Listeroid Garden

[Procrustes]

So I finally ordered a 6/1 Ashwamegh.  As my power plans are largely undecided, I'll try extending my growing season by adding hydronic "root zone" heater in my raised-bed garden.  I'll fill the Ashwamegh tank with a gallon or two of fuel and start it before bed on cold nights.

There's not much in the way of implementation details about such systems on the internet, at least not that I could find.  I saw two vague descriptions.  One site sad you should dig furrows every 18" to 24" for heat pipe.  The other described the use of coils of PEX, the narrow, flexible PVC-style pipe for hydronic applications.  The ideal temperature for roots is 100 degrees F, I don't know what is the safe upper range  Adherents maintain that root zone heating is more important than air temperature and that I'll see 12 foot sunflowers and like wonders.

I have 200 sq ft of raised beds, all 22 inches deep.

I'm looking for suggestions for the heating system.  I could load Listeroid with a pump and circulate coolant through the garden for instance.  I think the coolant temperature would be too hard to regulate though.

The next plan would involve a DC generator, water heater, a circulation pump, and a water->water heat exchanger.  This would employ two water loops: a themosiphon for the Listeroid and a circuit from pump to water heater to the garden hydronic pipes.  I'd exchange heat from the coolant to the water heater intake with the heat exchanger.

I favor a DC generator over an alternator because I'll probably get a battery bank some day.  I still haven't found a DC head that would load the Listeroid properly and efficiently though.

Any suggestions?

[trigzy]

An alternator from a bus is about 280Amps at 24VDC, 6720watts if fully loaded, which is over the rating of the 6/1.  So you could use that, they also usually have a nice 10 groove serpentine pulley on them.  Of course, the alternator will only load up the motor if you load up the alternator.  The same gernators can maek 12VDC as well, they just need a regulator change.  If interested, let me know and I'll find some pics or more info for you.

Steve

[rgroves]

I favor a DC generator over an alternator because I'll probably get a battery bank some day.  I still haven't found a DC head that would load the Listeroid properly and efficiently though.

Any suggestions?

Take a look at the Etek motor. Briggs and Stratton doesn't make them any more, but you can find them all over the web. About $500 bucks. Very efficient, PM, uses neodymium  magnets.  Brush kits are available.  (and no, I don't sell them or have any financial interest  blah blah)

You would pump out a whole lot of DC with one of these, and a battery doesn't care if the charge voltage wavers a bit. Something to be said for letting electronics make your AC.


http://www.specialtyvehiclesonline.com/eprints/briggsandstratton.htm  (an old site but lots of info)

"Today, two versions of the motor are manufactured. One is an enclosed version that operates at 60 Amps continuously and 325 Amps intermittently at 48 Volts. An open version of the motor operates at 150 Amps continuously at 48 Volts, nearly 10 hp in a package 8 inches in diameter and 6 inches deep. The Briggs & Stratton motor is also an excellent generator. Voltage output is very consistent when the motor is spun by one of Briggs & Stratton's engines, enabling the possibility of hybrid vehicle configurations."

[SHIPCHIEF]

  Just go for the AC 240V gen head. You can use a step down transformer and diodes to get that battery charger function, or buy a nice big smart charger and run it off the AC power. The ability to run your shop on the AC power is priceless.
I was thinking a similar thought about the secondary heat loop, except for hydronic home heat. George B ran the Lister cooling water thru a copper coil built into a hot water tank. That hot water tank can handle the hydronic system pressure, and a circulating pump can forward it to the hydronic boiler. In this case the boiler would still fire when the temp drops to the 160 setpoint. If the Lister contributes any heat, then furnace oil is saved.
  In your case, regulating the soil temperature is the technical challenge. Taking heat from the lister is simple. The first heat exchanger is for heat to you garden, the thermosyphon system dictates that this heat exchanger be on top. If the garden is up to temp, then the engine coolant would still need to reject some heat, so a second heat exchanger below (like a car radiator) would serve that function, then the coolant would re-enter the engine.
Scott E

[Procrustes]

  Just go for the AC 240V gen head. You can use a step down transformer and diodes to get that battery charger function, or buy a nice big smart charger and run it off the AC power. The ability to run your shop on the AC power is priceless.

