Study guide
11.4 Biomass, Geothermal, Hydropower, Solar Thermal, and Waste-to-Energy Systems
AEE Certified Energy Manager CEM
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1 Chapter 1: Energy and Sustainability Policies, Codes, and Standards
1.1 Federal and State Energy Policies, Decarbonization Targets, and ESG Reporting 1.2 Building Energy Codes: ASHRAE Standard 90.1, IECC, and Compliance Paths 1.3 Energy Management Systems: ISO 50001, ENERGY STAR Benchmarking, and Portfolio Manager
2 Chapter 2: Energy Rates, Tariffs, and Supply Options
2.1 Utility Rate Structures: Volumetric vs. Demand Charges, Time-of-Use (TOU), and Real-Time Pricing 2.2 Demand Charges, Ratchets, Peak Shaving, and Power Factor Penalties 2.3 Energy Procurement, Deregulated Markets, Supply Contracts, and Green Tariffs 2.4 Demand-Side Management, Load Curtailment, and Transportation Energy Efficiency
3 Chapter 3: Energy Audits and Instrumentation
3.1 Energy Audit Methodologies: ASHRAE Level I, II, and III Audit Scopes 3.2 Audit Instrumentation, Data Loggers, Metering Accuracy, and Safety (PPE) 3.3 Baseline Energy Data, Utility Bill Disaggregation, and ECM Identification 3.4 Energy Modeling, Simulation, Digital Tools, and Performance Indicators
4 Chapter 4: Energy Accounting and Economics
4.1 Energy & Power Units (kWh, kW, Therms, MMBtu, Joules) and Conversion Calculations 4.2 Financial Metrics: Simple Payback Period, Return on Investment (ROI), and LCCA 4.3 Time Value of Money: Net Present Value (NPV), Internal Rate of Return (IRR), and Escalation 4.4 Advanced Financial Evaluation: Annual Worth, SIR, Depreciation, and Interest Formulas
5 Chapter 5: Electrical Power Systems and Motors
5.1 Electrical Fundamentals: Single/Three-Phase Power, Apparent/Real/Reactive Power, and Power Factor 5.2 Electric Motors: Efficiency Classes, Loading Calculations, NEMA Premium, and Losses 5.3 Variable Frequency Drives (VFDs), Affinity Laws, and Electrical Harmonics
6 Chapter 6: Lighting Systems
6.1 Lighting Fundamentals: Photometric Quantities (Lumens, Lux, Foot-Candles, CRI, CCT) and Efficacy 6.2 Lighting Technologies & Retrofits: LED Systems, Fluorescent/HID Replacement, and LPD 6.3 Lighting Controls: Occupancy/Vacancy Sensors, Daylight Harvesting, Dimming, and Task Tuning
7 Chapter 7: HVAC Systems and Building Envelope
7.1 HVAC Fundamentals & Psychrometrics: Dry-Bulb, Wet-Bulb, Dew Point, Relative Humidity, and Enthalpy 7.2 Cooling and Heating Equipment: Chillers (COP, kW/ton, EER, SEER), Heat Pumps, and Boilers 7.3 Air and Water Distribution: AHUs, VAV vs. CAV, Pumping Systems, Fans, and Economizers 7.4 Building Envelope: Heat Transfer (U-factor, R-value, SHGC), Infiltration, and Thermal Insulation 7.5 Building Envelope Calculations: Degree-Days, Solar Heat Gain, and Passive Design 7.6 Refrigerants, Cooling Towers, and Specialized HVAC Technologies (Absorption, VRF, Chilled Beams)
8 Chapter 8: Building Automation, Controls, and Artificial Intelligence Systems
8.1 Building Automation Systems (BAS) Architecture, BACnet, Modbus, and DDC Loops 8.2 Energy Control Strategies: Temperature/Pressure Resets, Night Setback, and Deadbands 8.3 Fault Detection & Diagnostics (FDD), Energy Analytics, and AI Optimization 8.4 IoT, Cloud-Based BAS, Expert Systems, and Cyber-Security
9 Chapter 9: Energy Storage Systems
9.1 Battery Energy Storage Systems (BESS): Technologies, Capacity, Efficiency, and Safety 9.2 Thermal Energy Storage (TES): Chilled Water, Ice Storage, and Phase Change Materials 9.3 Storage Dispatch Strategies, Tariff Integration, Peak Shaving, and Microgrid Integration
10 Chapter 10: Boiler and Steam Systems
10.1 Boiler Fundamentals & Efficiency: Combustion Efficiency, Excess Air, and Stack Losses 10.2 Steam Distribution & Traps: Steam Trap Types, Failure Modes, Testing, and Insulation 10.3 Condensate Recovery, Boiler Blowdown Control, and Waste Heat Recovery
