Field of the Invention

This invention relates to a system and a method for energy audit of chiller plants. Particularly, this invention relates to a system and a method for obtaining data from new or existing sensors in a chiller plant and analysing the data efficiently.

Prior Art

From time to time, the relevant agency may issue notices for an energy audit report. Upon receiving the notices, the building owner has to engage third parties to conduct energy audit. Current methods of energy audit conducted by third parties involve having staffs stationed at the premises of the building to obtain readings of the electrical systems or devices. As the periodic readings over a certain period of time are required, such energy audit is labour intensive and time consuming. For example, a central chiller plant energy audit includes installation of following sensors: 1 . Probe type temperature sensors measuring chilled water supply and return temperature as well as condenser water supply and return temperature; 2. Ultrasonic flow meters; 3. Equipment for power measurement; and 4. Pressure sensors.

Each sensor is connected to a logger to measure changes in the parameters over time. The data logs are then downloaded after specific time. Data from each logger is converted to certain parameter being measured (i.e. a temperature probe is actually measuring a resistance - as such, the logger only includes resistance information that needs to be put in an equation unique for each sensor to deliver temperature reading). This step is done manually. Data from different loggers are combined manually to one database to create a single data base. Different parameters are then correlated. For example, temperature and flow is correlated to calculate Cooling Load and Cooling load and energy is correlated to calculate efficiency.

The mentioned process has several limitations. First, the installation process takes time. Setting up each logger and connecting each sensor to each logger is cumbersome.

Secondly, the engineer has no way of knowing whether the measured parameter is correct. This is because the parameters only make true sense if correlated with each other. In other words, it is difficult to determine chilled water supply temperature in itself l without correlating it to chilled water return temperature, chilled water flow and energy consumption of all equipment. Hence, this is technically challenging.

Thirdly, there is no way of knowing whether measurements are performed on correct equipment. This is because the engineers may setup measurement for one set of equipment, but operators chose to change operating equipment.

Fourthly, if the data obtained is in error due to any of the issues raised above, a re-audit is required.

The current products available which use limited wireless capability are not created for speed of installation and ease of data manipulation on site. They are developed to be pure monitoring devices which are provided as a 1 time installation and integration to a monitoring device such as a building management system (BMS). The installation of wireless meters can be done by qualified personnel and integration to monitoring device is done by a qualified software engineer. As such, these installations can be done only at high cost and not at scale. In addition, each wireless product is currently compatible to its own platform. For example, it is hard to combine data from a wireless pressure sensor from one supplier to the flow data from a wireless flow meter from a second supplier.

Therefore, those skilled in the art are striving to provide an improved system and method for auditing chiller plants that is less complex and allows flexibility to be used in multiple chiller plant audits.

Summary of the Invention

The above and other problems are solved and an advance in the art is made by a system and method in accordance with this invention. A first advantage of the system and method in accordance with this invention is that the system and method can be used in multiple chiller plants. A second advantage of the system and method in accordance with this invention is that the system and method can be provided at a lower cost since the wireless devices can be easily installed and uninstalled. A third advantage of the system and method in accordance with this invention is that the system and method can be installed by less qualified workforce. This increases productivity as the more qualified workforce can be redeployed to handle jobs that better commensurate their qualification. A fourth advantage of the system and method in accordance with this invention is that the system and method can use existing sensors where applicable. Hence, the system and method in accordance with this invention can be implemented to existing chiller plants. A first aspect of the invention relates to a chiller plant energy audit system comprising a plurality of wireless devices, a plurality of site servers, and a main server communicatively connected to the plurality of site servers, and each of the plurality of site servers is communicatively connected to a few of the plurality of wireless devices that are deployed at the same site of the site server. Each of the plurality of wireless devices includes a processor, a memory, a low power long range wireless transmission module, a power source, a Liquid Crystal Display (LCD), an RS485 converter, an RS232 converter, a 4 Channel 24bit Analogue Digital Converter (ADC), and a 1 Gbit 4mA to 20mA output port, wherein the RS485 converter and the RS232 converter are adapted to receive signals from flow and power meters, 10k thermistor input port of the 4 Channel 24bit ADC is adapted to receive signals from a temperature sensor; 4mA to 20mA input port and 0V to 10V input port of the 4 Channel 24bit ADC are adapted to receive analogue signals. Each of the plurality of wireless devices further includes instructions stored on the memory and executable by the processor to: sample data receive from the RS485 converter, RS232 converter, 4 Channel 24bit Analogue Digital Converter (ADC) according to a sampling interval; store the sampled data with a time stamp; and transmit a data package to the site server including the identity (ID) of the wireless device, current sampled data (T), first previous sampled data (T-1 ) and second previous sampled data (T-2).

