REP Renewable Energy Professional (AEE REP) Overview
These study notes are designed to prepare candidates for the Association of Energy Engineers (AEE) Renewable Energy Professional (REP) certification exam. The notes cover six core subjects: renewable energy resource assessment and technology, project economics and financing, grid integration and energy storage, regulatory frameworks and environmental impact, site assessment and system design, and operations, maintenance, and performance monitoring. Each subject includes key concepts, must-know items, practical applications, distinctions, pitfalls, and review tasks. Candidates should supplement these notes with official AEE references and current industry standards.
For Technical Conquer practice planning, this module is tracked as 100 questions over about 180 minutes with a listed pass mark of 70%. Treat those numbers as practice baselines and verify the current official format before scheduling.
How This Guide Is Organized
The sections below turn the syllabus into studyable subject blocks. Read a subject first, explain the must-know ideas without notes, then use questions, flashcards, and mind maps to test whether the knowledge holds under field-style pressure.
- Renewable Energy Resource Assessment and Technology
- Renewable Energy Project Economics and Financing
- Grid Integration and Energy Storage
- Regulatory Frameworks and Environmental Impact
- Site Assessment and System Design
- Operations, Maintenance, and Performance Monitoring
Exam Snapshot and Readiness Target
Format: 100 questions, 180 minutes, pass mark 70% (practice baseline; verify with AEE)
Candidate level: Professional with experience in renewable energy, energy engineering, or related fields
Readiness target: Demonstrate comprehensive knowledge of renewable energy technologies, project development, economics, grid integration, regulations, and performance monitoring
Most candidates should budget at least 42+ focused study hours, then adjust upward for unfamiliar equipment, code, regulatory, commissioning, controls, or calculation-heavy content.
Renewable Energy Resource Assessment and Technology
Syllabus Focus
- Solar resource assessment (irradiance, insolation, PV and CSP technologies)
- Wind resource assessment (wind speed, direction, power curves, turbine types)
- Biomass, geothermal, hydro, and ocean energy technologies
- Resource measurement and modeling techniques
Key Notes
- Solar irradiance is measured in W/m²; insolation (kWh/m²/day) varies by location, season, and tilt. Use TMY (Typical Meteorological Year) data for long-term estimates.
- Wind power density (W/m²) depends on air density and wind speed cubed. Classify sites using IEC wind classes (I, II, III) based on reference wind speed and turbulence.
- Biomass energy content is measured by higher heating value (HHV) and lower heating value (LHV). Moisture content significantly reduces net energy output.
- Geothermal resources are categorized by temperature: low (<90°C), medium (90-150°C), high (>150°C). Binary cycle plants are used for medium-temperature resources.
- Hydropower potential depends on head (height difference) and flow rate (m³/s). Small hydro (<10 MW) often uses run-of-river designs with minimal storage.
Must Know
- Understand the difference between direct normal irradiance (DNI) and global horizontal irradiance (GHI) for solar applications.
- Know the power curve of a wind turbine: cut-in, rated, and cut-out wind speeds; capacity factor calculation.
- Recognize the typical efficiency ranges: PV (15-22%), wind (30-45%), hydro (70-90%), geothermal (10-20% for binary, higher for flash).
- Be able to interpret resource maps and data from sources like NREL, NASA SSE, or local meteorological stations.
Field and Exam Application
- Use solar pathfinder or Solmetric SunEye for shading analysis at potential PV installation sites.
- Apply wind rose diagrams to determine prevailing wind direction for turbine siting.
- Calculate biomass feedstock availability from agricultural or forestry residues using yield per acre and collection efficiency.
High-Yield Distinctions
- GHI vs. DNI: GHI is total solar radiation on a horizontal surface; DNI is direct radiation from the sun, important for concentrating solar power (CSP).
- Capacity factor vs. availability factor: capacity factor is actual output over rated output over time; availability factor is time available to generate.
- IEC wind classes: Class I (high wind, high turbulence), Class II (medium), Class III (low wind). Turbines are designed for specific classes.
Common Pitfalls
- Confusing irradiance (instantaneous power) with insolation (energy over time).
- Assuming wind speed at hub height is the same as at anemometer height without applying wind shear correction (power law or log law).
- Neglecting soiling losses in solar PV estimates (typically 2-5% annually).
Review Tasks
- Practice converting between units: kWh/m²/day to W/m², mph to m/s.
- Review NREL's PVWatts and SAM (System Advisor Model) for solar and wind resource assessment.
- Calculate capacity factor for a given wind turbine using a power curve and Weibull distribution.
