A residential photovoltaic (PV)-storage system primarily consists of PV modules, energy storage batteries, storage inverters, metering devices, and monitoring management systems. Its goal is to achieve energy self-sufficiency, reduce energy costs, lower carbon emissions, and improve power reliability. Configuring a residential PV-storage system is a comprehensive process that requires careful consideration of various factors to ensure efficient and stable operation.
I. Overview of Residential PV-Storage Systems
Before initiating the system setup, it is essential to measure the DC insulation resistance between the PV array input terminal and the ground. If the resistance is less than U…/30mA (U… represents the maximum output voltage of the PV array), additional grounding or insulation measures must be taken.
The primary functions of residential PV-storage systems include:
- Self-consumption: Utilizing solar energy to meet household energy demands.
- Peak-shaving and valley-filling: Balancing energy usage across different times to save on energy costs.
- Backup power: Providing reliable energy during outages.
- Emergency power supply: Supporting critical loads during grid failure.
The configuration process includes analyzing user energy needs, designing PV and storage systems, selecting components, preparing installation plans, and outlining operation and maintenance measures.
II. Demand Analysis and Planning
Energy Demand Analysis
Detailed energy demand analysis is critical, including:
- Load profiling: Identifying the power requirements of various appliances.
- Daily consumption: Determining the average electricity usage during the day and night.
- Electricity pricing: Understanding tariff structures to optimize the system for cost savings.
Case Study
| Table 1 Total load statistics | |||
| equipment | Power | Quantity | Total power (kW) |
| Inverter air conditioner | 1.3 | 3 | 3.9kW |
| washing machine | 1.1 | 1 | 1.1kW |
| Refrigerator | 0.6 | 1 | 0.6kW |
| TV | 0.2 | 1 | 0.2kW |
| Water heater | 1.0 | 1 | 1.0kW |
| Random hood | 0.2 | 1 | 0.2kW |
| Other electricity | 1.2 | 1 | 1.2kW |
| Total | 8.2kW | ||
| Table 2 Statistics of important loads (off-grid power supply) | |||
| equipment | Power | Quantity | Total power (kW) |
| Inverter air conditioner | 1.3 | 1 | 1.3kW |
| Refrigerator | 0.6 | 1 | 0.6kW |
| Water heater | 1.0 | 1 | 1.0kW |
| Random hood | 0.2 | 1 | 0.2kW |
| Lighting electricity, etc. | 0.5 | 1 | 0.5kW |
| Total | 3.6kW | ||
- User Profile:
- Total connected load: 8.2 kW
- Critical load: 3.6 kW
- Daytime energy consumption: 10 kWh
- Nighttime energy consumption: 20 kWh
- System Plan:
- Install a PV-storage hybrid system with daytime PV generation meeting load demands and storing excess energy in batteries for nighttime use. The grid acts as a supplementary power source when PV and storage are insufficient.
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III. System Configuration and Component Selection
1. PV System Design
- System Size: Based on the user’s 8.2 kW load and daily consumption of 30 kWh, a 12 kW PV array is recommended. This array can generate approximately 36 kWh per day to meet demand.
- PV Modules: Utilize 21 single-crystal 580Wp modules, achieving an installed capacity of 12.18 kWp. Ensure optimal arrangement for maximum sunlight exposure.
Maximum power Pmax [W] 575 580 585 590 595 600 Optimum operating voltage Vmp [V] 43.73 43.88 44.02 44.17 44.31 44.45 Optimum operating current Imp [A] 13.15 13.22 13.29 13.36 13.43 13.50 Open circuit voltage Voc [V] 52.30 52.50 52.70 52.90 53.10 53.30 Short circuit current Isc [A] 13.89 13.95 14.01 14.07 14.13 14.19 Module efficiency [%] 22.3 22.5 22.7 22.8 23.0 23.2 Output power tolerance 0~+3% Temperature coefficient of maximum power[Pmax] -0.29%/℃ Temperature coefficient of open circuit voltage [Voc] -0.25%/℃ Temperature coefficient of short circuit current [Isc] 0.045%/℃ Standard Test Conditions (STC): Light intensity 1000W/m², battery temperature 25℃, air quality 1.5 2. Energy Storage System
- Battery Capacity: Configure a 25.6 kWh lithium iron phosphate (LiFePO4) battery system. This capacity ensures sufficient backup for critical loads (3.6 kW) for approximately 7 hours during outages.
