GB2543787A

GB2543787A - A domestic controller for an energy management system

Info

Publication number: GB2543787A
Application number: GB1519014.3A
Authority: GB
Inventors: Betz Martin; O'coimin Aubrey
Original assignee: Basic Holdings
Current assignee: Basic Holdings
Priority date: 2015-10-27
Filing date: 2015-10-27
Publication date: 2017-05-03
Also published as: WO2017072215A1; GB201519014D0

Abstract

A controller 100 configured to divert energy generated from a local microgeneration power source 140 which may be a wind turbine, micro hydro system, solar PV cell or a microbial fuel cell, to a local energy reservoir 160 in preference to exporting that energy to a grid connection 150. The controller comprises an input to receiver data reflective of the net power, the differential between available power from the microgeneration source 140 and the power consumed locally and if this is greater that zero the controller triggers activation of a load, which may be a water heater or storage heater or a battery, within the local energy reservoir 160a. The controller may contain feedback circuitry, such as a proportional-integral-derivative (PID) controller, configured to determine the net power at set time intervals.

Description

Title A Domestic Controller for an Energy management system Field

The present application relates to energy management systems and particularly to a domestic controller for an energy management control system that interfaces with various sources of energy and divert available energy based on energy supply and demand.

Background

With the growth in “green” energy sources such as photovoltaic (PV), wind and the like there is a new class of energy supply called microgeneration. Microgeneration technologies include small-scale wind turbines, micro hydro, solar PV systems, microbial fuel cells, ground source heat pumps, and micro combined heat and power installations. These technologies are used in small-scale generation of heat and electric power by individuals, small businesses and communities to meet their own needs, as alternatives or supplements to traditional centralized grid-connected power.

Problems that arise with the use of microgeneration technologies include the fact that the locally generated power may not be sufficient to meet the actual demand at any given time or there are occasions where the locally generated power may be surplus to current demands. To ensure that use of these microgeneration technologies does not interfere with actual power usage requirements, it is known to provide controllers that interface with each of the microgeneration power sources and power from the centralised grid and divert power appropriately. This diversion may include selectively diverting surplus power that is generated by the microgeneration technologies into the national grid and/or supplementing the power that is available from the microgeneration technologies with power from the national grid. Examples of the function of these known controllers is a diversion of surplus power to a designated load, normally a hot water heater, storage heater or the like to allow a user reduce their dependency on the power from the national grid and thereby save energy and minimise utility bills.

Despite the known solutions, there continues to exist a need for improved controllers that can optimise the selective use and source of power within any one location.

Summary

Accordingly, a first embodiment of the application provides a controller in accordance with claim 1 and a system in accordance with claim 14. The application also provides a method as detailed in claim 20. Advantageous embodiments are provided in the dependent claims.

Brief Description Of The Drawings

The present application will now be described with reference to the accompanying drawings in which:

Figure 1 is a schematic showing an exemplary arrangement in accordance with the present teaching.

Figure 2 is a schematic showing further detail on the controller described in Figure 1.

Figure 3 shows an example of the functionality of the controller of Figure 1 or 2.

Detailed Description of the Drawings

The present teaching will now be exemplified with reference to the following schematics. As shown in Figure 1, a controller 100 is installed within a geographical location 130 and interfaces with data provided from an energy meter 120 that is configured to determine the instantaneous value of power at a grid connection point so as to determine whether the actual load 160 within the particular location 130 is being met by power available from local microgeneration power sources 140 or whether the load requires an import of power from the grid 150. It will be appreciate that the data from the energy meter can also be used to determine whether the power that is available from the local microgeneration sources 150 exceeds that required for local consumption and can therefore be exported to the grid. An arrangement per the present teaching has particular application for domestic installations so for the purposes of the present teaching the particular location 130 may be considered a domestic dwelling.

It will be appreciated that the energy meter 120 may provide a simple indication of whether there is a net import or export of energy to the grid at any one time. Variants in the functionality of the energy meter may provide more detailed granularity in that information and may log that information for further analysis so as to allow determination as to the time of day that electricity is being imported or exported. The meter may also include a communication interface port that would permit a remote operator interface with the energy meter to selectively switch the meter or to take a reading from same. The use of these meters is becoming more prevalent with the advent of domestic or local generation of power through microgeneration technologies and the sale of any excess power to the grid 150. The energy meter may be mounted close to the consumer unit of the domestic supply, or in any other location where the exact amount of electricity imported or exported. In other configurations it is possible to provide a connection to a remote platform so as to provide an indication of the energy that is exported or imported at any one site to a device or devices of end users.

As was discussed above, various technologies exist for providing a source of microgeneration power. Examples include:

Wind turbines which produce electricity from available wind;

Photovoltaic Cells (PV) that convert sunlight falling onto them into electricity through the use of semi-conducting material. PV cells are most commonly situated on the roofs of buildings. The efficiency of these cells vary but typically, 7m2 of PV will yield a maximum of 1 kW of electrical power.

