SE1950081A1

SE1950081A1 - Method and system for storing electrical energy in the form of heat and producing a power output using said heat

Info

Publication number: SE1950081A1
Application number: SE1950081A
Authority: SE
Inventors: Joachim Karthäuser
Original assignee: Climeon Ab
Priority date: 2019-01-23
Filing date: 2019-01-23
Publication date: 2020-07-24
Also published as: WO2020153896A1

Abstract

The invention relates to a system for storing heat energy and generating a power output in the form of electricity using said heat. Said system comprising a heat power module (1) operating in accordance with a thermodynamic closed loop cycle process (RC) to generate a first power output (E1) from heat input (HSin) from a geothermal well, a receiver (2) for receiving said first power output (E1) and a second power output (E2) generated by at least one additional intermittent energy source (ES2) selected from solar photovoltaics, wind power, biogas electrification or other renewable energy source arranged to intermittently generate electricity. The system also comprises an electricity control system (3) controlling and distributing said first power output (E1) and second power output (E2) externally to the grid, at least one flow control system (4) arranged to distribute the flow of a geothermal medium heated by said geothermal heat (HS) in the geothermal well and a controller (5). Said controller (5) is arranged to direct the flow control system (4) to regulate the geothermal medium to i) be distributed from the geothermal well to a first thermal storage system (6) when a second power output (E2) is received, and ii) be distributed from said first thermal storage system (6) to be used as heat input (HSin) to the heat power module (1) mainly when a second power output (E2) is not received. The invention also relates to a method for storing electrical energy in the form of heat and producing a power output using said heat.

Description

METHOD AND SYSTEM FOR STORING ELECTRICAL ENERGY IN THEFORM OF HEAT AND PRODUCING A POWER OUTPUT USING SAIDHEAT Field of The InventionThis invention relates to the field of power generation, and storage of energy and electricity.

Background and Prior ArtEnergy sources, especially solar and wind, are intermittent. Electricity demand is also variable, see e.g. yxfxvxvgenergsf-charts.cle/poyverhtin . Therefore, it is desirable to store electricity, e.g. in chemical form through electrolytic hydrogen produc-tion, in batteries, ﬂywheels, magnetic technologies, in pumped hydro storage orin the form of compressed air. This enables the production of electricity at timesof high demand, also referred to as “peak shaving” or “time shifting”. An overviewof various storage technologies is found at vnfwæxnsandíangoﬂf, wvtfxw.store-aaroušectrsii, xvxvxfvpurdrieaedu, xvxfvvvireiiarurg. Said references also discuss typical capital and operational costs of the various techniques, as well as application examples, en- ergy densities, round-cycle efficiencies, energy and effect ranges etc.

The invention deals specifically with energy storage in the form of hot water. Thefollowing patent disclosures give an impression of the general art: US 9331 547 (L. Bronicki, Ormat Technologies) describes an elegant hybrid geo-thermal power plant where photovoltaic modules and a geothermal Rankine cyclecooperate in order to match electricity production and demand.

US 7178 337 by Tassilo Pﬂanz describes a geothermal storage method utilizing acompressed gas energy storage system.

WO 2018 102 265A1 by J. King et al. (Combined Power LLC) describes a com- bined geothermal and concentrated-solar-power system which is able to store en- ergy.

US 7566 980 by G. Fein (Genedics), US 8005 640 by D. Chiefetz describe the gen-eral art, the latter disclosure describing a test system utilizing heat and powerpulses for testing geothermal reservoirs.

US 37 57 516 by B. McCabe (Magma Energy) gives a general historic overview over low temperature thermodynamic cycles in geothermal power plants.

The general technology to store excess electricity as heat, with possibility to re-cover at least part of the electricity through a thermodynamic cycle, is being re- ferred to as “Carnot battery”, see https:I/'iea-eces.org/everits/iifiternatíonal-ifvork- sliop-on-carnot-'batteriesﬂ Heat at any temperature between 100 and 800 °C may be generated directly with resistive heating or by using a heat pump, and theheat may be stored in any medium including hot water (see Climeon WO2017065683A1), molten salt (Google / Malta proposal), or vulcanic stones (Siemensproposal). Heat and cold may be stored in separate containers. Typically, theround-trip-efficiency (RTE = output electricity / input electricity) is determinedby the Coefficient of Performance (COP) of the heat pump and the practical ther-modynamic efficiency of the thermodynamic cycle, and it is usually in the order of -50%.

The prior art does not provide economically attractive methods to store excesselectricity in the form of heat and allowing to generate electricity from said heat at a temperature range of 70-120 °C at times of peak electricity demand.

Object of The InventionThe object of the invention is to provide a method and a system for storing energy and producing electricity with a high efficiency and profitability.

The object of the invention is to provide a method and a system for storing energyand producing electricity with a high cycle turnaround efficiency, i.e. electricalenergy produced by the Rankine Cycle (RC) divided by the electrical energy con-sumed by the device generating heat, >50%, >7 0% and even >90%. The method is lO preferably used for storing and time-shifting intermittent renewable electricityfrom solar and wind power at a scale above 1 MWh and a power effect of 150 kW and above, and it can be used to store any electricity.

