Information on the project
Renewable energy sources to secure the base load in electricity supply
Contribution, perspectives, investments
Background and central aspects of the topic
The expansion of electricity generation from renewable energy sources is a central component of German energy and climate policies. The share of renewable energy sources used in electricity consumption is targeted rise to 25%-30% by 2020 and continue to rise steadily after this date. Much of this expansion in regenerative energy sources will be based on technologies with fluctuating supply. These include wind energy in particular, but also and increasingly solar generation of electricity. The strongly increasing proportion of fluctuating feed-in means that the requirements on the electricity supply and its structure are considerably changed.
The base load refers to the minimum level of electricity demand which is never undercut in diurnal variation. The base load is met by power stations which produce electricity at low variable costs and which (usually) can only be regulated with difficulty. In Germany, these are currently mainly hydroelectric, nuclear or lignite power plants.
In this context, consideration is being given to the contribution that renewable energy sources (beyond hydropower) can make to cover the base load. A central term in the discussion is the so-called "capacity credit". This describes the contribution a technology – either conventional or renewable – can make with a defined certainty to meeting the electricity demand.
While wind energy and especially photovoltaics (PV) taken by themselves only boast a low capacity credit, the level for biomass, hydropower and geothermics is in the range of comparable plants in the conventional energy system. If the various renewable electricity generation technologies are taken together as an interconnected unit, the guaranteed capacity turns out higher overall because, for instance, there are compensatory effects between PV and wind energy.
The guaranteed capacity, however, reveals only little about how well the electricity demand can be met by renewable energy sources and what kind of power plant park must be maintained to meet the demand. In this respect, in considering the contribution of renewable energy sources to safeguarding the base load, the load profile of the demand must be included. The load to be met by conventional power plants results from the difference between renewable production and demand. If the expansion of renewable energy sources leads here to a reduction in the necessary deployment of base load power plants, this constitutes a contribution to reducing the conventional base load.
During discussion of the current amendment of the Renewable Energy Sources Act (Erneuerbare Energien Gesetz, EEG), much significance was accorded to this topic. It is an important aim for the further development of the EEG to create incentives for renewable energy generation, wherever possible and economically reasonable, to orientate its feed-in to the current electricity demand. In the EEG amendment, the significance of this topic is emphasized by the power to issue statutory instruments set out there for improved market integration and the creation of an integration bonus.
Objective and procedure
The range of topics on "base load" is by nature not accessible to an isolated view, but must be embedded in an overall consideration of the structure of electricity generation (power plant park, economic and ecological determinants of power plant deployment, "virtual power plants", investment decisions, etc.) and the electricity demand (e.g., load management, energy-saving measures and rational energy use).
To handle these questions, a method is needed which covers both the short-term implementation of power plants on an hourly basis and long-term investment decisions on the energy market. Consideration of the effects of various scenarios in future investment paths in the field of renewable energy sources on the electricity market and the short-term deployment of power plants is of particular significance.
For this reason, it seems necessary to conduct our own model-supported investigations into scenarios of future electricity generation as well as to evaluate the existing literature.
Overall, the following procedural steps are planned:
- Compilation and comparative analysis of the results of previous scientific research;
- Model-supported analyses on the development of electricity demand and meeting the requirements in the current and future system of electricity supply;
- Investigation of the present and expected future contribution of renewable energy sources to safeguard the base load in electricity supply;
- Analysis of improved system integration by investing in the field of renewable energy sources, grid expansion, storage technologies and in the rest of the electricity sector;
- Infer from this the requirements on the future system of electricity supply;
- Overview of new and progressive technologies which could fulfil these requirements in the future;
- Identify options for guaranteeing that the base load will be met with ambitious expansion targets for renewable energy sources.