Newbie Ignorant Questions
Benign Vanilla
house, and am not sure where to begin. I thought I'd ask some total newb
questions here, and home for the best.
I have a single story rancher that is an approx. 20x40 rectangle. The house
faces due east. I don't know what the exact pitch of the roof is, but I
assume it would be fair to say, it is fairly "typical". Not steep, but not
flat. My first question then, could I mount panels on this roof (I am
thinking the back side, west side for aesthetics) and have enough efficiency
to get hot water?
We currently have a 50 gallon hot water heater fired by gas. It is dieing
and we planned on replacing it with an on-demand system, with no tank. My
second question, could I add a solar hot water system to the on-demand and
stay away from a tank? Or would it be best to have a tank?
Are there sites that can answer these basic questions?
--
BV.
www.iheartmypond.com
bvRE...@tibetanbeefgarden.com
Gary
Benign Vanilla wrote:
> I am more and more seriously considering adding some solar hot water to the
> house, and am not sure where to begin. I thought I'd ask some total newb
> questions here, and home for the best.
>
> I have a single story rancher that is an approx. 20x40 rectangle. The house
> faces due east. I don't know what the exact pitch of the roof is, but I
> assume it would be fair to say, it is fairly "typical". Not steep, but not
> flat. My first question then, could I mount panels on this roof (I am
> thinking the back side, west side for aesthetics) and have enough efficiency
> to get hot water?
>
The solar water heater collector should be mounted facing south, and
tilted up at approximately your local latitude. Variations of plus or
minus 20 degs are OK -- you will still get good performance. However, I
do not think you will get good performance if you mount the panel facing
West. A typical 3 in 12 or 4 in 12 pitch roof would only give you about
15 degs of tilt if you mounted the collector parallel to the roof surface.
You could consider mounting the collector in the south yard (if it can
see the south sky from this position). Or, you could mount it on the
roof using a support system that allows the panel to face south.
The collector should get 6 hours of good sun to work well. You can
download a sunchart at: http://solardat.uoregon.edu/SunChartProgram.html
that will help you work out how much sun the collector will get in a
given position. This is particularly important if there are trees or
houses that might block the sun for part of the day.
> We currently have a 50 gallon hot water heater fired by gas. It is dieing
> and we planned on replacing it with an on-demand system, with no tank. My
> second question, could I add a solar hot water system to the on-demand and
> stay away from a tank? Or would it be best to have a tank?
>
Bosch AquaStar makes an on demand (tankless) heater that they recommed
to use in solar water heating applications (it might the the model
125B). I'm not sure what the difference is, but its probably worth
finding out.
If you use a conventional solar water heating system with a tankless
water heater, you will need a storage tank. If you use the "batch"
(sometimes called ICS) style solar hot water heater (in which the tank
and collector are combined in one unit), you won't need a separate
storage tank. The batch heaters are simple, and make a good DIY
project, but are subject to freezing problems in colder climates.
> Are there sites that can answer these basic questions?
If you google "solar water heater" (or the like), quite a few come up.
There is a recent book by Tom Lane that has an amazing amount of
practical info on solar water heaters -- "Solar Hot Water Systems --
1977 to Today -- Lessons Learned", 2003. I suspect its available in a
few places, but I know this place has it: http://altenergystore.com
Hope this helps -- Gary
>
> --
> BV.
> www.iheartmypond.com
> bvRE...@tibetanbeefgarden.com
>
>
Steve Spence
consideration that the incoming water might be anywhere from 35F to 110F.
--
Steve Spence
Renewable energy and sustainable living
http://www.green-trust.org
Discuss vegetable oil and biodiesel
powered diesels at
http://www.veggievan.org/discuss/
"Gary" <cre...@montanadsl.net> wrote in message
news:409188eb$0$98337$c39...@news.newsgroups.ws...
