Thermal energy output system and method for controlling the thermal energy output system

Abstract

To provide a thermal energy output system that can effectively reduce operating costs. [Solution] A thermal energy output system 10 according to an embodiment includes a combustion boiler 11, an electric boiler 12, an output line 13, and a control unit 14. The combustion boiler 11 and the electric boiler 12 are connected in parallel to the output line 13, the electric boiler 12 includes a heat storage unit 122, a heating unit 121 that heats the heat storage unit 122, and an output unit 123 that outputs heat from the heat storage unit 122, the electric boiler 12 being configured to be able to simultaneously heat the heat storage unit 122 and output heat from the heat storage unit 122, and the control unit 14 is configured to compare the fuel cost required to cause the combustion boiler 11 to output a unit of thermal energy with the power cost required to cause the electric boiler 12 to output a unit of thermal energy, and to perform control to operate the electric boiler 12 if the power cost is lower than the fuel cost.

Description

[Technical Field]

[0001] The present invention relates to a thermal energy output system and a method for controlling a thermal energy output system. [Background technology]

[0002] Patent Document 1 discloses a steam plant including a steam boiler that generates steam and load equipment that uses the steam generated in the steam boiler as a heating or power source. The steam boiler generates steam by burning fuel, for example, in the form of gas, supplied from a fuel supply source to heat hot water. The steam generated in the steam boiler is transported to the load equipment via steam piping. The operation of the steam plant is managed by a management device configured using, for example, a computer terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7529331 Summary of the Invention [Problem to be solved by the invention]

[0004] The steam plant disclosed in Patent Document 1 is equipped with a single steam boiler and is used to generate steam from fuel supplied from a single fuel supply source. Therefore, the cost required to generate steam in the steam plant is related to the price of the fuel. In other words, the operating cost of the steam plant is bound by the price of the fuel. It may be difficult to reduce the operating cost of the steam plant.

[0005] In order to reduce the operating costs of the system, it is desirable for a system equipped with a boiler to have a configuration that allows for the generation of thermal output (e.g., steam) at a lower cost. In order to generate thermal output at a lower cost, it is desirable for the system to have a configuration that allows for the use of cheaper energy sources (e.g., fuels such as natural gas, electricity). An object of the present invention is to provide a thermal energy output system equipped with a boiler that is capable of generating thermal output at a lower cost, and to provide a method for controlling a thermal energy output system. [Means for solving the problem]

[0006] The thermal energy output system of the present invention includes a combustion boiler, an electric boiler, an output line for outputting thermal output from the combustion boiler and the electric boiler to the outside, and a control unit for controlling the operation of the combustion boiler and the electric boiler. The combustion boiler and the electric boiler are connected in parallel to the output line, the electric boiler includes a heat storage unit, a heating unit for heating the heat storage unit, and an output unit for outputting heat from the heat storage unit, the electric boiler is configured to be able to simultaneously heat the heat storage unit and output heat from the heat storage unit, and the control unit is configured to compare the fuel cost required to cause the combustion boiler to output a unit of thermal energy with the power cost required to cause the electric boiler to output a unit of thermal energy, and to control the electric boiler to operate if the power cost is lower than the fuel cost.

[0007] In the thermal energy output system, the control unit may be configured to formulate a purchase plan for purchasing electricity when the electricity cost is lower than the fuel cost, and to control the operation of the electric boiler based on the purchase results according to the purchase plan.

[0008] In the thermal energy output system, the control unit may be configured, in formulating the purchase plan, to formulate a tentative bidding plan for purchasing electricity during a time period when the electricity cost is lower than the fuel cost, calculate a predicted value for the heat storage level in the heat storage unit based on the tentative bidding plan, and formulate a bidding plan that excludes bids for time periods when the predicted value is equal to or greater than a predetermined value from the tentative bidding plan.

[0009] The control method for a thermal energy output system of the present invention is a control method for a thermal energy output system comprising: an electric boiler including a combustion boiler, a heat storage unit, a heating unit that heats the heat storage unit, and an output unit that outputs heat from the heat storage unit, and configured to be able to simultaneously heat the heat storage unit and output heat from the heat storage unit; an output line in which the combustion boiler and the electric boiler are connected in parallel and output the heat output from the combustion boiler and the electric boiler to the outside; and a control unit that controls the operation of the combustion boiler and the electric boiler, and includes the steps of: comparing the fuel cost required to cause the combustion boiler to output a unit of thermal energy with the electricity cost required to cause the electric boiler to output a unit of thermal energy; and controlling the electric boiler to operate if the electricity cost is lower than the fuel cost, by the control unit.

[0010] The control method for a thermal energy output system may further include formulating, by the control unit, a purchase plan for purchasing electricity when the electricity cost is lower than the fuel cost, and performing control to operate the electric boiler may include operating the electric boiler based on the purchase results according to the purchase plan.

