There are many types of water heating systems. The
common in the US is the tank type <link>. This is a
beast, a water tank, heating elements and a
switch. The water in the tank is heated to a target
temperature and maintained by the thermostat switching
element on and off. When hot water is
off, cold water enters to replace it. The only nod to
sophistication is that this cold water enters at the
in an attempt to prevent the hot and cold water mixing
and cooling the outflow. This doesn't work. The result is
declining water temperature in times of peak demand.
The standard solution is to buy a bigger one. More water,
larger heating element. It ameliorates but doesn't solve
problem. Worse, the larger tank leaks heat for all the
of the day it isn't being used, only a little more,
proportional to the extra surface area, but more.
The solution, is phase change. When solids melt, they
absorb a huge amount of heat energy for no real change
temperature. Conversely, when liquids freeze, they give
out a tremendous amount of heat energy while the
temperature stays the same. This is the principle behind
ice in drinks, and the coffee cup I invented <link> that
someone inconsiderately invented before me* <link>.
So, water heater, tank style. Water in the tank. Tank has
chamber inside filled with a wax that melts at say 50
Celsius. No need for double walls or any such
sophistication. Even a couple of sealed metal tubes of
reasonable volume would do it. Now, the heating
heat up the water and as it approaches maximum
regulated temperature, the wax starts to melt. As the
thermostat clicks off, the wax is liquid. Now, water is
demanded, hot water leaves and cold water rushes in.
temperature drop is detected and the heating element
turns on. Simultaneously the wax begins to solidify
transferring huge heat capacity to the water.
A kg of standard hydrocarbon wax will melt with 220kJ
energy given off, which will be enough to heat 52 liters
water one degree. So 10kg would provide very significant
heat buffering capability, in a package 1/60th the
of water. So you could have a much more stable tap
temperature without a bigger tank leaking more heat.
Now, if someone would kindly make one and send it
perhaps I could have a shower unimpeded by the
*My invention lacked the leaky lid feature.