|Egypt's 150 MW Kuraymat plant is among the first ISCC projects to come online Source: Green Prophet|
The completion of several integrated solar combined-cycle (ISCC) plants over the last two years suggests the hybrid technology could have a promising outlook.
Concentrated solar power (CSP) hybridisation or integrated solar combined cycle (ISCC) plants have been increasingly noticeable, with about ten plants around the globe coming online in the past couple of years, compared with just a handful prior to 2009.
The concept is to combine the environmental benefits of solar energy with the operational advantages of a conventional gas combined-cycle plant. The plants work by using solar energy to produce steam that augments the output of the heat recovery steam generator (HRSG) of a conventional combined-cycle plant, boosting electrical output. As non-solar power production equipment is already provided with the combined-cycle, the only additional cost is the solar field and related steam generation equipment. In many cases, existing conventional thermal power plant infrastructure including power transmission links to the grid can be used.
Paolo Frankl, head of the renewable energies division at the International Energy Agency (IEA), recently noted that fossil fuels have a role to play in renewable energy development – and especially CSP, which is complementary with fossil fuel systems.
Pricing and efficiency are, as always, key. But here, too, the outlook is positive. A study by SunLab found that ISCC plants can cut costs to $1.5/W and drive the cost of solar power down to below 8 US cents/kWh, while achieving efficiencies in the order of 67 per cent, which is ten points higher than a conventional combined-cycle plant.
Increasing the ratio of solar to conventional power is another important consideration. The ratio is often currently somewhere between 10 per cent and 20 per cent. But this looks set to climb as newer projects design in higher ratios. That said, some of the ratios for early proof-of-concept projects have been fairly low. Areva Solar's Australian Liddell project has just 3 MW of solar partnered with 2000 MW of conventional power, while its Kogan Creek project partners 44 MW peak (23 MW average) of solar with 750 MW of conventional power.
Kuraymat – the pioneer
The MENA (Middle East and North Africa) region is shaping up as a key testing ground with several ISCC plants recently completed, particularly in North Africa. In many ways North Africa is a strong match for ISCC. The climate is a natural fit for solar and lowering domestic demand for fossil fuels could boost exports, increase revenues, deepen ties with neighbouring countries, and improve the security of energy supply.
But getting ISCC plants off the drawing board has taken time – several years in many cases. One example of this is Kuraymat in Egypt. It was selected for World Bank funding way back in 1999 but only finally opened for business earlier this year.
Spain's Iberdrola was finally awarded the $220 million contract to build the plant by the Egyptian government's New Renewable Energy Authority (NREA) in September 2007 after an international public tendering process. Construction was then held up by various hitches until 2009, when it got underway on uninhabited desert land 95 km south of Cairo, in close proximity to the power grid.
The Kuraymat plant's energy performance is about 10 percentage points higher than that of most modern plants. It operates at night as a conventional combined-cycle gas power plant producing about 110 MW from natural gas. During the day it transforms the energy from a 1900 m2 solar thermal field into steam powered electricity, reaching 150 MW during peak hours.
Kuraymat has been criticised for deriving almost all its energy from gas, despite attracting $50 million of World Bank funding for its hybrid combination of renewable and fossil fuels. The plant has been seen as effectively entrenching fossil fuels as the energy of choice in Egypt rather than ushering in a completely new dawn for renewables.
Yazd ISCC power station in Iran faces similar criticism. This 478 MW ISCC installation in the desert features a solar thermal component of some 17 MW. The contractor for the $170 million project is the Iran Electricity Development Organisation with turbines supplied by Siemens and Alstom.
New developments in NorthWest Africa
While plants such as Kuraymat and Yazd are clearly demonstrating ISCC technology's potential, these hybrid plants could make their greatest contribution in the countries of the Maghreb.
Spanish multinational Abengoa has taken the lead in building ISCC plants in northwest Africa. The 470 MW Ain Beni Mathar plant in Morocco opened near the Algerian border in November 2010. The facility's combined-cycle is based on Alstom's GT13E2 gas turbine and the plant features a large array of 224 parabolic mirror collectors.
Financing comes from both the private and the public sectors. The Global Environment Facility provided a $43.2 million grant, with the World Bank as an implementing agency. This grant was complemented with loans from the African Development Bank, Spain's Instituto de Credito Official, and equity from the Moroccan state-owned utility Office National de l'Electricité (ONE).
Abengoa Solar and Teyma (Abengoa's construction company) collaborated with Abener in engineering, designing and building the plant under a turnkey contract with ONE. The EPC contractor was Abener Energia, which also operates the plant together with ONE.
