Energy demand is increasing day by day, Presently, electrical energy consumption from users in an area is monitored and calculated by frequent field visits done by technicians from the electricity department for the calculation of energy fare. This is a time-consuming task as there will be thousands of houses in an area and numerous apartments in the same flats. When it comes to a city or town, this is a very hectic process. There is no provision to check or analyze the individual energy consumption of houses in a period of time nor to create a report of energy flow in a certain area. This is just the case throughout many places in the world.
There are no existing solutions implemented to tackle the above problem. Hence, we are developing a smart energy monitoring system that will ease the inspection, monitoring, analysis, and calculation of energy fare. The STEMS system will additionally allow generating user specific or area specific charts and reports to analyze the energy consumption and energy flow.
Step 1: Workflow
The STEMS module mainly comprises the Seeedstudio Wio LTE module which is given a unique user code to identify the particular housing unit where the energy consumption has to be measured. The power consumption will be monitored by Wio LTE module with the help of a current sensor interfaced using the analog grove connection.
The energy consumption data, the unique user code and the location (Wio inbuilt GPS/GNSS) of the module will be uploaded to STEMS cloud (hosted at AWS) at real-time using the Wio LTE connectivity and Soracom Global SIM. The data from the cloud can be accessed and analyzed to calculate individual energy consumption, generate individual and collective energy charts, generate energy reports and for detailed energy inspection. Relays are also interfaced to cut off the connected appliances in case the energy consumption goes beyond the threshold limits. An LCD display module can be integrated into the local STEMS module to display real-time energy measurement values. The system will work independently if a portable power source such as dry cell battery or Li-Po battery is attached. Setup The hardware setup is depicted below:
STEMS Hardware setup
The GPS signal was found to be weaker inside the building. But once the modules are shifted outside, we will start getting good reception. The GPS coordinates received from the module was compared to the actual GPS coordinates in Google Maps. A fair amount of accuracy was obtained.
Power from the AC mains is drawn and passed through the current sensor which is integrated into the household circuit. The AC current passing through the load is sensed by the grove current sensor module and the output data from the sensor is fed to the analog pin of the WIO LTE module. Once the analog input is received by the WIO module, the measurement of power/energy is inside the program. The calculated power and energy is then displayed on the LCD display module.
In AC circuit analysis, both voltage and current vary sinusoidally with time.
Real Power (P): This is the power used by the device to produce useful work. It is expressed in kW.
Real Power = Voltage (V) x Current (I) x cosΦ
Reactive Power (Q) : This is often called imaginary power which is a measure of power oscillates between source and load, that does no useful work.It is expressed in kVAr
Reactive Power = Voltage (V) x Current (I) x sinΦ
Apparent Power (S) : It is defined as the product of the Root-Mean-Square (RMS) Voltage and the RMS Current. This can also be defined as the resultant of real and reactive power. It is expressed in kVA
Apparent Power = Voltage (V) x Current (I)
The relation between Real, Reactive and Apparent power:
Real Power = Apparent Power x cosΦ
Reactive Power = Apparent Power x sinΦ
We are concerned only on the Real power for the analysis.
Power Factor (pf) : The ratio of the real power to the apparent power in a circuit is called the power factor.
Power Factor = Real Power/Apparent Power
Thus, we can measure all form of power as well as power factor by measuring the voltage and current in the circuit. Following section discusses the steps taken to obtain the measurements that are required to calculate the energy consumption.
The output from the Current Sensor is an AC voltage wave. The following calculation are done:
- Measuring the peak to peak voltage ( Vpp )
- Divide the peak to peak voltage(Vpp) by two to get peak voltage (Vp)
- Multiply Vp by 0.707 to get the rms voltage (Vrms)
- Multiply the Sensitivity of the current sensor to get the rms current.
- Vp = Vpp/2
- Vrms = Vp x 0.707
- Irms = Vrms x Sensitivity
- The sensitivity for current module is 200 mV/A.
- Real Power (W) = Vrms x Irms x pf
- Vrms = 230V (known )
- pf = 0.85 (known)
- Irms = Obtained using the above calculation
For calculating the energy cost, the power in watts is converted into energy: Wh = W * (time / 3600000.0)Watt hour a measure of electrical energy equivalent to a power consumption of one watt for one hour. For kWh: kWh = Wh / 1000The Total Energy cost is: Cost = Cost per kWh * kWh.The information is then displayed onto the LCD display and concurrently wrote to the SD Card.
Step 2: Testing
As the testing was done near to the balcony, a fair amount of GNSS reception was obtained.
Step 3: Future Plans
An app will be created to access the STEMS cloud data to monitor user energy consumption in real-time and to view or generate energy analysis reports. An upgrade to the STEMS module can be easily done due to the Arduino IDE compatibility. Once successfully completed, this module can be produced in the market and can be used by energy service providers throughout the world.