According to an embodiment of the first aspect of the invention, each of the site servers includes a processor, a memory, a data structure stored on the memory and instructions stored on the memory and executable by the processor to: monitor and receive the data packages from the connected wireless devices; update the data structure according to the data packages received; transmit site data package to the main server; and wherein the data structure includes wireless device ID and each wireless ID includes sensors data, and time stamp.

According to an embodiment of the first aspect of the invention, the site data package includes site server ID, wireless device ID, sensor data and time-stamp of the 3 current readings (T, T-1 and T-2).

According to an embodiment of the first aspect of the invention, the instruction to update the data structure according to the data packages received further comprises instructions stored on the site server to: determine whether data packages have been received from required wireless devices that are registered on a record stored on the memory of the site server; in response to a failure to receive a data package from an error connected wireless devices, use the previous data package of the error wireless device to fill in the data structure for the current time stamp and mark the ID of the error wireless device; and update the data structure by entering the readings received from the wireless devices.

According to an embodiment of the first aspect of the invention, the instruction to transmit site data package to the main server further comprises instructions stored on the site server to: determine whether each of the ID of the error wireless device has been marked consecutively for 3 times; and in response to determining an ID being marked consecutively for 3 times, amend the sensors data associated to the ID to pre-determined value.

According to an embodiment of the first aspect of the invention, the predetermined value is an unusual value. According to another embodiment of the first aspect of the invention, the pre-determined value is 99999.

According to an embodiment of the first aspect of the invention, the main server comprises a processor, a memory, and instructions stored on the memory and executable by the processor to: receive site data packages from the plurality of site servers; arrange the site data packages in a master data structure; and analyse the master data structure according to inputs from a user.

According to an embodiment of the first aspect of the invention, the instruction to analyse the master data structure according to inputs from a user comprises instructions stored on the main server to: in response to an input to determine error wireless device, perform a lookup in the master data structure for the predetermined value and retrieve the IDs associated to the predetermined value.

According to an embodiment of the first aspect of the invention, the instruction to analyse the master data structure according to inputs from a user comprises instructions stored on the main server to: in response to an input to analyse sensors data, receive one or more selections on a type of data in the sensors data, retrieve and display formulas associated to the selected type of data, receive a selected formula, and display a result based on the selected formula and selected type of data.

According to an embodiment of the first aspect of the invention, the instruction to retrieve and display formulas associated to the selected type of data further comprises instructions stored on the main server to: receive a formula edit request from the user; display a formula editor page comprising a plurality of mathematical expressions on a top region of an editor box; and creating a new formula as and when the user drag and drop a mathematical expression to a central region of the editor box.

A second aspect of the invention relates to a method according to the chiller plant energy audit system described in the first aspect of the invention.

A third aspect of the invention relates to a site server of a chiller plant energy audit system comprising a plurality of wireless devices communicatively connected to the site server, and a main server communicatively connected to the site server, wherein each of the plurality of wireless devices includes a processor, a memory, a low power long range wireless transmission module, a power source, a Liquid Crystal Display (LCD), an RS485 converter, an RS232 converter, a 4 Channel 24bit Analogue Digital Converter (ADC), and a 16bit 4mA to 20mA output port, a data structure having wireless device ID and each wireless ID includes sensors data, and time stamp, wherein the RS485 converter and the RS232 converter are adapted to receive signals from flow and power meters, 10k thermistor input port of the 4 Channel 24bit ADC is adapted to receive signals from a temperature sensor; 4mA to 20mA input port and 0V to 10V input port of the 4 Channel 24bit ADC are adapted to receive analogue signals. The site server includes a processor, a memory, a site data structure stored on the memory and instructions stored on the memory and executable by the processor to: monitor and receive a data packages from the connected wireless devices, each data package comprises the identity (ID) of the wireless device, current sampled data (T), first previous sampled data (T-1 ) and second previous sampled data (T-2); update the data structure according to the data packages received; transmit site data package to the main server; and wherein the data structure includes wireless device ID and each wireless ID includes sensors data, and time stamp.

According to an embodiment of the third aspect of the invention, the site data package includes site server ID, wireless device ID, sensor data and time-stamp of the 3 current readings (T, T-1 and T-2).

According to an embodiment of the third aspect of the invention, the instruction to update the data structure according to the data packages received further comprises instructions to: determine whether data packages have been received from required wireless devices that are registered on a record stored on the memory of the site server; in response to a failure to receive a data package from an error connected wireless devices, use the previous data package of the error wireless device to fill in the data structure for the current time stamp and mark the ID of the error wireless device; and update the data structure by entering the readings received from the wireless devices. According to an embodiment of the third aspect of the invention, the instruction to transmit site data package to the main server further comprises instructions to: determine whether each of the ID of the error wireless device has been marked consecutively for 3 times; and in response to determining an ID being marked consecutively for 3 times, amend the sensors data associated to the ID to pre-determined value.

