Thermosiphoning solar panels

zvalve

More than 30 years ago I purchased a hot water solar panel for use in a thermosiphoning system for the roof of a small camp. I forgot the name of the company I bought it from but they were from Florida and the panel was made in Israel. Any information on Florida based passive solar system sellers as described would be great. Anyone know where to purchase panels for thermosiphoning systems. My system worked great with no controls or moving parts except I had to hand pump water to a rooftop supply tank I am thinking of using a thermosiphoning system at my house on Long Island, NY preheat domestic hotwater in the warmer months say April to November. Any feedback.

Jamie Hall

Generally in a climate such as Long Island you will be looking at one of two types of solar heating for water: drainback systems, in which the water is drained out of the panel when not in use, and pumped systems with antifreeze in them.

And there any number of suppliers of such panels...

hot_rod

The tank needs to be above the collector for a thermosiphon to work

In warm climates across the pond you see collectors with a horizontal tank right above them mounted on the roof. Mostly evac tube assemblies. No real freeze protection.

Chromgen (sp) was imported into Florida from Israel. I was a dealer once😊

I too would go with a plain water drain back if the tank can be below the collector. A ladder style collector.

US built collectors AET out of Florida Sun Earth or Heliodyne out of California

Larry Weingarten

Hi, Amcor was a thermosyphon system from Israel. It’s not hard to make your own system with a conventional collector and horizontal repurposed two element electric tank. I wouldn’t do this where it could freeze. ... Or go with an inefficient poly tube coil collector and a PV powered pump.

Yours, Larry

jumper

Below is what I posted last May. If you can obtain photovoltaic panels without expense of inverters and interfaces .....

>>DHW is best use of solar energy because it's relatively easy to store and control the harvested energy. Simplest and least expensive storage is thermal. To keep tanks reasonably sized we need extra hot water, say 200° or even 250° or even hotter.

PV resistance is simpler and (I think) less expensive than a concentrating thermal collector. PV is supposed to be efficient at cold temperatures whereas thermal works otherwise.

Some time ago I angered some people here by declaring solar thermal defunct. <<

hot_rod

I doubt ST will ever be defunct, the numbers need to be crunched carefully.

55% efficiencies up to 90% efficiencies with ST, fairly easily accomplished

12- 15% with PV?

The key with ST is a consistent, low temperature load, pool heat DHW pre-heat, etc.

Pool heating in mild climate for example, unglazed plastic collector where ambient and pool temperatures are close, near 90% efficiencies. How does PV- thermal come even close to that? PV to a heat pump, looks a bit better.

100° from a flat plate on a 20° ambient day 37% efficiencies.

jumper

I agree that solar thermal has some easy applications like a swimming pool which HotRod says is inherently a low temperature energy storage device.

But to store solar energy for DHW or heating: cheapest method is very hot water from PV-resistance heater. Alternative is concentrated solar. More efficient but more complicated.

hot_rod said:

I doubt ST will ever be defunct, the numbers need to be crunched carefully.

55% efficiencies up to 90% efficiencies with ST, fairly easily accomplished

12- 15% with PV?

The key with ST is a consistent, low temperature load, pool heat DHW pre-heat, etc.

Pool heating in mild climate for example, unglazed plastic collector where ambient and pool temperatures are close, near 90% efficiencies. How does PV- thermal come even close to that? PV to a heat pump, looks a bit better.

100° from a flat plate on a 20° ambient day 37% efficiencies.

Jamie Hall

And good passive solar design and architecture for space heating is really remarkable. The result doesn't have to look weird or have poor interior functioning -- just be thoughtfully done. One house I built recently... well, almost 20 years ago! -- is almost indistinguishable either inside or outside from any other two story saltbox design, such as you see in many subdivisions. The cost was about 5% over "normal" construction (mostly in brow-beating the contractors on careful insulation and draught sealing). It runs down to about 10 F on no auxiliary heat, and has a small wood stove for colder weather. It's only semi-passive -- there is a high volume low velocity fan (quarter horse) and some ducting to move heat around).

hot_rod

If someone were to give me 25K to put any solar on my home, no doubt PV would be my choice. If I had a year 'round pool costing me hundreds a month to heat, I may reconsider, at my 12/Kwh rate, under 100 per month electric bill.

Yes my next home will be as passive as possible. Lot of technology available today to get to net zero with careful design.

jumper

Another thing to consider is that when you need it most –like when it's very cold– thermal performance decreases while PV improves.

hot_rod

i would advise against glycol on a vacation or seasonal home. You end up over heating the glycol when the spend a lot of time in stagnation conditions, no load