Back in high school I made a wood fired evaporator out of sheet metal. I called it “The Ecraperator” for obvious reasons. Over a random weekend I had some time to go back home and fire it up again. Here it is, ready to be lit, with my dad for scale.

Its lit!! The maple syrup goes in a tray that was left over from my grandpa’s maple syrup days. The ecraporator itself is just a box with a piece of dryer vent attached to the back. The long chimney helps provide a strong draft.

So in my high school days, we would light the fire and just wait. But since I have now gone to college, it was time to USE THE POWER OF TECHNOLOGY. I rigged up a little CPU fan with a power supply, and an air duct made of cement blocks to guide the air into the stove without melting the fan.

With the fan running, the fire burned HOT. It turns out that in a wood burning reaction, the limiting factor is the air. So if you force feed the air, the fire burns FAST. I had to add more wood very frequently.

As the sun set I was able to grab some very aesthetic photos.

Now that I’m in grad school, I decided to do some math while I waited. We estimated that we had about 7 gallons to boil. The ratio of sap to maple syrup is 40:1, so for our analysis we can say that all of this must be boiled.

It takes about 9MJ to get this water from 20C up to 100C, but the vast majority of the energy required is the 60MJ required to boil the water. So, 69MJ in total for this 7 gal batch.

On the standard 1500W home burner, this would take a whopping 21 hours! Plus, it would fill your home with sticky steam, which is gross. On the ecraperator, it took only about 2.5 hours to get the batch down to 1 gallon. We did the final hour of boiling on the stove. Therefore, I estimate the ecraperator was doing about 10.8 Kw, about 7 times the heat output of a household burner. This could likely be improved by tending the fire better, and near the end we let it burn slow to avoid overboiling the batch.

Here are some nice pics of the final product.

The next weekend, it warmed up, and the sap stopped flowing, so that’s all for the ecraperator this year. Stay tuned for next year though!