The object of the invention is to provide a method and a system for storing energyand producing electricity wherein the method and system is used for quickly, i.e. on the scale of less than one minute, regulating power demand in the grid.

The object of the invention is to provide a method and a system for storing energyand producing electricity wherein full and phase- and frequency-matched power is supplied at within less than one minute.

Summary of The Invention The present invention relates to a system for storing heat energy and generatinga power output in the form of electricity using said heat. Said system comprises aheat power module comprising a turbine generator arranged to generate a firstpower output in the form of electricity. Said heat power module is operating inaccordance with a thermodynamic closed loop cycle process being arranged to re-ceive heat input from a geothermal well, wherein said well is functioning as firstcontinuous energy source of geothermal heat, and a cold input from a cold sourcefor phase change of a working medium. The system also comprises a receiver forreceiving said first power output and a second power output generated by at leastone additional intermittent energy source selected from solar photovoltaics, windpower, biogas electrification or other renewable energy source arranged to inter-mittently generate electricity. Additionally, the system comprises an electricitycontrol system controlling and distributing said first power output and secondpower output eXternally to the grid, at least one flow control system arranged todistribute the flow of a geothermal medium heated by said geothermal heat inthe geothermal well and a controller in electrical communication with said one ormore receiver, the electricity control system and the flow control system, wherein said controller is configured to direct said electricity control system and flow lO control system to regulate electricity distribution and geothermal medium flowand distribution. The system is characterised by that said controller is arrangedto direct the flow control system to regulate the geothermal medium to i) be dis-tributed from the geothermal well to a first thermal storage system when a sec-ond power output is received by the receiver and ii) be distributed from said firstthermal storage system to be used as heat input to the heat power module mainlywhen a second power output is not received by the receiver, wherein said heat power module generate said first power output.

When using this method the electricity production is controlled so that the heatpower module electricity production is mainly active when the renewable addi-tional intermittent energy sources are not active to produce electricity, and viceversa, so that electricity from the renewable additional intermittent energysources is stored in the form of geothermal heat in said heat storage tank, and electricity production for the grid can be time-shifted to meet public demand.

In one embodiment, said controller is arranged to direct the electricity controlsystem to distribute selected electricity to operate a geothermal pump arrangedto generate a flow of geothermal medium, wherein the selected electricity is the first power output, the second power output or output generated by the grid.

In one embodiment the receiver is also arranged to detect required power de-mand from the grid. The selected electricity to operate the geothermal pump isthe second power output, when the second power output or the total system power output eXceed the detected required power demand from the grid.

Pumping geothermal medium from a well is power consuming and may at someground conditions be so high that it is difficult to for the heat power module to de-liver more power output that power input needed to operate the pump. However,when the energy source selected to deliver the pump power depend on the amount of energy each energy source delivers at that time or at what price electricity is sold the operational efficiency can be improved. For example, duringa time period, when wind or solar procedure more electricity than the demand orwhen electricity is sold at a lower price, said electricity is used to pump hot geo-thermal medium, e.g. at 90 °C, to said first thermal storage. During a later timeperiod, when electricity is in demand or more expensive, the hot geothermal me-dium is used to generate electricity by the heat power module. Thus, renewableelectricity not required by the market is predominantly used for pump system op- eration.

In one embodiment the system also comprises a first thermal storage system andwherein said first thermal storage system comprises at least one first thermal storage tank arranged below or above ground.

Said first thermal storage system is preferably selected to be able to store liquidmedium having the temperature range 70-140 °C, preferably at below 100 °C and to maintain said temperature within said range.

In one embodiment said heat storage tank has a volume of at least 50 m3 and/oris large enough to generate a flow of geothermal medium to the heat power mod- ule for at least 2 hours of electricity production, preferably at least 4 hours.

In one embodiment said first thermal storage tank is used as a district heating tank or a reservoir.

In one embodiment said first thermal storage tank is a combined storage tankadapted for a layered storage of geothermal medium from the hot source and/orcooling medium from the cold source, wherein the medium is stored in layers ac- cording to density and temperature.

The hot storage medium and the cold storage medium may comprise preferablywater or geothermal brine, optionally physically decoupled through heat ex- changers.

In one embodiment the first thermal storage system comprises a second thermalstorage tank arranged to store the geothermal medium eXiting the heat power module at a temperature below said first temperature interval.

In one embodiment the system also comprises a second thermal storage systemand wherein said second thermal storage system arranged to store the cooling medium from the cold source.

In one embodiment the geothermal pump system and the heat power module areselected to create an energy system operating at a COP of least 10, i.e. one unit ofelectricity supplied to the geothermal pump produces at least 10 units of heatand later at least 10 units of electricity generated by said heat in said heat power module.

