Among all types of photovoltaic power plants, those used for agricultural solar lighting and fishing solar lighting come with the highest construction costs. This stems from the considerable challenges these projects hold – pile foundation, construction difficulty and labor cost – in comparison to more ‘normal use’ photovoltaic power plants.

Recently, some of these complex projects have made use of optimized 500W+ 210mm high-power modules, helping reduce the overall cost of the power station and, even with rising module prices, the projects delivered acceptable profit levels.

Analysis of the main factors driving down costs

From a system perspective, changing low-power modules to high-power modules primarily affects the design. High power production reduces the number of modules required, thereby reducing the number of trackers and piles, the number of foundations, and the number of combiner boxes and cables, for the same installation capacity.

The table below illustrates an agricultural solar lighting project by the Hunan Electric Power Design Institute. Looking at the comparison between the three types of module on the market, the most important cost drivers are the trackers and pile foundations.

Table 1: Cost differences among various modules (data provided by Hunan Electric Power Design Institute)

Looking at the tracker

For a fixed tracker system, the cost of the trackers is related to the total supporting area and an increase in the total supporting area within a certain range reduces the cost of the trackers. Compared with the 166 modules, the 182 and 210 modules have a significant increase in supporting area, which drives down the total cost. When we compare the two modules with the same supporting area, widening the tracker not only reduces its cost but also increases the power of each pile foundation. This then reduces the foundation cost per W (assuming that the pile spacing is constant). Therefore, widening the trackers results in more BOS savings than lengthening them.

The figure above shows a comparison of a two-row vertical installation of 20 modules, which illustrates that the overall power and area of the 210 module array and the 182 module array are similar. However, due to the slimmer design of the 210 module, the tracker has been widened and the overall length is shorter. This means the total amount of steel for the tracker is minimized, helping reduce costs as much as possible.

Looking at the foundations

As mentioned previously, the key to driving down the cost of agricultural solar lighting and fishing solar lighting projects is the pile foundation, and the application of high-power modules can significantly save the cost of pile foundations. The following table lists the reasons for the differences in pile foundation costs for three comparative components and, due to the increased power of a single block of the two 500W+ modules, the number of pile foundations was significantly reduced. This helps keep costs down.

Table 2: Pile foundation cost differences of different products (data provided by Hunan Electric Power Design Institute)

In addition, as a module with low voltage, the 545W is able to accommodate a large string design of 36 modules. The slim design makes the length of the tracker per unit power area shorter which increases the utilization rate of the pile foundation, and in turn maximizes the possibility of cost savings in the pile foundation.

However, it is worth noting that the above-mentioned projects are calculated based on a 5m pile length. As the head of the Hunan Academy of Engineering Institute commented, the differences in system costs vary with project conditions. In some agricultural solar lighting projects, the prefabricated pipes are 12 meters long and under those circumstances, the cost differences of the pile foundation will be significant. In this type of project, using the 210 module pile foundation can save 0.127 yuan/W compared to the 166 module, and the overall system cost difference can reach 0.2 yuan/W or more.

Table 3: Cost differences for different pile foundation lengths

210 high-power module accelerate industrial applications

The Chief engineer of Hunan Yuan New Energy Ltd., Feng Zhuowen, said: “Projects with higher pile foundation and trackers costs, such as agricultural solar lighting and fishing solar lighting, can utilize high-power modules to a great extent. This will significantly reduce the amount of pile foundation needed, thereby driving down the overall cost and ultimately improving a project's profitability.                                                                                                                                                   

The two 500W+ products performed well in the cost comparison analysis, in a variety of situations tested by the design institute. The 545W module with the advanced 210 silicon wafer technology was seen to be more cost-effective by comparison to the 535W module.

With the gradual increase in production of the 210 mm high-power modules, an increasing number of projects have begun switching to the new technology in a bid to drive down the overall costs of power station. Processes associated with trackers and inverters supporting high-power modules are also accelerating, helping create a new round of innovation in photovoltaic product solutions.

Source: Pvmen