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On Saturday, November 2, 2019 at 10:02:57 AM UTC-7, jla...@highlandsniptechnology.com wrote:
On 2 Nov 2019 09:47:38 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:
dcaster@krl.org wrote...
You understand the trade offs. I had not seen anything
about MPPT'n and it sounds adding one of them would be
cost effective. And easy to add at any time.
You will see a dramatic difference between using a fixed
load resistance, and some form of MPPT. But I was able
to create of form of pseudo MPPT, that's only about 10
to 15% worse than perfect MPPT. To illustrate my scheme
I'll use the values I implemented, to charge the Li-ion
battery in my bee-hive monitor. My sources are nominal
12V solar panels with various capacities. An important
first step is an electrolytic cap charged by the panels.
This holds the node voltage during high converter current
pulses. I used 470uF 25V to handle up to 20W panels.
Next a Schottky diode to handle reverse polarity wiring.
Followed by an efficient buck converter setup to create
a 4.6-volt charging voltage. Next an important item, an
accurate UVLO to shutoff the buck converter whenever the
470uF elec voltage drops below 10 volts. I used a TI
TPS54202H, which has an accurate 1.28V cutoff, with two
1% resistors to set the 10V (or maybe 11V). It's the
hiccuping of the buck converter that implements MPPT.
Finally there's a charging-controller IC, setting the
maximum Li-ion charging current, limiting its voltage
to 4.3 volts. The equivalent in your case would be a
fixed resistor on the 4.6-volt output. When there's
insufficient solar, the buck converter cuts out and
the 4.6-volts drops, but the solar panel is always
operating with a load from 10 to 13 volts, even with
an overcast sky, and it's delivering close to its
maximum available power.
It would make more sense for him to install a standard solar system,
into the AC line, and go to Walgreens and get a little electric heater
for the basement.
Yes, my lazy solution: $100 150W stick on flexible panel + $100 300W micro inverter + $10 heater.
Installation: clean the roof, roll out (17' x 1.5') and stick it on, connect MC4 to micro inverter, plug inverter output into outdoor light or A/C outlet, plug in heater in basement.
On Saturday, November 2, 2019 at 12:34:13 PM UTC-4, jla...@highlandsniptechnology.com wrote:
Sunlight looks bright, but it's low density intermittent energy and
hard to apply. It's even worse in winter. Better to insulate the
basement, probably.
Basements are typically not insulated because being below ground they are close to the optimum temperature. Only above ground walls are insulated.
John doesn't like solar power so he knocks it. His claim of it being "hard to apply" is directly in contradiction of the OP who is looking for a simple solution. In this case I think PV solar may be an easy approach. The only issue is whether it is cost effective or not.
So far the only issue will be finding a MPPT load device.
--
Rick C.
-++ Get 1,000 miles of free Supercharging
-++ Tesla referral code - https://ts.la/richard11209
On Friday, November 1, 2019 at 5:18:33 PM UTC-4, John Larkin wrote:
Solar cells are inefficient, and resistive heaters are inefficient.
The sunlight is hot already, so maybe use a hot water loop, basically
a solar water heater.
I guess a solar cell could run a small circulating pump.
--
On Friday, November 1, 2019 at 5:18:33 PM UTC-4, John Larkin wrote:
Solar cells are inefficient, and resistive heaters are inefficient.
The sunlight is hot already, so maybe use a hot water loop, basically
a solar water heater.
I guess a solar cell could run a small circulating pump.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
You are right. Solar cells are inefficient. The ones thaOn Friday, November 1, 2019 at 5:18:33 PM UTC-4, John Larkin wrote:
Solar cells are inefficient, and resistive heaters are inefficient.
The sunlight is hot already, so maybe use a hot water loop, basically
a solar water heater.
I guess a solar cell could run a small circulating pump.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
t caught my eye say just over 20 %. But solar collectors are not 100% efficient. And plumbing solar collectors is a lot more work. Here ( Delaware ) you either have to drain the system at night so it does not freeze or have an expansion tank to so you can use antifreeze .
Dan
Can you ground mount and just use a hot air collector and maybe a smalledward.ming.lee@gmail.com wrote...
On November 1, 2019, dca...@krl.org wrote:
I think about doing a lot of things that I never actually undertake.
... So another idea is using solar panels in a super simple way...
to provide a little heat to the basement. So it would just be
solar panels connected to a resistive load.
