Grid-tied solar
- Thread starter dave1949
- Start date
farmeratheart
Platinum Member
I agree- "Wow!" Kind of makes me feel a lot less significant with my 20 panel 4kW system! If I were in your shoes, however, buying all that electricity each month I bet our system would be bigger. Please keep us posted as the project moves along. You won't believe the satisfaction that comes at the end of the project when you are making your own power!
Frank
sdkubota
Platinum Member
There are a multitude of articles although it appears many have been scrubbed for political correctness. Here is but one although most state degredation rates around .08%/yr:
http://photovoltaics.sandia.gov/docs/PDF/IEEE Quintana.pdf
http://www.waset.org/journals/waset/v58/v58-120.pdf
It is possible that modern manufacturing methods have helped diminish early failure rates of panels.
http://photovoltaics.sandia.gov/docs/PDF/IEEE Quintana.pdf
http://www.waset.org/journals/waset/v58/v58-120.pdf
It is possible that modern manufacturing methods have helped diminish early failure rates of panels.
Redneck in training
Elite Member
I talked to a researcher from Iowa State University working in alternative energy field few days ago. He said that the certified panels will drop to about 90% of the guaranteed capacity. The way they do it is that the tolerance is always positive. In other words if they rate the panels to 220 W most of them will generate 235-250W. I also asked about the AC efficiency. The current technology is about 77% at the connection to the outlet/grid.
My system is right around 96%....
Panel ratings are based on Standard Test Conditions. You should be looking at the Nominal Rating when building your system.
Redneck in training
Elite Member
We are just exploring a loan for solar system. Iowa gives zero percent loan for half of the project but it has to be paired with commercial loan for the other half. If the zero interest loan is less than 25K it gets approved quickly.
Here is my system proposal:
92 Hyundai 250W mono panels.
92 Enphase 215 inverters.
1 Energy Management Unit for monitoring via web.
Unirac ground racking system.
Got a quote for 52k shipping, all drawings included + added estimated 3K for incidentals such as cable, concrete etc.
Eligible for 30% federal tax write off and up to 3000 Iowa tax write off.
Unfortunately own installation work can't be added to the total cost of the system unless you own a business that can be billed for the work.
Expected yearly generation 31000 kWh.
Expected payback 11 years assuming constant cost of electric power.
I figured that the loan payment will be about same (expected rate is 5% for 25k therefore effective interest for 50K is 2.5%) what we pay for electric power now so it will not affect our budget any significant way.
Cost of power increased at rate 2.1%/year in past 20 years in Iowa so if the trend continues the power will be 23% more costly after 10 years and 51% after 20 years.
I will talk to an expert at the university to make sure my assumptions are correct before I commit to the project.
Here is my system proposal:
92 Hyundai 250W mono panels.
92 Enphase 215 inverters.
1 Energy Management Unit for monitoring via web.
Unirac ground racking system.
Got a quote for 52k shipping, all drawings included + added estimated 3K for incidentals such as cable, concrete etc.
Eligible for 30% federal tax write off and up to 3000 Iowa tax write off.
Unfortunately own installation work can't be added to the total cost of the system unless you own a business that can be billed for the work.
Expected yearly generation 31000 kWh.
Expected payback 11 years assuming constant cost of electric power.
I figured that the loan payment will be about same (expected rate is 5% for 25k therefore effective interest for 50K is 2.5%) what we pay for electric power now so it will not affect our budget any significant way.
Cost of power increased at rate 2.1%/year in past 20 years in Iowa so if the trend continues the power will be 23% more costly after 10 years and 51% after 20 years.
I will talk to an expert at the university to make sure my assumptions are correct before I commit to the project.
Redneck in training
Elite Member
My system is right around 96%....
Panel ratings are based on Standard Test Conditions. You should be looking at the Nominal Rating when building your system.
Tim.
The rated power is 250W, nominal power is 228W for the panels I intend to use. Assumed AC efficiency for calculation of power production with Enphase inverters is 80%. I think it is due to high temperatures in the summer. I let the experts to do the calculations of expected production.
Panel ratings are based on Standard Test Conditions. You should be looking at the Nominal Rating when building your system.
Tim.
The rated power is 250W, nominal power is 228W for the panels I intend to use. Assumed AC efficiency for calculation of power production with Enphase inverters is 80%. I think it is due to high temperatures in the summer. I let the experts to do the calculations of expected production.
Modern grid tie inverters are in the high 90% range for efficiency. You will find bigger losses in your electrical runs than in the inverters.
As for sizing the array, I initially had 48 x 235W ( 11280W ) panels split between two 5KW inverters. In the heat of the summer they were peaking at ~9KW. So I put up another 8 panels this spring. Now on the hottest days, it is pushing the inverters into a slight surplus, which is dumped as heat. So you can do a quick calculation to see how much the panels are degraded by heat.
Your highest potential for output is in March/April, and Sept/Oct, when the temp is cool and the irradiance is still high. It is important for me to maximize my output though, because I am selling to the grid but am limited to 10K peak output by the terms of the contract.
As for sizing the array, I initially had 48 x 235W ( 11280W ) panels split between two 5KW inverters. In the heat of the summer they were peaking at ~9KW. So I put up another 8 panels this spring. Now on the hottest days, it is pushing the inverters into a slight surplus, which is dumped as heat. So you can do a quick calculation to see how much the panels are degraded by heat.
Your highest potential for output is in March/April, and Sept/Oct, when the temp is cool and the irradiance is still high. It is important for me to maximize my output though, because I am selling to the grid but am limited to 10K peak output by the terms of the contract.
I just learned of another thing to consider about residential energy systems of all types. A fellow in a neighboring town told me the town is putting a value (25%-30% of the installed cost) on his small wind turbine and including that in his property tax evaluation. He says solar PV systems are being valued at their full cost. He is a bit peeved to say the least.
I know real property and personal property tax laws vary considerably around the country, but have any of you run into this issue? I am afraid to ask our local tax clerk
Not really, she is a very nice and helpful person, but I will put it off until I have more info.
For example, if a person installs an outdoor wood boiler, or a geothermal system, are the cost of those included in tax evaluations in your areas?
I know real property and personal property tax laws vary considerably around the country, but have any of you run into this issue? I am afraid to ask our local tax clerk
Not really, she is a very nice and helpful person, but I will put it off until I have more info.For example, if a person installs an outdoor wood boiler, or a geothermal system, are the cost of those included in tax evaluations in your areas?
EE_Bota
Elite Member
I just learned of another thing to consider about residential energy systems of all types. A fellow in a neighboring town told me the town is putting a value (25%-30% of the installed cost) on his small wind turbine and including that in his property tax evaluation. He says solar PV systems are being valued at their full cost. He is a bit peeved to say the least.
I know real property and personal property tax laws vary considerably around the country, but have any of you run into this issue? I am afraid to ask our local tax clerk
For example, if a person installs an outdoor wood boiler, or a geothermal system, are the cost of those included in tax evaluations in your areas?
I don't know, but I almost do Dave. My county is on the lookout for any improvement or change whatsoever. My heat pump that was taxed for many years goes belly up, they want to know of the replacement so they can tax it at full value. Generally, anything that gets inspected also gets taxes, and the inspection can be thought of as a way to get the change on the tax roles as much as for any other reason. Same for carpet, or most anything, but they feel too silly to call in the carpet inspectors, so we are on our honor. Unless a county chooses to favor certain real property (thinking it is a good thing and wishing to encourage more) they are all mostly pretty hungry for tax revenue.