it.

    Thoughts?
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: question

    The best bang for you buck to reduce costs... 1. Conservation, 2. Conservation, 3. Probably Solar Hot Water (especially if electric heat now), 4. Solar Grid Tied electric power.

    The nice thing about solar hot water--it is relatively inexpensive to install and the panels are relatively small (because of their high efficiency at gathering heat). Bad thing (from my point of view), need hot water tanks for storage (rough rule of thumb is 20 gallons per person per day), plumbing, and maintenance issues (freezes, air locks, pump failures, corrosion).

    The nice thing about Grid Tied solar--virtually zero maintenance (you can clean your panels for a 5-10% increase in power--I have pretty much given up on regular cleanings at they are on a second story roof and it is a pain to get a ladder up for cleaning--plus as I get older, I found I have a new fear of heights). Bad thing--costly installation, pain with utility and PUC rules. Panels are large because they are only 12% efficient or so.

    The 80 Watt panel is fun to experiment with and learn about solar, charge controllers, and batteries... But in real life, it is probably going to cost you more in money than it can ever save (batteries are large and expensive, should be recycled and changed every 3-10 years).

    Start with your largest consumer of power... Electric Hot Water Heater, heating and A/C, electric oven, lighting, "standby loads" (computers, printers, TVs, etc.), down to unplugging cell phone chargers when not needed...

    The above is in rough order of importance. I.e., don't drive your wife nuts by bugging her about forgetting to unplug the cell phone charger when you have an electric hot water heater and a full flow shower head in the home.

    For the smaller appliances, a kill-a-watt meter is a great tool (120 VAC, 15 amps). For larger appliances, you can do estimates (water heater costs), or what I have done before is get an old utility meter and wire that into the heavy loads and let it run for a week or a month to see how much power is used.

    The electric hot water heaters are already pretty energy efficient--and a new one will just have a little bit more insulation and shave another couple percentage points off the energy bill.

    Converting to natural gas or propane would be a stop gap change to reduce costs... Or, get a good electric hot water heater either with an internal heat exchanger or a open loop type (if you are in an area that does not get freezing temperatures) and add solar.

    Configure it so that you can turn off the lower element in the summer and the solar panels will provide the heat. The upper element is still there to give you hot water even when it has been cloudy or all of the day's solar hot water has been used up.

    Solar Guppy recommended SolarRoofs.com as they have well thought out kits for home installation.

    Since you have electric hot water--your conversion to solar hot water should be a natural. (for those of us with gas, the issues are a bit more complex to add a second demand heater or something else).

    There have been a couple threads in the last few days asking about solar thermal hot water--and we have posted links to a few threads and products to read through... A good place to start.

    I think you will be best served by looking at your home as a "system" and address the major issues in a well thought out way... Everyone is different and lives in different locations. If you have A/C, a geothermal heat pump with attached water heating system would be a great way to go--but if you don't have A/C, maybe not. etc...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    Re: question

    Dave I wouldn't mess with trying to preheat your boiler water, it can get messy and dangerous. If you have extra hot water you might try a simple radiator type setup with domestic hot water. Heck even something as simple as a 1/2 inch copper coil at 25-100 feet, a small circulation pump and a fan will pull out a lot of heat.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • System2
    System2 Posts: 6,290 admin
    Re: question

    Thanks for the reply Bill. I actually have been reading some of those resent threads, and I have been to solarroofs.com and I guess the $4000 system for heat (with 80 gallon tank) is the best bang for the buck out there?

    I am outside of Philadelphia PA so I need a freeze proof system.

    My roof is low and has a low pitch so I do not mind getting up on it for cleaning or even installing the systems.

    I actually have recently told my one girlfriend (all my other girlfriends have there own houses ;)) that she will be needing to bring in the car cell phone charger as that is what the 12 volt system is going to be used for, as the 80watt panel is just going to be used to supply power to 12 volt devices like cell phone charges and all my other electronic devices I have in the house that run on 12 volt adapters. I wont be using an inverter for AC power from the panel or batteries.

    Speaking of batteries... what size would be recommended for my 80 watt panel and were is a good place to purchase them? Walmart perhaps?

    Like I said I am very green to this whole thing and I am reading as much as I can on these forums.

    And I agree 100% with you Bill on 1.) and 2.) and I do pretty good.

    I have about 90% of my lights as CFL's and I have off peak power option with First Energy and use things like the dishwasher on off peak hours.

    My electric bills are not terrible as I only have a 1600SQ foot house and may go up to $250 in a very cold month in winter. I currently do not have central AC and only use the baseboard heaters in rooms that need heat in the winter. I have been looking at getting AC but I am now waiting until I see what I can do with solar or perhaps a ground water source unit????

