Calculating Energy Production
I calculated monthly energy production values for the AC side of the system and used those values to calculate the annual revenue generated if this system was awarded a FIT contract. The formulas used were from Renewable and Efficient Electric Power Systems by Gilbert M. Masters. I also calculated energy production on the DC side of the system to provide Francois Laforest-Grant with information for his DC microgrid.
AC Energy Production
RETScreen Analysis
I performed a RETScreen analysis to determine the financial viability of this project. Using interest rates and debt ratios recommended by the lead engineers, I calculated a simply payback of 12.1 years. This project also has a positive net present value, and will generate over $20,000/year in revenue if awarded a FIT contract.
Calculating Bifacial Energy Gains
As my design utilises bifacial solar modules, I calculated the average annual amount of bifacial energy gains. Referring to research done in this field, I determined that my system was elevated at the recommended height (>0.5m), and had good underlying surface albedo (~0.5 year round). Some bifacial energy gains are lost due to the shallower tilt angle, but not enough to make choosing this type of module impractical.
Manually Calculating Optimal Tilt angle and Direct beam irradiation
Using formulas found in Renewable and Efficient Electric Power Systems by Gilbert M. Masters I calculated the optimal angle for the site along with the average direct beam irradiation. This was similar to mean daily global insolation data collected by Natural Resources Canada. Given that the NRCan data was based on multiple years' observation of weather data for this site, I chose to go with the NRCan data as it was a more accurate representation of the typical conditions found on-site.
LCOE vs LDC rates
I also calculated the point at which the cost per kWh (14.4 cents/kWh) of my system would become cheaper than local utility rates, based on historical and projected time of use and tiered rates from the Ontario Energy Board. Based on the average annual percent increase in electricity rates, my system will produce energy more cheaply than off-peak rates by 2025, and the lower tiered rate by 2026.
System Specs
I sized my system to offset approximately 20% of the annual energy demand of the new building, based on energy intensity goals set in the SOR. I used a standard derate factor or 0.75 and found insolation values for my system configuration. I calculated the area required, and found it to be slightly higher than that required in the SOR. However, since my design utilises a canopy system, the space underneath the panels is both habitable and open to additional uses such as a recreational space and/or green roofing.
System Size, Area, Building Energy Offset, Annual Energy Production
Calculating LCOE
Using equations found in Renewable and Efficient Electric Power Systems by Gilbert M. Masters, I calculated the system cost, capital recovery factor, annual payments, and thus LCOE for my system.
Calculating LCOE
Wiring and Single Line Diagram
I created a wiring and single line diagram in PVCad to show how the components were connected to each other. I wired up all the strings, fed those to combiner boxes, then ran the output to the inverters and finally the load panel for the building. PVCad is an excellent tool for PV systems design as it will also calculate the size, number, and type of balance of system (BOS) components required for your design. It creates an Excel spreadsheet listing such BOS details as: length and type of conductors, number and size of fuses, length and type of conduit using appropriate conduit fill.
Confirming Last Year's Work
I verified that the optimal tilt angles and insolation values stated by last year's team were correct. Due to aesthetic concerns my system utilises a shallower tilt angle, however it still receives enough insolation to have a cost competitive levelized cost of energy (LCOE).
System Configuration and Annual Energy Output
In this tech memo, I stated the major system specs of my design such as: total area, size in kW, annual energy offset, and physical configuration. I discuss how I sized my strings to be code compliant (OESC 64-202). I also calculated annual energy production for both the AC and DC sides of my system, including the bifacial energy gains. The values obtained from hand calculations were confirmed with those obtained from simulation programs such as RETScreen, PVSyst, PVWatts, and Solar Pathfinder Assistant.
Component Selection
In this tech memo, I stated the specific components I chose to use in my design, citing applicable sections in the SOR. I also include figures of the wiring diagram and single line diagram that I created in PVCad, along with the balance of system (BOS) components list generated in PVCad.
LCOE Sensitivity
The cost per watt used in my calculations was higher than NREL solar PV system cost benchmark prices to accommodate the higher prices of bifacial modules. Given that solar PV prices have been dropping rapidly for a number of years, and that this system is unlikely to be built for at least another few years, by the time of construction, the cost per watt is likely to be much lower than the value I used in my calculations, thus giving a lower levelized cost of energy, making this system more financially viable.