Dump the plumbing and use PV to heat water? - Page 5

where2 · 07-15-13, 10:02 PM

Quote:

Originally Posted by Xringer

No gas lines on my street. So, it's not on the selection list.

This month, the A7 is using 0.412 kWh per day from the grid.
At 16.63 cents per kWh, that comes to 6.85 cents per day. ($2 per month).
Considering we've been taking twice as many showers, I think that's pretty good.

No gas line for me either, not that I want another billing fee whether I use any gas or not. They've recently been replacing gas lines on nearby streets. It ends around the corner, 4 houses away.

Sounds like the A7 is running about 30-45 minutes per day? Are you having to run a dehumidifier, or just the A7 and your mini-split to handle the summer humidity?

Xringer · 07-15-13, 11:34 PM

I'm not sure when it's running. I hardly ever hear it, now that it's sunnier.
I think when it does run, it's most likely after we use a lot of hot water on an overcast day.
In the past, the typical run is between 1 and 2 hours per day. But not on good sunny days..

The A7 isn't doing a lot of water heating, therefore, not much help with the humidity.
The basement ventilation is on during times of low outdoor humidity.
So, we are pulling in dry air from outdoors, when possible.
If it's raining or damp, no fresh air for the basement.

The Sanyos have been working great during this hot spell.
At night, I turn off the den Sanyo and just leave the LR unit set to 22C.
That's the best way to keep it dry in here. If set to 23 or 24, it gets damp.
Because it won't run with outdoor temps at 23 or 24C..
If it's a cool rainy night, I have to set to dehumidifier mode, and that makes it too cold..

ELGo · 07-15-13, 11:37 PM

@#25

I was curious about the $ arithmetic ...

A gallon of heating oil has about 41 kWh. Assuming about a 60% burn efficiency for the boiler (is that about right ?),a gallon will supply 24.6 kWh of heat for about $3.50, or 14 cents a kWh.

PVWatts says that a perfectly sited fixed solar collector for Boston averages 1.54 kWh a year per watt installed if the derate is 1.0 . If your tilting array is E-W you will collect another ~ 30%, or about 2 kWh/watt*year.

What did the PV setup cost ? If say $2/watt and 25 years of use then cost per kWh is 200/50 = 4 cents.

If you are only willing to track out 10 years, then the $2 buys you 20 kWh, = 10 cents a kWh.

So I would say this is not a giant $ saver, but you no doubt had fun setting it up, and it is clean energy. TWO THUMBS UP.

----
It is much less obvious to me that the ASHP would be something I would add since it's annual average COP is less than 2 in Boston, and most of your energy is now supplied from PV.Moreover, the ASHP and PV are not complementary in the sense that during the cold winter when PV is down, the ASHP COP will be poor (approaching 1).

ELGo · 07-16-13, 01:26 AM

One last comment about PV adventures ...

I was much more gung ho about PV until I started reading about very premature PV panel death from the cheap Chinese manufacturers. I expect this to be a growing pain transition kind of thing, but for now I personally would only consider panels from European or American manufacturers. That raises the cost per watt for the panel to well over $3.

Xringer · 07-16-13, 06:31 AM

My 125W panels on the 500w tracking array have some problems. They look pretty bad.
http://ecorenovator.org/forum/solar-...pv-panels.html

But, they seem to be pumping out about the same power levels. So, I'm not too upset.

My panels were purchased on Ebay with my 'hobby money' account.
Since that money was essentially 'free' money I picked up gambling, my solar panel collection cost me almost nothing.

What got me thinking about DHW from PV, was the ever increasing price of #2 fuel oil/diesel fuel.
Which is now about $4 per gallon in this area. Boston Gas Prices - Find Cheap Gas Prices in Massachusetts
When I read the goverment research report on DHW using PV, I liked the idea.

Running the oil burner for 1/2 hour per day at a cost of $2 seemed like a lot for a couple of showers.
But this month, PV DHW assisted by the A7 ASHP, it's about 7 cents a day.
What's that, about 1/28th cost of oil? Wow, the sun is coming up on a clear blue sky!

MN Renovator · 07-16-13, 07:16 AM

Quote:

Originally Posted by ELGo

One last comment about PV adventures ...

I was much more gung ho about PV until I started reading about very premature PV panel death from the cheap Chinese manufacturers. I expect this to be a growing pain transition kind of thing, but for now I personally would only consider panels from European or American manufacturers. That raises the cost per watt for the panel to well over $3.

I've talked to a few solar installers and based on what they say, some cheap Chinese manufacturers are using reject third market cells. Basically the cells get rejected by one manufacturer, go to the next and those cells get rejected and they go to a third manufacturer and generally you get junk in the end. I'm sure there might be a few Chinese manufacturers that are good but you'd have to do research on their track record to figure it out. IMHO you can get good UL listed solar PV at a decent price(sub $1/watt before shipping) from a good manufacturer without resorting to Chinese panels. When you figure how much the inverter, racking, installation, permitting, etc costs it isn't worth putting questionable panels up. I don't think you need to be spending $3/watt though.

