New Concentrating Solar Power Storage Material From Yara

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Yara International is a Norway-based company focused on sustainable environmental and agricultural solutions. The company recently made an announcement about a breakthrough technology used in concentrated solar power. Below is an interview with Emilio Iglesias Sola, a Yara business manager.

What about your use of potassium calcium nitrate is new and unique?

This is the first time that potassium calcium nitrate has been used in the concentrated solar power (CSP) market, and therefore opens up many opportunities for utility-scale growth.

Calcium nitrate is not new; it has been used in other industries and application for years. What is unique is that our new potassium calcium nitrate grade – patent-pending – has been specifically developed to meet the performance demands of the solar thermal power industry. Our researchers identified a challenge related to heat storage using existing molten salts available in the market, and applied Yara’s chemistry expertise to overcome this obstacle.

At its core, this reflects what Yara does every day. With over 100 years of experience in nitrogen-based applications, we provide products and integrated solutions using nitrogen – one of the building blocks of life – and help make the world a better place by optimizing industrial processes and environmental compliance. For instance, our diesel exhaust fluid helps abate harmful nitrous oxides from heavy-duty trucks.

What practical advantages are there to using it and the way you are using it?

In addition to cost advantages, the new potassium calcium nitrate offers plant engineers and operators technical advantages:

First, the properties of potassium calcium nitrate bring down the melting point of the molten salt mix, a huge improvement for all CSP technology. For plants using parabolic trough technology with thermal oil and thermal storage, the current temperature range is 290ºC to 390ºC. Thermal oil’s maximum temperature is 400ºC.  The new ternary salts using potassium calcium nitrate have a wider Tª (131-560ºC).  The wider temperature range and significantly lower melting point means plants have more storage time and require less molten salt to function. In addition, the lower melting point helps owners prevent blockage caused by molten salt solidification, which can be very costly in terms of plant down-time and repairs.

We’ve also seen the market develop a trend to avoid thermal oil as a heat transfer fluid (HTF) for several reasons, including thermal oil is more expensive, not environmentally friendly and requires an (often expensive) heat exchanger between the oil and the molten salt. The broader temperature range of the new ternary salts using potassium calcium nitrate allows for new lower working temperatures, and provides a higher turbine yield when working at higher temperatures.

Finally, our new potassium calcium nitrate is much less corrosive than common calcium nitrate grades. It also contains fewer impurities than common grades of calcium nitrate. More pure and less corrosive, Yara’s synthetic molecule helps reduce corrosion of plant components, related maintenance costs and safety issues.

Your use of potassium calcium nitrate is said to be more cost effective, how much more cost effective is it and why?

The price of Yara’s new potassium calcium nitrate is more competitive than that of potassium and sodium nitrate, offering significant CAPEX reductions in the purchase of the nitrates during plant construction.  Not only is potassium calcium nitrate very competitively priced, but given the wider temperature range noted earlier, less salts need to be purchased overall.

As the world’s largest nitrates producer, our global scale and production efficiencies mean we can provide the product to our customers at an even lower rate than our competitors to anywhere in the world.

Based on size of the plant (which determines the volumes of molten salts required during construction) and the current price of potassium and sodium nitrate, we can estimate a wide range of total capital expense savings. Additionally, due to the potassium nitrate (KNO3) and sodium nitrate (NaNO3) price trends, we anticipate savings for customers using our potassium calcium nitrate will increase over the coming years.

It is these cost savings, along with operational expenses, that we believe will make solar thermal more profitable for plant operators and investors, significantly improving the commercial viability of CSP.

Is your new technology currently operating in CSP facilities, if so, where, and if not, where might it be employed soon?

We have advanced negotiations with several companies, although due to Non-Disclosure Agreements I am not at liberty to share more. That said, the product is ready for sale today and we anticipate the first plant running our proposal will come out of field tests in 2014.

In which parts of the world do you expect it to be used first and why?

The United States and Spain, the countries with the most advanced CSP development, will be the places where this technology is first implemented.

Going forward, we anticipate the next large area of CSP growth to come from the US for several reasons:

• First, the US has the potential to offer better yields than Spain. Land availability and better radiation locations will allow plant managers to develop larger, more-efficient CSP plants which will lower costs and produce better yields.
• Secondly, the US currently has a renewable energy pool policy, which is a good political and social environment to develop CSP plants.

How long can potassium calcium nitrate be used before its storage potential is exhausted?

Thermal storage using nitrates lasts the whole lifetime of the CSP plant, which is about 30 years.
 

 
Are there limits to how much you can produce?

As the world’s largest nitrates producer, Yara can produce more than enough potassium calcium nitrate to meet the needs of the solar thermal market. Although the volumes of molten salts needed for the CSP sector are set to surge, they remain only a fraction of Yara’s production capacity. Our global production platform and international supply chain can currently support the US and Spanish CSP markets, as well as future CSP markets in China, North Africa, India and Australia.

What is the future of concentrated solar power and what does this breakthrough development mean for the global solar power industry?

Two things have always plagued the utility-scale adoption of solar power: storage and cost. Concentrated solar power technology solved the first issue, by providing a way to store thermal energy and provide on-demand, reliable electricity from the sun, even after dark, when demand for electricity peaks. This allows CSP to be baseload, something PV and wind power cannot achieve in any scalable way at the moment. It also will enable CSP to achieve grid parity with its traditional gas, coal and nuclear counterparts.

The next generation of molten salts using Yara’s potassium calcium nitrate address the second and final barrier, making utility-scale CSP plants less costly to construct and more profitable for plant operators and investors – for the first time, CSP will be commercially viable.

How did Yara’s commitment to innovation lead to the identification of this new grade of CN, developed specially for heat storage and transfer applications?

Through ongoing R&D, we identified a new grade of potassium calcium nitrate with promising thermal properties, and developed it specifically for heat storage and transfer applications. We then tested the CSP application in partnership with Universidad Complutense de Madrid in Spain.

As noted earlier, Yara has over 100 years of experience in nitrogen-based applications. Ongoing R&D is an important part of our commitment to “shape” the industry, and as the market develops in the coming years, we will continue to follow this track.

Image Credit: Yara International