Nothing wrong, but lots of work soldering cells. You also have
to make frame to protect them from breakage. I would rather get
pre-made panels.
Standard 1.0 x 1.6m panels deliver 300W max. These are available
for under $200 each. I have 34 of them on my roof. You might
want two or three of them. While thinking about system, which
includes a large hot-water heater, I considered using a solar
thermal collector system for the hot-water function. But after
adding up required the roof space, and plumbing and long-term
maintenance issues, it was clear solar panels was a tossup.
So I went with solar electricty to heat my hot water.
On Saturday, November 2, 2019 at 12:34:01 PM UTC-7, whit3rd wrote:
On Saturday, November 2, 2019 at 12:03:47 AM UTC-7, Martin Riddle wrote:
On Fri, 1 Nov 2019 13:19:32 -0700 (PDT), "dcaster@krl.org"
dcaster@krl.org> wrote:
... Seems like a good project,...t to provide a little heat to the basement. So it would just be solar panels connected to a resistive load.
Hot water solar collectors are the most efficient out of all solar
things. Most bang for the buck too. They move more heat than PV'S
could.
Absolutely, if you want area heat, solar HEATING of water for pumped circulation
to the basement is a good idea. It's as effective as a south-facing basement
window... except you can turn it off in the summer. Mirror area is cheaper
than solar-panel area,
Yes, mirrors or fixed panels are cheaper, but flexible panels are easier to install without risking damages to the roof. It's a much simpler solution as requested by the OP.
On Saturday, November 2, 2019 at 9:25:47 AM UTC-4, Klaus Kragelund wrote:
Resistive load wonât operate at the maximum power point
If you overshoot, power goes way down
That is very true. In fact, you need a maximum power point tracking (MPPT) load. If you try to draw a fixed amount of power and the solar cell can't deliver that, the resulting power provided goes down a lot more than it should. Draw too much current and the voltage drops disproportionately.
They make MPPT controllers, but they still will only put out some fixed voltage and for any given lighting condition you won't get optimum power. So in reality you need a MPPT load device instead. Not hard conceptually. It's basically a switching regulator but the thing being controlled is power to the load rather than voltage or current. Use a low resistance load and a standard buck topology can be used. A small MCU can measure the voltage and current into the load and dither it to find the optimum power point.
On Sat, 2 Nov 2019 09:25:12 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 9:03 AM, upsidedown@downunder.com wrote:
On Sat, 2 Nov 2019 08:45:25 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 8:25 AM, Klaus Kragelund wrote:
Resistive load wonât operate at the maximum power point
If you overshoot, power goes way down
Overshoot what? I assumed a resistor of appropriate value connected
directly to a solar panel.
If the illumination level drops, the I/V curve "knee" (MPP) will also
move and the fixed resistor will overload the panel.
The panel cannot be overloaded. It is a constant current source and will
survive a short circuit on its output.
At some illumination level, there is an optimum load current. Anything
else wastes power. A solar cell is not a constant-current source.
For a (silly) resistive heater, one could add a big cap and PWM the
heater to find the sweet spot.
On Saturday, November 2, 2019 at 1:02:57 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On 2 Nov 2019 09:47:38 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:
dcaster@krl.org wrote...
You understand the trade offs. I had not seen anything
about MPPT'n and it sounds adding one of them would be
cost effective. And easy to add at any time.
You will see a dramatic difference between using a fixed
load resistance, and some form of MPPT. But I was able
to create of form of pseudo MPPT, that's only about 10
to 15% worse than perfect MPPT. To illustrate my scheme
I'll use the values I implemented, to charge the Li-ion
battery in my bee-hive monitor. My sources are nominal
12V solar panels with various capacities. An important
first step is an electrolytic cap charged by the panels.
This holds the node voltage during high converter current
pulses. I used 470uF 25V to handle up to 20W panels.
Next a Schottky diode to handle reverse polarity wiring.
Followed by an efficient buck converter setup to create
a 4.6-volt charging voltage. Next an important item, an
accurate UVLO to shutoff the buck converter whenever the
470uF elec voltage drops below 10 volts. I used a TI
TPS54202H, which has an accurate 1.28V cutoff, with two
1% resistors to set the 10V (or maybe 11V). It's the
hiccuping of the buck converter that implements MPPT.