According to an embodiment of the third aspect of the invention, the predetermined value is an unusual value. According to another embodiment of the third aspect of the invention, the pre-determined value is 99999.

A fourth aspect of the invention relates to a main server of chiller plant energy audit system comprising a plurality of wireless devices, a plurality of site servers to the main server, each of the plurality of site servers is communicatively connected to a few of the plurality of wireless devices that are deployed at the same site of the site server, wherein each of the plurality of wireless devices includes a processor, a memory, a low power long range wireless transmission module, a power source, a Liquid Crystal Display (LCD), an RS485 converter, an RS232 converter, a 4 Channel 24bit Analogue Digital Converter (ADC), and a 16bit 4mA to 20mA output port, wherein the RS485 converter and the RS232 converter are adapted to receive signals from flow and power meters, 10k thermistor input port of the 4 Channel 24bit ADC is adapted to receive signals from a thermometer sensor; 4mA to 20mA input port and 0V to 10V input port of the 4 Channel 24bit ADC are adapted to receive analogue signals , each of the wireless devices is configured to transmit a data package to the site server including the identity (ID) of the wireless device, current sampled data (T), first previous sampled data (T-1 ) and second previous sampled data (T-2) and each of the site servers is configured to transmit site data packages to the main server, the site data package includes site server ID, wireless device ID, sensor data and time-stamp of the 3 current readings (T, T-1 and T-2). The main server comprises a processor, a memory, and instructions stored on the memory and executable by the processor to: receive site data packages from the plurality of site servers; arrange the site data packages in a master data structure; and analyse the master data structure according to inputs from a user.

According to an embodiment of the fourth aspect of the invention, the instruction to analyse the master data structure according to inputs from a user comprises instructions to: in response to an input to determine error wireless device, perform a lookup in the master data structure for the predetermined value and retrieve the IDs associated to the predetermined value. According to an embodiment of the fourth aspect of the invention, the instruction to analyse the master data structure according to inputs from a user comprises instructions to: in response to an input to analyse sensors data, receive one or more selections on a type of data in the sensors data, retrieve and display formulas associated to the selected type of data, receive a selected formula, and display a result based on the selected formula and selected type of data.

According to an embodiment of the fourth aspect of the invention, the instruction to retrieve and display formulas associated to the selected type of data further comprises instructions to: receive a formula edit request from the user; display a formula editor page comprising a plurality of mathematical expressions on a top region of an editor box; and creating a new formula as and when the user drag and drop a mathematical expression to a central region of the editor box.

Brief Description of the Drawings

The above advantages and features in accordance with this invention are described in the following detailed description and are shown in the following drawings:

Figure 1 illustrating an overview of the system for performing the processes in accordance with an embodiment this invention;

Figure 2 illustrates a processing system of a server for performing processes to provide a system in accordance with an embodiment this invention;

Figure 3 illustrating an example of a processing system in a wireless device for performing processes in accordance with an embodiment of this invention;

Figure 4 illustrating a process of installing the wireless device in accordance with an embodiment of this invention;

Figure 5 illustrating a process performed by a site server in accordance with an embodiment of this invention;

Figure 6 illustrating a data structure prepared by the site server in accordance with an embodiment of this invention;

Figure 7 illustrating a process performed by the site server in accordance with an embodiment of this invention; Figure 8 illustrating an example of a GUI for selecting data and formula in accordance with an embodiment of this invention; and

Figure 9 illustrating an example of a formula editing page in accordance with an embodiment of this invention.

Detailed Description

This invention relates to a system and a method for energy audit of chiller plants. Particularly, this invention relates to a system and a method for obtaining data from existing or new sensors in a chiller plant and analysing the data efficiently.

As mentioned above, the current sensors available use limited wireless capability that are not created for speed of installation and ease of data manipulation on site. These wireless sensors are developed to be pure monitoring devices which are meant for a 1 time installation and integration to a monitoring device such as a building management system (BMS). The installation of wireless meters can be done by qualified personnel and integration to monitoring device is done by a qualified software engineer. As such, these installations can be done only at high cost and not at scale.

Based on current state of the art, no one has provided a solution for wireless audit of central chiller plants.

Advantageously, the system and method in accordance with this invention is that any contractor/engineer with limited education can use the system and method of this invention to gather information for central chiller plant energy audit. The system and method according to this invention offers the ability of performing energy audits of central chiller plant at fraction of time and cost by allowing conversion of a multitude of signals to wireless signal (reducing equipment installation cost) as well as creating a platform for ease of data collection and processing for site engineers.

It is envisioned that a system and method in accordance with embodiments of this invention may be used to assist in providing energy audit of a chiller plant. The system and method comprises 2 parts, namely, collection and analysis.