Renewable Energy Project Economics and Financing
Syllabus Focus
- Levelized cost of energy (LCOE) calculation and components
- Net present value (NPV), internal rate of return (IRR), payback period
- Tax incentives (ITC, PTC, MACRS depreciation), grants, and rebates
- Financing structures: debt, equity, power purchase agreements (PPAs), and tax equity
Key Notes
- LCOE = (Total lifecycle cost) / (Total lifetime energy production). Includes capital, O&M, fuel, and financing costs. Discount rate significantly affects LCOE.
- NPV > 0 indicates a profitable project; IRR should exceed the cost of capital. Payback period is simple or discounted.
- In the US, the Investment Tax Credit (ITC) allows 30% of eligible costs for solar and storage (as of 2024, subject to phase-down). The Production Tax Credit (PTC) applies to wind and other technologies.
- MACRS (Modified Accelerated Cost Recovery System) allows 5-year depreciation for solar and wind (bonus depreciation available).
- PPAs are long-term contracts (15-25 years) where a developer sells electricity at a fixed or escalating price to a buyer.
Must Know
- Calculate LCOE with given capital cost, O&M, fuel cost, capacity factor, and discount rate.
- Understand the impact of tax credits and depreciation on project NPV.
- Know the difference between feed-in tariffs (FITs), net metering, and PPAs.
- Recognize common financial metrics: debt service coverage ratio (DSCR), leverage ratio, and return on equity (ROE).
Field and Exam Application
- Evaluate a solar PV project using NPV analysis with ITC and MACRS benefits.
- Compare LCOE of wind vs. solar for a specific site using realistic capacity factors.
- Structure a PPA with an escalating price to hedge against inflation.
High-Yield Distinctions
- Simple payback vs. discounted payback: discounted payback accounts for time value of money.
- ITC vs. PTC: ITC is a one-time credit based on capital cost; PTC is per kWh produced over 10 years.
- Debt vs. equity: debt has fixed interest and priority in repayment; equity has higher risk and potential returns.
Common Pitfalls
- Using nominal discount rate with real cash flows (inflation mismatch).
- Ignoring degradation in energy production over time (e.g., PV degrades ~0.5%/year).
- Forgetting to include decommissioning costs in LCOE for certain technologies (e.g., nuclear, large hydro).
Review Tasks
- Build a simple LCOE spreadsheet model with inputs for capital, O&M, fuel, capacity factor, and discount rate.
- Research current ITC and PTC rates and eligibility requirements from the IRS or DSIRE database.
- Calculate NPV for a 10 MW solar farm with 30% ITC, 5-year MACRS, and a 20-year PPA at $0.05/kWh.
Grid Integration and Energy Storage
Syllabus Focus
- Grid interconnection requirements (IEEE 1547, UL 1741)
- Power quality, voltage regulation, and frequency response
- Energy storage technologies: lithium-ion, flow batteries, pumped hydro, compressed air
- Demand response, microgrids, and virtual power plants
Key Notes
- IEEE 1547 standard governs interconnection of distributed energy resources (DER) to the grid, including voltage and frequency ride-through, anti-islanding, and power quality.
- Energy storage systems (ESS) provide grid services: frequency regulation, peak shaving, load shifting, and renewable firming.
- Lithium-ion batteries dominate due to high energy density and falling costs; flow batteries offer longer duration (4-12 hours) and longer cycle life.
- Pumped hydro storage accounts for ~95% of global grid storage capacity; requires two reservoirs at different elevations.
- Microgrids can operate grid-connected or islanded; require proper protection coordination and energy management systems.
Must Know
- Understand the four quadrants of reactive power capability for inverters (IEEE 1547-2018).
- Know the difference between energy capacity (kWh) and power capacity (kW) for storage.
- Recognize the role of battery management systems (BMS) in safety and performance.
- Be familiar with net metering policies and their impact on grid integration.
Field and Exam Application
- Design a battery storage system for peak shaving at a commercial facility: size based on peak demand reduction target.
- Evaluate the impact of high PV penetration on voltage regulation in a distribution feeder.
- Implement a demand response strategy using smart inverters and load control.
High-Yield Distinctions
- Grid-following vs. grid-forming inverters: grid-following synchronize to grid voltage; grid-forming can establish voltage and frequency in islanded mode.
- Round-trip efficiency of storage: lithium-ion ~85-95%, flow batteries ~70-80%, pumped hydro ~70-85%.
- C-rate: 1C discharges battery in 1 hour; 0.5C in 2 hours. Higher C-rate reduces usable capacity.
Common Pitfalls
- Confusing power (kW) and energy (kWh) when sizing storage for a specific application.
- Assuming all inverters have the same reactive power capability; check IEEE 1547 settings.
- Neglecting thermal management in battery systems; temperature extremes reduce life and safety.