Benign Vanilla
> The solar water heater collector should be mounted facing south, and
> tilted up at approximately your local latitude. Variations of plus or
> minus 20 degs are OK -- you will still get good performance. However, I
> do not think you will get good performance if you mount the panel facing
> West. A typical 3 in 12 or 4 in 12 pitch roof would only give you about
> 15 degs of tilt if you mounted the collector parallel to the roof surface.
> You could consider mounting the collector in the south yard (if it can
> see the south sky from this position). Or, you could mount it on the
> roof using a support system that allows the panel to face south.
Sorry, my bad...I thought I had implied that I would mount the units on some
sort of rack to increase their angle towards the south. As my roof has a due
east face and a due west face, I figured I'd have to raise one end of the
panels up a bit to get better exposure. I didn't make that clear.
I can't mount anywhere in the yard safely. Not with two boys and a
neighborhood full of kids. LOL. The roof is my only option.
> The collector should get 6 hours of good sun to work well. You can
> download a sunchart at: http://solardat.uoregon.edu/SunChartProgram.html
> that will help you work out how much sun the collector will get in a
> given position. This is particularly important if there are trees or
> houses that might block the sun for part of the day.
Awesome site! Thanks! This leads me to another question. If I estimate very
conservatively that with the panels on the west facing roof, I would get 5.5
hours of good sun, could I benefit from one panel on the east side, and one
on the west? Both would get about 4-5 hours of really good direct sun, but
at different times. Would the net effect be better then both on one face of
the roof? Is that question clear?
>
> > We currently have a 50 gallon hot water heater fired by gas. It is
dieing
> > and we planned on replacing it with an on-demand system, with no tank.
My
> > second question, could I add a solar hot water system to the on-demand
and
> > stay away from a tank? Or would it be best to have a tank?
> >
>
> Bosch AquaStar makes an on demand (tankless) heater that they recommed
> to use in solar water heating applications (it might the the model
> 125B). I'm not sure what the difference is, but its probably worth
> finding out.
I have been looking at the Bosch systems. I am aware of those.
> If you use a conventional solar water heating system with a tankless
> water heater, you will need a storage tank. If you use the "batch"
> (sometimes called ICS) style solar hot water heater (in which the tank
> and collector are combined in one unit), you won't need a separate
> storage tank. The batch heaters are simple, and make a good DIY
> project, but are subject to freezing problems in colder climates.
This is where my confusion gets worse. I am definately in a hard freeze
area, so I will need a system whereby there is a heat exchange. So does that
mean I have to have a tank? Or just a heat exchanger?
> > Are there sites that can answer these basic questions?
>
> If you google "solar water heater" (or the like), quite a few come up.
>
> There is a recent book by Tom Lane that has an amazing amount of
> practical info on solar water heaters -- "Solar Hot Water Systems --
> 1977 to Today -- Lessons Learned", 2003. I suspect its available in a
> few places, but I know this place has it: http://altenergystore.com
I appreciate all of your information. It is very helpful.
--
BV.
www.iheartmypond.com
bvRE...@tibetanbeefgarden.com
Benign Vanilla
"Steve Spence" <ssp...@green-trust.org> wrote in message
news:409193bf$1...@newsfeed.slurp.net...
> the S series aquastars allow modulation of the gas valve, taking into
> consideration that the incoming water might be anywhere from 35F to 110F.
>
> --
> Steve Spence
> Renewable energy and sustainable living
> http://www.green-trust.org
> Discuss vegetable oil and biodiesel
> powered diesels at
> http://www.veggievan.org/discuss/
Does this imply that if I want 100F water, and the solar array is passing in
90F water, the on-demand unit will put 10F of effort in? I guess what I am
asking is if I loop the two together is the on-demand unit going to try and
heat already hot water and just waste energy or will it only heat when and
to an amount needed?
--
BV.
www.iheartmypond.com
bvRE...@tibetanbeefgarden.com
Ecnerwal
"Benign Vanilla" <BVre...@tibetanbeefgarden.com> wrote:
> Awesome site! Thanks! This leads me to another question. If I estimate very
> conservatively that with the panels on the west facing roof, I would get 5.5
> hours of good sun, could I benefit from one panel on the east side, and one
> on the west? Both would get about 4-5 hours of really good direct sun, but
> at different times. Would the net effect be better then both on one face of
> the roof? Is that question clear?
