# HOW TO CALCULATE SOLAR PLANT PERFORMANCE RATIO (PR) | SOLAR PV DESIGN

Hi Guys, welcome to Minutes 2 Energy. We are a team of Solar professionals with
more than 10 years of experience in technology and business fields and today we are going
to share our knowledge and experience with you. Please see the video till the end for useful
resources. So, let's start!! Today’s topic is Solar Plant Performance
Ratio or in short PR. PR is a very important tool or factor that
being used globally by companies and professionals to assess the healthiness of Solar PV system.

So let’s know how this PR is calculated
and how it is so important for Solar PV System. So what is Performance ratio or the PR for
Solar PV Power Systems? PR is the Ratio of Effective Produced Energy
to Ideal Energy Yield at STC Condition. As it’s a Ratio it is Unit less and globally
it is being denoted as a Percentage value. Here the term Effective Energy is the available
Useable Energy delivered to the Grid or to the End User. While calculating the PR all the losses like
Optical losses PV array Losses DC to AC conversion losses and the other System losses are taken
info on Different types of system losses.

Simple Annual PR measured on the basis of
Actual Annual useable energy and the Annual Solar Irradiance
Now let’s see the Formula of PR. So PR is equals to E Grid divided by the product
of GII and P Nom PV. Here E Grid is the Useable energy available
at the User End. Unit of E grid is kilo Watt hours per year. GII refers to the Global Inclined Irradiation
received by the Solar PV array at certain tilt angle. Next is P nom PV. This is Solar PV array’s installed DC capacity
and denotes as kilo Watt Peak.

Next is the types of PR which are there for
their own significance and applicability. So let’s know more about them. First is STC Equivalent PR. It is determined by adjusting the power at
each recording interval to compensate for difference between the actual PV module temperature
and the STC reference temperature. This method normally used when the System
PR is to be measured at a short duration of day time. Annual Temperature corrected PR is similar
to the previous one. Here PR is calculated by adjusting the reporting
period with respect to power to compensate for the difference between the actual PV module
Temperature and the expected annual average module temperature.

Annual Temperature correction is significant
when the Annual PR is required to be Validated for within 15 to 20 days of operation. Now let’s look at an example of how to calculate
simple annual PR with available plant operational data. For any given year and location say from a
one thousand kilo watt peak Solar PV On-Grid installation the annual Global Irradiance
received at the PV plane is 1875 kilo Watt hours per meter square per year and the useable
energy fed to grid is 1540 Mega Watt Hours. Now here the E grid is 1540 megawatt hours
or 1540 into 1000 kilo watt hours per year. GII is 1875 kilo Watt hours per meter square
per year and the P nom PV is one thousand kilo watt peak. Then the yearly PR Should be calculated as
1540000 divided by open bracket 1875 multiplied by 1000 close bracket. Which is 0.82 or 82%. So hope you now understand how to calculate
Annual Performance ratio of solar Plant. Please see our other video on How to Calculate
PR in MS Excel for more detailed understanding. The Solar Plant Performance Ratio is defined
in the norm IEC EN 61724.

61724-1 (2017 edition). Link to get the standard from IEC webstore
is in the description below. Now let’s talk about Few Points you should
keep in mind while assessing the Solar Plant Performance Ratio. First PR always represented as Percentage. Second PR is a Ratio of actual energy generated
to the ideal energy Yield for a given period. And the third one is that it is independent
of location’s specific Irradiance level. So What is the Significance of Plant Performance
Ratio? Well The PR is an important metric in the
PV industry it is often used as a contractual condition / contract warranty when commissioning
a PV system Irrespective Of System Size Or System Type whether be it ground-mount or
rooftop based Grid-connected or Off-grid be it a small rooftop system or even an Ultra
Megawatt utility scale solar plant.

Also we professionals always check PR for
the HEALTHINESS of the plant and to VERIFY the annual energy yield. So this is all about Solar Plant Performance