TECHNICAL FIELD

The present invention relates generally to increasing the efficiency of electric energy utilization. Especially, the invention relates to a system according to the preamble of claim 1. The invention also relates to a corresponding method, a computer program and a non-volatile data carrier storing such a computer program.

BACKGROUND

Today’s electricity consumers have an increasing blend of energy sources to choose from. Typically, due to variations in the production conditions well as the consumption patterns, the supply and demand of the electricity vary substantially over time, both in the short-term perspective and the long-term perspective. It is therefore complicated to ensure that a given consumer has access to the amount of energy that he/she demands at all times. The situation becomes even more complex if economic aspects are factored into the equation. Each energy source has its own tariff, which is often applied dynamically.

Various forms of accumulators, for instance in the form of batteries, may be employed to balance out the peaks and valleys in the supply and demand. However, controlling when to charge or discharge the accumulator involves manual actions that rely on human considerations on the fly. Below follows some examples of battery charging/discharging solutions.

US 11 ,165,268 B2 discloses a charge/discharge pattern battery training system includes a battery subsystem connected to a battery charging subsystem, and a battery charging determination engine coupled to the battery charging subsystem. The battery charging determination engine monitors a plurality of charge/dis- charge cycles performed by the battery subsystem and, based on the plurality of charge/discharge cycles performed by the battery subsystem, identifies a first charge/discharge pattern exhibited by the battery subsystem. The battery charging determination engine then determines a charging schedule that will cause the battery subsystem to exhibit a second charge/discharge pattern that is different than the first charge/discharge pattern, and applies the charging schedule via the battery charging subsystem to the battery subsystem that causes the battery subsystem to exhibit the second charge/discharge pattern. The battery charging determination engine may also retrieve user scheduling information that is associated with a use of the battery subsystem in order to determine the charging schedule.

US 7,671 ,567 B2 describes a method and apparatus that allows the end user to optimize the performance of an all-electric or hybrid vehicle and its charging system for a desired mode of operation is provided. The system of the invention includes multiple charging/operational modes from which the user may select. Each charging/operational mode controls the cut-off voltage used during charging and the maintenance temperature of the battery pack.

KR 101413291 B1 shows a technical solution that creates a battery charging pattern according to the type of vehicle, weather, etc. and uses the charging pattern to predict the amount of charging power, charging time, charging rate, etc. A battery charging apparatus and method for an electric vehicle are provided, comprising: a charger connected to a battery of an electric vehicle to charge the battery; Weather information observation unit for observing the weather information of the area where the charger is installed; and a charger control server that stores electric vehicle charging information and generates a charging pattern according to electric vehicle information and weather information provided from the weather information observation unit, predicts power consumption and charging rate using the charging pattern, and provides it to consumers Including, the battery charging method of the electric vehicle comprising the steps of selecting a charging method; searching for a charging pattern corresponding to an electric vehicle for charging; retrieving a charging unit price according to the estimated charging time; and an estimated charge display step of displaying the estimated charging time and the estimated charging amount, or displaying the estimated charging time and the estimated charging power.

Thus, battery charging systems are known, which for example are adapted to charge electric vehicles. These systems primarily aim at optimizing the capacity and the lifetime of the batteries. However, there is yet no solution that employs an accumulator to automatically accommodate for the fluctuations in the supply and demand of electricity to a consumer so that an expected amount of electric energy provided to the consumer per unit price is maximized.

SUMMARY

The object of the present invention is therefore to offer a solution that solves the above problem and enables electric power to be delivered to an electric load in a reliable and cost-efficient manner despite any variations in the production thereof, and possibly also the consumption of the electric power.

According to one aspect of the invention, the object is achieved by a system for providing electric power to an electric load. The system has a first input configured to obtain electric power from a first source of energy, for example represented by a power grid. The system also contains an accumulator and a control unit. The accumulator, which, in turn may contain a battery, a capacitor and/ or an inductor, is configured to receive electric power obtained via the first input, store the received electric power and make the stored electric power available for consumption by the electric load. The control unit is configured to receive a capacity signal reflecting a state of charge of the accumulator and receive a cost signal representing an electricity tariff for the electric power obtained from the first source of energy over a test period. Based on variations of the cost signal during the test period, the control unit is configured to determine a cost signature reflecting an estimated typical cost for the electric power obtained from the first source of energy as a function of time. Further, the control unit is configured to produce a control signal to the accumulator, which control signal controls a flow of electric power: from the first input to the electric load, from the first input to the accumulator, and/or from the accumulator to the electric load, based on the capacity signal and the cost signature so that an expected amount of electric energy provided to the electric load per unit price is maximized.