    The way things are currently going I feel that electric cost is going to start climbing and fast so I want to start somewhere and thus the 80watt panel with controller and get my 12 volt stuff off my electric bill and then go from there.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: question

    Well, using this link, it looks like you average about 4.5 kWhr per day (across the whole year)...

    If you wan to store power for up to three days, and not discharge the battery by more than 50% (for long life)--an average size battery would be:

    4.5 hours of sun per day * 80 watts * 0.6 (overall efficiency derating) * 3 * 1/50% = 1,286 watt*hr battery bank

    Or for a 12 volt battery,

    1,286 WH / 12 volts = 108 amp*hours worth of 12 volt storage battery(ies)

    This is all approximate--you probably would not want (or need) to go larger, and you could easily go to 1/3 the size and still be OK.

    Start with a standard wet cell storage battery--cheap and you can refile with distilled water when needed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: question
    BB. wrote: »
    Well, using this link, it looks like you average about 4.5 kWhr per day (across the whole year)...

    If you wan to store power for up to three days, and not discharge the battery by more than 50% (for long life)--an average size battery would be:

    4.5 hours of sun per day * 80 watts * 0.6 (overall efficiency derating) * 3 * 1/50% = 1,286 watt*hr battery bank

    Or for a 12 volt battery,

    1,286 WH / 12 volts = 108 amp*hours worth of 12 volt storage battery(ies)

    This is all approximate--you probably would not want (or need) to go larger, and you could easily go to 1/3 the size and still be OK.

    Start with a standard wet cell storage battery--cheap and you can refile with distilled water when needed.

    -Bill

    Those calculations are impressive but way over my head! :blush:

    Is that for all my energy needs or just for my 12 volt items as that is all I am going to start with.

    standard wet cell... like a car battery right? Those are cheap at walmart. I take it I should get one with the most watt/hr?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: question

    The battery size is based on what is reasonably expected to be output by your solar panel (average over the year)...

    You could also do the calculations based on the loads--but you have not supplied any numbers--so there is nothing I can do there.

    Basically, if the solar panel is too big (or the battery too small), you will loose energy, and possibly charge the battery too quickly. Also, you will not be able to take much power out of the battery before it becomes damaged (too deep of discharge for a lead acid battery will quickly kill it--weeks to months).

    If the solar panel is too small (or the battery too large), you will have a hard time completely charging the battery.

    So, the best is to aim for the happy medium where the battery is properly charged and damaged by too much load for its size.

    Power wise... The calculation is basically how much power times how long...

    So, for a 10 watt light running for 5 hours would be:

    10 watts * 5 hours = 50 Watt*hours of electricity used.

    And, it also works out:

    5 watts * 10 hours = 50 watt*hours of electricity used.

    Your 80 watt solar panel will give you about 120 watt*hours in the winter and 240 watt*hours in the summer of useful energy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    Re: question

    Boiler pre-heat? If you have the capacity, sure, no problem.

    http://www.stsscoinc.com/

    has some options.
  • System2
    System2 Posts: 6,290 admin
    Re: question
    BB. wrote: »
    The battery size is based on what is reasonably expected to be output by your solar panel (average over the year)...

    You could also do the calculations based on the loads--but you have not supplied any numbers--so there is nothing I can do there.

    Basically, if the solar panel is too big (or the battery too small), you will loose energy, and possibly charge the battery too quickly. Also, you will not be able to take much power out of the battery before it becomes damaged (too deep of discharge for a lead acid battery will quickly kill it--weeks to months).

    If the solar panel is too small (or the battery too large), you will have a hard time completely charging the battery.

    So, the best is to aim for the happy medium where the battery is properly charged and damaged by too much load for its size.

    Power wise... The calculation is basically how much power times how long...

    So, for a 10 watt light running for 5 hours would be:

    10 watts * 5 hours = 50 Watt*hours of electricity used.

    And, it also works out:

    5 watts * 10 hours = 50 watt*hours of electricity used.

    Your 80 watt solar panel will give you about 120 watt*hours in the winter and 240 watt*hours in the summer of useful energy.

    -Bill

    Makes perfect sense. Thank you Bill.

    I will have to look at all my 12 volt equipment and see if I can figure out the watts needed and go from there.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: question
    standard wet cell... like a car battery right? Those are cheap at walmart.

    Your best bet is the generic Deep Cycle battery, around $80 or 90. They make a zillion of them for boats and they should last you 4 years. They have about 90AH capacity, caps that you remove to add DISTILLED water, and usually a combination of terminal types.

