Technology

CSP Today speaks to Andrea Pedretti, CTO of Airlight Energy, about the company’s technological innovations, their project in Morocco and the importance of local content

Airlight Energy, established in 2007, has its roots in the civil engineering domain. Over the past five years Airlight Energy, led by Andrea Pedretti, has focused its attention on new innovations in CSP and CPV. Airlight Energy has developed a new parabolic trough system using pneumatic mirrors situated in an inflated enclosure supported by pre-fabricated concrete blocks.  This new technology will be put into action in the Ait Baha booster plant currently in construction in Morocco.

CSP Today: What has the development of the new Airlight Energy parabolic trough involved and what will this contribute to the CSP industry?

Basically, the innovation of our parabolic trough has involved a number of key aspects. Firstly the structure has changed. Instead of having a metallic structure, made from steel or aluminium, we have used pre-casted concrete. We have developed machines to create moulds in which the concrete structure can be produced. The key benefit of this is that the parabolic trough structures can be manufactured locally on CSP sites. We simply transport the mould to the site of the CSP plant under development, where the concrete structure can be set.

Secondly, we have drastically changed the mirrors in our parabolic troughs. Instead of using heavy glass or aluminium mirror structures we use thin aluminised polyester film foil, kept in place by pressurised air. This achieves a perfect shape along our parabolic trough.

Together these two innovations allow us to produce collectors that are much larger than those currently available. We have an optical aperture that is around 10m – almost double the span of existing troughs. The length per trough is 200m in one collector. The basic idea is that we have a few large pieces that are produced locally, rather than many small ones.

The third important innovation is the use of air as a heat transfer fluid instead of synthetic oil, DSG or molten salts. The advantage of air is that it is freely available, it has a higher temperature capacity of around 600 to 650°C and any industrial process that uses fossil fuels produces air as a by-product. We can take this hot air or smoke generated by the industrial processes and reheat it up to 500 to 600°C to produce steam for electricity.

Using air does however mean that we need to use pipes that are eight to ten times  larger than oil pipes (40-60cm in diameter), but we can handle this as our structure is much larger than regular parabolic troughs.

CSP Today: Is this the technology and strategy you are employing in the Ait Baha booster plant in Morocco?

Yes. We have integrated our solar field to a cement factory of Italcementi Group in Morocco. In the production of cement there is a lot of heat that is wasted. We are able to take this wasted heat and recover and reheat it to 600ºC. This heat can be used to produce steam and electricity (around 3MW thermal) which can be used in the cement factory itself. This is an important application which can pave the way towards developing a stand-alone plant in the future.

CSP Today: Do you see Morocco as a potential market to build a stand-alone plant?

Yes, they have the Ouarzazate complex project to build 500 MW of CSP plants by 2015, of which they have already assigned 150 MW. Next year the additional 350 MW will be allocated. We will participate in the bidding process and hope to get a 50 or 100 MW allocation to build a stand-alone plant in Morocco.

Morocco is ideal for us because we already have our production machines that are used in the moulding process for the Ait Baha project so in terms of logistics we don’t have to transport anything more to the country. We also have trained local labour and agreements with local companies.

CSP Today: When do you expect your current project to reach completion?

It will be completed by March 2013.

CSP Today: Asides from Morocco, are there other markets you are looking to move into?

Yes. Any standard CSP market with good DNI ratings is of interest to us. Presently we have a lot of contacts in different areas. North Africa is of great interest to us because it is relatively near. South America, Chile in particular, has a lot of mining activity that uses electricity and heat. Our technology could fit well with the extraction of minerals, allowing us to build a similar booster project to the one we are developing in Morocco.

CSP Today: In terms of storage materials, you are using a silica based gravel component. How effective is this storage system?

This system of storing heat has actually been in use since 1929.

We have improved this technology making a tank out of concrete (instead of steel) and it is not a cylinder but a truncated cone. We usually place the tank underground and in this way the side walls become excellent insulators.

The main storage material is gravel, which we can find on site meaning we don’t need to import any molten salts and so forth. This is inexpensive and uses local labour.

The idea is to have gravel storage in a pebbled bed around 30mm in silica, not calcium, because of temperature requirements. We let the hot air percolate at the top, heating the stones, whilst the lower part of the storage tank gets cold and draws in more heat. Basically we store the heat directly in the stones. When we need the energy, to make steam or something during the night or the morning we do the opposite, releasing the heat from the top, out the bottom until the storage tank has cooled and can be reheated. The heat can be released on demand and we are able to store around 7000 hours’ worth of energy per year.

CSP Today: What attracted you to establish a local company in Morocco?

Instead of building all the components in Europe and exporting them to Morocco, we have transferred a lot of our equipment used in the CSP manufacturing process to our branch in Morocco. This is favourably viewed by the local government because we provide local employment, develop skills and promote the growth of the Moroccan technology industry.   

CSP Today: Would you adopt a similar strategy in other emerging markets by developing a local company in each emerging market?

Yes I would think so. For example, if we had projects underway in Chile, then we would look into creating a local office in Chile to oversee the local production process.

We already have a company in the USA, which has patents and licensing. It is not active yet as we are waiting to complete the projects we have in Switzerland and Morocco. After this we will activate the USA company and start development in North and South America.

CSP Today: Are you looking at establishing your own plants, or would you be involved in supplying existing developers?

The main strategy is to approach local utilities, enter into an agreement with them to provide the technology and they will need together with local construction companies. We therefore will not take full ownership of the projects, but will work in conjunction with local utilities and developers in different markets.  

To comment on this article write to the editor, Jennifer Muirhead