TECHNICAL FIELD OF THE INVENTION The present invention generally relates the buffering of electrical energy from an intermittent energy source. More specifically, the present invention relates to the optimizing of the efficiency of an electrical energy buffering with regard to use of inputs and outputs, environmental load, and buffering capacity. BACKGROUND OF THE INVENTION

Several of the renewable or sustainable energy sources available today are irregular in their supply, in particular if they depend directly on varying natural phenomena, such as wind and solar power. These energy sources commonly fail to deliver peak power when the demand is the highest It can even be the case that the peak power can be delivered when the demand for power is the lowest, e.g. wind power during night-time. Hence, there is need for a method to store the energy produced by an intermittent energy source. For example, a farmer owns a windmill and green-house that is heated electrically. At moder- ate to high wind speeds the windmill produces surplus electrical energy after heating the green-house. However, at low wind speeds the windmill does not produce sufficient energy for heating the green-house. However, at present there is no efficient method for locally store the surplus electrical energy and retrieve it later when there is a need.

There is a general problem in handling biological waste without contributing negatively to the environment, both locally and globally. Locally the degradation of biological waste can result disturbing odours, e.g. from pig manure. Globally the degradation of biological waste contributes to the green-house effect. In the presence of oxygen, the biological waste produces carbon dioxide, while in the absence of oxygen it produces methane, which is a much more efficient greenhouse gas than carbon dioxide If this degradation is not contained and controlled, the chemical energy intrinsic to the biological waste is lost. Further, there is a!so a need for a replacement of fossil fuels as a source for electrical energy production, as this is not a sustainable or environmentally friendly energy source There are a number of methods and systems for extracting energy from biological waste. However, they are limited in their overall efficiency, in particular with regard to utilizing also the surplus heat and rest products produced. A system for extracting energy in the form of hydrogen from biological waste is described in "Large Renewables - Hydrogen Energy Systems: Gathering and Transmission Pipelines for Windpower and other Diffuse, Dispersed Sources", by Leighty et a!., conference proceedings for World Gas Conference, 2003. The system is optimized for large scale energy transport, not local or regional energy buffering- Further, it lacks an overall energy balance taking the generated surplus heat and all residual outputs into account, thereby decreasing the over- all efficiency and buffering capacity of the system.

WO2005/005312 describes a system having the ability to function as a buffer for buffering electrical energy from the intermittent energy source by way of treating biological waste. However, the system is optimized for co-producing hydrogen and lacks an overall energy balance taking the generated surplus heat and the residual outputs from the biological waste into account. Hence, the system is not efficient with regard to the overall entropy, in particular to the residual outputs having a biological use or value.

OBJECTS OF THE INVENTION

An object according to the present invention is to ach Ιθνθ 3Π efficient buffering of electrical energy with a small negative effect, or even a positive overall ef- feet, on the environment Another object of the present invention is to achieve a high buffering capacity of an electrical energy buffering system. A particular feature of the present invention is a feedback or reuse of surplus heat within the electrical energy buffering system. One advantage with this feature is that a high efficiency of the electrical energy buffering system is achieved with regard to the the inputs of the system. A further object of the present invention is to achieve a high overall efficiency with regard to all the inputs and all the outputs of an electrical energy buffering system.