[0011] In the control method for a thermal energy output system, formulating the purchase plan may include formulating a provisional bidding plan for purchasing electricity during a time period when the electricity cost is lower than the fuel cost, calculating a predicted value of the heat storage level in the heat storage unit based on the provisional bidding plan, and excluding from the provisional bidding plan bids for a time period when the predicted value is equal to or greater than a predetermined value. [Effects of the Invention]

[0012] According to an embodiment of the present invention, a thermal energy output system includes multiple boilers (combustion boilers and electric boilers) that use different energy sources and are connected in parallel to an output line. The combustion boilers generate heat by burning supplied fuel, and the electric boilers generate heat by heating a heating element using supplied electricity. A control unit that controls the operation of the combustion boilers and the electric boilers is configured to compare the fuel cost and electricity cost required to generate a unit of thermal energy, and to operate the electric boiler if the electricity cost is lower than the fuel cost. That is, in the thermal energy output system of the embodiment, fuel and electricity are used together to generate thermal energy output (thermal output) by the boilers, and the cheaper of the fuel and electricity is used as the energy source, thereby effectively reducing operating costs.

[0013] According to an embodiment of the present invention, the electric boiler in the thermal energy output system includes a heat storage unit that stores heat, a heating unit that heats the heat storage unit, and an output unit that outputs heat from the heat storage unit. Specifically, the electric boiler is configured so that the heating unit can heat the heat storage unit and the output unit can output heat from the heat storage unit simultaneously. This allows the supplied electric power to be used more efficiently to generate thermal output, and more effective reductions in operating costs can be achieved in the thermal energy output system. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a schematic configuration of a thermal energy output system according to an embodiment of the present invention. [Figure 2] 3 is a flowchart outlining a control method implemented by a control unit in a thermal energy output system according to an embodiment of the present invention. [Figure 3]4 is a flowchart illustrating the formulation of an electricity purchasing plan, which is carried out by a control unit in a thermal energy output system according to an embodiment of the present invention. [Figure 4] 4 is a flowchart illustrating the creation of an operation plan, which is carried out by a control unit in the thermal energy output system according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] A thermal energy output system and a control method for a thermal energy output system of the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram showing a schematic configuration of a thermal energy output system 10 according to one embodiment of the present invention. As shown in Fig. 1, the thermal energy output system 10 of the embodiment includes a combustion boiler 11, an electric heating boiler 12, an output line 13, and a control unit 14. As shown in the figure, the combustion boiler 11 and the electric heating boiler 12 are connected in parallel to the output line 13.

[0016] The thermal energy output system 10 is connected to an external thermal energy utilization plant MP via an output line 13. The output line 13 is supplied with thermal output generated by the combustion boiler 11 and the electric heat boiler 12. The combustion boiler 11 and the electric heat boiler 12 generate thermal output in the form of, for example, steam, hot water, or hot air. The generated thermal output is supplied via the output line 13 to the external thermal energy utilization plant MP, which uses the steam to manufacture products, for example. The external thermal energy utilization plant MP is, for example, a factory facility such as a petrochemical plant, a steel mill, a paper mill, or a power plant. When the thermal output generated by the combustion boiler 11 and the electric heat boiler 12 is in the form of steam, the output line 13 is configured as a pipeline for transporting the steam.

[0017] The control unit 14 controls the operation of the combustion boiler 11 and the electric heat boiler 12 and adjusts the supply of thermal power generated in the combustion boiler 11 and the electric heat boiler 12 to the output line 13. When only one of the combustion boiler 11 and the electric heat boiler 12 is operating and generating thermal power, and the other boiler has stopped generating thermal power, only the thermal power from the fuel boiler 11 or the thermal power from the electric heat boiler 12 is supplied to the output line 13. There may also be cases where both the combustion boiler 11 and the electric heat boiler 12 are operating and generating thermal power, in which case both the thermal power from the fuel boiler 11 and the thermal power from the electric heat boiler 12 may be supplied to the output line 13. The connection state between the fuel boiler 11 and the output line 13 and the connection state between the electric heat boiler 12 and the output line 13 may be controlled by the control unit 14.

[0018] The combustion boiler 11 is supplied with fuel from the outside via a fuel supply line 110. The fuel supply line 110 is connected to, for example, a fuel supply facility (e.g., a city gas pipeline network) FS operated by an external fuel supplier. The combustion boiler 11 includes a combustion device 111 that burns the supplied fuel to generate heat. The heat generated in the combustion device 111 is supplied to a medium line MSL1 through which a medium (e.g., water) supplied from a medium supply source MS flows. The heat supplied to the medium line MSL1 heats the medium in the medium line MSL1, raising its temperature and generating thermal output in the form of, for example, steam. The fuel to be burned in the combustion device 111 may be, for example, city gas containing methane as a main component and supplied in a gaseous state via the fuel supply line 110.

