# Renewable Energy Systems

## Solar Photovoltaic (PV)

### System Types
| Type | Description | Application |
|------|-------------|-------------|
| Roof-mounted | On existing roof | Most common |
| Ground-mounted | On ground racking | Large systems, rural |
| Building-integrated (BIPV) | Replace building materials | Architectural |
| Carport/canopy | Over parking | Commercial, multifamily |
| Floating | On water bodies | Reservoirs, ponds |

### Module Technologies
| Type | Efficiency | Cost | Notes |
|------|------------|------|-------|
| Monocrystalline | 18-22% | $$$ | Most common, best efficiency |
| Polycrystalline | 15-17% | $$ | Lower cost, less efficient |
| Thin-film | 10-13% | $ | Flexible, low efficiency |
| Bifacial | 20-25% | $$$$ | Collects light both sides |
| PERC | 20-23% | $$$ | Enhanced rear surface |

### System Sizing
| Building Type | Watts/SF Roof | Notes |
|---------------|---------------|-------|
| Residential | 4-5 W/sf | Based on available roof |
| Commercial | 10-15 W/sf | Flat roof, optimal tilt |
| Industrial | 15-20 W/sf | Large flat roofs |

### Roof Requirements
| Factor | Requirement |
|--------|-------------|
| Structural capacity | 3-5 PSF additional |
| Age | < 10 years remaining (or reroof) |
| Orientation | South preferred (±45°) |
| Shading | < 10% annual shading |
| Access | 3' perimeter, pathways |
| Fire setbacks | Per local fire code |

### Electrical Components
| Component | Function |
|-----------|----------|
| Modules | Generate DC power |
| Inverter | DC to AC conversion |
| Racking | Mounting structure |
| Combiner box | Aggregate strings |
| Disconnect | Safety isolation |
| Meter | Production monitoring |
| Rapid shutdown | NEC 2017+ safety |

### Inverter Types
| Type | Application | Efficiency |
|------|-------------|------------|
| String inverter | Residential, small commercial | 97-99% |
| Microinverter | Shaded roofs, complex | 95-97% |
| Power optimizer | Partial shading | 98-99% |
| Central inverter | Large commercial | 97-99% |

---

## Energy Storage

### Battery Technologies
| Type | Energy Density | Cycle Life | Cost |
|------|---------------|------------|------|
| Lithium-ion (NMC) | High | 3,000-5,000 | $$$ |
| Lithium iron phosphate (LFP) | Medium | 5,000-10,000 | $$ |
| Lead-acid | Low | 500-1,000 | $ |
| Flow batteries | Low | 10,000+ | $$$$ |
| Sodium-ion | Medium | 3,000-5,000 | $$ |

### Residential Storage
| Product | Capacity | Power | Notes |
|---------|----------|-------|-------|
| Tesla Powerwall | 13.5 kWh | 5 kW | Most common |
| Enphase IQ | 5 kWh | 3.84 kW | Modular |
| LG Chem RESU | 9.8 kWh | 5 kW | High density |
| Generac PWRcell | 9-18 kWh | 9 kW | Scalable |

### Commercial Storage
| Application | Sizing | Benefit |
|-------------|--------|---------|
| Demand charge reduction | 15-30 min peak | 20-40% bill savings |
| TOU arbitrage | 2-4 hour capacity | Rate optimization |
| Backup power | 4-8 hours | Business continuity |
| Grid services | Variable | Revenue stream |

### Sizing Considerations
| Factor | Impact |
|--------|--------|
| Critical loads | Determines minimum capacity |
| Outage duration | Hours of backup needed |
| Solar pairing | Self-consumption optimization |
| Demand charges | Peak shaving duration |
| Utility rates | TOU differential |

---

## Net Zero Design

### Definition Levels
| Level | Description |
|-------|-------------|
| Net Zero Site Energy | On-site generation = consumption |
| Net Zero Source Energy | Accounts for grid losses |
| Net Zero Energy Cost | Energy bill = $0 |
| Net Zero Carbon | No carbon emissions |

### Design Strategies
| Priority | Strategy | Impact |
|----------|----------|--------|
| 1 | Reduce loads | 30-50% reduction |
| 2 | Passive design | 10-30% reduction |
| 3 | Efficient systems | 20-40% reduction |
| 4 | Renewable generation | Offset remaining |

### Load Reduction Targets
| Building Type | Target EUI (kBtu/sf) |
|---------------|----------------------|
| Office | 25-35 |
| School | 25-40 |
| Retail | 30-45 |
| Multifamily | 25-40 |
| Single-family | 15-25 |

### Passive Strategies
| Strategy | Benefit |
|----------|---------|
| Orientation | Optimize solar gain |
| Glazing ratio | Balance daylight/heat gain |
| Thermal mass | Moderate temperature swings |
| Natural ventilation | Reduce cooling loads |
| Daylighting | Reduce lighting loads |
| Shading | Control solar heat gain |

---

## Solar Thermal

### System Types
| Type | Temperature | Application |
|------|-------------|-------------|
| Flat plate | 100-150°F | DHW, pools |
| Evacuated tube | 150-250°F | DHW, space heating |
| Unglazed | 70-100°F | Pool heating |
| Concentrating | 300-750°F | Industrial process |

### Domestic Hot Water
| Climate | Solar Fraction |
|---------|----------------|
| Sunny (AZ, FL) | 70-90% |
| Moderate (CA, TX) | 60-80% |
| Cold/cloudy (WA, NY) | 40-60% |

