sodamo
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solar power
- Thread starter kenacp
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houstonscott
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If you can connect to grid and sell back, don't go batteries and don't use tracking. Your better off spending that money on more panels and selling during good hours and buying power at night.
HS
HS
grsthegreat
Super Star Member
well I'm all for solar and wind energy IF i could install it in a cost efficient way.
So far, Ive never been able to crunch the numbers and find a cost savings for anyone that lives next to utility power lines. they have only worked for the rural guy living a few miles from power where the utility company wants HIM to foot the entire bill.
For me, i would NEVER save enuf money to pay for the system. Never.
Now, if they would come up with a better system and get the price into a reasonable ballpark, thats different. A few years ago, there was a company here in Idaho that was looking for electrical contractors to install the new revolutionary roof mount wind turbine that produced line voltage power (110/220v) to supplement your house power costs. the unit was the size of an oil drum. had nice pics and nice brochure. I signed up for more info....never heard anything back. Not sure what happened to them, or if was just some sort of hoax. I thought...finally an affordable wind system.
my elect bills vary from $50 - $120 per month depending on how lazy I'm at in stocking the wood fireplace, or running the a/c. Now if i could rely on a solar system to pump the power to me and pay for itself over a few years, id do it. but these systems constantly need new batteries, inverter problems,maintenance, etc. so its not just a one time cost.
That being said, if a direct a/c input system comes around that i can use to augment my current system, id jump at it ... unless it costs $50,000 which it probably will. My ultimate wish list system would provide for power with both sun and wind (snows here in idaho), and provide line voltage.... also would need cheap battery storage and inverters....like that will ever happen
So far, Ive never been able to crunch the numbers and find a cost savings for anyone that lives next to utility power lines. they have only worked for the rural guy living a few miles from power where the utility company wants HIM to foot the entire bill.
For me, i would NEVER save enuf money to pay for the system. Never.
Now, if they would come up with a better system and get the price into a reasonable ballpark, thats different. A few years ago, there was a company here in Idaho that was looking for electrical contractors to install the new revolutionary roof mount wind turbine that produced line voltage power (110/220v) to supplement your house power costs. the unit was the size of an oil drum. had nice pics and nice brochure. I signed up for more info....never heard anything back. Not sure what happened to them, or if was just some sort of hoax. I thought...finally an affordable wind system.
my elect bills vary from $50 - $120 per month depending on how lazy I'm at in stocking the wood fireplace, or running the a/c. Now if i could rely on a solar system to pump the power to me and pay for itself over a few years, id do it. but these systems constantly need new batteries, inverter problems,maintenance, etc. so its not just a one time cost.
That being said, if a direct a/c input system comes around that i can use to augment my current system, id jump at it ... unless it costs $50,000 which it probably will. My ultimate wish list system would provide for power with both sun and wind (snows here in idaho), and provide line voltage.... also would need cheap battery storage and inverters....like that will ever happen
catfishdaddyengineering
Silver Member
GRS,
The problem with line power for wind is that an AC generator requires lots of torque (wind) to excite the field before it starts generating power. Just think of inrush current on a motor. Most require at least 15mph winds to start generating. The system in your 4th paragraph was probably a VAWT (Vertical Axis Wind Turbine). They look kind of like a squirrel cage fan, do not have to track the wind, and start generating in as little as 5mph wind. These are awesome, and you can build them yourself for less than $500.
Right now there is no line power system for solar, because the way the cells work is virtually the same as a battery. Not to get too technical, but the sun excites the top layer and electrons flow through the substrate to the bottom. The top and bottom are connected just like a battery with anode and cathode; therefore, it makes a loop. This makes it DC. Our body's energy works the same way.
If you plan to grid-tie, it is also better to have DC-to-AC inverter, because the inverter does all the work of regulating voltage. It can synchronize to the grid much faster and easier. In other words, cheaper than a synchronizer system for AC generator.
The problem with line power for wind is that an AC generator requires lots of torque (wind) to excite the field before it starts generating power. Just think of inrush current on a motor. Most require at least 15mph winds to start generating. The system in your 4th paragraph was probably a VAWT (Vertical Axis Wind Turbine). They look kind of like a squirrel cage fan, do not have to track the wind, and start generating in as little as 5mph wind. These are awesome, and you can build them yourself for less than $500.
Right now there is no line power system for solar, because the way the cells work is virtually the same as a battery. Not to get too technical, but the sun excites the top layer and electrons flow through the substrate to the bottom. The top and bottom are connected just like a battery with anode and cathode; therefore, it makes a loop. This makes it DC. Our body's energy works the same way.
