GB2474305A

GB2474305A - Smoothing domestic electricity consumption using an electricity storage device

Info

Publication number: GB2474305A
Application number: GB0917830A
Authority: GB
Inventors: Martin Pollock
Original assignee: Siemens PLC
Current assignee: Siemens PLC
Priority date: 2009-10-09
Filing date: 2009-10-09
Publication date: 2011-04-13
Anticipated expiration: 2029-10-09
Also published as: GB2474305B; GB0917830D0

Abstract

A device for smoothing domestic electricity consumption, comprising a storage device 4, such as a battery or super capacitor, is arranged to store energy from an electricity supply network during periods when the power demand from a domestic load falls below a certain threshold. The device is arranged to release the stored electrical energy from the storage device to the domestic load when power demand from the domestic load exceeds a certain threshold. A controller associated with the domestic utility meter controls the flow of power in and out of the storage device using input and output conditioners. In practice, excess generating capacity relative to a lack of demand in off peak periods can be stored for use during peak period, thus reducing strain in the supply network due to high demand during peak periods.

Description

DEVICE AND METHOD FOR SMOOTHING DOMESTIC ELECTRICITY

CONSUMPTION

At present, domestic electricity demand fluctuates during the day.

For example, very little power is consumed during the night-time hours of midnight to 06:00 a surge of power is consumed between 06:00 and 09:00 as people wake up, prepare breakfast, heat water and so on. Domestic consumption will be reduced between 09:00 to 12:00 as many people leave the home to go to work. A small surge will occur between 12:00 and 14:00 as lunches are prepared, and an increasing demand will follow between 15:00 to about 22:00, as children come home from school, heating and lighting is switched on, meals are prepared. r

The infrastructure for domestic power distribution must be 15 sufficiently robust to supply the highest peak demand. This means that 100A at 240V AC is available to a typical United Kingdom house. The infrastructure needs to be capable of supplying power at peak levels to all homes at peak consumption during the day, and the infrastructure is much underutilised at other times of day.

A typical United Kingdom home consumes about 24kWh per day. If distributed evenly throughout the day, this would equate to a constant 1kW load: consuming about 5A. If the domestic consumption could be spread equally throughout the day, the infrastructure could be scaled down, to provide a lower peak current availability to each home. This in turn would mean that more homes could be supplied with existing power generation, and that renewable energy may make a more significant contribution to meeting domestic energy requirements. Renewable energy from sources such as wind, tide, wave, geothermal provides a varying quantity of energy, not synchronised to demand peaks. More conventional power generation methods such as coal, oil, gas and nuclear can be controlled to meet peaks in demand which are not met by the renewable energy sources.

The present invention provides methods and arrangements for spreading, or smoothing, domestic electricity consumption.

The present invention accordingly provides methods and arrangements as recited in eth appended claims.

The above, and further, objects, advantages and characteristics of the present invention will become more apparent from the following description of certain embodiments thereof, in conjunction with the accompanying Fig. 1 which schematically illustrates an arrangement according to the present invention.

The present invention provides a device which presents a varying domestic electrical load to an electricity supply network as a relatively constant load. In particular, the domestic load is provided with a storage device which stores energy from the electricity supply network during periods of low demand, and releases the stored energy to the varying domestic load during periods of higher demand.

An example device of the present invention is schematically illustrated in Fig. 1. The device comprises a monitor 1 a controller 2 an input conditioner 3 a storage device 4 and an output conditioner 5. The monitor 1 is connected to an electricity supply network. The electricity supply network and the output conditioner 5 supply energy to the varying domestic load, represented by consumer unit panel or fuse box 6 that contains the circuit breakers linked to individual household circuits.

The monitor 1, controller 2 may derive power from the electricity distribution network or may be supplied independently, for example by a battery.

The monitor 1 may be a conventional existing energy meter, provided that it is capable of providing consumption data to the controller 2. Alternatively, the monitoring means may be a new Smart Meter as is currently contemplated by new EU and other Regulation.

0 In an embodiment, the monitor 1 provides sufficient information to the controller 2 for it to detect whether present instantaneous (or near 15 real-time) power consumption is above or below a given threshold. This threshold is a programmable parameter that may be presented to the v...... control means 2 from time to time by traditional or "smart" metering communications techniques. The information provided to the controller may be as simple as a one-bit threshold signal: binary "1" indicating instantaneous consumption exceeding the threshold; binary "0" indicating instantaneous consumption below the threshold. Rather than reacting to instantaneous consumption, which may vary widely as devices are switched on and off, the information provided by the monitor may represent an averaged consumption over a certain period of time, such as one minute or 30 seconds. The controller 2 may be provided with a smoothing arrangement to prevent it reacting to rapid changes in the information provided by the monitor. For example, the controller may be arranged to react according to an average value of the information from the controller representing a time period of 2-5 minutes. On the other hand, the monitor and the controller may be arranged to react immediately to changes in consumption. The threshold may be fixed according to the size of the domestic installation, the tariff subscribed to by the householder, public policy, or any other constraint. The threshold may be fixed permanently, reviewed at selected intervals such as annually or quarterly, or following a certain cumulative power consumption, or revised daily or more frequently, as desired.

