The GreenRoost Blog

We like to think that we are progressing with time. While it is true in many instances, it is not always the case. A great example is, of course, the Dark Ages. Eratosthenes back in Ancient Greece was just a few miles off when calculating the circumference of the Earth - certainly did way better than Columbus (and Columbus was way advanced for his time, when many considered the Earth to be flat!).

The Dark Ages is not the only example of the mass memory lapse - “forgetting” things that were common sense a few centuries ago. And when it comes to solar water heating, we’ve certainly managed to go way backwards from where we were just a hundred years ago.

A post by bibliosk8 on concretelunch.com reminded me of how a bit pricey solar water heating systems currently are, and I did a little research on solar water heaters and their history. I was really surprised to find out how advanced (by modern standards) our solar water heating systems were in the early 1900s (and apparently affordable, since the standard of living for the common folk in the US wasn’t that great prior to WWII).

Actually, the guts of a solar water heating system (the so called “hot box”) were invented way before that - in 1760s by Horace de Saussure, a Swiss naturalist. The hot box consists of:

• An insulated outside box with a glass top and the black lining at the bottom
• A smaller container inside that box

Saussure observed that the temperature inside the container could reach 228 F (above the boiling point). The sun comes through the glass, the black lining at the bottom absorbs the heat, and the heat gets trapped inside. Put water in the smaller inside container - and you have a basic solar water heater!

In the late 1800s black barrels installed on the south side of the roofs were common, and they worked well for taking baths in the second part of the day in summers (assuming the weather was sunny that day). But not so well in winter and earlier parts of the day.
So Saussure invention was dug up and used to keep the water warmer for longer periods. In 1891 Clarence Kemp was selling his solar heating system called “Climax” to:

eastern gentlemen whose wives had gone off with their maids to summer at some resort, leaving their husbands to fend for themselves. The solar water heater, Kemp advertised, would simplify housekeeping duties for this class of men already burdened by their wives and domestic staffs absence and unaccustomed to such work as lighting the gas furnace or stove to heat water.

Not sure how affordable these water heaters were, if the men who bought them not only were incapable of turning on a stove without maids’ help, but also their wives could afford to travel to a resort for the whole summer and take all the maids with them!

Fast forward a few years…
In 1909 William J. Bailey figured out how to separate the water storage from the water heating element - an invention that made a big difference! Now water heaters did not depend that much on the outside weather or the time of the day, as hot water could be stored in an insulated storage unit inside the house. Bailey sold over 4,000 solar water heaters - prior to 1918. But here is the most astounding part:

By 1941, more than half the population [in Florida] heated its water with the sun!

During the Great Depression half of Florida’s population could afford to buy and install a solar water heater!

Ironically the man who made it happen also contributed to the death of the affordable solar water heating system, here in the US anyway. With the discovery of natural gas, Baily applied his technology to gas-powered water heaters. The combination of cheap gas and aggressive efforts by power companies to increase the use of electric power (and electric water heaters) finally killed their solar alternatives on the US market.

However, a few countries not so blessed with the natural gas or other fossil power resources picked up the technology and still widely use it today. For instance, after WWII Solar water heaters were a great solution to Japanese farmers looking for easy and inexpensive ways to heat water. Currently 90% of homes in Israel have solar powered water heaters.

But do check out this article by California Solar Center for more interesting details on the history of solar water heaters.

So frankly I am not sure what makes our current solar water heating systems so expensive (that’s going to be another research project : ). Googling for “do it yourself” tutorials it seems obvious that the model of the solar heater is quite simple in concept. Perhaps not the perfect one that guarantees hot water in any weather conditions, but at least a partial one that would kick in on sunny days, and leave it up to the gas heater as a backup in prolonged cloudy conditions. And I love this simple idea of a water preheater that uses solar energy to preheat the water before it goes into the gas water heater.