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Photovoltaics

Companies and institutes are continuously working on further reducing the costs of photovoltaic production whilst increasing the quality and efficiency of cells and modules. In 2019, the German Federal Ministry for Economic Affairs and Energy (BMWi) approved 135 new photovoltaic funding projects within the framework of the 7th Energy Research Programme. In 2019, around 96 million euros were invested in 491 ongoing research and development projects.

In joint funding projects, industry and science set themselves concrete development goals. This reduces investment and operating costs, and increases finance options: Germany's largest subsidy-free solar farm "Barth 5" west of Stralsund went into operation in November 2019, with a capacity of 8.8 megawatts. It is financed through a Power Purchase Agreement, abbreviated PPA. Such long-term contracts between power plant operators and electricity consumers secure the operation of the plants.

IRENA, the international agency for renewable energy sources, has documented the development of the past decade in its report "Renewable Power Generation Costs in 2019": According to this, the cost of generating power from photovoltaics fell by 82 per cent between 2010 and 2019. The costs are more and more frequently below those for the generation of power from fossil fuel-fired power plants.

Distribution of incentives and grants and development of the volume of new approvals in the photovoltaic sector since 2015.

Distribution of incentives and grants and development of the volume of new approvals in the photovoltaic sector since 2015.

115 gigawatts added worldwide in 2019

The decreasing costs are reflected in the expansion figures. Both nationally and internationally, power from photovoltaics has a large share in today's energy provision. Around 9 per cent of the power that reached German consumers in 2019 came from photovoltaics. Data from the Renewable Energy Statistics Working Group indicate that the installed photovoltaic output in Germany increased from around 45.8 to 49 gigawatts in 2019. This puts expansion in 2019 at around 3.8 gigawatts, significantly higher than in 2018, when around 2.9 gigawatts of new output was added. Initial estimates by the International Energy Agency (IEA) indicate that around 115 gigawatts of photovoltaic output was added worldwide in 2019.

Developing new areas through integrated photovoltaics

The use of the technology is manifold: Small rooftop installations and large open space installations on fields are currently the best known areas of application. Further potential can be found in so-called integrated photovoltaics: Here the modules are built into surfaces. Building façades are particularly suitable for this. Sound-proofing walls, vehicles, watercourses and agricultural land can generally also be considered. Thin-film solar cell are particularly suitable for this purpose. One example are the so-called CIGS solar cells. The name stands for the elements copper, indium, gallium and selenium, which form the semiconductor in this cell concept.

CIGS modules on the façade of a Spar supermarket in Norway.

CIGS modules on the facade of a Spar supermarket in Norway.

Crystalline silicon as the basic technology

Cells based on crystalline silicon as a semiconductor continue to be at the forefront of development. The current standard here is the so-called PERC technology, short for "Passivated Emitter and Rear Contact". So-called bifacial types are new. These double-sided solar cells can absorb both incident light at the front and stray light at the rear side, thus increasing the light yield.

With a view to the future, stacking cells are also a central topic of BMWi research funding. Two or more solar cells of different materials are stacked on top of each other. Crystalline silicon often serves as the base layer. Combining different semiconductor materials makes it possible to utilise a wider spectrum of sunlight. Each layer captures a different partial spectrum, thereby increasing efficiency. The efficiency indicates what percentage of the incident light energy can be converted into usable energy, meaning power.

Steep development curve for perovskites

Especially stacking cells with perovskites are close to series-production readiness. Perovskites are a semiconductor material that has only played a role in photovoltaic research since 2009. Research and development has resulted in a steep increase in the efficiency of cells made of silicon and perovskite in recent years.

In all research approaches it is important that new concepts can be transferred from the laboratory to industrial production processes. Plants that can be flexibly converted to different cell concepts and information and communication technology play an important part in this.

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