What is energy recovery? In a world where the efficient use of resources is becoming increasingly important, energy recovery plays a central role. At its core, it is about reusing energy that would normally be lost as waste heat, friction, or kinetic energy.
Brief summary
Energy recovery (recuperation) is the process by which energy that is generated in a system and would otherwise be unused is converted into a usable form and fed back into the cycle. Whether this is heat from industrial systems, the kinetic energy of a braking vehicle, or pressure differences in gas pipes – the aim is to use this energy for other purposes.
Basic principles and technologies
The functional principle of energy recovery is based on the physical fact that energy is neither generated nor destroyed, but can only be converted from one form to another. Recovery involves converting energy that is in an inefficient or not directly usable form (e.g., kinetic energy of a moving object or thermal energy as waste heat) into a usable form of energy. It is often converted into electrical energy, which can then be stored in a rechargeable battery or battery storage system, or fed directly into the power grid.
To make it usable, heat pumps raise heat to a higher temperature level during heat recovery
Energy conversion explained simply
In many processes, energy is produced in forms that are not needed for the original purpose or are as a by-product. For example, a vehicle loses kinetic energy when braking, which is released as heat in the brakes and the surrounding air. The production processes in a factory generate considerable amounts of waste heat. This is exactly where energy recovery comes in: it converts this “lost” energy.
A generator is a device that is frequently used for this conversion. While a motor converts electrical energy into motion, a generator does the opposite: it converts kinetic energy into electrical energy. This principle is crucial for recuperation in vehicles. Heat recovery often involves heat exchangers that transfer thermal energy from one medium to another, or heat pumps that raise heat to a higher temperature level in order to make it usable. The use of DC power grids in industry also makes it possible, for example, to recover the energy generated when braking or reducing loads. A typical example is a robot. When the robot moves a heavy crate downwards, the motor converts the kinetic energy into electrical energy.
Key technologies for energy recovery
Different technologies are used to recover energy from different sources. The most important approaches include:
Recuperation: Recovery of kinetic energy
Recuperation is a common form of energy recovery, for example in electric cars, e-bikes, and industrial systems. When braking, the electric motor acts as a generator and converts kinetic energy into electricity, which is fed back into the battery. This increases the range and reduces brake wear. Energy is also recovered in DC grids when loads are reduced, e.g., in robots and in storage and retrieval machines. This energy can be made available directly to other loads, which increases efficiency and service lives and reduces the thermal load.
Heat recovery: The use of waste heat
The concept of heat recovery utilizes the waste heat generated by processes that would otherwise be released unused – for example in industrial systems, power stations, and buildings. It is particularly effective in ventilation systems and production processes. Heat is transferred from the hot media (e.g., exhaust air, exhaust gases) to colder media (e.g., fresh air, water) via heat exchangers. The recovered energy can the be used for heating, warm water preparation, and process preheating. This saves energy, cuts costs, and reduces the consumption of fossil fuels.
Pressure recovery
In systems where media is transported under high pressure and this pressure must be released at the end of the process, the energy released can also be recovered. One example of this is the release of natural gas in gas distribution networks. Instead of simply reducing the pressure by throttling and losing the resulting energy as heat, an expander or turbine can be used to convert the pressure energy into electrical energy. This technology is particularly efficient where large pressure differences have to be overcome.
Other methods and applications
In addition to the main technologies already discussed, there are other specialized methods of energy recovery. These include, for example:
- Recovery of chemical energy: In certain industrial processes, chemical substances that are produced as waste products can be recycled and their chemical energy reused.
- Osmotic power stations: A technology still under development that generates energy from the difference in concentration of fresh and salt water.
- Thermoelectric generators: Devices that can convert temperature differences directly into electrical energy, often used in niche applications to utilize low levels of waste heat.
Advantages of energy recovery
The advantages of energy recovery are manifold and range from ecological to economic and operational aspects. It is a highly effective means of positively influencing the overall energy balance and reducing dependence on primary energy sources.
