The effect of low insolation conditions and inverter oversizing on the long‐term performance of a grid‐connected photovoltaic system

Abstract

The performance of a roof mounted grid-connected photovoltaic (PV) system in Northern Ireland was monitored over 3 years on annual, seasonal and monthly bases. The overall system performance was adversely affected by low insolation conditions; 19% of total incident insolation was absorbed at irradiance level below 200 W/m 2 and 67% below 600 W/m 2 , only 6Á2% above 900 W/m 2 . In summer and winter, the PV and system efficiencies were 9Á0 and 8Á5%, and 7Á8 and 7Á5%, respectively and inverter efficiencies were 86Á8 and 85Á8%, respectively. The inverter for this particular system was oversized; 77% of the total DC energy produced when inverter's operating load was 50% of its rated capacity. The annual average monthly system performance ratio (PR) was 0Á61 with seasonal variation 0Á59 to 0Á63. The average monthly PV, system and inverter efficiencies over the whole monitored period were 8Á8, 7Á6 and 86Á8%, respectively. The main losses of the system were inverter DC/AC conversion loss, inverter threshold loss and low insolation loss.

Performance assessment of a thin film photovoltaic system under actual Mediterranean climate conditions in the island of Crete

“…On the other hand, it was clear from the results, that the models proposed by RissereFuentes [41] and Mondol et al [18] predicted significantly higher than the observed values of Tm, when the related adjustment indicators MBE, MAE and RMSE for RissereFuentes [41] model were 32.0%, 32.0% and 32.7%, respectively. This fact may be a result of the linear regression coefficients in their Table 9 Summary of Ross e Smockler [57], Ross [43] e Nordmann and Clavadetscher [51], Tselepis e Tripanagnostopoulos [58], Mondol et al [18] and Schott [59] models evaluation test results under real field conditions.…”

“…Chenni et al [55] Tm ¼ 4:3 þ 0:028*G T þ 0:943*Ta À 1:528*Vw Servant [56] Tm ¼ Ta þ 0:0138*G T *ð1 þ 0:031*TaÞ*ð1 À 0:042*VwÞ King [34] Tm ¼ Ta þ GT GT;REF ½0:0712*Vw 2 À 2:411*Vw þ 32:96 Independent variables: Ta, G T Mondol et al [18] Tm ¼ Ta þ 0:031*G T À 0:058 Ross [43]-Nordmann and Clavadetscher [51] Tm ¼ Ta þ k*G T , with k ¼ 0.0208 Ross-Smockler [57] Tm ¼ Ta þ NOCTÀ20 800 *G T…”

“…According to Ayompe et al [47] k was determined equal to 0.018 C*m 2 /W using nonlinear regression analysis on measured data from Dublin (Ireland). Mondol et al [18] developed a correlation equation to predict Tm, using measured module temperature, Ta and incident insolation data collected in the summer of year 2002 at Ballymena (N. Ireland). They determined k ¼ 0.031 C*m 2 /W, via linear regression technique.…”

Measured performance of a 1.72kW rooftop grid connected photovoltaic system in Ireland

“…The monthly PV module efficiency (g PV,m ) is calculated as [7]: The instantaneous PV system efficiency is calculated as [11]:…”

“…The monthly system efficiency (g sys,m ) is calculated as [7]: Reduction of output current for irradiance sun spectra with an 397 air mass lower than AM 1.5.…”