Frontlines of the energy transition: Dr. Karl Hesse, Vice President Process Development at Wacker Chemie

The recent boom of solar energy in Europe is a cause for celebration. Having quickly become the cleanest and most cost-effective energy source, solar is now gearing up for massive deployments in 2020. Indeed, after a stellar year for installations in Europe, with a 110% increase and over 20GW of capacity added, the future of solar looks brighter than ever.

Where solar really soars is in its immense employment potential, where it creates more jobs per installed watt than any other power generation source. As a result of new installations, and research and development, solar jobs are expected to double by 2021 compared to 2016. In Europe alone, solar can create up to 500,000 jobs by 2030, and 1.7 million by 2050. These jobs are highly-skilled and local, and can help deliver a European Green Deal for all by targeting former coal regions for solar projects – sites that have untapped solar potential, and are thus attractive business environments for solar deployment and manufacturing. In fact, a recent Joint Research Centre study found solar to be particularly suitable for employing former coal workers and to help drive regional development.

In this series of articles, SolarPower Europe catches up with the people behind the power, putting a spotlight on those who work in the solar sector. Today, we talked with Dr. Karl Hesse, Vice President Process Development at Wacker Chemie.

Why did you choose to work in the solar sector?

As a chemist, I was always fascinated at how hyperpure silicon shapes our world. The material is the cleanest product that is produced worldwide, and has been the basis of our information age for decades now. Concerning the use of this material for solar, for me it was a “Saul to Paul” transformation. Until the mid-90s I was focused on Silicon for the Semiconductor Industry and was convinced that solar energy based on Crystalline Silicon would never be competitive. Then I realised that there is no future without solar energy in the long-term, and how huge the cost reduction potential is in the sector. So I started to develop dedicated silicon feedstock for the PV Industry, making it better and even more sustainable.

What is your favourite aspect of working in the solar industry?

The development of solar is breathtaking. Beginning as a niche application decades ago, it is now on the way to becoming the largest electricity source and our most important tool to mitigate climate change. Everybody can use solar, from very small domestic installations, up to utility-scale PV power plants.

Tell us about your day-to-day activities?

The success story of solar PV is driven by continuously reducing the levelised cost of electricity. The industry achieves this by increasing the efficiency of modules every year, and by reducing costs, e.g. reduction of specific resource consumption and economy of scale. As a world-leading producer of the key raw material in solar modules, Wacker must contribute its share to this development, too. In my role as head of Wacker Polysilicon’s Process Development Department, it is my responsibility to achieve these goals. Most polysilicon in the world is produced with the so-called ‘Siemens process’, which has been pioneered by Wacker. My team and I develop next generation equipment and improved processes to lower specific energy consumption, for instance.

Energy is the main contributor to the cost and environmental footprint of polysilicon. Competitive polysilicon production only works with affordable energy prices and low specific consumption. I am happy to say that our company is a world champion in specific energy consumption for Siemens polysilicon. All this goes together with extreme quality requirements. For that we are using high-end analytical and data processing tools. Wacker is well known for the outstanding quality of its material. We’re first choice particularly for challenging applications like n-type monocrystalline wafers and of course in semiconductors and we must not compromise in quality.

What is something most people do not know about solar?

The solar community is well aware of its achievements, and I am confident that we will continue this progress at the same speed over the next years. However, when I discuss these facts at public events, I always notice that many people do not know the level that solar PV has already achieved. Solar is already cost-competitive to established sources of energy; and the LCOE in sun rich countries is at or below 2 €cts/kWh. Even in a less sunny country like Germany, our recent 100 MW auction yielded a record price 0f 3.55 €cts/kWh.

Some people still question the sustainability of PV quoting outdated information on energy payback time. Those people are always surprised when I show them that the EPBT of PV has come down to about one year. But it’s only logical. Take the contribution of polysilicon for instance. Last year the industry reached a level for the specific consumption of poly below 4 grams of silicon per watt. Going back 15 years or so this factor was four times higher. In the same period Wacker has lowered its specific energy consumption by more than a factor of two. Putting these two facts together means that the silicon contribution to the energy budget of a PV module has come down by a factor of about eight

What do you think the future of the solar sector will look like?

In a few decades solar PV energy will be by far the dominant energy source. We will see a steady improvement in solar cell efficiency as we have seen over the last decades. Processes to improve single junction silicon cells are in the pipeline and by the time we get closer to the theoretical limits of single junctions we will have affordable tandem solutions (e.g. perovskite on silicon). We will see further improvements in materials and efficiencies. We can expect a further decrease of the LCOE and will achieve long term < 1 €ct/kWh in sunny regions, and < 2 €ct/kWh in countries with less sunshine.

The sustainability of solar PV will further improve, driven by initiatives like Ecodesign for instance, or the EU’s goal of a circular economy. We will see continuously growing solar PV deployment worldwide, which will not only include common sectors like utility-scale ground mounted or rooftops, but also all kinds of integrated solutions – such as BIPV, Agri-PV, vehicle-integrated PV, and floating solar. All of this needs to go hand-in-hand with integration into our energy systems – including enhanced transmission systems, smart grids, e-mobility, power to heat, power to gas.

Photo: Wacker Chemie

Do you work in the solar sector? We’d love to hear from you and how your work is contributing to the energy transition. Send your stories to

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