Abstract: paper for WWEC 2003
Subject 4.2/4.6
WIND ENERGY AS AN ALTERNATIVE TO SOLAR POWER IN A SOUTH AFRICAN TELECOMMUNICATIONS NETWORK.
ABSTRACT.
An extensive radio (WLL) based telecommunications network exists in rural areas of SA that are not served by grid power. Solar power has been used extensively to power base stations and repeater sites, with an installed base approaching 6 MW. Theft of solar panels from isolated sites has reached such proportions that it is becoming impossible to maintain networks. In the year 2000, some 7500 solar panels valued at $1500000 were removed from the network. Attempts at theft prevention have proved unsuccessful and alternate methods of providing energy are being investigated. The power required does not exceed 200 watts per site.
Up to now Wind has not been considered as viable alternative resource. Apart from the coastal areas, the wind resource in most areas of SA is low with average wind speeds of 4m/s and less. Wind is also a very unpredictable and poorly mapped resource. Previous attempts at using wind were also hindered by the lack of suitable wind generators on the local market.
Permanent magnet based generators in the 1Kw to 5Kw range have recently appeared on the local market. These produce maximum power at wind speeds of 10-12 m/S, well above the average available. Considering that the output of a 1kw unit at 4m/s is approximately 100 watts, and the cost is less than the cost of constructing a power route of 1km in length, the use of wind generators becomes a viable option for sites > 1km away from the grid.
Most radio stations are located on high sites, where benefit can be obtained from the wind enhancement factor, which could be as high as 200%. As generator outputs also vary as the cube of the wind velocity, gusty conditions can be effectively exploited.
Wind generators were erected at four sites subject to repeated solar theft and the performance monitored over a 6-month period, with the following aims;
1)Determine whether the generators would be subject to theft or vandalism
2)Determine whether the wind resource would be sufficient to provide the power needs of the site.
3)To validate the engineering assumptions made and establish the basis for designing future sites.
4)To investigate the potential of the wind resource at high sites and compare with average figures for the area obtained from the weather office.
Three of the four sites proved successful and the fourth is regarded as marginal due to very low wind resource.
This paper describes the project from initial engineering to final analysis of the field trial. The field trial has proved that using an innovative non-optimised engineering approach can result in an effective economic solution.
Author : MGJ Rycroft: Specialist : Network power : Telkom SA
Private bag X74 Pretoria 0001
Tel 012 322 0922
Fax 012 322 0922
Co: Authors
Neil Rabie: Specialist : Network Power : Telkom SA
Private bag X74 Pretoria 0001
Henry Pahl: Senior manager: Switching, routing and power: Telkom SA
Private bag X74 Pretoria 0001
PRESENTER PROFILE
MGJ RYCROFT
Graduated from Natal University in 1971 with the degree Bsc. Electrical Engineering . Appointed as a engineer in the then Dept of Posts and Telegraphs. Worked in various sections in Head Office such as Telematics, Telephone Switching, Microwave engineering etc. Studied further at Pretoria University for the Degree of Bing. (Hons) which was obtained in 1981.
In 1992 I was appointed as manager of the Power Section of head Office, where I was responsible for all functions relating to Telecommunications Power systems Including technology, planning, installation and maintenance. Responsible for initiating and running a major project to modernise the power systems in Telkom, which involved the change from vented batteries to sealed and from Thyristor rectifiers to switchmode types.
With the introduction of radio and other power dependant technologies into the rural network, I became responsible for the development and deployment of alternate energy systems for these networks. Largely responsible for the widespread use of Solar systems in the Telkom SA network.
Main interests at the moment are the use of wind power as an alternate to solar, the optimal use of network power management systems, and optimising battery lifecycle costs.