Research and Application of Wind-Solar Complementary Power Generation System

1.Technical Overview

The wind-solar complementary power generation system combines wind turbines and solar PV arrays as two types of power generation devices. It is mainly divided into off-grid and grid-connected types.

1.1 Off-grid system

Off-grid systems utilize solar PV arrays and wind turbines to store generated electricity in battery banks. The inverter converts stored DC power into AC power, which is transmitted to users’ loads through transmission lines.

1.2 Grid-connected system

The grid-connected type mainly consists of a power generation system composed of wind turbines, solar PV arrays, intelligent controllers, battery banks, multi-functional inverters, cables, support structures, and auxiliary components. It feeds the generated electricity into the conventional grid.

2.Technical Principles

The main principle of the off-grid wind-solar complementary power supply system is as follows: Wind turbines generate DC current by using the wind to drive the three blades and interact with the permanent magnet generator.

The DC current enters the battery bank through the cable and is stored.  When electricity is needed, the inverter converts the DC power from the battery bank into AC power for office, living, or lighting use.  Solar power generation converts solar energy into electrical energy and stores it in the battery bank.

The wind-solar complementary grid-connected power supply system includes several main components:

2.1 Photovoltaic system

The photovoltaic system consists of photovoltaic arrays and DC/DC converters. The DC/DC converter is utilized to optimize power generation by matching the voltage of the photovoltaic array to the DC bus voltage, enabling maximum power tracking.

2.2 Wind power system

The wind power system comprises wind turbines and AC/DC converters. The AC/DC converter is responsible for converting the AC power generated by the wind turbine’s generator into DC power. It also ensures voltage compatibility between the DC bus and the generator, while achieving maximum power tracking.

2.3 Wind-solar complementary grid-connected control and inverter system

In the wind-solar complementary grid-connected control and inverter system, the control systems of both wind turbines and photovoltaic arrays are integrated. This integration allows for efficient power generation and facilitates grid connection. The system utilizes the DC/(AC)-DC-AC conversion function of the inverter to convert the generated power into a suitable form for grid connection.The core technology of the wind-solar complementary power supply system lies in the small-scale wind turbine.  The system flowchart is shown in Figure.

3.Technological Innovations

3.1 Solar power reduces reliance on grid electricity, emits no greenhouse gases, and aligns with sustainable development.

3.2 Off-grid systems are easy to install and require no power grids or cables.

3.3 Grid-connected systems use the grid as an energy storage device, allowing for power purchase during high demand and selling excess power. This eliminates the need for batteries, improves system reliability, reduces pollution, and lowers costs.

3.4 The grid-connected system adopts a distributed construction approach, supplying power locally and dispersing power generation. It is beneficial for enhancing the resilience of the power system against wars and disasters, improving load balancing in the power system, and reducing line losses.

4.Technical Reliability

The wind-solar complementary power supply system relies on electromagnetic and blade deformation speed limiting for wind power supply. It’s tested up to Wind Class 15 in a wind tunnel without safety concerns. Its technical reliability is mainly reflected in the following three aspects:

4.1 Complementary resources:

Wind energy and solar energy have complementary characteristics in terms of time and seasons, which improves the reliability of the power supply system.

4.2 Complementary technologies:

The wind-solar complementary power supply system uses batteries as energy storage components and employs the complementary combination of wind power and solar photovoltaic power to extend the lifespan of the batteries and enhance the reliability of the power supply system.

4.3 Complementary economics:

The wind-solar complementary power supply system is widely used in multiple fields, with lower construction costs and operating costs compared to traditional grid power supply.

5.Technological Applications

5.1 Applicable Fields of Technology

Wind-solar complementary power supply systems are used in various applications: port and navigation power supply, road and landscape lighting, video surveillance, off-grid power for islands, remote areas, oil drilling platforms, communication base stations, and government-promoted distributed solar power supply.

5.2 Technology Usage Conditions

Wind-solar complementary power supply systems are suitable for regions with an average annual wind speed of 4 m/s, abundant sunlight, and a total annual solar radiation exceeding 4,500 MJ.

6.Analysis of Technological Benefits

6.1 Economic Benefits

For off-grid wind-solar complementary power supply systems:
The construction of conventional power supply streetlights includes the construction of substations, procurement and laying of cables, and various civil engineering and labor costs. In contrast, wind-solar complementary off-grid power supply systems are easy to install and require no extensive cable laying projects. The cost is comparable, and the annual maintenance cost of conventional streetlights is calculated as 2% of the project cost, while wind-solar complementary off-grid power supply systems require no maintenance costs. A comparison of construction and maintenance costs between conventional streetlights and wind-solar complementary streetlights is shown in Table 1.

6.2 Energy-saving and Low-carbon Benefits

In China, 62 wind-solar off-grid systems (105W LED) will be added in 2023, saving 80110.2 KWH (26.44 tce/A). 89 grid-connected systems (120W LED) have been installed, saving 358,659 KWH (118.36 tce/A).

The costs of off-grid systems are similar to conventional streetlights, with no complex cable laying or maintenance expenses. Grid-connected systems have an investment of 2.7 million yuan, with annual subsidy, electricity cost savings, and benefits resulting in a payback period of around 6 years.

6.3 In terms of social benefits

wind-solar complementary power supply systems can save energy equivalent to 144.8 tce/a annually and reduce coal combustion emissions by 3.45 tons of sulfur dioxide, 1.04 tons of nitrogen oxides, and 376.48 tons of carbon dioxide.

 

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