What would be a conceivable way to heat 3,000 gallon poly tanks of WVO? Not necessarily to a high temp, but enough to keep it from solidifying on cold nights?

Immersion elec heaters of sufficient wattage. The better the vessel is insulated, the less wattage needed. Make sure the heater will never be in contact with the poly tank to avoid melt through.

1) Circulate through an external heater.
2) Submersed electric heater of low watt density
3) "hydronic" system, providing externally heated water circulating through a heat exchanger to heat the oil.

The advantage of 3) is that the heater wattage requirements are reduced and steady, basically it's a water heater, plumbed to a tank heater. A pump circulates the hot water on demand. Hazard is very low.

quote:

Originally posted by johno:
1) Circulate through an external heater.
2) Submersed electric heater of low watt density
3) "hydronic" system, providing externally heated water circulating through a heat exchanger to heat the oil.

The advantage of 3) is that the heater wattage requirements are reduced and steady, basically it's a water heater, plumbed to a tank heater. A pump circulates the hot water on demand. Hazard is very low.

Actually, we're designing a system based on number 3. The only hiccup I can see is if there's a leak. Then we're mixing water with our oil. But provided that it's inspected constantly or there's a hydrometer, or, since the water level should be roughly constant since the water's not boiling, if there's a level gauge, you can be fairly certain you're not adding water.

If you are using a modern shell and tube heat exchanger to heat with they are made with double wall tubing. if either the water or oil were to start to leak through the first layer they would come out of the "telltale" port on the flange of the heat exchanger. Typically they are used to heat domestic water from steam or radiant hot water in order to determine that there is no contamination of the domestic water by the heating medium. Cheers

quote:

Originally posted by fasst:
What would be a conceivable way to heat 3,000 gallon poly tanks of WVO? Not necessarily to a high temp, but enough to keep it from solidifying on cold nights?

Heated tank blankets are one fasst way to solve that problem. They come in versions with low enough watt density for poly tanks. With 3000 gallons your going to radiate heat out on a cold night fasster than you can put in, unless you insulate the tank. It may be more economical to build a shed over the tank and heat the shed as needed. Piedmont biofuels built a solar heated straw bail building to keep one of their tanks warm at night.

quote:

Originally posted by fasst:
What would be a conceivable way to heat 3,000 gallon poly tanks of WVO? Not necessarily to a high temp, but enough to keep it from solidifying on cold nights?

Heating pads from your local drugstore, They don't get to hot. $15 at Walgreens here. Insulate.

Of course one could use a milk holding tank like dairy farms use and not worry about it melting. Already has the pallet stirrers in place and would only need to have either a stainless or black iron heat exchanger run through it on the bottom. Put the stirrer on a timer and have the exchanger on a solenoid valve to keep it at level temp. Yup, a spendy proposition but you'll only have to set it up once.
Keep the poly tank (only if you already have it) for washing. http://www.Bete.com has some really, I mean really neat nozzles that would fit the bill.