I found its idea is quite interesting: control the temperature of these two pieces of metal, cold water goes in one end, cold water runs through internal path inside the block and absorbs temperature of the metal until it reaches the same temperature, and goes out the other end.

We can have all benefits that we want, such as 0.6mm jet, long internal tube inside the bloc, preinfusion chamber for pressure ramp up; PID, heavy grouphead for direct temperature control. But why this technology has not been in a commercial machine?

I would guess that achieving the heat capacity of a large commercial's boiler you would need a huge chunk of metal?

I imagine, that because of the performance of the thermoblock machines currently available, that to really give the stability that can beat a HX system, or even a Dual Boiler system, it would have to be one huge chunk of metal.


Personally I think that the dual boiler system is the best system available out there right now.. And adding a saturated brew group.. There is some seriously stable temps. Given that the PID is becoming commonplace on a stock setup like this, I almost think that a thermoblock would be a step backwards in temp stability, and even further backwards on temp control, meaning being able to control temps to the half-degree.

I would like to think a thermoblock would allow for a more affordable machine, but I have a feeling that it would have been done already, and it would probably be as or more expensive, given the size that that the thermoblock would be.. Im assuming.

default wrote:I found its idea is quite interesting: control the temperature of these two pieces of metal, cold water goes in one end, cold water runs through internal path inside the block and absorbs temperature of the metal until it reaches the same temperature, and goes out the other end.

We can have all benefits that we want, such as 0.6mm jet, long internal tube inside the block, preinfusion chamber for pressure ramp up; PID, heavy grouphead for direct temperature control. But why this technology has not been in a commercial machine?

Actually, it has been done in commercial machines. The machine sold here http://www.amanti.com.au/prodguide4.htm is a thermobloc design. See also the attached pic taken at the thermobloc stand at the Milan trade show.


Alan

Wall mounted lever machines from the 50s used gas fired thermoblocks/instant heaters. There are people experimenting with using the group or a small thermoblock just ahead of the group to take nearly hot enough water and regulate the temperature very precisely, maybe even profile it over time.

Often the answer to questions like this is the same as why keyboards are still qwerty: inertia.

Thank you for all the answers. Alan, that is very interesting, but the website not saying much.

This idea came up while looking at the design of Aurelia Competition machine. Hot water from lower and upper tubes of the HX is controlled by two different sizes of gicleur, and the big chunk of metal at the grouphead to help stabilize the overheated water, if there is any. Astoria +4U has dedicated heaters at each grouphead to control the temperature of the metal. Dalla Corte has combined the grouphead and boiler into one unit, thus no water travel and heat lost. Just combine them all, and voila, thermobloc.

I think as far as it is a boiler, it still is prone to temperature swing when cold water is introduced to the boiler. Often the reading probe is put at the most fluctuated point in the boiler, and the water outlet at the most stable point in the boiler, which means there is a turbulence of water inside the boiler. And not to mention the distance between boiler and grouphead that water need to travel and lose heat to the environment. Even the newest and well thought-out design, like Kees' Speedster (my dream machine), still needs some offset at the PID and the delivery. This is not to say that boiler system is not stable, but isn't it so '60s?

Would there be any drawbacks of the thermobloc? Faster scale build-up?

One disadvantage, or advantage depending on where you live, is that they work a better in places like Australia and Europe that have 240 Volt AC electric power. My understanding is that they do not work as well in the U.S.A. because of its 110 Volt AC electric power. I think is the reason why there are so few machines available in the U.S.A. with this technology. But I could be wrong.

Geoffrey

It's so easy to make generalizations like "thermoblock = BAD"

But in general, it's rarely effective or productive to over-generalize. Everything depends on the design characteristics, EVERYTHING. Just because many cheap domestic espresso machines use small, short, underpowered thermoblocks made from aluminum does NOT mean that technology couldn't be designed utilizing a similar operation principle to great effect.

In my mind (I'm a career engineer and designer), I can readily envision an extremely accurate and controlled thermoblock-type device for brewing coffee or espresso. Depending on the length of the path, materials of construction and power/arrangement/control of heating elements such a device could possibly be superior to conventional boilers in some ways.

Such a thermoblock would bear little or no resemblance to what is currently used in cheap coffeemakers.

I agree. Sunbeam Australia has come out with some home models that can produce really nice espresso.
I see no reason why the concept can no be taken to higher level ( commercial).

This is what i call a god shot coming from a dual thermoblock machine:



Also we have to keep in mind that generally speaking in terms of high end espresso the word "thermoblock" is cursed....

One Big plus of thermoblock based machines is that they can be easily descaled.