Review Tasks
- Review IEEE 1547-2018 standard sections on voltage regulation and frequency ride-through.
- Calculate the required battery capacity (kWh) to shift 500 kWh of solar generation from midday to evening peak.
- Compare levelized cost of storage (LCOS) for lithium-ion vs. flow batteries for a 4-hour duration application.
Regulatory Frameworks and Environmental Impact
Syllabus Focus
- Federal and state renewable portfolio standards (RPS) and clean energy standards
- Environmental impact assessments (EIA) for renewable projects
- Permitting processes: local, state, federal (NEPA, Clean Water Act, Endangered Species Act)
- Carbon markets, renewable energy certificates (RECs), and carbon offsets
Key Notes
- RPS require utilities to source a percentage of electricity from renewables; vary by state with different targets and timelines.
- NEPA (National Environmental Policy Act) requires environmental impact statements (EIS) for federal actions; many renewable projects on federal land trigger NEPA.
- RECs represent the environmental attributes of 1 MWh of renewable generation; can be sold separately from electricity.
- Carbon markets (cap-and-trade) set a cap on emissions; allowances are traded. Renewable projects can generate carbon offsets.
- Endangered Species Act and Migratory Bird Treaty Act can affect wind and solar siting; require biological assessments.
Must Know
- Understand the difference between compliance RECs and voluntary RECs.
- Know the key steps in an EIA: screening, scoping, impact analysis, mitigation, and public participation.
- Recognize the role of the Federal Energy Regulatory Commission (FERC) in interstate electricity sales and transmission.
- Be aware of the Production Tax Credit (PTC) and Investment Tax Credit (ITC) as federal incentives.
Field and Exam Application
- Prepare a REC purchase agreement for a corporation seeking to claim renewable energy use.
- Conduct a preliminary environmental screening for a wind farm to identify potential wetland or endangered species issues.
- Calculate the carbon offset potential of a landfill gas-to-energy project using methane capture.
High-Yield Distinctions
- RPS vs. Clean Energy Standard (CES): RPS typically includes only renewables; CES may include nuclear and other low-carbon sources.
- RECs vs. carbon offsets: RECs represent renewable generation; offsets represent emission reductions from any source.
- NEPA EIS vs. EA: EIS is more comprehensive and required for major federal actions; EA is a preliminary analysis.
Common Pitfalls
- Assuming RECs can be double-counted; each MWh generates exactly one REC.
- Overlooking state-specific permitting requirements (e.g., California's CEQA is more stringent than NEPA).
- Confusing carbon tax with cap-and-trade: carbon tax sets a price on emissions; cap-and-trade sets a quantity limit.
Review Tasks
- Research the RPS target in your state and the current compliance status.
- Review a sample EIS for a renewable project (e.g., from BLM or USFS).
- Calculate the number of RECs generated by a 100 MW wind farm with a 35% capacity factor over one year.
Site Assessment and System Design
Syllabus Focus
- Site selection criteria: solar access, wind resource, geotechnical, environmental constraints
- System design for PV: array sizing, inverter selection, wiring, shading analysis
- Wind turbine siting: spacing, wake effects, noise, and visual impact
- Balance of system components: mounting structures, transformers, switchgear
Key Notes
- PV array sizing: match inverter DC/AC ratio (typically 1.1-1.4) to optimize energy yield; consider module temperature coefficient and degradation.
- Shading analysis: use tools like PVsyst or Helioscope to model shade from nearby objects; even partial shading can cause significant losses.
- Wind turbine spacing: typically 3-5 rotor diameters apart in the prevailing wind direction, 5-7 diameters perpendicular to reduce wake losses.
- Geotechnical investigation: soil bearing capacity, frost depth, and seismic conditions affect foundation design for wind turbines and solar racking.
- Noise from wind turbines: limit to 45-55 dBA at nearby residences; low-frequency noise can be an issue.
Must Know
- Calculate the optimal tilt angle for a fixed PV array: latitude ± 10° for summer/winter optimization.
- Understand the impact of temperature on PV module voltage and current; use temperature coefficients for sizing.
- Know the difference between string inverters, microinverters, and power optimizers.
- Be familiar with wind turbine wake models (e.g., Jensen, Park) for array efficiency.
Field and Exam Application
- Design a ground-mount PV system with a given area, accounting for row spacing to avoid inter-row shading.
- Select a wind turbine model based on site wind class and noise constraints.
- Perform a geotechnical review for a solar farm foundation (driven piles vs. concrete ballasts).
High-Yield Distinctions
- Fixed-tilt vs. tracking systems: single-axis tracking increases yield by 15-25%; dual-axis by 25-40% but with higher O&M.
