Residential Solar Relieving Peak Demand

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My understanding is the peak usage period each day in the summer is about 3  
to 6 PM.  A few days ago the forecast was for 95F+ for a couple of days.  
The local electrical utility cooperative sent an email asking members to  
reduce power consumption between 3 and 6.  I complied by cutting off my AC  
during that period.  Before I cut it off I lowered the thermostat a couple  
degrees so the house would cool down a bit and become a thermal storage  
tank.  It seemed to work pretty well as the temperature inside the house  
only reached 79 or 80 each day by the time the A/C was turned back on after  
6.  I decided to use the programming feature on the thermostat to do this  
every day.

My utility has an hourly usage view mode and I see the power consumption  
pattern shift dramatically drawing peak usage earlier in the day when the  
A/C lowers the set point until 3 PM when the set point is raised to 82F  
using 2.5 to 3 kW.  Then the usage drops to a fraction of a kW until the  
thermostat is lowered to 77F after 6 PM where it rises to 3 kW for one or  
two hours until the outside temp drops and power usage drops accordingly.

I don't know yet if this is costing me money or saving me money.  There  
currently is no time factor on the metering currently.  The distribution  
charge by the utility is lower after a base amount of 300 kWHr each month,  
so the incremental rate is lower than the average rate.  Once  I have  more  
data I will add up the costs each day and see if I can tell any difference.

But what is notable is the peak demand shift from 3-6 to the periods before  
and after that period.  If the utility is asking us to cut back on demand,  
it must be important to them.  My utility is a coop and so is not motivated  
by profit.  This could be extended by using thermal storage of some sort.  I  
have read about incorporating beads of coconut oil or a particular type of  
paraffin into wallboard as a phase change material.  Coconut oil melts over  
a range of 74 to 80 degrees (approx) and so would be good for this.  There  
are paraffins which melt in this range as well.  During off peak hours the  
cool air can be passed through a tank of these materials for thermal  
storage, then when cooling is needed the A/C is left off and the warm air  
looses heat to the phase change material as it melts.  I've not been able to  
find good info on the latent heat of melting for either of these materials.  
The coconut oil would be the least expensive, but there is little good data  
on it.  So I can't estimate how large a tank would be needed.

--  

Rick C

Re: Residential Solar Relieving Peak Demand
On Monday, July 17, 2017 at 7:46:42 PM UTC-4, rickman wrote:
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DoE has been experimenting with this concept for some years now.
http://www.pbs.org/wgbh/nova/next/tech/melting-to-keep-cool/
National Gypsum has a drywall product that was used in DoE trials, not sure if it's for sale yet:
http://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/storing-heat-walls-phase-change-materials
These are mainly for solar homes to moderate the internal temperature swings. But there's no reason it could not be used in a situation like yours.

Re: Residential Solar Relieving Peak Demand
snipped-for-privacy@gmail.com wrote on 7/17/2017 8:57 PM:
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Kinda like streamlining cars.  Any car will benefit from using it, but they  
only seem to apply it optimally to the ones that are otherwise designed for  
high fuel efficiency or just plain go fast, or in the case of Tesla - BOTH.

--  

Rick C

Re: Residential Solar Relieving Peak Demand
On Monday, July 17, 2017 at 10:48:32 PM UTC-4, rickman wrote:
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wings. But there's no reason it could not be used in a situation like yours
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A solar chimney is a distinct and economical possibility that works well fo
r solar cooling (oxymoronic I know) when designed properly. You draw outsid
e air in through an underground cooling network and ventilate it out the to
p. https://en.wikipedia.org/wiki/Solar_chimney

Re: Residential Solar Relieving Peak Demand
snipped-for-privacy@gmail.com wrote on 7/18/2017 10:21 AM:
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"Underground cooling network"?  Sounds expensive unless you live next to a  
cavern.  Last time I replaced a heat pump I talked to a geothermal vendor.  
They were talking about some 4 or 5x cost factor and didn't quote prices  
because the risk of what they find underground is all yours.

