Construction of a 230 kilovolt gas-insulated substation started Sunday at the site of Rey Power Plant in south Tehran as the first step to phase out the old station, head of the Thermal Power Plants Holding Company said.
Estimated useful life of an electricity plant is 20 years but the Rey station has operated for half a century.
“It started working with 40 gas units and generation capacity of 1,170 megawatts,” Mohsen Tarztalab was quoted as saying by the Energy Ministry news portal Paven.
“However, due to old age, wear and tear and failure of some units, only 20 gas units are operating and output has dropped to 500 MW,” he said.
The units that are still functioning have an efficiency rate of 20%. Because of high costs of repair and maintenance, construction of new units has started, Tarztalab said.
As per plans, a new combine-cycle power plant will be set up near the old one that will be phased out gradually.
Energy efficiency of a conventional thermal power station, considered salable energy produced as a percent of the heating value of the fuel consumed, is typically 33% to 48%.
Considering the heat produced by gas and steam turbines, their efficiency is limited and governed by the laws of thermodynamics. Combined-cycle systems, however, have higher levels.
The new plant will have two F-class gas units and a steam unit, with a total capacity of 1,070 MW.
Permits for the construction of the new power station with 60% efficiency have been issued and work will begin in the fall. It is estimated to be completed in three years and cost $16 million, Tarztalab said.
As per Energy Ministry rules, new power plant units must have efficiency rates of at least 58%.
Tehran has close to 4.7 million subscribers, 75% of which are households. On average 100,000 new customers join the bulging subscription list each year across the province that has grown in all four directions piling pressure on utilities, namely water, electricity and gas.
On average $22 million is spent annually to optimize, upgrade and expand the national power grid to meet demand that has been of the ascending order since forever.
Tarztalab said if rehabilitating the ageing plants is delayed maintenance costs will rise to the detriment of the highly subsidized energy sector and the treasury.
Plans to boost electricity output from the current 82,000 MW to 120,000 MW cannot be realized unless new power plants come on stream and old plants are either retired or renovated.
Pointing to TPPHC's role in meeting power demand, he said at least 85% of Iran's electricity needs are met by thermal power plants.
With installed capacity of 67 gigawatts, Iran ranks ninth in terms of global thermal power capacity.