Ain Beni Mathar uses parabolic trough collectors with a reflective surface of more than 180 000 m2 and a capacity of 22 MW. The solar plant currently produces 20 MW of solar-derived power. The conventional power plant portion comprises two 179.9 MW gas turbines in combined-cycle.
Further east, in Algeria, the Hassi R'Mel ISCC power plant began producing electricity in June 2011. It was developed by New Energy Algeria (NEAL), a joint venture between Algerian state energy companies Sonatrach and Sonelgaz, and the private agro-industrial firm Semouleries Industrielles de la Mitidja (SIM). NEAL also undertakes development of projects and initiates partnerships with countries such as Germany for the export of electricity.
The EPC contractors are Abener and Teyma and the 150 MW Hassi R'Mel project has been built alongside an existing Sonelgaz power station at Tilghemt in the country's largest natural gas field, Hassi R'Mel. The solar contribution to the total output is estimated at some 25 MW, which will be integrated with 130 MW capacity from a conventional combined-cycle setup.
The decision to develop hybrid plants rather than stand-alone CSP plants reflects the broader industry's evolution, according to Cédric Philibert, a senior analyst in the Renewable Energy Division at the IEA. "Hybrid plants in North Africa stem from the Global Environmental Facility's (GEF) efforts to support the then nascent CSP industry," he said.
The GEF is run by the World Bank and its objective was to support both developing countries and companies with the solar know-how to develop their capabilities.
A sunny future for ISCC in North Africa?
Yet ISCC's future development remains uncertain. Successfully implementing the technology requires a regulatory framework with clear permits and permitting processes, not to mention adequate access to networks with enough capacity.
North African countries have problems in all these areas. The region also lacks the legal and commercial infrastructure for the hybrid industry to really take off. Utility companies are state-owned so lack experience in signing 25- or 30-year contracts for long-term power purchase agreements (PPAs), which could provide an obstacle. North Africa also lacks region-wide subsidies or feed-in tariffs. Only Algeria offers a feed-in-tariff system, which is restricted to hybrid systems and excludes purely solar systems.
|eSolar's solar tower technology is now being applied to ISCC Source: eSolar|
Algerian renewables may also struggle to compete with the country's cheap oil and gas resources. The high cost of cables to transmit solar-generated electricity raises its costs about 25 per cent above those for power from natural gas – a considerable disadvantage in a country with huge natural gas reserves.
Sonatrach's current internal upheaval has exacerbated the challenges for ISCC plants, as does the energy sector's failure to attract the foreign investment that it clearly needs for its development. Another obstacle is that the size of the solar field is limited by the extra capacity in the existing power block.
Getting a utility to sign a PPA for solar electricity from a hybrid plant can be complicated. While the solar portion of the overall power output of the plant may attract favourable feed-in tariffs, the portion of electricity that counts as renewable energy cannot be measured by direct physical metering. A model-based approach to determine the solar contribution to ISCC power output is therefore required.
In many parts of the world, building an ISCC power plant would involve an independent developer co-ordinating the project with the owner of the coal or gas plant. Building these solar boosters is therefore limited to companies that own coal or gas plants.
That said, Algeria has set a goal of ISCC plants providing 5 per cent of national generating capacity by 2015, according to its national programme for the development of renewable energy: the Algerian Sustainable Energy Development Plan for 2020. The country has also had a feed-in tariff scheme in place since March 2004, offering elevated tariffs for renewable power production.
Exports could provide impetus for growth
Looking to the medium term, Algeria has ambitious plans to export electricity from CSP to Europe. NEAL is currently seeking approval for a project to build a 3000 km transmission line capable of supplying 800–1000 MW of solar hybrid energy to the European Union. Algeria's long-term goal is to export 6000 MW of solar generated power to Europe by 2020.
This drive to export electricity is linked to the Desertec Industrial Initiative (DII), which was launched under the auspices of the Club of Rome and other institutions in October 2009. DII seeks to develop renewable energy production in the desert regions of the Middle East and North Africa both for local use and for export to Europe. Founding members of the project include Abengoa Solar, ABB, Deutsche Bank, EON, RWE, Schott Solar, Siemens, Solar Millennium/MSM and others.
The initiative is aimed at meeting 15 per cent of Europe's energy needs, and a substantial part of Northern African and the Middle Eastern demand, through concentrating solar plants and other renewable sources of energy by 2050. DII is already collaborating with the Mediterranean Solar Plan, an initiative approved by the European Union in 2008 to promote large-scale solar power projects in North Africa. Santiago Seage, CEO of Abengoa Solar, expressed his satisfaction upon signing the agreement for the company to join this ambitious project, pointing out that Northern Africa and the Middle East offer tremendous solar energy potential both for their own use and for exporting.
