Hybrid CSP-PV gains create openings for 24-hour solar supply

Activity in hybrid CSP-PV projects is growing as developers integrate design advantages and operational synergies to offer lower-cost baseload power, CSP experts told New Energy Update.

Integrated CSP-PV plants can optimize solar resources in markets requiring night-time supply. (Image credit: Xijian)

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Last month, Spain's Acciona and Abengoa resumed construction of the 110 MW Cerro Dominador CSP plant after receiving a notice to proceed (NTP) from project owners.

The Cerro Dominador plant is a tower design with 17.5 hours of molten salt thermal storage capacity. Abengoa is acting as technology partner for the engineering and construction project. The plant will be joined with an operational 100 MW PV plant to form a 210 MW hybrid solar energy complex.

Interest in hybrid CSP-PV is growing as operators seek lower cost energy for longer dispatch periods. While PV plants offer lower costs for daytime power, battery costs remain too high to offer night-time PV dispatch.

Combined CSP-PV plants can provide 24-hour baseload power at a lower cost per MWh than stand-alone CSP or separate CSP and PV plants, market experts told New Energy Update. Additional capex requirements for hybrid plants are more than offset by the output gains gained from optimizing the solar resources, the experts said.

Hybrid CSP-PV concepts could lower the levelised cost of energy (LCOE) to around 40 to 80 euros/MWh ($45.5-$91.1/MWh), depending on site and local market conditions, Oliver Baudson, managing director at TSK-Flagsol, said.

“In terms of levelized cost of energy, we assume for CSP-PV hybrid improvements of up to 50% compared to CSP stand-alone,” Baudson said.

Long-term gains

The integration of CSP and PV technology helps to lower construction and operations costs on a per MWh basis.

At a fully-integrated CSP-PV plant, where CSP output is stored to dispatch overnight, capex savings can be made from smaller solar field requirements per MWh, Johana Trujillo, Solar Program Director at Mott MacDonald, told New Energy Update.

"In tower projects there may also be some savings in the receiver as it may be smaller,” she said.

For future projects, hybrid efficiency can be optimized by sizing the CSP storage capacity to minimize PV and CSP generation overlap, using daytime resources to heat the CSP storage medium, Fernando Gonzalez, CEO of the Cerro Dominador project company, said.

Hybrid projects also bring about efficiencies in terms of logistics and labor costs, in both construction and operations phases.

Operational costs can be optimized through integrated operations and maintenance (O&M) contracts for the CSP and PV plants, Trujillo noted.

"The labor can be shared, while only one warehouse, workshop and administration building will be required,” she said.

The cost of standalone CSP and hybrid plants will continue to fall as growing deployment experience reduces contingencies during the construction period, Gonzalez said.

"And as more plants are built, the availability of financing options increases, reducing the overall cost of capital and allowing for the projects to become more competitive," he said.

                  CSP levelized cost of energy, auction price trends

                                                         (Click image to enlarge)

Source: International Renewable Energy Agency (Irena), January 2018.

Emerging markets

Developing countries with strong solar resources remain the key growth markets for CSP and hybrid CSP-PV projects.

"Demand for electricity is growing in developing countries, so there’s greater interest for baseload power generation like CSP,” Bruce Anderson, CEO at 24-7 Solar, said.

Following ground-breaking stand-alone CSP projects, Morocco is helping to boost hybrid PV-CSP development through its Noor Midelt project.

Morocco has set a target of 52% of installed capacity from renewables by 2030 and has launched a request for proposals for two hybrid solar plants at Noor Midelt. The two plants will each have a gross CSP capacity of between 150 MW and 190 MW and include storage capacity. The plants will be built by different developers and technology can be parabolic trough or tower while the exact PV capacity must be defined by the bidder.

Five CSP consortia have pre-qualified for project, led by ACWA Power, France's EDF EN, Engie (formerly GDF Suez), Germany's Innogy and Japan's JGC.

According to Trujillo, the markets most suited to hybrid CSP-PV are those with peak demand after sunset and sufficient daytime demand to absorb the PV generation.

This point was underlined by Meryem Lakhssassi, Sustainable Development Officer at the Moroccan Agency for Sustainable Energy (Masen), when she gave an update on the Noor Midelt project in April.

"The main objective of the Moroccan energy strategy is to reach 52% of installed capacity from renewables...Given the fact that the peak hour in Morocco is after sunset, the energy storage was inevitable," Lakhssassi said.

Standardized models

Larger hybrid projects can gain from economies of scale and wider deployment of hybrid plants should generate further design efficiencies.

“Over time, standardized methods will get established... it can be expected that a degree of efficiency saving in the design phase, as well as later on in the testing and operating phases, will become evident,” Trujillo said.

Design innovations and a favorable development framework should see Morocco hit its lowest prices for the hybrid CSP-PV Noor Midelt project, Lakhssassi said in April.

Morocco’s CSP tariff prices have already dropped sharply, from 1.62 Dirhams per kWh ($189/MWh) for the Noor I plant, operational since 2015, to 1.36 Dirhams/kWh ($140/MWh) for Noor II, expected online by the end of this year.

Morocco has kept in place a CSP regulatory framework in which Masen assumes many development and financial risks. This framework allows developers to focus on optimizing project costs and should result in a lower tariff for Noor Midelt than on previous stand-alone CSP projects, Lakhssassi said.

"We hope [the tariff] will continue to decrease, that is the objective," she said.

By Beatrice Bedeschi