BATCH HEATER

This simple batch heater is popular in many southern states where freezing is not a problem. It's used to preheat well water for a domestic hot water system, however it's not very efficient because of night heat loss.  The nice thing about this "Bread Box" is that it's inexpensive and easy to build. If you can find a small water tank like the one in the picture you might like to build this batch collector. 

If you don't have access to a small tank you can still make a very simple experimental bread box out of cardboard, crinkled newspaper, aluminum foil, a jar of water. 

1. First  stuff the insides of a box (1'x1'x1') with crinkled strips of damp, newspaper. Mold the newspapers into the shape of bowl. Now line the wet newspaper with pieces of aluminum foil and press the foil into the wet cavity with a mixing bowl. Remove the bowl and pray that the cavity retains a bowl like shape. Do the best you can without going nuts. You won't be eating out of this bowl. The batch heater you are making will only be used for experimental purposes. Now comes the hard part. You'll have to wait a week or two for the wet newspaper to dry out. You could place the wet box in a hot dry attic if you like to speed things up or you could use Elmer's glue instead of water to shape the newspaper.  I know it sounds messy, but if you're on a tight budget this is a great way to make an insulated, dish batch heater. 

2. Now you'll need something to collect heat. How about a jar filled with water placed on a raised platform in the center of the insulated foil lined bowl that you created.  

3. Take a temperature reading of the jug of water before putting a glass or plastic lid on your Bread Box. Now point your batch heater directly into, bright sunlight for an hour and measure the temperature of the jar of water.  The heat collected is equal to the weight of that water in pounds x the temperature difference between the initial and ending temperature of the water. This dish batch heater is not very practical because of the narrow window available for collecting heat. The trough batch heater has more tolerance for heat collection at various times of the day. Long troughs are more efficient than short troughs that cast shadows on the storage tank. You could try building a more practical trough batch heater if you like, but there will still be a problem with heat loss at night since the area of heat collection is not separated from the area of heat storage. This problem is overcome with the thermo siphoning batch heater,  

 thermo siphoning BATCH HEATER

This thermo siphoning batch collector is a great improvement over the simple batch heater above because the heat storage area is separated from the heat collection area and the tank is insulated.  The only complaints I have about this direct water heating system have to do with the small capacity of the storage tank and the possibility of freezing in a cold climate. This kind of collector might be too difficult for you to build, but you can still demonstrate the thermo siphoning phenomena. 

Tell us about your experimental results on the Batch Heater forum of the Bulletin Board.