I have thought about using water cooling, but there are a lot of issues  
there.  My well is likely supplied by water moving through the soil from the  
lake or if not that, the supply rate is huge.  So I think I could use that  
for a heat sink.  It would use a lot less water if done evaporatively, but  
that creates other problems.

--  

Rick C

Re: Residential Solar Relieving Peak Demand
On Tuesday, July 18, 2017 at 2:13:53 PM UTC-4, rickman wrote:
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This is not a mechanical geothermal. The solar chimney cooling is very comm
on on net zero solar homes. Some are built on small lots in high density ho
using neighborhoods (LosAngeles). I think they just bury a long coil of 4-6
" poly pipe about 6' down. You can also do the same if the location of your
 house is favorable. Say a cool wooded northern side and fully exposed sout
hern side. You build a wind wall to bunch the westerly winds on the western
 edge of your house to create a low  pressure region on your southern side.
 Then air from the cool northern side is forced through your north windows,
 through the house, and out the southern side. This age old technique using
 wind walls has been around forever. In modern times it can be supplemented
 by mechanical ventilation for times there is no wind.  

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Re: Residential Solar Relieving Peak Demand
snipped-for-privacy@gmail.com wrote on 7/18/2017 4:09 PM:
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Yes, a hundred years ago when there was no refrigeration, people did all  
manner of things to feel even the slightest bit cooler.  One of the things  
they would do was travel.  They would move out of the swamp called  
Washington, D.C. and spend the summer in Braddock Heights, MD among other  
places.  Those who had real money would travel much further to Canada and  
other points.

Pipes in the ground don't sound inexpensive to me and wind walls don't sound  
effective on days with max temperatures of 95F.  Actually, I have a set of  
pipes some feet down in the ground.  That's my septic system and replacing  
it would cost some $20,000 today.

--  

Rick C

Re: Residential Solar Relieving Peak Demand
On Tuesday, July 18, 2017 at 5:37:40 PM UTC-4, rickman wrote:
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re swings. But there's no reason it could not be used in a situation like y
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ut they
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ell for solar cooling (oxymoronic I know) when designed properly. You draw  
outside air in through an underground cooling network and ventilate it out  
the top. https://en.wikipedia.org/wiki/Solar_chimney
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to a
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es
common on net zero solar homes. Some are built on small lots in high densit
y housing neighborhoods (LosAngeles). I think they just bury a long coil of
 4-6" poly pipe about 6' down. You can also do the same if the location of  
your house is favorable. Say a cool wooded northern side and fully exposed  
southern side. You build a wind wall to bunch the westerly winds on the wes
tern edge of your house to create a low  pressure region on your southern s
ide. Then air from the cool northern side is forced through your north wind
ows, through the house, and out the southern side. This age old technique u
sing wind walls has been around forever. In modern times it can be suppleme
nted by mechanical ventilation for times there is no wind.
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The water based geothermal uses plastic flexible pipe, a few hundred feet p
er ton capacity, they just spiral wind in a trench, turns not touching, and
 fill it in. That operation with parts and material a few thou maximum, rel
atively inexpensive. They do similar for the solar chimney cooling. If you  
pay 20k for a septic field, you must have 20 toilets in your house.  

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Re: Residential Solar Relieving Peak Demand
snipped-for-privacy@gmail.com wrote on 7/18/2017 7:19 PM:
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That must be why they guy wouldn't even quote a figure for the geothermal  
system, because it was so cheap.  The trench would be many feet down at the  
top of the coils.  I expect they would need to be well spaced.  What is the  
point of laying coils close to each other if there isn't water circulating  
past them?  They would be warming/cooling the same bit of soil.  Also, like  
with your septic system, you are assuming ideal conditions.  I am on a piece  
of rock with trees covering everywhere there isn't currently road or septic  
or well.  I know because I've spent time digging post holes through it.

I may be remembering the figure the septic guy through out there and it was  
just a guesstimate, but it was in that ballpark.

If geothermal is so cheap to put in, why do so few use it?  I believe it  
also qualifies for incentives.

