By Rikki Stancich

CSP Today: GDF Suez and Solar Power Group are developing a 5 MW CSP plant, which will supply superheated steam to the 150 MW Mejillones coal-fired plant in Chile. Is Solar Power Group looking to establish itself in the energy market by offering a hybrid solution?

Mauricio Rojas: For us, a logical step is to jump into the add-on and booster market, in which we provide solar steam to power plants that are already in production and have been already depreciated. In this way, the energy produced from the solar field is cheaper because you don’t have to bear the costs of the turbine, balance of plant, special piping, and other infrastructure required for a stand-alone system.

In short, it is possible to  take advantage of the existing infrastructure and at the same time increase the dispatchability of the solar energy. Simultaneously, you improve the performance of these fossil fuel power plants because you can produce the same amount of energy with less consumption of fuel.

On the other hand, as midday peak demand is due to the strength of the sun, such hybrid plants can better adapt to the energy demand over the day. The hybrid systems offer many advantages very attractive to the power producers.

From the technological point of view, we can generate steam at higher temperatures, fact that has a positive impact in the efficiency of the overall hybrid system. This as well makes easy the integration of solar steam into the thermodynamic cycle of the plant.

Of course, with time we will see demand for stand-alone plants in small sizes, say 30 – 50 MW. Further down the road,  when storage tech is available for direct steam generation, we may then see base load plants in the range of 100’s MW.

But we think that the add-on market is a very important part of this transition and it is a way in which the utilities can take enough confidence to jump into CSP, in a progressive way.

CSP Today: The concept of CSP hybrids has been criticized in the past for ‘greening’ fossil fuels. Would you argue that hybrid plants have an important place in a country’s energy mix?

Mauricio Rojas: It depends a lot of the regulatory frameworks in the countries - how they see their energy mix. It is not just a matter of producing renewable energy; it is also that existing plants are generating a lot of emissions. So it is not simply a question of producing X or Y amount of renewable energy, it is a question of:  “how are you going to reduce the net emissions you are creating by producing electricity?”

When it comes to actually lowering the emissions of existing plants, the only renewable energy that can help the utilities to achieve these goals is CSP because it actually can replace some of the fuel that otherwise would be burnt. CSP as a state-of-the-art approach to emissions reductions is something I envisage becoming a reality before the end of this decade.

CSP Today: How much fuel economy is achieved by adding a 5MW CSP plant to produce superheated steam?

Mauricio Rojas: We did carry out a study involving a 350MW coal fired plant using a 6MW solar add-on. From the total energy produced by the plant, roughly 1.5% was solar. This is not an impressive number, but in absolute terms about 20,000 tonnes of coal would be saved in one year. This means an increase of efficiency of 1% in the power plant.

CSP Today: The ratios for solar booster plants are generally very low. What is the rationale for this?

Mauricio Rojas:  If you retrofit an existing power plant, you can reach solar portions of up to 5% - you would seldom see something in the two digits. But, on the other hand if you develop a power plant with this concept from the outset, you could easily go to 30-40% in a hybrid combination.

When you are talking about a 500MW plant, where solar provides 10%, this is already 50MW power coming from the sun - already an important amount. In some time, the sizes that we see now in standalone solar power plants will easily be the size of an add-on for a mid-size coal power plant. Here, land efficiency is going to play a very important role, which is where Fresnel technology has an advantage over other CSP technologies.

CSP Today: It is often mentioned that CSP augmentation and CSP hybrid plants are good bridging technologies. In your view, will CSP transition to the mainstream power generation via augmentation and hybrid technologies as fossil fuels become scarce, or will stand alone CSP develop in its own right? 

Mauricio Rojas: Hybridisation is one of the ways to bring CSP more mainstream. It’s going to be a slow transition for classical power producers, which are tied into a well-established industry. This approach will give them the opportunity to easily explore the new possibilities of solar energy.

CSP Today: For energy importers tied into long-term purchase agreements, how attractive is the solar booster concept as a means of achieving fuel economies, and to what extent are these countries becoming target markets for CSP technology providers and developers?

Mauricio Rojas: In a country where this concept is relatively widespread, you are talking about a huge amount of savings in terms of primary energy and a very important increase in independency. If a country really embraces this kind of fuel saving policy it can have a serious impact.

Stand-alone power plants today are very expensive and for many countries, to have them is just not an option. So solar boosters, which can represent only 40% of the cost of a stand-alone power plant, are more attractive. 

From a policy point of view, the hybridization also presents advantages, as more kWh of electricity can be obtained per money unit invested as support, because solar electricity from hybrid systems is cheaper than the produced in stand-alone plants.  

CSP Today: Solar Power Group is getting in on the ground floor of a potentially huge market via the Mejillones augmentation project. What is the policy framework like in Chile, with regards to support for renewable energies?

Mauricio Rojas: Right now Chile has a very ambitious program to increase the capacity of its grid for the North part of the country. They have a high concentration of mining sites there and they need to provide the energy support for the growth of this activity over the next ten years.

On the other hand, Northern Chile has one of the richest solar resources in the world, so they can achieve very impressive numbers in terms of power received per meter squared - almost twice that of what we can here in the best European location. This particular combination is an opportunity that for sure will be embraced by the country.

CSP Today: What are the advantages of working with a utility like GDF Suez on this project?

Mauricio Rojas: Certainly it is a strong point to be working with a utility like GDF Suez, because it provides an extra level of credibility in that they are actually acquiring our technology. We are going forward together on this venture as partners, but they are also our customer. As such, they will provide proof that the integration of Fresnel systems into existing power plants is feasible.

But for GDF Suez this project also has special significance, given that they own many power plants in areas suitable for solar augmentation. With this particular project one of the objectives is to collect operative information – how the system is controlled, what the performance is like.

To respond to this article, please write to the editor: Rikki Stancich