SUMMARY/DISCLOSURE OF THE INVENTION

In addition to the above objects, the above advantages and the above features, numerous other objects, advantages and features will be evident from the general and detailed descriptions given below of preferred embodiments according to the present invention The objects, advantages and features are according to a first aspect of the present invention obtained by a method for accumulating input electrical energy from an intermittent electrical energy source by an energy buffering plant having an input comprising the input electrical energy and biomass, and an output comprising output electrical energy and one or more fertilizers; the method comprising: placing the energy buffering plant at a location having a supply of the input and a demand for the output, collecting the input to the energy buffering plant, converting at least some of the input elec- trical energy and at least some of the biomass into stable chemical energy in a process further producing the one or more fertilizers, storing the chemical energy, converting at least some of the stored chemical energy to the output electrical energy, and distributing the output from the energy buffering plant. The intermittent electrical energy source may be a renewable energy source, such as a wind mill, solar cell, a hydropower plant, or a wave power plant. By nature, these energy sources are unstable. This allows for the proposed method to function as a carbon sink with regard to carbon dioxide in the atmosphere. The intermittent electrical energy source delivers the input electrical energy directly to the energy buffering plant, which allows for a plant that is independent of the local or national electrical power grid, and can therefore be placed in areas where no such grid is established. Alternatively, the energy buffering plant may be coupled to a local or national electrical power grid for in- put electrical power. This has the advantage that input electrical energy can be delivered from any intermittent electrical energy source coupled to the power grid. The energy buffering plant may be coupled to a local or national electrical power grid to delivers at least some of its output electrical power. This is favor- able for a low capacity or unstable power grid, as the buffering may be used for stabilizing the grid, for example in some developing nations where there is a ransoming of electricity. The energy buffering plant may be coupled directly to a local installation requiring electrical power, thereby allowing for a constant electrical energy supply from an isolated intermittent energy source alone.

The step of placing the energy buffering plant at a location having a supply of the input and a demand for the output may mean that plant is placed at a location where the input can be bought at an input cost being and the output can be sold at an output cost, where the input cost and output costs are approximately the same, or the latter larger than the former. The step of placing the energy buffering plant may also mean that the plant is placed at location where there is an easy access to the input and little or no access to the output; or the step may mean that the input can be acquired at a low price and the output sold at a high price. A producer of the biomass may even pay the plant for getting free of relieved from the biomass, in particular if it is an organic waste product, such as organic domestic waste.

The biomass may be wet biomass containing an amount of water to such degree that it is biodegradable on a seasonal basis, such as animal manure, waste water sludge, grass, organic matter from lakes or water courses, algae from the sea, biodegradable municipal solid waste, and harvested crop from farming. The biomass may be dry biomass containing a lesser amount of water such that it cannot degrade by biological process on a seasonal or yearly basis, for example wood chips and straw The dry biomass may also be produced from wet biomass that has been dried. The one or more fertilizers may be an organic fertilizer from the processing of the wet biomass, or an inorganic fertilizer from processing of the dry biomass. With the ability to use both wet and dry biomass, there is no requirement for changing the water contents of the biomass prior to its use in the process, which would otherwise add to the complexity of the method.

The stable chemical energy is stable in the sense that it is contained in a stable compound from which it can be extracted after accumulation and storage through chemical processes, such as oxidation.

The collecting of the input may comprise: collecting the input electrical energy at a first demand for or consumption of electrical power; and the distributing of the output from the energy buffering plant comprising: distributing the output electrical energy at second demand for or consumption of electrical power, the second demand or consumption being higher than the first demand or consumption. For example, the first and second demands may be determined by a power value, e.g. in the unit kW, representing the power consumed or needed to heat a greenhouse coupled to the energy buffering plant either directly or via a national grid.

The converting of at least some of the stored chemical energy to the output electrical energy may generate surplus heat, and at least some of the surplus heat may be employed in the converting of at least some of the input electrical energy and at least some of the biomass into stable chemical energy. This feedback will increase the efficiency of the method.

The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may generate intermediate surplus heat, and at least some of the intermediate surplus heat may be employed in the converting of at least some of the input electrical energy and at least some of the biomass into stable chemical energy. This feedback will further improve the efficiency of the proposed method,

The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise: dissociating water into oxygen and hydrogen in an electrolysis driven by employing the input electrica! energy and generating the intermediate surplus heat; the storing of the chemical energy may comprise: storing the hydrogen, and the converting of at least some of the stored chemical energy may comprise: consuming at least some of the stored hydrogen to generate at least some of the output electrical energy and at least some of the surplus heat.

