Thermal energy is energy relating to temperature or, more specifically, the kinetic energy of matter – atoms and molecules put in motion by heat. The term is used synonymously with that of internal energy, which refers to the energy contained within a system. Heat is a simple way of defining the amount of thermal energy of a system. It can be transferred from one system to another, for example, by conduction, convection and radiation. It naturally only moves from hotter objects to relatively colder ones, as cold is merely the absence of thermal energy. Heat transfer – the transfer of thermal energy – can be used to generate renewable power and to store electricity.
How can renewable thermal energy be used directly?
Renewable thermal energy can be used directly to provide heat, for example, to residential buildings and for industry applications. The most prominent use of thermal energy for direct heat is solar energy, which can be used to create hot water or warm air. Geothermal energy is a further, increasingly popular option. Both are fully renewable and clean alternatives to heating technology involving combustion of fossil fuels. Another sustainable use of thermal energy is the utilization of waste heat, which can be redirected, especially from industrial processes. Since its generation is usually associated with emissions, it isn’t technically carbon-neutral, but as it is a byproduct, it is considered clean.
How are thermal processes used to store energy?
Thermal energy storage can also be direct, for example, by directing the heat from one system to a colder system with good storage properties. Substances with high thermal capacities include water (both in liquid and solid frozen form) and stone (for example, granite). Indirectly, thermal storage can also be used to electrically heat or cool a material (usually at times when electricity is cheap), which later distributes or attracts ambient heat to its surroundings (when electricity is more expensive). More technologically advanced processes utilize the different physical properties of certain materials at varying temperatures to store and release electric power.
Effectively managing surplus energy
Energy storage systems by MAN Energy Solutions help make the most efficient use of different types of energy, including electricity generated from renewable sources and thermal energy generated from low-emission and natural sources, or as a by-product of industrial processes. Smart hybrid solutions integrate all these inputs and other forms of energy to coordinate them with the given requirements or store them for later use to avoid waste.
Thermal energy storage
Thermal energy can’t only heat and cool. The temperature differences and heat transfer systems can also be used to store and release electricity, balancing out any temporary energy surplus and providing security of supply. MAN Energy Solutions has pioneered ETES (Electro-Thermal Energy Storage), the only large-scale system on the market capable of using, storing and distributing heat, cold and electricity simultaneously. It is ideal for industrial or municipal applications where the production and need of thermal energy consistently arise in parallel and can effectively be exchanged within a closed system.
Another possibility for storing thermal energy is MAN MOSAS (Molten Salt Energy Storage). The energy storage of molten salt is an economical and flexible technology that can be integrated into various applications. It stores heat from renewable energies directly or indirectly via electric heating systems or heat pumps. The heat is later converted into steam to drive a steam turbine.
Most energy demand worldwide is for heating and cooling, not in transport nor in electricity as is commonly thought.