- Battery Modules: Employ modular, stackable designs with IP65-rated enclosures for indoor/outdoor installations. Each module has a capacity of 2.56 kWh, with 10 modules forming the complete system.
3. Inverter Selection
- Hybrid Inverter: Use a 10 kW hybrid inverter with integrated PV and storage management capabilities. Key features include:
- Maximum PV input: 15 kW
- Output: 10 kW for both grid-tied and off-grid operation
- Protection: IP65 rating with grid-off-grid switching time <10 ms
4. PV Cable Selection
PV cables connect solar modules to the inverter or combiner box. They must endure high temperatures, UV exposure, and outdoor conditions.
- EN 50618 H1Z2Z2-K:
- Single-core, rated for 1.5 kV DC, with excellent UV and weather resistance.
- TÜV PV1-F:
- Flexible, flame-retardant, with a wide temperature range (-40°C to +90°C).
- UL 4703 PV Wire:
- Double-insulated, ideal for rooftop and ground-mounted systems.
- AD8 Floating Solar Cable:
- Submersible and waterproof, suitable for humid or aquatic environments.
- Aluminum Core Solar Cable:
- Lightweight and cost-effective, used in large-scale installations.
5. Energy Storage Cable Selection
Storage cables connect batteries to inverters. They must handle high currents, provide thermal stability, and maintain electrical integrity.
- UL10269 and UL11627 Cables:
- Thin-wall insulated, flame-retardant, and compact.
- XLPE-Insulated Cables:
- High voltage (up to 1500V DC) and thermal resistance.
- High-Voltage DC Cables:
- Designed for interconnecting battery modules and high-voltage buses.
Recommended Cable Specifications
Cable Type Recommended Model Application PV Cable EN 50618 H1Z2Z2-K Connecting PV modules to the inverter. PV Cable UL 4703 PV Wire Rooftop installations requiring high insulation. Energy Storage Cable UL 10269, UL 11627 Compact battery connections. Shielded Storage Cable EMI Shielded Battery Cable Reducing interference in sensitive systems. High Voltage Cable XLPE-Insulated Cable High-current connections in battery systems. Floating PV Cable AD8 Floating Solar Cable Water-prone or humid environments.
IV. System Integration
Integrate PV modules, energy storage, and inverters into a complete system:
- PV System: Design module layout and ensure structural safety with appropriate mounting systems.
- Energy Storage: Install modular batteries with proper BMS (Battery Management System) integration for real-time monitoring.
- Hybrid Inverter: Connect PV arrays and batteries to the inverter for seamless energy management.
V. Installation and Maintenance
Installation:
- Site Assessment: Inspect rooftops or ground areas for structural compatibility and sunlight exposure.
- Equipment Installation: Securely mount PV modules, batteries, and inverters.
- System Testing: Verify electrical connections and perform functional tests.
Maintenance:
- Routine Inspections: Check cables, modules, and inverters for wear or damage.
- Cleaning: Regularly clean PV modules to maintain efficiency.
- Remote Monitoring: Use software tools to track system performance and optimize settings.
VI. Conclusion
A well-designed residential PV-storage system delivers energy savings, environmental benefits, and power reliability. The careful selection of components such as PV modules, energy storage batteries, inverters, and cables ensures the system’s efficiency and longevity. By following proper planning,
installation, and maintenance protocols, homeowners can maximize the benefits of their investment.
Post time: Dec-24-2024