Page 411 - A Comprehensive Guide to Solar Energy Systems

420 A COmpREHENSIvE GUIDE TO SOLAR ENERGy SySTEmS

There is a growing body of work on the CEDs and EpBTs of various system types across
varying geological boundaries. In a recent metaassessment Koppelaar [37] harmonized
several studies for annual solar radiation, supply chain technologies, lifecycle boundaries,
and technological configurations of mono­Si and poly­Si systems. Koppelaar identified
quality variation and study shortcomings and examined the ability to reproduce existing
results. The following parameters were used for harmonization: EROI was calculated for
studies that only derived EpBT; energy input values missing from the solar module pro­
duction chain were complimented with mean values; studies lacking energy input val­
ues for BOS, installation, transportation, operation, maintenance, and decommissioning
were complimented with mean values; energy input values for batteries, auxiliary ser­
vices, power lines operation, restructuring, labor, and capital investment cost based on
energy intensities were removed from studies; electricity output was recalculated using a
−1
−2
1700 kW h m yr (where yr refers to annum) radiation value; performance ratio of 0.8%
−1
with a degradation rate of 0.7% yr were applied; solar module packing factors to adjust
for noncell module area were assumed at 0.94 for poly­Si and 0.8 for mono­Si modules;
and a plant lifetime of 25 years. The results of the harmonization on EROIs are illustrated
in Fig. 21.6 in terms of % Energy Output related to EROI.
In general, the harmonization resulted in slightly lower EpBTs and higher EROI values
than the original studies. For mono­Si a mean EpBT of 3.9 years and a mean EROI of 8.6:1
was determined on recalculation. For poly­Si a mean EpBT of 2.9 years and a mean EROI
of 9.3 was found on recalculation. The largest recalculations were primarily due to lack of

FIGURE 21.6 % Energy Output versus EROI for harmonized studies of mono-Si and poly-Si. Adapted from Koppelaar
RHEM. Solar-PV energy payback and net energy: meta-assessment of study quality, reproducibility, and results
harmonization. Renew Sustain Energy Rev 2017;72:1241–55.