Mount them both right on the south edge of the roof, they'll be shaded
less of the time. For that matter, you could also hang them from the
south gable wall on angle brackets (better). Anyway, if the control
system is set up to pump only the panel that's got good sun when one
does and the other does not, yes, this should work somewhat better. If
(for simplicity and expense reasons) the pump is set up to pump both at
the same time, having similar exposure for both panels (with appropriate
storage) is better.
> This is where my confusion gets worse. I am definately in a hard freeze
> area, so I will need a system whereby there is a heat exchange. So does that
> mean I have to have a tank? Or just a heat exchanger?
You need a tank. You have to have someplace to store solar heated water,
so that you can draw on the solar heated water (heated when the sun
shines) to feed your tankless water heater (when you need hot water). A
_large_ (80 or 120 gallon) electric water heater with extra insulation
is probably the best bet ("solar storage tanks" are essentially the same
thing without heating elements, but due to lower sales volume, they
usually cost more - go figure...).
You appear to have an aversion to tanks. This might be helped by
locating a floor drain or pump to catch any disasters, perhaps with a
tray under the water heater and a drain line running to the floor drain
or sump. Actually doing a yearly or every 6 months flush on the tank
might also help (install a better drain valve when the tank is new and
you can still get the original crummy drain valve off).
--
Cats, Coffee, Chocolate...vices to live by
Benign Vanilla
"Ecnerwal" <Lawren...@SOuthernVERmont.NyET> wrote in message
news:LawrenceSMITH-E0D...@news.verizon.net...
Aversion? LOL. No, well maybe a little. We currently have a 50 gallon
behemoth, and most of the energy goes to heating and reheating because we
don't use it all. I hear that thing going on all night. It's dieing so I
planned on replacing the tank with a tankless on-demand system. I figured it
would be more energy efficient, and we'd regain that last space which is
currently at a premium. Then I got the idea for solar so I am trying to work
an plan where I have solar and the on-demand combined. I am not adverse to a
tank, but I'd like to minimize if possible.
How small of a tank can I use?
--
BV.
www.iheartmypond.com
bvRE...@tibetanbeefgarden.com
Ecnerwal
"Benign Vanilla" <BVre...@tibetanbeefgarden.com> wrote:
> How small of a tank can I use?
As small as you like - but small size limits the amount of good your
solar system can do you, unless all your hot water use is at a slow rate
and during days and times the sun is actually shining. For a given size
collector, a small tank will overheat more quickly when no hot water is
being used and the sun shines - and at that point your solar energy is
being wasted, not stored for future use. The small tank will also run
out faster when hot water is called for, so more gas will be used than
would be the case with a larger storage tank, for the same hot water use.
For electric heaters (which are simpler to insulate well due to the lack
of a flue) there is very little difference in energy use for a properly
insulated tank and a tankless heater if there is any hot water use going
on - this was discussed either here or in alt.energy.homepower not that
long ago, with actual measurements.
With gas, the uninsulated (has to be, or the heat cannot get in from the
flame) flue passage in the tank makes more of a difference between tank
and tankless. Still, with proper tank insulation, you may be
oversimplifing how much energy you waste on the tank, .vs. tankless,
unless you use very little hot water indeed. Most of the energy goes to
heating up cold water - less goes to losses from keeping heated water
hot.
With solar, the input energy is effectively free (not quite, there is
some energy used to pump things) so heating up a tank (especially a very
well insulated tank) costs very little, while not having enough storage
means paying for gas to heat cold water when the preheated water runs
out. Thus, bigger really is better; you'll have to make the call about
the space used .vs. the benefit derived. A 50 gallon water heater is
hardly a behemoth.
Benign Vanilla
"Ecnerwal" <Lawren...@SOuthernVERmont.NyET> wrote in message
All good points. This makes me think that maybe I should replace my current
tank system, with another tank and add the solar to it. Probably a better
deal then adding a tankless on demand systems, and then retrofitting a
tanked system to support the solar. Thanks for the post.
