I've always wondered why the solar panel makers don't put water tubing on the back side of the panels. Boost the efficiency, and get hot water for the house or pool at the same time. Seems like a no-brainer. {shrug}
Unfortunately for me, I have large trees shading the house (big enough that I'm hoping I'm coming out ahead with lower air conditioning bills), and a roof angle exposure that is not solar-friendly even if they weren't there. So I was thinking, if I had space for just a few panels, perhaps I could go low-tech with a system built from a scrap UPS. After all, I've got an APRS station - PC, TNC, radio, and internet connection - using power constantly, and I often find perfectly good UPSs being tossed out (i.e. free) because the battery is shot and not worth replacing.
Put the solar cells in place of the UPS' battery, and modify the power failure detect circuitry to work backwards - give preference to the battery/solar side, only switching to the line side if there is insufficient "battery" power. This will give me free 120 vac whenever the sun shines. At night, it would power-fail back over to the line, and only then would the power company's meter start to spin. I'd probably put a regular UPS down stream from the hacked-up one, in case the failover/back from line to solar wasn't real clean.
The biggest problem I see is that most of the solar panels available these days are in the 50-60 volt range, which means that you'd need to do a conversion down to battery voltage first. (Maybe put two panels in series and run them into a regular 12v DC power supply?)
Now, I just need to find a source of free-to-cheap solar panels. I almost bought a set at a local Ham swap ($10 ea) that had cracked surface glass but were otherwise functional, but I didn't think they'd survive the trip home in my car (no place big enough to lay them flat). (I'd need to weatherproof them too....)
Anyway, just a thought...
Greg KO6TH
Date: Thu, 1 Oct 2009 18:46:28 -0700 From: ptrowe@yahoo.com To: bruninga@usna.edu; amsat-bb@amsat.org; wb3jfs@cox.net Subject: [amsat-bb] Re: Solar Power (I was wrong)
One of my friends installed a water spray system to cool the panels since they lose efficiency fast as the temperature goes up. Also, it doesn't take much dust or bird poop to cut the efficiency. So if you install a system, be prepared to get on the roof every month or so to clean the panels.
Regards,
Pete
WA6WOA
_________________________________________________________________ Hotmail® has ever-growing storage! Don’t worry about storage limits. http://windowslive.com/Tutorial/Hotmail/Storage?ocid=TXT_TAGLM_WL_HM_Tutoria...
Hi Greg and all,
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Greg D. Sent: vrijdag 2 oktober 2009 6:13 To: ptrowe@yahoo.com; bruninga@usna.edu; amsat-bb@amsat.org; wb3jfs@cox.net Subject: [amsat-bb] Re: Solar Power (I was wrong)
I've always wondered why the solar panel makers don't put water tubing on the back side of the panels. Boost the efficiency, and get hot water for the house or pool at the same time. Seems like a no-brainer. {shrug}
I guess this is too complex for the additional gain in efficiency? According to the documentation, a raise in temperature of 25K decreases the efficiency by about 8-10% for the Suntech panels I have installed. Being 50degrees North, temperature is rarely a problem for me anyway. :-)
Unfortunately for me, I have large trees shading the house (big enough that I'm hoping I'm coming out ahead with lower air conditioning bills), and a roof angle exposure that is not solar-friendly even if they weren't there. So I was thinking, if I had space for just a few panels, perhaps I could go low-tech with a system built from a scrap UPS. After all, I've got an APRS station - PC, TNC, radio, and internet connection - using power constantly, and I often find perfectly good UPSs being tossed out (i.e. free) because the battery is shot and not worth replacing.
Put the solar cells in place of the UPS' battery, and modify the power failure detect circuitry to work backwards - give preference to the battery/solar side, only switching to the line side if there is insufficient "battery" power. This will give me free 120 vac whenever the sun shines. At night, it would power-fail back over to the line, and only then would the power company's meter start to spin. I'd probably put a regular UPS down stream from the hacked-up one, in case the failover/back from line to solar wasn't real clean.
That is almost exactly what a grid-connected system does.
In addition it also synchronizes (voltage and frequency) with the grid AND it doesn't disconnect from the grid. This allows for sharing the load between the panels and the grid. And for having the meter spin backwards when it puts your "overproduction" in the grid.
The more clever systems also search the MPP (Maximum Power Point) of the panels and optimize production of AC Power that way. If you run disconnected from the grid you will only produce what you use, overcapacity is wasted.