- String inverters vs. microinverters: string inverters are lower cost but suffer from mismatch losses; microinverters optimize per module.
- Horizontal-axis wind turbines (HAWT) vs. vertical-axis (VAWT): HAWT are more efficient and common; VAWT are less efficient but may be better for turbulent sites.
Common Pitfalls
- Ignoring snow load and wind load in structural design for solar racking.
- Underestimating wake losses in wind farms; typical losses are 5-15% depending on layout.
- Oversizing the inverter relative to the array (low DC/AC ratio) can reduce energy harvest during low irradiance.
Review Tasks
- Use PVWatts to model a 10 kW system at your location with different tilt angles and azimuths.
- Calculate the minimum row spacing for a PV array at latitude 40° to avoid shading at winter solstice noon.
- Review a wind farm layout optimization case study using OpenWind or similar software.
Operations, Maintenance, and Performance Monitoring
Syllabus Focus
- O&M best practices for solar, wind, and other renewables
- Performance metrics: availability, capacity factor, performance ratio (PR)
- Monitoring systems: SCADA, data acquisition, remote monitoring
- Troubleshooting common issues: inverter faults, soiling, blade erosion, gearbox failures
Key Notes
- Performance ratio (PR) for PV: ratio of actual yield to theoretical yield; typical PR is 0.75-0.85. PR accounts for all losses (temperature, inverter, wiring, soiling).
- Wind turbine O&M: scheduled maintenance includes oil changes, bolt torque checks, blade inspections; unscheduled includes gearbox and generator repairs.
- SCADA systems collect real-time data on power output, wind speed, temperature, and alarms; enable remote diagnostics.
- Soiling losses in PV: vary from 2-10% annually; cleaning frequency depends on location (rainfall, dust).
- Blade erosion in wind turbines: leading-edge erosion from rain and sand reduces aerodynamic efficiency; repaired with coatings or tapes.
Must Know
- Calculate availability: (hours online / total hours) × 100%. Target >97% for modern wind turbines.
- Understand the difference between scheduled and unscheduled maintenance and their impact on availability.
- Know common inverter failure modes: capacitor failure, IGBT short circuit, cooling fan failure.
- Be familiar with thermography for detecting hot spots in electrical connections and PV modules.
Field and Exam Application
- Analyze a PV system's SCADA data to identify a string with low current (possible module failure or shading).
- Schedule wind turbine major maintenance (e.g., gearbox replacement) during low-wind seasons to minimize lost production.
- Use drone-based infrared inspection to detect faulty PV cells or hot spots.
High-Yield Distinctions
- Performance ratio (PR) vs. capacity factor: PR is a measure of system efficiency; capacity factor is energy output relative to rated capacity.
- Condition-based maintenance vs. time-based maintenance: condition-based uses sensor data to predict failures; time-based follows fixed intervals.
- O&M costs as % of revenue: typically 1-2% for solar, 2-3% for wind, higher for offshore wind (3-5%).
Common Pitfalls
- Confusing availability with capacity factor; a turbine can be available but not generating due to low wind.
- Ignoring inverter efficiency curves; efficiency varies with load, typically highest at 50-75% load.
- Neglecting to calibrate sensors (anemometers, pyranometers) leading to inaccurate performance data.
Review Tasks
- Calculate the performance ratio for a PV system given monthly generation, irradiance, and rated capacity.
- Develop a preventive maintenance schedule for a 50 MW wind farm including annual, semi-annual, and quarterly tasks.
- Review a sample O&M contract and identify key performance guarantees (availability, power curve warranty).
How To Use These Notes With Practice Questions
Do not jump straight from reading to a full mock. Work by subject first: review the key notes, make a short recall sheet from memory, then answer a focused question set. After each miss, decide whether the problem was missing theory, weak code/source recall, poor measurement setup, calculation error, or a field sequence you did not visualize.
Technical Conquer's question bank, flashcards, mind maps, and spaced review tools are most useful after this instruction layer because they reveal which parts of the notes are not yet retrievable.
Final Review Checklist
- Review all six subjects, focusing on resource assessment, economics, grid integration, regulations, site design, and O&M.
- Practice LCOE, NPV, and performance ratio calculations with realistic inputs.
- Understand key standards: IEEE 1547, NEPA, and interconnection requirements.
- Be able to compare technologies (solar vs. wind vs. storage) on cost, resource, and environmental factors.
- Familiarize yourself with AEE's REP exam handbook and sample questions (if available).
- Verify current tax credits, RPS targets, and REC prices as they change frequently.
Official Sources and Further Reading
Use these sources as the final authority for format, eligibility, rules, regulatory limits, and exam updates. Study notes are a preparation layer, not a replacement for official candidate guidance.