Project Proposal - Electrical Consumption Monitoring System
Introduction
With the proliferation of internet connections at almost every home, ubiquitous Wi-Fi, and with smart sensors and devices; it is inevitable that our homes will be integrated with more and more sophisticated devices that will be interconnected to the web. This is commonly referred to as smart home technologies and is an important step toward creating the smart grid of the future. These technologies offer the potential of helping to reduced electrical consumption, reduce greenhouse gas emissions, and provide greater insight into home electrical usage.
The ability to monitor home electrical consumption is a critical piece in realizing the smart home. There are a number of products that attempt to provide insight into home electrical consumption, but provide varying levels of insight into the building’s energy consumption. The current technologies generally operate through one of the following technologies:
Device level monitoring - Device level monitoring systems will generally be integrated into the appliance itself or will be located at the receptacle that powers the device. Belkin SmartPlugs and the Killawatt are both devices that fall into this category.
Advantages – Provides the highest level of granularity into what each device is consuming. This works great for refrigerators. Can be installed by anyone.
Disadvantage – Is difficult to implement. Doesn’t provide a single place to monitor all devices in the home. Products like Killawatt can only monitor one device at a time and are too large to leave plugged in at each devices, are too expensive to be provided for each appliance, and can’t be used on 240V appliances. The Belkin SmartPlugs are more attractive and are Wi-Fi enabled, but have reliability issues and don’t work on 240V appliances like air conditioners, electric heaters, water heaters, electric clothes dryers, ovens, stoves, pool pumps, pumps, and other hardwired devices.
Circuit level monitoring – A circuit level monitoring system consists of multiple current transformers (CTs) located on each circuit.
Advantages – Offers circuit level monitoring. This can be used on 240V appliances that have dedicated circuit breakers; like on ovens, stovetops, dryers, laundry circuits, air conditioners, pumps, etc. This can be installed on almost any home and can monitor all loads.
Disadvantages – Doesn’t provide device level data for circuits with multiple devices on a single circuit. For example, homes often have only 2 or 3 circuits feeding all of the home receptacles and only 2 or 3 circuits feeding all of the lights in the home. You may know that kitchen plugs are being used, but don’t know if that load is the blender, coffee maker, or fridge. These circuits are pretty complicated to install. They must be installed by an electrician and require a lot of CTs. That can be expensive for homes with many CTs. Also, the more accurate CTs are even more expensive. This requires a lot of parts.
Building level monitoring – A building level monitoring system uses a single set of CTs on the main service panel entrance conductors. Almost all whole home monitoring systems use this topology, but some additionally use load disaggregation software to attempt to discern individual loads by viewing the changes in current when the load turns on and off.
Advantages – Only requires a single set of CTs on the main service conductors. Using split core CTs is most common so that the actual service conductors do not need to be rewired. Lowest material costs of the three topologies. Provides comprehensive view of all home loads.
Disadvantages – Does not allow for monitoring of individual loads without load disaggregation software running. Most load disaggregation programs can’t detect small loads, like individual lights. Many utility service panels contain solid bussing between the main breaker and the combined meter main, which can’t accommodate consumption CTs. These combined meter main panels are very common in California and many western states, but are less common in eastern states.
Overview
For our project, we would like to build a whole home monitoring system using the circuit level monitoring system as detailed above. A circuit level monitoring system offers greater flexibility, can be used by any home, and allows for more accurate load disaggregation analysis. Our project will implement the monitoring system with multiple CTs installed on the individual branch circuits. This design offers the option of using a single set of two consumption CTs on the main service panel, but also allows for the addition of multiple CTs on the individual load circuits. We would also like this system monitor to be able to monitor a single solar PV circuit with one production CT.
This type of circuit level monitoring system requires multiple CTs to implement, so requires that our device allow for multiple inputs. Our initial design will limit the total number of CTs to 8 for this project, but we will consider using a microcontroller that allows for more CT inputs.
Project Team
Student Engineer - Kevin Suiker
Student Engineer - Nick Soleil
Technical Advisor - David Kaiser, PE, DIrector of Systems Engineering, Enphase Energy
Faculty Advisor - Saeid Rahimi
Industry Advisor (Customer) - TBD
Schematic
Equipment List and Costs
Hardware Specifications (Digital/Analog Inputs/Outputs)
The Digilent WF32 must be powered by a USB power source or from a power supply.
