Snow Removal Services for Solar Plants Gather Attention in Japan
In the 2017–2018 winter, record-setting snowfall was continually reported in prefectures from Shimane to Aomori along the Japan Sea. Roads were closed and railway services were stopped for many hours, making it impossible for the people isolated by the transportation shutdown to buy food and everyday goods for a long period.
Solar power plants were also affected by a variety of hazards. Power generation stopped due to piling of snow on the panels. Mounting systems and arrays (units of solar panels fixed to mounting systems) collapsed and panels were cracked due to snow accumulation exceeding the level estimated at the time of design.
Mega (large-scale) solar power plants in snowy regions are normally designed with some margin based on the maximum and average annual snow accumulation during a certain period in the past. The arrays and mounting bases are designed to withstand snow accumulation exceeding the estimated level to some extent.
However, power generation equipment designed with a certain margin could be damaged depending on the degree of the margin by “record-breaking snow accumulation,” which occurred frequently last winter on the Japan Sea side.
One of the effective measures against damage caused by snow accumulation is “snow removal” for solar power plants that are in operation. Some companies have actually begun to undertake snow removal operations from solar power plants. One of such services is that using earth-moving machines offered by Golden Leaf-Works of Koto-ku, Tokyo.
The company conventionally offered the service to areas around its base in Asahikawa City, Hokkaido, because solar power plants that require the service are concentrated in the central and eastern regions of Hokkaido.
Because of the record-breaking heavy snow on the Japan Sea side last winter, the company received a number of requests for snow removal from solar power plants in the northern part of the Tohoku region including Akita Prefecture, Aomori Prefecture and Iwate Prefecture.
They requested the service to reduce the decline in power generation amount and minimize safety risks such as solar panels cracking and mounting systems collapsing. Requests from solar power plants that place priority on safety are on the increase recently, according to the company.
Golden Leaf-Works is a venture company and has been offering services to solar power plants by using heavy machinery since 2015 (See related article). The company uses earth-moving machines such as bulldozers and hydraulic excavators (shovel cars) and replaces the attachments (components for operations) depending on the services, which include snow removal, grass cutting and solar panel cleaning.
For snow removal, snow is pushed out from under solar panels by using a bulldozer (Video 1). In the method incorporated for removal of snow from roads, snow is sucked from the snow collection port and is blown out about several meters away from the bulldozer.
When it is difficult to use heavy machinery due to narrow spaces between arrays, for example, manual-type snow blowers are sometimes used.However, the physical burden is high when snow in heavy snowfall regions is removed by manual-type snow blowers, and the use of such blowers is avoided if possible.
When snow removal is carried out by civil engineering companies, they generally use bulldozers and hydraulic excavators without making modifications. Snow on roads can be removed without any problem by using the machines as they are, because the infrastructure is developed assuming incorporation of such methods. However, solar power plants have many limitations regarding driving machines, snow removal operations and disposal of snow, and it is sometimes difficult to use the machines as they are.
According to Hideaki Mizobuchi, president of Golden Leaf-Works, the company is advantageous to others because it can realize snow removal and other operations suitable for solar power plants, which have many restrictions, by replacing machine attachments with suitable ones. The company also takes advantage of the knowhow of persons who have experience of snow removal with earth-moving machines in Hokkaido and other regions.
Snow directly below solar panels can be removed with earth-moving machines up to the area close to the mounting systems for example. Snow sliding down the panels accumulates on the ground below the panels, forming heaps, and snow in these areas needs to be removed more than snow in any other areas, because the heaps extend to the bottom of the panels.
The knowledge and knowhow on both operations using earth-moving machines and solar power generation equipment are required to remove snow under solar panels and near mounting systems. Only a small number of snow removal service providers can remove snow perfectly without damaging power generation equipment, according to the company.
Snow is blown to the ground below the arrays at the front, because snow accumulation in the area does not cause problems regarding both safety and power generation.
