Multi-Season Energy Generation
As shown in Table 3, we tracked the monthly energy generation data
and IEC 61724-1:2021 standardized metrics across all four study periods.
Production clearly shifted with the seasons: August 2025 (south-west monsoon
retreat) records the lowest monthly output at 10,478 kWh, recovering to 12,096
kWh in October and stabilizing at 12,061 kWh in November 2025. Despite lower
absolute generation in August, the observed PR (0.805) was higher than in
November (0.751). This suggests that reduced irradiance during the monsoon
lowers cell temperatures, thereby improving conversion efficiency and elevating
the PR. Note that we ran all our statistical checks at the 95% confidence level
using standard correlation methods.
Table 3. Multi-Season Energy Generation
and IEC 61724-1:2021 Performance Metrics — KCAEFT 100 kW System
|
Month / Season
|
Monthly Generation (kWh)
|
Daily Avg (kWh/day)
|
Final Yield Yf
(kWh/kWp/day)
|
Ref. Yield Yr (h/day)
|
Obs. PR (Yf/Yr)
|
|
August 2025 (SW Monsoon retreat)
|
10,478
|
337.7
|
3.38
|
4.20
|
0.805
|
|
October 2025 (NE Monsoon
active/retreat)
|
12,096
|
390.2
|
3.90
|
5.05
|
0.772
|
|
November 2025 (Post-monsoon / winter
onset)
|
12,061
|
402.0
|
4.02
|
5.35
|
0.751
|
|
November 2024 (Primary observation
period)
|
~11,800 (est.)
|
~393
|
~3.93
|
5.20
|
~0.756
|
Reference
Yield (Yr) estimated from PVGIS for Tavanur (10.79°N, 76.00°E), Erbs
decomposition model. GSTC = 1,000 W/m², P₀ = 100 kW. ~ denotes
estimated values. November 2024 from a 28-day primary observation.
These findings are consistent with Indian rooftop PV studies under
similar tropical climatic conditions, where thermal losses dominate during
clear-sky periods (Baghel and Chander, 2022). Ajub Ajulian et al. (2025)
also found that post-monsoon clear-sky periods in the tropics produced more
total power but were actually less efficient at converting sunlight per unit
irradiance. The KCAEFT data faithfully reproduce this seasonal pattern.
However, these findings are early trends rather than definitive facts, because
we only tracked the system for a short time.
Statistical Correlations
Table 4 presents Pearson and Spearman correlation coefficients
between all measured environmental variables and daily E-Today (kWh) for the
November 2024 observation period (n = 28 days). All values are statistically
significant at p < 0.01 (two-tailed, 95% CI). It is important to note that
correlations indicate statistical association rather than direct causation.
Table 4. Bivariate Correlations —
Environmental Variables vs. Daily E-Today (November 2024, n = 28 days)
|
Environmental Variable
|
Pearson r
|
Spearman ρ
|
Physical Association
|
|
Light Intensity (Lux → W/m²)
|
+0.92
|
+0.91
|
Dominant driver of short-circuit
current
|
|
Ambient Temperature ( °C)
|
+0.78
|
+0.76
|
Positive to 32 °C; thermal
saturation beyond
|
|
Relative Humidity (%RH)
|
−0.61
|
−0.63
|
Cloud proxy; soiling adhesion
accelerator
|
|
Wind Speed (m/s)
|
+0.34
|
+0.31
|
Convective cooling benefit
|
|
Composite Index: Lux×(1−RH/100)
|
+0.94
|
+0.93
|
Synergistic coupling of irradiance
and humidity
|
All
correlations are statistically significant at p < 0.01 (two-tailed). The
composite index is empirical; it was proposed for practical, predictive use.
Correlations indicate association, not causation.
