Background of Project:

Concern over the anthropogenic Greenhouse Gas Build-up in the atmosphere resulted in increased  interest  in  Renewable  Energy  Technology.  Due  to  its  rapidly  increasing
population and the urgent need for increasing the Production of  Electricity awareness in
The  Islamic  Republic  of  Iran, the renewable energy technology including Solar Energy
have gained momentum in the Iranian industrial sector.
The Islamic Republic Of Iran became keenly interested in the large-scale exploitation of
its  abundant solar resource, specifically by means of Concentrated Solar Power (CSP) technology.  The  principal rationale of this interest is the Iranian Government's strategic
goal  of  diversification  of  its  power  production  basis  and  the more efficient use and
prolongation of the country's oil and natural gas reserves.

The  consistent  interest  of The Islamic Republic of Iran in CSP is documented through
actions already initiated in the early 1990's.In 1992 the German Federal Minister for the
Environment,  Nature  Conservation  and  Nuclear  Safety  of  the  Federal  Republic  of
Germany and the Vice President of the Islamic Republic of Iran signed a "Memorandum
of Understanding Concerning Cooperation in the Field of the Environment" in Tehran.
To follow-up, Iranian and German experts organized the "First  German-Iranian Seminar
on Solar Thermal Power Plants" in September 1993 in Tehran,sponsored by the Energy
Ministry and the Electric Power Research Center.

In 1994, a  Joint  German-Iranian  Expert Group on Solar Thermal Power, sponsored by
the  German  Federal  Ministry  of  Environment  and  the  Iranian  Power  Development
Company (IPDC), elaborated a concept study for a 100mw Solar Thermal Plant. In 1996,
IPDC  contacted  GEF to investigate the possibility of support for the implementation of
such  a  major  solar  power  plant.  At  that time, GEF responded that a more thorough
feasibility analysis was needed as a basis for potential committment and grant support
to a project.

In  1997,  IPDC  contracted  the  Electric  Power  Research Center (now named NIROO
Research Institute), Pilkington Solar International (now named FLABEG Solar International)
and  Fichtner   (now  Fichtner  Solar) to execute a comprehensive feasibility study. NIROO
was  responsible  for  the  site selection, analysis of implementation strategy in the Iranian
electricity  sector  context,  and  analysis  of  local  manufacturing  capabilities,  FLABEG
Solar   for   the   solar  field lay-out  and   design,  economic  and  financial  analysis  and
structuring  of  project  financing.  Fichtner  Solar  took  responsibility  for the optimization
of  the combined cycle retrofit and optimal integration of the solar field technology into this
cycle.

The  best  places  for  installation  of Solar Thermal Power Plant in Iran have been selected
as  Esfahan,  Fars,  Kerman and Yazd due to high solar resources. Finally Yazd has been
selected for implementation of the first Solar Thermal Power Plant in Iran.

The location of the site is shown below:-

The  site  is  excellent  for  construction and operation of a solar field, approximately 9 km2
of  land  adjacent  to  the  future  power  complex has already been purchased by the Yazd
utility  company.  It  is adequate in size for almost 450mw of solar field capacity and
almost level, minimizing grading requirements. The entire high plateau of the Yazd region
is characterized by a high annual direct normal radiation of 2,511 kWh/m2, thus reducing
the required solar field size. Annual rainfall is low and wind speeds are moderate, the site
water resource, however, is limited. Due to this scarcity of water, a dry cooling system is
recommended for the steam turbine condensing cycle.

