Example 2: Solar Integration¶

This example shows how solar production and solar gain work together to create substantial cost savings.

Scenario¶

Date: March 20, 2025 (Spring Equinox) Location: Netherlands Weather: Sunny, temperatures 5-12°C Solar panels: 10 kWp system, south-facing Electricity pricing: Dynamic with production feed-in tariff

Configuration¶

Building:
  Area: 150 m²
  Energy Label: A+ (U-value: 0.35 W/m²K)
  Windows South: 15 m² (large south-facing windows)
  Windows East/West: 3 m² each

Heat Pump:
  Base COP: 4.2
  K-factor: 0.025
  Compensation: 0.92

Solar Production:
  Capacity: 10 kWp
  Orientation: South
  Feed-in tariff: €0.08/kWh

Input Data¶

Hourly Conditions (06:00 - 18:00)¶

Heat Balance¶

Key observation: Net demand is negative from 09:00 to 15:00 due to solar gain!

Optimization Strategy¶

Without Solar-Aware Optimization¶

Traditional heating would continue providing heat even when solar gain exceeds loss, wasting free energy.

With Solar-Aware Optimization¶

Detailed Optimization¶

Thermal Buffer Evolution¶

Amazing result: Zero heat pump operation from 09:00 to 23:00 (14 hours)!

Cost Analysis¶

Without Optimization¶

Continuous heating at current demand:

Total cost: €0.20 for morning heating only

With Optimization¶

Early morning pre-heat strategy:

Total daily cost: €0.30 + €0.23 (midnight) = €0.53

Cost comparison: Traditional heating without buffer: ~€1.80 vs. With optimization: €0.53

Solar Production Value¶

Effective Net Pricing¶

With solar production, the effective electricity price is:

\[ P_{net}(t) = P_{consumption}(t) - P_{production}(t) \]

During peak production (12:00):

• Consumption price: €0.35/kWh
• Production price (feed-in): €0.08/kWh
• Net price: €0.35 - €0.08 = €0.27/kWh

But heat pump not running, so effective cost is €0!

Solar Gain vs Solar Production¶

Two separate benefits:

1. Solar Gain (passive): Sunlight through windows heats the building
2. Free heat, reduces demand

3. Creates thermal buffer

4. Solar Production (active): PV panels generate electricity

5. Reduces net price of electricity
6. Can make effective price negative during excess production

Combined Effect¶

Optimization During Production Peaks¶

When PV production exceeds consumption, net price becomes negative:

\[ P_{net} = 0.35 - 0.08 - (P_{production} - P_{consumption}) \times 0.08 < 0 \]

During negative pricing, the optimizer actually prefers heating because:

• Heat pump consumption uses self-generated solar power
• Reduces export to grid (at low feed-in tariff)
• Stores energy as heat (in building thermal mass)

Buffer Capacity Reality Check¶

Did we claim 20.6 kWh buffer? Is this realistic?

Building Thermal Mass¶

Concrete floor (10 cm, 150 m²):

• Mass: 150 m² × 0.1 m × 2400 kg/m³ = 36,000 kg
• Specific heat: 1000 J/kg·K
• Temperature rise: 3°C (acceptable: 20°C → 23°C)
• Capacity: 36,000 × 1000 × 3 / 3,600,000 = 30 kWh

Yes, 20 kWh is realistic!

Seasonal Performance¶

Spring/Fall (like this example)¶

• High solar gain
• Moderate heat demand
• Savings: 50-70%

Winter¶

• Lower solar gain
• High heat demand
• Savings: 15-25%

Summer¶

• Very high solar gain
• Minimal/no heat demand
• Savings: Not applicable (no heating needed)

Key Takeaways¶

1. Solar Gain is Powerful¶

South-facing windows can provide 4-6 kW of free heat on sunny days.

2. Buffer Unlocks Value¶

Without buffer tracking, solar gain during zero-demand periods is wasted. With buffer:

• Store excess heat
• Use it hours later
• Eliminate heating for extended periods

3. Production + Gain Synergy¶

The combination of:

• Solar panels (electricity)
• South windows (passive heat)
• Good insulation (retain heat)
• Thermal mass (store heat)

Can reduce heating costs by 60-80% on optimal days.

4. Configuration Matters¶

To maximize solar benefits:

• ✓ Configure accurate window areas by orientation
• ✓ Enable production sensor
• ✓ Use dynamic pricing (to value self-consumption correctly)
• ✓ Set appropriate k-factor (efficient heat pump benefits more)

Next Example: Cold Snap Scenario - See how optimization handles extreme weather