11 Chapter 11: Distributed Generation and Renewable Energy Systems
11.1 Solar Photovoltaic (PV) and Wind Energy Systems: Design, Inverters, and Capacity Factor 11.2 Combined Heat and Power (CHP) / Cogeneration: Thermal Efficiency and System Sizing 11.3 Grid Interconnection, Net Metering, Islanding, and Microgrid Resilience 11.4 Biomass, Geothermal, Hydropower, Solar Thermal, and Waste-to-Energy Systems
12 Chapter 12: Industrial Systems
12.1 Compressed Air Systems: Efficiency, Pressure Drop, Leak Management, and Receiver Storage 12.2 Industrial Process Heating, Cooling Towers, and Industrial Refrigeration 12.3 Production-Normalized Energy Metrics, Pumping System Optimization, and Process Integration
13 Chapter 13: Operations, Maintenance, and Commissioning
13.1 Preventive, Predictive, and Reliability-Centered Maintenance Strategies 13.2 Building Commissioning: Existing Building Commissioning (EBCx) & Retro-Commissioning (RCx) 13.3 Savings Persistence, Continuous Commissioning, Sensor Calibration, and Alarms 13.4 Quantifying O&M Losses: Compressed Air Leaks, Steam Traps, Boiler Scale, and Group Relamping 13.5 CMMS, Water Treatment, and Human Behavior in Energy Management
14 Chapter 14: Energy Savings Performance Contracting and Measurement & Verification
14.1 Energy Savings Performance Contracting (ESPC), ESCO Roles, and Financing Models 14.2 Measurement and Verification (M&V): IPMVP Options A, B, C, and D 14.3 Baselines, Weather Normalization, Non-Routine Adjustments, and M&V Reporting
11.4 Biomass, Geothermal, Hydropower, Solar Thermal, and Waste-to-Energy Systems
Key Takeaways Explain This Topic AI
Biomass (wood chips, pellets, biogas, biofuels) can be combusted or gasified for heat and CHP; its carbon-neutrality depends on sustainable feedstock supply and regrowth, not on combustion chemistry.
Geothermal energy spans ground-source heat pumps (GSHPs) using shallow stable ground temperatures for high-COP heating/cooling and deep geothermal for direct steam/hot-water power generation.
Hydropower output follows P = η·ρ·g·Q·h; micro-hydro and run-of-river schemes serve facilities with on-site head and flow, while capacity factor depends on stream variability.
Solar thermal systems (flat-plate, evacuated-tube, and concentrating collectors) produce hot water, space heat, and industrial process heat; evacuated tubes outperform flat-plate at high temperature or cold climates.
Waste-to-Energy (WtE) recovers heat from municipal solid waste via mass-burn or RDF incineration, and district energy distributes that heat (and cooling) from a central plant across a network of connected buildings.
Last updated: July 2026
Biomass, Geothermal, Hydropower, Solar Thermal, and Waste-to-Energy Systems
Section 11.1 covered solar PV and wind, and Section 11.2 covered CHP. The CEM Body of Knowledge's Distributed Generation & Renewable Energy domain also lists Biomass, Geothermal, Hydropower, Solar Thermal Systems, Waste to Energy, and District Energy Systems . These resources fill niches that PV/wind cannot—high-temperature process heat, firm baseload, or heat-recovery-from-waste—and the CEM must know when each is the right tool.
Biomass Systems
Biomass converts organic feedstock—wood chips, pellets, agricultural residue, biogas from anaerobic digestion, and liquid biofuels—into heat, power, or both. Conversion routes:
Direct combustion in boilers or stoves for heat, often paired with steam turbines for CHP.
Gasification converts solid biomass to a combustible syngas for engines, turbines, or boilers.
Anaerobic digestion of organic waste produces biogas (≈60% methane) for boilers, CHP, or upgrading to RNG.
