Sun hours

[gregvet]

Meantime warmer days are here, the heat pump runs very little, and I'm already piling
up KWH reserve for the winter of 15/16. Bruce Roe

What temps are you talking about?

[bcroe]

What temps are you talking about?

Today was about 65 deg F, overnight lows hitting 35 to 45. Bruce Roe

[SunEagle]

Today was about 65 deg F, overnight lows hitting 35 to 45. Bruce Roe

Can you put in a good word for warmer weather next week. I will be in Lincoln for a few days starting next Wednesday.

[gregvet]

Today was about 65 deg F, overnight lows hitting 35 to 45. Bruce Roe

Despite our highs around 60 to 75 degrees, our overnight lows have been around 28 degrees F.- Not necessarily conducive to normal heat pumps.

[bcroe]

They were very vague about that last year, net metering was a haphazard,
by hand operation. It was hard to tell what happened. But this year bills are regular again.

I believe they will reset 1 April or whenever they (manually) read the meter. The
plan was I get no credit for extra KWH, but A. I can burn extra heating the other
building, and B. It looks to be a very small amount anyway, which cost me nothing.
I can make 128 KWH in one sunny day. Or, I might run short, too close to call. Bruce

Finally the electric bill reflecting the end of my net metering year came. Last month
they didn't even send one until I requested a copy. Here is the curve of my KWH
reserve, being used up through the winter for electricity and heating the house.

Production for the year ending 1 April was about 28,000 KWH. What happened is
the reserve built up to about 12,400 KWH at the end of Oct, then consumption
exceeded generation. Would there be enough reserve to last the winter? Reserve
bottomed at 691 KWH 5 Mar, then it went up again. The POCO reset it to zero
1 April, I ended up giving them 728 KWH (that cost me nothing). So the reserve
made it with energy to spare. 12 months in a row with no electric energy charge.

This included 6 months use of a new heat pump. 15/16 will get 12 months use, so
the reserve might be even higher. If I can track it better, some may get diverted to
help keep the car shop above freezing. Bruce Roe

[DanKegel]

Its a 3 ton air to air, pretty quick & cheap but only half as efficient as a buried system,
and definitely limited in the coldest months. In a 2000 sq ft, not very well insulted ranch

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
[ EDIT: 1/3 x 2 = 2/3, not 1.5. I was asleep when I wrote that.
So this crude measure gives 20,000 KWH/year as my needs, so my array
should generate 75% of my needs, which isn't bad.]

I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

[SunEagle]

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

Getting rid of the "leaks" is one of the best ways to save money.

I saw a significant decrease in my AC costs when I replaced all of the East and a few of the West facing windows with new ones that had a Low E coating to prevent heat intrusion. You could feel the heat a foot away from the window when the sun was shining directly on it before I installed the new ones.

[bcroe]

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

Thanks for the comments. Plugging leaks is the most effective thing you can do.
Don't remove the gas furnace, its your backup. Heat pumps switching to resistance
heat are terrible.

Check your arithmetic, I estimate you will need 0.65 times as much energy as
used here. However a ranch is the least energy efficient, and outside surface
doesn't go up as fast as square feet, so maybe you only need 0.5 times as much.
If so 15,000 KWH would be in the ballpark. You will ALSO have the advantage
that your heat pump will typically run at higher efficiency in your temperatures,
and backup heat such as I used (resistance heating) can be avoided.

My array has many extra panels to keep up serious production even under some
level of clouds; its rarely clear here. AND, they are oriented to stretch the effective
length of a sunny day, without increasing the size of the rest of the plant.
Bruce Roe

[J.P.M.]

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

1.) Check your math. The heating/cooling DD's are in the ballpark. The load calc is a bit unusual and in any case, the math is wrong. Aside from that, what's your current annual usage ?

2.) As before adding solar, tighten up/insulate/conserve before consideration of new/diff. HVAC equip., and if you proceed w/new equipment, just like solar, don't oversize it.

3.) For the relatively small HVAC loads imposed by low # heating/cooling DD, and also after considerations for load reductions, new equipment may be hard to justify from a cost effective standpoint.

[DanKegel]

Yeah, posted that in the middle of the night after my dog woke me up to warn me of raccoons,
realized the math error as I was going back to sleep.
1/3 x 2 = 2/3, not 1.5. So this crude measure gives 20,000 KWH/year as my needs.
My array should generate 75% of that. Sanity check passed.

About the heat pump... I don't have air conditioning, and my wife really wants it;
replacing the furnace with a heat pump kills two birds with one stone.
So it's not just to reduce carbon emissions, it's also to increase comfort.
I would probably set it to never turn on the resistance strips.

I'm totally onboard the efficiency-first, right-sized HVAC train, have
done an energy audit, discussed it elsewhere on this board. Waiting for
tax refund to start the next step along the path.

[bcroe]

About the heat pump... I don't have air conditioning, and my wife really wants it;
replacing the furnace with a heat pump kills two birds with one stone.