Elsewhere in the Middle East, technologies such as ISCC could also stand to gain from national strategies to reduce the opportunity cost of burning fossil fuels. Kuwait, which has set an ambitious goal of deriving 10 per cent of its electricity from renewables by 2020, has shown an interest in developing ISCC technology. A planned project for Abdaliyah, southwest of Kuwait City, would lead to a 220 MW combined-cycle gas power plant with solar radiation generating another 60 MW.
Development potential in Latin America and China
While analyses of the development of ISCC technology tend to focus on the Middle East and North Africa, plenty of ISCC projects are taking place elsewhere.
In Mexico, Spain's Abengoa plans to bring a CSP solar field on line within the next two years at the Agua Prieta II power plant in the state of Sonora. The facility is being promoted by the Mexican Federal Electricity Commission (CFE) and supported by the GEF of the United Nations' Development Programme.
Abengoa will carry out the engineering, design and start-up of the solar-gas hybrid technology in the plant, which includes a 12 MW solar field of parabolic trough collectors. The second phase of the project will be completed with a combined-cycle plant that can produce up to 464.4 MW of power.
In China, Hanas New Energy Group is investing about $346 million into developing an ISCC trough solar power plant that it claims will have a thermal efficiency of around 80 per cent. Output from the plant in Gaoshawo in Ningxia autonomous region will be able to follow grid demand, making it more like a traditional thermal power plant, allowing for easier grid connection and management, according to Hanas.
In collaboration with North China Power Engineering and Siemens, Hanas began constructing the plant in October 2011. The 92.5 MW facility is due to operate from October 2013. If the plant proves a success then further projects in China are likely to follow.
GE, eSolar and MetCap target economies of scale
Solar booster projects may definitely prove a promising niche for CSP manufacturers. ISCC's economics are also increasingly compelling as the technological capacity to integrate solar-thermal technology with gas plants improves.
Areva, Alstom and Siemens have all made investments over the past two years, and each has a hybrid solar-gas plant offering. GE believes adding solar thermal technology to its natural gas plants will make them run more cheaply and efficiently. The firm has agreed to invest up to $40 million in eSolar, a California-based developer of large solar thermal power systems.
|Ain Beni Mathar integrated solar combined-cycle power plant Source:Dana Smillie/World Bank|
The investment follows a licensing agreement that GE struck with eSolar in June of this year that will see the two companies supplying technology that combines solar thermal and gas power systems globally, with the exception of the Indian and Chinese markets.
The partnership's first venture is the Dervish integrated renewables combined-cycle (IRCC) plant in Karaman, Turkey, which is scheduled to complete in 2015 and involves a link-up with MetCap Investments, a Turkish investor and power project developer. The Karaman plant will have a capacity of about 530 MW and outstanding efficiency, said Paul Browning, president and CEO – Thermal Products for GE Energy. "At MetCap's site conditions, we will achieve 69 per cent plant efficiency, with this technology providing the capability to deliver efficiency greater than 70 per cent at Gas Turbine World conditions."
Previous installations that integrate solar energy with natural gas powered turbines have used parabolic trough technology, in which curved mirrors focus heat onto Dewar tubes carrying a heat transfer fluid – usually oil – to produce steam for enhancing the plant's efficiency. GE's system, on the other hand, will focus sunlight on a central tower with a vast mirror display, heating the water inside the tower to 200 °C more than was previously possible.
This is one of several innovations that would distinguish the Dervish IRCC plant's design from other large-scale integrated solar combined cycle plants, such as the ISCC Kuraymat in Egypt. But even without the input of renewables, GE's Flex Efficiency system can achieve 61 per cent fuel efficiency on natural gas alone.
The GE plant is also unlike previous combined-cycle plants in that it incorporates more than one type of renewable energy. Although not part of the main integrated system, 50 MW of wind turbines will be connected and will kick in on days that are windy but not sunny. John van Scoter, president and CEO of eSolar, has described the Dervish plant as transformational.
"When you get to the scale of Dervish, then you really have economies of scale. I think it's a blueprint for the future," he said. "The key issue in Turkey is the price of gas [currently about €10/MBTU] and adding the solar price on to this makes sense."
Despite general financing difficulties due to global economic crisis, he also forecasts that the industry will continue to grow in 2012. "I would be incredibly surprised if we didn't have more involvement in 2012, especially with the opportunity to retrofit existing combined-cycle plants, and even coal plants, with solar," he said.
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