Fine Art Tuesday

 

Springhouse near Valley Forge

This weeks Fine Art Tuesday is a little different than the others.

The usual focus is to look at painting from a particular artist or paintings of a particular subject. Today we look at two, and only two, photos of springhouses. While there are many paintings titled "Springhouse" most of the images are not very convincing.

Springhouses

In the Northern United States and all of Canada, the temperature of the ground is cooler than the air in the summer and warmer than the air in the winter. That is useful for storing food and milk.

The graphic on the left is called a "Whip-lash chart" a name that I find entertaining. For those who don't speak Canadian, 10 degrees C is 50F and 14C is 57F. Source for this image and the next.

Assuming that the water is welling up from five meters (16 feet) below ground...or was 16 feet below the surface until it hit a strata with a high degree degree of permeability, the peak temperature will occur in September and it will top-out at 57 degrees (in this model).

Source

Many, perhaps most bacteria that cause food-poisoning reproduce most quickly at temperatures that are common in the bowels of mammals and birds.

If you use the most common strains of E. coli as a proxy for those growth rates, the difference in growth rate between 85F and 57F is a factor of 40. That is, assuming identical levels of initial contamination, the bacterial counts will be very similar after one hour of 85F and 40 hours at 57F.

While 40 hours does not sound like very long, it is plenty long enough to have the same meal the next day and almost the third.

Finding a spring 

While there are many pictures that claim to be images of "springhouses", most of them have a small out-building situated in a place where a "spring" seems unlikely.

If you have no other information, formations similar to the ones circled in red are a good place to start looking for springs. These are gulleys or valleys cutting into the edge of a plateau/highland.

Springs are where you find them

They can occur mid-slope if a permeable layer (like sand or limestone) is underlain by an impermeable layer (like clay or shale) provided the joint between the two layers is exposed.

Scouring rush. Each stem is approximately the diameter of a common pencil. It can occur in large, dense, single-species stands.

Vegetation can be a reliable indicator of a water table that is close to the surface. Cattails, sphagnum moss, willows, sycamore and horsetails (scouring rush) are all reasonably reliable indicators in Michigan. In the springtime, Skunk Cabbage and Marsh Marigolds are good indicators.

Energy consumption

To misquote the Grinch, "If I cannot find a spring, I will make one instead". How do the energy budgets for running a refrigerator and "making a spring" compare?

A typical refrigerator consumes 600 Watts. It draws two-to-three times that amount at start-up due to inrush current. Because the motor is attached to a positive displacement compressor, the motor loiters near stall during start-up longer than a centrifugal pump or a fan would. 600-to-1800 Watts of electricity are a lot of solar panels.

On the other hand, a motor the size used in computer muffin fans draws about 35 Watts or approximately 1/25th of a horsepower assuming 80% efficiency. But how much water can you pump with that tiny bit of electricity (basically one, 100W solar panel because it, too has inrush issues)?

Assuming you could perfectly match the motor to the pump, frictionless piping and so on, that amount of power is sufficient to move 10 gallons of water a minute from 16 feet below the ground. That volume sounds like a miscalculation (on the high side) until you realize that most of the power in a domestic water pump is used to generate 40psi static head at ground level. In the faux springhouse, there is a static head of zero, the water is spilling out.

Ten gallons of water a minute at 57F...or lower...can chill far more food by weight than you can fit in ten refrigerators. Remember, 57F is the warmest you will get.

If 57F is too warm, you can go twice as far down and the water you pump out will be the average annual temperature for your location unless you are in Yellowstone, Wyoming or Hot Springs, Arkansas.

The downside of Grinch springs are that they don't flow very much at night although if it were important, one could pump to a reservoir and dribble the water out through the night hours.