The system is simple and economic as storage of hot water or hot liquid is inex-pensive. Provided that the geothermal pump produces at least 10 units thermalenergy in the range 80-100 °C using one unit electrical energy supplied to thepump, electrical energy stored in the form of thermal energy can be recovered to 100%.

In one embodiment the heat power module is utilizing an Organic Rankine Cycleto generate electricity, wherein said Organic Rankine Cycle is operating with aheat input of 70-140 °C, a cold input between 0-30 °C and a net efficiency for conversion of heat to power of at least 5%.

Thus, said heat input of the hot source are from a geothermal medium having atemperature within a first temperature interval. Preferably said first tempera- ture interval are temperatures between 70-140 °C, preferably below 100 °C, In one embodiment the system also comprises at least one additional intermit-tent energy source selected from solar photovoltaics, wind power, biogas electrifi-cation or other renewable energy source arranged to intermittently generate elec- tricity.

An additional intermittent energy source of that kind typically requires interme-diate and temporary storage for 1-120 hours, preferably 4-12 hours, to optimizeits power output. The temporary storage is solved by the system according to theinvention. Said additional intermittent energy source may preferably be locatedin immediate proximity to first continuous energy source, thus the geothermalwell and may share certain components such as high voltage connection infra-structure, or where said electricity sources are geographically apart, but linked through the grid.

The invention also relates to a method for storing electrical energy in the form ofheat and producing a power output using said heat. Said method comprising thesteps: - generating a first power output in the form of electricity from a first con-tinuous energy source in the form of geothermal heat power by using a heatpower module comprising a turbine generator arranged to generate a first poweroutput in the form of electricity, wherein said heat power module operating in ac-cordance with a thermodynamic closed loop cycle process being arranged to re-ceive heat input from a geothermal well, functioning as first continuous energysource of geothermal heat and a cold input from a cold source for phase change ofa working medium, - receiving said first power output and a second power output generated by at least one additional intermittent energy source selected from solar lO photovoltaics, wind power, biogas electrification or other renewable energy sourcearranged to intermittently generate electricity, - controlling and distributing said first power output and second power out-put externally to the grid, - distributing the flow of a geothermal medium heated by said geothermalheat in the geothermal well, - directing said electricity control system and flow control system to regu-late electricity distribution and geothermal medium flow and distribution, theflow control system is directed to regulate the geothermal medium to - be distributed from the geothermal well to a first thermal storage systemwhen a second power output is received by the receiver, and - be distributed from said first thermal storage system to be used as heatinput to the heat power module mainly when a second power output is not re-ceived by the receiver, wherein said heat power module generate said first power output.

In one embodiment, the electricity control system is directed to distribute se-lected electricity to operate a geothermal pump arranged to generate a flow of ge-othermal medium, wherein the selected electricity is the first power output, the second power output or output generated by the grid.

In a further embodiment the required power demand from the grid is detected inthe detection step, and wherein the selected electricity to operate the geothermalpump is the second power output when the second power output or the total sys- tem power output eXceed the detected required power demand from the grid.

In another embodiment the geothermal pump is controlled to be operated at vari-able speed depending on the power output from the first continuous energy source and the additional intermittent energy source.

In another embodiment, the geothermal pump is controlled to be operated at es-sentially the same speed, possibly with +/- 10% variations, over extended periods of time.

In another embodiment said method also comprises the step of: - selecting the geothermal pump and the heat power module to create anenergy system operating at a COP of at least 10, i.e. one unit of electricity sup-plied to the geothermal pump produce at least 10 units of electricity generated by heat in said heat power module, shifted in time.

Said method or system according to the above is preferably to be used as a bat-tery for storage of electricity at a capacity scale of 1 MWh electricity and above and a power rating of 150 kW peak electricity and above.

Brief Description of The Drawings Fig. 1a and 1b show the general first and a second system according to the inven-tion.

Fig. 2a and 2b show schematic view illustrating the system and working princi-ple of an exemplary heat power module utilizing the phase change energy of aworking medium produced in a thermodynamic cycle process RCP.

Fig. 3 shows a schematic view of time-shifting electricity production from renewa-ble energy (RE) using a geothermal well and a pump which is operated at 50-100% of nominal load during the day.

Fig. 4 shows data from Fig. 3 in graphical form.

Fig. 5 is a table similar to Fig. 3, but with constant operation of the geothermalpump.

Fig. 6 shows COP 20 geothermal unit, capable of time-shifting intermittent re-newable energy production over the day.

Fig. 7 shows storage of 120 a.u. wind energy in geothermal heat storage, andtime-shifted electricity production with 100% turnaround efficiency with a COP10 geothermal well.

Fig. 8 shows a graphical representation of Fig. 7.