[0019] The electric boiler 12 includes a heat storage unit 122 that stores heat, a heating unit 121 that heats the heat storage unit 122, and an output unit 123 that outputs the heat from the heat storage unit 122. The electric boiler 12 receives power from an external source via a power supply line 120. The power supply line 120 is connected to, for example, a power distribution facility ES operated by an external power transmission and distribution company. The heating unit 121 is configured as a heat generating device that converts the supplied power into heat, and the heat storage unit 122 is heated by the heat generated by the heating unit 121. The heat storage unit 122 has a function of storing the heat supplied from the heating unit 121. The heat temporarily stored in the heat storage unit 122 is supplied by the output unit 123 to a medium line MSL2 through which a medium (e.g., water) supplied from a medium supply source MS flows. As a result, the medium in the medium line MSL2 is heated and its temperature rises, generating thermal output in the form of, for example, steam.

[0020] The heating unit 121 configured as a heat generating device that converts supplied electric power to generate heat may have the form of an electric heater that converts electric power supplied from the power supply line 120 into Joule heat. Note that the configuration of the heating unit 121 is not limited to the form of an electric heater as long as it has the function of supplying heat converted from electric power to the heat storage unit 122. For example, it may be a device that performs dielectric heating.

[0021] The heat storage unit 122 included in the electric boiler 12 has the configuration of a heat storage tank, for example, in which a heat storage material is filled in an insulated container made of stainless steel with excellent corrosion resistance. The outer surface of the insulated container is provided with a heat insulating material to reduce heat loss due to the temperature difference between the inside and outside of the insulated container. Materials such as rock wool, calcium silicate board, ceramic fiber board, and carbon felt are used depending on the temperature range of the insulated container when the heat storage unit 122 is used. The heat storage material used in the heat storage unit 122 may be, for example, a latent heat storage material (PCM: Phase Change Material) composed of a salt containing cations such as lithium ions, potassium ions, magnesium ions, and calcium ions, and anions such as chloride ions, nitrate ions, nitrite ions, hydroxide ions, carbonate ions, acetate ions, and sulfide ions. In addition, examples of heat storage materials that may be used include concrete whose main components are silicon dioxide and calcium carbonate, bricks whose main chemical composition contains specific amounts of magnesium oxide and iron oxide, ceramics made by sintering particles of aluminum oxide, magnesium oxide, silicon carbide, etc., and sensible heat storage materials such as rock, crushed stone, and graphite.

[0022] The heat stored in the heat storage unit 122 is supplied to the medium in the medium line MSL2 by the output unit 123. In the illustrated example, the output unit 123 includes a heat pumping circuit 123c interposed between the heat storage unit 122 and the medium line MSL2. The heat pumping circuit 123c may have the form of a heat pipe through which a heat transfer fluid (HTF) flows, for example. A portion of the heat pumping circuit 123c is in contact with the heat storage unit 122, and another portion is in contact with the medium line MSL2. With this configuration, the heat stored in the heat storage unit 122 is supplied to the medium in the medium line MSL2 via the heat pumping circuit 123c. Note that the output unit 123 may not be provided with the heat pumping circuit 123c, and a configuration may be adopted in which the medium line MSL2 directly contacts the heat storage unit 122 to supply heat to the medium. In this case, the medium line MSL2 is configured as an output for drawing heat from the heat store 122.

[0023] The electric boiler 12, which includes a heating unit 121, a heat storage unit 122, and an output unit 123, is configured to simultaneously heat the heat storage unit 122 (storing heat in the heat storage unit 122) using the heating unit 121 and output (pumping) heat from the heat storage unit 122 using the output unit 123. Therefore, while the heat storage unit 122 is pumping heat to generate thermal output, there is no need to stop the heating of the heat storage unit 122 by the heating unit 121. Generally, unlike the electric boiler 12 of the embodiment, which includes a heat storage unit 122 that converts supplied power into heat and stores it, electric boilers equipped with a storage battery that directly stores supplied power cannot charge the storage battery while the storage battery is discharging. Compared to such electric boilers, the electric boiler 12 can effectively consume supplied power continuously over a wider period of time.

[0024] The ability to consume the supplied electricity continuously over a wider range of periods means that there is a higher possibility that the electricity can be provided as supply capacity (adjustment capacity) that electricity transmission and distribution companies procure through the balancing market to adjust to match fluctuating electricity demand and supply (so-called demand response (DR) characteristics). The adjustment capacity is sold to electricity transmission and distribution companies through the electricity balancing market. The good DR characteristics obtained by the electric boiler 12 having a configuration that allows heat storage in the thermal storage unit 122 and heat extraction from the thermal storage unit 122 to be performed simultaneously can increase profits from selling the adjustment capacity, and as a result, operating costs of the thermal energy output system 10 can be reduced.

