app.py

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import streamlit as st
from typing import Dict, Tuple

# Constants
ONE_BR_UNITS = 23
TWO_BR_UNITS = 45
SOLAR_PANEL_RATING = 625  # W
SOLAR_PANEL_COST = 13000  # KSH per panel
BATTERY_CAPACITY = 200  # Ah
BATTERY_VOLTAGE = 12  # V
BATTERY_COST = 39000  # KSH per battery
SYSTEM_LOSSES = 0.20  # 20% system losses
GRID_COST_PER_KWH = 25  # KSH
FEED_IN_TARIFF = 12  # KSH per kWh sold back to grid

# Consumption estimates (kWh/month)
ONE_BR_CONSUMPTION = 250
TWO_BR_CONSUMPTION = 400
COMMON_AREA_CONSUMPTION = 1500  # For entire complex


def initialize_session_state():
    """Initialize session state variables"""
    if "solar_panels" not in st.session_state:
        st.session_state.solar_panels = 100
    if "batteries" not in st.session_state:
        st.session_state.batteries = 50


def calculate_consumption(one_br_occupancy: float, two_br_occupancy: float) -> float:
    """Calculate total monthly consumption based on occupancy rates"""
    total_consumption = (
        one_br_occupancy * ONE_BR_UNITS * ONE_BR_CONSUMPTION
        + two_br_occupancy * TWO_BR_UNITS * TWO_BR_CONSUMPTION
        + COMMON_AREA_CONSUMPTION
    )
    return total_consumption


def solar_production(panel_count: int, sun_hours: float = 5) -> float:
    """Calculate daily solar production considering losses"""
    daily_production = (
        panel_count * SOLAR_PANEL_RATING * sun_hours * (1 - SYSTEM_LOSSES) / 1000
    )  # kWh
    monthly_production = daily_production * 30
    return monthly_production


def battery_storage(battery_count: int) -> float:
    """Calculate usable battery storage considering losses"""
    total_capacity = battery_count * BATTERY_CAPACITY * BATTERY_VOLTAGE / 1000  # kWh
    usable_capacity = total_capacity * (1 - SYSTEM_LOSSES)
    return usable_capacity


def financial_analysis(
    monthly_consumption: float,
    solar_production: float,
    battery_capacity: float,
    panel_count: int,
    battery_count: int,
) -> Dict[str, float]:
    """
    Calculate financial metrics including costs, savings, and ROI
    """
    # Initial investment
    panel_cost = panel_count * SOLAR_PANEL_COST
    battery_cost = battery_count * BATTERY_COST
    total_investment = panel_cost + battery_cost

    # Energy calculations
    solar_used = min(solar_production, monthly_consumption)
    excess_solar = max(solar_production - monthly_consumption, 0)
    grid_purchased = max(monthly_consumption - solar_used, 0)

    # Battery can store excess or reduce grid purchases
    battery_stored = min(excess_solar, battery_capacity)
    battery_used = min(grid_purchased, battery_capacity)

    # Final energy flows
    final_grid_purchased = max(grid_purchased - battery_used, 0)
    final_excess_solar = max(excess_solar - battery_stored, 0)

    # Financial calculations
    grid_cost = final_grid_purchased * GRID_COST_PER_KWH
    feed_in_income = final_excess_solar * FEED_IN_TARIFF
    savings = (monthly_consumption * GRID_COST_PER_KWH) - grid_cost + feed_in_income

    return {
        "total_investment": total_investment,
        "monthly_savings": savings,
        "annual_savings": savings * 12,
        "simple_payback_years": (
            total_investment / (savings * 12) if savings > 0 else float("inf")
        ),
        "grid_purchased": final_grid_purchased,
        "excess_solar": final_excess_solar,
        "battery_utilization": (
            (battery_used + battery_stored) / battery_capacity
            if battery_capacity > 0
            else 0
        ),
        "solar_coverage": (
            solar_used / monthly_consumption if monthly_consumption > 0 else 0
        ),
    }


def plot_scenario_comparison(results: Dict[str, Dict[str, float]]):
    """Plot comparison of different occupancy scenarios"""
    scenarios = list(results.keys())