Preliminary activities have been started such as construction of infrastructure, extending
gas and water pipeline, water wells, complete weather station and extension of 400 kv
substation and so on. Meanwhile three older 64mw gas turbines (KWU V93.1) two from
Basat Power Station and one from Shiraz have been dismantled and relocated and have
been transferred to the Yazd site. About the same time a contract was signed by Alstom
GT to supply two gas turbine generator units with the characteristic PG 9171E (123.4 ISO
Condition). Alstom Company fulfilled their commitments and two gas turbine units have
been installed and the plant was put into operation on the 3rd May 2000.
At this stage we had to decide which configuration was the best solution for this power
plant. Two plant configurations are considered as a base for study as an appropriate
technical solution to meet the requirements of Iran:- one stand-alone Solar Rankine
Cycle and another Integrated Solar Combined Cycle System.
According to the feasability study and due to the two gas turbine generator units
already installed and technically adopted conventional combined cycle ISCCS short
description of Parabolic Trough Integrated Solar Combined Cycle System has been
selected for this technology.
Of course it is proven ISCCS has generated much interest because of its innovative way of reducing costs and increasing overall solar electricity efficiency.
At this stage Consultancy Services were awarded to Moshanir Power Engineering
Consultants on January 2001 for upgrading two gas turbine units to combined cycle
power plant and adding an aperture area of 366 240 m² to the solar field.
Moshanir scope of services include:
- Preparation of General & Technical Specification (Civil-Mechanical-Electrical-I&C-solar field)
- Preparation of Tender Document
- Preparation of Construction Bid Package
- Request for quotation
- Evaluate the quotation and negotiation EPC-Contract
- Award EPC-Contract
- Engineering
- Procurement
- Construction
- Commissioning
Summary of Work Process For Tender Document Production
Activites carried out by consortium
Fichtner - Pilkington - Matn
System Description:
Following Diagram will show the Process Flow Diagram of ISCCS:-

Fig 1. Schematic Flow Diagram ISCCS

The collector field consists of large field of single axis tracking parabolic trough solar collectors. The Solar Field which is modular in nature and comprising many parallel rows of solar collectors, which is aligned from North-South horizontal axis. Each solar collector has a linear parabolic shape reflector and will focus the direct sun-beam radiation in a linear receiver, which is located at the focus of parabola. The collector will track the sun from East-West all day and will ensure that the sun continuously focuses on the linear receiver. HTF fluid (Monsanto Therminol aromatic hydrocarbon biphenyl-diphenyl oxide) is heated and circulated in the linear receiver and will be transferred to the series of heat exchangers in order to generate steam. This is the general function of a solar field.

On the other hand combined cycle power plants fired by natural gases are a very cost-effective configuration due to excellent performance, cost and emission characteristics. The conventional CC plant consists of a combustion (Gas) Turbine (GT), Heat Recovery Steam Generator (HRSG) and Steam Turbine (ST) bottoming cycle. Hence the energy in the gases or other fossil fuels is used much more efficiently than in a GT alone. Modern cycles can achieve overall thermal-to-electric efficiencies of 55 or higher.

Integrated conventional combined cycle power plant and SEGS Solar Steam System will improve steam parameter and will permit the use of steam reheat turbine. Consequently the steam cycle efficiency increases by 40% and overall cycle easily by 50% fired by clean fuel natural gas combustion turbine. The integration combustion turbine is unchanged, Solar field will be used for steam generation and super heats the steam, which is then passed through high pressure turbine to low pressure turbine. Gas turbine waste heat will be used preferably to feed water preheating and steam generation. Since no superheating is required from solar field, evaporation temprature will be raised for high steam pressure. Elevated waste heat temperature will be used for attainment of high superheat temperature for high pressure steam. ISCCS will generate steam at 500 ? C and 100 bar .

There are four solar field operating modes:-

Operating mode No. 1:
When direct solar radiation is less than 200 W/m² and HTF temperature is less than 391 C, HTF, by-passing solar boiler will pump to the solar field. This will continue until HTF heat reaches the desired temperature.
Operating Mode No. 2 :
When direct solar radiation is more than 200 W/m² and HTF temperature is about 391 C and
HTF, passing solar field will enter solar boiler that consists of preheater, steam generator and
superheater.
Operating Mode No. 3 :
When direct solar radiation is more than 200 W/m² and HTF temperature is less than 391 C,
with regard to the variable-speed pump it is possible to reduce HTF flow rate until its temperature
reaches 391 C.

Operating Mode No. 4 :
In   this  case  if  the temperature of HTF is over 391 C, some of the collectors will be dismissed
from their focal position and unable to focus the direct insolation towards HCE, this will continue
until temperature of HTF reaches 391 C.