The above system is advantageous because it avoids the need for manual interventions in the process of selecting the energy source for the load while ensuring an overall cost-efficient supply of the electric energy thereto.

According to one embodiment of this aspect of the invention, the control signal is configured to cause the accumulator to generate the stored electric power at a magnitude being larger or smaller than a magnitude of the electric power from the first source of energy. If the magnitude of the stored electric power is smaller than the magnitude of the first source of energy, electric power from the first source of energy is fed into the accumulator. If the magnitude of the stored electric power is larger than the magnitude of the first source of energy, electric power from the accumulator is fed into the electric load. Thus, the electric energy may be conveniently controlled to flow into the electric load, into the accumulator or out from the accumulator into the electric load.

According to another embodiment of this aspect of the invention, the electric load is presumed to have a consumption rate that, at least potentially, varies over time. The system therefore contains an electricity meter configured to generate a signal that directly or indirectly reflects an amount of electric power provided to the electric load. The electricity meter may either generate a consumption signal indicating the amount of electric power provided to the electric load, or the electricity meter may generate an input flow signal indicating an amount of electric power obtained from the first source of energy from which input flow signal the consumption signal is derivable. Based on any variations of the consumption signal during the test period, the control unit is further configured to determine a consumption signature reflecting an estimated typical consumption of electric power consumed by the electric load as a function of time. Moreover, the control unit is configured to control the flow of electric power on the further basis of the consumption signature so as to maximize the expected amount of electric energy provided to the electric load per unit price. Hence, consumption variations are also handled in an efficient manner.

According to another embodiment of this aspect of the invention, the system also has at least one second input configured to obtain electric power from at least one respective renewable source of energy, for example originating from wind, solar, wave, tide and/or rain energy. Preferably, the control unit is further configured to receive at least one auxiliary signal reflecting at least one respective property of the at least one renewable source of energy, and the control unit is configured to control the flow of electric power on the further basis of the at least one auxiliary signal. Consequently, electricity from alternative energy sources may supplement electricity from a primary source to enhance the overall costefficiency.

According to yet another embodiment of this aspect of the invention, at least one first auxiliary signal of the at least one auxiliary signal reflects weather forecast information concerning an area in which the at least one respective renewable source of energy is produced. Additionally, the control unit is configured to determine at least one respective estimated future production profile for each of the at least one respective renewable source of energy based on the at least one first auxiliary signal. Here, the respective estimated future production profile reflects a respective predicted production of electric energy from the at least one respective renew- able source of energy as a function of time. The control unit is configured to control the flow of electric power on the further basis of the at least one respective estimated future production profile for each of the at least one respective renewable source of energy. Thereby, any predicted variations in the electricity supply from the renewable source of energy can be weighed into the distribution algorithm.

According to still another embodiment of this aspect of the invention, at least one second auxiliary signal of the at least one auxiliary signal represents a respective electricity tariff for the electric power obtained from each of the at least one respective renewable source of energy over the test period. The control unit is further configured to receive at least one second auxiliary signal during the test period. Based thereon, the control unit is configured to determine a respective estimated future cost profile for each of the at least one respective renewable source of energy. The at least one estimated future cost profile reflects a respective estimated cost for the electric energy from the respective renewable source of energy as a function of time. Analogous to the above, the control unit is configured to control the flow of electric power on the further basis of the at least one respective estimated future cost profile for each of the at least one respective renewable source of energy. The electricity tariff may very well be zero for at least one of the at least one renewable source of energy, which for instance is true if the user himself/herself disposes this source of energy, say provided by a local solar panel. This typically increases the general priority of the energy source in question, so that it is used whenever available.

According to one embodiment of this aspect of the invention, at least one third auxiliary signal of the at least one auxiliary signal represents a seasonal parameter, such as a date, indications of sunrise/sunset, number of sun hours and/or in combination with geographical position. Here, the control unit is configured to control the flow of electric power on the further basis of the at least one third auxiliary signal. According to a further embodiment of this aspect of the invention, at least one fourth auxiliary signal of the at least one auxiliary signal reflects weather forecast information concerning an area in which the electric load is located. The control unit is here configured to determine the consumption signature on the further basis of the at least one fourth auxiliary signal. Consequently, expected future increases or decreases in the electric load’s consumption of electric can be modelled by the control unit.

