GB2452314A

GB2452314A - Calculating the individual energy usage of lights controlled and monitored by a lighting controller

Info

Publication number: GB2452314A
Application number: GB0716973A
Authority: GB
Inventors: Paul Mans
Original assignee: CP Electronics Ltd
Current assignee: CP Electronics Ltd
Priority date: 2007-08-31
Filing date: 2007-08-31
Publication date: 2009-03-04
Anticipated expiration: 2027-08-31
Also published as: GB0716973D0; GB2452314B

Abstract

A method of monitoring energy usage in a lighting system controlled by at least one lighting controller 2 arranged to control a plurality of lighting devices 3. Comprising: measuring the electrical power drawn by the lighting controller 2 for distribution to the plurality of lighting devices 3, receiving from the lighting controller 2 information indicative of the status of each lighting device, and calculating an energy usage value for each lighting device based on the measured electrical power and the status of the lighting device. The method has the advantage that the energy consumption of individual lighting devices 3 can be determined using a single energy measurement device.

Description

LIGHTING SYSTEMS

Field of the Invention

This invention relates to a method of monitoring energy usage in a lighting system.

Background to the Invention

Energy measurement and monitoring is becoming an increasingly important activity in the drive to reduce energy usage in buildings. Successful energy monitoring allows consumption to be logged and energy saving plans to be introduced and measured.

Furthermore on buildings which are sub-let, energy usage measurement provides a mechanism for measuring energy charges to individual areas. As 40% of energy use in a typical office environment is lighting, this represents a major area where energy usage can be monitored. Systems in use today will monitor the power used on individual circuits, typically located at the electrical distribution board and using power clamps to take readings. The information is either stored locally or reported using some form of wired or wireless communication.

Separately, the use of lighting control systems is widespread in commercial and other premises to switch lighting and control the level of lighting. Typically these systems might comprise several multi-channel switching devices (lighting control modules or LCMs), presence detectors, light detectors, other forms of controller and a coordinator in each area, commonly called an area controller. The devices are generally connected together on some form of network to allow communication between detecting and controlling devices. A computer can also be connected, via some form of gateway, to the lighting control system to display the status of devices on the system, and also to allow the operation of the system to be modified. In some circumstances, the lighting control system can also be used for the control of blinds and HVAC (heating, ventilation and air conditioning) systems.

The provision of the known type of energy-usage monitoring system in addition to a io lighting control system significantly increases the cost of the system, as well as complicating installation. The present invention, at least in its preferred embodiments, seeks to address this problem.

Summary of the Invention

According to the present invention, there is provided a method of monitoring energy usage in a lighting system controlled by at least one lighting controller arranged to control a plurality of lighting devices, the method comprising: measuring the electrical power drawn by the lighting controller for distribution to the plurality of lighting devices; receiving from the lighting controller information indicative of the status of each lighting device; and calculating an energy usage value for each lighting device based on the measured electrical power and the status of the lighting device.

Thus, according to this method, there is no need to measure the power drawn by each individual device controlled by the system. Instead, the power drawn by the lighting controller is measured and the energy usage is calculated from the status of each lighting device. In this way, a power measuring device is only required for the lighting controller, rather than each device. The invention therefore integrates energy monitoring into a lighting control system.

Energy measurement may be taken at a lighting control module or an area controller, for example. Thus, the lighting controller may be a lighting control module or an area controller for example. At the lighting control module the resolution of the energy measurement allows readings for individual output channels. At the area controller, readings reflect the usage of energy for an individual circuit, which may be a lighting circuit or any other circuit, such as a ring main. At the lighting control module the method of measurement may be a shunt resistance because the supply can easily be broken internally and the powers are quite low. At the area controller the method of measurement may be a power clamp, allowing measurement to take place without splitting conductors.

It is possible for the power measurements to be taken at both the lighting control module and the area controller in order that the same system can measure the power consumption of other electrical circuits, such as HVAC systems, ring mains and the like.

The status of the lighting devices may include whether they are on or off. The status may also include their dimming level, where appropriate.

The method may further comprise an occasional calibration step of activating sequentially each of the lighting devices controlled by the lighting controller and measuring the electrical power drawn by the lighting controller. The calibration step may be carried out periodically, for example at the same time every day. Alternatively or in addition, the calibration step may be carried out when a period of inactivity of the lighting devices has been identified, for example when all of the lights have been off for a predetermined period of time.

The invention extends to a lighting control system configured to operate in accordance with the method of the invention.

Viewed from a further aspect, the invention provides a lighting controller comprising a plurality of controllable outputs each arranged to control a respective lighting device. The lighting controller further comprises an energy measurement device configured to measure the electrical power drawn by the lighting controller for distribution to the plurality of lighting devices. The lighting controller is arranged to calculate an energy usage value for each lighting device based on the measured electrical power and the status of each lighting device.

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which Figure 1 shows a lighting control system according to an embodiment of the invention.

Detailed Description of Embodiments

Figure 1 shows a lighting control system according to an embodiment of the invention.

The lighting system extends over three floors of a building, with an area controller I provided for each floor. The area controller I is shown for each of the three floors, but for reasons of clarity only the details of the remaining components of floor three are shown; the arrangement of the other two floors is similar.

As shown in Figure 1, each floor is provided with at least two lighting control modules 2, each of which is arranged to control up to ten light fittings (or luminaires) 3. The lighting control modules 2 and the area controllers 1 are connected by bus wiring which allows both power and data to be communicated between the lighting control modules 2, the area controllers I and a front end computer 4 provided at the reception or plant area of the building.