The collection part comprises wireless devices that can be implemented directly to existing sensors to obtain readings or attached to readily available sensors in the market if no existing sensor is installed. The wireless devices are easily adaptable to receive readings from various types of sensors that are commonly used in a chiller plant. Further, the wireless devices comprise universal connection that allows plug and play connectivity. This ensures seamless connection of the wireless devices to the sensors.

The analysis part comprises processes to read the data received from the wireless devices and provide an analysis on the data received. The processes include determining the performance of the chiller plant based on configurable formulas or predetermined formulas. A detailed description of the system and/or method in accordance with embodiments of this invention will now be described as follows.

Figure 1 illustrates an overview of the system 100 for performing the processes in accordance with this invention. The system 100 includes a main server 1 10, and a number of wireless modules 120. The wireless modules 120 are communicatively connected to the main server 1 10 via a network 130. These wireless modules 120 are installed at one or more chiller plants located at different sites 160 and 170. Network 130 is a network such as the Internet that allows processing systems to communicate with one another. At each site, the wireless modules are communicatively connected to a site server or router 140 prior to connecting to the network.

The main server 1 10 is a typical processing system such as a desktop computer, laptop computer, or other computer terminal capable of handling large data storage and processing need. Main server 1 10 is communicatively connected to network 130 via either a wired or wireless connection to retrieve data from wireless devices 120 and/or site server/router 140. One skilled in the art will recognise that more than one server 1 10 may be used without departing from the invention. Further details of the server 1 10 will be described below with reference to figure 2.

Processes stored as instructions in a media that are executed by a processing system in main server 1 10 or site server 140 provide the method and/or system in accordance with this invention. The instructions may be stored as firmware, hardware, or software. Figure 2 illustrates processing system 200 such as the processing system in main server 1 10 or site server 140 that execute the instructions to perform the processes for providing a method and/or system in accordance with this invention. One skilled in the art will recognize that the exact configuration of each processing system may be different and the exact configuration of the processing system in each device may vary. Thus, processing system 200 shown in Figure 2 is given by way of example only.

Processing system 200 includes Central Processing Unit (CPU) 205. CPU 205 is a processor, microprocessor, or any combination of processors and microprocessors that execute instructions to perform the processes in accordance with the present invention. CPU 205 connects to memory bus 210 and Input/ Output (I/O) bus 215. Memory bus 210 connects CPU 205 to memories 220 and 225 to transmit data and instructions between the memories and CPU 205. I/O bus 215 connects CPU 205 to peripheral devices to transmit data between CPU 205 and the peripheral devices. One skilled in the art will recognize that I/O bus 215 and memory bus 210 may be combined into one bus or subdivided into many other busses and the exact configuration is left to those skilled in the art.

A non-volatile memory 220, such as a Read Only Memory (ROM), is connected to memory bus 210. Non-volatile memory 220 stores instructions and data needed to operate various sub-systems of processing system 200 and to boot the system at start-up. One skilled in the art will recognize that any number of types of memory may be used to perform this function.

A volatile memory 225, such as Random Access Memory (RAM), is also connected to memory bus 210. Volatile memory 225 stores the instructions and data needed by CPU 205 to perform software instructions for processes such as the processes required for providing a system in accordance with this invention. One skilled in the art will recognize that any number of types of memory may be used as volatile memory and the exact type used is left as a design choice to those skilled in the art.

I/O device 230, keyboard 235, display 240, memory 245, network device 250 and any number of other peripheral devices connect to I/O bus 215 to exchange data with CPU 205 for use in applications being executed by CPU 205. I/O device 230 is any device that transmits and/or receives data from CPU 205. Keyboard 235 is a specific type of I/O that receives user input and transmits the input to CPU 205. Display 240 receives display data from CPU 205 and display images on a screen for a user to see. Memory 245 is a device that transmits and receives data to and from CPU 205 for storing data to a media. Network device 250 connects CPU 205 to a network for transmission of data to and from other processing systems.

Wireless device

The wireless devices 120 refer to any apparatus having a communication interface to allow transferring and receiving of information over a wired or wireless connection. Figure 3 illustrates the block diagram of the wireless device. The wireless device 120 can receive and transmit data, execute software applications. The wireless device 120 comprises a processor 310, memory 320, transceiver 330, input/output ports 340, display 350 and power unit 360.

The processor 310 is a processor, microprocessor, microcontroller, application specific integrated circuit, digital signal processor (DSP), programmable logic circuit, or other data processing device that executes instructions to perform the processes in accordance with the present invention. The processor 310 has the capability to execute various applications that are stored in the memory 320.

The memory 320 may include read-only memory (ROM), random-access memory (RAM), electrically erasable programmable ROM (EEPROM), flash cards, or any memory commonly used for computers.

Network device 330 connects processor 310 to a network for transmission of data to and from other processing systems. Network device 330 is a low power long range wireless transmission modules. In order to achieve low power consumption, the network device 330 is communicatively connected to a site server or router 140 instead of directly to the main server 1 10. In order words, the wireless device 120 is configured to only obtain readings from the sensors and transmit the readings to the main server 120 via the site server or router 140.

