Patent Application
20140144785
The invention relates to an energy management system. The invention also relates to an industrial plant comprising an energy management system of this kind and to a method for operating an energy management system.
Water electrolysis with alkaline electrolysers (electrolyte is, as a rule, potassium hydroxide solution KOH) or with PEM (“Polymer Electrolyte Membrane” or “proton exchange membrane”) electrolysers is prior art.
Due to their construction, alkaline electrolysers can typically cover performance ranges of 25-100% of a predefined nominal performance and during start up require a lead time to attain the operating temperature. The degree of ageing in dynamic operation, i.e. with a frequent adjustment of the operating performance, is high with this type of electrolyser. Available performances of the alkaline electrolysers currently extend up to several MW. The predominant field of application for alkaline electrolysers is the production of hydrogen for material use in industry owing to the constant mode of operation which is possible there.
Due to their construction, PEM electrolysers can typically cover performance ranges of 0-100% of a predefined nominal performance (or up to 300% in overload mode with system-optimized design). Compared with an alkaline electrolyser a PEM electrolyser is distinguished by its dynamic mode of operation. Available performances in the case of PEM electrolysis currently extend up to about 0.5 MW. PEM electrolysers are predominantly used in the laboratory due to the compact construction, high purity of the generated electrolysis products hydrogen and oxygen, and their dynamic properties (H2 or O2 “on demand”).
The invention is based on the object of enabling particularly dynamic performance adjustment of an electrolysis system even in the case of high operating performances.
The object is achieved according to the invention by [an] energy management system comprising an electrolysis system having an alkaline electrolysis unit and a PEM electrolysis unit and a control unit which is designed to control the electrolysis units independently of one other with respect to an adjustment of an overall performance of the electrolysis system.
The invention is based on the idea of combining the alkaline and PEM technology to form a homogeneous, robust hybrid electrolysis system, wherein, due to the separate control or regulation of the operating performances of the electrolysis units, the properties of the two electrolysis technologies are used to achieve optimum overall performance of the electrolysis system and to constantly adjust this as quickly as possible to the operating requirements. The electrolysis system is used for energy storage and for simultaneously producing hydrogen and oxygen.
The alkaline electrolysis unit and the PEM electrolysis unit can be operated simultaneously or just one of the electrolysis units can be in an operating mode while the other one is shut down. The performance of only one of the electrolysis units for example is varied in the case of dynamic grid smoothing by means of the energy management system. An energy management system with a wide control range, high dynamics, high nominal performances, long life and advantageous system costs is provided in this way and the requirements of the electrolysis system may be better and more efficiently met than with one of the two technologies alone.
A further advantage of the energy management system in particular compared with current batteries and accumulators is that, owing to the use of electrolysis units, it is also used to produce hydrogen and oxygen, wherein the generated gases are stored for flow-back and/or are fed into the natural gas network and/or are provided for material use.
According to a preferred embodiment the control unit is designed to firstly vary the performance of the PEM electrolysis unit for the adjustment of the overall performance. This means that a performance adjustment in particular in relation to variations in the grid can be made in seconds or minutes by way of regulation of the performance of the PEM electrolysis unit if the operating conditions allow it. The operating performance of the alkaline electrolysis unit is substantially unchanged during power fluctuations; an adjustment of the operating performance of the alkaline electrolysis unit is provided in particular if this cannot occur by way of the PEM electrolysis unit or if the overall performance of the electrolysis system is to be changed over a relatively long period, for example lasting hours or days, by way of example in the case of a change in the requirements for the quantity of electrolysis products. The alkaline electrolysis unit of the electrolysis system, which is less dynamic but more powerful, primarily ensures a basic operating performance of the electrolysis system. With fluctuations in the power supply or with short-term variations in the operating requirements of the electrolysis system, mainly the operating performance of the PEM electrolysis unit is adapted since the PEM electrolysis unit can be operated much more dynamically than the alkaline electrolysis unit. A positive and a negative regulating performance can take place in this connection. Current peaks by way of example are attenuated since the PEM electrolysis unit is operated in overload mode (negative regulating performance). In the case of a positive regulating performance the PEM electrolysis unit is again partially or fully shut down so there is a passive supply of energy.
The alkaline electrolysis unit can preferably be operated in a performance range between 25% and 100% of a nominal performance. Particularly stable operation occurs in this performance range with minimal ageing. The alkaline electrolysis unit expediently has an adaptation time in this performance range for performance adaptation in the minute range, in particular in a range between 1 min and 5 min.
The PEM electrolysis unit is preferably operated in a performance range between 0% and 300% of a nominal performance. The performance range between 100% and 300% of the nominal performance constitutes an overload mode which can be attained with a system-optimized design of the PEM electrolysis unit. The overload mode is, as a rule, adjusted for only a short time, in particular under precisely determined operating conditions, such as the effect of heat or dissipation of heat. Overload mode conventionally lasts 15 min; with appropriate design of the components of the PEM electrolysis unit an extension to several hours is also possible.
The PEM electrolysis unit advantageously has an adaptation time for adaptation of its performance in the seconds range, in particular in a range between 1 s and 30 s. This means that the PEM electrolysis unit achieves overload mode in a few seconds, whereby current peaks may be compensated particularly quickly and effectively.