[0025] The operation of the combustion boiler 11 (adjustment of the amount of fuel supplied to the combustion device 111, adjustment of the amount of thermal output generated, etc.) and the operation of the electric boiler 12 (adjustment of the amount of power supplied to the heating unit 121, adjustment of the amount of thermal output generated, etc.) are controlled by the control unit 14. The control unit 14 is configured as a device including a calculation element, a memory element, etc. (not shown), and as will be described in detail later, has a configuration capable of formulating a plan for procuring energy sources (fuel for the combustion boiler 11 and electricity for the electric boiler 12) for the thermal energy output system 10.

[0026] The control unit 14 formulates a procurement plan for fuel for the combustion boiler 11 and electricity for the electric boiler 12, and formulates an operation plan for controlling the operation of the combustion boiler 11 and the electric boiler 12 according to the procurement results. Specifically, the control unit 14 is configured to compare the fuel cost required to make the combustion boiler 11 output a thermal output of a unit of thermal energy with the electricity cost required to make the electric boiler 12 output a thermal output of a unit of thermal energy, and formulates an operation plan according to the comparison result.

[0027] Specifically, as will be described later, when the electricity cost is lower than the fuel cost in the above comparison, an operation plan is formulated that includes generating thermal power using the electric boiler 12, and the operation of the electric boiler 12 is controlled based on this operation plan. When the electricity cost is equal to or higher than the fuel cost in the above comparison, an operation plan is formulated that includes generating thermal power using only the combustion boiler 11. In this way, since the control unit 14 is configured to compare the fuel cost with the electricity cost, formulate an operation plan based on the comparison result, and operate the electric boiler 12 in accordance with the formulated operation plan, the thermal energy output system 10 can use electricity to generate thermal power when the electricity cost is lower than the fuel cost, thereby making it possible to effectively reduce the operating costs of the thermal energy output system 10.

[0028] In this specification, "fuel cost" means the cost of procuring the fuel necessary to make the combustion boiler 11 output a thermal output of a unit of thermal energy, and "electricity cost" means the cost of procuring the electricity necessary to make the electric boiler 12 output a thermal output of a unit of thermal energy.

[0029] The control unit 14 is connected to an external energy source supply system so as to be able to formulate an energy source procurement plan for the thermal energy output system 10. The connection between the control unit 14 and the external energy source supply system will be described below.

[0030] The control unit 14 is connected to an external fuel price information system FPS and an external electricity price information system EPS. Specifically, the fuel price information system FPS may be a city gas rate simulation system operated by a city gas retailer. Alternatively, the fuel price information system FPS may be a system that provides pre-calculated fuel cost values ​​based on a thermal output supply menu in a contract with a thermal energy utilization plant MP. Specifically, the electricity price information system EPS may be an electricity trading system operated by the Japan Electric Power Exchange (JEPX). Furthermore, the control unit 14 is connected to an external electricity supply and demand adjustment system EAS. Specifically, the electricity supply and demand adjustment system EAS may be an electricity supply and demand adjustment market system operated by the Electric Power Reserve Exchange (EPRX). The control unit 14, the fuel price information system FPS, the electricity price information system EPS, and the electricity supply and demand adjustment system EAS are connected to each other directly or indirectly via a predetermined communication means such as the Internet so that they can communicate with each other.

[0031] Here, we will explain the electricity trading system operated by the Japan Electric Power Exchange (JEPX), which can be the electricity price provision system EPS. The JEPX is an exchange that mediates spot trading and futures trading of wholesale electricity in Japan. The JEPX operates a day-ahead market (spot market), an intraday market (hour-ahead market), a forward market, and other markets where electricity is bought and sold between electricity producers who want to sell electricity and companies who want to procure electricity.

[0032] In the day-ahead market (spot market), a 24-hour day is divided into 48 0.5-hour (30-minute) time slots, and electricity in each of these 48 slots is traded as an individual commodity. The execution method in the day-ahead market is a blind single-price auction, with transactions taking place the day before the delivery date (i.e., the day the electricity is used). The market price, where supply and demand intersect, is determined by the electricity sold by power generation companies (selling bids) and the bids from electricity retailers or consumers (buying bids), and the transaction is concluded the day before the electricity is used. In the intraday market (hour-ahead market), like the spot market, a 24-hour day is divided into 48 0.5-hour (30-minute) time slots, and transactions take place up to one hour before delivery. The execution method in the intraday market is the intraday trading method, where a sale order and a buy order match. The forward market is a market for trading electricity to be delivered over a certain period in the future, and trading is possible from three years to three days before the delivery date, with the trading period varying depending on the product.