Hydro power which converts the flow of water into electrical energy. This can be advantageously employed where the location 130 is close by a source of flowing water such as a river.

Micro Combined Heat and Power (CHP) which produce both electricity and heat for a house or small business. They can be fuelled by gas, diesel or biomass

In the example of Figure 1, the microgeneration power source 140 details two specific examples 140a, 140b but it will be appreciated that one or more different types could be installed in a particular location 130 dependent on the specifics of the location. For the purposes of the present teaching, the microgeneration power source will be considered in the context of a PV source, 140a. A PV power source converts daylight to electricity in the form of a DC power supply. As domestic appliances typically run on AC power-which is what is provided by the grid 150- to allow this PV power be used within the domestic environment, typically the DC power from the PV source will be converted to an AC equivalent which is then synchronised with the frequency of the grid AC supply. The PV source is coupled to the mains or grid supply via a domestic consumer unit or fuse board that provides the interface between the electricity meter and the mains supply.

Within the domestic environment, power is consumed by a plurality of load devices, collectively shown as a load 160. The characteristics of any one component of the collective load 160 will vary. For example a domestic hot water cylinder 160a or storage heater 160b provides both a power load but also a power dump, where excess power can be stored in the form of heat energy until such times as required. Heat may be generated within these devices by powering heating elements using for example IGBT drivers. While not traditionally deployed- and for this reason not shown in Figure 1- batteries are also being discussed as energy storage devices that may be deployed in domestic dwellings. Other load components such as electrical appliance white goods such as televisions, washing machines etc do not have this capacity to store energy for future use.

The discussion heretofore discusses how the controller 100 is provided with data indicative of actual power available and usage and uses that data to monitor power imported from, and exported to the grid. The controller 100 is arranged to identify when there is available surplus power that is being generated locally and which can be diverted to water storage cylinder or other storage device to prevent that excess energy being exported to the grid. Where the locally generated power generates electricity, the production is initially consumed by electrical appliances or devices in the household that are creating a demand for energy. If the household does not consume all of the energy produced by the local power, for example PV panels, the surplus energy will, instead of being sent to the grid, will be used to heat the water in a household water tank, and therefore prevent this energy from going to waste. This maximizes the consumption of self-generated solar power and minimizes the cost of buying energy for domestic hot water. A controller per the present teaching can be retrospectively fitted to homes already with solar PV and a hot water cylinder or other loads or power sources. A controller 100 per the present teaching preferably uses a proportional-integral-derivative controller, PID controller as part of a control loop feedback mechanism. An example of such a PID controller 100 is shown in Figure 2 and continuously, at set intervals in time for example every 3 seconds, calculates an "error value", e, as the difference between a measured process variable, the value of power y provided by the energy meter 120, a first input, and a desired setpoint or reference value y0 which in an preferred application is set at 0 watts, a feedback or second input.

The controller 100 attempts to minimize the error, e, over time by adjustment of power, u, supplied to a heating element 160, to a new value determined by a weighted sum. In the example of a hot water cylinder this value u is the power value that a IGBT driver- or other electrical power circuit- should drive the elements of the cylinder. The PID 100 will try to keep the active power maintained at 0 Watts by modulating the output power to the heater 160. When the calculated output power becomes 0 watts, the PID 100 will stop.

Figure 3 shows in more detail functional components to illustrate the operation of the PID controller 100 where Kp, Td and T, denote the time constants of the proportional, integral and derivative terms respectively. In this schematic, the values of e and u are as described above and the following list the other identified elements:

The error e is the difference between the measured value y and the reference value yo where : e = y0-y

As the PID controller uses a weighted sum methodology each error value e is then fed into a summation value to give en -the sum of the errors- where: 6n = βη-1 + Θ

Using this value it is then possible to compute each of the I, D and P terms: I = TiX en

As was discussed above, the energy meter provides value at distinct intervals- the example given was every three seconds. As a result of which, and different to other PID controllers, a controller 100 per the present teaching uses a set of discrete values instead of continuous data. In this way a substitution of the series un-i - un is used instead of the d/dt shown in Figure 3 D = Td x (un-i - un) P = Kp x e

The calculated output value:

u = P + I + D where P = 0.5 I = 0.3 D = 0.05

On computing a power value u, that value u is the output power that is provided to the hot water cylinder 160.

It will be appreciated that the actual load power that is provided will be dependent on the load resistance of the load 160. To compute this resistance, the present teaching provides a calibration methodology of which the following is a worked example:

Steps Voltage Power

Switch IGBT driver to 0%, read active power 1 consumed and input voltage from energy meter 120 229.8 420 2 Switch IGBT to 100%, read active power and input 230.1 2630 voltage from energy meter 3 Calculate load resistance of heating device 160 by:

Power increased = 2630-420 = 2210W Average voltage = (229.8+230.1)/2 = 229.95V Resistance = (229.95Λ2 )/2210W = 23.93ohm (Power = (VA2)/R)

The "Resistance" is valid if it is in range (17ohm -400ohm). If not, repeat steps (#1-#3)

Repeat steps (#1-#3) until comtroller gets 5 valid resistance values. The load will be considered out of range if routine ran 10 times but still could not get 5 valid values.

