Interview by Rikki Stancich, Editor

Innovation doesn’t sleep – and neither, it seems, does Sky Fuel’s CTO, Randy Gee. For three decades Mr Gee has continued to push the boundaries of CSP technology and today, his energy and inspiration show no signs of diminishing.

Having designed parabolic trough collectors for Solargenix’s (now Acciona) 64 MW Nevada Solar One plant (commissioned in 2007), Mr Gee went on to co-found CSP technology OEM Sky Fuel; as well as ReflecTech, Inc, which supplies high reflectance films for heliostats, parabolic troughs and photovoltaic concentrators (now part of SkyFuel); and Industrial Solar Technology Corp. (IST) a leading manufacturer of parabolic trough solar collector systems, which is now part of Abengoa Solar.

In this week’s edition of CSP Today, Randy Gee explains how Sky Fuel’s latest R&D project to develop a ‘colossal parabolic trough’, with the support of the US National Renewable Energy Laboratory, will deliver the much needed efficiency leap that will make CSP a competitive alternative energy option.

CSP Today: What dimensions can we expect to see in the new trough design?

Randy Gee: We are still designing the collector size, but we anticipate that it will be in the range of 8 – 9 metres in aperture width), around 150 metres in length,  so the overall collector aperture is about twice the area of the current SkyTrough.

The current design approach is based on a receiver absorber diameter of 80mm – the same as the 6 metre SkyTrough. With this receiver and a significantly bigger aperture, we will be able to achieve concentration ratios higher than has ever been achieved before for parabolic troughs.

CSP Today: What temperature is the trough being designed to operate at?

Randy Gee: The new trough will achieve 500° C top output – so an average of 450° C – which is 100°C higher than the current design of other trough technologies. 500° C is getting up there and brings significant benefits – for the power block, and even more so for thermal storage, where large cost savings will result from the reduced  thermal mass.

The collector is being designed for integration with many heat transfer fluids (such as oil and molten salt) and thermal storage solutions.

CSP Today: How will the scaled up trough impact factors such as cost, procurement, and installation?

Randy Gee: The main point of going bigger and increasing the concentration ratio is to operate at a higher temperature and simultaneously reduce the collector cost. By scaling up we will achieve a 25% reduction in installed solar collector cost. This is a solid achievable figure, not just a simple goal of ours.

We all know that the receiver is a big part of the cost equation – it accounts for about a third of the total. When we increase the concentration ratio, the relative cost of the receiver component goes down.

We have to scale up the reflectors, but by using a reduced number of the same size receiver tubes, we generate a significant cost saving. When you add this advantage to the other economies of larger, highly-accurate concentrators, and the higher operating temperature with the advantage it creates for thermal storage, the net impact is big.

CSP Today: Will SkyFuel be using off-the-shelf receivers, or are you designing receivers in-house?

Randy Gee: We are looking at all the standard receiver sizes, and will evaluate all of these. But we have no motivation to redesign the receiver – we can use existing off-the-shelf products with the increased reflector aperture.

At the end of the day, cost reduction is really underpinning where we are headed. Personally, I have designed parabolic troughs for several decades and I can honestly say that this is the biggest improvement in trough technology we’ve seen in years.

CSP Today: The SkyTrough has yet to be commercially deployed, yet you are already launching into developing the next design phase. What is the rationale for this?

Randy Gee: With the SkyTrough, we have carried out the R&D, verification and field testing. Now we are ready to deploy the technology in large-scale projects, and we are establishing manufacturing capabilities in anticipation of big orders over the next 12 months.

Because of the long development cycle (engineering, testing, validation and field demonstration) we can’t sit around and be forever satisfied with the existing SkyTrough – we need to move on with new advancements and designs.

It is important for us, for the financial community, and for the world at large to see that parabolic trough costs are coming down; otherwise people will think that trough technology is static, rather than downward moving on price.

CSP Today: Is increasing component size a trend that is likely to continue?

Randy Gee: The trend toward larger collectors is clear – this is where everyone is heading.

The other key trend is the ability to use more precise optical reflectors – more so than mirrors – which is key to achieving higher concentration ratios. So, we’ll likely see higher concentration collectors, with better optics than we have seen in the past.

CSP Today: Are alternative reflectors such as ReflecTech, and aluminium reflectors, likely to gain significant market share in coming years – and will glass be able to compete with alternative reflectors in the future?

Randy Gee: We’ll see – I think the level of competition is very good. Ultimately the company that delivers the optimal solution will be the one that wins out.

When we first began designing the SkyTrough, we didn’t realize that we would get better optics; we just didn’t want to use glass and have to deal with breakage and the other issues with glass reflectors.

But we got better optics, and this is the kind of discovery that occurs; it is the most fascinating part of designing new technology. I suspect as concentration ratios increase and collectors get bigger, others will look at new strategies to get better optics and find exciting ways to improve the technology. It is the self-evolving nature of technology that will transform trough design and drive down prices.

CSP Today: Would you say that projects are trending toward large scale, rather than modular?

Randy Gee: Yes, I would say so. There are many 50MW projects in Spain and these were an important part of advancing CSP project sizes. Once upon a time, 50MW was considered to be very big; nowadays, people are talking about 250MW projects. We’ll see the trend pan out as to where the optimal project size lies.

From a purely technical perspective, 150MW may be the optimum size. But as we all know, many factors will influence the scale of a project – such as the availability of finance, the level of confidence within the financial community, and the terms of the PPA.

Whether a project is 50MW or 200MW, the most important thing is that the technology is going into the ground, so that the sector can learn by doing and to constantly improve the technology so that costs may come down.

CSP Today: How important is the Indian market for the CSP sector as a whole?

Randy Gee: India is a market that reflects the need to reduce costs. It will be much more competitive than Spain – and the greater financial pressure will force the CSP sector to continue to reduce costs.  

CSP Today: Is SkyFuel in discussions with any CSP developers in India with a view to deploying the SkyTrough?

Randy Gee: We have personnel in India right now. India is a very important market for us precisely because low cost is critical – it is a great place for [SkyFuel] to begin significant deployment.

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

Rikki Stancich: rstancich@csptoday.com