If you plan to grid-tie, it is also better to have DC-to-AC inverter, because the inverter does all the work of regulating voltage. It can synchronize to the grid much faster and easier. In other words, cheaper than a synchronizer system for AC generator.
grsthegreat
Super Star Member
cool, thanks for the input.:laughing: :thumbsup:
im going to look up some info on the VAWT systems, cause they really intrigued me at the time
IXLR8
Elite Member
VAWT systems are very intriguing, but usually not worth the paper the brochures they are printed on. They don't need much wind to start them generating power, but to get any real amount of power out of them, you need a good wind. You don't get good wind close to the ground, I would hate to see one spinning at the top of a 60 ft tower. Advancements are being made all the time but from all the research I did 2 years ago, VAWT systems have a long way to go. Having said that.. I hope they can find a way to make it work.
Solar PV, the new grid tied systems are affordable, especially if the gov't is willing to pay for 30% of the installation. Without the batteries, their cost of purchase/maintenance, the system I looked at produced the power I need for .07/Kwh, less then half of what I am paying now. It will take 8-10 years to payback, but the panels are rated for a 30 year life cycle and I figure if the inverters last the 5 years they are warranted for, they should last as long as the panels. So that is 20 years of free power. If I ever get my garage finished... this is what I am going to do.
dynasim
Platinum Member
Sodamo
Thanks! That was exactly what I was looking for. It will help in number crunching.
Chris
Thanks! That was exactly what I was looking for. It will help in number crunching.
Chris
eepete
Platinum Member
So with 7.7 KW DC rating, on a cloudy day I might get as low as 10 KWH. Mixed day, 20, and full sun 50 KWH. Grid tie. If you charge batteries, you won't get the power out that you put in, don't have an exact loss percentage, would guestimate 25% loss? Hope the battery crowd can chime in here too, I'd love to know what the total system efficiency is.
I've been on line about 6 months, made about 7 MHW for a daily average of about 38 KHW/day (with 7.7 panel capacity). That translates to about:
5 KWH per 1 KW panel capacity per day.
Realize that some days have been as low as 600 watts per 1 KW panel capacity per day. The weather was very cloudy with rain.
People with off grid can chime in, but I'll bet anyone who is off grid has a generator as part of their system.
Pete
dmccarty
Super Star Member
This thread made me do more pondering regarding PV. :laughing: Apparently I was pondering last Aug/Sept because I bought that issue of Home Power magazine. 
That issue just happened to have quite a few reports on solar projects that might work for us.
So if you can find that issue online, at the library or buy it, that would be a good resource.
Any who, the story about grid tied systems mentions an installed cost of $7-9 per watt.
They were using a total SYSTEM efficiency of 66%. There is a side bar conversation regarding how the calculated the 66% number.
Later,
Dan
That issue just happened to have quite a few reports on solar projects that might work for us.So if you can find that issue online, at the library or buy it, that would be a good resource.
Any who, the story about grid tied systems mentions an installed cost of $7-9 per watt.
They were using a total SYSTEM efficiency of 66%. There is a side bar conversation regarding how the calculated the 66% number.
Later,
Dan
eepete
Platinum Member
Dan's post got me thinking about the phrase "total system efficiency".
Like any energy system, you have to "follow the juice". On a tractor, you start with the maximum theoretical energy in a gallon of Diesel. Then you have the efficiency of the engine, then the transmission, then tractor, and finally you get energy "on the ground". All such measurements need units, such as HP or Watts.
For solar, you start with the energy of the sun on some amount of area. The panels then convert that to electricity, and that's already a pretty bad number along the lines of 10 to 15 percent. You now have DC. Then there is a box (single inverter) or boxes (micro inverters) that converts the panel's DC output to either AC that can go on the grid or DC that can charge batteries.
If you have batteries, there is the efficiency of charging, the efficiency of getting current out of the batteries, and then the DC to AC efficiency on the "back end" inverter.
Like any good technical thingie, you can go nuts with the details. I like to start out with the DC power output of the panels. Mine are rated 7.7KW, but when they are new you get a bit more (I've seen 8.5KW of _output_ from the panels around this time of year when the sun is 90 degrees on the panels and it's a low humidity day). The published DC power rating for a panel is set up for an "after 10 years of use" number driven by the 10 year warranty on the panels. The panels get a little less efficient each year, but they will have 25+ years of life. Between OC detail Geeks and paranoid Lawyers, is it any wonder this is too complex :laughing:. At any rate, the DC output of the panels is my starting point.