The electrolysis may be of a single cell type with an anode and a cathode separated from one another to extract the hydrogen and the oxygen without mixing the two gases. The storing of the hydrogen may involve a compression of the gas and a subsequent storage in hydrogen tank. The consuming of the hydrogen may involve a micro-turbine in which the hydrogen is burnt to generate hot gases directly driving the fans of the turbine. The oxygen for the micro-turbine may be provided from the ambient air. The micro-turbine in turn drives an electrical generator to provide the output electrical energy as an alternating current. The consuming may also be in an internal combustion engine coupled directly to an electrical generator to generate the output electrical energy. Alternatively or additionally, the consuming may involve burning by oxygen from the ambient air to heat a boiler system generating the output electrical energy through a heated steam turbine coupled directly to an electrical generator.

Additionally or alternatively, the hydrogen may be consumed in at least one fuel cell. This way the output electrical energy is directly generated as a direct current. The direct current may be converted to an alternating current by an inverter Alternatively to the electrode electrolysis, the electrolysis may be achieved through proton exchange membrane electrolysis, or another "inverted" fuel cell technology.

The storing of the chemical energy may comprise: cooling the hydrogen by employing at least some of the surplus heat and/or at least some of the inter- mediate surplus heat. This allows for a storing of the hydrogen in liquid form, with a high overall efficiency of the energy buffering system. The hydrogen tanks may be isolated and also cooled to allow for the storing in liquid form The liquid hydrogen has the advantage of higher chemical energy density as compared to the gaseous form

The output may further comprise at least some of the stored hydrogen. The output hydrogen may be to a hydrogen grid for transporting the hydrogen over long distances, or for a local tapping, e.g. for refueling hydrogen powered vehicles.

The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise: subjecting at least some of the biomass to at (east some of the oxygen and to at least some of the surplus heat and/or at least some of the intermediate surplus heat for contributing to a partial oxidation of the biomass to produce synthesis gas; the storing the chemical energy may comprise: storing the synthesis gas; and the converting of at least some of the stored chemical energy may comprise: consuming at least some of the stored synthesis gas to generate at least some of the output electrical energy and at least some of the surplus heat The partial oxidation may produce heat that that also contributes to drive the gasification producing the synthesis gas. However, the supplied heat to the biomass will to some extent drive the oxidation process, which increases the overall efficiency of the system. The main constituents of the synthesis gas are usually hydrogen, carbon monoxide, and a smaller amount of methane. The gasification is particularly suitable for a dry biomass as described above, as a too high water contents can somewhat hinder the gasification process. The storing of the synthesis gas may be in a pressurized gas tank, or in a gas holder or bell. The consuming may involve burning by oxygen from the ambient air to heat a boiler system generating the output electrical energy through a heated steam turbine coupled directly to an electrical generator. The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise, controlling the partial oxidation of the biomass to further produce char; and the storing the chemical energy may comprise: storing the char; additionally, the converting of at least some of the stored chemical energy may comprise: consuming at least some of the stored char to generate at least some of the output electrical energy and at least some of the surplus heat; and/or the distributing of the output from the energy buffering plant may comprise, including at least some of the stored char in the one or more fertilizers. The char, or charcoal, is an organic product being similar to coke produced by gasification of bituminous coal or black coal broken from the ground. The controlling of the partial oxidation may vary depending on the type of biomass used. For example, one first type of biomass may require more oxygen than a second type of biomass having the same mass as the first mass. The controlling may relay on results of earlier test performed to achieve a certain type or amount of char from a specific type of biomass. The storing of the char may be in weather protected enclosed spacing, e.g. a shed. The consuming may involve burning by oxygen from the ambient air to heat a boiler system generating the output electrical energy through a heated steam turbine coupled directly to an electrical generator.