Perhaps.  I'd certainly pay more for DC equipment.  However I'd forgotten about these: http://zena.net.  This is the sweetest generator/welder ever.  I'd sure like to have a welder.  These units are stackable too, so you can buy extra capacity in 200 or 150 amp units.  I guess about 300 amps at 12V would about right for the 6/1.

I was thinking a similar thought about the secondary heat loop, except for hydronic home heat. George B ran the Lister cooling water thru a copper coil built into a hot water tank. That hot water tank can handle the hydronic system pressure, and a circulating pump can forward it to the hydronic boiler. In this case the boiler would still fire when the temp drops to the 160 setpoint. If the Lister contributes any heat, then furnace oil is saved.
  In your case, regulating the soil temperature is the technical challenge. Taking heat from the lister is simple. The first heat exchanger is for heat to you garden, the thermosyphon system dictates that this heat exchanger be on top. If the garden is up to temp, then the engine coolant would still need to reject some heat, so a second heat exchanger below (like a car radiator) would serve that function, then the coolant would re-enter the engine.
Scott E

That's right, I would need a radiator too.  I'd been concerned about the Lister not being big enough for the job and hadn't thought of that.

I may end up installing hydronic home heating too.  User `fuelishnot' gave me a good idea for this.  Build a huge insulated water reservoir and use it for hot water and hydronic heat.  It would be convenient to dump all waste heat there.  This would work well with your 25/2 too.  You could run it flat out for a\while every day and then coast thereafter.  I'd be able to use my Lister to heat the the reservoir or to drive the pump or both.  No compatible with thermosyphon unfortunately.

[Procrustes]

Take a look at the Etek motor. Briggs and Stratton doesn't make them any more, but you can find them all over the web. About $500 bucks. Very efficient, PM, uses neodymium  magnets.  Brush kits are available.  (and no, I don't sell them or have any financial interest  blah blah)

Funny, I saw that very page not long ago.  In my original post I had forgotten about the Zena unit I mentioned above.  I have lust in my heart sir.

[Red2Beacvh]

If you are concerned about coolant temperature in a buried garden system, why not introduce the thermostat to your Listeroid. Most of these would have a mean temperature of 180 degrees. At least in this fashion, you could regulate the coolant temperature.

[solarguy]

Of course, there are 92 ways you could engineer this.  One part of the solution could be a simple tempering valve.  They're not so pricey, widely available at any good plumbing shop, and usually have a bimetallic element that takes your hot water and mixes whatever cold is needed to stay below the design temperature.  They are sometimes known as an anti-scald valve, which is pretty much what you're trying to do, not scald those poor rootlets.

Good luck and have fun!

troy

[Procrustes]

Of course, there are 92 ways you could engineer this.  One part of the solution could be a simple tempering valve.  They're not so pricey, widely available at any good plumbing shop, and usually have a bimetallic element that takes your hot water and mixes whatever cold is needed to stay below the design temperature.  They are sometimes known as an anti-scald valve, which is pretty much what you're trying to do, not scald those poor rootlets.

Good luck and have fun!

troy

The temper valve is a good idea, I hadn't thought of that.  Since I posted that I've changed my mind about a couple of things.  First I'm tearing down my Listeroid, so this spring is out.  Second, I may just attach the garden to my forthcoming home hydronic heating system.  This would especially make sense if I end up with the huge hot water tank.

Have you looked at geothermal heat pumps?  Those are attractive as well.

[solarguy]

Dear Procrustes,

Yes, geothermal heat pumps are nifty pieces of machinery that border on magic.  Well, just like the refrigerator is magic.  But I have this against them:

They are not cheap.  They are not simple.  They generally cannot be seviced by the average handy person.  They take a lot of land, like bigger than a typical lot in town unless you go deep.  They are pretty messy to install with big trenches, etc.  Durability has not been as good as the average furnace and they can be expensive to repair.  Perhaps my biggest criticism is that they are generally coal powered or nuclear powered, both of which are problematic at current usage levels for the US.  Running one off a Listeroid with some alternative renewable fuel would of course answer the last objection if you had an efficient way to use the waste heat.

They certainly have their place and they are vastly more efficient than simple resistance heat.  Not exactly my cup of tea though.

Finest regards,

troy