Two steam units of Tarasht Power Plant in Tehran have been decommissioned and it is likely that by the end of the current Iranian year (March 2023), the aging power station will be completely restored as the construction of new gas units is underway, the plant’s deputy for planning and engineering said.
“According to the plan, six new gas units, with a nominal capacity of 9.8 megawatts each, will replace the old steam units,” Amir Hossein Hassan Ahi was also quoted as saying by IRNA.
According to its initial design, the power plant had an efficiency of 26%, but as time passed by, the figure decreased to about 20% in recent years. However, with the renovation of the power plant, its efficiency will reach 50%,” he added.
Tarasht Power Plant was established in the 1930s with four steam units and a wet cooling tower, with a nominal capacity of 50 megawatts. 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 the power plant is over 60 years old.
In addition to being outdated, another problem with Tarasht was that it had a wet cooling tower that is preferred in regions where water is plentiful, like the coastal regions.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 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 implies minimal water loss.
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 3 million then to over 10 million at present.
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.
