I'm under the impression that most (all?) espresso machines come up to temperature using either a submerged heating element, or a heating element attached to the exterior of the chamber. Have any machines experimented with induction heating to bring their chamber up to temperature? It's basically the most efficient way to boil water:
http://en.wikipedia.org/wiki/Induction_...iderations

Of course this would require the chamber to be made of some sort of induction-friendly material like stainless steel.

Has anyone ever heard of such a thing?

(apologies if I've used any incorrect terminology... i'm new to this whole thing)

Interesting. I've often wondered about the possibility of a system similar to modern "on demand" home water heaters. Basically the water passes through a burner that instantly heats the water as it's required. I would think this would be a nice, easily adjustable method for heating water for espresso. No warm up necessary. Parts might have to be made from ceramics to reduce the amount of thermal conductivity.

I don't think that the cooking-efficiency analogy is relevant. If you're heating with electricity, all methods could be 100% efficient, if you have no thermal losses, meaning perfect insulation everywhere. There may be differences in speed (transfer rates) for specific configurations, but I don't see any inherent difference in efficiency. Stove-top cooking has inherent thermal losses: the cooktop is exposed to ambient temperature and not usually insulated, at least not on top. So in this configuration the induction method may provide the least heating of the cooktop itself, giving better overall efficiency. There's not necessarily an analogous component to the cooktop when heating water with a submerged element.
-Ed

I understand where you're coming from, but after poking around a bit more I've found this patent application that claims submerged induction heating works faster than a standard submerged element:

http://www.faqs.org/patents/app/20090025571

I wouldn't argue that induction is faster or slower, I merely contend that for this application it is no more efficient. In fact, the patent that you referenced mentions "...an appropriate electric-frequency driver generator" as part of the scheme, which in itself would have to be 100% efficient to not give this overall scheme an automatic disadvantage in efficiency compared to the submerged electrical-resistance scheme.
And, as far as I know, a working prototype is not required to get a patent.
-Ed

nixter wrote:Interesting. I've often wondered about the possibility of a system similar to modern "on demand" home water heaters. Basically the water passes through a burner that instantly heats the water as it's required. I would think this would be a nice, easily adjustable method for heating water for espresso. No warm up necessary. Parts might have to be made from ceramics to reduce the amount of thermal conductivity.

This is not similar to induction heat, but the gas equivalent of a thermoblock. Faema built a wall mounted lever machine in the 50s that seems to either have used a gas instant heat system.

Most of the thermoblocks in low end conventional machines or home superautos are low quality pressed aluminum. Quickmill builds a good quality copper tube and steel thermoblock, but still with a button thermostat. Finally, one of the Spanish espresso machine manufacturers, VFA, builds a a machine with a very large steam boiler and separate PID controlled instant heat devices in each group head. I'm still waiting eagerly to hear from anyone has tried this machine; it sounds like it could be a contender.

another_jim wrote:...with... separate PID controlled instant heat devices in each group head.

That sounds like workable scheme that would enable selectable thermal profiling. If you get rid of the thermosiphon and go "all-active" heating for the brew path, you can get the response time that you need for shaping a 30-second profile.
-Ed

I did actually look into induction heating for an espresso machine. It turns out that (IMHO) it wasn't so great. Mostly because the induction heater heated the metal but not the water so the metal heated the water by conduction. Stainless steel (ferritic types) boilers worked the best (compared to copper and brass - too conductive) because of the ferrous properties. In addition to the eddy currents, the material magnetizes and demagnetizes the iron that creates additional heat. In the end the system was not very efficient due to the boiler shell acting as the heating element and half of it is exposed. There are a induction rice cookers out there that we took apart but we also found that the induction heater only heated the metal and not the contents. Contents were heated by the hot metal container.

Anyway just my opinion of course.

Anyone else have any better experience?

BillC

decaf_Ed wrote:That sounds like workable scheme that would enable selectable thermal profiling. If you get rid of the thermosiphon and go "all-active" heating for the brew path, you can get the response time that you need for shaping a 30-second profile.
-Ed

Mark P has been saying for a while that he believes the next huge step in espresso machine tech, will be temperature profiling*; ie: being able to control the temperature, consistently, how you see fit, during a shot.

(*Not that that's what "happening next", but that when it happens, it will be a big leap forward).

Seeing how much small changes in temperature affect how coffee is brewed, especially espresso, I can certainly see why he thinks(possibly very rightly so) that. In my head at least, it makes sense that it would be "the next big thing".. Temperature is now uber-stable. Pressure has been uber-stable. Now pressure can be fully manipulated, or 'profiled', ala LM Strada. Next up, fully controllable temperature. Again, in my head at least.

I have been conducting experiments on temperature profiling (along with pressure profiling) and the findings have been interesting. I am not really the best at tasting coffee but I did notice some small differences. It is very hard to tell since I can only taste a couple of shots a day before I cannot taste any differences (lost alot of taste buds with 10 years in the Marines....... MRE's and all). I have yet to release my system to let others try it but I should be done in a few months and would love some HB testing.

Sorry no induction heating.

Bill C