Calculate the average load resistance by adding all 4 5 values and then divide result by 5

It will be appreciated that by using a desired setpoint or reference value y0 set at 0 watts, that the present teaching provides a controller which can be used to use excess energy produced by a microgeneration system to heat water or other stored energy materials. The controller is configured to monitor and adjusts the power imported and exported to the grid, ensuring that the exported power remains at virtually zero when the PV system is producing enough energy to cover the demand for domestic electricity and hot water. The controller may be configured to incorporate a timed boost function, which can be set for multiple days of the week so as to ensure that the consumer can provide additional heating when desired.

To provide a user with information, the controller may be configured with a display panel such as a back-lit LCD display with different Light OFF times available so as to display information about the operating mode, settings, Wi-Fi connection etc. By incorporating a log, it is possible to allow interrogation of the current imported, exported and diverted power levels. The user may be provided with the capacity to vary the diverted load from 0-100%.

The words comprises/comprising when used in this specification are to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers , steps, components or groups thereof.

Claims

1. A domestic energy controller configured to divert energy generated from a local microgeneration power source to a local energy reservoir in preference to exporting that energy to a grid connection, the controller comprising: a first input configured to receive input data reflective of nett power, the nett power being reflective of a differential between available power from the local microgeneration power source and power consumed locally; a first output configured, on determination that the nett power is greater than zero, to trigger activation of a load within the local energy reservoir in response to determination that the available power from the local microgeneration power source is currently greater than the power consumed locally.

2. The controller as claimed in claim 1 configured to interface with a remote operator and provide data indicative of the diverted power to the remote operator.

3. The controller of any preceding claim comprising feedback loop circuitry, the controller configured to determine at set time intervals the nett power and a reference value set point and to vary the load applied within the local energy reservoir to equalise the values of the nett power and the reference value set point.

4. The controller of claim 3 wherein the reference value set point is 0 watts.

5. The controller of claim 3 or 4 wherein the set time interval is three seconds.

6. The controller of any preceding claim wherein the activation of the load effects a modulation of output power provided to the local energy reservoir.

7. The controller of claim 3 wherein the feedback loop circuitry comprises a proportional-integral-derivative controller.

8. The controller of claim 7 wherein the proportional-integral-derivative controller is configured to use a set of discrete values in effecting the trigger of activation of the load.

9. The as claimed in any preceding claim configured to determine when the local energy reservoir is incapable of receiving additional power and to deactivate the load on said determination.

10. The controller as claimed in any preceding claim configured to determine when the local energy reservoir is incapable of receiving additional power and to activate a load on a second local energy reservoir on said determination.

11. The controller as claimed in any preceding claim wherein the activated load is dependent on a load resistance within the local energy reservoir.

12. The controller of claim 11 wherein the controller includes calibration data indicative of the load resistance within the local energy reservoir.

13. The controller of claim 12 wherein the controller includes a processor configured to carry out method steps of: Provide a zero load to the local energy reservoir and measure the input data reflective of nett power and determine a corresponding value for input voltage; Provide a maximum load to the local energy reservoir and measure the input data reflective of nett power and determine a corresponding value for input voltage; Calculate a load resistance based on an increase in power between the nett power at zero load and maximum load and an average voltage as measured on providing the zero load and maximum load, the calculated load resistance being determined as a valid load resistance on falling within a predetermined range.

14. An energy management system comprising the controller as claimed in any preceding claim and an energy meter, the energy meter configured to provide the first input to the controller.

15. The system of claim 14 wherein the energy meter is configured to communicate over a wireless communication channel with the controller.

16. The system of claim 14 or 15 wherein the energy meter is configured to communicate over a wired network with the controller.

17. The system of any one of claims 14 to 16 configured on a periodic basis to effect an activation of the load fully to determine changes in the value provided by the energy meter to establish that the energy meter still operates correctly.

18. The system of any one of claims 14 to 17 wherein the microgeneration power source comprises at least one of a wind turbine, micro hydro system, solar PV system, microbial fuel cell, ground source heat pump, and micro combined heat and power installation.

19. The system of any one of claims 14 to 18 wherein the local energy reservoir comprises at least one of a water cylinder or a storage heater or a battery.

20. A method of diverting energy generated from a local microgeneration power source to a local energy reservoir in preference to exporting that energy to a grid connection, the method comprising: receiving input data reflective of nett power, the nett power being reflective of a differential between available power from the local microgeneration power source and power consumed locally; determining that the nett power is greater than zero, and on effecting said determination triggering activation of a load within the local energy reservoir to maintain the nett power at a zero level.

21. A computer program which when executed on a processor is configured to carry out the method of claim 20.