As for the behemoth measurement...I guess it's in the eye of a beholder eh?
:)
--
BV.
www.iheartmypond.com
bvRE...@tibetanbeefgarden.com
Steve Spence
to necessary.
see http://www.solardepot.com/pub/dpc_st_igwh.htm
--
Steve Spence
Renewable energy and sustainable living
http://www.green-trust.org
Discuss vegetable oil and biodiesel
powered diesels at
http://www.veggievan.org/discuss/
"Benign Vanilla" <BVre...@tibetanbeefgarden.com> wrote in message
news:c6tmuh$fl1nk$1...@ID-152254.news.uni-berlin.de...
LarenCorie
> Aversion? LOL. No, well maybe a little. We currently have a 50 gallon
> behemoth, and most of the energy goes to heating and reheating because we
> don't use it all. I hear that thing going on all night. It's dieing so I
> planned on replacing the tank with a tankless on-demand system. I figured
it
> would be more energy efficient, and we'd regain that last space which is
> currently at a premium. Then I got the idea for solar so I am trying to
work
> an plan where I have solar and the on-demand combined. I am not adverse to
a
> tank, but I'd like to minimize if possible.
With Solar, you need a tank. That tank might be inside of the
collector up on the roof, in a passive thermosyphon or batch
type collector, or in the house where your present standard
tank is, with an active system. Either way it needs to be big
unless you are in a climate that has sunshine every day. Tanks
of 80 gallons or more are standard.
Instead of screwing up the looks of your house, and lowering
its resale value, with an unprofessional tacky collector installation
up on racks above your roof, have your collectors mounted flush
to your west or east roof. The efficiency will be lower, than on
a southern exposure, so you will need to compensate by increasing
your collector area by 50-100%, depending on your latitude, how
far they are aimed from south, and the pitch of the east/west roof
where you mount the system. But, you will also not have the costs
involved in a complicated tilt rack mounting. That will give you a
much more professional installation, that will look like skylights,
not an ugly piece of machinery. In most cases the end cost of
extra collector, instead of extra tilt racks and labor, is close.
I worked with a company that installed thousands of hot water
systems. That was the best way for a house without an optimum
south facing roof. Tilt racks on weird angles are really tacky.
Most people who make that mistake, end up paying to have the
collector system taken down, especially when they want to sell
the house for top dollar.
-Laren Corie-
Benign Vanilla
"LarenCorie" <Laren...@axilar.net> wrote in message
news:1098rcr...@corp.supernews.com...<snip>
> With Solar, you need a tank. That tank might be inside of the
> collector up on the roof, in a passive thermosyphon or batch
> type collector, or in the house where your present standard
> tank is, with an active system. Either way it needs to be big
> unless you are in a climate that has sunshine every day. Tanks
> of 80 gallons or more are standard.
I am hoping to replace my current 50 gallon gas fired unit, but feed it with
solar, so I use less gas. I don't have room for an 80 or up.
> Instead of screwing up the looks of your house, and lowering
> its resale value, with an unprofessional tacky collector installation
> up on racks above your roof, have your collectors mounted flush
> to your west or east roof. The efficiency will be lower, than on
> a southern exposure, so you will need to compensate by increasing
> your collector area by 50-100%, depending on your latitude, how
> far they are aimed from south, and the pitch of the east/west roof
> where you mount the system. But, you will also not have the costs
> involved in a complicated tilt rack mounting. That will give you a
> much more professional installation, that will look like skylights,
> not an ugly piece of machinery. In most cases the end cost of
> extra collector, instead of extra tilt racks and labor, is close.
> I worked with a company that installed thousands of hot water
> systems. That was the best way for a house without an optimum
> south facing roof. Tilt racks on weird angles are really tacky.
> Most people who make that mistake, end up paying to have the
> collector system taken down, especially when they want to sell
> the house for top dollar.