Finally there's a charging-controller IC, setting the
maximum Li-ion charging current, limiting its voltage
to 4.3 volts. The equivalent in your case would be a
fixed resistor on the 4.6-volt output. When there's
insufficient solar, the buck converter cuts out and
the 4.6-volts drops, but the solar panel is always
operating with a load from 10 to 13 volts, even with
an overcast sky, and it's delivering close to its
maximum available power.
It would make more sense for him to install a standard solar system,
into the AC line, and go to Walgreens and get a little electric heater
for the basement.
A classic illustration of completely not understanding the problem.
On Saturday, November 2, 2019 at 12:03:47 AM UTC-7, Martin Riddle wrote:
On Fri, 1 Nov 2019 13:19:32 -0700 (PDT), "dcaster@krl.org"
dcaster@krl.org> wrote:
... Seems like a good project,...t to provide a little heat to the basement. So it would just be solar panels connected to a resistive load.
Hot water solar collectors are the most efficient out of all solar
things. Most bang for the buck too. They move more heat than PV'S
could.
Absolutely, if you want area heat, solar HEATING of water for pumped circulation
to the basement is a good idea. It's as effective as a south-facing basement
window... except you can turn it off in the summer. Mirror area is cheaper
than solar-panel area,
On Saturday, November 2, 2019 at 10:30:00 AM UTC-4, John S wrote:
On 11/2/2019 9:25 AM, John S wrote:
On 11/2/2019 9:03 AM, upsidedown@downunder.com wrote:
On Sat, 2 Nov 2019 08:45:25 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 8:25 AM, Klaus Kragelund wrote:
Resistive load wonât operate at the maximum power point
If you overshoot, power goes way down
Overshoot what? I assumed a resistor of appropriate value connected
directly to a solar panel.
If the illumination level drops, the I/V curve "knee" (MPP) will also
move and the fixed resistor will overload the panel.
The panel cannot be overloaded. It is a constant current source and will
survive a short circuit on its output.
I should have said that the constant current is a function of the
insolation. If the insolation drops, the current will go down if the
panel is attached to a resistor.
Look up the I/V curve for a solar array or cell. It is only constant current up to the knee of the curve where the max voltage is approached and the current drops off dramatically. At that point it is constant voltage.
Even so, in the constant current range the voltage drops off dramatically. Maximum power is at a point on the knee between the two.
On 11/2/2019, Rick C wrote:
On November 2, 2019, John Larkin wrote:
On 2 Nov 2019, Winfield Hill wrote:
dcaster@krl.org wrote...
You understand the trade offs. I had not seen anything
about MPPT'n and it sounds adding one of them would be
cost effective. And easy to add at any time.
You will see a dramatic difference between using a fixed
load resistance, and some form of MPPT. But I was able
to create of form of pseudo MPPT, that's only about 10
to 15% worse than perfect MPPT. To illustrate my scheme
I'll use the values I implemented, to charge the Li-ion
battery in my bee-hive monitor. My sources are nominal
12V solar panels with various capacities. An important
first step is an electrolytic cap charged by the panels.
This holds the node voltage during high converter current
pulses. I used 470uF 25V to handle up to 20W panels.
Next a Schottky diode to handle reverse polarity wiring.
Followed by an efficient buck converter setup to create
a 4.6-volt charging voltage. Next an important item, an
accurate UVLO to shutoff the buck converter whenever the
470uF elec voltage drops below 10 volts. I used a TI
TPS54202H, which has an accurate 1.28V cutoff, with two
1% resistors to set the 10V (or maybe 11V). It's the
hiccuping of the buck converter that implements MPPT.
Finally there's a charging-controller IC, setting the
maximum Li-ion charging current, limiting its voltage
to 4.3 volts. The equivalent in your case would be a
fixed resistor on the 4.6-volt output. When there's
insufficient solar, the buck converter cuts out and
the 4.6-volts drops, but the solar panel is always
operating with a load from 10 to 13 volts, even with
an overcast sky, and it's delivering close to its
maximum available power.
It would make more sense for him to install a standard
solar system, into the AC line, and go to Walgreens
and get a little electric heater for the basement.
A classic illustration of completely not understanding the problem.
A classic illustration of not understanding the original requirement:
"So another idea is using solar panels in a super simple way.
Not to replace electricity, but to provide a little heat to
the basement. So it would just be solar panels connected to
a resistive load. No battery storage, no inverter, no
temperature control."
