Solar energy

Engine of the energy turnaround

Author: Dr. Robert Bartl, Bayern Innovativ GmbH (As of February 2015) Comparing the different renewable energies, solar energy clearly stands out: The most important point is the large expansion potential of photovoltaics. Systems for generating solar power can be installed and operated anywhere in the world. The second point: energy generated decentrally and close to the consumer relieves the networks and components and thus reduces the cost of infrastructure expansion.

Naturally, the performance of PV systems depends on the meteorological conditions. A suitable location with the area of southern Germany would be sufficient to cover the entire electricity needs of today's world population. In Germany, photovoltaic systems on all suitable roof surfaces alone could generate about 30 % of the German electricity demand. Since sealed areas such as facades or carports are also ideally suited, photovoltaic systems are hardly in competition with areas that can be used for other purposes.

Classical solar modules dominate

If one considers the solar technologies competing on the global and German markets, the "classical" solar modules based on silicon semiconductors continue to dominate. Today, they achieve efficiencies of over 20% even in large-scale industrial production and are inexpensive to produce. Further improvements are expected for the next generation of products. New PV technologies have therefore found it difficult to establish themselves so far. Although thin-film technologies require significantly less semiconductor material, their market share is only 10-15% due to their lower efficiencies. According to many forecasts, the thin-film market will even shrink to 7% by 2017.

In order to improve the efficiencies and thus the competitiveness of thin-film technologies, researchers and developers are looking for inexpensive semiconductor materials with very good absorption properties that are available in sufficient quantities. Promising research results are provided by coatings based on the structure of the mineral perovskite. However, CdTe and CIS thin-film technologies also represent alternatives. Pioneers are the companies First Solar, AVANCIS, Manz and Solar Frontier. CdTe and CIS thin-film cells are expected to serve three-quarters of the total thin-film market in 2014.

Storage is a prerequisite

One of the biggest challenges of the energy transition is to integrate the electricity from renewable energy sources, which is generated with large fluctuations throughout the day and season, into the existing energy supply system or to develop suitable alternative concepts. Photovoltaic systems designed for domestic electricity requirements with integrated electricity and heat storage solutions offer an interesting way of relieving the strain on the grids and reducing electricity costs for the end consumer. However, large-scale energy storage is a prerequisite for ensuring a sustainable supply of fluctuating renewable energies. In addition to minute and hourly storage systems, long-term and seasonal storage systems are needed.

Conversion of electricity generated by wind and PV plants during peak periods into hydrogen and its subsequent methanation

The resulting synthetic "Substitute Natural Gas" - SNG for short - can be efficiently transported and stored in large quantities due to the good European gas grid infrastructure. SNG is available in the short, medium and long term and meets all the requirements of an energy storage facility. SNG is suitable both as a raw material for the chemical industry, as a fuel for building heating systems and vehicle engines, and also for reconversion into electricity. This makes SNG an important alternative for a climate-neutral energy supply.

Accelerate innovations

The focus of many current R&D projects is the analysis of potential CO2 sources with regard to availability, generation potential, economic viability and costs. Biogas plants come into question as a sensible CO2 source for industrial power-to-gas generation. The CO2 contained in the raw biogas from the 6,000 biogas plants currently operating in Germany could be used to generate more than 25 TWh of storable methane annually via the power-to-gas process. The electricity required for this comes from fluctuating wind and photovoltaic plants.

With rooftop photovoltaic plants, electricity can already be produced today at prime costs of 14 ct/kWh. These are significantly below the current German end consumer prices of about 30 ct / kWh, but still above the electricity production costs of lignite (5.3 ct / kWh), hard coal (8 ct / kWh) or gas and steam power plants (9.8 ct / kWh).

In order to make photovoltaics, storage technologies and solar fuels even more competitive, innovative technologies, production processes and installation methods are required. The close integration of industry and science makes an important contribution to implementing new research results more quickly in the production lines of industry - regardless of the many different approaches to further increasing efficiencies and reducing production costs. It is important to look at the energy system as a whole. While the focus is currently still on the electricity market, the heating market and, not least, the topic of energy efficiency must be included more consistently in order to make the energy transition a success.