Renewable Energy Engineering StudioNEC 690/705/706 · IEEE 1547 · Solar PV · BESS · Microgrids · EV Charging

Applied Renewable Energy Engineering Professional Program

Why a 20%-efficient solar panel can still be a great investment — efficiency and capacity factor measure completely different things and don't track each other.

Why one shaded panel can tank your whole array under a string inverter, but barely register with microinverters or power optimizers — it comes down to shared series current.

Where the extra energy-conversion step actually happens — DC-coupled means fewer conversions and matched equipment, AC-coupled means an extra round-trip but retrofit flexibility.

Why a home full of working solar panels can go completely dark in an outage — a basic grid-tied system is required to shut down (anti-islanding), and only a hybrid or off-grid system can safely keep the lights on.

Two different reasons solar production gets capped — clipping is an internal, deliberate DC-oversizing tradeoff, curtailment is an external grid or interconnection limit unrelated to how the system was sized.

Why a "10kW solar system" can mean two different numbers — the sum of the panels' rated output, or the inverter's rated maximum output — and why utilities and incentive programs often care about only one of them.

SOC and DOD describe the exact same battery level from opposite directions — but routinely cycling to a deep DOD degrades lithium-ion capacity faster than shallow cycling, which is why manufacturers cap recommended DOD.

Why identical solar systems can have different economics — net metering credits exports near the retail rate, net billing credits them at a separately set, typically lower rate, which is exactly why storage and self-consumption matter more under one than the other.

Why a "400W panel" never actually produces 400W in the real world — STC is an idealized lab rating, PTC simulates realistic field heating, and PTC comes out 10-15% lower every time, which is exactly why California's CEC-approved list uses PTC, not STC.

Why a single, defect-free silicon crystal converts more sunlight than a cast block of many crystals — grain boundaries scatter charge carriers, which is the entire reason mono cells run ~20-22% efficient vs. poly's ~15-17%.

Why a fixed panel loses energy every morning and evening to cosine losses, and how single- and dual-axis trackers claw it back — at the cost of added mechanical complexity, wind-load design, and upkeep.

Why the battery with the lower sticker price per kWh often costs more per kWh actually delivered — lead-acid's ~50% safe DoD and few hundred cycles vs. lithium-ion's ~90-100% DoD and thousands of cycles.

Maximum circuit current × 1.25 × 1.25 per NEC 690.8(A)(1). Wire ampacity and OCPD rating.

String open-circuit voltage temperature correction at lowest expected ambient temperature.

Usable kWh from rated kWh given charge/discharge efficiency. Cycle life and annual throughput.

Simple payback, NPV, and IRR from installed cost, annual savings, incentives, and degradation rate.

120% busbar rule: inverter output current limit from panel main breaker and bus rating.

Total EV demand from charger count, kW rating, and diversity factor per NEC 625.42.

Federal ITC (30%), MACRS 5-year depreciation, and state incentive summary for project economics.

Annual kWh from Weibull k/c parameters and turbine power curve integration.

DoD limits, cycle life at operating DoD, and calendar aging estimate for LFP and NMC chemistries.

Estimate recommended system size (kW DC), panel count, annual production, and roof area from annual usage, peak sun hours, and system derate factor.

Recommended nameplate battery capacity (kWh) and power/inverter rating (kW) for backup power or solar self-consumption, accounting for depth of discharge and round-trip efficiency.

Required inverter AC capacity and string-inverter count from array DC size and target DC/AC ratio, with an estimated annual clipping-loss impact.

Average load, load factor, and annual demand-charge exposure from a facility's annual kWh and peak kW — the two figures that anchor solar-plus-storage sizing.

Battery storage financial return calculator — annual throughput, degradation-adjusted payback period, and lifetime net savings for peak-shaving, demand-response, or arbitrage BESS projects.

Adjust array kW, tilt, location irradiance, and day length to plot the hourly DC/AC production curve and daily kWh. Models a clear-sky bell curve with inverter and system losses per NREL PVWatts methodology.