The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise: controlling the partial oxidation of the biomass to further produce tar; and the storing the chemical energy may comprise: storing the tar; additionally the converting of at least some of the stored chemical energy may comprise: consuming at least some of the stored tar to generate at least some of the output electrical energy and at least some of the surplus heat. The controlling of the partial oxidation may vary depending on the type of biomass used. For example, one first type of biomass may require more oxygen than a second type of biomass having the same mass as the first mass. The controlling may relay on results of earlier test performed to achieve a certain type or amount of tar from a specific type of biomass. The storing of the tar may be in an airtight container, e g. in a tank. The consuming may involve burning by oxygen from the ambient air to heat a boiler system generating the output electrical energy through a heated steam turbine coupled directly to an electrical generator. Further, the output may further comprise the tar. The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise: controlling the partial oxidation of the biomass to further produce nitrates; and the distributing of the output from the energy buffering plant may comprise: including at least some of the nitrates in the one or more fertilizers. The controlling may relay on results of earlier test performed to achieve a certain type or amount of nitrates from a specific type of biomass.

The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise: subjecting at least some of the biomass to microorganisms and to at least some of the surplus heat and/or at least some of the intermediate surplus heat for contributing to a biological breakdown of the biomass to produce biogas; the storing of the chemical energy may comprise: storing the biogas; and the converting of at least some of the stored chemical energy may comprise: consuming at least some of the stored biogas to generate at least some of the output electrical energy and at least some of the surplus heat. The biological breakdown and the production may be in a tank for containing and collecting the produced biogas. The storing of the biogas may be in a pressurized gas tank, or in a gas holder or bell The consuming may involve burning by oxygen from the ambient air to heat a boiler system generating the output electrical energy through a heated steam turbine coupled directly to an electrical generator. The microorganisms may primarily be anaerobic digesters producing primarily methane. This is typically achieved at elevated temperatures between 35-60 degrees C, which to some extent may be obtained by the heat supplied to the biomass. The microorganisms may also involve a certain amount of aerobic digesters to achieve a specific residual output more suitable as a fertilizer. A wet biomass as described above is particularly suitable for the biological breakdown, as the high water contents allows for the microorganisms thrive and spread.

The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise: controlling the biological breakdown of the biomass by subjecting the biomass to at least some of the oxygen generated in the electrolysis. The controlling of the biological breakdown may relay on results of earlier test performed to destroy at least some of the microorganisms in the biomass, e g, the anaerobic micro-organisms, that may be harmful,

The converting of at least some of the input electrical energy and of at least some of the biomass into stable chemical energy may comprise controlling the biological breakdown of the biomass to further produce an organic fertilizer; and the distributing of the output from the energy buffering plant may comprise: including at least some of the organic fertilizer in the one or more fertilizers. The controlling of the bioiogical breakdown may relay on results of earlier test performed to obtain an organic fertilizer of a specific type from a specific type of biomass. For example, an initial biological breakdown may be preformed to produce biogas. However, the residual biomass is not suitable as a fertilizer. By subjecting this residual to oxygen and an aerobic digestion, it may be suitable as an organic fertilizer.

The distributing of the output from the energy buffering plant may comprise: including at least some of the surplus heat and/or at least some of the interme- diate surplus heat in the output; and distributing the surplus heat and intermediate surplus heat in the output to remote heating. For example, the remote heating may be a heating of a greenhouse at the same location as the energy buffering plant Additionally or alternatively, the energy buffering may be coupled to a district heating system, to which at least some of its surplus and/or intermediate surplus heat is delivered.

Subsequent to the biological breakdown of the biomass, the electrolysis may be performed directly on the biomass to dissociate water contained therein into the oxygen and the hydrogen. As described above, the electrolysis may be of a single cell type with an anode and a cathode separated from one another to extract the hydrogen and the oxygen without mixing the two gases A current is allowed to go through the biomass between the anode and the cathode. This may generate an amount of heat sufficient to destroy microorganisms in the re- sidual biomass, thereby making it suitable as an organic fertilizer. Further, the electrolysis may also change the chemical composition of the biomass, thereby making it more favorable as a fertilizer. The wet biomass as described above is particularly suitable for the electrolysis, as the higher water contents allows for an efficient production of oxygen and hydrogen.

