## 1 Introduction
### System Configuration Features and Preliminary Modeling Results
Additionally, this allowed minimization of the system output voltage to safe levels, and the selection of a suitable low-power microinverter model with matched electric input characteristics and having maximum power point tracking (MPPT) capabilities. The benefits of using the parallel and also the massively-parallel electric circuit configurations of PV modules installed into low-power solar energy harvesters have been well documented and reported previously [35]. Predictive modelling of the electric energy outputs expected to be generated by the atrium installation and each of its parts annually (and also monthly) has been performed using HOMER Pro  
Figure 2: A graphical summary of the microgrid configuration details (**a,b**), sample data logs for the daily energy generation and use (**c**), and a photo of TV screen data showing a summary of system state (**d**), which is also available through live Internet broadcast at [[http://tcp.iostream.io/vicinity-warwickgrove/index.php](http://tcp.iostream.io/vicinity-warwickgrove/index.php)]([http://tcp.iostream.io/vicinity-warwickgrove/index.php](http://tcp.iostream.io/vicinity-warwickgrove/index.php)) with 15-minute data sampling intervals. microgrid analysis software package (HOMER Energy Inc., Boulder, CO, USA). The unconventional PV generators (solar windows) have been approximated in the software-assisted microgrid model as \"generic flat plate PV\" outputting 30 W per window at peak irradiation conditions, at the nominal operating cell temperature (NOCT). This power rating per window closely approximates their expected performance at the peak orientation and peak-weather conditions, when the temperature of solar cell surfaces is near 40 \({}^{\circ}\)C. The model has also fully accounted for the local monthly and yearly climate-related solar irradiation datasets corresponding to the exact geographic location of installation. The geometric orientation (tilt) and also the azimuth orientation angles of all system parts were fully accounted for in the software model. Figure 3 shows a graphical summary of the energy generation modeling results, obtained for each PV windows subsystem and for the overall atrium installation. The modeling results indicated that the annual energy output in excess of 0.6 MWh can be expected, composed mainly of the roof sections contribution over the warmer months, and dominated by the contributions from the North Wall section between April and August. The atrium's measured monthly energy production during August 2019 (from the data logged by the Enphase Enlighten(tm monitoring system) was 38.54 kWh, which was about 10% less than the corresponding monthly output predicted by the software model, not accounting for the small extra contributions from the strongly  
Figure 3: A summary of the predicted monthly and yearly microgrid energy output results modeled using HOMER Pro software package; the measured electric energy generation amounts during the month of August 2019 are also shown (data obtained from the Enphase Enlighten(tm monitoring software records). shaded East Wall window units (which were nevertheless modeled as two 30W east-facing generators placed vertically). The measured monthly electric energy output from the North Wall units in August was 16.8 kWh (or 43.6% of the total generated energy), which also corresponded closely to the model predicting about 50% energy contribution from these units. The north-oriented front entrance windows have frequently been subjected to the intermittent shading conditions from the people traffic, reducing the power generation. Considering the local annual sun-path geometry, strong contributions from the vertically-mounted North Wall windows were also expected during the colder months, when the mid-day Sun altitude angles are low, and with the Sun azimuth direction shifting towards north, even at sunrise times.