According to preferred variants the alkaline electrolysis unit has a performance between 100 kW and 100 MW, in particular between 100 kW and 5 MW. According to a further preferred variant the PEM electrolysis unit has a performance between 50 kW and 1 MW, in particular between 50 kW and 500 kW. The alkaline electrolysis unit, which conventionally has a higher performance, is therefore mainly used to produce hydrogen and oxygen and is operated in the performance range optimized for it of between 25% and 100% of the nominal performance. The PEM electrolysis unit complements the alkaline electrolysis unit in the production of hydrogen and oxygen but is also used for energy management by way of adjustment of the overall performance of the electrolysis system.
The energy management system is preferably a component of an industrial plant. A “component of an industrial plant” is here taken to mean that the energy management system has a spatial proximity to the industrial plant and is coupled in terms of process engineering to the industrial plant since at least one electrolysis product is used in the industrial plant. The electrolysis system is connected in particular to the industrial plant by gas cables for supplying hydrogen and/or oxygen. Alternatively, the electrolysis system can be used with the associated control unit for energy management of a stand-alone grid.
The object is also achieved according to the invention by an industrial plant having an energy management system according to one of the embodiments mentioned above. The industrial plant can be by way of example an open-pit mine, a plant in the semi-conductor or glass industries, a metal finishing plant or a plant for ammonia synthesis. By way of addition the oxygen produced in the electrolysis system can likewise be used for the process proceeding in the industrial plant. Alternatively, only the oxygen may be used in the industrial plant which is coupled to the electrolysis system.
A technological process proceeds in the industrial plant in which at least one electrolysis product, in particular hydrogen, generated in the electrolysis system of the energy management system is used. In addition to the production of substances, which are required for the process proceeding in the industrial plant, the energy management system is therefore also used for positive and negative regulation of performance in relation to the industrial plant.
The object is also achieved according to the invention by a method for operating an energy management system comprising an electrolysis system with an alkaline electrolysis unit and a PEM electrolysis unit, wherein the electrolysis units are controlled independently of one other with respect to an adjustment of an overall performance of the electrolysis system. Firstly a performance of the PEM electrolysis is preferably varied when adjusting the overall performance of the electrolysis system.
The advantages and preferred embodiments already listed in relation to the energy management system may be logically transferred to the industrial plant and the method.
An exemplary embodiment of the invention will be explained in more detail with reference to a drawing. The single FIGURE schematically shows an energy management system 2 based on an electrolysis system 6.
The FIGURE shows an energy management system 2 which is a component of an industrial plant which is schematically indicated by the block 4. The industrial plant 4 is a plant in the chemical, metallurgical or semi-conductor industry, by way of example a plant for producing electrical semi-conductor components, such as light emitting diodes.
The energy management system 2 comprises a hybrid electrolysis system 6 with an alkaline electrolysis unit 8 and a PEM electrolysis unit 10. The energy management system 2 also comprises a high-performance electronic device 12 for supplying energy and operational control, to which alternating current is supplied, indicated by the arrow 14. The high-performance electronic device 12 is composed for example of rectifier for the electrical current, transformer, gas analyzer and a safety device (none shown here). The high-performance electronic device 12 is in particular “smart grid” compatible.
A control unit 16 is also provided which separately controls or regulates the operating performances of the alkaline electrolysis unit 8 and the PEM electrolysis unit 10. The control unit 16 can also be integrated in the high-performance electronic device 12.
According to
The electrolysis system 6 with the associated controller therefore has two functions. Firstly hydrogen and/or oxygen is/are provided for the process proceeding in the industrial plant 4. This function of the electrolysis system 6 is fulfilled in particular by the alkaline electrolysis unit 8 which has a relatively high operating performance in the megawatt range and which is provided for an optimally constant mode of operation, wherein its performance range lies between 25% and 100% of its nominal performance.
The second function consists in energy management by way of suitable control or regulation of the electrolysis system 6 by way of the control unit 16. The electrical current 14 which is fed into the electrolysis system 6 exhibits fluctuations, and this can be expensive for the electricity users since the energy supply companies often use the most frequently demanded performances for pricing. The electrolysis system 6 is therefore designed for highly dynamic operation since the alkaline electrolysis unit 8 is supplemented by the PEM electrolysis unit 10 by way of which an overall performance of the electrolysis system 6 is adapted during operation. The PEM electrolysis unit 10 has a lower operating performance of a maximum of 0.5 MW in this exemplary embodiment but it may temporarily operate (in particular for several minutes) in overload mode, so its performance range is between 0% and 300% of the nominal performance.
In contrast to the alkaline electrolysis unit 8, in which a performance adjustment within the admissible performance range can last a few minutes, the PEM electrolysis unit 10 is distinguished by a particularly fast adaptation time which is conventionally below 30 s. Variations in the grid in the seconds and minutes range are therefore caught particularly efficiently by the PEM electrolysis unit 10 and used for increased production of hydrogen and oxygen. The operating performance of the PEM electrolysis unit 10 is accordingly reduced in phases in which high performance of the industrial plant 4 is briefly required, for example when starting up motors, so a passive provision of energy is made for operation of the industrial plant 4.
By combining the two electrolysis units 8, 10 a hybrid electrolysis system 6 is therefore created which is capable of avoiding the drawbacks of alkaline electrolysis by way of the advantages of PEM electrolysis.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11172385.4 | Jul 2011 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/062188 | 6/25/2012 | WO | 00 | 2/4/2014 |