The biggest problem I see is that most of the solar panels available these days are in the 50-60 volt range, which means that you'd need to do a conversion down to battery voltage first. (Maybe put two panels in series and run them into a regular 12v DC power supply?)
A step down switching regulator can easily handle that at >95% efficiency. For instance the MAX5035 can handle voltages up to 75V.
Now, I just need to find a source of free-to-cheap solar panels. I almost bought a set at a local Ham swap ($10 ea) that had cracked surface glass but were otherwise functional, but I didn't think they'd survive the trip home in my car (no place big enough to lay them flat). (I'd need to weatherproof them too....)
Anyway, just a thought...
Greg KO6TH
BR, -- //\arc
... I have... a roof angle exposure that is not solar-friendly...
That was another error I had made in my situation.
Again, there is a BIG difference between solar design for stand-alone battery systems (must point south, optimum angle, etc) and grid-tie systems that can be anything from SE to SW and even FLAT and still be only a few percent off peak!.
The economics are entirely different.
The remote/battery system, MUST provide a minimum power on the worst winter days and weather of the year. It MUST be optimized for winter.
On the other hand, the grid tie system only has to have a good AVERAGE power averaged over a year. And you can make more money in a month of summer sun making money at HIGH payback rates than you can get all winter (3 months).
Even a FLAT array makes more power in the 3 summer months than the optimum tilt angle array does.
And lastly, anything pointed SE to S to SW is about the same for a grid-tie system. You lose at most about 5% SE or SW compared to South. Again, the reason is not obvious. But any tilted array is only going to see the sun for 180 degrees of path across the sky. Even the ideal South facing tilted array does not see the morning sun nor the evening sun in the summer when you are getting your most payback.. It only sees the midle 6 hours. Since the sun is up much longer than that most seasons, then getting those 6 hours averaged before noon (SE) or getting them in the afternoonn (SW) makes little difference for a grid-tie array, though, I'd favor SW, since peak electric rates apply longer in the afternoon than in the morning. So you want to maximize your power when electricity rates are highest.
Again, I am sharing this off topic with everyone, because I too learned that my thinking was all wrong based on my previous experiences with stand-alone power systems and that a grid-tie-system has completely diffeerent economics to my normal thinking...
You can play with all the angles and directions for grid-tie systems on-line with the solar energy calculator here:
Yes, SOUTH with a latitude tilt is best... But based on annual AVERAGEs: Southeast only lost 5% Southwest only lost 5% Droping the tilt to the angle of my roof 25 deg only lost 1%! Droping the tilt to FLAT on the ground only lost 14% (but if I tilt them up to 45deg Sept to April) I GAIN 20%! And that is a +5% over optimum south.
http://www.nrel.gov/rredc/pvwatts/version1.html
On the other hand, ANY shade will significantlly cut into your power budget.
Bob, Wb4APR
I think you are also forgot the price of a Building permit - in this county 1-2K
Doc
----- Original Message ----- From: "Robert Bruninga" bruninga@usna.edu To: "'Greg D.'" ko6th_greg@hotmail.com; ptrowe@yahoo.com; amsat-bb@amsat.org; wb3jfs@cox.net Sent: Friday, October 02, 2009 11:27 AM Subject: [amsat-bb] Re: Solar Power (I was wrong)
... I have... a roof angle exposure that is not solar-friendly...
That was another error I had made in my situation.
Again, there is a BIG difference between solar design for stand-alone battery systems (must point south, optimum angle, etc) and grid-tie systems that can be anything from SE to SW and even FLAT and still be only a few percent off peak!.
The economics are entirely different.
The remote/battery system, MUST provide a minimum power on the worst winter days and weather of the year. It MUST be optimized for winter.
On the other hand, the grid tie system only has to have a good AVERAGE power averaged over a year. And you can make more money in a month of summer sun making money at HIGH payback rates than you can get all winter (3 months).
Even a FLAT array makes more power in the 3 summer months than the optimum tilt angle array does.
And lastly, anything pointed SE to S to SW is about the same for a grid-tie system. You lose at most about 5% SE or SW compared to South. Again, the reason is not obvious. But any tilted array is only going to see the sun for 180 degrees of path across the sky. Even the ideal South facing tilted array does not see the morning sun nor the evening sun in the summer when you are getting your most payback.. It only sees the midle 6 hours. Since the sun is up much longer than that most seasons, then getting those 6 hours averaged before noon (SE) or getting them in the afternoonn (SW) makes little difference for a grid-tie array, though, I'd favor SW, since peak electric rates apply longer in the afternoon than in the morning. So you want to maximize your power when electricity rates are highest.