Carbon neutrality is the key nuance: combustion releases CO₂ immediately, but the feedstock regrew by absorbing CO₂, so the cycle is near-neutral if the feedstock is sustainably harvested and regrown. The CEM evaluates biomass on delivered-energy cost, feedstock supply security, ash handling, and emissions, not just on theoretical neutrality.
Geothermal Energy
Geothermal serves two distinct markets:
Ground-Source Heat Pumps (GSHPs / geoexchange) use the shallow ground's near-constant temperature (≈50–60°F) as a heat source in winter and a heat sink in summer. Because the loop exchanges with a mild source rather than cold winter air, GSHPs achieve COPs of 3–5 , well above air-source heat pumps. Loop types include closed-loop vertical, horizontal, and pond, plus open-loop groundwater.
Deep geothermal taps hydrothermal reservoirs for direct steam or hot water to drive turbines or supply district heat—economical only where the resource is close to the surface (e.g., the U.S. West, Iceland).
GSHP economics hinge on the loop installation cost (often the majority of first cost) and ground thermal conductivity; the CEM models lifetime COP against the local electricity and fossil-fuel prices.
Hydropower
Hydropower converts the energy of falling water: P = η · ρ · g · Q · h , where η is turbine/generator efficiency, ρ water density (1000 kg/m³), g gravity (9.81 m/s²), Q flow (m³/s), and h head (m).
For facilities with on-site streams, micro-hydro (typically <100 kW) and run-of-river schemes (no large reservoir) can supply firm baseload at very low operating cost. The catch is capacity factor : stream flow varies seasonally, so the CEM sizes the turbine to the firm (exceedance) flow, not the peak, to avoid chronic under-generation. Hydropower is among the highest-capacity-factor renewables when the resource is stable.
Solar Thermal Systems
Unlike PV (which makes electricity), solar thermal makes heat. Collector types:
- Collector Temperature Best Use
- Flat-plate Low–medium (to ~80°C) Domestic hot water, pool/space heating
- Evacuated-tube Medium (~100–200°C) Hot water/heating in cold climates, process heat
- Concentrating (parabolic trough, dish) High (>200°C) Industrial process heat, solar-thermal power
Applications include solar hot water (the most common), solar space heating, and Solar Industrial Process Heat (SHIP) for food, textile, and chemical operations. The CEM sizes collectors against the load's temperature and the local solar irradiance (kWh/m²·day), and accounts for freeze protection, storage, and backup. Evacuated tubes outperform flat-plate at high delivery temperatures or in cold climates because the vacuum cuts convective loss.
Waste-to-Energy (WtE)
Waste-to-Energy recovers heat from municipal solid waste (MSW):
Mass-burn incinerates MSW as-received; the heat raises steam for power or district heat.
Refuse-Derived Fuel (RDF) processes waste into a more uniform fuel before combustion.
WtE serves a dual purpose—volume reduction of landfill-bound waste and energy recovery. The CEM evaluates WtE on tipping-fee revenue, emissions control (acid gases, dioxins, mercury), ash disposal, and base-load dispatchability (WtE runs ~24/7, unlike wind/solar). It pairs naturally with district energy .
District Energy Systems
District energy centralizes heating and/or cooling production and distributes it through insulated pipe networks to many connected buildings. A central plant can use CHP (Section 11.2), biomass, WtE, or large chillers/heat pumps at efficiencies and economies of scale no single building can match. Benefits:
Higher efficiency from large, well-maintained central equipment.
Fuel flexibility —switch the central plant without touching customer buildings.
Space recovery in connected buildings (no local boiler/chiller rooms).
Resilience —redundant central plants ride through outages.
The CEM evaluates district connection against the connection fee, per-unit energy tariff, and the avoided cost of in-plant equipment replacement. For dense campuses, hospitals, and downtown cores, district energy is often the lowest-life-cycle-cost option.
Selecting Across the Renewable Mix
The CEM matches the resource to the load's character:
High-temperature process heat → solar thermal (concentrating) or biomass.
Firm baseload with on-site water → micro-hydro.
Heating/cooling with mild ground → GSHP.
Waste stream + heat demand → WtE or biogas CHP.
Dense multi-building load → district energy fed by any of the above.
No single renewable fits every site; the CEM's value is selecting—and often combining—the right resource for the load, climate, and waste stream at hand.