One or more input/output (I/O) ports 340 can be configured to allow the processor 310 to communicate with and control from various I/O devices. Peripheral devices that may be connected to wireless device 120 via the I/O ports 340 include a USB storage device, an SD card or other storage device for transmitting information to or receiving information from the wireless device 120. In addition to updating applications stored on memory 320 or installing new applications onto the memory via the network device 330, a user may alternatively install new applications or update applications on the memory 320 through a user interface such as a USB via the I/O ports 340. I/O ports 340 also include necessary connectors to connect to a plurality of sensors for monitoring chiller plant. This includes 4 channel 24bit analog-to-digital converter (ADC) 341 , RS485 converter 342, RS232 converter 343, and 16bit 4mA to 20mA converter 344.

Display 350 receives display data from processor 310 and display images on a screen for a user to see. Display 350 may be a low power liquid crystal display (LCD) showing a variety of information for ease of identification and trouble shooting. These include identity data (ID) of the wireless device, readings received from the sensor (i.e. value being transmitted to the server/router or main server) and battery status. The wireless device 120 is powered by the power unit 360. For this invention, 2 AA batteries are used which is able to last for 2 years in normal operations.

One skilled in the art will recognize that other features may be included in the wireless device 120. Further, the components in wireless device 120 may be replaced by other components that perform similar functions. In brief, the wireless device 120 as shown in figure 3 is considered merely illustrative and non-limiting.

Essentially, the wireless device 120 is a multi-input data acquisition module, designed to interface with industrial sensors and measuring equipment. The wireless device 120 comes with an on-board processor and low power long range wireless transmission modules. It is powered with 2xAA batteries and is designed to last for 2 years in normal operations. The wireless device 120 converts analogue (resistance, 4-20 mA, 0-10 Volts) and digital (RS485, RS232) signals to wireless packages. As the wireless device 120 is battery driven, it is easy to install and installer does not need to lay long cables to connect the wireless device to a power source. The small LCD provided on the wireless device allows the installer to control the ID of the wireless device and parameters measured.

Although the wireless device 120 has wireless connectivity, the wireless device 120 also has wired connectivity to connect to new sensors or existing sensors on site which are currently connected to Building Management System (BMS) as well as ability to send out equivalent of some of the signal received. By splitting the signals, both existing BMS as well as server/router can receive the same signal. This is achievable via the input port 4mA to 20mA of the 4 Channel 24bit ADC 341 and the output port of the 16bit 4mA to 20mA 344. Particularly, the existing sensor for measuring pressure would be connected to the input port 4mA to 20mA of the 4 Channel 24bit ADC 341 . The signal received would be directed to the output port of the 16bit 4mA to 20mA 344 and stored in the memory 320 for forwarding to the main server 1 10 thereafter.

Briefly, the RS485 converter 342 and RS232 converter 343 are for receiving signals from flow and power meters; input port 10k thermistor of 4 Channel 24bit ADC 341 receives signals from the thermometer sensor; input ports 4mA to 20mA and 0V to 10V of the 4 Channel 24bit ADC 341 are for receiving analogue signals from the sensor.

Advantageously, the wireless device 120 has all necessary inputs to connect to a plurality of sensors allowing the installers to work with a single hardware-software platform. The wireless device 120 has high accuracy 24 bit resolution for accurate data acquisition. With the low power LCD showing a variety of information, the installer is able to easily identify the wireless devices for trouble shooting. Information displayed on the LCD includes ID of wireless device, value being transmitted and battery status.

Each wireless device 120 is required to send three data in each package, namely, current reading (T), first previous reading (T-1 ) and second previous reading (T-2). While it is proposed to include three readings in one package, one skilled in the art will recognise that any other number of readings may be provided in one package and this is left as a design choice to those skilled in the art.

Site server

A site server with installed SCADA and database may be provided at the site. This setup adds cost, but avoids following problems:

1 . Data is backed up on local database in case of 3G signal loss, avoiding data loss

2. The site server ensures that data with same time stamp are matched and that lost data has a pre-agreed format prior to data being pulled from cloud. These actions considerably reduce latency issue in wireless communication.

3. The site server ensures that data from one timestamp is complete (missing information is filled using T-1 or T-2 data, in case of 3 consecutive package loss a predetermined number is filled prior to the data being pulled to the cloud). This drastically reduces the workload on cloud server.

4. Sampling interval is adjustable. Data is measured at second level but stored in the database at minute level to save database size. In case a user wants to increase sampling rate, he can do so either remotely and on-site in order to have more granular data.

