Willis solarsyphon

[ericw]

It only needs a pump on the primary (solar panel) side to transfer the heat from the panels as in most systems. The secondary circuit transfers heat by convection.
The other pump in the diagram seems to be a left over from some other experiment.

[djh]

Some published test results

http://www.willis-renewables.com/pdf/Performance_Evaluation_Willis_Solasyphon.pdf

I finally got around to reading this. Reasonable results I thought. It seems like there were at least a couple of ways to improve the performance of the willis.

Firstly, they didn't account for the heat loss from all the extra plumbing, so in some ways of looking at it the willis performed better than they reported. But the insulation on the willis itself as well as the pipework could all be increased with useful results I suspect.

Secondly, there was a large gap between the temperature of the heated water above the willis and the hottest that the water in the tank got. Some difference must be necessary for the syphon to work but I suspect there's scope to optimise that part of the circuit.

I was also interested by the results for the coil in tank, which didn't destratify the top of the tank as much as I expected from previous reading.

[dan_c]

Did the Navitron test ever happen here?

I've been browsing around for ages looking for data on sidearms (like the Willis and Wallnoefer) and PHEs but all the links to external documents seem to be dead now.

I want to maximise DHW from a big tank (1000litres+) so a bottom solar coil is pointless in my case. I'm thinking a sidearm of some sort is the way forward but I want to find some more detailed info before shelling out for anything.

[wookey]

There is a dearth of detailed data apart from Willis' own test and rather subjective evidence from people like me. There _is_ quite a lot of good data on other stratifying systems (as opposed to bottom coils) in various academic research. E.g the rebus report, various research from Simon Furbo in Denmark, and IEA reports. But direct comparative data is missing (so far as I know - not looked for a year or so).

[dan_c]

Thanks Wookey,

I did find an Ulster University test report on the Willis which made for very interesting reading and certainly seemed to weigh in favour of the Willis for generating small volumes stratified hot water. I have searched for the "Rebus report" - which I think is titled "REBUS – Competitive Solar Heating
Systems for Residential Buildings" and came up with loads of papers and presentations by the same author so I am reading through them now.

There was a great thread on here about stratification but all the links (which people commented were great reading) are dead. I'll try to dig out the old thread and then maybe someone will have the linked documents saved.

I have also found this but not made any headway through it yet: http://www.byg.dtu.dk/upload/institutter/byg/publications/rapporter/byg-r160.pdf

Is your sidearm PHE pumped on the tank side or just syphoning?

[djh]

I did find an Ulster University test report on the Willis which made for very interesting reading and certainly seemed to weigh in favour of the Willis for generating small volumes stratified hot water. I have searched for the "Rebus report" - which I think is titled "REBUS – Competitive Solar Heating
Systems for Residential Buildings" and came up with loads of papers and presentations by the same author so I am reading through them now.

It's generally useful to post links, so we can be sure we're all talking about the same thing. Do you have links for the documents you mention above? And/or give the authors and titles so searches are effective.

There was a great thread on here about stratification but all the links (which people commented were great reading) are dead. I'll try to dig out the old thread and then maybe someone will have the linked documents saved.

If you post the original links and authors/titles here, I've probably got most of them.

I have also found this but not made any headway through it yet: http://www.byg.dtu.dk/upload/institutter/byg/publications/rapporter/byg-r160.pdf

Thanks for this; I don't think I've seen it. Like wookey, I haven't followed the subject for a while now but I'm just getting interested in it again, since I'll need to make a decision later this year.

[dan_c]

Sorry, I didn't post all the links to the papers I'd found as I didn't want to pepper this thread with links that were old news to everyone. I saved all the documents but have no links - I will search for them again later and post up some more links. The author (or at least co-author) for most was Simon Furbo.

These are the Willis documents I do have and have read through which I think you guys have all seen already:

http://www.willis-renewables.com/pdf/UU-solar-syphon-report.doc
http://www.willis-renewables.com/pdf/Performance_Evaluation_Willis_Solasyphon.pdf

I do have the thread with all the dead links bookmarked on my other computer so I will post them up later this evening as I can't find the thread now.

[climber]

I am struggling to justify the cost of a Solasyphon, so was planning to try one of these:

http://www.ebay.co.uk/itm/Stainless-Steel-Heat-Exchanger-Plate-Heat-Exchanger-10-Plates-22-kW-/330731149829?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item4d011cda05

Does anyone know if these will accept standard plumbing fittings? Hard to tell from the description.

[knighty]

I am struggling to justify the cost of a Solasyphon, so was planning to try one of these:

http://www.ebay.co.uk/itm/Stainless-Steel-Heat-Exchanger-Plate-Heat-Exchanger-10-Plates-22-kW-/330731149829?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item4d011cda05

Does anyone know if these will accept standard plumbing fittings? Hard to tell from the description.

yes, standard fittings, you need something like a 1inch bsp to 22mm compression fitting adapter
(or whatever size you need)

the threads have flat tops, so don't take compression fittings directly, but every plumbers merchants / b+q will stock the adaptors :-)

[dan_c]

Here are a few links which may be of interest (apologies to those who have seen these before):

Stratifiers (Bahy Abdel Mesih and Janne Dragsted) http://cms.uni-kassel.de/unicms/uploads/media/Bahy_Janne.pdf

More stratifier info (Peter Vogelsanger, Heinz Marty, Michael Cinelli) http://www.iea-shc.org/publications/downloads/task32-d2.pdf

Side arm vs coil vs mantle tank (Vijay Dwivedi) http://www.esru.strath.ac.uk/Documents/MSc_2009/Dwivedi.pdf

[djh]

Here are a few links which may be of interest (apologies to those who have seen these before):

Stratifiers (Bahy Abdel Mesih and Janne Dragsted) http://cms.uni-kassel.de/unicms/uploads/media/Bahy_Janne.pdf

More stratifier info (Peter Vogelsanger, Heinz Marty, Michael Cinelli) http://www.iea-shc.org/publications/downloads/task32-d2.pdf

Side arm vs coil vs mantle tank (Vijay Dwivedi) http://www.esru.strath.ac.uk/Documents/MSc_2009/Dwivedi.pdf

Thanks for those links. I don't think I've seen the first or third before, so I'll have some reading to do. I have seen the second, which impressed me, and I corresponded with Heinz Marty. He sent me a German paper with some more detail, if you're interested.