Solar

PVWatts and the “Golden Ratio” of Solar Performance

PVWatts is a great tool for solar performance estimation, or at the very least is free and good enough for unshaded rooftops in the United States. We’ll use PVWatts to generate the “Golden Ratio” of solar to perform solar energy estimates and budget calculations in your head.

Ultimately, we want to determine how much energy a 1W solar array will produce in a year?

 

1 DC kW ~= __________ kwh/yr

1 DC Watt ~= _________ kwh/yr

The next step is to input your site conditions. Change the array size to 1kW from the default value of 4kW. Change the array type to “roof mount”.  Leave everything else the same for the time being.

PVWatts has advanced parameters to help you fine tune your model. Default values in PVWatts are conservative. For now, we’ll use the default PVWatts numbers under the motto, “It’s better to under-promise and over-deliver.” But even a more accurate model, annual weather patterns can cause solar performance to vary by over 10%, per year.

So if you are conservative on your design, PVWatts is all the computing power you need for unshaded jobsites.  However, as the projects grow in size, project financing requirements may request a more accurate model which should only increase the energy performance estimate number computed by PVWatts default values.

The major downside of PVWatts is that it does not model shade. For quick shade analysis, we recommend Folsom Lab’s Helioscope which has a hassle-free trial account. But guess what? Both the commercial software and PVWatts pull from the same weather data, so for unshaded, residential jobsites, PVWatts is all the computing power you need.

The final screen is an annual output for PVWatts.  We’ll produce about 1,290 kwh per year! In addition, we get useful hourly site data which we discuss in further in class. But for now, let’s go back and model a south-west facing array at the same site location. Change the 180 azimuth orientation to 225 degrees.

Notice the performance difference between a south and south-west facing array really isn’t that much. There are some minor economic implications here, but let’s continue to explore our  performance by modeling a due east facing array.

 

We lose about 15% of our production when reorienting from a south to an east or west array orientation. In fact, if we spun the solar array around 180 degrees and to face it north, we lose about 30% of our production. There is more to this story when you factor in economics. Always keep in mind:

It’s not just about how much electricity you produce, it’s also how much that electricity is worth.

It’s worthwhile to evaluate all project surfaces for solar. In most cases, fitting a larger array on the roof makes better economic sense than a smaller array. Installing an entire pallet of solar modules is more cost-effective than installing a smaller array.

But for solar projects oriented between southeast, south, and southwest, the energy performance estimate doesn’t budget. When covering the entire roof (moving onto east, west, and north roof surfaces), your total roof estimate “per watt” won’t shrink by more than 15% (at 4:12 or 5:12 roof tilts).

This brings us back to the Golden Ratio of Solar for Philadelphia!

 

1 DC kW ~= 1290 kwh/yr

1 DC Watt ~= 1.3 kwh/yr

Community Solar

State Engineering Continuing Education Requirements

Our course qualifies for continuing education in 41 states. Check engineering professional development requirements here:

StateRequirementDue DateReportingSpecial Instructions
Alabama15 PDH / yearEnd of YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Alaska24 PDH / 2 yearsEnd of Year OddSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Arkansas15 PDH / yearEnd of YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Delaware24 PDH / 2 yearsJune 30th Odd YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.We can break out our program into 3 hours ethical, 3 hours business, and 12 hours technical on request.
Florida18 PDH / 2 yearsFeb 28th Odd YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Georgia30 PDH / 2 yearsEnd of Year EvenSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Idaho30 PDH / 2 yearsNo special instructionsSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Illinois30 PDH / 2 yearsNov 30 Odd PE Nov 30 Even StructuralSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Indiana30 PDH / 2 yearsJuly 31 even yearsSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.Be sure to chat with the instructor while taking the class, as distance learning only qualifies for up to 15 hours.
Iowa30 PDH / 2 yearsDecember 31 Even/OddSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Kansas30 PDH / 2 yearsApril 30 Even A-L Odd M-ZSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Kentucky30 PDH / 2 yearsJune 30 Even M-Z Odd A-LSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Louisiana30 PDH / 2 yearsMarch 31 and September 30 based on the year of licenseSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Maine30 PDH / 2 yearsEnd of Year OddSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Maryland24 PDH / 2 yearsCheck with licensing boardSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Minnesota24 PDH / 2 yearsJune 30 EvenSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Mississippi15 PDH / yearEnd of YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Missouri30 PDH / 2 yearsEnd of YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Montana30 PDH / 2 yearsJune 30 EvenSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Nebraska30 PDH / 2 yearsJan 1 A-K Even, Jan 1 L-Z OddSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Nevada30 PDH / 2 yearsCheck with licensing boardSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
New Hampshire30 PDH / 2 yearsEnd of Birthday Month based on license yearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
New Jersey24 PDH / 2 yearsNo special instructionsNot yet approved for engineering continuing education
New Mexico30 PDH / 2 yearsDecember 31 Even or Odd based on license number endingSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
New York36 PDH / 3 yearsEnd of Birthday Month based on license yearNot yet approved for engineering continuing education
North Carolina15 PDH / yearJune 30thNot yet approved for engineering continuing education
North Dakota30 PDH / 2 yearsEnd of YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Ohio15 PDH / yearEnd of YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Oklahoma30 PDH / 2 yearsEnd of Month LicenseSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Oregon30 PDH / 2 yearsDecember 31 Odd A-F Even G-ZSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Pennsylvania24 PDH / 2 yearsNo special instructionsSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
South Caronlina30 PDH / 2 yearsJune 30th EvenSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
South Dakota30 PDH / 2 yearsBased on licenseSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Tennessee24 PDH / 2 yearsBased on licenseSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Texas15 PDH / yearMarch 31, June 30, September 30 or December 31 based on licenseSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Utah24 PDH / 2 yearsDec 31 EvenSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Vermont20 PDH / yearNo special instructionsSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Virginia16 PDH / 2 yearsEnd of Year OddSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
West Virginia15 PDH / yearJune 30thSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
Wisconsin30 PDH / 2 yearsAugust 1 EvenSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.Please be sure to chat / interact with the instructor during class, otherwise the class may only count for 13 hours.
Wyoming30 CPC / 2 yearsEnd of YearSelf-reporting, but we provide a publicly-viewable receipt stored on the SolarCoin Block Chain.
CaliforniaNo CEU Requirement
ArizonaNo CEU Requirement
ColoradoNo CEU Requirement
ConnecticutNo CEU Requirement
HawaiiNo CEU Requirement
MassachusettsNo CEU Requirement
MichiganNo CEU Requirement
WashingtonNo CEU Requirement
Rhode IslandNo CEU Requirement

Community.Solar makes not guarantee regarding the accuracy or completeness of this data. Please verify all information with your State Board.