Drainback and without glycol, new solar systems approaching the heating market.

[heinbloed]

Several solar companies are now manufacturing pressure free/open/vented solarsystems.These systems are 10-30% more efficient (!)compared to the standard closed systems.The major new features are: a.)direct feeding of the storage tank,no heatexchanger b.) no pressure, no pressure-proof piping system, no pressure-proof tanks, no pressure-proof collectors c.) they're self-protecting drainback-systems and accordingly d.) they work without frost-proof, no glycol.
These features increases the thermal harvest by 10-30%, a major step in efficiency.
The tanks can be cheap plastic tanks.Leightweight, easy installed even when larger volumes have to be stored.
Here some manufacturers, all with the solar key mark:
www.pelletsworld.com
www.conergy.ch "Biotech Drainmaster BDM"
www.consolar.de "Sunrise2000"
www.cdsolar.it "ESFVD200/300"
www.ese-solar.com "Dynasol" and "Domosol"
www.rotex.de "Rotex Solaris"
www.solahart.com "Streamline" and "Powerpack 10kW"
www.vaillant.de "Aurostep VSL S150/S250"
www.wagner-solar.de "Secusol 160-1/250-1/250-2/350-2"

Some of these manufacturers are already present on the Irish market.
All Data above from the magazine"Sonne,Wind,Waerme" 14/2008,page 86-87.

[Viking House]

Are the Sunshore ones you used "drainback without glycol"?

[heinbloed]

In principle-yes.With the difference that a flat panel collector is actually draining back totally, to the last drop, avoiding build-up of ice or steam=pressure increase. The vacuum tubes however would have to be turned upside down to get to the same result=total draining. The "Sunshore" tube collectors that I used are vented systems, open to let out steam pressure. Ice build-up can't occure due the vacuum-insulation. In severe weather circumstances (arctic nights) the ice that could build-up in the tubes will be floating on warm water and has -thanks to the cylinder shaped inner tube- enough expansion capacity upwards without bursting the glass tube.It would take several days of permanent frost in absolute darkness to cause a total freeze. This can't happen in our part of the world, the "eternal night" is only to be observed at the poles.
So even if the water in the tubes has froozen the first touch of indirect,murky daylight would melt it again. Thanks to the vakuum insulation external frost (cold atmospherical air)has hardly any cooling impact on the tubes.And as long as there is some slight light available the tubes are instantenous warming up.Not much if the light is very little, but well above freezing point.
The company Arcon, bussy in the megawatt-class of thermal collector fields, is now planning the installation of drainback thermal collectors in Greenland, well above the arctic circle, for district heating.Drainback of course, no glycol mixture will withstand 180 days of darkness and being energy efficient the same time. Or 180 days of permanent sun exposure, this would boil away all water.
See www.arcon.dk