The power plants that can relocate20 August 1998
Flexibility is an increasingly key element in the electricity supply industry, and power barges can fulfil this demand. There are growing opportunities for a power supply that can be installed swiftly, and moved to alternative sites. An example of the flexibility to be found comes from the Philippines, and the Victoria 2 barge, originally destined for National Steel Corporation.
One simple fact summarises the potential market for power barges: that fact is that over 75 per cent of the world's population live within 50 miles of the sea. This represents a massive potential market. Power plants that can be built and moved to any spot in the world in such close proximity with three quarters of the world's population would seem to have great potential.
The ability to relocate a power plant also has obvious advantages. This is especially well-demonstrated in the case of the Victoria 2 barge. This 120 MWe plant was constructed by Sabah Shipyard, intended for National Steel of the Philippines. This was completed, but the contract was not finished. As a result, a new buyer was sought for the power barge. A spokesman for Sabah Shipyard has indicated that a new buyer has been found for this barge. This transaction is, at the time of going to press, in progress.
The Victoria 2 power barge consists of one Westinghouse W501D5A 'Econopac' gas turbine generator package, capable of generating 120 MWe at 60 Hz, 13.8 kV at ISO conditions.
The gas turbine is equipped for distillate and naphtha firing, but it also has a gas distribution ring fitted, so future conversion to natural gas or dual firing should present no major problems. The majority of equipment on board was supplied by Westinghouse, with the main 13.8/138 kV step-up transformer supplied by Hyundai.
The barge was originally completed in 1996, having been built to NKK (Nippon Kaiji Kyokai) Classification and complying with all applicable requirements of the local regulatory bodies for the service intended.
The barge has the following principal dimensions:
Overall length - 82 metres
Beam - 26 metres
Depth - 3.7 metres
Draught - 1.8 metres
The barge was provisionally registered under the Belize flag on 19 April, 1996. It had been originally designed for an IPP contract with the National Steel Corporation in the Philippines, but that contract was terminated, and work ceased on the barge in early 1997. Since then, the barge has been in a laid-up condition, and maintained by Sabah Shipyard's engineers.
The equipment installed on the barge consists principally of the following:Gas turbine and enclosure Generator and enclosure Starting motor (4160 V, 60 Hz) Air filter housing Mechanical package Pipe rack Electrical package Generators circuit breaker (SF6) Line-side cubicle and AVR ISO phase bus duct from circuit breaker to step-up transformer Step-up transformer (13.8/138 kV) 2 x auxiliary transformers (13 800/4160/480) 'Amp-guard' switchboard for auxiliary high voltage systems Fuel treatment module Compressor water-wash module Rotor air fin fan air cooler Lubricating oil fin fan cooler
According to a valuation carried out by Combustion, Energy and Steam Specialists (CESS), there is about 4-6 weeks work required to bring the plant from mobilisation to reach final commissioning.
One of the major advantages offered by power barges during the construction phase is fact that the construction takes place at shipyards. As a result, construction is very much easier. Skilled local labour is readily available, as is equipment such as heavy cranes.
This makes construction both more reliable and controlled, as well as cheaper. Risk factors are reduced.
In addition, because the barge itself is mobile, there is a reduced need to transport heavy pieces of equipment to site over inhospitable terrain. The equipment can be transported to the shipyard, which will have good transportation infrastructure.
Power barges provide greater security for lenders. Because these plants are mobile, if a problem arises with finance, the assets can be repossessed. This is vividly demonstrated by the National Steel project, in which the plant is being offered for sale to another potential purchaser, after 99 per cent completion of the construction.
Power barges have been described as being ideal for leasing. They can be used to provide solutions to temporary requirements in remote areas.
In general, there has been a lot of interest in leasing plant, but not a lot of firm leasing orders. A spokesman for Westinghouse said that power barges were a good prospect for developing areas.
An example of this is Ghana. A contract for 140 MWe of power, based on three simple cycle machines, was signed between Westinghouse and Ghana National Petroleum. The contract is part of a large project to develop a harbour, shore facilities, offshore gas and oil production, and transmission and distribution systems, in addition to the power barge. The US Maritime Administration has agreed to provide financial assistance for the power barge. The unit will be powered by natural gas from the Tano field.
In addition, the reserve level of power in the USA is declining, and has fallen from about 25 per cent to ten per cent. As a result, there may be growing opportunities for leasing solutions in the USA.
Because of the ability of the power barge to change location, the plant has to be able to accommodate a wide range of fuel. There are, for example, many places where the planned fuel is naphtha. This leads to a requirement for on-site water purification systems.
Reliability and availability
Because they use proven technology, the availability and reliability figures for operating power barges tend to be very high.
For example, Van der Horst and Wärtsilä NSD claim that Dura I, a power barge located in the Philippines, has an average of 98.6 per cent overall reliability and 95.8 per cent availability. Westinghouse claims availability and reliability figures typically about 99 per cent.
Will barges take off?
There appear to be many advantages to power barges. However, the actual demand for power barges has not yet taken off.
The initial cost per kW of simple cycle plant is higher than that of a land-based plant. According to Westinghouse, this is not the case for a combined cycle plant, with land and barge-mounted plants having the same cost per kW.
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