OutbackAuzz · 07-16-13, 07:20 AM

Well don't know where I've been but found myself back here.
Earlier post mentioned Evacuated tube hot water, which I've since purchased a 24 tube and hooked it up myself as they say you can, rather easy. $1200 all up went for these as the flat pack black polly tube is old school. These are passive trackers and they heat the water from cold, to easy 80 deg C in a day. I wanted this system, as I have left the electric element in place, and can turn the Circuit B on, on sunless days to boost the temp. Actually at night with the cheaper rate. As for the Gov't supporting PV hot water, there is actually few systems like that here, as the only cost with the Evac tube is the initial outlay, the are no others. The Gov't would pay for ANY solar system, only if the old electric system was removed. I didn't want that.
Maybe this will annoy others, but we haven't had a power bill now for three quarters, we have had three credits, including our first winter credit. First Quarter was $54, second $27, third including 1 1/2 mths winter was $6. Since then I have had installed a fully gas stove, so I'm looking for to the next invoice. So with the 2.1kw solar array pumping into the grid and getting .44c a kWh exporting, and us paying .22c kWh importing until 2028 I'm glad we jumped on the band wagon. They say in 2006 there were 108 houses with solar on the roof, in 2013 1.2 million houses. :-)))))

ELGo · 07-16-13, 08:46 AM

Quote:

Originally Posted by MN Renovator

I've talked to a few solar installers and based on what they say, some cheap Chinese manufacturers are using reject third market cells. Basically the cells get rejected by one manufacturer, go to the next and those cells get rejected and they go to a third manufacturer and generally you get junk in the end. I'm sure there might be a few Chinese manufacturers that are good but you'd have to do research on their track record to figure it out.

More than one problem may be in play. I read that imprudent cost cutting in building the module was the problem, not the solar cells per se. So the electric connections end up having premature failures.

AC_Hacker · 07-17-13, 10:58 AM

Quote:

Originally Posted by ELGo

...If you have a shower that is often used on the second floor and some plumbing skills, check out drain heat exchangers. I think they cost under $400 and conserve about 50% of the hot water energy.
...

Elgo,

Nice job on the shower water heat recovery. Nice video, too!

But I'm curious how you determined, "conserve about 50% of the hot water energy"?

I'm not challenging it... but I would like to know your method of measurement and calculation that brought you to the "50%" number.

Being able to save 50% of energy anywhere is definitely a worthy victory.

Best,

-AC

ELGo · 07-17-13, 02:52 PM

AC,

Sounds like you think I built that device -- I wish!
Just a nifty idea I found on the web.

The commercial heat recovery (HR) units that do measure recovery report 50-60% -- that was the basis for my comment. I don't know if the DIY version does as well. I imagine the flows should be counter-current to maximize heat recovery. I'm planning to read up on flow physics a bit to see if I can come to any reasonable conclusions how to match unit geometry with flow rates. I do know that the water has to spread itself out as a film on the tube to optimize heat transfer. This is the reason the HR units are typically installed vertically.

Tempting to try, isn't it ?

I don't know how much the parts would cost, but I'll be very surprised if it reaches $100.

07-15-13, 11:34 PM	#42
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 115 Thanked 250 Times in 230 Posts	I'm not sure when it's running. I hardly ever hear it, now that it's sunnier. I think when it does run, it's most likely after we use a lot of hot water on an overcast day. In the past, the typical run is between 1 and 2 hours per day. But not on good sunny days.. The A7 isn't doing a lot of water heating, therefore, not much help with the humidity. The basement ventilation is on during times of low outdoor humidity. So, we are pulling in dry air from outdoors, when possible. If it's raining or damp, no fresh air for the basement. The Sanyos have been working great during this hot spell. At night, I turn off the den Sanyo and just leave the LR unit set to 22C. That's the best way to keep it dry in here. If set to 23 or 24, it gets damp. Because it won't run with outdoor temps at 23 or 24C.. If it's a cool rainy night, I have to set to dehumidifier mode, and that makes it too cold.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