Light intensity (converted to W/m²) shows the strongest association
with daily generation (r = 0.92), confirming its role as the primary driver of
short-circuit current and instantaneous power output (Bamisile et al.,
2025). Ambient temperature shows a threshold-bounded positive association (r =
0.78): warmer days tend to accompany clearer skies, but beyond approximately 32
°C, this benefit is eroded by thermal efficiency losses. Relative humidity
shows a moderate inverse association (r = −0.61), acting both as a proxy for
cloud cover and as an accelerator of soiling adhesion through capillary
cementation of fine particles on moist module glass (Ghosh, 2020). The
composite index [Lux × (1 − RH/100)] achieves the highest single-variable
association (r = 0.94), demonstrating multiplicative coupling between
irradiance and humidity in their joint influence on generation.
Temperature-Stratified Production Analysis
Table 5 stratifies observed daily energy generation and estimated
Performance Ratio by ambient temperature band during the November 2024
observation period.
Table 5. Temperature-Stratified Daily
Production Profile — KCAEFT (November 2024)
|
Temp. Band ( °C)
|
Avg E-Today (kWh)
|
Est. PR
|
System Behavior and L_T
Estimate
|
|
22–26
|
~340
|
~0.72
|
Low irradiance / cloud hours; L_T ≈
3–5%; monsoon transition
|
|
27–30
|
~390
|
~0.77
|
Productive window; moderate thermal
load; L_T ≈ 7–9%
|
|
31–32
|
~410
|
~0.78
|
Optimal band; peak production; L_T ≈
10–12%
|
|
> 32
|
~385
|
~0.72
|
Thermal saturation: L_T ≈ 13–16%; PR
decline despite high irradiance
|
PR
estimated via IEC 61724-1:2021; PVGIS reference irradiation for Tavanur. LT
estimated from NOCT model (Equation 3), GPOA (W/m²) range 600–900
W/m², ΔT_roof = +4 °C.
The 31–32 °C band yields the highest E-Today (~410 kWh/day) and
estimated PR (~0.78), representing the operational sweet spot at KCAEFT. Beyond
32 °C, the estimated cell temperature reaches 55–59 °C (NOCT model with +4 °C
roof correction), producing LT ≈ 13–15% and
a measurable PR decline to approximately 0.72. This band-by-band analysis
directly informs the priority for thermal management remedies discussed in
Section 5.
PRCLM Loss Quantification Results
Table 6 presents the component-level loss quantification from the
PRCLM across all four study periods. As illustrated in Fig. 3, thermal loss
constitutes the largest share of total losses during post-monsoon periods. Fig.
4 shows strong agreement between modeled and observed performance ratios across
all seasons.
Table 6. PRCLM Component Loss
Quantification and Model Validation — KCAEFT 100 kW System
|
Loss Component
|
Aug 2025 (%)
|
Oct 2025 (%)
|
Nov 2025 (%)
|
Nov 2024 (%)
|
Physical Explanation
|
|
Thermal loss (LT)
|
7.0
|
8.5
|
10.0
|
9.0
|
Tcell
44–57 °C (NOCT model); clear sky elevates module temperature
|
|
Cloud/Irradiance
loss (LI)
|
6.0
|
5.5
|
6.0
|
7.0
|
Overcast days:
G_POA 150–300 W/m²; monsoon diffuse dominance
|
|
Soiling/Cementation
(LS)
|
3.0
|
5.0
|
6.0
|
5.5
|
Monsoon rain
self-cleans (Aug); post-harvest dust peaks in Nov
|
|
Orientation loss
(LO)
|
1.0
|
1.5
|
2.0
|
2.0
|
Right Grid
morning azimuthal deficit; 12–20 min peak lag
|
|
System/Inverter
loss (Lsys)
|
4.0
|
4.0
|
4.0
|
4.0
|
ηinv ≈ 0.96;
wiring losses ≈ 0.98–0.99 (fixed estimate)
|
|
Total Modelled
Loss (1−PRmodel)
|
19.4
|
22.6
|
24.9
|
24.8
|
Cascade
multiplication (Equation 2)
|
|
Observed PR (PRobs
= Yf/Yr)
|
0.805
|
0.772
|
0.751
|
~0.756
|
IEC 61724-1:2021
|
|
Modelled PR (PRmodel)
|
0.806
|
0.774
|
0.748
|
0.752
|
PRCLM cascade
model output (this study)
|
|
|PRobs
− PRmodel|
|
0.001
|
0.002
|
0.003
|
0.004
|
Model validation
— RMSE = 0.003 across all periods
|
LT
from NOCT model (Eq. 3–4), ΔT_roof = +4 °C, γPmax = −0.0045/ °C (Skoplaki &
Palyvos, 2009). LI
from PVGIS clear-sky baseline. LS: ρs = 0.15%/day
(Nov), 0.05%/day (Aug); dnc ≈ 30–35 days LO: solar geometry,
Tavanur 10.79°N, 09:00–11:00 IST. Lsys = 1 − (0.96 × 0.99).