A novel approach has been adopted to allow the measurement of energy usage for individual output channels on the lighting control module 2 using a single measurement device, such as a shunt resistance or a power clamp. The power measurement device is incorporated into the lighting control module 2. The device measures the energy used by the entire lighting control module 2. During normal operation one or many channels of the lighting control module 2 are operational and using energy whilst the lighting control module 2 itself draws a quiescent power. The lighting control module 2 sends data to the front end computer 4 indicating which of the outputs of the lighting control module 2 is operational, the dimming level of each output and the instantaneous power drawn by the lighting control module 2.

Energy measurement software running on the front end computer 4 records the total power consumption for the lighting control module 2, together with the status of the individual outputs including, where applicable, the dimmed level of each fitting. From this information the software is able to apportion the power consumption to the individual light fittings 3 and record the energy usage of each fitting 3. In this way, the front end computer 4 can record the energy usage of each fitting 3 over time, from which an energy saving strategy for the end user can be suggested.

The energy measurement software is arranged to sense a suitable time when all of the output channels are off, typically a usage pattern will be analysed, and then run a calibration routine. On a periodic basis calibration energy measurements are taken for the lighting control module 2 quiescent power, plus the power taken by each of the output channels at a series of discrete dimming levels (where applicable). This data is recorded and updated to reflect the differing lifetime characteristics of a luminaire 3. The front end software also allows the user to schedule the calibration measurements, if required. Using the total measured consumption when the outputs are on; the status of the outputs; and the recorded measurements during calibration, the total consumption for each luminaire 3 can be deduced with relatively high accuracy.

It is possible for the energy measurement software to run on the lighting control module 2, rather than on the front end computer 4. In this case, the consumption data, rather than the raw data, is reported via the lighting control system bus to the front end computer 4.

Furthermore there is provision to calibrate the actual energy measurement circuitry. A calibration device can be plugged into a spare channel of the lighting control module 2 or to the input of the area controller device 1. Calibration mode is entered via the front end software, via commissioning software running on a portable computer that is plugged into the lighting control module 2 or using an infrared handset. The calibration device has a known consumption dictated by a precision resistance which is used by the energy measurement software to calibrate its readings. It is also possible for the calibration device to be permanently fitted to an extra, internal channel for calibration purposes.

This invention allows a lighting control system to monitor and record the energy usage of individual light fittings or complete lighting or other electrical circuits. The results can be collated using the same computer front end as used for the lighting control system.

In summary, a method of monitoring energy usage in a lighting system controlled by at least one lighting controller 2 arranged to control a plurality of lighting devices 3. The method comprises measuring the electrical power drawn by the lighting controller 2 for distribution to the plurality of lighting devices 3. The method further comprises receiving from the lighting controller 2 information indicative of the status of each lighting device and calculating an energy usage value for each lighting device based on the measured electrical power and the status of the lighting device. The method has the advantage that the energy consumption of individual lighting devices 3 can be determined using a single energy measurement device.

Claims

Claims I. A method of monitoring energy usage in a lighting system controlled by at least one lighting controller arranged to control a plurality of lighting devices, the method comprising: measuring the electrical power drawn by the lighting controller for distribution to the plurality of lighting devices; receiving from the lighting controller information indicative of the status of each lighting device; and calculating an energy usage value for each lighting device based on the measured electrical power and the status of the lighting device.
2. A method as claimed in claim I further comprising an occasional calibration step of activating sequentially each of the lighting devices controlled by the lighting controller and measuring the electrical power drawn by the lighting controller.
3. A lighting control system configured to operate in accordance with the method of claim! or2.
4. A lighting controller compnsing a plurality of controllable outputs each arranged to control a respective lighting device, wherein the lighting controller further comprises an energy measurement device configured to measure the electrical power drawn by the lighting controller for distribution to the plurality of lighting devices; and the lighting controller is arranged to calculate an energy usage value for each lighting device based on the measured electrical power and the status of each lighting device.
5. A method of monitoring energy usage in a lighting system substantially as hereinbefore described with reference to the accompanying drawings.
6. A lighting system or a lighting controller substantially as hereinbefore described with reference to the accompanying drawings.

6. A lighting system or a lighting controller substantially as hereinbefore described with reference to the accompanying drawings.

--

Claims I. A method of monitoring energy usage in a lighting system controlled by at least one lighting controller arranged to control a plurality of lighting devices, the method comprising: measuring the electrical power drawn by the lighting controller for distribution to the plurality of lighting devices; receiving from the lighting controller information indicative of the status of each lighting device; and calculating an energy usage value for each lighting device by apportioning the power drawn by the lighting controller based on the measured electrical power and the status of the lighting device. * .*

2. A method as claimed in claim 1 further comprising an occasional calibration step of activating sequentially each of the lighting devices controlled by the lighting controller 15 and measuring the electrical power drawn by the lighting controller. S...

S

3. A lighting control system configured to operate in accordance with the method of :: claim 1 or2.

S

4. A lighting controller comprising a plurality of controllable outputs each arranged to control a respective lighting device, wherein the lighting controller further comprises an energy measurement device configured to measure the electrical power drawn by the lighting controller for distribution to the plurality of lighting devices; and the lighting controller is arranged to calculate an energy usage value for each lighting device by apportioning the power drawn by the lighting controller based on the measured electrical power and the status of each lighting device.

5. A method of monitoring energy usage in a lighting system substantially as hereinbefore described with reference to the accompanying drawings.