South Africa's first green-fuel mother station came into operation, in December 2009, in preparation for the showcasing of the green transport-technology options during the 2010 FIFA World cup.

The compressed natural gas (CNG) station is operated by energy company Virtual Gas Network, a division of CNG Holdings and CNG Technology. The mother station consists of two operating units. The first is a facility whereby CNG is distributed to large consumers as an alternative energy source. The second is a test re-fuelling facility, using two CNG dispensers that will be available to fill up buses, local delivery vehicles, cars, taxis and fork-lift trucks on CNG before the 2010 FIFA World Cup.

The test vehicles will be used by commercial businesses and operators in the area and will allow valuable data collection by CNG technologies and the South African National Energy Research Institute (Saneri).

"CNG Technologies has worked closely with the Saneri to establish various size filling stations that will be used to service various sectors in the market place, from a 20 vehicle in-house filling points to over 100 vehicles commercial filling stations. This is in a bid to introduce CNG technology into the South African market, by initially focusing on fleet operators," says CNG Technologies sales and marketing director Charles Jordão.

Saneri conducted an extensive study into the operation of public transport on CNG, with findings indicating that CNG is the only viable alternative fuel source readily available for immediate implementation in South Africa. Four companies were short-listed to do a full investigation and feasibility study on establishing a CNG refuelling station to service a minimum of 100 buses and 100 taxis.

CNG holdings was awarded the tender, in October 2008, and completed the feasibility study in March 2009. Jordão reports that the results of the study indicated that CNG is an economical alternative to fuel, and natural gas vehicles (NGV) are an extremely viable option.

The demonstration station is sized to refuel 100 buses, as well as 100 vehicles a day with CNG refuelling. One of the main aims is to establish a petrol/diesel conversion workshop that will refuel demo cars and conduct research related to performance assessments and emissions.

The mother station, located south of Johannesburg, is connected to an existing gas pipeline. Natural gas is compressed to 250 bar and stored in specialised modules, which are placed on platforms especially designed for safe and efficient module refilling and exchange. On arrival, the transport trailer exchanges the empty modules, brought from the consumption point, for ready filled modules. Jordão. explains that specially designed machines on the trailer reduce module loading and unloading times using the highest safety standards.

The modules are transported by road to a daughter station at the customer's site, where it is decompressed and regulated into their network. The regulating plants have a maximum capacity of 10 000 m3/h.

"The whole process is continuously monitored by a computer-based supervisory control and data acquisition system, which ensures seamless operation, relaying to the mother station exactly how much gas the customer has and when it needs more gas," he says.

Jordão points out that CNG is undoubtedly the fuel of the future as it can be used in a wide range of applications, such as heating, cooling, power generation, fuels for vehicles and furnaces. It can also be supplied to industrial, commercial and domestic consumers.

"Once the project is up and running, we aim to set up other stations, in and around Gauteng, so that the general public can start filling up. In the long term, we would like to have a national roll-out plan whereby not only piped gas, which is supplied from Mozambique, will be the source of natural gas, but other sources will be used as well, such as coal-bed natural gas. The mother station means that CNG will now be more accessible to everyone and not only the select few on the pipeline network," he says.

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