    Then you also need a charge controller to manage charging it, and a couple of cig lighter outlets to plug your cell phone into.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2
    System2 Posts: 6,290 admin
    Re: question
    mike90045 wrote: »
    Your best bet is the generic Deep Cycle battery, around $80 or 90. They make a zillion of them for boats and they should last you 4 years. They have about 90AH capacity, caps that you remove to add DISTILLED water, and usually a combination of terminal types.

    Then you also need a charge controller to manage charging it, and a couple of cig lighter outlets to plug your cell phone into.

    Thanks Mike. Actually the panel I bought (from fleebay) comes with some sort of a controller... here is the actual link to what I purchased: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170211546820&ssPageName=ADME:B:EOIBSA:US:1123
    It should be arriving in the next few days.

    I was thinking about running some new wire to all of my phone jack locations and replacing the jacks with some sort of 12 volt banana plug jacks? and then from there you could plug in a cig lighter adapter or anything else you might want to connect to use the 12 volts. What kind of wire would one use for a 12 volt outlet / outlets through out your house?

    Also do they make some sort of step down/up transformer for 12 dc so that if say your device needs 3.5 or 6 volts DC or 22 volts DC you can adjust it? Or would you have to charge 24 volt batteries and use a var. resistor and a volt meter to get what you want by adjusting the variable resistor?

    I guess if all goes well with getting some 12 volt gear running on a small system I could add a second then third panel and more batteries and convert other things like lights in the house and ceiling fans to 12 volt ones and power them off the growing system? Make sense?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: question

    It's real easy to get in to trouble with 12V banana jacks. Seems easy to hook up, and then, one day, somebody hooks something up backwards. Best to have a charger shed or something.
    You've hit upon a major problem with DC, it's difficult to get the right voltage for everything. Using a resistor works, but wastes power. You don't want to start running 12V thru the house, because it likely will violate many fire codes, and IF there is a fire, insurance won't pay.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2
    System2 Posts: 6,290 admin
    Re: question
    mike90045 wrote: »
    It's real easy to get in to trouble with 12V banana jacks. Seems easy to hook up, and then, one day, somebody hooks something up backwards. Best to have a charger shed or something.
    You've hit upon a major problem with DC, it's difficult to get the right voltage for everything. Using a resistor works, but wastes power. You don't want to start running 12V thru the house, because it likely will violate many fire codes, and IF there is a fire, insurance won't pay.

    Very good points.

    I think I will just install one cig lighter outlet in the kitchen.

    For my theater devices I will wire direct to 12 volts. I guess you dont need surge protectors for 12 systems????
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: question

    Many folks use 120/240 VAC twist lock type connectors from the local hardware store... More reliable than Cig. plugs, and safer too (if you have kids, they can get fingers and metal objects into the Cig. outlet).

    Regarding surge protection--actually, you still need fuses, and while it would be nice to have surge protection, on low voltage DC, it is pretty difficult to achieve.

    If you live in a lightning prone area, following grounding recommendation for DC solar systems is imperative. Your DC system is just as likely to have surges as your AC system.

    For your home theater setup--I would suggest using a smaller pure sine wave inverter to power them. It is easy to isolate AC with a transformer (and a surge protected power strip). Plus, AC appliances are generally protected (and factory tested) for better than 2,000 volts against common mode surge voltages. DC systems just can't do that.

    Lastly, DC distribution of power is a pain...

    You need relatively large ware gauges because of the high voltage drops at 10x current levels (120 vs 12 volts) and the low voltage range (12 volt circuit drops 2 volts, 10 volts left, most devices won't work--vs 120 volts -2, left with 118 volts--works fine).

    And, your Battery Bus voltage has a very large range--it is not 12.0 volts, but in a properly operating system will be between 10.5 volts and 15.5+ volts... Most DC appliances (many intended to plug into a car's cigarette lighter) will either die below much 12 volts or get killed above 15 volts.

    The last major pain in 12 vdc is the grounding and ground loop issues. A typical 12 volt appliance ties 12 volt ground to the chassis and audio ground for external cables (as an example). You connect all of these together, and you can have DC power currents flowing through your audio and chassis grounds--In worst case / high power situations, this can fry cables and cause sparks as chassis are moved around.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    Re: question

    (if you have kids, they can get fingers and metal objects into the Cig. outlet).

    Can vouch for this. My neighbour kept blowing fuses in his van, couldn't find the cause until he found the dime stuffed in the cig lighter...+ point touched by dime touching walls of socket. Poof, poof, poof...arrgghhh Davey:grr

    Ralph
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: question

    Polarized Anderson Connectors work great. Available in various sizes up to better than 50 amps. I use them for all my 12vdc stuff except the telephone. If you initially wire them properly, you CAN'T cross wire anything, as they will only go together the proper way.

    Icarus