Again, I am sharing this off topic with everyone, because I too learned that my thinking was all wrong based on my previous experiences with stand-alone power systems and that a grid-tie-system has completely diffeerent economics to my normal thinking...
You can play with all the angles and directions for grid-tie systems on-line with the solar energy calculator here:
Yes, SOUTH with a latitude tilt is best... But based on annual AVERAGEs: Southeast only lost 5% Southwest only lost 5% Droping the tilt to the angle of my roof 25 deg only lost 1%! Droping the tilt to FLAT on the ground only lost 14% (but if I tilt them up to 45deg Sept to April) I GAIN 20%! And that is a +5% over optimum south.
http://www.nrel.gov/rredc/pvwatts/version1.html
On the other hand, ANY shade will significantlly cut into your power budget.
Bob, Wb4APR
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Bob, While I'm at my summer place in the Upper Peninsula of Michigan (EN56), I run my satellite station purely by solar power. It is not by any means a high tech setup, but it works for me. I bought my 15watt solar panel from a RV (recreational vehicle) center, and charge up two 26 amp hour gel cell batteries. I also use one of those " $10 Dayton specials" power units with a 17ah battery and 400 watt inverter. This runs the laptop and rotator. But not for long. I think I've got less than $250 into the whole system. This is not by any means the most effective or efficient system to have, but it is portable and works for Field Day. So if I make contact with you from EN56, it's done from solar power. 73 de Doug KA8QCU
----- Original Message ----- From: "Robert Bruninga" bruninga@usna.edu To: "'Greg D.'" ko6th_greg@hotmail.com; ptrowe@yahoo.com; amsat-bb@amsat.org; wb3jfs@cox.net Sent: Friday, October 02, 2009 14:27 Subject: [amsat-bb] Re: Solar Power (I was wrong)
... I have... a roof angle exposure that is not solar-friendly...
That was another error I had made in my situation.
Again, there is a BIG difference between solar design for stand-alone battery systems (must point south, optimum angle, etc) and grid-tie systems that can be anything from SE to SW and even FLAT and still be only a few percent off peak!.
The economics are entirely different.
The remote/battery system, MUST provide a minimum power on the worst winter days and weather of the year. It MUST be optimized for winter.
On the other hand, the grid tie system only has to have a good AVERAGE power averaged over a year. And you can make more money in a month of summer sun making money at HIGH payback rates than you can get all winter (3 months).
Even a FLAT array makes more power in the 3 summer months than the optimum tilt angle array does.
And lastly, anything pointed SE to S to SW is about the same for a grid-tie system. You lose at most about 5% SE or SW compared to South. Again, the reason is not obvious. But any tilted array is only going to see the sun for 180 degrees of path across the sky. Even the ideal South facing tilted array does not see the morning sun nor the evening sun in the summer when you are getting your most payback.. It only sees the midle 6 hours. Since the sun is up much longer than that most seasons, then getting those 6 hours averaged before noon (SE) or getting them in the afternoonn (SW) makes little difference for a grid-tie array, though, I'd favor SW, since peak electric rates apply longer in the afternoon than in the morning. So you want to maximize your power when electricity rates are highest.
Again, I am sharing this off topic with everyone, because I too learned that my thinking was all wrong based on my previous experiences with stand-alone power systems and that a grid-tie-system has completely diffeerent economics to my normal thinking...
You can play with all the angles and directions for grid-tie systems on-line with the solar energy calculator here:
Yes, SOUTH with a latitude tilt is best... But based on annual AVERAGEs: Southeast only lost 5% Southwest only lost 5% Droping the tilt to the angle of my roof 25 deg only lost 1%! Droping the tilt to FLAT on the ground only lost 14% (but if I tilt them up to 45deg Sept to April) I GAIN 20%! And that is a +5% over optimum south.
http://www.nrel.gov/rredc/pvwatts/version1.html
On the other hand, ANY shade will significantlly cut into your power budget.
Bob, Wb4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (5)
-
Dave Larsen PhD -
Doug Kuitula -
Greg D. -
Marc Vermeersch -
Robert Bruninga