[0033] Here, we will explain the electricity supply and demand adjustment market system operated by the electricity supply and demand adjustment exchange, which can be the electricity supply and demand adjustment system EAS. Electricity transmission and distribution companies need to make adjustments to match fluctuating electricity demand with supply, and this adjustment is achieved by the "adjustment capacity" provided by electricity consumers. "Adjustment capacity" is the power supply capacity that can be made available to ultimately match the difference between demand and supply, which cannot be predicted in advance, and is an essential element for electricity transmission and distribution companies to achieve a stable supply of electricity.

[0034] In the supply and demand balancing market, "adjustment capacity" is traded. Electricity consumers can sell (bid for sales) the electricity they have purchased that they can supply as adjustment capacity in the supply and demand balancing market. When a situation arises where it is actually necessary to supply electricity as adjustment capacity, the seller of the adjustment capacity will supply the electricity sold as adjustment capacity (adjust electricity consumption) in accordance with instructions from the electricity transmission and distribution company that purchased the adjustment capacity. In the supply and demand balancing market, for example, 24 hours are divided into eight time slots (blocks) of three hours each, and the adjustment capacity in each of the eight product blocks is traded as an individual commodity.

[0035] The control unit 14 is configured to formulate an energy source procurement plan by referring to information acquired from external energy source provision systems (fuel price information provision system FPS, electricity price provision system EPS). As shown in the figure, the control unit 14 is communicatively connected to the combustion boiler 11, the medium supply source MS, the electric heat boiler 12, the external energy source provision systems (fuel price information provision system FPS, electricity provision system EP), the external electricity supply and demand adjustment system EAS, and also to the management system MPMS of the external thermal energy utilization plant MP. When formulating the energy source procurement plan, information acquired through these connections, such as the boiler efficiency of the combustion boiler 11, the boiler efficiency of the electric heat boiler 12, the heat storage level in the thermal storage unit 122 of the electric heat boiler 12, the thermal output demand of the thermal energy utilization plant MP, the selling price of fuel, and the selling price of electricity, is referenced. Note that the boiler efficiency of the electric heat boiler 12 included in the thermal energy output system 10 is preferably 85% or higher.

[0036] A control method for the thermal energy output system 10 that can be implemented by the control unit 14 will be described below with reference to the flowchart shown in Figure 2. The control method for the thermal energy output system 10 includes formulating a procurement plan for an energy source for generating thermal output in the thermal energy output system 10, formulating an operation plan for the thermal energy output system 10 based on the results of the energy source procurement, and controlling the operation of the thermal energy output system 10 based on the formulated operation plan. Note that the description of the control method for the thermal energy output system 10 below with reference to Figure 2 will be given on an example in which the fuel for the combustion boiler 11 is city gas, the fuel price information providing system FPS is a gas rate simulation system operated by a city gas retailer, the electricity price providing system EPS related to the procurement of electricity for the electric heating boiler 12 is a spot market trading system operated by the Japan Electric Power Exchange, and the electricity supply and demand adjustment system EAS is an electricity supply and demand adjustment market system operated by the Electric Power Supply and Demand Adjustment Exchange.

[0037] First, in step S01 shown in FIG. 2, the fuel cost required to make the combustion boiler 11 generate a thermal output of a unit of thermal energy (e.g., 1 MJ of steam), and the electricity cost required to make the electric boiler 12 generate a thermal output of a unit of thermal energy (e.g., 1 MJ of steam) are calculated.

[0038] The fuel cost can be calculated by referring to the fuel sales price obtained from an external fuel price information system FPS, as well as the efficiency (boiler efficiency) of generating thermal output in the combustion boiler 11. Note that the calculation of the fuel cost may include a carbon cost (added to the fuel sales price) based on a predicted value of the amount of carbon dioxide emitted as a result of combustion in the combustion device 111 of the combustion boiler 11.

[0039] The electricity cost can be calculated by referring to the electricity price forecast (spot price forecast) obtained by referring to the history of past electricity price fluctuations obtained from an external electricity price providing system EPS, information such as forecast weather, and the efficiency of generating thermal output in the electric boiler 12 (boiler efficiency). Note that when calculating the electricity cost, the forecast value of the profit from selling the adjustment capacity obtained when purchasing electricity may be included (subtracted from the electricity price forecast).

[0040] Next, in step S02, the fuel cost calculated in step S01 is compared with the power cost to determine whether the power cost is lower than the fuel cost. In the example described, when power is purchased in procuring energy sources, the purchase is made via a spot market trading system. Therefore, the fuel cost is compared with the power cost for each of 48 time periods spanning a 24-hour period on the day when the power is used (i.e., the next day). In step S02, it is determined whether there is a time period (time period) in which the power cost is lower than the fuel cost within the 48 time periods on the next day.

[0041] If it is determined in step S02 that there is a case where the electricity cost is lower than the fuel cost, the process in the control unit 14 proceeds to step S03.

