Two new gas units will come on stream at Tehran’s Tarasht Power Plant, the oldest power station in Iran, in the summer, deputy for projects development at the Thermal Power Plants Holding Company said.
“A total of six new units are to be built and replace the old units of Tarasht Power Plant. The construction of the other four gas units is underway and will be completed in the fall,” Mohammad Ramezani was also quoted as saying by the Energy Ministry’s news service Paven.
“Tarasht Power Plant was established in the 1930s with four steam units and a wet cooling tower, with a nominal capacity of 50 megawatts,” he added.
At the time, the power plant met more than 50% of Tehran's electricity needs.
“Based on international standards, the average useful life of such plants is 25 years. This is while Tarasht Power Station is over 60 years old. However, due to its low efficiency [about 20%] and high water consumption [up to 3,000 cubic meters per day], TPPHC decided to decommission the aging station and build six gas units with a nominal capacity of 9.8 MW each with an efficiency of 46.3%,” Ramezani said.
The construction project has accelerated and at the same time worn-out units are being decommissioned.
Since last September, two steam units have been phased out and the wet cooling tower has also been demolished.
In addition to being outdated, another problem with Tarasht was that it had a wet cooling tower that is preferred in regions where water is plentiful, like the coastal regions.
In wet cooling towers, heat transfer is measured by a decline in the processing temperature and a corresponding increase in both the moisture content and the wet bulb temperature of the air passing through the cooling tower.
In areas like Tehran where access to water is limited, dry cooling techniques are used. As the name suggests, this relies on air as the medium of heat transfer, rather than evaporation from the condenser circuit. Dry cooling means minimal water loss is achieved.
When the facility opened over half a century ago, Tehran was not struggling with chronic water scarcity. But conditions have changed and the population has jumped from three million then to over 10 million now.
Conversion to Combined-Cycle Plant
The old power station was a simple cycle gas plant while the new one will be a combined-cycle one, equipped with F-class turbines that consume less gas and are more eco-friendly.
A combined-cycle power plant uses both gas and steam turbines to produce up to 50% more electricity from the same fuel than a traditional gas plant where waste heat from the gas turbine is sent to a nearby steam turbine to generate electricity.
Iran's long-term plans to boost electricity output from the current 85,000 MW to 120,000 MW cannot be realized, unless new power plants come on stream.
More than 80% of electricity output come from thermal plants that use fossil fuels.
Over two-thirds of Iran’s thermal power plants are owned and operated by private firms and generate almost 67% of the domestic thermal power.
With an installed capacity of 85 gigawatts, Iran ranks ninth in terms of thermal power capacity in the world.
The Energy Ministry is gradually phasing out inefficient power plants, expanding electricity infrastructure and acquiring modern technology. However, financial constraints have slowed the process.
Effective steps have been taken to convert conventional plants into combined-cycle units to improve efficiency and reduce pollution and costs.
Tehran has more than five million power subscribers, of which 75% are households. At least 100,000 new customers join the subscription list every year, which has grown at a regular pace and piled pressure on utilities, such as water, electricity and gas.
TPPHC oversees dozens of fossil fuel power plants with an installed capacity of over 71,000 MW, constituting the bulk of electricity demand.
On average, $22 million are spent annually to optimize, upgrade and expand the national power grid to meet demand that has always been of the ascending order.
If rehabilitating the aging plants is delayed, maintenance costs will rise to the detriment of the highly subsidized energy sector and the treasury.
Although necessary, repair and maintenance of aging power plants cannot improve their low efficiency as expected and there is a critical need for modernization.