Detailed Description The Rankine cycle is an idealized thermodynamic cycle of a heat engine that con-verts heat into mechanical work. An Organic Rankine cycle (ORC) is a Rankinecycle using other Working fluids than water / steam, in particular organic fluids.Moreover, in the present invention, the term “ORC” is meant as any power gener-ation process capable of converting 50-150 °C heat streams to electricity. The ap-plicant uses the process termed “Heat Power” as described in WO 2012/ 128 715and SE 2013 / 051 059, PCT SE 1800 576-4, SE 1400 027-7 and SE 1400 160-6,and WO 2015/112 075 and PCT SE 2015/050 368, and SE 1400 514-4, and re-lated documents in the patent families, all hereby incorporated by reference. Es-sentially, the heat power module is a particularly efficient power generation sys-tem operating at low pressures and capable of utilizing heat of low temperatures,e.g. 70-120 °C, for power generation. Other ORC processes may be used as wellin the embodiments of the present invention.

The invention relates to a system and method which allow the reversible storage of electricity at a scale exceeding 1 Megawatt-hour (MWh).

Fig. 1a shows the general system for storing heat energy and producing electric- ity using said heat according to a first embodiment of the invention.

The system according to the first embodiment comprises at least one heat powermodule 1 comprising a turbine generator 300, 400 arranged to continuously gen-erate first power output E1 in the form of electricity. The system also comprises areceiver 2 for receiving said first power output E1 and a second power output E2,wherein said second power output E2 is generated by at least one additional in-termittent energy source ES1 selected from solar photovoltaics, wind power, bio-gas electrification or other energy sources arranged to intermittently generateelectricity. The system also comprises an electricity control system 3 controlling and distributing said first power output E1 and second power output E2 lO 11 externally to the grid as Well as at least one flow control system 4 arranged todistribute the flow of a geothermal medium heated by said geothermal heat HS in the geothermal well.

The flow is generated by an electricity powered geothermal pump 7. The systemmay also comprise a system of pipes and valves connecting the pump 7 with theheat power module 1 and the first thermal storage system 6. The geothermal me-dium is distributed to and from said first thermal storage system 6 by said sys- tem of pipes and valves controlled by signals sent by the flow control system 4.

The system also comprise a controller 5 in electrical communication with said oneor more receiver 2, the electricity control system 3 and the flow control system 4.Said controller 5 is configured to direct said electricity control system 3 and flowcontrol system 4 to regulate electricity distribution and geothermal medium flowand distribution. The controller 5 may comprising a processor and a non-transi-tory computer-readable medium, configured to store instructions, which when ex-ecuted by the processor, causes the controller to receive said instructions fromthe electricity control system 3 and the flow control system 4 and to generate a signal to distribute electricity and medium flow accordingly.

Preferably the geothermal medium is distributed to flow from the geothermalwell to the first thermal storage system 6 when the least one additional intermit-tent energy source ES2 is generating a power output EZ and to flow from said firstthermal storage system 6 to be used as heat input HSin to the heat power module1 mainly when the least one additional intermittent energy source ES2 is not generating a power output EZ.

Said geothermal medium is controlled to be distributed on the basis of mainly thefollowing input parameters, a) amount of generated electricity by the additionalintermittent energy source ES2, b) available heat input HSin stored in said first thermal storage system 6, c) power demand of the geothermal pump 7, and d) 12 marked required first power output El from said first continuous energy source ES1.

The electricity control system is arranged to distribute power to a geothermalpump 7 either from the intermittent energy source ES2 and/or from the heat power module 1 and/or from the grid.

In one embodiment the receiver 2 also detect signals about the present requiredpower demand from the grid. The power demand varies over the day, see for ex-ample Fig. 4. When the second power output E2 or the total system power outputE1+E2 eXceed the required power demand from the grid the selected electricity tooperate the geothermal pump 7 is the second power output E2. Detection ofpower demand from the grid is possible e.g. by detecting changes in the frequency of the grid, i.e. deviations from e.g. 50 or 60 Hz.

The system may also include said at least one additional intermittent energysource ES2. However, the system may also be connected to an already existing power plant producing energy from said additional intermittent energy sourceES2.

The first thermal storage system 6 comprises at least one first thermal storagetank 6A arranged below or above ground. The system for storing heat energy maybe connected to or include said first thermal storage system 6. Said first thermalstorage system 6 is preferably selected to be able to store liquid medium havingthe temperature range 70-140 °C, preferably at below 100 °C and to maintainsaid temperature within said range. The heat storage tank 6A preferably has avolume of at least 50 m3 and/or is large enough to generate a flow of geothermalmedium to the heat power module for at least 2 hours of electricity production, preferably at least 4 hours. 13 The heat storage tank 6A may also be at least 100 m3, 1000 m3, 10 000 m3 or atleast 100 000 m3. For storages of at least 5 000 m3, the storage tank may be aheat storage tank/reservoir as used in the district heating industry. Underground caverns are suitable reservoirs for both heat and cold storage.

