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Providing coverage of Alaska and northern Canada's oil and gas industry
July 2017

Vol. 22, No. 29 Week of July 16, 2017

Efficiency is key to new ML&P power plant

State-of-the-art gas-fired power facility has many features designed to reduce cost of electricity by minimizing fuel consumption

Alan Bailey

Petroleum News

Having gone into operation in January, Municipal Light & Power’s new Plant 2A power generation facility in north Anchorage is now in full use. The state-of-the-art, gas-fueled plant can produce electricity much more efficiently than the decades old equipment that it has replaced - it employs combined-cycle technology in which heat from two gas turbine generators drives a steam-turbine generator, thus making maximum use of the energy released from the natural gas that is burned in the gas turbines.

Efficiency systems

The plant has several other features designed for maximum efficiency, including a system for maintaining the temperature of the air entering the gas turbines at the level required for maximum turbine efficiency. In part, this capability derives from the location of the plant adjacent to Anchorage’s main water supply conduit from Eklutna Lake. Cold lake water can be used to cool the intake air in the summer, while excess heat from the turbines can heat the air in the winter. Gas compressors hooked into the facility can also up the pressure of the gas input, especially during the winter, to optimize the pressure of the gas feeding into the gas turbines.

“We have seen through the beginning of our operations of the plant that it’s actually more efficient than what we believed,” said Mark Johnston, ML&P general manager, during a media tour of the plant on July 7.

Although the plant is rated for 120 megawatts of power output, ML&P has been able to operate the plant up to 125 megawatts, Johnston said.

The plant also has modern systems for minimizing the output of air pollutants, including an anhydrous ammonia system for removing nitrogen oxides from the gas turbine exhaust. And the plant’s high efficiency significantly reduces the volumes of carbon monoxide and carbon dioxide emissions relative to the amount of electricity generated.

Reliability

A prime reason for building the new plant was to address reliability issues with ML&P’s old plants, which were experiencing mechanical problems after continuing to operate for many years beyond their original life expectancies, Johnston said. But, although the construction of Plant 2A came in under budget, the ultimate cost of some $306 million does have to be recovered via consumers’ electricity bills. However, in the long term, the substantial savings in natural gas consumption resulting from the new plant’s efficiency will result in electricity cost savings. ML&P estimates savings of about $8 million per year in gas fuel purchases, with the possibility of the intake air temperature control system resulting in an additional $2 million in fuel cost savings, Johnston said.

Johnston likened the building of the new plant to the need to purchase a new car when an old car experiences frequent breakdowns. In addition to the soaring costs of maintaining the old equipment, the new equipment is needed to assure continuing reliability. It is a question of ensuring that customers’ lights stay on and that electrical heating continues to operate, Johnston said.

The operation of a power pool recently agreed between ML&P, Chugach Electric Association and Matanuska Electricity Association will also play a critical role in the use of Plant 2A. The plant operates at maximum efficiency when working close to its maximum capability of 120 megawatts of output, Johnston explained. However, during periods of the day when electricity demand is low, the demand from ML&P’s customers drops below that 120 megawatt level. But, by pooling power supply and demand with the other Southcentral utilities, the plant can run continuously at full output, thus maximizing fuel consumption efficiency. Under the pooling arrangements, Plant 2A and another modern combined-cycle, gas-fired plant, the Southcentral Power Project in south Anchorage, jointly owned by ML&P and Chugach Electric, will continuously provide base load power. Other, less efficient plants will then accommodate the swings in power demand above that base load level.






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