What has made this invention unique is the range of expertise required - instrumentation (to ensure that wireless DAQ readings are accurate), network knowledge (for choice of correct wireless setup and protocol) knowledge in database setup (to design an architecture that is scalable, can handle missing information and is fast without large investment in server hardware) and HVAC energy audit to oversee the overall design and function. The wireless device 120 can be installed in the following manner as illustrated in figure 4. An installer will couple the wireless device 120 to one of the sensors accordingly in step 405. For example, if the existing sensor is connected to a BMS, the wireless device 120 allows for splitting of all 4mA to 20mA type input signals to allow for both BMS as well as wireless system access to data. If the existing sensor is not connected to a BMS or the sensor is a new sensor, the wireless device 120 is connected to any of the inputs available.

Once the wireless device 120 is switched on, the installer would configure the wireless device 120 via an installer device that is communicatively connected to the wireless device 120 via wireless connection or wired connection in step 410. The installer device may be a mobile device with an installer application that allows an installer to configure the parameters of the wireless device 120. The installer application should also be able to update firmware, monitor the status of the components in the wireless device 120. The parameters that are configured by the installer include the ID, sampling intervals, transmitting interval and the three data in each package to be transmitted, namely, current reading (T), first previous reading (T-1 ) and second previous reading (T-2).

The connection protocol between the wireless device 120 and the site server 140 is predetermined and no further configuration is required to connect the wireless device 120 to the site server 140. In other words, the wireless device 120 and site server 140 will automatically connect with each other. All the installer has to do is to switch on the site server 140 and verify that the wireless device 120 is connected to the site server 140 by checking the IDs that are connected to the site server 140 in step 415. One skilled in the art will recognise that the installer may configure the wireless device using the site server instead of the installer device without departing from the invention. The installation process ends after step 415.

After the wireless devices 120 are connected to the site server 140, each wireless device 120 samples the reading from the sensor at a pre-set interval. The readings are stored on the memory with a time stamp. Thereafter, the wireless device 120 transmits data packages containing high accuracy (up to 24-bits resolutions) sensor readings, ID and time-stamp to the site server 120. Each data package also includes data measured at current time (T), as well as data measured at two previous time intervals (T-1 and T-2). The data includes four groups of readings, namely power, temperature, pressure and flow. For power group, the readings include voltage, current, power factor and total power. For temperature group, the readings include thermistor reading, atmosphere dry bulb, atmosphere wet bulb and relative humidity. For flow group, the readings include volumetric flow rate, flow velocity, upstream signal strength, downstream signal strength, sound speed, Reynold number and correction factor. Additional information may be added to the flow group and they include pipe size, wall thickness and distance between sensors. One skilled in the art will recognise that the readings are dependent on the type of sensors used for measuring the chiller plants. Hence, other types of readings may be included without departing from the invention. Pressure group includes analogue output in voltage or current (4 to 20mA or 0 to 10V).

Site server 140 has processes that structure the data according to time and sensor. Further, the site server 140 also has processes that check lost data points in the database and use historical data from packages to fill in the blank space. These processes put in a pre-determined value when three consecutive packages are lost. This is useful when installer has left the site. In case of data loss, having a pre-determined number helps in having alarms identifying the error. For example, the main server 1 10 runs a script to alert if the pre-determined value of 99999 shows up. This allows the main server 1 10 to identify all wireless devices 120 with error in one step. Further, having a blank or random number creates database challenges. A blank number may create problems when querying database. As such, having a pre-determined number avoid the above problem. The site server 140 in turn transmits the sensor data in table format via the 3G/4G modem to the main server 1 10.

One skilled in the art will recognise that having a site server 140 reduces the cost of having to furnish each wireless device 120 with 3G/4G communication capability. If future network communication protocol includes Internet of Things (loT) communication at a more cost efficient rate, the wireless device 120 may be configured to transmit the readings directly to the main server 1 10.

Figure 5 illustrates a process 500 performed by the site server 140 for receiving data packages and arranging the data in a data structure in accordance with this invention. Process 500 begins with step 505 by monitoring and receiving the data packages from various wireless devices 120. The data packages received are arranged in a data structure comprising ID, sensors data, time stamp. An example of the data structure for two wireless devices 120 is shown in figure 6. Particular, ten readings are recorded for each of the two wireless devices 120. Subsequent readings are appended to the data structure with the oldest reading removed. One skilled in the art will recognise that the number of readings for each wireless device 120 to be recorded on the data structure is dependent on the number readings to be transmitted to the main server 1 10. Based on current example of 3 recent data, a minimum of 3 readings for each wireless device 120 is required. The sensors data includes four groups of readings, namely power, temperature, pressure and flow. For power group, the readings include voltage (V), current (I), power factor (PF) and total power (TP). For temperature group, the readings include thermistor reading (T), atmosphere dry bulb (ADB), atmosphere wet bulb (AWB) and relative humidity (RH). For flow group, the readings include volumetric flow rate (Volrate), flow velocity (Flowrate), upstream signal strength (USS), downstream signal strength (DSS), sound speed (SS), Reynold number (Rey) and correction factor (CorFac). For pressure group, the readings include analogue output in voltage or current (4 to 20mA or 0 to 10V). Additional information may be added to the flow group and they include pipe size, wall thickness and distance between sensors.