    # Prepare data for plotting
    metrics = {
        "Monthly Consumption (kWh)": [results[s]["consumption"] for s in scenarios],
        "Solar Production (kWh)": [results[s]["solar_production"] for s in scenarios],
        "Grid Purchased (kWh)": [
            results[s]["financials"]["grid_purchased"] for s in scenarios
        ],
        "Excess Solar (kWh)": [
            results[s]["financials"]["excess_solar"] for s in scenarios
        ],
    }

    # Create figure
    fig, axes = plt.subplots(2, 2, figsize=(15, 12))
    axes = axes.flatten()

    for i, (title, values) in enumerate(metrics.items()):
        axes[i].bar(scenarios, values, color=plt.cm.tab20(i))
        axes[i].set_title(title)
        axes[i].tick_params(axis="x", rotation=45)

        # Add value labels
        for j, v in enumerate(values):
            axes[i].text(j, v * 1.02, f"{v:,.0f}", ha="center", va="bottom")

    plt.tight_layout()
    st.pyplot(fig)


def plot_financial_comparison(results: Dict[str, Dict[str, float]]):
    """Plot financial comparison across scenarios"""
    scenarios = list(results.keys())

    # Prepare financial data
    financial_metrics = {
        "Monthly Savings (Ksh)": [
            results[s]["financials"]["monthly_savings"] for s in scenarios
        ],
        "Solar Coverage (%)": [
            results[s]["financials"]["solar_coverage"] * 100 for s in scenarios
        ],
        "Payback Period (Years)": [
            results[s]["financials"]["simple_payback_years"] for s in scenarios
        ],
        "Battery Utilization (%)": [
            results[s]["financials"]["battery_utilization"] * 100 for s in scenarios
        ],
    }

    # Create figure
    fig, axes = plt.subplots(2, 2, figsize=(15, 12))
    axes = axes.flatten()

    for i, (title, values) in enumerate(financial_metrics.items()):
        if title == "Payback Period (Years)":
            # For payback period, we'll do a horizontal bar chart
            axes[i].barh(scenarios, values, color=plt.cm.tab20(3))
            axes[i].set_xlabel(title)

            # Add value labels
            for j, v in enumerate(values):
                if np.isfinite(v):
                    axes[i].text(v * 1.02, j, f"{v:.1f}", va="center")
                else:
                    axes[i].text(0, j, "Never", va="center")
        else:
            axes[i].bar(scenarios, values, color=plt.cm.tab20(i + 4))
            axes[i].set_title(title)
            axes[i].tick_params(axis="x", rotation=45)

            # Add value labels
            for j, v in enumerate(values):
                axes[i].text(j, v * 1.02, f"{v:,.1f}", ha="center", va="bottom")

    plt.tight_layout()
    st.pyplot(fig)


def main():
    st.set_page_config(
        page_title="Apartment Complex Solar Analysis", page_icon="🏢", layout="wide"
    )

    # Initialize session state
    initialize_session_state()

    # Main title and description
    st.title("🏢 Apartment Complex Solar Energy Analysis")
    st.markdown(
        """
    This tool analyzes solar energy potential for a complex with:
    - 45 two-bedroom units
    - 23 one-bedroom units
    
    Comparing three specific occupancy scenarios with 2BR at 100% occupancy and varying 1BR occupancy.
    """
    )

