LED Lights Used Against Crows at 2MW Solar Plant in Shiga
"Lake Biwa Marriott Hotel" is a resort hotel located near the south end of Lake Biwa in northern Moriyama City, Shiga Prefecture, Japan (Fig. 1). The lakeside hotel attracts people with the beautiful reflection of mountains on the lake and the abundant surrounding nature.
Located next to this hotel is the "Mori Trust Energy Park Lake Biwa," a mega- (large-scale) solar power plant with a solar panel capacity of about 2MW and a PV inverter capacity of 1.990MW (Fig. 2). Four years have passed since this power plant began operation in December 2014.
The Mori Trust Group also owns land around the hotel and leveraged many of the unused areas in it as the mega-solar site. The power producer is Mori Trust Co Ltd.
Mori Trust developed the "Mori Trust Energy Park Izumizaki" with a total output of 10MW at another location before constructing this solar plant.
Along with the efficient use of energy, the utilization of renewable energy is a major challenge for the Mori Trust Group even in its mainstay urban building-related business. The group is proactively adopting an independent system that combines solar power generation and batteries in the buildings it has developed and operates in Tokyo and other urban areas.
When using solar power generation in such urban buildings, the Mori Trust Group has made the best use of the experience and knowledge it has accumulated in mega-solar development and operation.
Inspections entrusted to hotel
Kinden Corp provides engineering, procurement and construction (EPC) services at both mega-solar power plants next to Lake Biwa Marriott Hotel and on a former golf course in Izumizaki. PV inverters manufactured by Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC) were adopted at both sites.
The mega-solar plant site of Lake Biwa Marriott Hotel is near the lake and is surrounded by rice and vegetable fields. These sites were beneficial in limiting construction costs because they were originally flat and required no full-fledged land reclamation. Mori Trust reportedly needed to do almost nothing apart from land leveling and weeding when it developed the site.
Given the badly drained ground, however, drainage measures had to be considered. There were originally reservoirs at multiple locations inside and outside the plant site. In order to use these reservoirs more effectively, new drainage ditches were dug so rainwater could be drained quickly and discharged into these reservoirs (Fig. 3).
Even so, the site sometimes gets muddy in some areas especially on the day after rain. Accordingly, the company contrived a way to keep feet dry, placing concrete blocks and bricks like steppingstones in the areas that easily get muddy such as between arrays where people frequently walk for inspections and patrols (Fig. 4).
The Mori Trust Group operates and maintains (O&M) the plant after it started operation. One of the group's characteristics is its extensive experience in building operation and management. According to Mori Trust, solar power plants are relatively easy to manage among the group facilities thanks to O&M that leverages this characteristic.
As for daily duties, the Mori Trust Group has established a structure to implement frequent patrols, requesting a security company to rush to the site when something goes wrong and entrusting daily patrols to the hotel. This was also meant as a safeguard against cable thefts from the solar plant. Such thefts have happened continuously in the Kinki region.
What has been entrusted to the hotel includes weeding. Although the solar panel areas are covered by crushed stones (Fig. 5), weeds have rooted and easily grow in some areas. The hotel cuts the grass in such areas.
The Mori Trust Group also applies the same O&M method that utilizes its resources to the mega-solar plant on a former golf course in Izumizaki.
Flash lights in patterns to keep crows away
What the group had not anticipated during operation was that the cover glass of solar panels was occasionally broken. This seems to be attributed to "stone dropping" by crows (Fig. 6). The damage is about five panels per year at the most.
There are not only rice and vegetable fields but also forests and mountains around the mega-solar plant. A number of black kites and crows live there, constantly flying around the mega-solar plant (Fig. 7). When I visited the site for an interview, crows were resting on the arrays as well.
Crows not only leave their droppings on panels but also sometimes pick up stones and drop them onto solar panels while flying. Many mega-solar plants suffer from cover glass broken by crows in this manner.
Mori Trust immediately replaces any panel as soon as its cover glass is found broken. Many panels continue to generate power as much as before even after the cover glass is broken; however, broken cover glass might remotely cause cells (power generation elements) to get damaged and sparks to be generated. Focusing on such safety reasons, Mori Trust replaces the panels in question as soon as possible.
With a view to preventing damage from stone dropping, Mori Trust added a measure against crows inside the power plant site. The company attached units to the arrays that emit light up in the air that crows dislike (Fig. 8). To verify their effect, the units were set up through about half the site.
The adopted units are the "Bird Bee Flash" manufactured by Toshin Electric Co Ltd (Yodogawa-ku, Osaka City) (See related article).
These LED lights are set up in high positions on the arrays. During the day, the unit regularly emits light into the air above the arrays in various random patterns that crows dislike. This device was originally developed for mounting on utility poles and preventing crows from nesting there.
This device is embedded with a solar panel and requires no dedicated external power supply. As it is small and light, it can easily be attached in a small space on the corner of a mounting system.
After setting up these devices, the number of solar panels whose cover glass got broken by stone dropping decreased. However, as the number of broken cover glasses has also decreased in the area without these LED devices, it is difficult to determine the effect of these devices.