My inverter has a maximum efficiency of 96%, and I've seen it very close to this. Typical is around 94%. The output power is then off to the grid. You get better efficiencies at higher power outputs. Not unlike a tractor which is often most efficient when used to it's maximum ability.
So at a max output of 8 KW at 96% efficient, I loose 320 watts. But at a lower output of 2KW, my efficiency is worse at 93% but I only loose 140 watts. Note that efficiency very much changes with different manufactures and inverter architectures. My Fronius 10KW inverter has 3 parallel stages, so at low power only one is running, which helps with the efficiency. Efficiency also changes with temperature. In the winter time, I see the near 96% efficiency. At the peak of summer, that will go down a few percent because it's hot. Nothing is simple....
So for a battery system, I'd want to see the DC power out of the panels, and then add up the efficiency of the "DC to Battery charger" (easy to measure/know), the efficiency of "energy charged and stored in the batteries" (this seems like a hard one to figure out) and then the efficiency of the DC to AC inverter (this is also easy to measure).
The grid tie system will be cheaper and more efficient, but is worthless when it's dark. The battery "off grid" system will be more expensive and less efficient, but you have power whenever you want it (as long as the batteries have a charge in them).
Clear as mud?
Pete
Like any energy system, you have to "follow the juice". On a tractor, you start with the maximum theoretical energy in a gallon of Diesel. Then you have the efficiency of the engine, then the transmission, then tractor, and finally you get energy "on the ground". All such measurements need units, such as HP or Watts.
For solar, you start with the energy of the sun on some amount of area. The panels then convert that to electricity, and that's already a pretty bad number along the lines of 10 to 15 percent. You now have DC. Then there is a box (single inverter) or boxes (micro inverters) that converts the panel's DC output to either AC that can go on the grid or DC that can charge batteries.
If you have batteries, there is the efficiency of charging, the efficiency of getting current out of the batteries, and then the DC to AC efficiency on the "back end" inverter.
Like any good technical thingie, you can go nuts with the details. I like to start out with the DC power output of the panels. Mine are rated 7.7KW, but when they are new you get a bit more (I've seen 8.5KW of _output_ from the panels around this time of year when the sun is 90 degrees on the panels and it's a low humidity day). The published DC power rating for a panel is set up for an "after 10 years of use" number driven by the 10 year warranty on the panels. The panels get a little less efficient each year, but they will have 25+ years of life. Between OC detail Geeks and paranoid Lawyers, is it any wonder this is too complex :laughing:. At any rate, the DC output of the panels is my starting point.
My inverter has a maximum efficiency of 96%, and I've seen it very close to this. Typical is around 94%. The output power is then off to the grid. You get better efficiencies at higher power outputs. Not unlike a tractor which is often most efficient when used to it's maximum ability.
So at a max output of 8 KW at 96% efficient, I loose 320 watts. But at a lower output of 2KW, my efficiency is worse at 93% but I only loose 140 watts. Note that efficiency very much changes with different manufactures and inverter architectures. My Fronius 10KW inverter has 3 parallel stages, so at low power only one is running, which helps with the efficiency. Efficiency also changes with temperature. In the winter time, I see the near 96% efficiency. At the peak of summer, that will go down a few percent because it's hot. Nothing is simple....
So for a battery system, I'd want to see the DC power out of the panels, and then add up the efficiency of the "DC to Battery charger" (easy to measure/know), the efficiency of "energy charged and stored in the batteries" (this seems like a hard one to figure out) and then the efficiency of the DC to AC inverter (this is also easy to measure).
The grid tie system will be cheaper and more efficient, but is worthless when it's dark. The battery "off grid" system will be more expensive and less efficient, but you have power whenever you want it (as long as the batteries have a charge in them).
Clear as mud?