The heat power module 1 is arranged to continuously generate first power outputEl in the form of electricity. Said heat power module operating in accordancewith a thermodynamic closed loop cycle process RCP being arranged to receiveheat input HSin from a geothermal well, functioning as first continuous energysource ES1 of geothermal heat HS, and a cold input CSin from a cold source CS.The heat and cold input is used for phase change of a Working medium. The hotsource is geothermal well comprising a geothermal medium and the cold sourcemay for example be a cooling tower, radiator, a large water body (from a nearbyriver, lake or sea) or underground well. The heat power module 1 is further de- scribed in Fig. 2a and 2b.

In one additional embodiment of the invention, the hot side heat exchanger of theheat power module 1 is kept at an operational temperature by circulating hot wa-ter through said hot side heat eXchanger and by idling the heat power module,and where after the heat power module may be started up within less than oneminute to provide full and phase- and frequency-matched power supply. Moreo-ver, the cycle turnaround efficiency, i.e. electrical energy produced by the heatpower module divided by the electrical energy consumed by the heat pump, is at least 50%.

Fig. 1b shows the general system for storing heat energy and producing electric-ity using said heat according to a second embodiment of the invention. The gen-eral system is similar as the system in Fig. 1a however here additional thermal storage systems have been added. lO 14 In this second embodiment the first thermal storage system 6 also comprises asecond thermal storage tank 6B arranged to store the geothermal medium exitingthe heat power module. I.e. at a temperature below said first temperature inter-val. Further, the system in Fig. lb also comprises a second thermal storage sys-tem 8. The second thermal storage system 8 is arranged to store the cooling me- dium from the cold source CS.

Moreover, the cold second thermal storage system 8 and/or the hot first thermalstorage system 6 may either comprise two separate storage tanks or a combinedstorage tank. The combined storage tank may be a stratified tank which mayhave a separating layer such as a floating separating layer. In a combined stor-age tank, the colder storage medium is collected at the bottom and the hot stor-age medium is collected at the top of the combined storage due to difference in densities of the cold and warm media.

Thus, the complete system is providing electrical energy partly by continuouselectrical energy from heat power and generated in the heat power module andpartly by intermittent electrical energy from wind power or solar power. The pur-pose of the system is to store especially intermittent energy until such time when electrical energy is needed by a utility or customers.

Fig. 2a shows a schematic view illustrating the working principle of an exem-plary heat power module. Said power generation module is arranged to convertlow temperature heat into electricity by utilizing the phase change energy of aworking medium produced in a thermodynamic cycle process RCP. The thermo-dynamic closed loop cycle may be a Rankine cycle, Organic Rankine Cycle, Kalinacycle or any other known thermodynamic closed loop power generating processes converting heat into power.

The heat power module of the invention is arranged to continuously generate thermal power output in the form of electricity by a thermodynamic closed loop cycle process utilizing the temperature difference between a heat input of a hotsource and a cold input from a cold source. Said hot source HS is a geothermalmedium flow from a geothermal well. The heat power module is cooled by a cool-ing medium flow which may come from a cold source CS in the form a coolingtower, radiator, a large water body (from a nearby river, lake or sea) or under-ground well. The temperature of the cooling flow entering the heat power moduleis within a second temperature interval of 0-30 °C, preferably 5-20 °C. The tem-perature of the cooling medium when eXiting the heat power module is preferably20-40 °C. The cooling medium may circulate in a closed loop. The hot storage me-dium and the cold storage medium may comprise preferably water or geothermal brine, optionally physically decoupled through heat eXchangers.

The power generation module comprises a turbine 800, a generator 400, a hotsource heat exchanger 200, a condensation device 500, for example in the form ofa cold source heat exchanger, and a pump 600, and a working fluid is circulatedthrough the module. The working fluid is heated in the hot source heat eXchanger200, also called evaporator, to vaporisation by an incoming hot source HSin, e.g.the hot geothermal fluid. The hot gaseous working fluid is then passed throughthe turbine 300 which drives the generator 400 for production of electrical en-ergy. The expanded hot working fluid, still in gaseous form, is then fed into thecondensation device 500 to be by the cold input from the cold source CSin, con-verted back to liquid form before being recirculated to the hot source heat ex-changer 200 to complete the closed-loop cycle 100, as shown on the left-hand sideof Fig. 2a. Thus, the condensation of the working medium takes place directly inthe cold source heat exchanger 500 which then can be said to be the condensationdevice. In this embodiment, the stream of liquid medium Q may be pumped di- rectly back to the hot source heat eXchanger 200 by the pump 600.

The condensation device may in one embodiment, as illustrated in Fig. 2b, 1 be a separate vessel 100 or container 100 and a cold source heat exchanger 500. 16 Examples Example 1 In one embodiment, hot Working fluid is produced from a geothermal Well using a pump to pump geothermal fluid. Figs. 3 and 4 give schematic details: Fig. 3 shows a schematic view of time-shifting electricity production from reneWa- ble energy (RE) using a geothermal Well and a pump Which is operated at 50-100% of nominal load during the day. RE, in this case solar PV, produces a totalof 120 a.u. = arbitrary units (e.g. kWh) during the day. Operating the geothermalpump partly by RE and partly by the poWer output of the heat poWer module, the“Total Delivery to grid” can be time-shifted. In effect, solar PV electricity has been stored by means of the geothermal Well and heat storage.

