Passive Pumping Part II

Kevin_in_Denver_2

There’s a new passively pumped solar water heating system

that greatly simplifies the typical cold climate domestic hot water (DHW)

installation.  <a href="http://www.sunnovations.com/">http://www.sunnovations.com/</a>



For me, the holy grail of solar DHW is a system with almost

everything missing:



1.  No pumps

2.  No controller

3.  No sensors

4.  No electricity required

5.  No valves

6.  No stagnation or overheating problems

7.  No chance of freeze damage (freeze tolerant, at least)

8.  PEX  allowed

9.  No heat exchanger

10. No antifreeze



 This system provides 1-8, but it does have an in-tank heat exchanger and propylene glycol.   I’m not on my knees, but not bad!



 It operates by resurrecting the Copper Cricket style geyser pump.  They

solved overheating with a steamback-like method, and can use anyone’s harp

style collector.



Prices are still taboo to discuss here, and they are  taboo on the

company's website also.



 The CEO, Matt Carlson, explains that  "the installed cost varies by region.  It

is influenced by the cost of labor, competition, shipping cost, configuration

of the home, permitting costs, and distributor pricing, etc."



 Ballpark prices can be obtained through direct contact, though:



<a href="http://www.sunnovations.com/forms/contact-us">http://www.sunnovations.com/forms/contact-us</a>



Here’s another discussion of how the Copper Cricket worked:



<a href="http://tinyurl.com/popsci89">http://tinyurl.com/popsci89</a>



And why it fizzled:  <a href="http://www.heatinghelp.com/forum-thread/133419/Steam-Pumping">http://www.heatinghelp.com/forum-thread/133419/Steam-Pumping</a>



I’m just looking for comments and feedback about the

system.   Hopefully one of their “authorized

installers” will post here.

Mark Eatherton

One has to ask...

If this concept was SUCH a good idea, why didn't it catch on fire and take off the FIRST time around?



I still question the use of PEX in any system directly connected to a flat plate absorber. It just makes the hair stand up on the back of my neck. I'd have to see it in operation, under maximum insolation, with minimum demand (spelled Summer stagnation conditions) before I'd believe it.



Interesting concept for sure, but one has to ask...



ME

Kevin_in_Denver_2

The PEX collector loop is safe

It's supposed to be protected from super high temps because when steamback occurs, it all goes into a copper expansion tank. It's similar to the Butler heat dump.



Only copper is directly connected to the panel.

hot_rod

freeze protection

to -22F, with 50% glycol??  Usually 50% is good to -50 or so.  Why the high freeze temperature #?



hr

ABSolar

Auntie Frees - not in Kansas no mo', Toto

Perhaps they're not using Dowfrost HD, but Cryotek Original, which has freeze protection down to, Oh my god, -22 degrees F.   :-)  see link below:

http://www.herchem.com/specs/cryoteck.pdf

ABSolar

Why it fizzled

I read the wall blogs hypothesizing "Why" the Coopper Cricket failed, but I saw nothing substantial to validate why. So, why DID the Copper Cricket fail?  Was it hardware/ design malfunction or marketing issues?

Kevin_in_Denver_2

Mainly Mechanical failures

Tom in Maine said they weren't too reliable in the long term. He was involved with the early versions.



This new company seems diligent in their testing, and have a few hundred installed.

Before I invested any time or money in a bubble pump collector, I'd have to see at least five of them, interview at least 3 different installers and homeowners.... etc.



LOTS of due diligence required for something so new in solar. This industry has been plagued with snake oil and/or insufficient testing.

Sunnovations

Answers from Sunnovations

I thought it may be helpful to chime in on this threat.



1) What happened with Copper Cricket?

In the late 80's, early 90's, the $1B solar hot water industry died after 40% incentive for SHW was stripped by Reagan and oil went down to $10/barrel. 90% of the many companies in the SHW sector went down, including Sage - the manufacturing company of the copper cricket.

They did however quite well, they sold several 1000's systems, and quite a few are still up and running. As far as I heard and read - it was working well. It had a few shortcomings: the heat exchanger under the tank was not very efficient and needed to be flushed regularly to avoid calcium clogging. The system was not scalable (only one collector, while 2 panels is generally most cost effective for single family homes (i.e. shortest payback period). Also the "hump" the top of the unit was super good looking - it was a heavy unit to install. The methanol used as heat transfer fluid was a bit tricky, as it is pretty toxic. Unlike the Sunnovations system, copper cricket did not have a overheat protection system and could loose vacuum over time. The pipe run was full copper (not pex).



Bottom line: the copper cricket did not fail because of technical reasons, but because the market dried up, and - unfortunately - put the company out of business.



2) Overheat protection system.

The overheat protection system in Sunnovations works quite different from the Butler sun system. Butler sun still a pressurized system and excess heat is radiated away. The Sunnovations system is non pressurized (safer) and the fluid will be passively purged from the collectors to an overflow reservoir in case of overheating. So it has a similar (favorable) mechanism as the drain-back system, without the extra tank or energy-consuming pumps.



3) Glycol freeze protection.

A 50/50% propylene glycol mix will provide freeze protection up to about -22 F (which is pretty cold). It depends a little bit which supplier specs you check. In southern states a 30/70 mix can better be used, as more water in the mix helps, at it has a higher heat capacity than glycol.



We also rather have a system without glycol - but all "open" systems have some form of freeze protection, and they all have failed miserably. So for freeze prone areas (pretty much all of USA) - closed loop, glycol based systems are the preferred option.