On 11/2/2019 1:25 PM, Rick C wrote:
On Saturday, November 2, 2019 at 9:25:47 AM UTC-4, Klaus Kragelund wrote:
Resistive load wonât operate at the maximum power point
If you overshoot, power goes way down
That is very true. In fact, you need a maximum power point tracking (MPPT) load. If you try to draw a fixed amount of power and the solar cell can't deliver that, the resulting power provided goes down a lot more than it should. Draw too much current and the voltage drops disproportionately.
They make MPPT controllers, but they still will only put out some fixed voltage and for any given lighting condition you won't get optimum power. So in reality you need a MPPT load device instead. Not hard conceptually. It's basically a switching regulator but the thing being controlled is power to the load rather than voltage or current. Use a low resistance load and a standard buck topology can be used. A small MCU can measure the voltage and current into the load and dither it to find the optimum power point..
Have you read and understood the original requirement?:
"So another idea is using solar panels in a super simple way. Not to
replace electricity, but to provide a little heat to the basement. So
it would just be solar panels connected to a resistive load. No battery
storage, no inverter, no temperature control."
I interpret this as just connecting a resistor to the panel and nothing
else.
On Sat, 2 Nov 2019 15:07:49 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 11:38 AM, jlarkin@highlandsniptechnology.com wrote:
On Sat, 2 Nov 2019 09:25:12 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 9:03 AM, upsidedown@downunder.com wrote:
On Sat, 2 Nov 2019 08:45:25 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 8:25 AM, Klaus Kragelund wrote:
Resistive load wonât operate at the maximum power point
If you overshoot, power goes way down
Overshoot what? I assumed a resistor of appropriate value connected
directly to a solar panel.
If the illumination level drops, the I/V curve "knee" (MPP) will also
move and the fixed resistor will overload the panel.
The panel cannot be overloaded. It is a constant current source and will
survive a short circuit on its output.
At some illumination level, there is an optimum load current. Anything
else wastes power. A solar cell is not a constant-current source.
For a (silly) resistive heater, one could add a big cap and PWM the
heater to find the sweet spot.
Have you read and understood the original requirement?:
"So another idea is using solar panels in a super simple way. Not to
replace electricity, but to provide a little heat to the basement. So
it would just be solar panels connected to a resistive load. No battery
storage, no inverter, no temperature control."
If cost doesn't matter, use a roof full of solar panels inefficiently.
I like Win's link:
https://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm
"Solar space heating can be 25 or more times more cost effective than
solar electric (PV) systems"
but there no limit on how inefficient a PV heating system can be made.
On 11/2/2019 11:38 AM, jlarkin@highlandsniptechnology.com wrote:
On Sat, 2 Nov 2019 09:25:12 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 9:03 AM, upsidedown@downunder.com wrote:
On Sat, 2 Nov 2019 08:45:25 -0500, John S <Sophi.2@invalid.org> wrote:
On 11/2/2019 8:25 AM, Klaus Kragelund wrote:
Resistive load wont operate at the maximum power point
If you overshoot, power goes way down
Overshoot what? I assumed a resistor of appropriate value connected
directly to a solar panel.
If the illumination level drops, the I/V curve "knee" (MPP) will also
move and the fixed resistor will overload the panel.
The panel cannot be overloaded. It is a constant current source and will
survive a short circuit on its output.
At some illumination level, there is an optimum load current. Anything
else wastes power. A solar cell is not a constant-current source.
For a (silly) resistive heater, one could add a big cap and PWM the
heater to find the sweet spot.
Have you read and understood the original requirement?:
"So another idea is using solar panels in a super simple way. Not to
replace electricity, but to provide a little heat to the basement. So
it would just be solar panels connected to a resistive load. No battery
storage, no inverter, no temperature control."
On Saturday, November 2, 2019 at 4:12:43 PM UTC-4, John S wrote:
On 11/2/2019 1:25 PM, Rick C wrote:
On Saturday, November 2, 2019 at 9:25:47 AM UTC-4, Klaus Kragelund wrote:
Resistive load wonât operate at the maximum power point
If you overshoot, power goes way down
That is very true. In fact, you need a maximum power point tracking (MPPT) load. If you try to draw a fixed amount of power and the solar cell can't deliver that, the resulting power provided goes down a lot more than it should. Draw too much current and the voltage drops disproportionately.