In an example reacting to instantaneous consumption, if instantaneous consumption is below the given threshold, then the controller 2 will send appropriate signals to the input conditioner 3 to cause energy to flow from the electricity supply network into the storage 0 device 4. This is arranged such that the sum of the previously measured below-threshold consumption and the additional consumption caused by 15 the energy flowing into the input conditioner 3 and so into the storage device 4 is equal to the given threshold, to within a predetermined tolerance range.

Similarly, if instantaneous consumption is above the given threshold, then the controller 2 will send appropriate signals to instruct the output conditioner 5 to allow energy to flow out of the storage device 4 to the load 6. This is arranged such that the energy flowing out of the storage device 4 meets the difference between the previous above-threshold quantity and the given threshold, such that the consumption from the electricity supply network is equal to the given threshold to within a predetermined tolerance range.

Thus the controller 2 is able control the input conditioner 3 and the output conditioner 5 in such a way that the monitor 1 will record a relatively constant consumption of energy close to the given threshold, always provided that the storage device 4 has sufficient capacity to receive energy from the input conditioner 3 and supply it to the output conditioner 5.

The input conditioner 3 and the output conditioner 5 are arranged according to the particular requirements of the storage device 4. For example, the storage device 4 may be a super-capacitor, or re-chargeable battery. In this case the input conditioner 3 provides AC to DC conversion and appropriate voltage protection and current limitation. Similarly, the output conditioner 5 provides DC to AC conversion, frequency and phase synchronisation, and power quality control.

In a preferred configuration the storage device 4 is of such capacity that it can support a given threshold that would be equivalent to the average daily consumption rate. In the UK today this is about 24kWh (86.4MJ) per day, an average of 1kW. Using the device of the invention equipped with such a storage device would present a constant consumption load to the electricity supply system. Rechargeable batteries of suitable capacities are being developed by various automotive manufacturers, as a component in planned electrically powered vehicles.

On the other hand, conventional lead-acid car batteries with a capacity of 4MJ or more (lOOAh at 12V) are readily available. Several such batteries could be networked to provide the required capacity. Alternative energy storage devices, such as compressed air tanks, may be used in place of electrical storage devices.

In another preferred configuration the storage device (4) is modular and exchangeable. For example, a home may be provided with two exchangeable storage devices 4. If, during a period of low domestic load (i.e. below the threshold), a connected storage device becomes fully charged, the input conditioner 3 may switch to begin or complete charging of the second storage device 4. Similarly, during a period of high domestic consumption (i.e. above the threshold) one storage device may become fully discharged. When that happens, the output conditioner 5 may switch to another storage device to provide energy to the domestic load.

Switching between the storage devices may be achieved by a manually operated switch or preferably automatically in response to a detected charge level in one of the storage devices exceeding an upper limit or falling below a lower limit.

In a development of this configuration, one of the storage devices may be used to power a vehicle. In one example, an electric vehicle is plugged into the domestic supply overnight.

When the domestic load remains below the threshold, energy is stored in a first storage device as descrthed above. When the first storage device is fully charged, further energy may be diverted to charging an energy storage device in the vehicle. Alternatively, charging of the vehicle may be given higher priority, such that the first energy storage device is only charged after the energy storage device in the vehicle is fully charged.

In another variant, the energy storage devices may be interchangeable between the vehicle and the domestic supply, and a householder may choose to swap the storage device in the vehicle with the other storage device, which remains in the house, depending on the relative state of charge of the energy storage devices and the householder's priorities at the time. More than one storage device may be provided in the home, or carried in the electric vehicle, as determined by the householder's requirements.

While some research has been carries out into "smart charging" of electric vehicles, this has been in relation to allowing electricity supply companies to control the overall load. Arrangements have been suggested in which power supply companies can turn on or turn off charging of electric vehicles to enable them to cope with surges in demand. During a surge in demand, the power supply company may switch off charging to electric vehicles, turning the vehicle charging back on when the demand surge has subsided.