[0042] If the determination in step S02 is "no" that the electricity cost is lower than the fuel cost, it is decided not to purchase electricity for the next 24 hours, and a procurement result A (step SNA) is determined, indicating that all energy sources for generating thermal power for the next day will be fuel (city gas). An operation plan A corresponding to the demand for thermal power based on a production plan or the like, provided by the thermal energy utilization plant MP management system MPMS, is formulated (step SNAP). Operation plan A is an operation plan that does not operate the electric boiler 12 (heating the thermal storage unit 122 of the electric boiler 12 and generating thermal power by the electric boiler 12) for the next 24 hours, and generates thermal power only using the combustion boiler 11. Operation control of the thermal energy output system 10 is carried out in accordance with operation plan A (step SNAC). Note that purchasing city gas provided through a city gas pipeline network operated by a fuel supplier does not require a purchase procedure before use; the fee is settled according to the amount used after use.

[0043] In step S03, a purchase plan for the electricity used to generate thermal power in the electric boiler 12 is formulated. Specifically, a purchase bid plan (bidding plan) is formulated for the spot market trading system, which purchases electricity during a time slot (time slot) when the electricity cost is lower than the fuel cost. As will be described in detail later with reference to FIG. 3 , the bidding plan for the spot market trading system may be formulated based on the following day's contract capacity of the thermal energy output system 10 (the maximum amount of electricity that can be used simultaneously in the thermal energy output system 10), a predicted value of the power load of the thermal energy output system 10 (the amount of electricity consumed in the thermal energy output system 10 other than the electricity used for thermal storage), the amount of electricity required according to the demand for thermal power provided by the management system MPMS of the external thermal energy utilization plant MP, the thermal storage level (SOC: State Of Charge) in the thermal storage unit 122 of the electric boiler 12, and the like.

[0044] Next, in step S04, purchases are made in accordance with the purchase plan formulated in step S03. The purchase of electricity can be made to the electricity price providing system EPS by, for example, an administrator of the thermal energy output system 10 using an electricity purchase support function that may be included in the control unit 14. Specifically, a bid (buying bid) is made to the spot market trading system according to the formulated bidding plan. Note that electricity purchases may also be made through an electricity retailer.

[0045] In step S05, the result of the purchase executed in step S04 (power purchase result) is determined. It is determined whether or not there is any purchased power (specifically, whether or not there is a contracted slot in the result of the purchase bid to the spot market trading system (bidding result)). If it is determined in step S05 that there is purchased power "available" (if the purchase is realized in one of the 48 slots over the next 24 hours in the spot market), the energy source procurement result B reflecting the power purchase result is determined (step SYB), and the process proceeds to step S06.

[0046] In step S05, if it is determined that no electricity has been purchased (if no purchases have been realized in the spot market for any 24-hour period on the following day), a procurement result A (step SNA) is determined, in which all energy sources for generating thermal output on the following day will be fuel (city gas), just as in the case where it is determined that no electricity has been purchased in step S02 above. An operation plan A is formulated (step SNAP), and then operation control of the thermal energy output system 10 is carried out in accordance with the operation plan A (step SNAC).

[0047] In step S06, an adjustment power sales plan is formulated to sell the adjustment power obtained as a result of the power purchase results (bidding results) via the electric power supply and demand balancing system EAS. The adjustment power sales plan is formulated based on the predicted adjustment power price obtained from information such as the history of past adjustment power price fluctuations obtained from the electric power supply and demand balancing system EAS and forecast weather. In the example described below, the adjustment power sales plan is specifically a bidding plan for selling adjustment power to the electric power supply and demand balancing market system (EPRX).

[0048] Next, in step S07, the sale is executed in accordance with the adjustment capacity selling plan formulated in step S06. The sale of the adjustment capacity is executed to the electric power supply and demand balancing system EAS, for example, by the administrator of the thermal energy output system 10, using an adjustment capacity selling support function that may be included in the control unit 14. Specifically, a bid (sale bid) is submitted to the electric power supply and demand balancing market system according to the formulated adjustment capacity selling bid plan. In step S07, the sale result of the adjustment capacity in the electric power supply and demand balancing system EAS (the contract result for the adjustment capacity selling bid to the electric power supply and demand balancing market system) is determined. Note that the sale of the adjustment capacity may also be executed through a resource aggregator (a business operator that controls and manages power generation facilities, demand facilities, etc. by directly contracting with electric power consumers).

[0049] Next, in step S08, the result of the purchase executed in step S04 (power purchase result) and the result of the sale of the adjustment power obtained in step S07 are referenced to formulate an operation plan B. In formulating the operation plan B, a plan is formulated to operate the electric heat boiler 12 to generate thermal output. As will be described in detail later with reference to FIG. 4, in formulating the operation plan B, a heat release threshold is set to an appropriate value as the lower limit of the heat storage level at which heat can be extracted in the heat storage unit 122 (i.e., the lower limit of the heat storage level at which the generation of thermal output can be executed in the electric heat boiler 12).