    # Sidebar for system configuration
    with st.sidebar:
        st.header("System Configuration")
        st.session_state.solar_panels = st.number_input(
            "Number of Solar Panels",
            min_value=0,
            max_value=1000,
            value=st.session_state.solar_panels,
            step=1,
        )

        st.session_state.batteries = st.number_input(
            "Number of Batteries",
            min_value=0,
            max_value=500,
            value=st.session_state.batteries,
            step=1,
        )

        st.markdown("---")
        st.markdown(
            f"**Panel Specifications:** {SOLAR_PANEL_RATING}W @ Ksh{SOLAR_PANEL_COST:,} each"
        )
        st.markdown(
            f"**Battery Specifications:** {BATTERY_CAPACITY}Ah @ Ksh{BATTERY_COST:,} each"
        )
        st.markdown(f"**System Losses:** {SYSTEM_LOSSES*100:.0f}%")

    # Define the specific scenarios
    scenarios = {
        "1BR: 0%, 2BR: 100%": {"1br": 0.0, "2br": 1.0},
        "1BR: 25%, 2BR: 100%": {"1br": 0.25, "2br": 1.0},
        "1BR: 50%, 2BR: 100%": {"1br": 0.5, "2br": 1.0},
    }

    # Calculate results for each scenario
    results = {}
    for scenario, occupancy in scenarios.items():
        # Calculate consumption and production
        consumption = calculate_consumption(occupancy["1br"], occupancy["2br"])
        production = solar_production(st.session_state.solar_panels)
        storage = battery_storage(st.session_state.batteries)

        # Financial analysis
        financials = financial_analysis(
            consumption,
            production,
            storage,
            st.session_state.solar_panels,
            st.session_state.batteries,
        )

        results[scenario] = {
            "consumption": consumption,
            "solar_production": production,
            "battery_capacity": storage,
            "financials": financials,
        }

    # Display system summary
    st.subheader("System Summary")
    col1, col2, col3, col4 = st.columns(4)
    col1.metric("Total Solar Panels", st.session_state.solar_panels)
    col2.metric("Total Batteries", st.session_state.batteries)
    col3.metric(
        "Total Investment",
        f"Ksh{(st.session_state.solar_panels * SOLAR_PANEL_COST + st.session_state.batteries * BATTERY_COST):,}",
    )
    col4.metric(
        "Total Solar Capacity",
        f"{st.session_state.solar_panels * SOLAR_PANEL_RATING / 1000:.1f} kW",
    )

    # Display scenario comparison
    st.subheader("Scenario Comparison: Energy Flows")
    plot_scenario_comparison(results)

    st.subheader("Scenario Comparison: Financial Metrics")
    plot_financial_comparison(results)

    # Detailed results for each scenario
    st.subheader("Detailed Results by Scenario")

    for scenario, data in results.items():
        with st.expander(f"Scenario: {scenario}"):
            col1, col2, col3 = st.columns(3)

            # Energy metrics
            col1.metric("Monthly Consumption", f"{data['consumption']:,.0f} kWh")
            col2.metric("Solar Production", f"{data['solar_production']:,.0f} kWh")
            col3.metric("Battery Capacity", f"{data['battery_capacity']:,.1f} kWh")

            # Financial metrics
            col1.metric(
                "Monthly Savings", f"Ksh{data['financials']['monthly_savings']:,.0f}"
            )
            col2.metric(
                "Annual Savings", f"Ksh{data['financials']['annual_savings']:,.0f}"
            )

            payback = data["financials"]["simple_payback_years"]
            payback_text = f"{payback:.1f} years" if np.isfinite(payback) else "Never"
            col3.metric("Simple Payback Period", payback_text)

            # Energy flow details
            st.markdown("#### Energy Flow Details")
            flow_data = {
                "Metric": [
                    "Grid Purchased",
                    "Excess Solar",
                    "Solar Coverage",
                    "Battery Utilization",
                ],
                "Value": [
                    f"{data['financials']['grid_purchased']:,.0f} kWh",
                    f"{data['financials']['excess_solar']:,.0f} kWh",
                    f"{data['financials']['solar_coverage']*100:.1f}%",
                    f"{data['financials']['battery_utilization']*100:.1f}%",
                ],
            }
            st.table(pd.DataFrame(flow_data))


if __name__ == "__main__":
    main()