0 The present invention differs from those ideas in that it enables the domestic consumption to be smoothed, reducing the size of demand 15 surges to the power companied in the first place. Using the present invention, it is anticipated that a constant supply of 5A would be sufficient to power a typical United Kingdom home. With widespread adoption of the present invention, domestic power demand surges would be significantly reduced. Powering a typical home with an electric vehicle may require a larger supply, such as a constant 1OA supply. Such power supply levels are believed to be well within the capabilities of the present electrical distribution network.

The present invention has several benefits including, but not limited to the following: It removes the need for the electricity distrthution network to have to respond to sudden variations in load.

It offers a purpose-designed alternative to the remote control of individual real loads, avoiding potential short-term conflicts and providing consumer choice.

By varying the desired "threshold" more or less frequently, the utility or the consumer can optimise actual storage in anticipation of predictable peaks and troughs.

The device may be arranged to acts as an uninterruptible supply in the event of distribution failures, of the controller 2 and output conditioner are arranged to react to an absence of power from the electricity distribution network by connecting the energy storage device 4 to the domestic load.

It offers the possthility of charging an exchangeable storage device 0 and provides sufficient energy to power an electric vehicle, whilst limiting the peak domestic power demand to a much mower level than 15 conventionally provided for. r

Claims

CLAIMS1. A device for smoothing domestic electricity consumption, comprising a storage device (4) arranged to store energy from an electricity supply network in response to a power demand from a domestic load falling below a certain threshold, and arranged to release stored energy from the storage device to the domestic load in response to power demand from the domestic load exceeding the certain threshold.
2. A device according to claim 1 comprising: a monitor (1); a controller (2); 0 an input conditioner (3); a storage device (4); and 15 an output conditioner (5), wherein the monitor (1) provides consumption data to the controller (2), and -in response to consumption data indicating consumption below the threshold level, controlling the input conditioner (3) to supply energy from an electricity supply network to the storage device; and -in response to consumption data indicating consumption above the threshold level, controlling the output conditioner (5) to supply energy from the storage device to the domestic load.
3. A device according to claim 2 wherein the consumption data provided to the controller is a one-bit threshold signal indicating consumption exceeding the threshold or indicating consumption below the threshold. -10-
4. A device according to claim 2 wherein the consumption data provided to the controller indicates the magnitude of consumption, and the controller is provided with the value of the threshold, the controller comparing the consumption data with the threshold.
5. A device according to any preceding claim reactive to instantaneous consumption.
6. A device according to any preceding claim, reactive to consumption averaged over a certain period of time.
7. A device according to any of claims 2 to 4, wherein the Q consumption data provided by the monitor (1) represents an averaged consumption over a certain period of time.
8. A device according to any of claims 2 to 4, wherein the controller (2) is arranged to react according to the consumption data averaged over a certain period of time.
9. A device according to claim 2 wherein the energy storage device (4) is a rechargeable battery, the input conditioner (3) provides AC to DC conversion from the electricity supply network to the battery, with appropriate voltage protection and current limitation, and the output conditioner (5) provides DC to AC conversion from the battery to the domestic load, with frequency and phase synchronisation, and power quality control.
10. A domestic energy management system comprising a device according to any preceding claim along with at least one further energy -11 -storage device (4), the at least two energy storage devices (4) being selectively connectable to the remainder of the system.
11. A domestic energy management system according to claim 10, wherein one of the storage devices (4) is installed within an electric vehicle.
12. A domestic energy management system according to claim 10 or claim 11, arranged such that the at least two energy storage devices (4) are selectively connected to the remainder of the system so as to enable at least two of the energy storage devices to store energy when the domestic load remains below the threshold, and to derive energy from at least two of the energy storage devices when the domestic load is above the threshold.
13. A device or system according to any preceding claim arranged to react to an absence of power from an electricity distribution network by connecting the energy storage device (4) to the domestic load.
14. A method for smoothing domestic electricity consumption, wherein energy from an electricity supply network is stored in a storage device (4) in response to power demand from a domestic load falling below a certain threshold, and wherein stored energy is released from the storage device to the domestic load in response to power demand from the domestic load exceeding the certain threshold.15. A method according to claim 14 wherein, with power demand from the domestic load below the threshold, the sum of the power demand from the domestic load and additional power demand caused by the -12 -energy flowing into the storage device (4) is equal to the given threshold, to within a predetermined tolerance range.
15. A method according to claim 14 or claim 15 wherein, with power demand from the domestic load above the threshold, the energy flowing out of the storage device (4) meets the difference between the power demand from the domestic load and the threshold, such that the consumption from the electricity supply network is equal to the given threshold to within a predetermined tolerance range.
