Solar

Through Thick and Thin

Issue 4 and Volume 11.

Despite the apparent conflict between advocates of thin-film and crystalline silicon photovoltaic technologies, Florian Holzapfel argues that drawing these two camps together can yield huge opportunities for the industry as a whole. The ultimate goal is not technology dominance, it is cost reduction.

Sometimes it seems that there is a deep chasm dividing the photovoltaic community into two, sometimes hostile, camps. On the one side stand the knights of the old order, keeping the faith of classic crystalline silicon technology. On the other side are stationed the dedicated followers of thin-film. Those advocates of thin-film technologies see a new age dawning on the PV horizon and look down on those relics of a former age who cannot yet see the light dawning.

As always, things are not quite as simple as they may seem to be at first glance. For while there may be a potential conflict between advocates of thin-film and the better-established crystalline silicon technologies, this conflict in fact misses the point. Because it is not a question of which PV technology might or might not prevail in the future, but what they all can do to play a part in the breakthrough of PV that counts. And, as we all know, that is contingent upon the industry’s ability to bring down production costs rapidly.

Therefore, leaving aside real or imagined potential lines of conflict, a thorough examination of the key success factors of both crystalline silicon technology and various thin-film technologies can be equally valuable to the purported rivals. For it can reveal how the strengths of both camps can be united into a global industry that is both successful and sustainable.

Efficiency – the key parameter

Of primary importance is the efficiency of the cells or modules and increasing efficiency remains one of the most important tasks that the industry must accomplish. Although it must be remembered that striving for ever greater efficiency is not an end in itself, nonetheless, the significance of raising the efficiency of photovoltaic technologies cannot be underestimated. It is a means to an important end: bringing down the costs of a whole photovoltaic system.

It is a well known fact that efficiency is one of the main advantages of crystalline silicon (c-Si) technology. It is also no secret that there is still a lot of potential for further increases. Incremental achievements in the proven technology are still possible, but if the industry wants to move ahead, then it has to focus on research and development. This is because classic cell technology will not see any great leaps in efficiency levels. The industry has to be firmly dedicated to new concepts and new processes. Q-Cells, is not alone in implementing a dedicated R&D programme. In this example it entails both the development of radical innovations in metallization, with a new process for back side contacting, and research on the next generations of solar cells. These back contact cells have an efficiency potential of more than 18% (multicrystalline) and above 21% (monocrystalline) respectively. Of course, this does not come cheap. The Q-Cells Research Centre cost nearly €50 million to build in order to have a commercial pilot production line on a reasonable scale to advance the next generation cell developments. Such significant investments are necessary because while a laboratory result may be potentially encouraging, it is a far cry from industrial production.

Even if efficiency has to be raised here too, the first priority in that field is the establishment of stable production processes and a rapid up-scaling of production. When we look at all the ‘revolutions’ and ‘breakthroughs’ that have been promised by the PV industry so far – and what has been delivered – we see clearly that this task is not as simple as it might appear, not by far.

A scalable platform

The second key factor for success, and which is possibly the decisive factor for the short- to mid-term future of thin-film technologies, is a scalable platform. For crystalline technology that is no big deal, a second major advantage that the industry has over its younger less mature rivals. Thus, even if the silicon shortage of late has cast some doubts over the dimensions that the crystalline silicon industry could possibly reach, the scalable platform is more than evident. The incumbent players are rapidly expanding their production capacities, and simultaneously many new producers are entering this buoyant growth market. With new sources of solar-grade silicon – won by upgrading metallurgical silicon – especially significant in addressing the supply chain constraint, this potential bottleneck to growth will, inevitably, soon be overcome.

Solar cell and module companies have grown enormously over recent years. Q-Cells alone, for example, is expecting to increase its output by a factor of four from 2007 to 2010. So there definitely is a scalable platform. It remains necessary, however, to monitor closely any other possible constraints that might arise in order to prevent another ‘silicon situation’ in which the industry runs into scarcity problems that inevitably increase costs. Solar glass or Tedlar® for example are manufacturing materials that provide ample business opportunities, but which also carry the potential supply risk – and its consequent financial risk implication – of insufficient resources at some point in time.

With thin-film, the situation is somewhat different. The growth potentials are certainly enormous, but nearly all of the players currently in the market have still successfully to manage an industrial-scale ramp-up. For some this might well prove to be the hurdle that is ultimately impossible to overcome.

So what do we need to master that challenge? The access to raw material is no problem so far, but this must not be underestimated for the future. It is also important to consider other components, for instance glass, which may still present some future supply side risks.

However, while such considerations are germane for the longer term, perhaps more important at the current stage of development are access to both Intellectual Property (IP) and key production equipment.

IP and ramping production

Given that technology and its production capacity are likely to be the key industry drivers in the short-to-medium term, accessibility is crucial. Basically, there are two different ways to handle this issue. On the one hand there are in-house developments of proprietary technologies, and on the other, there is the tendency to buy so-called turnkey factories from third party players. Turnkey developments are available for crystalline technologies and the thin-film area, mainly for silicon technologies, but with some first CIGS technologies arising.

