kWh of storage means very little. What is needed is a discharge temperature and power delivery figures.

1 tonne of water can easily hold 300MJ at 80°C, but it can just as easily hold half that. Not saying, before I get jumped upon, that water is a better material to store heat in, just highlighting that kWh is not a good unit to describe this.
Now if you want to claim that 1000kg of this material can reliably deliver x m^3 of air at 25°C for y hours, then that is a different matter. Do you have any figures for what it can actually deliver.

Could anyone explain how this kind of heat store could be setup with a existing MVHR, my understanding is that MVHR doesn't deliver enough airflow for heating or would it with higher temperatures from the store. I understand the MVHR can provide the humid air to the store but missing how the delivery works, is an extra fan required or would it be the MVHR unit that does it?

I have concerns about fan power requirements, resistance of the heat storage material, the larger the surface area the higher the potential resistance, pushing air through tiny spaces could be an energy drain on fan power.

Ahhhh fan power! Not that is also something I remember.

We were extracting energy from the zeolite at somewhere well above 3kw, about 9kw IIRC. In order to do this we were using an air flow of some 100l/s.

The output temp of the air was high, tumble dryer high, so well above 60C, possibly even 80C.

The air was also bone dry (very little water content at all).

The input air was high RH and pretty warm too, about 40C and 90+ RH (think the output from a tumble dryer).

We had to use a pretty massive fan, in the kW range to achieve this, (the actual fan we used was a custom designed one that was 500mm in dia but less than 50mm thick). The air was blown thru a zeolite bed of about 0.3m2 cross sectional area and 200mm length.

That should give you an idea of the power and flow rate requirements of our application. Obviously 10 years of refinement and optimisation (we were very space restricted but had little constrain on power) will have improved that.

If I could go back to the input/output RH issue.

If I understand this system uses atmospheric humidity to release the heat. It does this by passing cool, slightly damp air through the zeolite bed to become warmer, much dryer air. Ecomind, correct me if I'm wrong).

My worry is this: whenever you heat cooler air up, the RH drops. This is not normally a problem in the Uk as when the air is cold, it is often damp, so heated up the RH is still acceptable. If the air is heated by passing over a zeolite, it not only increases in temp from say 20 to 30C, which would reduce the RH, but the absolute water content reduces (having being adsorbed by the zeolite) further reducing the RH.

I would imagine a house with it's air supplied via a zeolite bed would be have an uncomfortably low humidity level (like living in the alps in winter)

How does Xsorb get around this issue?

Am I right in thinking then that this "invention" is basically a warm air heating system which relies on ducted air around the house?

If someone has already referenced/ posted this, apologies. This is Mr Minkkinen's granted GB patent. It's too large to attach here, but if you click on "original document" (further apols that I can't see to post links) you can download it.

http://worldwide.espacenet.com/publicationDetails/originalDocument?FT=D&date=20080625&DB=EPODOC&locale=en_EP&CC=GB&NR=2444949A&KC=A&ND=4

Claim 1 at the end defines the monopoly. I suspect that the key feature differentiating it from what has been done before is the 3 month requirement at the end of the claim.

JSH - thanks for your response. I was hoping my post (plus the one a day earlier) would have elicited a response from EcoMind but nothing doing so far! So my understanding was not too far off the mark then; for the Xsorb system to be of use to me I would have to install a fan unit to blow air through the adsorbent bed followed by an air to water heat exchanger, which could be coupled up to a coil in my thermal store. In my case I presume this air would have to be "outside" air? How would I "charge up" the adsorbent in the first place?

It may well be that some, maybe all, of the practical problems can be overcome, but from what I can see these are the key ones:

1) The material needs to be recharged with heat and the adsorbed moisture needs to be driven out. This process is unlikely to be anything like 100% efficient, as the driven out water, and the dry recharge air needed to push the water out, will inevitably take some recharge heat out of the system (probably a fair bit).

2) When releasing stored heat energy the material needs to be fed with a controlled amount of moisture, matched to the output heat energy requirement. This may or may not be met by the humidity of the exhaust air from the house (assuming the material is fed with house exhaust air), so it seems likely that an additional source of water injection might be needed.

3) To transport the moist air through the material and extract the heat as hot, dry, air will require a fan and there will be a pressure loss across the material that will absorb power. The fan power needed to produce the required air flow rate might be substantial, especially as very fine input filters will be needed in order to keep the material free from airborne contamination.

4) If the system uses moist exhaust air from the house as the input, then the flow rates required for an adequate heat output are likely to be quite high, significantly greater than typical MVHR flow rates. The house ventilation and heating system would need to be designed with these high flow rates in mind, with large ducts to keep velocities down and reduce draughts.