The upgrading to combined cycle (CC) adds 118mwe (from 212 to 331) net capacity and 964 GWh/a annual net electricity production. The further upgrading to ISCC will increase the net capacity by another 67mwe (from 331 to 398) and produce additional 156 GWh/a annual net electricity without additional fuel consumption. These conditions result in a solar contribution or solar share of 20% peak at full insolation and 5.5% annual average. The annual average heat rate is reduced from 11177 kJ/kWh for the gas turbines to 7175 kJ/kWh for the combined cycle plant and to 6784 kJ/kWh for the ISCC.
Solar energy is used more efficiently in the ISCC configuration than in a stand-alone steam Rankine cycle, such as the SEGS parabolic trough plants operating in California. The incremental solar electricity from the ISCC is 156 GWh/a compared to 131 GWh/a solar electricity from a Rankine cycle plant with the same size solar field.
A further benefit of integrating solar plants into the Iranian grid is the counteraction of the production losses from the gas turbines due to high daytime summer temperatures by the coincidence of high solar power production due to high solar input at those times. For example, from a night temperature of 10°C to a day temperature of 30°C the net electric power from the two gas turbines will decrease by 28mwe, whereas the ISCC will produce solar electricity at high insolation coinciding with the high daytime temperatures. The net result is an increased electricity output of 39mwe for the ISCC.
By upgrading the gas turbines to a combined cycle power plant, an investment of $115m will result in an additional annual net electricity generation of 964 GWhe/a from the high temperature exhaust gases which otherwise will be emitted to the atmosphere. By further upgrading with a solar field, an additional investment of $138m will result in an additional annual net electricity generation of 156 GWhe/a from solar energy.
By comparison, the investment required for a solar stand alone (SEGS) power plant of the same solar field would be $163m and producing 131 GWhe/a of electricity from solar energy.
Additional operation and maintenance requirements for the solar field have been taken into account in the economic analysis. Basically this consists of additional staffing of 14 personnel, and adequate spare parts stores for solar field maintenance.
Project organization and construction planning are discussed, but are not different from conventional power plant development and construction in most aspects. Solar field construction time requirements do not extend the normal construction schedule for a plant of this type.
National and regional employment impacts have been briefly examined. Solar power plant implementation can significantly increase national employment in several key sectors, including manufacturing, construction and plant O&M.
The environmental benefits of the solar addition are significant, notably in the avoidance of CO2 emissions and reducing global warming effects. The amount of CO2 emissions avoided by the ISCC plant over 25 years, compared to gas turbine operation and compared to combined cycle operation respectively, are approximately 17.7 million tons and 1.6 million tons. CO2 avoidance costs range from $3/ton to $31/ton for these two cases.
While a number of conclusions are discussed in this site, the overiding result is that upgrading the Yazd gas turbines to a combined cycle system with solar energy addition is warranted and encouraged.


Conclusions :
Upgrading of the two new gas turbines at the Yazd site to a Combined Cycle (CC) Power Plant by installing a waste heat recovery steam generator (WHRSG) and a steam turbine system is economically more attractive.
Further upgrading to an Integrated Solar Combined Cycle (ISCC) Power Plant by installing a larger waste heat recovery steam generator and a larger steam turbine system is the next step in economizing
However the upgrading to CC and then to ISCC must be planned and implemented from the beginning, that is, it cannot be carried out in two steps as the WHRSG and the steam turbine systems have to be sized so that both heat from the gas turbine exhaust and the heat from the solar field can be accommodated.
The cost of generating power from the ISCC is lower than the cost of generating power from the gas turbines.
If generation of electricity by means of solar technology in Iran is desired, then the integration with the new gas turbines in Yazd is the most attractive application. This is so because the Yazd site has already the complete infrastructure and superior site characteristics and solar insolation conditions.
Integration of a solar component into a Combined Cycle Power Plant costs less and produces more solar electricity than a stand-alone Solar Power Plant.
The high production losses of gas turbines and consequently of Combined Cycle Power Plants due to high ambient temperatures during the daytime in summer will be compensated from solar electricity production precisely at these times of high temperatures.
It is therefore recommended to upgrade the two new gas turbines at Yazd with a Waste Heat Recovery Steam Generator, a Steam Turbine and a Solar Field.
The advantages and the recommendations to integrate solar components into combined cycle power plants are applicable to all gas turbines in Iran. In particular within three years from now the next set of gas turbines are scheduled to be installed at Yazd and the same procedure could be applied.
It is further recommended that The Islamic Republic of Iran approach the Global Environmental Fund (GEF) in the future for discussions.