1. wind load
As the angle between the solar tracking bracket and the prevailing wind is constantly changing, the force on the bracket is also constantly changing. There may be components of impacting the support, lifting or pushing the support in these forces. In order to counteract these forces, there should be a large gap between the four sides of the module during installation, so that the wind load can be significantly reduced. Such as the hole in the kite body makes it difficult to tip over. The gap is actually part of the array, which increases the effective surface area and reduces wind loads.
2. Increase in power generation ratio
The increase in power generation and cost-effectiveness are the most controversial issues in the use of solar tracking devices. Many opinions have been put forward over the years, and calculations, simulations and proofs have been carried out based on computers.
The general expectation for the average annual increase in power generation is 30%. This ratio has taken into account the difference between the sun’s track in summer (>180°) and winter (<180°). In summer, the sunshine duration is longer, and the increase in power generation is expected to be higher than 30%, while in winter, the sunshine hours are shorter, and the increase in power generation is expected to be less than 30% (also depending on latitude and topography). Due to the above reasons, the application of solar tracking devices in solar pumping systems is particularly advantageous, because the photovoltaic array is connected to the load all day. In the battery charging system, the regulator may disconnect the load, which makes the solar tracking device waste. This of course also depends on the load curve throughout the year, and the peak load in summer will be more used for incremental power generation.
It must be noted that the radiation intensity is also affected by the air quality and the tilt angle of the sun. In the early morning and evening, we can use solar tracking devices to make the photovoltaic modules vertical, but limited by the radiation intensity, power generation is limited. Due to factors such as occlusion, terrain features will also affect the tracking system.
The only real way to check the cost-effectiveness of solar tracking devices is to design two systems with and without solar tracking devices, calculate the output and cost of the two systems and compare and evaluate them.
According to general experience: Compared with a fixed array, a system containing a solar tracking device must contain at least 8 photovoltaic modules in order to recover the cost of the solar tracking device.
[Example] The component costs are as follows:
8 solar tracking systems $4,000
Mounting frame for 8-component fixed array 1200 USD
175W (4.9A) photovoltaic module 1500 USD/pc
The actual cost of the solar tracking device = the cost of the solar tracking system-the cost of the installation frame = 4000-1200 = 2800 (USD).
Assuming that the daily average sunshine time is 5.5h, the output of 8 4.9A photovoltaic modules during the 5.5h solar peak time is 215.6A·h/d (fixed array). If the solar tracking device is used, the average annual power generation can be increased by 30%, so the output with the solar tracking device is 280.3A·h/d, and the increment is 64.7A·h/d, corresponding to 5.5h peak sunshine hours 64.7A·h, which is equivalent to an increase of 11.8A (64.7A·h/5.5h) in the current in the array. This 11.8A is equivalent to an additional 2.4 (11.8A/4.9A) photovoltaic modules. Therefore, an additional 2.4 photovoltaic modules are required to obtain the same output.
Assuming that it is not possible to purchase photovoltaic modules in whole numbers, each module is 1,500 US dollars, then the additional cost of purchasing 2.4 modules will be 3,600 US dollars (2.4 x 1500 US dollars).
Therefore, the cost of using a fixed array to generate 215.6A·h/d is:
10.4 modules $15,600
10 frames USD 1500
17100 USD in total
The cost of using the system with solar tracking device to generate 215.6Ah/d is:
8 components USD 12,000
8 solar tracking systems $4,000
USD 16,000 in total
The above did not consider the wire and hardware cost differences of the two different arrays.
As can be seen from the above example, solar tracking devices are cost-effective, and the larger the array, the more cost-effective. However, solar tracking devices usually can only contain 12 components at most, so the economy of the system varies with the number of components. In some cases, a fixed array may still be more economical.