07-15-13, 11:37 PM	#43
ELGo Helper EcoRenovator Join Date: Apr 2013 Location: Albuquerque Posts: 66 Thanks: 4 Thanked 3 Times in 3 Posts	@#25 I was curious about the $ arithmetic ... A gallon of heating oil has about 41 kWh. Assuming about a 60% burn efficiency for the boiler (is that about right ?),a gallon will supply 24.6 kWh of heat for about $3.50, or 14 cents a kWh. PVWatts says that a perfectly sited fixed solar collector for Boston averages 1.54 kWh a year per watt installed if the derate is 1.0 . If your tilting array is E-W you will collect another ~ 30%, or about 2 kWh/wattyear. What did the PV setup cost ? If say $2/watt and 25 years of use then cost per kWh is 200/50 = 4 cents. If you are only willing to track out 10 years, then the $2 buys you 20 kWh, = 10 cents a kWh. So I would say this is not a giant $ saver, but you no doubt had fun setting it up, and it is clean energy. TWO THUMBS UP. ---- It is much less obvious to me that the ASHP would be something I would add since it's annual average COP is less than 2 in Boston, and most of your energy is now supplied from PV.Moreover, the ASHP and PV are not complementary in the sense that during the cold winter when PV is down, the ASHP COP will be poor (approaching 1). Last edited by ELGo; 07-16-13 at 01:16 AM..*

07-16-13, 01:26 AM	#44
ELGo Helper EcoRenovator Join Date: Apr 2013 Location: Albuquerque Posts: 66 Thanks: 4 Thanked 3 Times in 3 Posts	One last comment about PV adventures ... I was much more gung ho about PV until I started reading about very premature PV panel death from the cheap Chinese manufacturers. I expect this to be a growing pain transition kind of thing, but for now I personally would only consider panels from European or American manufacturers. That raises the cost per watt for the panel to well over $3. Last edited by ELGo; 07-16-13 at 01:29 AM..

07-16-13, 06:31 AM	#45
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 115 Thanked 250 Times in 230 Posts	My 125W panels on the 500w tracking array have some problems. They look pretty bad. http://ecorenovator.org/forum/solar-...pv-panels.html But, they seem to be pumping out about the same power levels. So, I'm not too upset. My panels were purchased on Ebay with my 'hobby money' account. Since that money was essentially 'free' money I picked up gambling, my solar panel collection cost me almost nothing. What got me thinking about DHW from PV, was the ever increasing price of #2 fuel oil/diesel fuel. Which is now about $4 per gallon in this area. Boston Gas Prices - Find Cheap Gas Prices in Massachusetts When I read the goverment research report on DHW using PV, I liked the idea. Running the oil burner for 1/2 hour per day at a cost of $2 seemed like a lot for a couple of showers. But this month, PV DHW assisted by the A7 ASHP, it's about 7 cents a day. What's that, about 1/28th cost of oil? Wow, the sun is coming up on a clear blue sky! __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

07-16-13, 07:20 AM	#47
OutbackAuzz Lurking Renovator Join Date: Nov 2010 Posts: 16 Thanks: 0 Thanked 0 Times in 0 Posts	Well don't know where I've been but found myself back here. Earlier post mentioned Evacuated tube hot water, which I've since purchased a 24 tube and hooked it up myself as they say you can, rather easy. $1200 all up went for these as the flat pack black polly tube is old school. These are passive trackers and they heat the water from cold, to easy 80 deg C in a day. I wanted this system, as I have left the electric element in place, and can turn the Circuit B on, on sunless days to boost the temp. Actually at night with the cheaper rate. As for the Gov't supporting PV hot water, there is actually few systems like that here, as the only cost with the Evac tube is the initial outlay, the are no others. The Gov't would pay for ANY solar system, only if the old electric system was removed. I didn't want that. Maybe this will annoy others, but we haven't had a power bill now for three quarters, we have had three credits, including our first winter credit. First Quarter was $54, second $27, third including 1 1/2 mths winter was $6. Since then I have had installed a fully gas stove, so I'm looking for to the next invoice. So with the 2.1kw solar array pumping into the grid and getting .44c a kWh exporting, and us paying .22c kWh importing until 2028 I'm glad we jumped on the band wagon. They say in 2006 there were 108 houses with solar on the roof, in 2013 1.2 million houses. :-))))) Last edited by OutbackAuzz; 07-16-13 at 07:27 AM.. Reason: spelling

07-17-13, 02:52 PM	#50
ELGo Helper EcoRenovator Join Date: Apr 2013 Location: Albuquerque Posts: 66 Thanks: 4 Thanked 3 Times in 3 Posts	AC, Sounds like you think I built that device -- I wish! Just a nifty idea I found on the web. The commercial heat recovery (HR) units that do measure recovery report 50-60% -- that was the basis for my comment. I don't know if the DIY version does as well. I imagine the flows should be counter-current to maximize heat recovery. I'm planning to read up on flow physics a bit to see if I can come to any reasonable conclusions how to match unit geometry with flow rates. I do know that the water has to spread itself out as a film on the tube to optimize heat transfer. This is the reason the HR units are typically installed vertically. Tempting to try, isn't it ? I don't know how much the parts would cost, but I'll be very surprised if it reaches $100.