In step 510, process 500 determines whether data packages have been received from required wireless devices based on the IDs on records stored on the memory of the site server. Each wireless device is required to transmit data package at certain time interval. Hence, if the site server 140 fails to receive a data package from any one of the wireless devices (i.e. an error wireless device), the site server 140 has to update the data structure accordingly in step 515. If all data packages are received, process 500 continues with step 525.

In step 515, process 500 uses the previous data package of the error wireless device to fill in the data structure. Process 500 then marks the ID with the missing data in step 520. This is illustrated in figure 6 where ID 002 at time stamp 01072017 1503, 01072017 1504 and 01072017 1505 has been marked with an asterisk and the data at time stamp 01072017 1502 has been replicated in time stamps 01072017 1503, 01072017 1504 and 01072017 1505.

In step 525, process 500 update the data structure by entering the readings received from the wireless devices 120.

After step 525, process 500 repeats from step 505 to obtain the data for the next time interval. The central SCADA can be configured to send warning alarms should it failed to receive data after a pre-fix duration. The Alarms can be send via SMS or email to the designated numbers or email addresses

Figure 7 illustrates a process 700 performed by the site server 140 for transmitting the data packages to the main server 1 10 in accordance with this invention. Process 700 begins with step 705 by checking whether each ID has been marked consecutively for 3 times. For example, ID 002 in the example shown in figure 6 has been marked consecutively with an asterisk for 3 recent readings. This means that the 3 recent readings are based on the readings on 01072017 1502 time stamp for ID 002 and highly likely that an error as occurred for wireless device 120 having ID 002. If an ID has been marked consecutively for 3 recent readings, process 700 proceeds to step 710. If none of the ID has been marked consecutively for 3 recent readings, process 700 proceeds to step 715.

In step 710, process 700 amends the sensor data associated to the ID to predetermined value. Accordingly, the pre-determined value is an unusual value. Preferably, the pre-determined value is 99999.

In step 715, process 700 sends the data packages to the main server 1 10. The data packages include site server ID, wireless device ID, sensor data and time-stamp of the 3 current readings (T, T-1 and T-2). After step 715, process 700 repeats from step 705 for the next time interval.

Processes 500 and 700 may be performed concurrently. Alternatively, processes 500 and 700 may be performed in sequence. For example, immediately after step 525, process 500 proceeds to step 705 instead of repeating from step 505; and immediately after step 715, process 700 repeats from step 505 instead of step 705.

Main server

The main server consolidates the time stamped measurement data from the sensors, onto a single spread sheet and displays the calculated value for user verification. A user can drag and drop files to create formulae to convert instrument signals to measured parameters. Due to variations of the site setup, a predefined formula may not meet the needs of the users. Hence, the main server includes an application that allows user to select the relevant data points and creates the corresponding calculation based on the site conditions. The main server is able to display the result of existing data logging live so that the user can address any potential issues. Essentially, the application executable by the main server includes receiving data structures from the site servers and displaying the result of existing data logging in real time. User is allowed to select relevant data points and creates the corresponding calculation. The application may be provided in the form of a Graphical User Interface (GUI). Each site server 140 has an identification number. Using the ID of the site server, the main server 1 10 is able to arrange the data packages from each site server 140 accordingly onto a single spread sheet. For example, using the data structure shown in figure 6, an additional column may be added to include the ID of the site server 140. Alternatively, the ID for each of the wireless devices 120 is not repeated and the IDs for each site are selected from a specified range for each site.

As mentioned above, a script can be executed at a pre-determined time to identify error wireless devices 120. Essentially, the script would perform a lookup in the single spread sheet for the pre-determined value, 99999, and retrieve the IDs associated to the pre-determined value. For example, assuming the ID of the site server for the data structure as shown in figure 6 belongs to site server ID 101 , the script would return with ID 101 and ID 002 with the earliest and latest time stamp of data with value 99999.

One customer may have more than one site being monitored at the same time. Hence, it is possible for a user to select multiple sites, by selecting the site IDs, to retrieve the relevant data for analysis. There are essentially 2 steps involved in analysing data. First, the relevant data are selected. Based on the type of data selected, the formulas that are relevant to the data would be suggested. The formulas are based on commonly used expression for energy audit of chiller plant. New formulas may be added by the user. After a user select a formula, the result would be populated into the same database as a calculated value.