With recuperation, an electric car requires less charging current to drive a certain distance
Increased energy efficiency
A particularly obvious advantage of energy recovery is the drastic increase in energy efficiency. By recovering and reusing otherwise lost energy, the total energy requirement for a particular service or process is reduced. As an illustration, for example, an electric car with recuperation requires less charging current to drive a certain distance, and an industrial system with heat recovery requires less fuel for its heating processes. This efficient use of the available energy results in an optimization of the entire value chain and significantly reduces the amount of energy required. Systems are becoming more efficient and more economical to operate.
Contributing to climate protection and the energy transition
Energy recovery is a powerful lever in the fight against climate change. Every kilowatt hour of energy saved through recovery is one that does not have to be newly generated. This directly reduces the consumption of fossil fuels, which in turn lowers emissions of greenhouse gases such as carbon dioxide. At a time when the focus is on the energy transition – the transition from fossil fuels to renewable energy sources – energy recovery is the perfect supplement. It minimizes the overall energy consumption and helps to reduce the load on the power grid, which also supports the extension of renewable energies. It makes the entire power supply more sustainable and robust.
Economic benefits and cost savings
The reduction in energy requirements leads to lower operating costs. Companies and households that use energy recovery systems can save considerable amounts of money by spending less on electricity, gas, and other fuels. With electric vehicles, the range and service life of the brakes are extended as they are subjected to less mechanical stress. The investment in energy recovery technologies often pays for itself quickly through the savings achieved, making it an attractive option for industrial, commercial, and private applications. In the long term, the efficient recovery of energy leads to a stabilization of energy costs.
Areas of application for energy recovery
Energy recovery is not a niche technology, but is used in many areas of our lives and our economy. Its broad implementation is a good indication of its raft of benefits.
E-mobility
Recuperation is a core component of e-mobility. Electric cars, e-bikes, and e-scooters use regenerative braking systems to convert kinetic energy into electrical energy when braking and driving downhill, and feed this recovered energy back into the battery. This not only increases the range of the vehicles, but also makes driving more efficient. It is a key factor that increases the attractiveness and sustainability of electric vehicles compared to conventional combustion engines. Without this energy recovery capability, the efficiency of electric vehicles would be significantly lower.
Industry and production
Industrial processes generate a great deal of waste heat, which often remains unused. Heat recovery represents great savings potential here: waste heat from furnaces, cooling processes, and computer servers can be used to preheat air and water, for heating and to generate electricity – e.g. in steelworks, data centers, and or chemical plants. Pressure recovery is also used in the gas and oil industry. In addition, braking energy can be recovered in DC grids and fed directly to other loads. This improves the energy balance and increases efficiency.
Building technology
To minimize their energy consumption, state-of-the-art buildings are increasingly relying on energy recovery. Heat recovery is becoming standard, in particular in ventilation systems. It ensures that the heat from the exhaust air is not simply dissipated to the outside, but is used to preheat or pre-cool the fresh air supply. This significantly reduces the energy required for heating in winter and cooling in summer. This is a decisive element in achieving the high efficiency standards required in passive houses and low-energy buildings.
Local public transport
Energy recovery also plays an important role in local public transport, especially in trains, subway trains, and streetcars. When these vehicles brake, their electric motors, which then act as generators, feed electrical energy back into the overhead line grid or into stationary storage systems. This recovered energy can then be used by other trains in the same grid to accelerate, which significantly reduces the overall energy consumption of the system. This contributes to the sustainability of local public transport and helps to reduce operating costs.
Challenges and future prospects
Despite clear advantages, energy recovery also brings challenges: a high initial investment, technical adaptation to processes, and limited storage options – especially with fluctuating power generation. Nevertheless, the prospects are promising: advances in research and development as well as smart control systems and smart grids increase efficiency and reduce costs. As climate awareness grows, energy recovery is becoming a central building block of the energy transition and our energy infrastructure.
Summary
Energy recovery is much more than just a technical detail; it is a fundamental principle for sustainable and efficient energy use. By consciously recovering and reusing energy that would otherwise be lost, we can not only significantly increase our energy efficiency and save costs, but also make a decisive contribution to climate protection and to successfully shaping the energy transition. The continuous development and widespread implementation of these technologies are essential if we are to meet the challenges of modern power supply systems and pave a sustainable path for the future.
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