They make MPPT controllers, but they still will only put out some fixed voltage and for any given lighting condition you won't get optimum power. So in reality you need a MPPT load device instead. Not hard conceptually. It's basically a switching regulator but the thing being controlled is power to the load rather than voltage or current. Use a low resistance load and a standard buck topology can be used. A small MCU can measure the voltage and current into the load and dither it to find the optimum power point.
Have you read and understood the original requirement?:
"So another idea is using solar panels in a super simple way. Not to
replace electricity, but to provide a little heat to the basement. So
it would just be solar panels connected to a resistive load. No battery
storage, no inverter, no temperature control."
I interpret this as just connecting a resistor to the panel and nothing
else.
That was my original thought. Did not know there were cheap MPPT's on the market. That is what is good about SED. One learns things.
Dan
On 2 Nov 2019 09:47:38 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:
dcaster@krl.org wrote...
You understand the trade offs. I had not seen anything
about MPPT'n and it sounds adding one of them would be
cost effective. And easy to add at any time.
You will see a dramatic difference between using a fixed
load resistance, and some form of MPPT. But I was able
to create of form of pseudo MPPT, that's only about 10
to 15% worse than perfect MPPT. To illustrate my scheme
I'll use the values I implemented, to charge the Li-ion
battery in my bee-hive monitor. My sources are nominal
12V solar panels with various capacities. An important
first step is an electrolytic cap charged by the panels.
This holds the node voltage during high converter current
pulses. I used 470uF 25V to handle up to 20W panels.
Next a Schottky diode to handle reverse polarity wiring.
Followed by an efficient buck converter setup to create
a 4.6-volt charging voltage. Next an important item, an
accurate UVLO to shutoff the buck converter whenever the
470uF elec voltage drops below 10 volts. I used a TI
TPS54202H, which has an accurate 1.28V cutoff, with two
1% resistors to set the 10V (or maybe 11V). It's the
hiccuping of the buck converter that implements MPPT.
Finally there's a charging-controller IC, setting the
maximum Li-ion charging current, limiting its voltage
to 4.3 volts. The equivalent in your case would be a
fixed resistor on the 4.6-volt output. When there's
insufficient solar, the buck converter cuts out and
the 4.6-volts drops, but the solar panel is always
operating with a load from 10 to 13 volts, even with
an overcast sky, and it's delivering close to its
maximum available power.
It would make more sense for him to install a standard solar system,
into the AC line, and go to Walgreens and get a little electric heater
for the basement.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
On Saturday, November 2, 2019 at 12:03:47 AM UTC-7, Martin Riddle wrote:
On Fri, 1 Nov 2019 13:19:32 -0700 (PDT), "dcaster@krl.org"
dcaster@krl.org> wrote:
... Seems like a good project,...t to provide a little heat to the basement. So it would just be solar panels connected to a resistive load.
Hot water solar collectors are the most efficient out of all solar
things. Most bang for the buck too. They move more heat than PV'S
could.
Absolutely, if you want area heat, solar HEATING of water for pumped circulation
to the basement is a good idea. It's as effective as a south-facing basement
window... except you can turn it off in the summer. Mirror area is cheaper
than solar-panel area, and there's black vacuum-insulated glass tubes that
are wonderfully effective at heating a water-based fluid (you want some antifreeze).
For my basement, though, i'm more concerned with moisture; it has a resident
dehumidifier.
On 11/2/2019 2:33 PM, whit3rd wrote:
On Saturday, November 2, 2019 at 12:03:47 AM UTC-7, Martin Riddle wrote:
On Fri, 1 Nov 2019 13:19:32 -0700 (PDT), "dcaster@krl.org"
dcaster@krl.org> wrote:
... Seems like a good project,...t to provide a little heat to the
basement. So it would just be solar panels connected to a resistive
load.
Hot water solar collectors are the most efficient out of all solar
things. Most bang for the buck too. They move more heat than PV'S
could.
Absolutely, if you want area heat, solar HEATING of water for pumped
circulation
to the basement is a good idea.  It's as effective as a south-facing
basement
window... except you can turn it off in the summer. Mirror area is
cheaper
than solar-panel area, and there's black vacuum-insulated glass tubes
that
are wonderfully effective at heating a water-based fluid (you want
some antifreeze).
For my basement, though, i'm more concerned with moisture; it has a
resident
dehumidifier.
Why not just heat the air and move it where you want it.
Assuming that won't be far.