The CTs will monitor 240V power circuits, and will transform the signal to a 90V, low current signal. The currents are very low but we will need to take special precautions to ensure that hazardous voltages are not applied to the Digilent analog inputs. This will be performed with a voltage divider or LRC circuit. The CTs will be the analog inputs (AI) to the board. The voltage reference will also be an analog input (AI). The output to the LCD will be a digital output (DO). The input from the button will be a digital input (DI). The button will toggle through the LCD Display’s menu headings and will allow the customer to select either consumption or production monitoring as the display option.
Engineering Specifications
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Minimum input of three CTs to datalogger
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Voltage Input to datalogger
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Must be able to accurately report power and energy at +-5% accuracy
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Will report power to local display at least every 15 seconds
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Will report binned energy data to display and web at least every 15 minutes
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LCD Display at In-home monitoring device will display instantaneous power, as well as cumulative energy readings for daily, monthly, and lifetime energy
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CT accuracy will be at least +-2.5%
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The datalogger and displays’ WiFi chips must be able communicate with the home WiFi Network that is no less than 50ft away.
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The data logger and Raspberry Pi will be powered through USB power supplies
Safety Precautions
This project will require working with hazardous voltages. Precautions will be taken to ensure that the circuits are always deenergized before being worked with them. All circuits will be tested with a voltmeter prior to being worked. Personal protective equipment will also be utilized, including gloves and eyeprotection.
Nick Soleil is a licensed, master electrician in California, Texas, and Louisiana and has been an electrician for over 20 years. Nick is extremely competent working with voltages up to 480Y/277V and will ensure that safe working conditions are used. Nick provides electrical best practice training to electricians, electrical inspectors, and solar industry professionals across the US and Canada. Nick is regarded as an electrical code and standard experts working at a leading solar equipment manufacturer, Enphase Energy. Nick Soleil has drafted technical documentation on the installation of CTs for power monitoring systems, with articles on the Enphase website and in the leading solar industry magazine, SolarPro Magazine. Tech briefs below:
http://solarprofessional.com/articles/design-installation/installing-consumption-monitoring-cts
Ethical Standards
As we plan our project, we intend to maintain the highest standards of ethics for our project. We will make sure that the project is created from our own original work. In any instance that we rely on information, software, or other intellectual property we will purchase or provide proper credit to the individuals and companies that have provide the ideas, hardware, or software.
We will ensure that our project will minimize any risk of fire, shock, or hazard to the public or any individuals involved in the project. In the case that risk exists, we will make all efforts to guard against the hazards. We will also take adequate steps to ensure that proper safety standards are in place to ensure personal safety and any personal property.
Survey Results
Other Feedback:
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David Kaiser - Provide ability to log data min/max for the day (demand charge data.)
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Dave Kowalski - Make it a one time fee and a game.
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Nick Morelli - Would rather not add any more devices into hallway, so compatibility/integration with existing devices important.
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Matt Allen - Integrate into home automation package.
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Nick Dadikozian - Integrate with a basic weather station or sensors. Eventually control individual loads.
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Karen Suiker - Must be usable for people who aren't tech savvy
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Silvia Rodriguez - Compare appliance usage with average appliance usage
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Grayson Cooke - Swap the LCD for a hologram
Testing
What we need to test:
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Voltage output of CTs
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Communication between WF32 and PIC
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Communication between PIC and cloud
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Voltage step down to allowable input to microcontroller
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Displaying graphical data on the LCD
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Accurate measurement using ADC on microcontroller
Testing of Raspberry Pi
Here we attempt to send data to our Raspberry Pi over UDP. In order to accomplish this we needed to declare a port to use as well as identify the IP address of the destination. Here is the code written in Python of the source of the information.
On the Raspberry Pi we have similar code but we are receiving the information rather than sending it. We still need to identify port and IP
From here we can append all the data we receive into a file that will be read by another script to create our graphics for the wall display/web based interface.
Connected CTs to analog inputs of WF32 and predicted results and recorded results:
