Comparison: base load power plants vs. peak load power plants

Introduction to the importance of modern power systems

In the context of modern power supply systems, it is of central importance to ensure a balanced interaction of different types of power plants in order to enable both a stable base load and reliable coverage of short-term peak loads. Traditionally, a distinction is made between so-called “base load power plants” and “peak load power plants”. Both types of power plant fulfill different but crucial tasks for the overall system. A deeper understanding of these concepts is of great importance, especially in view of the growing demands for flexibility, cost-effectiveness and climate compatibility of electricity generation. In the following, the essential properties, methods of use and challenges of base and peak load power plants are presented and related to each other in order to better understand the dynamics of a sustainable energy system.

Characteristics and tasks of base load power plants

“Base load power plants” are traditionally considered the heart of the power grid. They are characterized by the fact that they deliver constant, continuous power in order to reliably cover the daily, always present electricity requirement - the so-called base load. The idea behind it is easy to understand: Although the demand for electricity fluctuates over the course of the day and week, there is always a minimum level of demand that is never fallen below. Base-load power plants therefore ideally run near full load around the clock. This uninterrupted operation makes them particularly useful for types of power plants that can only respond slowly to changes in load. At the same time, they are designed to be economically efficient when operated at high capacity over long periods of time. Typical examples of such systems are nuclear power plants, lignite power plants, large run-of-river power plants and some forms of biomass power plants. These are usually designed in such a way that their fixed costs are high, but the variable costs - especially the fuel costs - are comparatively low. Due to their continuous operation, the high investment costs are spread over many operating hours, which is what makes the model possible.

Challenges and flexibility problems of base load power plants

A key feature of baseload power plants is their limited flexibility. These systems are usually large and often technologically complex. If demand changes on the network, they react only slowly. If they are actually shut down or their performance is adjusted at short notice, this will cause time and technical effort. It is precisely this inertia that is being viewed increasingly critically in the wake of the energy transition. With the increasing share of fluctuating renewable energies, such as wind and solar energy, the need for flexibility is growing. This means that baseload power plants will either have to react more quickly in the future or be supplemented by other, more flexible solutions. Nevertheless, they remain an essential component of the energy system, at least in the medium term, as they form the reliable basis for the electricity supply.

Characteristics and tasks of peak-load power plants

The so-called “peak load power plants” have a completely different profile. These systems are specifically used to cover those moments when electricity consumption suddenly increases and base and medium load capacities are not sufficient to cover demand. These consumption peaks often occur in the early evening when many households are cooking, turning on electrical appliances or activating heating or cooling systems at the same time. Special events such as major television broadcasts or extreme weather conditions can also trigger short-term surges in demand.

Flexibility and functionality of peak-load power plants

Peak-load power plants are characterized by their high flexibility and rapid response ability. “They step in in the shortest possible time” and thus stabilize the power supply if an unexpected jump in demand occurs. Typically, gas turbine power plants or pumped storage power plants are used for this function. Gas turbines can be started up within a few minutes and are then immediately available as a power source. Pumped storage power plants use excess energy from the grid (e.g. from renewable sources when supply is high and demand is low) to pump water to a higher basin. If demand later increases, the water is allowed to drain away again and turbines generate electricity. This system therefore acts as a type of natural energy storage that can be activated at very short notice.

Economic efficiency of peak load power plants and their operational logic

Another important aspect is the cost structure of peak-load power plants. Unlike baseload systems, they typically have lower fixed costs, but their variable costs are relatively high. This is due, among other things, to the fact that the fuels used - often natural gas - are more expensive or the efficiency of the systems is lower. Nevertheless, they make economic sense. Especially during peak load times, electricity prices on the electricity exchanges are often particularly high, which makes the operation of these systems profitable despite high variable costs. This mechanism ensures that peak-load power plants are only used if they are really worth operating. Although they are in operation less often, they earn a significant portion of their income in a short period of time due to the high electricity prices.