5) If the system uses outside air to operate, and then has some form of hot air to liquid heat exchanger to transfer heat energy to the house, then it seems very probable that additional water injection will be required in cold weather, as the moisture level in sub-zero air will be close to zero.

All told we don't have enough information about all these factors to determine overall practicality or efficiency, and this is very much a system where the devil is in the detail. The properties of the material are really almost secondary to the engineering challenges involved in making it work as a practical domestic scale heat store.

<blockquote><cite>Posted By: Ed Davies</cite>Posted By: Jeff B: “How would I "charge up" the adsorbent in the first place?�

See the link I posted yesterday:

<a rel="nofollow" href="http://new.xsorb.nl/?page_id=18">http://new.xsorb.nl/?page_id=18</a></blockquote>

Sorry, missed it yesterday. Have seen it now. Looks quite simple on paper but it seems to me that it would be quite an expensive proposition in my case with a lot of new kit required. I'd rather not be a guinea pig with this technology - quite happy to wait a year or two and see how things pan out!

It's a pity that Ecomind hasn't returned yet to give us some feedback on how we could economically use the Xsorb technology.

I've been giving it a little further thought myself. One thing that the xsorb website mentions is that it is more efficient to charge the material with solar air panels rather than solar liquid panels, so this got me thinking.

Rather than looking at this as an inter-seasonal store, if you were to look at it on say 2 week time scale, perhaps you could have a large enough solar air array to harvest enough heat for a passive house and then use a smaller amount of xsorb to smooth out the delivery of the heat when it is required?

A 150m2 certified passive house should only require about 2250kWhr/a so about 500-600kWhrs/month in the heating season.

1m3 should then provide sufficient storage for any 2 week period and as long as you can harvest sufficient solar energy to fully charge the store at some point in the 2 week cycle then it could work.

What we don't know is the efficiency of the store in converting the solar air into stored heat, if it is low then you probably won't be able to harvest enough energy in the middle of winter even assuming you get 3 or 4 good sunny days during the two week period.

There are also still the questions over the fan size to extract the heat from the store but perhaps that is minimised in this scenario with the store being as small as possible.

If you were going to install solar PV anyway it is interesting to note that there are hybrid PV/air panels already available and when the air isn't required for space heating it can be ducted to an air to water heat exchanger to provide DHW and when the DHW requirement is satisfied any excess hot air is just vented to atmosphere.

This whole arrangement would help greatly the economics of installing the massively oversized array that would undoubtedly be needed to harvest sufficient heat in the winter. Perhaps it might just work, any guinea pigs?

http://www.grammer-solar.com/cms/en/solar-air/products/pv-hybrid-collector.html

Not sure if we're "not seeing" the UK website that is described as Xsorbs only UK supplier deliberately for fear of advertising or because we enjoy chewing the fat and surmising what it may or may not be. It does say among other claims

• "Cheap to purchase ROI 3-5 years"

I'd love to see the figures behind that. I'm intrigued by the product.

RobinB

Lets not forget this is very old technology just the material is slightly different to the more volatile caustic soda which has been used in the past and would work perfectly well with high temperature solar panels for the recharge.

http://www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/soda/soda.htm

Posted By: Chris P BaconRather than looking at this as an inter-seasonal store, if you were to look at it on say 2 week time scale, perhaps you could have a large enough solar air array to harvest enough heat for a passive house and then use a smaller amount of xsorb to smooth out the delivery of the heat when it is required?

There's a continuum between pure inter-seasonal stores and day-to-day thermal stores. I think it's quite reasonable to consider a store where you go into the winter with the store more-or-less full and deplete it slowly over the winter season but take any sunny weather that comes along as a opportunity to stash away a bit more energy.

What we don't know is the efficiency of the store in converting the solar air into stored heat, if it is low then you probably won't be able to harvest enough energy in the middle of winter even assuming you get 3 or 4 good sunny days during the two week period.

Yes, this is a good point. Efficiency of charging in August doesn't matter much but you can't afford much inefficiency for winter charging.

Posted By: JSHarris...with the inevitable losses that will arise, both from the fans and from heat that will be lost as exhaust.

Bear in mind that during winter charging there's the opportunity to recover a lot of that heat. Their diagram shows that being used to pre-warm the outside air being fed to the solar collectors.

Posted By: RobinBI'm intrigued by the product.

Me too. However EcoMind's approach has put me off sufficiently that I've dropped any thought of including this in my immediate plans which is a pity as I think it has some very big advantages over the large water thermal store which is plan A.

Can we take any ensuing browser discussions to a separate thread, please. This one's likely to be of future interest and is long enough already.

I don't think it's a browser thing. I'm using Internet Explorer 8 & it doesn't work for me either.

David