[0050] The operation plan B can be formulated to respond to the need to adjust the actual power consumption from the power used in the electric boiler 12 as adjustment power, depending on the result of the sale of the adjustment power in step S07 described above. In other words, when a command to contribute adjustment power is received from the power transmission and distribution company based on the result of the sale of the adjustment power, the power consumption of the electric boiler 12 is adjusted in accordance with the command. Note that if the formulation of the adjustment power sales plan in step S06 and the sale of adjustment power in step S07 are not executed and the determination in step S05 is "yes," step S08 may be directly executed without going through steps S06 and S07. Next, the control unit 14 executes operation control in accordance with the operation plan B (step SYBC).

[0051] Next, the formulation of the power purchase plan in step S03 described above will be specifically described with reference to the flowchart shown in Fig. 3. Specifically, the formulation of the power purchase plan, which is the formulation of a bidding plan for the spot market trading system, includes formulating a provisional bidding plan (step S031), calculating a predicted value of the thermal storage level (SOC) of the thermal storage unit 122 based on the formulated provisional bidding plan (step S032), and updating the provisional bidding plan by referring to the calculated predicted value of the thermal storage level (step S033).

[0052] First, in step S031, a provisional bidding plan is formulated. The provisional bidding plan is formulated by referring to the contract capacity (the maximum amount of power that can be used simultaneously at the same site under the contract with the electricity retailer) of the site where the thermal energy output system 10 is located or of the power consumer who owns the thermal energy output system 10, the predicted value of the power load other than that of the thermal energy output system 10 at the same site, and the amount of power required based on the demand for thermal output provided by the management system MPMS of the external thermal energy utilization plant MP, and the amount of power to be purchased in each of the 48 time slots in the next 24 hours where the power cost is lower than the fuel cost. A provisional bidding plan is formulated that assumes the purchase of all the power to be purchased.

[0053] Next, in step S032, a predicted value of the heat storage level of the heat storage unit 122 is calculated by a simulation based on the provisional bidding plan formulated in step S031. In the simulation, heating of the heat storage unit 122 by the heating unit 121 of the electric boiler 12 is attempted for all of the periods in which electricity is purchased in the provisional bidding plan. In addition, in the simulation, a predetermined heat release threshold is set as the lower limit of the heat storage level at which heat can be extracted from the heat storage unit 122. It is desirable to set the heat release threshold low (for example, below 50% of the upper heat storage level) so that more electricity can be used during time periods when the electricity cost is lower than the fuel cost. If the heat storage level is equal to or higher than the predetermined heat release threshold, extraction of heat from the heat storage unit 122 (i.e., generation of thermal output) is attempted. By performing the simulation, a predicted transition of the heat storage level of the heat storage unit 122 of the electric boiler 12 over the next 24 hours is calculated.

[0054] Next, in step S033, the results of the simulation executed in step S032 are referenced and the provisional bidding plan is updated. Specifically, frames (out of 48 frames) for which the predicted value of the heat storage level obtained by the simulation for the next 24 hours is equal to or greater than a predetermined value are extracted. The predetermined value of the heat storage level can be set, for example, to be equal to or greater than 90% and equal to or less than 100% of the upper limit of the heat storage level. The provisional bidding plan is updated with reference to the extracted frames. Specifically, a final bidding plan is created by excluding the bids for the extracted frames from the provisional bidding plan.

[0055] As described above, the control unit 14 formulates a tentative bidding plan, calculates a predicted value of the thermal storage level, and updates the tentative bidding plan, thereby formulating a purchasing plan that can procure an energy source that can generate the required amount of thermal power at a lower cost while preventing overheating in the thermal storage unit 122. From the viewpoint of quickly responding to an increase in the amount of thermal power generated due to a sudden change in the demand for thermal power, it is desirable that the thermal storage unit 122 be maintained at a relatively high temperature for a relatively long period of time. When the predetermined value of the thermal storage level is set relatively high (e.g., 90% or higher), a power purchasing plan can be formulated that can purchase power that can maintain the thermal storage unit 122 at a higher temperature for a longer period of time.

[0056] Next, the formulation of the operation plan B performed in step S08 in the control method described with reference to Fig. 2 will be described in detail with reference to the flowchart in Fig. 4. Specifically, the formulation of the operation plan B, which includes a plan for generating thermal output by operating the electric boiler 12, includes calculating a predicted value of the heat storage level of the thermal storage unit 122 based on the results of purchasing electricity (step S081), and setting a heat release threshold value with reference to the calculated predicted value of the heat storage level (step S082).