That's a good piece of advice, and I intend to follow it. If the array looks
like hell, my wife will kill me.
--
BV.
www.iheartmypond.com
bvRE...@tibetanbeefgarden.com
Gary
I think that this is basically good advice, but with your fairly low
pitch roof, and your fairly high latitude, you should be aware that you
will not get much sun on the collector panel during the mid winter
months. The sun just does not get high enough in the winter to put a
lot of useful sun on a panel with low tilt.
The table below compares the daily total solar radiation received by 1
square foot of panel for a horizontal panel to a panel tilted at an
angle equal to latitude and aimed south (the ideal case) -- this is for
a latitude of 48degrees (Northern US). These numbers are for sunny days.
Horizontal Tilted 48 deg to South
Jan 596 1478 BTU/ft^2-day
Feb 1080 1972
Mar 1578 2228
Apr 2106 2266
May 2482 2234
Jun 2626 2204
Jul 2474 2200
Aug 2086 2200
Sep 1522 2118
Oct 1022 1860
Nov 596 1448
Dec 446 1250
So, the horz panel does fine in the summer, but is not so good in the 3
or 4 months of winter. As suggested, you could increase the panel area
to partially offset this.
Good Luck -- Gary
Chuck Yerkes
> In article <c6tml2$fq47m$1...@ID-152254.news.uni-berlin.de>,
> "Benign Vanilla" <BVre...@tibetanbeefgarden.com> wrote:
>
>>Awesome site! Thanks! This leads me to another question. If I estimate very
>>conservatively that with the panels on the west facing roof, I would get 5.5
>>hours of good sun, could I benefit from one panel on the east side, and one
>>on the west? Both would get about 4-5 hours of really good direct sun, but
>>at different times. Would the net effect be better then both on one face of
>>the roof? Is that question clear?
When the sun is in the west, it's usually warmer. For all that means.
In your area (you don't say) that might mean it clouds up. I get fog
around 4-5PM everyday.
>>This is where my confusion gets worse. I am definately in a hard freeze
>>area, so I will need a system whereby there is a heat exchange. So does that
>>mean I have to have a tank? Or just a heat exchanger?
What area? Got a state? Oregon hard freezes, but not like Michigan.
Is it possible to just run empty in the winter with these (turn it off)
and use it when the water isn't going to freeze and screw the heat
exchange? It's not quite AS effective, but for 7-8 months/year it means
you don't need anti-freeze and a big tank.
> You need a tank. You have to have someplace to store solar heated water,
> so that you can draw on the solar heated water (heated when the sun
> shines) to feed your tankless water heater (when you need hot water). A
> _large_ (80 or 120 gallon) electric water heater with extra insulation
> is probably the best bet ("solar storage tanks" are essentially the same
> thing without heating elements, but due to lower sales volume, they
> usually cost more - go figure...).
Well, some tank to do heat exchange. In my non-hard freeze area (or
rare), I can get away with a 10-20 gallon tank in front of a tankless
heater. Showers will likely not use more than that. If something does,
then I'm in a "no solar" state and the tankless heater just does what it
does.
I just picked up a bunch of info at a Green Fair in Berkeley today
(small, in a small park). Was looking at a Japanese tankless (50 years
in .ja and 10 years in the US) on display. It heats the water UNTIL
it reaches the set point (110, 115).
Tomorrow AM, I meet with a solar contractor. He had an issue with a
client who was storing water that was TOO hot. Water sits around and
recircs and heats and recircs and heats and comes out at Tea making
temps. I think the solution was just a bigger (25gal) storage tank).
> You appear to have an aversion to tanks. This might be helped by
> locating a floor drain or pump to catch any disasters, perhaps with a
> tray under the water heater and a drain line running to the floor drain
> or sump. Actually doing a yearly or every 6 months flush on the tank
> might also help (install a better drain valve when the tank is new and
> you can still get the original crummy drain valve off).
I'd suggest that it's size. I have room for either my 50 gal tank or
a tankless with a little bitty solar tank (eg, 100 gallons? Perhaps in
the guestroom).