Individual L uncertainty: ±1–2%; ~ = estimated.
Thermal loss (LT) is the largest single controllable loss
component during post-monsoon and winter months (10% in November), driven by
high irradiance, elevated ambient temperatures, and the metal roof's thermal
contribution. It is markedly lower in August (7%) because monsoon cloud cover
moderates cell temperatures while suppressing irradiance—explaining why
August's PR (0.805) is higher than November's (0.751) despite lower absolute
monthly output. These findings are consistent with Indian rooftop PV studies
under similar tropical climatic conditions, where thermal losses dominate
during clear-sky periods (Baghel and Chander, 2022). Sensitivity analysis
indicates that thermal and soiling losses are the dominant contributors to
variations in system PR.
Soiling loss (LS) is
the fastest-evolving component within any given season. In August, monsoon
rainfall self-cleans modules, maintaining LS at
approximately 3.0%. By November, without any recorded cleaning event, L_S rises
to 6.0%—doubling the soiling burden. At ρs ≈ 0.15%/day, each uncleaned week
costs the 100 kW system approximately 30–40 kWh of recoverable yield. The
overall uncertainty in PR_model is estimated at ±2–3%, accounting for the
propagation of measurement errors, irradiance estimation uncertainty, and model
assumptions. The model's RMSE of 0.003 demonstrates strong agreement, though
future studies should incorporate higher temporal resolution datasets for more
rigorous validation.

Fig. 3. Component-level loss contribution (%) to total
PRCLM-modeled losses across four seasonal study periods at KCAEFT, = = thermal
loss;= irradiance (cloud-induced) loss;= soiling loss;= orientation loss;
= system loss, including inverter and wiring inefficiencies. Data from Table 6.

Fig. 4. PRCLM model validation: observed Performance
Ratio (PR_obs) versus modelled Performance Ratio (PR_model) for all four study
periods. The 1:1 reference line represents perfect agreement; RMSE = 0.003
confirms model accuracy.
Evidence-Based
Interventions by Loss Component
The PRCLM results directly map each identified loss to its physical
cause, enabling targeted, prioritized remedies rather than generic maintenance
prescriptions. Seven evidence-based interventions are prescribed (Table 7),
ranked by a combination of the magnitude of loss addressed and implementation
simplicity. All yield gain estimates are drawn from the cited literature and
should be interpreted within site-specific conditions.
Soiling and Cementation
Bi-annual panel cleaning and hydrophobic nano-coating together
address the LS pathway, identified as the fastest-growing
post-monsoon loss mechanism. The recommended schedule is May (before the
south-west monsoon onset) and December (after the north-east monsoon retreat).
Hydrophobic nano-coatings, applied every 2–3 years, sustain a 30–50% reduction
in soiling adhesion and leverage monsoon rainfall for partial self-cleaning
(Ghosh, 2020; Wu et al., 2025). It is noted that the soiling rate
estimates are based on indirect environmental correlations, and direct optical
transmittance measurements are recommended in future work to validate these
values.