According to an additional embodiment of this aspect of the invention, the system contains a singular connection point, which is configured to: pass electric power from one or more of the first input and/or the at least one second input into the electric load, and/or pass electric power from one or more of the first input and/or the at least one second input into the accumulator. The control unit is here configured to produce the control signal to cause the accumulator to generate the stored electric power at a magnitude being larger or smaller than the respective magnitudes of the electric power from the first source of energy and the at least one second sources of energy so as to control the flow of electric power to maximize the expected amount of electric energy provided to the electric load L per unit price.

Preferably, for enhanced flexibility, a parallel connection arrangement is included, which is configured to enable: a flow of electric power from the first input into the electric load in parallel with a flow of electric power from the accumulator to the electric load; a flow of electric power from at least one of the at least one second input into the electric load in parallel with a flow of electric power from at least one of the at least one second input into the accumulator; a flow of electric power from the accumulator into the load in parallel with a flow of electric power from first input into the load and/ or a flow of electric power from the accumulator into the load in parallel with a flow of electric energy from at least one of the at least one second input into the electric load. Analogous to the above, the control unit is configured to produce the control signal to cause the accumulator to generate the stored electric power at a magnitude being larger or smaller than the respective magnitudes of the electric power from the first source of energy and the at least one second sources of energy so as to control the flow of electric power to maximize the expected amount of electric energy provided to the electric load per unit price.

According to another aspect of the invention, the object is achieved by a computer-implemented method for providing electric power to an electric load. The method is performed in at least one processor of a control unit of a system that has a first input configured to obtain electric power from a first source of energy. It is further presumed that the system contains an accumulator configured to receive electric power obtained via the first input, store the received electric power and make the stored electric power available for consumption by the electric load. The method involves receiving a capacity signal reflecting a state of charge of the accumulator and receiving a cost signal representing an electricity tariff for the electric power obtained from the first source of energy over a test period; determining, based on variations of the cost signal during the test period, a cost signature reflecting an estimated typical cost for the electric power obtained from the first source of energy as a function of time. Based on the capacity signal and the cost signature, the method involves producing a control signal configured to control a flow of electric power: from the first input to the electric load, from the first input to the accumulator, and/or from the accumulator to the electric load to maximize an expected amount of electric energy provided to the electric load per unit price. The advantages of this method, as well as the preferred embodiments thereof are apparent from the discussion above with reference to the proposed control unit.

According to a further aspect of the invention, the object is achieved by a computer program loadable into a non-volatile data carrier communicatively connected to a processing unit. The computer program includes software for executing the above method when the program is run on the processing unit. According to another aspect of the invention, the object is achieved by a non-volatile data carrier containing the above computer program.

Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

Figure 1 schematically illustrates a system according to a first embodiment of the invention;

Figure 2 schematically illustrates a system according to a second embodiment of the invention;

Figure 3 schematically illustrates a system according to a third embodiment of the invention;

Figure 4 shows a first set of graphs exemplifying how different parameters may vary over time according to one embodiment of the invention;

Figure 5 shows a second set of graphs exemplifying how different parameters may vary over time according to one embodiment of the invention;

Figure 6 shows a block diagram of a control unit according to one embodiment of the invention; and

Figure 7 illustrates, by means of a flow diagram, a method according to one embodiment of the invention. DETAILED DESCRIPTION

In Figure 1 , we see a system according to a first embodiment of the invention for providing electric power PE(L) to an electric load L. Incoming electric power is obtained from a first source of energy PE(S1 ), for example a power grid, via a first input 101 . The electric load L may have a consumption rate that varies over time, for example in a short-term perspective over a 24 hour cycle, and a long-term perspective over a seasonal cycle. The electric load L may consequently be represented by one or more households. Technically, however, the electric load L may equally well be constituted by any single piece of electricity consuming equipment, or a group thereof. According to the invention, the electric load L may also have a constant consumption. In any case, as will be discussed below, an electricity tariff for the electric power obtained from the first source of energy PE(S1 ) varies over time.

The system contains a control unit 120 and an accumulator 110, and preferably also an electricity meter 130.

