alternative seedling heat beds

Im just trying to think of some alternatives to the heat pads everyone goes out and buys around this time of year to start there plants a little early. it could use wood, water, solar, anything else. Im wondering what ideas people out there have.

In "olden times"  people used to use fresh manure piled into a trench with soil piled on top..if you get it fairly deep it will throw a lot of heat depending on what sort of manure it is..and by the time the roots get down to it  it should have gone through the first stages and cooled down.

yea i know about that system, but i was thinking something i can set would be best. because there are days that the greenhouse heats up a lot, adding bottom heat to that would only make things worse. hot compost beds cant do that.

How about waterlines/hoses under the planting beds, through which you can pump either hot, warm, or cold water as needed?  Recycle the water through a tank, perhaps with a small fountain pump.

what powers the pump? what heats the water?

How far along are you taking your seedlings with heat? If you are just taking them to germination and then taking heat away...(which is what I have been doing) then you can simply set your growing containers on top of any heat source inside your home. Since I have a Geothermal system, it blows hot hair out of floor vents. I have put my grow containers on a raised baked goods cooling rack over the vents. this lets the hot air still get to the house, but bottom heats my plants. I have a few over the house and once they germinate, I take them to my sunroom for continued growth. Is that what you are looking for?

yea that's sort of the idea only a bit too small. i plant a few hundred starts of each type every year for sale and myself. as of now i start all my seeds in a unheated greenhouse, the daytime temps are no problem. its basically to just keep them heated at night without having to heat the whole GH which is 12'x20'x10'. the heater would need to be on whenever temps are below 50 ideally but im not going to go out and buy timers/thermometers. i know a friend with Subterranean Heating and Cooling System which is awesome. i am going to do that with the propagation house i am building now but that wont be done for this season.

i am kind of leaning to a small fire chamber and some sort of thermal mass as we have a ton of twigs to burn, and they are a sustainable source around here.

the area i would need to heat is about 8ft long and 1-2ft wide.

thanks to everyone for the ideas so far.

Last year I had thought of using solar heated water to provide under-planting heat in my mini hoop house, but never got around to it.  I might this year.

Similar to PaulB, the basic idea would be to build a simple solar water heater/storage contraption, mounted on the south side.  This would heat and store a working fluid (a solution of environmentally friendly anti-freeze) during the day, and release that liquid into hoses placed under the planting beds.  In the morning, the working fluid would be hand pumped back into the heater.

Further, I had ideas to make the system "active" through the cold months by using the thermosiphon effect to cycle the liquid from heater to beds.  Though, most likely this would require a small (solar powered) pump at one end.

A simple solar water heater can be made from old garden hose, or leftover lawn irrigation tubing, scrap copper tubing, etc.

Hmm, I might just start hoarding ... er, collecting, some raw materials. 

thanks tipafo that's the stuff i want to hear.

i have thought of a similar system and already have a solar heater that i never ended up getting tubing for. might have to actually try and finish it now that im not crazy lol.

A couple of thoughts - Solar heater which looks as though it has already been suggested.  The other thought is to locate the compost pile outside and use heat transfer via water to heat the soil.  i.e. the compost/manure heats the water and the water heats the soil.

JMHO YMMV

Jeff

SHCS is awesome, I never heard of that before. I had another thought too…and it will probably be better for smaller scale…perhaps your size greenhouse. It is a bit expensive depending on how many you would need, but could you bury lightbulbs in conduit in the soil? Im thinking the type that give off a little heat and are designed for undercabinet lighting. They are 12 volt, and you would need a transformer. Im sure regular incandescent would work fine too, but it would have to be larger conduit that is waterproof. Ive never tried it, so this is just theory 

Back to the SHCS, does anyone have any experience with them? Would they work on a really small scale like a cold frame type setup?

Whoa, completely forgot about that Compost Water Heater!

I came across this video about a year ago ... and guess who's hosting?

You know .... 

https://permies.com/bb/index.php?topic=7083.new;topicseen#new

A PV Solar Panel, charging a 70amp hour battery, with a small inverter.
and a washing mashine pump ( can handle hot water)
Pump Hot water out of your Compost heap through poly pipes under beds.
Could go under your Hoop House or diverted to a small Hothouse.
An Aquarium Thermostat can switch the pump on and off.
This is in my to do list...