--  

Rick C

Re: Residential Solar Relieving Peak Demand
On Tuesday, July 18, 2017 at 8:50:48 PM UTC-4, rickman wrote:
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, not sure if it's for sale yet:
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toring-heat-walls-phase-change-materials
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ture swings. But there's no reason it could not be used in a situation like
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 but they
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igned for
a - BOTH.
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 well for solar cooling (oxymoronic I know) when designed properly. You dra
w outside air in through an underground cooling network and ventilate it ou
t the top. https://en.wikipedia.org/wiki/Solar_chimney
Quoted text here. Click to load it
t to a
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endor..
ices
y common on net zero solar homes. Some are built on small lots in high dens
ity housing neighborhoods (LosAngeles). I think they just bury a long coil  
of 4-6" poly pipe about 6' down. You can also do the same if the location o
f your house is favorable. Say a cool wooded northern side and fully expose
d southern side. You build a wind wall to bunch the westerly winds on the w
estern edge of your house to create a low  pressure region on your southern
 side. Then air from the cool northern side is forced through your north wi
ndows, through the house, and out the southern side. This age old technique
 using wind walls has been around forever. In modern times it can be supple
mented by mechanical ventilation for times there is no wind.
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ll
ings
her
and
 sound
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t of
cing
et per ton capacity, they just spiral wind in a trench, turns not touching,
 and fill it in. That operation with parts and material a few thou maximum,
 relatively inexpensive. They do similar for the solar chimney cooling. If  
you pay 20k for a septic field, you must have 20 toilets in your house.
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People who live in areas of substandard housing rarely buy SEER 40+ systems
.  

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Re: Residential Solar Relieving Peak Demand
On Tuesday, July 18, 2017 at 8:50:48 PM UTC-4, rickman wrote:
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The two main options for ground geothermal are slit trenches and wells.  
Slit trenches work best in new construction with wide open fields that  
haven't been landscaped yet.  The higher the water table the better.  Wells  
work best in retrofits and crowded landscapes like you have.  From reading,  
I believe that 2-300' wells are most common, with multiple wells as needed  
spaced maybe 5-10' apart.  Cap one end of 4 or 6" tubing, extend to the  
bottom of the well, fill with water to hold it down, inject grout around the  
exterior to ensure good thermal contact, insert 2 or 3" tubing to the  
bottom, use a fancy through-tee at the top, and voila, a u-tube.  There was  
a company called Kelix that made inner tubing with exterior fins for  
turbulence that claimed a factor of 2 or 3 improvement in efficiency (so 1/2  
or 1/3 the number of wells), but their web site seems gone.

--  
Regards,
Carl Ijames



Re: Residential Solar Relieving Peak Demand

On Tuesday, July 18, 2017 at 8:50:48 PM UTC-4, rickman wrote:
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The two main options for ground geothermal are slit trenches and wells.
Slit trenches work best in new construction with wide open fields that
haven't been landscaped yet.  The higher the water table the better.  Wells
work best in retrofits and crowded landscapes like you have.  From reading,
I believe that 2-300' wells are most common, with multiple wells as needed
spaced maybe 5-10' apart.  Cap one end of 4 or 6" tubing, extend to the
bottom of the well, fill with water to hold it down, inject grout around the
exterior to ensure good thermal contact, insert 2 or 3" tubing to the
bottom, use a fancy through-tee at the top, and voila, a u-tube.  There was
a company called Kelix that made inner tubing with exterior fins for
turbulence that claimed a factor of 2 or 3 improvement in efficiency (so 1/2
or 1/3 the number of wells), but their web site seems gone.
============================================

Oops, Martin is right, I called this geothermal but it's ground source not  
geothermal.  Need more Diet Coke, sigh.