Turnkey factories supplied by large technology players that already have a proven track record of delivering in other industry sectors look like the way forward, at least at first glance. The ramp-up support available from experienced external suppliers together with the possibility of learning from other turnkey fabrication operations from the same supplier can definitely help – allowing a comparably smooth transition to master the problems of up-scaling a technology platform. On the other hand, it must be remembered that the relatively high cost of such a solution, the dependency on the supplier and the limited opportunities to improve the technology further in-house can cast a long shadow. Another consideration is that turnkey solutions might also turn out to be ‘me too’ solutions. If just about anyone can gain access to identical technology, there is no real competitive advantage to be had from such an investment. Theoretically at least, it must be possible to do something better in the first place, rather than trying to do better something that everyone else also already does. Ultimately it may be argued that there is little to choose between the two options and the choice is a stark one that is based on risk perception.

The point is this: in developing proprietary IP and manufacturing capabilities, the risks are higher, you need more in-house know-how, and you cannot learn from anybody else. A company that is self-confident enough might prefer that choice, but a ‘no risk, no fun’ approach to running a business might not be everyone’s cup of tea. This is particularly so when other people’s money is involved.

The unsatisfactory conclusion must be that there is no silver bullet when it comes to scalable platforms. No one who wants to enter the thin-film field has to think for himself – and there is no guarantee that the chosen method will be the right one. That is all part of the excitement. Even so, whatever the decision, the solution has to be a stable one in order to achieve growth.

The decisive factor

Moving to the decisive factor for the future of PV as a whole, it is also necessary to address the question of which technologies will play a major part in the development of the sector. Some argue that thin-film is indeed the short track to cost reduction and competitiveness with conventional generation. In Germany, certainly, this predication is often repeated by journalists, pundits and politicians – people who are scarcely experts in the field.

Nonetheless, undoubtedly the potential for cost reduction is the main rationale for the development and commercialization of thin-film technologies. It is, however, in no way stipulated that they are the only way to reach the goal of ‘grid parity’ pricing and a low-cost future for PV. The silicon wafer based technologies – both those already in existence and the ones that are still to emerge – also have a large potential for cost reductions. A large bundle of sources for this cost reduction potential has already been identified. A 40%–50% reduction in system costs, based on 2006 figures, is definitely possible in the mid-term. Most of that reduction will be technology driven: raising the efficiency of the cells and modules, reducing wafer and cell thickness and other measures.

These are not in any way new concepts, but even so, they have to be driven on and on into perpetuity. We have already touched on the importance of scaling up the production capabilities of the various technologies. But it cannot be emphasized enough that getting bigger also means reducing unit costs – one of the iron laws of industry that the PV sector must also accept and adopt. And, of course, there is productivity. Manufacturing excellence will become more and more important in the future, and on-going standardization of the sector will also play its part in the drive towards cost reduction. Of course, getting there means that a lot of money has to be invested in new production facilities, better equipment and especially in continuing research and development.

That is all fairly obvious and no rational argument could deny the necessity for further investment in the industry. For those photovoltaic companies which want to make an impact on the sector, that is day-to-day business. However, to really take the lead, a much more radical approach might be needed. A detailed examination of the theoretical possibilities for bringing down processing costs reveals that the prospects for PV are even more glorious than they may at first glance appear to be.

For example, energy costs within the cell process, which are already fairly low, could be cut to almost zero. And material costs, which are the main cost drivers in the photovoltaic sector currently, show a fantastic potential for cost reduction. Even excluding silicon prices – which can only be influenced indirectly by a cell producer – material costs can be brought down enormously. The main factors here are the potential cost reduction for expensive metallization materials, where a reduction by three quarters is theoretically possible. Material efficiency for other materials like gases and chemicals is also currently very low. But step change improvements in productivity can only be achieved when the industry is prepared to find new production paths that are way off the beaten track.

Some might say that putting an emphasis on cost reduction is not very inventive and that we have heard that too often as it is. But the simple truth remains that cost reduction is the ultimate goal for the PV industry: it simply cannot be stressed too often. And, even if the potentials might be the highest on the silicon and the cell side of the business, everyone along the whole value chain bears responsibility for that common goal.

The means to this end are far from exhausted, with a lot that we already know about and a whole lot more that is possible in the ‘classic’ crystalline silicon photovoltaic technology arena.

Will thin-film win the day or will crystalline silicon technology lead us into the fabled and long sought after Land of the Low Costs? There is no clear answer. Not only do all the available technologies have an extremely large potential, but there also is a large bandwidth of attainable system costs for both thin-film and silicon-wafer based photovoltaics. Bringing the industry forward and reaching a competitive advantage is thus not so much a question of which technology to choose – it is much more a question of being very good at executing the business plan and getting the priorities right.

The key factors for success have been identified. Now it is time to act accordingly. Wasting energy on arguing about which is the ‘right’ technology is futile. There are several good ones out there, and it is also possible to work with many of them as Q-Cells does with its subsidiaries Sontor, Calyxo, Solibro and Flexcell.

As long as the overarching target of cost reduction is clear, the old saying still applies: Who dares wins.

Florian Holzapfel is chief technology officer for Q-Cells.
e-mail: [email protected]