The accumulator 110 is configured to receive electric power obtained via the first input 101 , store the received electric power and make the stored electric power PE(A) available for consumption by the electric load L. The accumulator 110, in turn, may include one or more batteries, one or more capacitive elements and/or one or more inductive elements for holding the accumulated electric power.

The control unit 120 is configured to receive the capacity signal SOC and a cost signal ST. If the electricity meter 130 is included, the control unit 120 is further configured to receive a consumption signal SL, or derive such a signal as will be discussed below.

The cost signal ST represents the electricity tariff for the electric power obtained from the first source of energy PE(S1 ) over a test period. The test period may have such an extension that the cost signal ST has a constant value over the test period. However, should the cost signal ST vary over the test period, the control unit 120 is configured to determine a figure providing a fair representation of the cost over the test period, such as an average or median value. In other words, based on variations of the cost signal ST during the test period, the control unit 120 is configured to determine a cost signature reflecting an estimated typical cost for the electric power obtained from the first source of energy PE(S 1 ) as a function of time t.

The electricity meter 130 is configured to generate a basis for the consumption signal reflecting an amount of electric power PE(L) provided to the electric load L. For example, the consumption signal may reflect a number of kilo Watt hours (kWh) for a given period and/or a momentary wattage as a function of time.

In Figure 1 , the electricity meter 130 is arranged on the first input 101. The electricity meter 130 thus generates an input flow signal SE reflecting an amount of electric power obtained from the first source of energy PE(S 1 ). Additionally, the accumulator 110 is configured to generate an accumulator flow signal SA reflecting an amount of electric power received in or fed out from the accumulator 110. The control unit 120 is configured to receive the input flow signal SE and receive the accumulator flow signal SA. Based thereon, the control unit 120 is configured to derive the consumption signal SL as a difference between the received signals.

The capacity signal SOC reflects a state of charge of the accumulator 110, i.e. a level of charge relative to its capacity, for instance expressed as a percentage ranging from 0 to 100.

According to one embodiment of the invention, based on any variations of the consumption signal SL during the test period, the control unit 120 is configured to determine a consumption signature reflecting an estimated typical consumption of electric power PE(L) consumed by the electric load L as a function of time t.

Moreover, based on the capacity signal SOC, the cost signature and preferably the consumption signature, the control unit 120 is configured to control a flow of electric power from the first input 101 to the electric load L, from the first input 101 to the accumulator 110, or from the accumulator 110 into the electric load L in such a manner that an amount of electric energy provided to the electric load L per unit price is expected to be maximized.

In the embodiment illustrated in Figure 1 , the system includes a singular connection point 105 configured to pass electric power from the first input 101 into the electric load L, pass electric power from the first input 101 into the accumulator 110, or pass electric power from the accumulator 110 into the electric load L. Here, the accumulator 110 preferably includes a combined AC-to-DC and DC-to-AC converter (not shown), which is configured to convert incoming electric power from the first source of energy PE(S1 ) to a DC voltage and also make the stored electric power PE(A) in the accumulator 110 available as an output AC voltage to the electric load L via the singular connection point 105. The control unit 120 is configured to produce a control signal C adapted to cause the accumulator 110 to generate the stored electric power PE(A) to have a magnitude, which is either larger or smaller than a magnitude of the electric power from the first source of energy PE(S1 ). If the stored electric power PE(A) has a smaller magnitude than the first source of energy PE(S1 ), the incoming electric power from the first source of energy PE(S1 ) will be fed into the accumulator 110. If the stored electric power PE(A) has a larger magnitude than the first source of energy PE(S1 ), stored electric power PE(A) from the accumulator 110 will instead be fed into the electric load L. Thus, the control unit 120 may control the flow of electric power from the first input 101 into the electric load L, from the first input 101 to the accumulator 110, and/or from the accumulator 110 into the electric load L.

As will be discussed below, in embodiments of the invention, the system may include a parallel connection arrangement, and the control unit 120 may be configured to control the parallel connection arrangement so that the electric power flows in parallel into both the accumulator 110 and the load L, or in parallel into the load from both the first input 101 and the load L. Figure 2 schematically illustrates a system according to a second embodiment of the invention. In Figure 2, reference numerals that occur also in Figure 1 , designate the same devices and signals as described above with reference to Figure 1.