Pete
boggen
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next year or 2 away. i will be doing a complete off grid setup for turning a 20x24 cabin into a live able home.
i will be looking at low wind speed, windmill generators.
a bank or 2 of batteries.
generator that will most likely be converted to LP gas. if not a bigger generator bought that runs on diesel. (though LP, will most likely be it)
and most likely some solar panels will be tossed into the mix.
well pump, A/C, lights, fans, tv, computer, microwave.
heating will be either wood, or a vent less wall LP gas heater.
water heater will be gas
at moment the cabin runs fairly good on i want to say a honda generator 3000watt unit. a full tank of gas last a little longer than a day.
but when batteries, wind mill generator, solar panels all get tossed into mix, a more expensive transfer switch will be put into place. to allow auto start of generator.
the problem with transfer switch, and battery charger, gets more complicated, when dealing with 4 different power sources (wind mill, solar panels, batteries, and generator)
it will be a very complex setup, with efficiency losses, but *shrugs* you do what ya gotta do. beyond winning the lottery. i am not to overly worried about efficiency loss. if i only loose 10% i would be happy and not complain as long as it all worked and i had enough power to do what needs to be done.
i will be looking at low wind speed, windmill generators.
a bank or 2 of batteries.
generator that will most likely be converted to LP gas. if not a bigger generator bought that runs on diesel. (though LP, will most likely be it)
and most likely some solar panels will be tossed into the mix.
well pump, A/C, lights, fans, tv, computer, microwave.
heating will be either wood, or a vent less wall LP gas heater.
water heater will be gas
at moment the cabin runs fairly good on i want to say a honda generator 3000watt unit. a full tank of gas last a little longer than a day.
but when batteries, wind mill generator, solar panels all get tossed into mix, a more expensive transfer switch will be put into place. to allow auto start of generator.
the problem with transfer switch, and battery charger, gets more complicated, when dealing with 4 different power sources (wind mill, solar panels, batteries, and generator)
it will be a very complex setup, with efficiency losses, but *shrugs* you do what ya gotta do. beyond winning the lottery. i am not to overly worried about efficiency loss. if i only loose 10% i would be happy and not complain as long as it all worked and i had enough power to do what needs to be done.
Loren49
Veteran Member
We've lived with a small standalone solar & wind system since 1983. (generator backup)
If connection to the grid is easy, the only reason to go with a standalone system would be a philosophical desire. It is much more economical to finance a grid connect system. Batteries are the weakest link with a relatively short life span and with a grid connect you do not waste your excess power.
After saying that, there is an argument the other way. A standalone system will likely encourage the user to use less electricity and to be more efficient. (I'm not saying that this means a less comfortable life in any way)
------------------
One other point about output units. Panels and wind units are rated in watts (or kilowatts, megawatts) (the commercial unit 1200ft from my house is rated at 1.5MW, 1.5 million watts) People mistakenly state daily usage in watts while the correct unit is watt/hours. Example- a daily usage that averages a 10 amp draw of 120 volts equals an average 1200 watt usage 24 hrs a day. (amps x volts = watts) To find kWh (kilowatt hours) multiply 1200w x 24 hrs = 28,800 watt hours or 28.8kWh.
The same amperage with a 12 volt source would equal 2.8 kWh or one tenth the energy.
Loren
If connection to the grid is easy, the only reason to go with a standalone system would be a philosophical desire. It is much more economical to finance a grid connect system. Batteries are the weakest link with a relatively short life span and with a grid connect you do not waste your excess power.
After saying that, there is an argument the other way. A standalone system will likely encourage the user to use less electricity and to be more efficient. (I'm not saying that this means a less comfortable life in any way)
------------------
One other point about output units. Panels and wind units are rated in watts (or kilowatts, megawatts) (the commercial unit 1200ft from my house is rated at 1.5MW, 1.5 million watts) People mistakenly state daily usage in watts while the correct unit is watt/hours. Example- a daily usage that averages a 10 amp draw of 120 volts equals an average 1200 watt usage 24 hrs a day. (amps x volts = watts) To find kWh (kilowatt hours) multiply 1200w x 24 hrs = 28,800 watt hours or 28.8kWh.
The same amperage with a 12 volt source would equal 2.8 kWh or one tenth the energy.
Loren
tommu56
Elite Member
Loren
What you are describing is about the same as my cabin. that is off grid.
If you are going most of the transfer will be done with you inverter.
It will be seamless start gen the inverter will switch load from battery's to the gen and switch if power is available to charge batteries.
Home power magazine is a great source of info.
Home Power Magazine: Solar | Wind | Water | Design | Build
Backwoods solar has alot of info in their catqalog
Backwoods Solar Electric Systems
the wind mill is something that i thought about but I didn't feel comfortable having it run for weeks or months at a time and not being able to shut it down. because we don't have winter access (this year the last we got up there was the week after thanksgiving.)
tom
forgeblast
Elite Member
What about the newer dual inverters, that let you have a grid tie and or battery bank on the same system. if the batterys are full it feeds into the grid, grid goes down it powers your house.