The objects, advantages and features are according to a second aspect of the present invention obtained by an energy buffering plant for accumulating input electrical energy from an intermittent electrical energy source having an input comprising the input electrical energy and biomass, and an output comprising output electrical energy and one or more fertilizers, the energy buffering plant being placed at a location having a supply of the input and a demand for the output and comprising: an input collector to collect the input to the energy buffering plant; an input converter to convert at least some of the input electrical energy and at least some of the biomass into stable chemical energy in a process further producing the one or more fertilizers; an accumulator to store the chemical energy; an output converter to convert at least some of the stored chemical energy to the output electrical energy; and an output conveyer to distribute the output from the energy buffering plant.

The energy buffering plant may comprise: analysis means (30) to determine the demand for or consumption of electrical power, a regulator to control the input collector and the output conveyor to collect the input electrical energy at a first demand for or consumption of electrical power, and to distribute the output electrical energy at a second demand for or consumption of electrical power, where the second demand or consumption being higher than the first demand or consumption. The output converter may generate surplus heat that is conveyed to the input converter, and the input converter may be adapted to employ at least some of the surplus heat in converting at least some of the input e!ec- trical energy and at least some of the biomass into stable chemical energy.

The input converter may generate intermediate surplus heat that is conveyed internally in the input converter to employ at least some of the intermediate surplus heat in converting at least some of the input electrical energy and at least some of the biomass into stable chemical energy.

The input converter may comprise: an electrolyser to dissociate water into oxy- gen and hydrogen in an electrolysis driven by employing the input electrical energy and generating the intermediate surplus heat, the accumulator may comprise; a hydrogen tank to store the hydrogen; and the output converter may comprise; a first electrical energy producer to generate at least some of the output electrical energy and at least some of the surplus heat by consuming at least some of the stored hydrogen

The first electrical energy producer may comprise a fuel cell to consume at least some of the stored hydrogen. The accumulator may comprise: a cooler to cooi the hydrogen by employing at least some of the surplus heat and/or at least some of the intermediate surplus heat. The output conveyer further may comprise a hydrogen outlet to include at least some of the stored hydrogen in the output.

The input converter may comprise, a gasifier to subjecting at least some of the biomass to at least some of the oxygen and to at least some of the surplus heat and/or at least some of the intermediate surplus heat for contributing a partial oxidation of the biomass to produce synthesis gas; the accumulator may comprise: a synthesis gas tank to store the synthesis gas; and the output converter may comprise: a second electrical energy producer to generate at least some of the output electrical energy and at least some of the surplus heat by consuming at least some of the stored synthesis gas

The gasifier may comprise: a first oxygen supply controller to control the partial oxidation of the biomass to further produce char; and the accumulator may comprise: a solid storage to store the char; additionally the second electrical energy producer may further be adapted to generate at least some of the output electrical energy and at least some of the surplus heat by consuming at least some of the stored char, and/or the output conveyor may further comprise a char outlet to include at least some of the stored char in the one or more fertilizers.

The gasifier may comprise: a second oxygen supply controller to control the partial oxidation of the biomass to further produce tar; and the accumulator may comprise a liquid tank to store the tar, additionally the second electrical energy producer may further be adapted to generate at least some of the output electrical energy and at least some of the surplus heat by consuming at least some of the stored tar, and/or the output conveyor may further comprise a tar outlet to include at least some of the stored char in the output

The gasifier may comprise: a third oxygen supply controller to control the partial oxidation of the biomass to further produce nitrates; and the output conveyor may be adapted to including at least some of the nitrates in the one or more fertilizers.

The input converter may comprise: a biogas producer to subject at least some of the biomass to microorganisms and to at least some of the surplus heat and/or at least some of the intermediate surplus heat for contributing to a bio- logical breakdown of the biomass to produce biogas; the accumulator may comprise: a biogas tank to store the biogas; and the second electrical energy producer may further be adapted to generate at least some of the output electrical energy and at least some of the surplus heat by consuming at least some of the stored biogas.

