Energy transfer system comprising a phase change material

Abstract

An energy transfer system for absorbing, temporarily storing and releasing energy is disclosed. The described energy transfer system comprises (a) a first container containing a Phase Change Material, (b) a heat generation element, which is connectable to an external energy source and which is capable of charging the Phase Change Material with thermal energy, wherein energy provided by the external energy source is used, and a heat extraction element, which is connectable to an external heat engine and which is capable of extracting thermal energy from the Phase Change Material, wherein the external heat engine is capable of converting the extracted thermal energy into electric energy. It is further described an energy transfer arrangement comprising two of such energy transfer systems, and a method for absorbing, temporarily storing and releasing energy.

Description

FIELD OF INVENTION[0001]The present invention relates to the field temporarily storing thermal energy. In particular the present invention relates to an energy transfer system for absorbing, temporarily storing and releasing energy. Further, the present invention relates to an energy transfer arrangement comprising two of such energy transfer systems. Furthermore, the present invention relates to a method for absorbing, temporarily storing and releasing energy.ART BACKGROUND[0002]The production of electric power from various types of alternative energy sources such as wind turbines, solar power plants and wave energy plants is not continuous. The production may be dependent on environmental parameters such as wind speed (for wind turbines), insulation (for solar power plant) and wave height and direction (for wave energy plants). There is very often little or no correlation between energy production and energy demand.[0003]One known approach to solve the problem of uncorrelated elec...

AI Technical Summary

Benefits of technology

[0022]According to an embodiment of the invention the Phase Change Material comprises a metal, in particular aluminium. This may provide the advantage that the PCM has a comparatively high melting point temperature. Specifically, aluminum has a melting point temperature around 660° C. and a latent heat coefficient which is relatively high. Therefore, aluminum is a suitable material for the described energy transfer system. Further, the level of the melting point temperature makes it feasible to provide appropriate containers and isolation material as well as heat generating and heat extraction elements which can operate optimal within a temperature range around the melting point of and exploit the excessive potential for latent energy storage.

[0052]It is mentioned that the extracted thermal energy from the PCM may in addition be provided for the simple use of direct heating processes such as for residential and / or for industrial heating and cooling.

Problems solved by technology

However, unless sophisticated pressure vessels are used the maximum temperature of heat capacity storage in water is limited to 100° C.

Since for large capacity storage the cost of pressure vessels would be prohibitive, the use of water as a heat storage material is limited to a maximum temperature of 100° C. However, a maximum temperature of 100° C. is much too low in order to provide any useful thermodynamic efficiency of a heat engine, e.g. a steam turbo generator, which is to be operated on demand for release of the stored thermal energy.

Consequently, the benefits of the high heat capacity of water cannot be exploited in practice for high-volume energy storage.

However, solids generally have low heat capacity, and this leads to high volume requirements and to a low energy density.

However, molten salts have the drawback that they are generally not stable at temperatures much above 400° C., thereby limiting the thermodynamic efficiencies of related heat engines.

They also have the drawback that initial melting and re-melting on unintended solidification is very difficult due to the low conductivity of crystalline salts.

One problem related to the known heat storage systems is that for large scale energy storage, such as for storing energy produced from wind farms for longer time periods (hours), the capacity of known heat storage systems is not sufficient.

If one would scale up a known heat storage system to a system having sufficient capacity for such purposes, the prize of such a scaled up system would be relatively high, which makes a scaled up system unattractive because of economical reasons.

Even further, for a scaled-up heat storage system it is difficult and not cost-effective to recover the stored energy.

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