Duba 1 ISCC (Solar CSP + gas)


Low-cost Solar CSP in Saudi Arabia

The Duba 1 project in Tabuk province in the Kingdom of Saudi Arabia (KSA), on its northern Red Sea coast, is an ISCC (integrated solar combined cycle) project. It’s one of a small number of such projects worldwide to combine concentrated solar power (CSP) with an otherwise conventional power plant, reaping the benefits of an excellent local solar energy resource.

(NOTE: CSP is “concentrated solar power”, a family of technologies which collect solar energy from a wide area and focus it down onto smaller collectors to produce temperatures high enough to drive a thermal, spinning power generation cycle).

Developed and owned by the Saudi Electricity Company (SEC), the solar CSP technology used is parabolic trough with a solar power capacity of 43MW. This solar field is additional to a combined cycle gas power plant, bringing total plant capacity up to about 605 MW. The solar portion of the plant has been estimated to save the equivalent of 3 to 4 million barrels of fuel over the life of the project.

SEC, the Gulf region’s largest utility, will also be the electricity off-taker.

The plant is scheduled for completion and operation early in 2018.

 

 

“Firsts” in fuel and size

This is Saudi Arabia’s first integration of a solar field with a combined-cycle plant and the first ISCC plant to use “condensate” as a gas turbine fuel. Condesate is already used in some of Saudi Arabia’s other standalone gas plants. The availability of fuel was a major driver in the plant specification.

(NOTE: Condensate is a term describing mixed, low-density hydrocarbons, present within natural gas and able to be condensed to liquids by cooling under specific pressure conditions. Typical hydrocarbons include propane, butane, pentane and hexane).

In addition, Duba will be the largest integrated CSP capacity in the Arabian Gulf region: Algeria’s Hassi-R’mel plant integrates a 25 MW solar field while Egypt’s Kuraymat ISCC plant and Morocco’s Ain-Beni-Mathar station each incorporate 20 MW CSP units.

 

Plant details and contractors

 

i. Gas combined cycle and overall plant construction

GE is supplying the engineering equipment package for the combined-cycle plant, including two gas turbines, two heat recovery steam boilers and one steam turbine, plus associated condensers, boiler feed pumps and control systems. They are also providing a long-term service agreement. One gas turbine operates on condensate and the other on natural gas, with Arabian Super Light (ASL) crude oil as backup.

SEC tendered for the overall plant construction and balance of plant (the solar field and associated civil works, erection, commissioning and testing). This contract was awarded in late 2015. The contracts to build and operate the plant were reported to be $667 million.

At time of writing (October 2017), the plant is under construction through these EPC contract winners: Spanish EPC contractor Initec Energia and local partner Saudi Services for Electro Mechanic Works (SSEM).

 

ii. Solar CSP

In the combined cycle plant, the high temperature exhaust gases from the gas turbines are passed through the heat recovery steam boilers. High-pressure steam from these is then used in a second steam turbine generation cycle. It’s a well-proven technology that increases the overall generation efficiency (to over 50% in many cases). In ISCC installations such as this one, additional solar thermal energy is effectively injected into the heat recovery steam system of the conventional combined cycle plant. This boosts steam production and consequently electrical output.

In terms of the CSP part of the project, trough wasn’t the only technology considered for collecting solar heat. Fresnel, other trough and tower technology providers also expressed their interest in supplying the plant, including Novatec and Flagsol from Germany, TSK, Abengoa and Elecnor from Spain, and Solar Euromed from France. SEC communicated with various ISCC operators, before deciding to choose parabolic trough technology on the basis it would provide the maximum output at the lowest levelized cost of electricity (LCOE).

In the end, the solar collectors are supplied by Flabeg, a German supplier of high-tech glass and mirrors. They use technology developed by sbp sonne, another German firm, in collaboration with Fraunhofer Institute for Material Flow and Logistics (IML). The manufacturer claims that optical performance as measured by “intercept factor” (the ratio of power falling on the collectors to that falling on the concentrator) is between 97.5 and 99.2%.

The mirror field has a total aperture area of 170,000 m², with an aperture width of 7.5m (made from 48 parabolic mirrors), 8 solar collector elements (SCEs) per assembly (SCA) and a collector tube loop length of 800m. The total area requirement is about one square kilometre of land.

The choice of collector technology included adaptations to the specific site conditions, including a harsh corrosive coastal environment, plus its design suitability for the high wind-speeds found there. Field design considerations for a safe and efficient concentrator layout included measurement of the directional wind speed distribution, plus assessment of mirror breakage rates and equipment survival wind speeds.

Source: CSP Plaza

The solar collector tubes (carrying the synthetic oil in which the high-temperature solar energy is collected) are provided by Archimede Solar Energy, an Italian firm producing under license from ENEA (Italian National Research Agency for Renewable Energy).

There is no thermal energy storage component to the Duba 1 project.

A long-term service agreement involving the CSP system supplier throughout the plant’s lifecycle exists, with the aim of ensuring reliability and availability targets are met.

 

The Benefits of Integration: cost & experience

Duba 1 isn’t the only ISCC project in KSA: work is progressing simultaneously on the 1,390 MW Waad Al Shamal plant with 50 MW CSP.

Across both plants, SEC indicated that it had achieved a cost per installed kW for CSP of less than $1,600: less than half the lowest capital cost achieved until now on standalone CSP plants. The latter have ranged widely (from $3,500/kW to as high as $8,000/kW according to IRENA figures). In addition to low cost, the integrated approach allows SEC to gain construction and operation experience without taking significant risk.

 

Market Context 1: KSA, oil and gas and power demand

In the wider context, it’s important to note that the annual growth of power consumption in KSA is estimated to be around 7.5-8%, so in addition to regional needs there is a strong national requirement for new sources of electricity generation.

KSA is one of the few countries to burn oil as a substantial part of its generating mix, along with natural gas (the mix of primary energy for electricity generation is ~65% Oil, 27% Natural Gas and 8% waste heat from desalination).

With the stated increase in demand, unless alternative energy sources (and energy efficiencies) are adopted, the demand for fossil fuel for power generation could grow from about 3.4 million barrels per day (mbpd) in 2010 to well over 8 mbpd by 2030. In addition to climate and health concerns, this diversion of oil to the power sector also threatens to cut the Kingdom’s export revenues significantly.

KSA benefits from excellent solar resource: an average of 2,200 kWh of solar energy per square meter of land area every day. Direct normal incident radiation (DNI), which is the relevant measure for concentrated solar applications, is as high as 2,400 kWh per square meter in the Tabuk region.

 

Market Context 2: Electricity Access & The Grid

Grid interconnection to what is a developing region of KSA is limited, so the project is of high importance in meeting energy demand and supporting growth there (in the absence of an ability to import sufficient power from elsewhere).

Specific to the project, construction of the power plant also includes construction of a 380/132kV substation with protection, metering, control, communication, SCADA (system control and data acquisition), SAS (substation automation solutions) and civil works. Plus construction of 380kV underground cables to connect this substation. ABB won the right to design, supply and commission the substation under a contract worth $26 million.

As part of a wider grid strategy, SEC has also finalised the implementation and operation of a number of electric transmission and interconnection projects to link cities in the northern regions of KSA, at a total cost of US$1.47bn. These projects set a base for future electric links with the Duba 1 generation plant, in addition to a link with Al-Madinah region and an interconnection with the national grid of Egypt.

 

[Last updated: October 2017]

 

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