4) Summary.

Sunnovations uses the same basic principle as the copper cricket system for passively circulating fluid, and added several improvements: choice of standard (OG100) and scalable number of collectors, choice of tanks, overheat protection, vacuum revitalization, maintenance free and efficient heat exchanger, use of PEX.



The Sunnovations system was developed for two key reasons:

1) existing SHW systems are too expensive and take too long to install, which actually is the biggest cost.

2) The prevalent closed loop glycol systems have a whopping 50% failure rate within 10 years.



By eliminating complexity - both issues are addressed. The components that typically fail are gone: pumps, controllers, sensors, wires, valves, expansion tanks, etc. By removing the components that take most time, installation time is reduced (to one day installs). This benefits the home owner (cost savings) and installers (can make a decent margin and do more jobs).



Somebody once summarized the Sunnovations system as follows: It has the same simple configuration as a closed loop glycol system, it has the overheat protection of a drain-back system and it has the simplicity and passive operation of a thermo-syphon system.



We believe all eligible homes in USA (and rest of the world) should (and hopefully will) have a SHW. It just makes sense. It saves 15-30% on the utility bill, payback is typically within 5 years, the systems are affordable for middle class people - while producing the same amount of energy as a full roof of PV panels (for a fraction of the cost of a PV system).



The reduction in CO2 is large, as (coal) power plants produce electricity at low efficiency (up to 40%), while up to 12% is lost in transmission. So a KWh saved with a SHW system really counts.



Last but not least: Sunnovations is the only SHW system 100% made in USA!

Kevin_in_Denver_2

Solar in the 80's, etc.

Thanks so much for weighing in. I was getting a little uncomfortable with all the speculation.



I think this could be a very important step ahead for residential solar energy. Perhaps the biggest problem with most solar DHW designs is that there is always a reliable backup energy source. Certainly that's desirable, but the result is that no one is aware when the solar system isn't working.



At least one company thinks the solution is 100% performance monitoring:

http://www.pvtsolar.com/why_optimize.php



That's a step forward, yes, but most people will still ignore a monitoring system and a $35 higher energy bill.



That's why a simpler, more reliable system that just doesn't fail is needed.



Sunnovations has been awarded a patent on the system (see attachment), If you're inclined to study the operation further. I think they've addressed all the expected problems. Field operational results may uncover some unexpected problems. Minor ones, let's hope.



I would quibble slightly about your timeline on the demise of the Copper Cricket - the tax credit was killed in 1986, and the Copper Cricket wasn't readily available until approximately 1988. So I maintain that the sum of the minor technical issues pointed out in 1) above were more important to the demise of the CC than the overall solar market. That market was effectively quite dead before the CC was even introduced, and a technically superior product should have survived in the small market that remained, just like several flat plate manufacturers and controller companies did.

NRT_Rob

call me crazy

but if you basically have to heat up the water enough to boil to get the pumping action going, doesn't that absolutely kill your collector efficiency?

Sunnovations

Low Temperature Operation

If the system would operate at the normal boiling temperatures (~212'F), it would indeed be very inefficient. However, the system starts operation at about 100'F, this is accomplished by a vacuum in the system.



After installation a pressure test needs to be done to check if the system is air-tight. The Sunnovations system also has a mechanism to automatically re-vitalize the vacuum in case it gets low over time. It does this by purging air from the system using steam from the boiling.

Kevin_in_Denver_2

Getting a geyser pump started

In reading thru the patent, I understand that the geyser pump will start itself and draw its own vacuum on a sunny day. The fluid vapor displaces the air in the system, and it goes out an air vent. On the first cycle, the collector temperature must exceed the boiling point of the fluid. (approx. 220F)



The "Steam Guys" on this forum know all about this phenomenon, but their air vents also let air back in after the heat source is off.



So, if I installed this system and couldn't wait for a sunny day, how can I test the system?



Also, if there is a small vacuum leak, the revitalization effect you describe will eventually deplete the water in the closed system. That's because whenever air is vented, that air is hot and saturated. Might take years, or might take months.



What about the diffusion of O2 and N2 through the Pex? Does that mess up the vacuum eventually? Those gases coming in would be dry, of course.

Sunnovations

more answers to good questions

Air doesn't get back in, because it vents through a one way valve: air can go out, but not back in. Also, it vents into an overflow with a bladder, steam condenses back to fluid, so fluid is not lost/vented off over time.



After we install systems, we pull a vacuum on the system with a vacuum pump. You need some sun to see the system start working. But if a system is properly installed, tested for air-tightness and filled correctly, physics dictate that the system will work.



The system should not have leaks - if it can't keep a vacuum, the performance goes down (see above). The owner is advised to check the pressure/vacuum gauge every once in a while to see if the system holds vacuum. Collectors, tanks and the Sunnovations components are all factory pressure tested, the collectors are sweated and there are only 4 fittings to the pex tubes. The pex tubing has an oxygen barrier - O2 & N2 will not permeate through the wall.

Kevin_in_Denver_2

Reports?

Everything makes pretty good sense from an engineering standpoint.



Please direct us to some operational reports if and when they are available.

Kevin_in_Denver_2

First system in

I installed a Sunnovation system this past week, and it's percolating just fine.

I did a one collector system for a single person, so the flowrate is probably a bit low, but the collector outlet temperature did seem a bit high

Kevin_in_Denver_2

Sunnovation

Anyone else put one of these in recently?