The biogas producer may comprise: a fourth oxygen supply controller to control the biological breakdown of the biomass by subjecting the biomass to at least some of the oxygen generated in the electrolysis. The fourth oxygen supply controller may be adapted to control the biological breakdown of the biomass to further produce a an organic fertilizer; and the output conveyor may be adapted to including at least some of the organic fertilizer in the one or more fertilizers. The output conveyor may be adapted to include at least some of the surplus heat and/or at least some of the intermediate surplus heat in the output and to distribute it to a remote heating. The electrolyser and the biogas producer may be adapted to subsequent to the biological breakdown of the biomass performed the electrolysis directly on the biomass to dissociate water contained therein into the oxygen and the hydrogen All the features described in relation to the first aspect of the present invention may be included in the second aspect of the present invention. The effects and advantages of a particular feature described in relation to the first aspect of the present inventions are also relevant for the corresponding feature of second aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and features according to the present invention will be more readily apparent from the following detailed description and the drawing.

Fig, 1 being a schematic view of a preferred embodiment of a system according to the second aspect of the present invention for performing a process according to the method of the first aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The system shown in Fig.1 is a schematic illustration of the energy buffering plant 10 according to the present invention. The energy buffering plant 10 has an input collector 12 through which water 40, input electrical energy 22, wet biomass 24, and dry biomass 25 are distributed to the input converter 14 of the plant 10, The input converter is defined by an electrolyser 38 receiving the wa- ter 40 and the input electrical energy 22, a biogas producer 78 receiving the wet biomass 24, and a gasifier 56 receiving the dry biomass 25, The electrolyser 38 produces hydrogen 44 and oxygen 42 from the water 40 and the input electrical energy 22. The biogas producer 78 produces a biogas 79 from the wet biomass 24, while the gasifier 56 produces synthesis gas 57 from the dry biomass 25.

The oxygen 42 produced by the electrolyser 38 available to the biogas producer 78 to allow a control of the production of its output.. This output also com- prises organic fertilizers 84 and inorganic fertilizer 86, or raw-materials for the latter. Naturally, the properties of the fertilizers 84 and 86 depends on the amount of oxygen 42 used by the biogas producer 78 and the nature of the wet biomass 24, The biogas 78 primarily consists of methane. The oxygen 42 produced by the electrolyser 38 available to the biogas producer 78 is also used in the gasifier 56 to control the partial oxidation of the dry biomass 25, which produces the synthesis gas. 57primarily consisting of hydrogen, carbon monoxide, and a smaller amount of methane The electrolyser also produces intermediate surplus heat 36, of which is led to the biogas producer 75 and the gasifier 56. In the biogas producer 78 the heat is used to obtain a favourable temperature of the biomass 24 for the biode- grading microorganisms to produce biogas, typically in the range 35-60 degrees C. In the gasifier 56 the heat is used to increase the temperature of the biomass 25 to drive out combustible volati!es and tar 72 from the biomass. The partial oxidation will then further produce combustible volatiles. The synthesis gas 57 is the extracted from the combustible volatiles. After the partial oxidation the solid residual of the biomass is in the form of char or charcoal 70 that can be used soil improver to increase the carbon contents of the soil. Some of the char is further oxidized to produce nitrates 76.

The biogas producer is provided with a fourth oxygen supply controller 82 to control the biological breakdown of the wet biomass by regulating the amount of oxygen 42 supplied The gasifier is provided with a first oxygen supply controller 62 to control the production of char 70, a second oxygen supply controller 66 to control the production of tar 72, and a third oxygen supply controller 74 to control the production of nitrates 76 by regulating the supply of oxygen 42 from the electrolyser 38 during the different stages of the gasification. For example, the supplied oxygen level may be such that a significant amount of tar will oxidize before it can be extracted.

