Originally Posted by jedwards
We are working to expand our direct presence in Europe
and expect to have distributors there begin offering our portables before the end of 2010. The intital products will likely be the ULT25 and SC-DF25 with others following.
Good, this range of products & technology deserves a lot better representation & media exposure than the current
There are so many options with a FPSC system that I am not even sure where to begin with my answers as it is difficult to explain all of the nuances of Stirling theory in this format. For each answer I provide, you seem to have three questions.
I noticed only afterwards/recently that the indentation/line-breaks in my original posting/editing goes lost
when actually shown online, which doesn't really help when reading my long ponderings....
Will try to add another line break for each alinea, maybe that helps.
If you have more questions about the technical aspects of FPSC based cooling products and systems and how they work and can be integrated into custom insulated chambers, I would be happy to discuss them with you. PM me and I will give you my contact info.
Only the SC-C925 and its variants use the CO2 thermosiphon for secondary heat transport. The FPSC itself is also available seperately and can be integrated in several ways (see attachments). We also offer units that use forced convection which have no orientation limitations (SC-JS04 and SC-JS05)
As for a eutectic based systems, A FPSC system can take advantage of phase change materials just as much as compressor based system or any cooling system for that matter. Eutectic evaporator or plate based refrigerator systems use phase change materials as an energy storage method (think ice) in order to minmize energy consumption. Most FPSC systems don't worry so much about energy consumption (it's already about half of the compressor systems in our lowest efficiency system) and don't use phase change materials except in cases where the driving energy is being extracted from sunlight and it needs to stay cold overnight with out battery backup. Probably the biggest disadvantage to eutectic systems is that you are locked into a single temperature without using a phase change material with a eutectic temperature as low as you will ever need to set the unit combined with a secondary thermal regulation circuit/fan and many people seem to prefer the ability to change the temperature of their box from freezer to refrigerator and back. A very simple alternative would be to put eutectic material inside the box. If you want a temperature right about 0degC then use blue ice if you want it warmer there are several waxes that can be used. Just match the temperature set point you are using to the phase change material. If you really want to get fancy, fill the defrost catch tray on the SC-JS04/JS05 with your eutectic and set the temperature of the system acordingly to match and voila you have a FPSC refrigeration system with eutectic backup.
First, I should note that only recently I got a full grasp on 'eutectica', in both pure physics and the thermodynamics related to (compressor) fridges.
My understanding right now is that the concept
is *more* than just a 'time-shift' or 'peak-energy' holding plate, cq competing with a battery
It allows a compressor fridge to send all it's thermal energy in a relatively *high* temperature point, instead of going below that point every on/off cycle....and this 'deep-cycling' results in a lower thermodynamic efficiency (COP, thermal energy divided by electrical
energy) than at this higher steady eutectic temperature.
But: that COP-benefit of eutectica is probably less relevant for the Stirling concept/cyclus, because it's COP doesn't 'crash' at higher delta-T (and/or higher ambient temperatures).
(but even the Stirling cycle will consume more energy with higher ambient temperatures of course; it's just that you can send an almost unlimited amount of energy into the Stirling engine
, and still reach the targeted box temperature (all assuming the Stirling engine
is large enough....but that is exactly why I like those superduper-deepfreezers....
That said (and hopefully understood correctly, in both directions....
), in that same context of compressors/Rankin-cyclus & eutectica, probably to a lesser extend also Stirling, I have a 4th argument/theory in favor of eutectica, more than just 'time-shift' (night-silence), 'peak-energy' and 'absolute' COP:
If you run that 'timing' in reverse, cooling at night (eutectic charging), idle /discharging during the day, you have an inherently better COP and/or efficiency for both Rankin and Stirling, because the ambient air is much cooler.
And all that makes me wish for an eutectic option in the Twinbird boxes too....
And for the true effiency bean-counters, it *should* matter to them too, squeezing out a few more percent of effiency from a fridge-constellation, in particular in the context of solar
Note that also only recently I read a research-report on eutectica versus battery power....seems eutectica is more efficient than batteries in the context of both volume and weight (although the subjective/emotional rating/weigh-factor of displaced food/beverage can challenge physics here....
(note that the ideal holding plate, in particulary with evaporators/cooling elements perfectly surrounding the box/walls, also covers/surrounds each of the walls, for the same homogenous thermics (most important if you like being very close to 0C, but not freeze over your drinks (it doesn't flow well, and is annoyingly noisy at night, even if there is some fluid left among the ice-crystals....
(this is also an aspect of boxes that is hardly mentioned by anyone, not by manufacturers, not by testers, not even by experts in their fridge-literature)
(actually, the only fridge I know that has both the evaporator and holding plate in the same ideal surrounding shape (other than a small 0-shape freezer
compartment), is the Woick-modified Engel series (Woick is a German outdoor shop annex expedition outfitter)....each and any of the other brands keeps it at an U, L or even just I-shape (even some of the otherwise rather high-end Kissman boxes have I-shape elements))
Oh, before I forget, I should also mention why I came up with this 4th theory/benefit of eutectica, mostly in the earlier context of (COP-limited) compressor fridges:
My application is a deep-freezer inside one of the side cargo compartiments in an old Volvo
6x6 firefighter....since these side compartiments are covered by rolldoors, they can't be insulated....and being aluminium, with a roof also from aluminium, it gets rather hot in there in summer.
And while a regular compressor fridge, with eutectics, is happily chugging away in there, I don't trust the same location with a freezer, at least not without having the option of just sending in more power, like I can with a Stirling, instead of running into the limits of the Rankin cyclus.
As a general concept/argumentation:
After long contemplations, I considered & concluded that having 900L of water
onboard (of a relatively small 6x6 vehicle), for showering in the desert, just wasn't decadent enough....I also must have icecreams on board....
(in a more serious context I also want to have frozen pre-cooked food
with me, for culinary highlights way out in the bush, especially in regions where the local kitchen is somewhat, eh, challenged)
(anyone ever travelled in Russia
, far away from the main cities?....and you thought the English
kitchen is a challenge?....or a restaurant service
a la Fawlty Towers/John Cleese is unimaginable?....better reconsider, and prepare for something far worse than your imagination....
(the good thing is that 20 years ago, it was even worse, much worse....
(which challenges the imagination even more btw....8-))
Space Shuttle mission STS-60 in 1994. M223 Stirling Freezer used to provide low temperature storage for expeiments and crew rations. ONLY cooling technology approved for operation DURING launch, at least up to that time. Who knows what they have tried since.
That said, a LOT has changed over the last year or so, especially WRT pricing and availability.
I'm not sure why you are not getting a response from GCBV, but when you get my email from the above mentioned PM or from a couple of posts up, copy me to your request for info to GCBV and I will try to figure out what is going on. Since I'm not 100% sure of exactly what is allowed in this forum (Moderators: I'm just trying to help. I am not attempting to sell anything. I do not get anything like commision. In fact, it is a pain in my butt to sell to anyone but our distributors. However, if they want it and I can help, I'll give it a go but there is zero, maybe even negative, pressure), lets just say that GCBV gets their inventory from me and I ship inventory all over the world.
Good, I like transparant distribution channels & logistics....
(even though (individual) shipping
cost will probably make it inefficient to bypass any national party, assuming they order in bulk)
(if not, it might still help somewhat in the customs/VAT department....