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making 170*f solar hot water

michaelmichael Member Posts: 302
Hi all,I have a potential customer who is a diary farmer. To clean his equipment he needs a 100 gallons daily of 170*f hot water. His propane bills are killing him. He is sure he can get a grant for a solar hot water system.I have sized this already. I want to see what you folks come up with.I have sized it for Flat Plates and evacuated tubes, so I am open to both.Please specifiy how you would handle summer overheating....Any input welcome.Seriously this is a market (farmers) that has not been explored in my area. These guys want and need help to survive in this country (no politics please).Thanks for your inputMichael

I forgot to add they use 2.5 gallons propane a day.

the water is heated by a boiler to a side arm tank.

I came up with 8-10 collectors.

seriously I want some help on this.


  • RadmanRadman Member Posts: 70
    More Beta please

    Hi Michael,

    Could you give me some more data?

    How frequently does the farmer shut down processing and for how long?

    Where is the farm located (city, state)

    What is the ground water temp in the dead of winter?

    Where are the possible collector locations?  (ground, roof, facade, etc)

    I am happy to crunch some #s in T-Sol for you, but need more info.

    "If it was easy, they would have called it PV."
  • michaelmichael Member Posts: 302
    170 hot water


    Here is the Data:

    The farm never shuts down. I would still put a bypass in.

    The farm is located in Ithaca, NY

    The ground water temp in dead of winter per farmer 50*

    Will be roof mounted (south almost died on 192).

    I am also trying to find a way to use the extra summer heat without dumping.

    Thanks for input

  • hot rodhot rod Member Posts: 7,014
    select a few collectors

    and plot their efficiency via the SRCC data. i suspect you will find flat plate collectors running below 20% efficiency in those winter conditions. 170F - ambient divided by solar radiation. plot this on a graph as explained in I-dronics 3 and you will find that the evac tubes may be a better match for the cold climate you are dealing with.

    If you size for a certain SF at winter time conditions you may very well have excessive summertime production. use it or lose it!

    Saw a wild stirling engine mounted on a parabolic dish at the Anaheim Solar Power show last week. Now there is a way to harness some solar.

    The most efficient thermal solar array is in AZ at a Gatorade plant. They just take the water to 90F. This allows them to run it through filtration and RO. Then they boost it via high efficiency boilers to the final needed temperature.

    If you chose flat panels you might consider that approch, keeping the return to them low to drive up the efficiency.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • RadmanRadman Member Posts: 70
    edited November 2009

    Hi Michael,

    It sounds like the load is year round.  The closest I could come to with weather bin data is Syracuse.  That is fairly close, but the weather 1 hour away could vary greatly so close to the lake.   For estimation purposes, it is what we have.   I simulated a simple 2 panel E-tube system at 60deg inclination, 192degSW with 0deg adjustment for declination.  Storage capacity of 500L (132g) and 6sqM of E-tube absorber. (66sqFt)   Based on that and a 100g draw at 170degF you get a solar fraction of about 42%.   This is pretty low, but when you consider the efficiency of the system, it is fairly high.   The efficiency in T-Sol distills the total solar energy (insolation) down to the actual energy USED.   52% is pretty high, and anything above 50% is a good place to start. 

    Adding a 3rd collector only bumps the fraction up about 5% but lowers the efficiency 10%.    With solar, a good mantra to repeat is "less is more"  Or, "If it were easy, they would have called it PV"   Attached is a graph FYI.   The nice thing about this load profile is that it requires daytime draws, continuous operation, and low volume.   You can always add more collector and storage, and stage the tanks.   In this case, I would recommend a Caleffi iSolar 3 or iSolar Plus controller and a 3 way 120v diverting valve like a Caleffi Z616637.  This allows you to stage the tanks depending on insolation at the array.   Initially, the investment for two 3sqM E-tube collectors and a 130g tank is steep, and will still require a backup to allow for the 170deg supply to the system.   If you look at evacuated tube efficiency at those inlet temps, you are fairly high near 40% while a flat plate would be in the 20% range assuming low ambient temps in the winter at 32deg.     I am not suggesting that E-tubes are better in any way, just that around the temps that you are trying to reach they fit the application better.    You want to design with two efficiencies in mind: Collector efficiency and System efficiency.   I support designing from the system standpoint before being too critical of collector  efficiency.   The collector efficiency is a moving target, whereas system efficiency in many applications is more linear.    Harvest the energy, and use as much as possible without losing a ton to piping, heat exchange, under use, etc...  
    "If it was easy, they would have called it PV."
  • RadmanRadman Member Posts: 70
    Results with Seido 5-16 collectors

    Hi Michael,

    Attached is a graph of the results with three Seido 5-16 tubes and 155g storage.  The additional collector and storage is needed to get the performance in sync with the Viessmann Vitosol 300 collectors I ran in the first design.

    Just an FYI.

    It is interesting to run "what if" scenarios with different collectors & storage at the same installation parameters within T-sol.  You can also change parameters to see what those changes do to affect the performance of the system.
    "If it was easy, they would have called it PV."
  • michaelmichael Member Posts: 302
    edited November 2009
    Thanks Radman

    Your estimates are little lower than mine. I will have to check my input. Thanks for using this forum the way it should be used, Bouncing ideas and information off each other for all to gain. You have some of the staff here excited about your different findings. thanks again Michael
  • Mark EathertonMark Eatherton Member Posts: 5,582
    Waste heat recovery potential?