In Figure 2, the system contains a first switch 111 arranged to selectively control the flow of electric power from the first input 101 either into the electric load L or into the accumulator 110. The first switch 111 is here controlled by a first control signal C1 , which is produced by the control unit 120. The system also contains a second switch 112 arranged to selectively control the flow of electric power to be provided to the electric load L either from the first input 101 or from the accumulator 110. The second switch 112 is controlled by a second control signal C2, which likewise is produced by the control unit 120. The control unit 120 is configured to produce the first and second control signals C1 and C2 respectively so as to control the flow of electric power to maximize the expected amount of electric energy provided to the electric load L per unit price.

Referring now to Figure 4, we see a first set of graphs exemplifying how different parameters may vary over time according to one embodiment of the invention. Specifically, Figure 4 shows examples of the cost signal ST, the state of charge SOC of the accumulator 110 and the consumption of electric power PE(L) in the electric load L as functions of time t.

For example, here, between first and second points in time ti and t2, there is a peak in the consumption of electric power PE(L) in the electric load L. This may correspond to when the people in a household wake up and start using electric equipment. Simultaneously, the cost signal ST increases, and at the first point in time ti , the state of charge SOC of the accumulator 110 is relatively high. Therefore, in order to save costs, the control unit 120 produces the control signal C, or the control signals C1 and C2, such that electric energy from the accumulator 110 is fed into the load L. Between the second point in time t2 and a third point in time ts, the consumption of electric power PE(L) in the electric load L is low, essentially zero, and the cost signal ST continues to show high levels. Therefore, electric energy is neither stored into, nor extracted from the accumulator 110. This period may correspond to when the people in the household are at work and/or in school.

From the third point in time ts to a fourth point in time t4, the consumption of electric power PE(L) in the electric load L rises again. Between the third and fourth points in time ts and t4, although declining, the cost signal ST shows relatively high levels. Therefore, the control unit 120 produces the control signal C, or the control signals C1 and C2, such that electric energy is extracted from the accumulator 110 and fed into the load L. As a result, the state of charge SOC of the accumulator 110 decreases between the third and fourth points in time ts and t4. The period between the third and fourth points in time ts and t4 may correspond to when the people in the household return from work/school.

Between the fourth point in time t4 and a fifth point in time ts, the consumption of electric power PE(L) in the electric load L is again low, essentially zero. The cost signal ST designates very low levels, and at the fourth point in time t4, the state of charge SOC of the accumulator 110 is low. Therefore, the control unit 120 produces the control signal C, or the control signals C1 and C2, such that incoming electric power is fed from the first input 101 into the accumulator 110. As a result, the state of charge SOC of the accumulator 110 increases between the fourth and fifth points in time t4 and ts.

From the fifth point in time ts to a sixth point in time ts, the cost signal ST increases rapidly. During the same period, the electric load L demands a relatively large amount of electric power PE(L) . Therefore, the control unit 120 produces the control signal C, or the control signals C1 and C2, such that electric power is drawn from the accumulator 110 and fed into the electric load L, and no incoming electric power from the first input 101 is consumed. Between the sixth point in time te and a seventh point in time t?, the electric load L demands a moderate amount of electric power and the cost signal ST decreases. Therefore, during this period, the control unit 120 produces the control signal C, or the control signals C1 and C2, such that incoming electric power is fed from the first input 101 into the accumulator 110. Due to the moderate consumption of the electric load L, a fraction of the incoming electric power may be forwarded to the electric load L while the state of charge SOC of the accumulator 110 increases in response to incoming electric power.

Figure 3 schematically illustrates a system according to a third embodiment of the invention. In Figure 3, the reference numerals that occur also in Figures 1 and 2, designate the same devices and signals as described above with reference to Figures 1 and 2.

In the embodiment of Figure 3, the system contains at least one second input, here exemplified as 102 to 10m, configured to obtain electric power from at least one renewable source of energy PE(S2) to PE(SITI) respectively. The renewable sources of energy PE(S2) to PE(SITI) may for example deliver electric energy originating from wind, solar, wave, tide and/or rain energy.

In Figure 3, the electricity meter 130 is arranged on the output to the electric load L. Consequently, the electricity meter 130 directly generates the consumption signal SL, which is fed to the control unit 120. Here, the control unit 120 is configured to receive the consumption signal SL, receive the accumulator flow signal SA, and based thereon derive the input flow signal SE as a difference between the received signals SL and SA. In this case, the input flow signal SE reflects a total amount of electric power obtained from the first source of energy PE(S 1 ) and the at least one second source of energy PE(S2) to PE(SITI) .