Interaction between base and peak load power plants: stability versus flexibility

The comparison of base and peak load power plants shows a tension between stability and flexibility, continuity and short-term use. A modern energy system needs both to be reliable and economical. Although the public discussion often gives the impression that the energy world is developing exclusively in the direction of decentralized, renewable sources, central, stable and reliable power plants will actually still be needed in the future to guarantee security of supply. However, the weights are shifting. Where once only large, inflexible base-load power plants formed the backbone, storage technologies, fast backup capacities and flexible load management strategies will play an increasingly important role in the future.

Effects of renewable energies on base and peak load power plants

In addition, the balance between base load and peak load is changing due to the growing share of renewable energies in the electricity mix. Wind and solar energy are naturally not constantly available. There is not enough wind at all times, and solar radiation is also tied to the time of day, weather conditions and seasons. What does this mean for base and peak load power plants? On the one hand, it can happen that in times of high renewable feed-in - for example on windy days with lots of sun - the need for base load energy decreases because renewables themselves supply a significant amount of energy to the grid. In these moments, classic base-load power plants can be reduced in their function. On the other hand, the fluctuating generation leads to short, unforeseen peak load situations occurring more frequently, in which quickly regulated power plants or storage solutions have to step in.

Dynamizing the energy supply: an outlook

In the long term, the term “baseload power plant” could change in its current form. Instead of a few large, inflexible plants, the future could be characterized by a large number of flexible but also highly available power plants that, in combination with storage and intelligent load management, meet the high need for stability. Pumped storage plants, battery parks, power-to-gas systems and other forms of storage are becoming increasingly important. This could weaken rigid role models for base and peak load power plants. The classic distinction, in which base-load power plants run around the clock and peak-load power plants are only switched on, could disappear in favor of a more dynamic system in which many units fulfill both base-load and peak-load tasks as required.

Intelligent interaction is the key to a stable energy future

Several key findings can be made: Firstly, baseload power plants still form the stable basis of electricity supply in many of today's energy systems. They are cost effective as long as they can be operated continuously near their maximum output. Second, peak-load power plants complement this stability with the ability to cover short-term load fluctuations. They come into action when demand exceeds normal levels, thereby ensuring security of supply. Thirdly, the need for flexibility will increase due to the expansion of renewable energies, which places new demands on the generation structure. Fourth, technological developments in storage and network technologies as well as demand side management are leading to a potential redefinition of roles. This means that the previous, rigid distinction between base-load and peak-load power plants is gradually being replaced by a more dynamic, intelligent system.

Overall, it is a multifaceted topic in which technical, economic and ecological factors interact. The challenge is to find a balance between stability, profitability and sustainability. Base and peak load power plants form different but equally important building blocks. Their sensible combination enables a reliable energy supply and at the same time creates space for innovations that will enable even more flexible, cleaner and more efficient power generation in the long term.

Short version comparison: base load power plants vs. peak load power plants

function

• Base load power plants: They supply the constantly required base load in the power grid around the clock.
• Peak load power plants: They cover short-term peaks in electricity consumption that go beyond base and medium load.

Mode of operation

• Base load power plants: These power plants operate continuously near the full load limit.
• Peak-load power plants: They are used at short notice and flexibly as needed.

flexibility

• Base load power plants: Limited controllability and slow response to load changes.
• Peak load power plants: Very fast response times and high flexibility.

Cost structure

• Baseload power plants: They have high fixed costs but low variable costs (e.g. fuel costs).
• Peak-load power plants: They have lower fixed costs but higher variable costs.

Typical power plant types

• Base load power plants: Examples include nuclear power plants, lignite power plants, run-of-river power plants and biomass plants.
• Peak load power plants: Typical examples are gas turbine power plants and pumped storage power plants.

Duration of use

• Base load power plants: These power plants are in continuous operation.
• Peak load power plants: They are only operated for short periods during peak consumption.

economics

• Base load power plants: They are only economical when operated continuously.
• Peak load power plants: They are economical due to high electricity prices during peak times.

Suitable for:

• Hybrid power plants consisting of solar, wind, hydropower and battery storage
• Virtual power plants: decentralized energy, centrally controlled - stable networks through networking - optimizing electricity production and consumption