    Have you considered the potential of waste heat recovery? I do know that the milk when it first comes out of the cows is warm, and must be cooled down significantly. So I assume that there is a refrigerant based system on site for cooling the moo juice down. Why not use it as a DHW preheat. The heat is FREE, and you are already paying to remove the cow heat. Why not recover it in the DHW system?

    BTW, do you know what you call a cow with no back legs? An udder drag :-)

    How's about a cow missing two legs on one side... You got it, Lean Beef ;-)

    How's about NO legs.... Yup, ground beef....

    OK, enough bovine humor.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • michaelmichael Member Posts: 302
    this is no bull....


    They already have a recovery system. They have it piped into the heating system in the barn (not much of one). The recover fluid comes out at a 104*. Nice, for just cooling milk down. I just finished putting a 9kw PV system on there home. The next step is the hot water for the barn. They want to get a grant for this. So anything that makes sense has to been done before presenting to the feds and local gov'ts. It has to spelled out and has to be documented to the "T".

    Thanks though. Any other input more than welcomed.
  • Mark EathertonMark Eatherton Member Posts: 5,582
    Thinking outside the pipe...

    I have actually worked on the HW systems for a dairy milking operation, and I know how hot water intensive they can be. The heated water, after it is used, for udder washing, tank and equipment sanitation, what have you, goes to a drain. This drain could be an excellent potential heat source for a water to water heat pump. It would obviously need to be sanitary, but I am certain it can be done. Once it IS done, the need for an aux. hot water heating system is basically only there to cover the system standby losses.

    There was a German entity a couple of years ago who was incorporating 1" PEX into concrete sewer pipes specifically for this application. His intent was to circulate an alcohol water combination through the PEX, and extract any heat normally flowing down the drain with a WSHP.

    Something to think about, and it would significantly increase the value of the solar system.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Mark EathertonMark Eatherton Member Posts: 5,582
    Found it!!

    See attached.
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • EricAuneEricAune Member Posts: 431
    What about a drainage pipe heat exchanger?

    Take a look at this.  Not sure of the availability or documentation, but they are gaining in popularity.
    "If you don't like change, your going to like irrelevance even less"
  • michaelmichael Member Posts: 302
    that is great...

    This is one thing I was talking to the farmer about and have not had the time to research it.

    Now we's gittin some wheres.

    Much thanks!

  • michaelmichael Member Posts: 302
    Nice Mark

    Do you have any info on this German outfit. Man, thanks for the input!


    Here is a great article about solar cooling.
  • Grey Water Heat Recovery

    I recover about 1/3 of the heat from my shower water before it goes to the sewer using my Grey Water Tank.

    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • michaelmichael Member Posts: 302
    1/3 is huge

    wanna share a piping diagram? : )

  • Grey Water Heat Recovery Diagram

    It's piped like this except that the incoming cold also goes through 200" of 1" pex attached to the outside of the tank. In the winter the incoming cold water is 36 degrees, it flows through the pex wrapped around the tank and picks up about 10 to 15 degrees, it when flows through a submersed coil where 105 degree water from my shower pours over the submersed coil and the cold water is pre heated another 10 to 15 degrees to about 66 degrees or one third of the temp rise needed for domestic hot water. The incoming cold water is heated to about 60 degrees when the shower is not running. It may not sound like much , but sending 66 degree water to my solar tank is a whole lot better than sending 36 degree water to it during the winter with the shorter, weaker sun.

    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    He could make his own gas?

    There are plants out there that convert the waste to methane in a controlled environment. [url=]
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • michaelmichael Member Posts: 302
    Viessmann quote for this system

    The viessmann quote I received for this system size just blew me away. Now this is their rep in Mass. They said I would need 180 tubes (200 T) to get this 170* water. Wow! My figures and other even on this webpage have stated 64 tubes. They are more than double out estimates. This is a very interesting situation. Either all of us are wrong or they are. And "if'' they are what is the response? I hope systems are not getting over sized.

  • michaelmichael Member Posts: 302
    great idea charlie...

    I will definitely present it to the owner.

    I was check these out when I lived in New Mexico. I found an old copy of Mother Earth News (like 1974) and these had these methane chambers from India. Are you doing anything this?

    Thanks again

  • DennisDennis Member Posts: 79
    Ever jumped in a large pile of leaves?

    A few years back my son and I were hiking through the back areas of a local park, he stumbled across a pile of leaves dropped off by the township to rot into mulch. The pile was 30 feet high and about 100 feet long of tightly packed leaves. He could not resist climbing this mountain. On his way back down he fell into a void in the pile, while I was helping dig him out, we both noticed the leaves in that hole were about 100 degrees, and it seemed even hotter down below.

    I would bet that along with producing methane quite a bit of heat is also generated during bio break down.
    Just do it, right.
  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    Not enough raw material.

    I have 6 chickens so I am not in a position to make a methane producer. If I get any cows or pigs I will give it a try for experimental purposes only. I can probably earn more going to work than tending a methane producer. But a dairy farm has plenty of raw material. [url=] this may interest them too.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Mike_Mike_ Member Posts: 12
    use of brazed plate heat exchangers for solar hot water heating

    looks like compact heat exchangers are gaining popularity in solar hot water heating. i recently came across a manufacturer cross-reference of brazed plate heat exchangers at
  • tim smithtim smith Member Posts: 2,226
    Re: cool dairy waste generator

    Here is a powerpoint document on a dairy here in Washington state that made a success out of waste energy use. Pretty cool.
  • michaelmichael Member Posts: 302
    thanks Tim

    I was just talking to this farmer yesterday about something like this. Great timing on your part.

    How goes the solar in Washington State?

    Much Thanks,

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