Solar combi Heating systems ???

[Flamethrower_]

Hi All,

I'm not talking of integrating a gas combi boiler, my closest theory is a heatstore of some kind (i.e.thermal store, buffer tank utilising a large solar collector)

This topic is aimed at any one who has had experience of these, they seem to do quite a bit of this in Europe and Nordic countries but I have heard nothing of any thing here!
 
I'm looking for any info from any source

Regards

Flamethrower2

[roderickw]

I'm not talking of integrating a gas combi boiler, my closest theory is a heatstore of some kind (i.e.thermal store, buffer tank utilising a large solar collector)

This topic is aimed at any one who has had experience of these, they seem to do quite a bit of this in Europe and Nordic countries but I have heard nothing of any thing here!

Hi Flamethrower2,

There are two German vendors that I'm aware of selling these products in the Uk, Consolar and SonnenKraft.  I couldn't find an installer for Consolar where I live and while I could get two companies to quote for Sonnenkraft both of the installers had concerns about the ethics of the UK importer.  After getting two quotes over 10K I'm presently going down the Navitron route combined with a thermal store.  Not as fancy as the German products but less than half the price.  The UK vendor that sells Pandora heat banks has a configuration which allows stratified charging but even this is probably over specifying.  Moving from 50% (DHW from solar)  to 70% seems to at least double the cost of a system and the more I look at it the additional 20% is hard to justify.

Hope this helps,

Rod

[Flamethrower_]

Hi  roderickw,

Thanks for the reply, Have heard of both of these companies but not really know the type of products they do (will be investigating) but again I  would rather utilise navitron equipment.

Thanks

Rob

[roderickw]

Thanks for the reply, Have heard of both of these companies but not really know the type of products they do (will be investigating) but again I  would rather utilise navitron equipment.

Hi Rob,

I reviewed this topic a while ago so I looked up my notes which may be a bit dated but possibly still useful. 

The Internation Energy Agency ran a project on combisystems that reviewed the commercially available solar combisystems.  The results are a little dated as the work finished in 2003, also very few of the systems are available in the UK. 

The best system they identified used a thermal store with the burner element directly embedded in it, which removed heat losses transferring water from the boiler to the store.  It supports multiple burners, oil, gas and a they were piloting a pellet burner a couple of years ago.  The thermal store also incorporated an element that minimized disruption to the thermal stratification when drawing heat from the tank. 
http://www.solvis.de/6_download/6_pdf2/product-overview_front_gb.pdf
http://www.solvis.de/6_download/6_pdf2/product-overview_back_gb.pdf
Other systems use stratifying charging modules, the Consular one is IMHO neat using the buoyancy of the water at different temps to charge the top and then the bottom of the heat store.  But the Solvis system allowed heat to be injected at 5 levels in the tank rather than just 2.  The Sonnenkraft solution uses diverter valves and multiple inlets on the outside of the tank.  So there are more mechanical elements to fail and heat is lost from the feed pipes as they are outside the tank.  DPS's tank that uses an external heat plate and two inlets into the tank is also similar.

There is lots of background on combisystems as well as a simulation to compare different commercial systems in various locations available at:

http://www.elle-kilde.dk/altener-combi/dwload.html

This simulation is quite limited as it only supports the systems built into it and doesn't allow the modelling of very low energy buildings.

There is also a report on the state of the art for combisystems (in 2003), starting on page 5:

http://www.byg.dtu.dk/upload/institutter/byg/publications/rapporter/byg-sr0314.pdf

One of the key points that comes out when looking at very low energy buildings and combisystems is that the buildings only needs heat when the solar element of the combi system is least able to provide it.   On building that need heat for more months of the year combisystems are more relevant.

Regards,

Rod

[Flamethrower_]

Hi Rod,

Thanks for all the information.
I'm off to inter solar2007 in Freiburg tomorrow morning so hopefully will glean some more information there.
Thanks once again
I now need to get some sleep before an early start tomorrow
Regards
Rob