Most furnaces allow an air conditioner/heat pump to just plug in past the
burners; you will need a blower in any case. Bruce Roe

[J.P.M.]

Yeah, posted that in the middle of the night after my dog woke me up to warn me of raccoons,
realized the math error as I was going back to sleep.
1/3 x 2 = 2/3, not 1.5. So this crude measure gives 20,000 KWH/year as my needs.
My array should generate 75% of that. Sanity check passed.

About the heat pump... I don't have air conditioning, and my wife really wants it;
replacing the furnace with a heat pump kills two birds with one stone.
So it's not just to reduce carbon emissions, it's also to increase comfort.
I would probably set it to never turn on the resistance strips.

I'm totally onboard the efficiency-first, right-sized HVAC train, have
done an energy audit, discussed it elsewhere on this board. Waiting for
tax refund to start the next step along the path.

So for the precursor to the sanity check: Do you have an idea of what your actual usage is, say, for the last 12 months ? That's usually where a lot of conservation analysis begins.

[DanKegel]

So for the precursor to the sanity check: Do you have an idea of what your actual usage is, say, for the last 12 months ? That's usually where a lot of conservation analysis begins.

Yep. Here's a summary of 2013 and 2014 usage, plus way too much other info
(not sure how much I trust the energy audit part):

2013:
Craftsman house built ~1910
4550 square feet
89 windows (only 14 double-paned), total area 600 square feet
Two gas furnaces, 125,000 BTU/h each
About 60 x 60W incandescent light bulbs (+ 6 CFLs)
2013 heating degree days: 1501
2013 electric, gas use: 16960 kwh / $5,235.29, 1334 therms / $1,600.88

2014:
All incandescents and CFLs replaced with 6-9W LEDs during summer
Leaky old refrigerator replaced 10/2014
Leaky old dishwasher replaced 11/2014
Daily KWH use dropped as a result from ~40 to ~20
2014 heating degree days: 1037
2014 electric, gas use: 11609 kwh / $2050.43, 948 therms / $1,259.44

energy audit 2/2015:
Blower door test leakage:
20,549 CFM50
estimated 1.58 ACHnat (ASHRAE target 0.35)
Duct test leakage at CFM25
upstairs: 26% leakage
downstairs: 75% leakage (return via unsealed wall cavities)
Modelled heating losses last year (BTU/h)
Air Leakage 43,823 (27%)
Walls 34,456 (21%)
Windows / Doors 28,415 (17%)
Attic Insulation 23,626 (14%)
Duct Leakage and Insulation 19,734 (12%)
Floor 10,256 (6%)
Total 160,310
Modelled cooling losses last year (BTU/h):
Windows / Doors 48,458
Attic Insulation 32,485
Air Leakage 20,407
Walls 16,133
Floor 3,525
Total 121,008
Potential Energy Load Reduction by Improvement Project (%)
Wall Insulation 16.2
Air Sealing 16.1
Duct Upgrade 10.6
Window Upgrade 9.4
Floor Insulation 6.9
HVAC Upgrade ?
Attic Insulation 2.6
Water Heater Upgrade ?

[bcroe]

2014/15 PV Year

The April PoCo bill came; I now have complete info on the first full year of PV grid
connect operation here in northern ILL, land of clouds & snow (but NO forest fires,
earthquakes, water shortages, emissions inspections, Ag construction permits,
electrical black outs, mud slides, outrageously expensive real estate, $5 gasoline,
etc).

I now have 13 months in a row with 0 KWH billed. Not everyone will approve of that,
but the house stayed nice and warm without any uncomfortable "conservation". Only
a bit of propane added when temperatures went well below zero at night. All the rest
is heat pump down to about 10 deg F, and resistance heat below that.

The 15 KW inverters cranked out an annual generation of 27,800 KWH, or 76.1 KWH
per day, or on average 5.07 sun hours per day. That, through all the clouds we have
(didn't see the sun for 27 days in a row in Dec, made 1000 KWH anyway). The worst
days production was 5 KWH; the best was 148 KWH.

This April production was nearly identical to a year ago, 97 KWH per day. What is
different, is a heat pump is keeping the house warm. Instead of using 1411 KWH
at night, I only used 653 KWH; outflow days was up also. The annual reserve built
up in April last year was 174 KWH; this year its 1351 KWH. A nice beginning
for 2015/16.

There are still PV shading issues which can be improved, and needed is an easy way
to change panel tilt for winter snow. Perhaps with panels in just the right position,
annual production can exceed 30,000 KWH. Preliminary drawings already exist.

Some conservation is still going on; if there is enough reserve, the shop building
will probably start using a new heat pump to stay above freezing at all times. I
might try that experiment of feeding some DC direct to a Mini Split. To work in
winter the shop will need a quick propane zap up to 65 F. Bruce Roe

[bcroe]

Rainy Day Energy

Today we got 1/2 inch of rain, starting at 1300 sun time. But it didn't get very dark, the array delivered 80% of
maximum possible KWH for Mon. Time of day isn't a critical thing here, since power is fairly flat much of the day.
Bruce Roe