--  
Regards,
Carl Ijames



Re: Residential Solar Relieving Peak Demand
On 19/07/2017 01:50, rickman wrote:
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That isn't geothermal unless you happen to live in Yellowstone or  
Iceland it is basic ground source heat pump technology - which also  
works quite well in lakes too if you have a big enough one.
(a lot less hassle sinking a pipe in a deep lake too)

Snag is that even if you fit the profile perfectly for it being  
advantageous (eg. retired so wanting continuous heating) by the time you  
include all the maintenance costs it is borderline advantage.

I know a few such installations and on paper they should be good but in  
practice they are a PITA.
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The method works by exploiting the ground temperature being more or less  
constant if you go down a metre or more in the soil. Might not work at  
all in permafrost territory though. Air source heat pump works OK in a  
continental climate but quickly ices up in a cool humid UK winter.

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That isn't geothermal. Geothermal in most areas involves a deep well  
down to truly hot rocks and water coming back that is hot springs  
quality. Bath in the UK has natural hot springs as does Buxton.

Yellowstone is about the only place in the USA where shallow buried  
pipes would be yielding a decent amount of geothermal energy .

--  
Regards,
Martin Brown

Re: Residential Solar Relieving Peak Demand
On Wednesday, July 19, 2017 at 9:18:18 AM UTC-4, Martin Brown wrote:
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They call that geothermal in the U.S. It simply means the heat exchange is  
between the heat transfer fluid and the ground. The other more common techn
ology is called air exchange. It does not have to be in water, and actually
 the most common installation is in soil. And the most common geothermal is
 a dual exchange system wherein they exchange heat between conventional ref
rigerant and an antifreeze solution, and then use a pump to circulate the a
ntifreeze through the ground loop of polyethylene piping.

Re: Residential Solar Relieving Peak Demand
On 19/07/17 00:21, snipped-for-privacy@gmail.com wrote:
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Horse racing is a big thing in Australia. One of our oldest racehorse
stables is still standing at Rouse farm in western Sydney, and it gets
pretty hot there. But walk inside this tin shed on a blazing day, and
it's cool. It's really remarkable. The walls are double skinned, with
perhaps a metre of air space between, and continuous airflow from
outside that's driven by the chimney effect from solar heating. So the
air temperature inside is the same as outside, there is no perceptible
heating inside.

They don't have any buried pipework, but I guess a lot could be learned
from other tricks that the designers used.

Clifford Heath.

Re: Residential Solar Relieving Peak Demand
On 18/07/2017 9:46 AM, rickman wrote:

 > change material as it melts.  I've not been able to find good info on
 > the latent heat of melting for either of these materials. The coconut
 > oil would be the least expensive, but there is little good data on it.
 > So I can't estimate how large a tank would be needed.
 > Unless you find actual figures to prove otherwise, I would have  
thought ordinary water would have a higher specific heat than even the  
latent heat of an oil.  And its cheap, and easy to handle.

I often thought about 2 rainwater tanks, one inside the other, with some  
good insulator between the 2.  Just pump water in from a radiator (  
cooler ) at night, and out to the house in the day.  In winter, reverse  
the process.

Havent got around to sizing yet.  One of those sometime projects.

--  
Regards,

Adrian Jansen

Re: Residential Solar Relieving Peak Demand
On 18/07/17 14:30, Adrian Jansen wrote:
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If you already have hydronic heating, why not? But it's expensive
to fit during a build, and more expensive to retrofit.

Clifford Heath

Re: Residential Solar Relieving Peak Demand
On Tuesday, 18 July 2017 06:05:40 UTC+1, Adrian Jansen  wrote:
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What does the 2nd tank do?


NT

Re: Residential Solar Relieving Peak Demand
On 18/07/2017 5:29 PM, snipped-for-privacy@gmail.com wrote:
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Just a container to hold insulating material around the storage tank.  
Any suitable structure would do.

--  
Regards,

Adrian Jansen

Re: Residential Solar Relieving Peak Demand
Adrian Jansen wrote on 7/18/2017 5:46 PM:
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Build a shed around the tank and when you receive a shipment in styrofoam  
dump the beads or blocks inside.  I wonder how long it would take to fill  
the building around the tank.

--  

Rick C

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