                    Mikek
On Saturday, November 2, 2019 at 11:52:51 AM UTC-7, Rick C wrote:
On Saturday, November 2, 2019 at 2:11:20 PM UTC-4, edward...@gmail.com wrote:
On Saturday, November 2, 2019 at 10:02:57 AM UTC-7, jla...@highlandsniptechnology.com wrote:
On 2 Nov 2019 09:47:38 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:
dcaster@krl.org wrote...
You understand the trade offs. I had not seen anything
about MPPT'n and it sounds adding one of them would be
cost effective. And easy to add at any time.
You will see a dramatic difference between using a fixed
load resistance, and some form of MPPT. But I was able
to create of form of pseudo MPPT, that's only about 10
to 15% worse than perfect MPPT. To illustrate my scheme
I'll use the values I implemented, to charge the Li-ion
battery in my bee-hive monitor. My sources are nominal
12V solar panels with various capacities. An important
first step is an electrolytic cap charged by the panels.
This holds the node voltage during high converter current
pulses. I used 470uF 25V to handle up to 20W panels.
Next a Schottky diode to handle reverse polarity wiring.
Followed by an efficient buck converter setup to create
a 4.6-volt charging voltage. Next an important item, an
accurate UVLO to shutoff the buck converter whenever the
470uF elec voltage drops below 10 volts. I used a TI
TPS54202H, which has an accurate 1.28V cutoff, with two
1% resistors to set the 10V (or maybe 11V). It's the
hiccuping of the buck converter that implements MPPT.
Finally there's a charging-controller IC, setting the
maximum Li-ion charging current, limiting its voltage
to 4.3 volts. The equivalent in your case would be a
fixed resistor on the 4.6-volt output. When there's
insufficient solar, the buck converter cuts out and
the 4.6-volts drops, but the solar panel is always
operating with a load from 10 to 13 volts, even with
an overcast sky, and it's delivering close to its
maximum available power.
It would make more sense for him to install a standard solar system,
into the AC line, and go to Walgreens and get a little electric heater
for the basement.
Yes, my lazy solution: $100 150W stick on flexible panel + $100 300W micro inverter + $10 heater.
Installation: clean the roof, roll out (17' x 1.5') and stick it on, connect MC4 to micro inverter, plug inverter output into outdoor light or A/C outlet, plug in heater in basement.
Too bad it won't work.
Which part won't work?
On Saturday, November 2, 2019 at 1:02:57 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On 2 Nov 2019 09:47:38 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:
dcaster@krl.org wrote...
You understand the trade offs. I had not seen anything
about MPPT'n and it sounds adding one of them would be
cost effective. And easy to add at any time.
You will see a dramatic difference between using a fixed
load resistance, and some form of MPPT. But I was able
to create of form of pseudo MPPT, that's only about 10
to 15% worse than perfect MPPT. To illustrate my scheme
I'll use the values I implemented, to charge the Li-ion
battery in my bee-hive monitor. My sources are nominal
12V solar panels with various capacities. An important
first step is an electrolytic cap charged by the panels.
This holds the node voltage during high converter current
pulses. I used 470uF 25V to handle up to 20W panels.
Next a Schottky diode to handle reverse polarity wiring.
Followed by an efficient buck converter setup to create
a 4.6-volt charging voltage. Next an important item, an
accurate UVLO to shutoff the buck converter whenever the
470uF elec voltage drops below 10 volts. I used a TI
TPS54202H, which has an accurate 1.28V cutoff, with two
1% resistors to set the 10V (or maybe 11V). It's the
hiccuping of the buck converter that implements MPPT.
Finally there's a charging-controller IC, setting the
maximum Li-ion charging current, limiting its voltage
to 4.3 volts. The equivalent in your case would be a
fixed resistor on the 4.6-volt output. When there's
insufficient solar, the buck converter cuts out and
the 4.6-volts drops, but the solar panel is always
operating with a load from 10 to 13 volts, even with
an overcast sky, and it's delivering close to its
maximum available power.
It would make more sense for him to install a standard solar system,
into the AC line, and go to Walgreens and get a little electric heater
for the basement.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
I have two electric heaters in the basement already. They are also super simple. They are made from electric furnace heating elements mounted so the air flow is up. They will work fine with convection air flow but each has a 10 inch 240 volt industrial fan which helps to spread the heat around. One is at each end of the basement and plugs in a receptacle for a machine tool. With a single heater running it takes about 20 minutes to have the basement comfortable in Jan.
Dan