The hydrogen 44, the biogas 79 and the synthesis gas 57 is lead to an accu- mulator 16. The accumulator 16 has a cooled high-pressure hydrogen tank 46 for storing the hydrogen 44 produced by the electrolyser 38 as liquid. The cooling is obtained by a cooler 52 driven by some of the heat 36 from the electrolyser 38. The accumulator 16 also has a medium-pressure gas tank 58 for receiving both the combined biogas 79 and synthesis gas 57, a solid storage 64 in the form of a shed for storing the char 70, and a liquid container 68 for storing the tar 72. The hydrogen 44, biogas 79, synthesis gas 57, char 70, and tar 72 together define the stable chemical energy available as an energy buffer.

Some of the stored hydrogen 44 and the biogas 79 and synthesis gas 57 mix- ture is lead to an output converter 18. The output converter 18 has a first electric energy producer 48 in the form of a micro-turbine connected to a generator to convert the chemical energy of the hydrogen 44 into output electrical energy 26. Further, the output converter 18 has a second electric energy producer 60 in the form of a gas and solid burner consuming the biogas 79 and synthesis gas 57 mixture, at least some the char 70, and at least some of the tar 72 to heat a boiler giving a pressurized steam driving a turbine connected to a generator to yield output electrical energy 26 in addition to that produced by the first electric energy producer 48, The surplus heat 34 from the first 48 and second 60 electrical energy producers is collected and lead back to the cooler 52, the biogas producer 78, and the gasifier 56,

The biogas producer 78 and the electrolyser 38 are adapted 90 so that an electrolysis can be performed on the biomass after the biological degradation This produces additional oxygen 42 and hydrogen 44, as well as increasing the temperature and changing the chemical composition of the biomass. The temperature is increased to such a level that harmful microorganisms are destroyed, e g, to 80 degrees C. The biomass is then extracted as an organic fer- tilizer 84. The electrolysis can also be performed for such a period of time so that the biomass is turned into an inorganic fertilizer 86, with little or substantially no biological material left.

The hydrogen 44 can be extracted through a hydrogen outlet 54 to fill hydrogen flasks. The output electrical energy 26 can be extracted through a connection or outlet 26 to the national grid. There is also a connection through which 88 some of the surplus heat 34 and 36 can be extracted via a heat exchanger to a district heating tubing. The organic fertilizer 84, inorganic fertilizer 86, char 70, and/or nitrates 76 all define one or more fertilizers 28. The energy buffering system 10 has an output conveyor defined by the outputs for the one or more fertilizers 28, the hydrogen 65, the output electrical energy 26, the heating 88 and the tar 72.

The energy buffering plant 10 is provided with analysis means 30 able to de- termine and register the electrical power consumed by the national grid. A regulator 32 control the input collector 12 and the output conveyor 20 to collect the input electrical energy 22 at a first demand consumption of electrical power, and to distribute the output electrical energy 26 at a second consumption of electrical power, where the second consumption is set to be higher than the first consumption.

The arrows in Fig.1 indicate the direction in which the associated heat, gas, input, or output is conveyed, ITEM LIST

10 energy buffering plant

12 input/input collector

14 input converter

16 accumulator

18 output converter

20 output/output conveyor

22 input electrical energy

24 biomass

26 output electrical energy

28 fertilizers

30 analysis means

32 regulator

34 surplus heat

36 intermediate surplus heat

38 electrolyser

40 water

42 oxygen

44 hydrogen

46 hydrogen tank

48 first eiectrical energy producer

50 fuel cell

52 cooler

54 hydrogen outlet

56 gasifier

57 synthesis gas

58 gas tanks

60 second eiectrical energy producer 62 first oxygen supply controller 64 solid storage

66 second oxygen supply controller 68 liquid tank 70 char

72 tar

74 third oxygen supply controller 76 nitrates

78 biogas producer

79 biogas

82 fourth oxygen supply controller 84 organic fertilizer

86 inorganic fertilizer

88 remote heating

90 biomass water