Thermal Loss — Roof-Specific Interventions
Addressing LT (9–10% in November) requires interventions
accounting for the metal corrugated roof context. A minimum rear ventilation
gap of 15 cm between the roof surface and the module underside allows natural
convective airflow to dissipate heat. Where existing racking constrains this
gap, repositioning the lower clamp row can increase clearance without replacing
the full racking. Aluminium heat-sink fins on the rear of module frames provide
supplementary passive cooling at modest cost. Both interventions target the
ΔT_roof component (Equation 3), estimated to add 3–5 °C to the effective cell
temperature, which, through γPmax, compounds to produce an additional 1.4–2.3%
loss (Wu et al., 2025).
Orientation Correction and Monitoring
The Right Grid's morning peak lag (LO ≈ 2% in November)
is the simplest and least costly loss to eliminate: a minor tilt recalibration
in a single maintenance visit can synchronize Right Grid output with the Left
Grid during the 09:00–11:00 IST window. IoT per-string monitoring, partially enabled
by the existing datalogger, should be configured to flag morning current
asymmetries between Left and Right Grid strings as an ongoing diagnostic.
Table 7. Evidence-Based Remedy Matrix —
KCAEFT 100 kW Rooftop PV Installation
|
Remedy
|
Est. Yield Gain (%)
|
Payback Period
|
Targeted Loss / Basis
|
|
Bi-annual panel cleaning (May +
December)
|
3–8%
|
< 1 year
|
L_S; zero capital, campus labour;
Ghosh (2020)
|
|
Hydrophobic nano-coating
|
5–15%
|
2–4 years
|
L_S; 30–50% adhesion reduction; Wu et
al. (2025)
|
|
Rear ventilation gap (≥15 cm)
|
2–4%
|
< 1 year
|
L_T; convective cooling; Bamisile et
al. (2025)
|
|
Passive cooling fins (Al,
rear-mount)
|
2–4%
|
3–5 years
|
L_T; zero operational expenditure;
Wu et al. (2025)
|
|
Right Grid tilt recalibration
|
2–5%
|
< 1 year
|
L_O; azimuth correction; Baghel
& Chander (2022)
|
|
IoT per-string fault monitoring
|
3–6%
|
2–3 years
|
L_sys; early fault detection;
ANERT-eligible
|
|
Lux-based soiling monitoring
|
—
|
Minimal
|
Validates cleaning schedule; tracks
ρs
|
Yield
gain estimates are indicative, based on cited literature. Payback periods at
the 2024 KSEB tariff; ANERT co-funding may reduce effective CAPEX.
Limitations and Future
Work
This study presents a component-level quantification of solar PV
losses under humid tropical conditions; however, several limitations must be
acknowledged. First, the use of lux-based irradiance estimation does not
capture the full solar spectrum, particularly the near-infrared, and introduces
some systematic error relative to pyranometer-based measurements. Nevertheless,
its application is justified in resource-constrained monitoring scenarios and
is indirectly validated by the strong agreement between modeled and observed
performance ratios.
Second, the model validation is based on a limited number of
seasonal data points (n = 4), which may not fully capture high-resolution
temporal variability. Future studies should incorporate continuous,
high-frequency datasets to enable more robust validation. Third, soiling losses
were estimated indirectly using environmental correlations rather than direct
transmittance or cleaning experiments, which may affect precision. Similarly,
the roof temperature correction factor (ΔT_roof = +3–5 °C) was adopted from
literature and was not measured directly at the study site.
Fourth, the PRCLM assumes independence among loss components,
whereas in practice, environmental variables such as temperature and irradiance
interact constantly. Monthly aggregation was used for validation due to data
availability constraints, resulting in a slight timing mismatch.
Future work should include full annual monitoring, direct optical
soiling measurements, infrared thermography for hotspot detection, sensitivity
analysis using Monte Carlo methods, and validation across multiple
humid-tropical PV installations. Evaluation of agrivoltaic crop integration
beneath elevated racking structures is also recommended as a complementary
strategy for ANERT-supported agricultural campus installations.