In order to take account for the special characteristics of and conditions for the renewable sources of energy PE(S2) to PE(SITI) , the control unit 120 is preferably configured to receive at least one auxiliary signal S _a reflecting at least one respective property of each of the renewable sources of energy PE(S2) to PE(SITI) . The control unit 120 is configured to control the flow of electric power from the sources of energy PE(S 1 ) , PE(S2) to PE(SITI) into the accumulator 110 and/or into the electric load L on the further basis of the at least one auxiliary signal S _a .

A respective first auxiliary signal s _ai of the auxiliary signals S _a may reflect weather forecast information concerning a respective area in which each of the renewable sources of energy PE(S2) , ... , PE(SITI) is produced. For example, the first auxiliary signal s _ai may describe the chances of sunshine during different intervals over the day in an area where a solar panel is located, estimated wind speed during different intervals over the day in an area where a wind mill farm is arranged, and so on.

Here, the control unit 120 is configured to determine at least one respective estimated future production profile for each of the respective renewable sources of energy PE(S2) to PE(SITI) based on the respective first auxiliary signals s _ai . Each of the estimated future production profile reflects a respective predicted production of electric energy from the renewable source of energy PE(S2) to PE(SITI) as a function of time t. Additionally, the control unit 120 is configured to control the flow of electric power on the further basis of the respective estimated future production profiles for each of the renewable sources of energy PE(S2) to PE(SITI) . The control unit 120 is configured to control the flow of electric power from the first input 101 and/or one or more of the at least one second input 102 to 10m into the electric load L, from the first input 101 and/or one or more of the at least one second input 102 to 10m into the accumulator 110 and/or from the accumulator 110 to the electric load L.

According to another embodiment of the invention, additionally or alternatively, the control unit 120 is configured to receive at least one second auxiliary signal s _a 2 of the auxiliary signals S _a , which at least one second auxiliary signal s _a 2 represents a respective electricity tariff for the electric power obtained from each of the renewable sources of energy PE(S2) to PE(SITI) over the test period. Frequently, however not always, the electricity tariff is zero for one or more of the renewable sources of energy PE(S2) to PE(SITI). Typically, the electricity tariff is zero if the consumer with the electric load L disposes of the renewable source of energy PE(S2) to PE(SITI) in question. In such a case, the estimated cost for the electric energy from the source of energy PE(S2) to PE(SITI) as a function of time t may become trivial.

Otherwise, i.e. for sources of energy with non-zero tariffs, the control unit 120 is configured to receive the at least one second auxiliary signal s _a 2 during the test period. Based thereon, the control unit 120 is further configured to determine a respective estimated future cost profile for each of the renewable sources of energy PE(S2) to PE(SITI). The estimated future cost profile reflects a respective estimated cost for the electric energy from the respective renewable sources of energy PE(S2) to PE(SITI) as a function of time t.

Moreover, on the further basis of the respective estimated future cost profile for each of the renewable sources of energy PE(S2) to PE(SITI) , the control unit 120 is configured to control the flow of electric power from the first input 101 and/or one or more of the at least one second input 102 to 10m into the electric load L, from the first input 101 and/or one or more of the at least one second input 102 to 10m into the accumulator 110 and/or from the accumulator 110 into the electric load L so that an expected amount of electric energy provided to the electric load L per unit price is maximized.

According to one embodiment of the invention, at least one third auxiliary signal s _a 3 of the auxiliary signals S _a reflects weather forecast information concerning an area in which the electric load L is located. Namely, if for example the electric load L contains pieces of equipment arranged to heat and/or cool a facility or part thereof, the electric load’s L energy consumption typically de- pends on one or more weather parameters, such as the air temperature and/or the air humidity. Here, the control unit 120 is configured to determine the consumption signature on the further basis of the at least one third auxiliary signal s _a 3. Thus, expected future increases and/or decreases in the electric load’s L energy consumption can be adequately modeled and compensated for by the control unit 120.