If the snow remains until spring, it is effective for cooling solar panels in the event of a sudden temperature rise. The power generation efficiency of crystalline silicon panels drops at high temperatures, and the power generation loss is reduced if temperature rise is controlled.
The company keeps heavy machinery in the base in Asahikawa City to offer snow removal services. The company owns five earth-moving machines called “Skid-Steer Loaders,” which are frequently used for the services. The machines are “259D” models manufactured by Caterpillar Inc of the US. Five additional Skid-Steer Loaders can be leased if necessary.
In the majority of the snow removal services provided by the company, operations were performed by going to the sites from Asahikawa City, responding to the requests for the services from solar power plants in Hokkaido after heavy snow accumulation, and the company was paid for services in each operation.
As for snow removal operations entrusted by solar power plants in the Tohoku region last winter, the requests were also made every time the services were needed.
For stabilization of the business, it is preferable for the company to undertake periodic snow removal operations. According to a trial calculation by the company, when the cost for snow removal is deducted from the amount of power sales increased by snow removal, the balance will be plus for many mega solar power plants. However, orders for periodic snow removal were not realized because such cases are rare in Japan.
Some power producers, however, began to consider periodic snow removal because the decline in power generation amount due to snow accumulation exceeds the amount estimated at the time of project planning in some cases, and to ensure safety because solar panels and mounting systems could be damaged by snow accumulation, according to the company.
For example, the company is entrusted with semi-periodic snow removal services by a solar power plant in Hokkaido. The operation is entrusted by a mega solar power plant in eastern Hokkaido, and the operations are performed by going to the plant from Asahikawa City.
Images from remote monitoring cameras at the mega solar power plant are checked daily not only by the power producer but also by Golden Leaf-Works.
According to the contract signed with the power producer, snow is removed when the height of accumulated snow exceeds a certain level. Even if the height of accumulated snow has yet to reach the stipulated height, snow is removed upon approval of the power producer when heavy snowfall is anticipated or snow is estimated to reach the bottom of panels due to snow accumulation exceeding the anticipated level based on the current state of snowfall.
Requests for snow removal are concentrated in the snowy season, and snow accumulated on this mega solar site is sometimes removed at night .
Workers are not stationed at night and operations are not carried out at night in nearly all the general solar power plants. Therefore, only a small number of solar power plants are equipped with lighting devices, excluding special cases. This mega solar power plant also has no lighting device.
For snow removal at night, fish-luring lights used for fishing are installed on the earth-moving machines to improve visibility.
The company will soon receive orders for services that can utilize its snow removal knowhow in Hokkaido, including the experience of operations at night, according to the company.
The mega solar power plant is in the Hokuriku region and features an output of several tens of MW. The company will begin to offer snow removal services to the plant in or after autumn 2018, when the plant starts to sell power.
The region where the mega solar power plant is located also had heavy snowfall. Many solar panels after installation were cracked by the weight of accumulated snow during the construction work.
Considering such situations, the power producer decided to remove snow periodically after the start of operation.
Snow will be removed to reduce the decline in power generation amount and to prevent damage to solar panels, which were also the purposes of the operations carried out last winter responding to the requests from solar power plants in the Tohoku region.
According to Golden Leaf-Works, a control building with an accommodation facility will be constructed on the site adjacent to the mega solar power plant, and 10 or more snow removal workers, as well as a person who cooks for the workers, will be stationed in the building for continuous snow removal in night and day shifts.
The accommodation facility was set as one of the preconditions because part of the road between the city and the mega solar power plant could be closed due to delays in snow removal by the local government.
Golden Leaf-Works plans to recruit snow removal workers in the Hokuriku region from farmers who leave Hokkaido to work in winter, utilizing its network in Hokkaido. If the farmers use the same machine repeatedly, they can carry out familiar operations for many years, which is advantageous to the company and attractive to the workers.
Snow will be removed from the top surfaces of panels as well as the ground below solar panels at this mega solar power plant. The company plans to use non-contact snow blowers for removal of snow from the top surfaces of panels. The company plans to use machines with a function to blow off snow from panels without contacting them.
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