Estimation of weighted average efficiency of grid connected solar PV inverters for Indian climatic conditions
Student name: Mr Hariharan Krishnamurthy
Guide: Dr B Prasad
Year of completion: 2014
Host Organisation: Water and Renewable Energy IC, Larsen and Toubro Construction, Chennai
Supervisor (Host Organisation): Mr Milan Kumar
Abstract: The overall efficiency of solar PV systems depends not only on the efficiency of the solar PV
modules in use, but also on the efficiency of the other BOS components. The inverter, often
referred to as the backbone of a solar PV system, converts the DC power produced by the PV
modules to AC power. This conversion efficiency is of cardinal importance in determining the
overall efficiency and estimating the annual energy yield of grid connected solar PV power
plants in the preliminary analysis undertaken by project developers and system designers.
The peak efficiency specified by inverter manufacturers is measured under nominal input
parameters as per the inverter’s design. However, solar PV inverters seldom operate under
such nominal conditions due to varying solar radiation over a period of time. This results in a
deviation of the actual operating efficiency of inverters from the peak efficiency, leading to
inaccurate estimations of overall efficiency and annual energy yield of solar PV systems.
The Euro efficiency and CEC efficiency are two weighted average efficiency formulae that
were developed for Trier, Germany and Sacramento, California respectively based on hourly
averages of solar radiation data for these locations. Although the aforementioned weighted
average efficiency formulae are specific to Trier and Sacramento, they are being used at present
as a benchmark worldwide by inverter manufacturers and project developers alike to quantify
the efficiency of inverters.
Since irradiation varies from one location to another, the weighted average efficiency will
have to be formulated taking the local irradiation profile into consideration. This study presents
an approach for the formulation of the weighted average efficiency of solar PV inverters for
locations in India, namely Chennai, Tamil Nadu; Jaisalmer, Rajasthan; Gurgaon, Haryana and
Charanka, Gujarat. The major DC input power levels of the inverters have been determined
based on the irradiation pattern in these locations and the respective weighted average inverter
efficiency formulae are formulated accordingly. The suitability of the Euro efficiency and CEC
efficiency for these locations has also been studied and the inaccuracies, if any, have been
quantified.
Keywords: Solar PV Inverters, Efficiency, Weighted average efficiency, Euro efficiency,
CEC efficiency