Figure 8 illustrates an example of a GUI for selecting data and formula. In this example, the data are selected from a logger Tag Browser 810. Upon a selection, the path of the data would be displayed in the Tag Path 820. In response to the data being selected, formulas that are relevant to the data would be suggested in the Formula Input 830. Optionally, if the user wishes to edit the formula, the user can select Edit Formula 840 and a new page would be displayed to the user. Figure 9 illustrates the formula editing page 910. The formula editor only includes three items. The first item 920 is a selection on the parameters to be applicable to the formula. The second item 930 allows a user to edit or create a formula using a drag and drop approach. Particularly, the mathematical expressions are provided at the top region 932 of the editor box 921 . To include a mathematical expression, the user drags a mathematical expression and subsequently drops the selected mathematical expression to the central region 933. The mathematical expressions, +, -, x, ÷ , {, }, shown in figure 9 are for illustrative purposes only and other mathematical expressions such as large operators, matrix and etc may be provided without departing from the invention. The third item 940 shows the result of the formula created. The data are based on that selected prior to entering the formula editor page.

Examples of some analysis undertaken by the main server would be described as follows.

For determining cooling load, heat rejection and heat balance based on header level (Header 1 - Header N), the following expressions are used.

Total Cooling load RT

2. Total PCHWPs kW (PCHWP1 + 9. PCHWPs kW / Ton = Total PCHWPs PCHWP2+...+ PCHWPn) kW/ Total Cooling load RT

3. Total SCHWPs kW (SCHWP1 + 10. SCHWPs kW / Ton = Total SCHWPs SCHWP2+...+ SCHWPn) kW/ Total Cooling load RT

4. Total CDWPs kW (CDWP1 + 1 1 . CDWPs kW / Ton = Total CDWPs kW/ CDWP2+...+ CDWPn) Total Cooling load RT

5. Total CTs kW (CT1 + CT2+...+ CTn) 12. CTs kW / Ton = Total CTs kW/ Total

Cooling load RT

6. Total power input kW = Total Chillers kW 13. System kW/Ton = Total Power input kW + Total PCHWPs kW + Total SCHWPs kW / Total Cooling load RT

+ Total CDWPs kW+ Total CTs kW

7. Total Cooling load RT(CHW Header 1

+CHW Header 2+...+CHW Header n)

For determining the performance at Chiller level, the following expressions are used.

1 . Total Chillers kW (CH1 +CH2+...+CHn) 10. CDWPs kW / Ton = Total CDWPs kW/

Respective Chiller Cooling load RT

2. Total PCHWPs kW (PCHWP1 + 1 1 . CTs kW / Ton = Total CTs kW/ Total PCHWP2+...+ PCHWPn) Cooling load RT

3. Total SCHWPs kW (SCHWP1 + 12. Chillers kW / Ton = Total Chillers kW/ SCHWP2+...+ SCHWPn) Total Cooling load RT

4. Total CDWPs kW (CDWP1 + 13. PCHWPs kW / Ton = Total PCHWPs CDWP2+...+ CDWPn) kW/ Total Cooling load RT

5. Total CTs kW (CT1 + CT2+...+ CTn) 14. SCHWPs kW / Ton = Total SCHWPs kW/ Total Cooling load RT

6. Total power input kW = Total Chillers kW 15. CDWPs kW / Ton = Total CDWPs kW/ + Total PCHWPs kW + Total SCHWPs kW Total Cooling load RT

+ Total CDWPs kW+ Total CTs kW

7. Total Cooling load RT (CH1 16. CTs kW / Ton = Total CTs kW/ Total +CH2+...+CHn) Cooling load RT

8. Chillers kW / Ton = Total Chillers kW/ 17. System kW/Ton = Total Power input kW Total Cooling load RT / Total Cooling load RT

9. PCHWPs kW / Ton = Total PCHWPs

kW/ Respective Chiller Cooling load RT

CHW^T = Chilled Water Delta T - the difference between the Chilled Water Return Temperature and Chilled Water Supply Temperature

CHWRT = Chilled Water Return Temperature - The temperature of the water coming back to chiller from climate controlled space.

CHWST=Chilled Water Supply Temperature - The temperature of water leaving chiller to cool down the climate controlled space

CDW ^A T = Condenser Water Delta T - the difference between the Condenser Water Return Temperature and Condenser Water Supply Temperature

CDWRT = Condenser Water Return Temperature - The temperature of the water coming back to chiller from Cooling Tower

CDWST= Condenser Water supply Temperature - The temperature of the water leaving the chiller to Cooling Tower

Total Cooling Load = The amount of cooling delivered to a climate controlled space, measured in Refrigerant Tons

PCHWP - Primary chilled water pump

SCHWP - secondary chilled water pump

CDWP - condenser water pump

CT - Cooling Tower The above is a description of embodiments of a method and system chiller plant energy audit, implementing wireless devices for data collection and a main server for analysing the data collected. It is foreseeable that those skilled in the art can and will design alternative method and system based on this disclosure that infringe upon this invention as set forth in the following claims.