16. A method according to claim 14 or 15 in which at least two energy storage devices are provided, and, during a period of domestic load 0 below the threshold, a connected storage device becomes fully charged, a second storage device (4) is connected to be charged. 15
17. A method according to claim 14 or 15 in which at least two energy storage devices are provided, and, during a period of domestic load above the threshold, one storage device becomes fully discharged, a second energy storage device is connected to provide energy to the domestic load.Amendment to the claims have been filed as follows CLAIMS 13 1. A domestic energy management system comprising a device for smoothing domestic electricity consumption, comprising an energy storage device (4) arranged to store energy from an electricity supply network in response to a power demand from a domestic load falling below a certain threshold, and arranged to release stored energy from the storage device to the domestic load in response to power demand from the domestic load exceeding the certain threshold, and at least one further energy storage device (4), the at least two energy storage devices (4) being selectively connectable to the remainder of the system.2. A system according to claim 1, wherein the device for smoothing ____ 15 domestic electricity consumption comprises: a monitor (1); a controller (2); an input conditioner (3); and an output conditioner (5), wherein the monitor (1) is arranged to provide consumption data to the controller (2), and is further arranged: -to respond to consumption data indicating power demand from the domestic load below the threshold level, by controlling the input conditioner (3) to supply energy from an electricity supply network to a connected one of the energy storage device(s); and -to respond to consumption data indicating power demand from the domestic load above the threshold level, by controlling the output conditioner (5) to supply energy from a connected one of the energy storage device(s) to the domestic load.3. A system according to claim 2 wherein the consumption data provided to the controller is a one-bit threshold signal indicating power demand from the domestic load exceeding the threshold or indicating power demand from the domestic load below the threshold.4. A system according to claim 2 wherein the consumption data provided to the controller indicates the magnitude of power demand from the domestic load, and the controller is provided with the value of the threshold, the controller comparing the consumption data with the threshold.5. A system according to any preceding claim reactive to instantaneous power demand from the domestic load.1 6. A system according to any preceding claim, reactive to power demand from the domestic load averaged over a certain period of time.7. A system according to any of claims 2 to 4, wherein the consumption data provided by the monitor (1) represents an averaged power demand from the domestic load over a certain period of time.8. A system according to any of claims 2 to 4, wherein the controller (2) is arranged to react according to the consumption data averaged over a certain period of time.9. A system according to claim 2 wherein the energy storage devices (4) are rechargeable batteries, the input conditioner (3) provides AC to DC conversion from the electricity supply network to a connected one of the batteries, with appropriate voltage protection and current limitation, and the output conditioner (5) provides DC to AC conversion from a connected one of the batteries to the domestic load, with frequency and phase synchronisation, and power quality control.10. A system according to any preceding claim, wherein one of the storage devices (4) is installed within an electric vehicle.11. A domestic energy management system according to any preceding claim, arranged such that the at least two energy storage devices (4) are selectively connected to the remainder of the system so as to enable C at least two of the energy storage devices to store energy when the 1.10 domestic load remains below the threshold, and to derive energy from at least two of the energy storage devices when the domestic load is above the threshold.12. A device or system according to any preceding claim arranged to react to an absence of power from an electricity distribution network by connecting one of the energy storage devices (4) to the domestic load.13. A device or system according to claim 10, wherein the energy storage devices are interchangeable between the vehicle and the domestic supply.14. A method for smoothing domestic electricity consumption, wherein at least two interchangeable energy storage device (4) are provided; energy from an electricity supply network is stored in a connected one of the storage devices (4) in response to power demand from a domestic load falling below a certain threshold, and wherein stored energy is released from a connected one of the storage devices to the domestic load in response to power demand from the domestic load exceeding the certain threshold.15. A method according to claim 14 wherein, with power demand from the domestic load below the threshold, the sum of the power demand from the domestic load and additional power demand caused by the energy flowing into the connected storage device (4) is equal to the given threshold, to within a predetermined tolerance range.16. A method according to claim 14 or claim 15 wherein, with power C demand from the domestic load above the threshold, the energy flowing IC) out of the connected storage device (4) meets the difference between the o power demand from the domestic load and the threshold, such that the consumption from the electricity supply network is equal to the given threshold, to within a predetermined tolerance range.17. A method according to claim 14 or 15 in which, during a period of domestic load below the threshold, a connected storage device becomes fully charged, a second storage device (4) is connected to be charged.
18. A method according to claim 14 or 15 in which, during a period of domestic load above the threshold, one storage device becomes fully discharged, a second energy storage device is connected to provide energy to the domestic load,
19. A method according to any of claims 14-18, wherein one of the energy storage devices (4) is installed within an electric vehicle, and while the domestic load remains below the threshold, energy is stored in a first