Simulate charge/discharge of a BESS against a daily load + solar profile under time-of-use rates. Watch state of charge over the day and quantify peak-shaving and TOU arbitrage savings.

Balance generation (PV + battery + genset) against critical load during a grid outage to see whether the island holds and for how long, with hourly energy balance and survival time.

Simulate N EVs charging with arrival diversity and managed charging to build the aggregate site load profile and find the coincident peak demand and realized diversity factor.

Split-screen interactive designer for a complete residential solar + storage + EV system. Explore a 3D model — rooftop PV array, optimizers/rapid shutdown, hybrid inverter, DC/AC disconnects, battery (BESS), energy gateway, backup panel, net meter, and EV charger — alongside a connected one-line diagram. Click any component or node to cross-highlight across both views, and toggle to a top-down Site Plan with wiring runs. Covers NEC 690 PV design, 705 interconnection (120% rule), 706 storage, and 625 EV charging.

Planned: will simulate a behind-the-meter battery storage system responding to a 24-hour commercial load profile — charging from solar, discharging during evening peak, and receiving demand response signals — letting you adjust tariff structures (TOU, demand charge, export credit) and battery control strategy (self-consumption, peak shaving, backup priority) to optimize economics, and displaying state of charge, grid import/export, and real-time savings.

Planned: an interactive portfolio dashboard for a renewable energy project collection — rooftop solar, BESS, EV charging, and wind — that will track cumulative production (kWh), CO₂ avoided, cost savings, and remaining payback by asset, display NEC 690 system parameters, interconnection status, and utility meter data, and let you toggle between daily, monthly, and lifetime views with export to CSV for utility reporting.

Planned: will let you design a complete rooftop or ground-mount solar PV system using NREL PVWatts methodology, from roof area, tilt, azimuth, system losses, and utility rate to array size, annual kWh production, system cost, and simple payback — performing NEC 690 string sizing, inverter matching, wire sizing, and OCPD selection, and outputting a system one-line diagram and production summary for interconnection applications.

Planned: will let you size a battery energy storage system for peak shaving, backup power, or self-consumption from load profile (kW demand), utility demand charge rate, backup duration requirement, and battery chemistry (Li-ion, LFP, flow battery) — calculating required energy (kWh), power rating (kW), inverter size, and round-trip efficiency losses, and validating against NEC 706 and IFC 1207 installation requirements.

Planned: will let you plan EV charging infrastructure for a parking facility or fleet depot from stall count, charger levels (L1/L2/DCFC), simultaneous use rate, and utility transformer size — calculating peak electrical demand, load management strategy, NEC 625 branch circuit sizing, panel loading, and transformer capacity, and identifying whether a utility service upgrade is required and estimating demand charges with managed charging.

Planned: will let you design an islanded or grid-tied microgrid combining solar PV, battery storage, diesel gen-set, and critical loads by defining load tiers (life safety, critical, non-critical), switching strategy (soft transfer, UPS-class), and islanding detection method per IEEE 1547 — outputting a single-line diagram with protection coordination, transfer switching logic, and daily energy balance for a typical day.

Planned: will let you estimate annual energy production from a small wind turbine (HAWT or VAWT) using the Weibull wind speed distribution and turbine power curve, from hub height, mean wind speed, turbine rated power, and rotor diameter — calculating capacity factor, annual kWh, wake losses, and estimated revenue or savings, and checking setback and noise requirements against typical zoning standards.

Interactive 13-section renewable energy reference covering solar PV design (NEC 690), BESS energy storage (NFPA 855), wind energy, grid integration (IEEE 1547), microgrids, EV charging infrastructure, IRA tax incentives, and project development. First 3 free to preview.

A commercial solar-plus-storage system carried from load profile through PV sizing, inverter selection, battery sizing, interconnection, financial analysis, and a finished code review.