Fig. 4 shows data from Fig. 3 in graphical form. In this example, reneWable en-ergy (RE) is produced mainly around mid-day, i.e. in the hours 9-16 and peakingat noon. A total of 120 a.u. (e.g. kWh) is produced. The actual demand from themarket is shoWn in the line “Total delivery to grid”, this is also set to be 120 a.u.The geothermal pump consumes 240 a.u. for the production of 2400 a.u. thermalenergy corresponding to a COP of 10. The thermal energy is stored in a tank ofsuitable size. The operation of the heat poWer module is variable during the day,as is apparent from the line “El from Heat Power”. The total daily consumptionand production of electricity from the heat poWer module is 240 a.u. In combina-tion, the RE production around noon has been spread out over the day to matchdemand, thus in effect the electrical energy has been stored. Provided the geo-thermal Well Works like a heat pump With a COP of 10, 100% of the electrical en- ergy is recovered. Higher COP means that in excess of 100% can be produced.

The pump is operated variably. At night time, the pump uses 6 a.u. Whereas atnoon, 14 a.u. are consumed. This mode is possible but not preferred. In general,geothermal pumps are preferably operated at the same speed for longer periods, leading to example 2. 17 Example 2: In this example, the geothermal pump is constantly using 10 a.u. The electricalenergy is supplied by operation of the heat power module especially at night time,and from RE around noon. Even in this case, the RE production can be “smearedout” over the day. The thermal energy reservoir is built up during the day and de- pleted in the evening / night and morning hours.

Fig. 5 shows a table similar to Fig. 3, but With constant operation of the geother-mal pump. Typically, geothermal pumping is more efficient than corresponding to a COP of 10. The next example describes a system With a COP of 20.

Example 3: In this example, as visualized in Fig. 6, a smaller geo pump is operated at thesame speed at all times. Due to the high efficiency of the geothermal system, 240a.u. energy can be delivered to the grid, and the delivery profile can be adjustedWidely. Delivery of about 200 a.u. electricity from afternoon to the next morningrequires about 2000 a.u. thermal energy. For a commercial 150 kW heat powermodule, this equates to 150 kW*20 hours = 3000 kWh electricity, requiring 000 kWh thermal energy at 10% net efficiency. This corresponds to about a2000 m3 tank containing 90 °C Water, and a cooling source of about 20 °C of simi-lar dimensions (or a nearby river or other cooling). The 2000 m3 tank may befilled With Water at all times, but early afternoon the tank may contain only 90°C Water, and the next morning, When 30 000 kWh thermal energy has been usedfor nighttime electricity production (3 000 kWh) using the heat power module,the temperature may have dropped to 75 °C (15 °C temperature difference and2000 m3 equate to 33 000 kWh thermal energy).

Fig. 6 shows a COP 20 geothermal unit, capable of time-shifting intermittent re- newable energy production over the day. 18 For simplicity, the typical production profile of solar PV (photovoltaics) has beenused. It is conceivable, that intermittent Wind energy or any electricity source is used to partly operate the geothermal pump, as shown in the following example: Example 4:Here, wind is assumed to supply a total of 120 a.u. energy, stochastically distrib-uted over the day. Wind energy is used as solar energy to drive the geothermal pump to the degree possible given market demand, as shown in Fig.s 5 and 6.

Fig. 7 shows a graph presenting storage of 120 a.u. wind energy in geothermalheat storage, and time-shifted electricity production with 100% turnaround effi- ciency with a COP 10 geothermal well.

Fig. 8 shows a graphical representation of Fig. 7.

It should be understood that above embodiments described in the present inven-tion are merely examples of useful sequences to achieve the objective of the in-vention, namely to generate and store heat for electricity generation, and therebyto enable the storage of electricity, achievable through a combination of a geo-thermal well, a geothermal pump, a preferably renewable source of electricity, aheat power module and a heat storage tank. All embodiments are simplified. Ob-viously, the source of electricity, be it wind, solar or any other electricity source,may be a single source or a plurality of sources. The source may be in direct prox-imity, or it may be geographically far away. In the latter case electricity supplywould be physically through the grid, and legally through a Power PurchaseAgreement (PPA). If the source such as a solar park is in proximity, the geother-mal facility and the solar park may share certain components such as HV genera-tion, AC/DC converters and the like for grid feed-in. The cooling devices creatingthe cooling flow necessary to operate the heat power module may be utilizing thespace occupied by the solar park. The cooling devices, for example air cooled heat exchangers, could be placed under solar panels, as an example. These and other 19 engineering solutions are well known and obvious. Certain practical solutions,such as use of direct current generated in solar cells for operation of e.g. pumps are also considered rather obvious.