A fourth auxiliary signal s _a 4 of the auxiliary signals S _a may represent at least one seasonal parameter that influences one or more of the renewable sources of energy PE(S2) to PE(SITI). For example, the seasonal parameter may be represented by temporal indicators for sunrise and sunset respectively; information about whether it is currently spring, summer, autumn or winter; a current date and/or an indication of geographical position.

Here, the control unit 120 is configured to control the flow of electric power from the first input 101 and/or one or more of the at least one second input 102 to 10m into the electric load L, from the first input 101 and/or one or more of the at least one second input 102 to 10m the first input 101 into the accumulator 110 and/or from the accumulator 110 to the electric load L on the further basis of the at least one fourth auxiliary signal s _a 4 so that the amount of electric energy provided to the electric load L per unit price is expected to be maximized.

The system includes the singular connection point 105, which is here configured to pass electric power from one or more of the first input 101 and/or the at least one second input 102 to 10m into the electric load L, and/or pass electric power from one or more of the first input 101 and/or the at least one second input 102 to 10m into the accumulator 110, and/or pass electric power from the accumulator 110 into the electric load L. Analogous to the above, the accumulator 110 preferably includes a combined AC-to-DC and DC-to-AC converter (not shown), which is configured to convert incoming electric power from the first source of energy PE(S1 ) and the at least one second input 102 to 10m to a DC vol- tage. The combined AC-to-DC and DC-to-AC converter is further configured to make the stored electric power PE(A) in the accumulator 110 available as an output AC voltage to the electric load L via the singular connection point 105. The control unit 120 is configured to produce the control signal C to cause the accumulator 110 to generate the stored electric power PE(A) at a magnitude being either larger or smaller than the respective magnitudes of the electric power from the first source of energy PE(S1 ) and the at least one second sources of energy PE(S2) to PE(SITI).

If the stored electric power PE(A) has a smaller magnitude than one or more of the first source of energy PE(S1 ) and the at least one second sources of energy PE(S2) to PE(SITI), the incoming electric power from said one or more of the first source of energy PE(S1 ) and the at least one second sources of energy PE(S2) to PE(SITI) will be fed into the accumulator 110.

If the stored electric power PE(A) has a larger magnitude than the first source of energy PE(S1 ) and the at least one second sources of energy PE(S2) to PE(SITI), the stored electric power PE(A) from the accumulator 110 will instead be fed into the electric load L. Thus, the control unit 120 may control the flow of electric power from the inputs 101 , 102 to 10m into the electric load L, from the inputs 101 , 102 to 10m into the accumulator 110, or from the accumulator 110 into the electric load L.

Preferably, for additional flexibility and control, the system includes a parallel connection arrangement (not shown), is configured to enable:

- a flow of electric power from the first input 101 into the electric load L in parallel with a flow of electric power from the accumulator 110 into the electric load L;

- a flow of electric power from at least one of the second inputs 102,... , 10m into the electric load L in parallel with a flow of electric power from at least one of the second inputs 102, ... , 10m into the accumulator 110;

- a flow of electric power from the accumulator 110 into the load L in parallel with a flow of electric power from first input 101 into the load L; and/or

- a flow of electric power from the accumulator 110 into the load L in parallel with a flow of electric energy from at least one of the second inputs 102,... , 10m into the electric load L.

Furthermore, the control unit 120 is configured to control the parallel connection arrangement to maximize the expected amount of electric energy provided to the electric load L per unit price.

Figure 5 shows a second set of graphs exemplifying how different parameters may vary over time according to one embodiment of the invention. In Figure 5, the graph representing the cost signal ST as a function of time t and the graph representing the consumption of electric power PE(L) in the electric load L as a function of time t are identical to the corresponding graphs of Figure 4. Figure 5 also includes a graph representing an amount of energy PE(S2) produced by a renewable source of energy as a function of time t and a graph representing the state-of charge SOC of the accumulator 110 as a function of time t.

One difference relative to the scenario described with reference to Figure 4 is that between the second and third points in time t2 and ts, there is a peak in the amount of energy PE(S2) produced by the renewable source of energy. Since, during this period, the electric load L consumes very little electric power, the control unit 120 produces the control signal C, or the control signals C1 and C2, such that electric energy from the renewable source of energy is fed into the accumulator 110, and consequently its state-of charge SOC rises.

