Case: Telecom Transmission Line in Mongolia

Project title: Solar power system for trunk transmission of telecommunications network in Mongolia

Client: The Post and Telecommunication Authority of Mongolia

Naps Contact: Paavo Suuronen

Completion date: December 2000

Objective:

1. To find an economically attractive energy alternative
2. To supply power for repeater stations in difficult locations

Implementation:
A total of 25 telecommunication repeater stations were refurbished to use tailor-made solar electric systems instead of the old diesel generators (which were retained only for back-up use). Naps developed systems which operate autonomously and which require a maximum of two maintenance visits a year. Naps trained the local installation team, and supervised the installation and start-up. All this took only 12 weeks.

Site specific issues:
The stations, built on mountains where access is extremely difficult, form a 800-kilometre telecommunications backbone across the western half of the country. The average altitude of the sites is over 1800 metres. In the Mongolian highlands the wind speed can be up to 50 metres per second, and winters in this area can be quite harsh. The use of diesel generators did not seem economically justified, as the fuel consumption was 35040 litres per year for each station. Further, refuelling at the appropriate time was a problem, firstly, owing to the arduous journey involved in reaching the site location, and secondly, owing to the fact that Mongolia is completely dependent on imported oil products.

Average peak power per site is 542 watts.

Equipment and technical specifications:
The equipment at an average site comprises:

• Solar array 5720 Wp (about 100 modules)
• Panel centres and structures for the solar modules
• System control unit type NSCi, tailor-made for the project
• Battery bank type tubular plate

Conclusions:
Solar electricity has yielded significant savings in operating costs by reducing the need to transport fuel to the sites, minimising the need for maintenance, and prolonging the lifetime of the generators, which are now used only in a back-up capacity. The status of the energy system can easily be monitored and controlled from a control room, and as the system consumes much less fuel annually, these two factors have reduced operational costs by approximately 90%.