Second Idea

We were still looking for a place to put an electrically powered water heating element in a natural gas tank, and after looking at the retrofitted natural gas tank heated by solar power at Pete’s house we decided to take out the drain pipe and put the element in there. The drain is a good location because it is at the bottom of the tank and because of convection we want our element low. It is also an unnecessary part of the tank, rarely does a tank need to be drained, and if it does need to be the element can simply be pulled out.

Drainage Pipe Removed

We took one of the heating elements out of one of the 30 gal electric tanks and found that it was a 4500W 240V element.

Heating Element

Heating Element Rating

The measured resistance of the 4500W elements were around 12.8 ohms and for the 3500W element was 17.3 ohms.

Resistance of 3500W 240V element

We put a new element into the tank just to plug the hole.
After taking out the drain pipe our device screws into the existing threaded hole in the side. As seen in the figure, the device consists of a 4500W, 240V electric water heating element (that can easily be replaced with any rated element) that was slightly bent by pushing the parallel rods closer together. The element is threaded through a reducer and then a nipple that screws into the tank. The nipple size is 6″ so the element does not hit the flue that is still in place in the natural gas tank.

Our first design threaded the button thermostat through a T connecter where the drainage pipe used to be. The difficulty with this design was putting the button directly in water while also being connected in series to the photovoltaic cells and heating element.

Design 2.jpg
Design 1

90 C Thermostat Button

Our second design involved severing the heating element at the tip and connecting the thermostat in series within the water tank. The difficulty with this design involved the coiled nichrome wire found within the heating elements. Working with nichrome is challenging and beyond the scope of our initial experimentations and prototyping. However, we may want to revisit this design when making a product for commercial use.

Design 3.jpg
Design 2
Nichrome Wire Coiled Inside Element

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