Any geothermal well may be used for the invention. Practically, it is sufficient toutilize geothermal sources providing a flow within the temperature range 80-140°C and even below 100 °C. Those sources are more common in many countries,and cheaper to utilize. The heat may come from depths such as 1-3 km. It isusual that pumping power is needed to produce the thermal flow, and the ther-mal power output divided by the pumping power can be defined as a COP or coef-ficient of performance for heat production. If 1 kWh electrical energy is requiredfor production of 10 kWh of thermal energy, e.g. water in the temperature rangeof 70-90 °C, then these 10 kWh thermal energy can be re-converted to 1 kWhelectrical energy using the heat power module. Such a geothermal well is obvi-ously not suitable for electricity production as net production would be zero. How-ever, if 1 kWh renewable electricity is used to build up a thermal storage of theflow in the temperature range 7 0-90 °C, then this 1 kWh could be recoveredtime-shifted to 100%. Surprisingly thus, the combination of a - as such not par-ticularly useful- geothermal well with high flow resistance (COP 10) and a re-newable electricity source requiring time-shifting is thus a highly useful combi-nation, enabling 100% recovery or storage of said electricity. In practice, manygeothermal wells perform much better than COP 10, thus increasing the perfor- mance of the new battery according to this invention.

In the embodiments, different scenarios regarding the pumping operation werediscussed. In general, for the performance of a geothermal reservoir, it is pre-ferred to operate the geothermal pump at a constant speed with little and slowvariations. For the invention, it is preferred to increase the pump speed whencheap electricity is available e.g. from sun and wind, and to decrease the speed when electricity is in high demand, but a compromise needs to be struck between lO the reservoir Characteristics and the power demand. In practice, variations in the order of +/- 20% within hours may be a good compromise.

When not operational, the hot side heat exchanger of the heat power module maybe kept at an operational temperature by circulating hot water through said hotside heat exchanger and by idling the heat power module, where after the heatpower module may be started up within less than one minute to provide full and phase- and frequency-matched power supply.

The geothermal well can be considered an essentially closed loop of geothermalfluid, compared to a traditional geothermal well comprising an additional volumeof water stored in a tank or underground reservoir. Supply of electricity from therenewable electricity source, while the heat power module is not or only partlyoperating, leads to increased heat energy content in the tank, which later can bere-converted to electricity when demand is high. The said essentially closed loopmay also comprise further use of water at e.g. 75 °C and below for district heat-ing or heating of agricultural areas such as greenhouses, as the case may be us-ing intermediate heat eXchangers according to known art. Finally, the water is reinjected into the geothermal well.

Similar arrangements should be seen as falling under the spirit of this invention.

In summary, a simple solution is disclosed for storing electricity in the form of ahot medium. The solution is cheap in construction and operation, and thereforeprovides a useful method to store intermittent electricity at attractive “levelizedcosts of storage” or LCOS, significantly below the LCOS of electrochemical batter- ies.

Claims

1. l. A system for storing heat energy and generating a power output in theform of electricity using said heat, comprising: - a heat power module (l) comprising a turbine generator arranged to gen-erate a first power output (El) in the form of electricity, wherein said heat powermodule operating in accordance with a thermodynamic closed loop cycle process(RC) being arranged to receive heat input (HSin) from a geothermal well, func-tioning as first continuous energy source (ES l) of geothermal heat (HS), and acold input (CSin) from a cold source (CS) for phase change of a working medium, - a receiver (2) for receiving said first power output (El) and a secondpower output (E2) generated by at least one additional intermittent energysource (ES2) selected from solar photovoltaics, wind power, biogas electrificationor other renewable energy source arranged to intermittently generate electricity, an electricity control system (3) controlling and distributing said firstpower output (El) and second power output (E2) eXternally to the grid, - at least one flow control system (4) arranged to distribute the flow of a ge-othermal medium heated by said geothermal heat (HS) in the geothermal well, - a controller (5) in electrical communication with said one or more receiver(2), the electricity control system (3) and the flow control system (4), wherein saidcontroller (5) is configured to direct said electricity control system (3) and flowcontrol system (4) to regulate electricity distribution and geothermal mediumflow and distribution,characterised in that said controller is arranged to direct the flow control sys-tem (4) to regulate the geothermal medium to - be distributed from the geothermal well to a first thermal storage system(6) when a second power output (E2) is received by the receiver (2), and - be distributed from said first thermal storage system (6) to be used asheat input (HSin) to the heat power module (l) mainly when a second power out-put (E2) is not received by the receiver (2), wherein said heat power module (l) generates said first power output (El). lO 22

2. The system according to claim 1, wherein said controller is arranged todirect the electricity control system (3) to distribute selected electricity to operatea geothermal pump (7) arranged to generate a flow of geothermal medium,wherein the selected electricity is the first power output (El), the second power output (E2) or output generated by the grid.

3. The system according to claim 1 or 2, wherein the receiver (2) is alsoarranged to detect required power demand from the grid, and wherein the se-lected electricity to operate the geothermal pump (7) is the second power output(E2) when the second power output (E2) or the total system power output(E1+E2) eXceed the required power demand from the grid.