Between the third and fourth points in time ts and t4, the control unit 120 produces the control signal C, or the control signals C1 and C2, such that energy from the accumulator 110 is fed into the electric load L to handle the increased demand of the electric load L. The control unit 120 uses the relatively low cost ST of the first source of energy PE(S1 ) during the interval from the fourth point in time t4 to the fifth point in time ts when the electric load L has a low demand to produce the control signal C, or the control signals C1 and C2, such that electric energy from the first source of energy PE(S1 ) is fed into the accumulator 110, and consequently its state- of charge SOC rises.

In addition to the principles outlined above according to which electric energy is fed into the accumulator 110 when the electric load L has a demand sufficiently low to allow this - and at the same time - at least one of the sources of energy delivers electric energy at a sufficiently low cost; it is preferable that the control unit 120 aims at feeding electric energy into the accumulator 110 relatively shortly before it is expected that it is economically desirable to withdraw electric energy from the accumulator 110 into the electric load L. Namely, the accumulator’s 110 temperature rises when increasing its state-of-charge SOC; and a relatively high temperature of the accumulator 110, in turn, is beneficial when drawing electric energy out from the same with respect to energy efficiency, especially if it contains batteries. Thus, a shortened time between charging and discharging reduces the need for dedicated warming of the accumulator 110.

It is generally advantageous if the above-described procedure is effected in an automatic manner by executing one or more computer programs. Referring now to Figure 6, the control unit 120 preferably includes processing circuitry in the form of at least one processor 615 and a memory unit 616, i.e. non-volatile data carrier, storing a computer program 617, which, in turn, contains software for making the at least one processor 615 execute the actions mentioned in this disclosure when the computer program 617 is run on the at least one processor 615. Figure 6 exemplifies incoming signals in the form of the cost signal ST, auxiliary signal S _a , the consumption signal ST and the state-of-charge signal SOC, and output signals in the form of the control signal C, or the control signals C1 and C2 respectively. In order to sum up, and with reference to the flow diagram in Figure 7, we will now describe a computer-implemented method according to one embodiment of the invention for providing electric power to an electric load having a consumption rate that varies over time.

In a first step 710, a consumption signal SL is received, which consumption signal SL reflects an amount of electric power PE(L) provided to the electric load L. In a step 720, for example in parallel with step 710, a capacity signal SOC is received, which capacity signal SOC reflects a state of charge of the accumulator 110. In a step 730, for example in parallel with steps 710 and 720, a cost signal ST is received, which cost signal ST represents an electricity tariff for the electric power obtained from the first source of energy PE(S1 ).

A step 740 after step 710 checks if the test period has ended; and if so, a step 750 follows. Otherwise, the procedure loops back to step 710. A step 760 after step 730 also checks if the test period has ended; and if so, a step 770 follows. Otherwise, the procedure loops back to step 730.

In step 750, a consumption signature is determined based on the variations of the consumption signal SL during the test period. The consumption signature reflects an estimated typical consumption of electric power PE(L) consumed by the electric load L as a function of time t.

In step 770, for instance in parallel with step 750, a cost signature is determined based on the variations of the cost signal ST during the test period. The cost signature reflects an estimated typical cost for the electric power obtained from the first source of energy PE(S1 ) as a function of time t.

Subsequent to steps 750 and 770, in a step 780, based on the capacity signal SOC, the consumption signature and the cost signature, a flow of electric power is controlled from the first input 101 to the electric load L, from the first input 101 to the accumu- lator 110 and/or from the accumulator 110 to the electric load L to maximize an amount of electric energy provided to the electric load L per unit price.

Then, the procedure loops back to steps 710, 720 and 730 for updating of the consumption, capacity and cost signals. Of course, in a practical implementation, step 780 preferably continues to be executed in parallel with this.

All of the process steps, as well as any sub-sequence of steps, described with reference to Figure 7 may be controlled by means of a programmed processor. Moreover, although the embodiments of the invention described above with reference to the drawings comprise processor and processes performed in at least one processor, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The program may either be a part of an operating system, or be a separate application. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a DVD (Digital Video/Versatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal, which may be conveyed, directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

The term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. The term does not preclude the presence or addition of one or more additional elements, features, integers, steps or components or groups thereof. The indefinite article "a" or "an" does not exclude a plurality. In the claims, the word “or” is not to be interpreted as an exclusive or (sometimes referred to as “XOR”). On the contrary, expressions such as “A or B” covers all the cases “A and not B”, “B and not A” and “A and B”, unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

It is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.