[0057] First, in step S081, a simulation is performed based on the energy source procurement results (i.e., the power purchase results) determined in the above-mentioned step SYB, and a predicted value of the heat storage level is calculated. Specifically, a simulation is performed in which the electric boilers 12 are operated in all frames for which power purchase has been realized to heat (store heat) the heat storage units 122, and heat is extracted from the heat storage units 122 (i.e., thermal output is generated) using the heat release threshold set in the above-mentioned step S032. The simulation calculates the transition of the predicted value of the heat storage level of the heat storage units 122 over the 24 hours of the next day.

[0058] Next, in step S082, the heat release threshold is set according to the results of the simulation in step S081. Specifically, the heat release threshold is reset according to the heat storage level calculated in the simulation. If the simulation results show that the average heat storage level over the next 24 hours (48 frames) is below 30%, the heat release threshold is set higher than the value used in the simulation. If the simulation results show that the average heat storage level over the next 24 hours (48 frames) is 70% or higher, the heat release threshold used in the simulation is maintained or set lower than the value used in the simulation. This allows for the development of an operation plan B that reduces the number of shutdowns and starts, enables continuous operation for a longer period, and is able to respond to a sudden increase in the heat output to be generated. From the perspective of shortening the response time when starting the electric heat boiler 12, the heat release threshold is preferably set to 10% or higher.

[0059] In the operation plan B, during the time periods when the electric boiler 12 is not generating thermal power, the combustion boiler 11 is operated to generate thermal power. [Explanation of symbols]

[0060] 10. Thermal energy output system 11 Combustion boiler 12 Electric boiler 13 Output Line 14 Control Unit 110 Fuel supply line 111 Combustion equipment 120 Power Supply Line 121 Heating section 122 Heat storage section 123 Output section 123c heat pumping circuit FPS Fuel Price Information System EPS Electricity Price Providing System EAS Electricity Supply and Demand Adjustment System MS media source MSL1, MSL2 medium line MP Thermal Energy Utilization Plant MPMS Management System

Claims

1. Combustion boiler, Electric boiler and an output line for outputting heat output from the combustion boiler and the electric boiler to the outside; a control unit that controls the operation of the combustion boiler and the electric boiler; Equipped with the combustion boiler and the electric boiler are connected in parallel to the output line; The electric boiler includes a heat storage unit, a heating unit that heats the heat storage unit, and an output unit that outputs heat from the heat storage unit, the electric boiler is configured to be able to simultaneously heat the heat storage unit and output heat from the heat storage unit, The control unit The system is configured to compare a fuel cost required to cause the combustion boiler to output a unit of thermal energy with a power cost required to cause the electric boiler to output a unit of thermal energy, and to perform control to operate the electric boiler when the power cost is lower than the fuel cost; When the heat storage level in the heat storage unit is equal to or greater than a heat release threshold, the output unit is configured to output the heat. Thermal energy output system.

2. The thermal energy output system of claim 1, wherein the control unit is configured to formulate a purchase plan for purchasing electricity when the electricity cost is lower than the fuel cost, and to control the operation of the electric boiler based on the purchase results according to the purchase plan.

3. 3. The thermal energy output system of claim 2, wherein the control unit is configured, in formulating the purchase plan, to formulate a provisional bidding plan for purchasing electricity during a time period when the electricity cost is lower than the fuel cost, to calculate a predicted value of the heat storage level in the heat storage unit based on the provisional bidding plan, and to formulate a bidding plan that excludes bids for a time period when the predicted value is equal to or greater than a predetermined value from the provisional bidding plan.

4. Combustion boiler, an electric boiler including a heat storage unit, a heating unit that heats the heat storage unit, and an output unit that outputs heat from the heat storage unit, and configured to be able to simultaneously heat the heat storage unit and output heat from the heat storage unit; the combustion boiler and the electric boiler are connected in parallel, and an output line is provided for outputting thermal outputs from the combustion boiler and the electric boiler to the outside; a control unit that controls the operation of the combustion boiler and the electric boiler; A method for controlling a thermal energy output system comprising: Comparing the fuel cost required to output a unit of heat energy from the combustion boiler with the electricity cost required to output a unit of heat energy from the electric boiler; performing control to operate the electric boiler when the electricity cost is lower than the fuel cost; When a heat storage level in the heat storage unit is equal to or greater than a heat release threshold, outputting the heat by the output unit; by the control unit.

5. The control method according to claim 4, further comprising formulating, by the control unit, a purchase plan for purchasing electricity when the electricity cost is lower than the fuel cost, and performing control to operate the electric boiler includes operating the electric boiler based on the purchase results according to the purchase plan.

6. 6. The control method of claim 5, wherein formulating the purchase plan includes formulating a provisional bidding plan for purchasing electricity during a time period when the electricity cost is lower than the fuel cost, calculating a predicted value of the heat storage level in the heat storage unit based on the provisional bidding plan, and excluding from the provisional bidding plan bids for a time period when the predicted value is equal to or greater than a predetermined value.

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