4. The system according to any one of the preceding claims, further com-prising: a first thermal storage system (6) and wherein said first thermal storagesystem comprises at least one first thermal storage tank (6A) arranged below or above ground.

5. The system according to claim 4, wherein said thermal storage tank(6A) has a volume of at least 50 m3 and/or is large enough to generate a flow ofgeothermal medium to the heat power module (1) for at least 2 hours of electric- ity production, preferably at least 4 hours.

6. The system according to claim 4 or 5, wherein said first thermal stor- age tank (6A) is used as a district heating tank or a reservoir.

7. The system according to any one of claims 4-6, wherein said thermalstorage tank (6A) is combined storage tank adapted for a layered storage of geo-thermal medium from the hot source (HS) and/or cooling medium from the coldsource (CS), wherein the medium is stored in layers according to density and temperature. 23

8. The system according to any one of claims 4-7, wherein the first ther-mal storage system (6) comprises a second thermal storage tank (6B) arranged to store the geothermal medium exiting the heat power module.

9. The system according to any one of claims 4-8, further comprising:a second thermal storage system (8) and wherein said second thermal stor-age system comprises at least one third storage tank (8A) arranged to store the cooling medium from the cold source.

10. The system according to any one of the preceding claims, further com-prising the geothermal pump (7) and wherein the geothermal pump (7) and theheat power module (1) are selected to create an energy system operating at aCOP of at least 10, i.e. one unit of electricity supplied to the geothermal pumpproduces at least 10 units of electricity generated by heat in said heat power module, shifted in time.

11. The system according to any one of the preceding claims, wherein theheat power module (1) is utilizing an Organic Rankine Cycle to generate electric-ity, wherein said Organic Rankine Cycle is operating with a heat input (HSin) of70-140 °C, a cold input (CSin) between 0-30 °C and a net efficiency for conver- sion of heat to power of at least 5%.

12. The system according to any one of the preceding claims, further com-prising at least one additional intermittent energy source (ES2) selected from so-lar photovoltaics, wind power, biogas electrification or other energy source ar- ranged to intermittently generate electricity.

13. A method for storing electrical energy in the form of heat and produc-ing a power output using said heat, comprising the steps: - generating a first power output (El) in the form of electricity from a firstcontinuous energy source (ES 1) in the form of geothermal heat power by using aheat power module (1) comprising a turbine generator arranged to generate a first power output (El) in the form of electricity, wherein said heat power module 24 Operating in accordance with a thermodynamic closed loop cycle process (RC) be-ing arranged to receive heat input (HSin) from a geothermal well, functioning asfirst continuous energy source (ESl) of geothermal heat (HS), and a cold input(CSin) from a cold source (CS) for phase change of a working medium, - receiving said first power output (E 1) and a second power output (E2)generated by at least one additional intermittent energy source (ESl) selectedfrom solar photovoltaics, wind power, biogas electrification or other renewableenergy source arranged to intermittently generate electricity, - controlling and distributing said first power output (El) and secondpower output (E2) externally to the grid, - distributing the flow of a geothermal medium heated by said geothermalheat (HS) in the geothermal well, - directing said electricity control system (3) and flow control system (4) toregulate electricity distribution and geothermal medium flow and distribution,the flow control system (4) is directed to regulate the geothermal medium to - be distributed from the geothermal well to a first thermal storage system(6) when a second power output (E2) is received by the receiver (2), and - be distributed from said first thermal storage system (6) to be used asheat input (HSin) to the heat power module (l) mainly when a second power out-put (E2) is not received by the receiver (2), wherein said heat power module (l) generates said first power output (El).

14. The method according to claim 13, wherein the electricity control sys-tem (3) is directed to distribute selected electricity to operate a geothermal pump(7) arranged to generate a flow of geothermal medium, wherein the selected elec-tricity is the first power output (El), the second power output (E2) or output gen-erated by the grid.

15. The method according to claim 13 or 14, wherein required power de-mand from the grid is detected, and wherein the selected electricity to operate the geothermal pump (7) is the second power output (E2) when the second power output (E2) or the total system power output (E1+E2) exceed the required power demand from the grid.

16. The method according to claim 14 or 15, wherein the geothermal pump(7) is controlled to be operated at Variable speed depending on the power outputfrom the first continuous energy source (ES 1) and the additional intermittent en- ergy source (10).

17. The method according to any one of claims 14-16, wherein the geother-mal pump (7) is controlled to be operated at essentially the same speed, possibly with +/- 10% Variations, over extended periods of time.

18. The method according any one of claims 13-17, further comprising thestep of: - selecting the geothermal pump (7) and the heat power module (1) to cre-ate an energy system operating at a COP of at least 10, i.e. one unit of electricitysupplied to the geothermal pump produces at least 10 units of heat and later at least 10 units of electricity generated by said heat in said heat power module.