### Sizing Rules
| Application | Collector Area |
|-------------|----------------|
| DHW (per person) | 15-20 SF |
| Pool heating | 50-100% of pool area |
| Space heating | 10-20% of floor area |

### Components
| Component | Function |
|-----------|----------|
| Collectors | Absorb solar heat |
| Storage tank | Store heated water |
| Heat exchanger | Transfer heat |
| Pump/controls | Circulate fluid |
| Expansion tank | Pressure relief |
| Freeze protection | Drain-back or glycol |

---

## Geothermal Heat Pumps

### System Types
| Type | Description | Application |
|------|-------------|-------------|
| Vertical closed loop | Bore holes | Limited land area |
| Horizontal closed loop | Trenches | Adequate land |
| Pond/lake | Submerged loops | Water body available |
| Open loop | Well water | Good water quality |
| Standing column | Single deep well | Specific geology |

### Sizing Guidelines
| Factor | Guideline |
|--------|-----------|
| Bore depth | 150-400 ft per ton |
| Bore spacing | 15-20 ft apart |
| Horizontal loop | 400-600 ft per ton |
| Pond loop | 300-500 ft per ton |

### Performance
| Metric | Value |
|--------|-------|
| Heating COP | 3.5-5.0 |
| Cooling EER | 14-25 |
| Life expectancy | 25+ years (loop: 50+) |
| Energy savings | 30-60% vs conventional |

### Costs
| Component | Cost per Ton |
|-----------|--------------|
| Vertical bore | $3,000-5,000 |
| Horizontal loop | $1,500-3,000 |
| Heat pump unit | $1,500-2,500 |
| Total installed | $15,000-30,000 |

---

## Wind Energy

### Small Wind
| Size | Output | Application |
|------|--------|-------------|
| Micro (< 1 kW) | 500-1,000 kWh/yr | Off-grid, remote |
| Small (1-10 kW) | 2,000-15,000 kWh/yr | Residential |
| Medium (10-100 kW) | 20,000-200,000 kWh/yr | Commercial, farm |

### Site Assessment
| Factor | Requirement |
|--------|-------------|
| Average wind speed | ≥ 10 mph annual |
| Tower height | 80-140 ft |
| Setbacks | 1.5× tower height |
| Zoning | Check local regulations |
| Obstacles | None upwind |

### Building-Integrated
| Type | Notes |
|------|-------|
| Rooftop turbines | Low output, vibration issues |
| Building-augmented | Accelerated airflow |
| Vertical axis | Lower noise, omni-directional |

---

## Code Requirements

### Solar-Ready (2021 IECC)
| Requirement | Specification |
|-------------|---------------|
| Roof structural | 4 PSF additional load |
| Conduit | 3/4" from roof to electrical |
| Panel space | Reserved for future inverter |
| Roof area | Minimum solar zone |

### EV-Ready (2021 IECC)
| Building Type | Requirement |
|---------------|-------------|
| 1-2 family | 1 EV-ready space |
| Multifamily | 20% EV-capable |
| Commercial | Varies by jurisdiction |

### NEC Requirements (Solar)
| Section | Requirement |
|---------|-------------|
| 690 | PV system installation |
| 705 | Interconnection |
| 480.6 | Rapid shutdown |
| 110.26 | Working clearances |

### Fire Code
| Requirement | Specification |
|-------------|---------------|
| Ridge setback | 3 ft from ridge |
| Perimeter setback | 3 ft from edge |
| Pathways | 3 ft wide, every 150 ft |
| Ventilation | Per local fire marshal |

---

## Incentives and Economics

### Federal Incentives (2024)
| Incentive | Value |
|-----------|-------|
| Solar ITC (residential) | 30% of system cost |
| Solar ITC (commercial) | 30% + bonus adders |
| Storage ITC | 30% (standalone eligible) |
| Geothermal credit | 30% through 2032 |

### ITC Bonus Adders
| Adder | Additional Credit |
|-------|-------------------|
| Domestic content | +10% |
| Energy community | +10% |
| Low-income | +10-20% |

### State/Utility Incentives
| Type | Examples |
|------|----------|
| Rebates | $/watt upfront |
| SRECs | Tradeable certificates |
| Net metering | Full retail credit |
| Feed-in tariff | Fixed rate for exports |
| Property tax exemption | No added assessment |

### Financial Metrics
| Metric | Good Value |
|--------|------------|
| Simple payback | < 7 years |
| Levelized cost (LCOE) | < $0.10/kWh |
| IRR | > 10% |
| NPV | Positive |

---

## Integration Considerations

### Electrical Capacity
| Consideration | Impact |
|---------------|--------|
| Service size | May need upgrade |
| Panel space | Breakers for solar/storage |
| Interconnection | Utility approval |
| Export limits | Some utilities restrict |

### Structural
| Consideration | Impact |
|---------------|--------|
| Roof load | 3-5 PSF for solar |
| Roof age | Reroof first if needed |
| Attachments | Flashing, waterproofing |
| Wind loads | Increased uplift |

### Architectural
| Consideration | Approach |
|---------------|----------|
| Visibility | Integrate into design |
| Color | Black frames, black cells |
| Array layout | Aligned with roof edges |
| BIPV | Replace roofing/glazing |

### Operations
| Consideration | Impact |
|---------------|--------|
| Monitoring | Real-time production |
| Maintenance | Annual inspection |
| Snow/debris | Cleaning access |
| Warranty | 25-year production |
