3. Proposed home energy management system

As mentioned earlier, HEMS is a demand response tool that helps utility companies to shift or interrupt the demand to optimize the power consumption and production. HEMS has the ability to make a communication between smart appliances and utility companies to improve the energy consumption of the premise. HEMS is utilizing the smart appliances and smart meter (local controller) to monitor and control the overall power consumption of the residential dwellings. Smart appliances are able to communicate with the smart meter, which is responsible for collecting the required data of the smart appliances for further analysis. Figure 4 shows a simple structure of the smart home. Currently, the majority of the appliances in residential units are traditional and uncontrollable. Therefore, it is desired to convert the traditional electrical appliances to the smart appliances through smart plugs and smart meter. This is more complicated than a simple on and off switch. For instance, a smart air conditioner might extend its cycle time slightly to reduce its consumption on the grid.

In the following sections, smart meter, as well as smart plugs and transmission unit, will be introduced briefly.

Figure 4. Simple structure of smart home (HEMS).

#### 3.1. Smart meter/controller

HEMS consists of smart meter and smart appliances. Smart meters are devices to collect, monitor, and analyze the electricity consumption of the demand. These data are sent to the utility companies in real time to ensure more accurate electricity bills. Such devices provide many services such as electricity quality monitoring (voltage and frequency), demand control, dynamic service tariffs, and so on. In the smart home, electrical appliances are networked together and allow users to access and operate the appliances through a local controller or the Internet. Smart appliances are also able to respond to signals that are sent by utility companies

As mentioned earlier, HEMS is a demand response tool that helps utility companies to shift or interrupt the demand to optimize the power consumption and production. HEMS has the ability to make a communication between smart appliances and utility companies to improve the energy consumption of the premise. HEMS is utilizing the smart appliances and smart meter (local controller) to monitor and control the overall power consumption of the residential dwellings. Smart appliances are able to communicate with the smart meter, which is responsible for collecting the required data of the smart appliances for further analysis. Figure 4 shows a simple structure of the smart home. Currently, the majority of the appliances in residential units are traditional and uncontrollable. Therefore, it is desired to convert the traditional electrical appliances to the smart appliances through smart plugs and smart meter. This is more complicated than a simple on and off switch. For instance, a smart air conditioner might extend its cycle time

In the following sections, smart meter, as well as smart plugs and transmission unit, will be

to optimize the electricity usage during peak hours.

slightly to reduce its consumption on the grid.

Figure 4. Simple structure of smart home (HEMS).

introduced briefly.

70 Smart Microgrids

3. Proposed home energy management system

Smart meters are devices to collect, monitor, and analyze the electricity consumption of the demand. These data are sent to the utility companies in real time to ensure more accurate electricity supplies. Such devices provide many services such as electrical power quality monitoring (voltage and frequency), demand control, dynamic service tariffs, and so on.

Integrating smart meters to premises involves complex communication technologies and may lead to relevant economics and environmental profits for power companies and consumers. As an example in demand side, consumers can be informed remotely on energy costs and related carbon emission data. These data can be recorded and displayed online for the consumers.

A smart meter consists of two main parts such as local controller and transmission unit. At each time interval, smart meter aggregates the data from smart plugs, analyzes the data, and communicates with utility companies for further decisions. The smart meter aims to control the operation of appliances on the grid to decrease the electricity cost taking price signal and occupant's comfort into account. Figure 5 represents the simple structure of the smart meter. Eq. (1) demonstrates the cost of electricity function, while CP is the cost of electricity at the time τ, and TG indicates the consumed power from the grid at the time τ

$$\text{Electricityprice} = \sum\_{\tau=1}^{24} \mathbb{C}\_{\mathbb{P}}(\tau) \* T\_G(\tau) \tag{1}$$

#### 3.2. Smart plugs for conventional electrical appliances

The smart plug consists of three main parts such as a sensing unit, a micro-controller unit (MCU), and a transmission unit as shown in Figure 6. The aim of using the smart plug is to convert the conventional appliances to smart appliances.

A. Sensing unit: This unit can collect the ambient data, convert the analog data to digital, and send them to MCU unit. Current, voltage, temperature, and light lumens are some of the parameters that could be measured through sensors. These data are aggregated through MCU and sent to the local smart meter via wireless communication for further analysis. As an example, ACS 712 current sensors with Hall Effect measurement besides the lm 35 temperature sensors are used here as an example.

Figure 5. Simple structure of a smart meter.

Smart plugs that are proposed and implemented in the HEMS are categorized in two groups. The first category is the normal smart plugs. These plugs can control the electrical appliances by measuring the power consumption of them and send/receive the commands to/from a smart controller. The second category of the smart plugs is the thermal smart plugs. These plugs are connected to the thermal appliances such as air-conditioning system and refrigerator. They are able to measure the inside temperature of the thermal appliances beyond the ability of normal

Transformation of Conventional Houses to Smart Homes by Adopting Demand Response Program in Smart Grid

http://dx.doi.org/10.5772/intechopen.74780

73

There are many methods to reduce the power consumption during peak hours such as direct load control [19], dynamic electricity pricing to incentivize the costumers [20], load management based on game theory [21], and keeping the overall consumption of the building under the certain value [22], which are used as the optimization strategy for electricity price minimizing in this chapter. In order to reduce the electricity price according to Eq. (1), it is required to reduce the electricity consumption (TGð Þτ ) as much as possible. Therefore, the smart meter tries to keep the overall consumption of the building under the predefined value. Residents can turn on any appliance at any time. Each smart plug is interfaced with one appliance; therefore, when one of the residents tries to turn on an electrical appliance, the related smart plug sends a request to the smart meter. Then, the smart meter checks the electricity price, rated power, as well as the priority of the related appliance. If the electricity price is cheaper, related electrical appliance will be operating on the grid. Otherwise, the operation of the electrical appliance with the lower priority value is curtailed for some time, and a new appliance operates on the grid. However, if the priority of the new appliance is lower than the other appliances, the operation of the new appliance is delayed for some time to keep the overall

The aim of using the smart controller is to manage the appliances on the grid to optimize the electricity price. A case study has been observed in a studio-type apartment with ordinary electrical appliances for two persons as shown in Table 1. The priority of the appliances is adjusted by residents based on their comfort level. Here, it is assumed that the utility company sends signal to the smart meter to keep the overall consumption of the building (TGð Þτ ) under the 3000 W at any time interval. Otherwise, the electricity price will be increased as the penalty

The apartment is then equipped with the proposed intelligent plugs to control the electricity consumption during daytime. In order to understand the performance of the intelligent plugs and smart meter, two scenarios are studied and compared, which will be discussed in this Section. It is assumed that electricity price is calculated and sent by the utility company at each time interval. As an example, Table 2 shows the hourly changes of electricity price during 24-h

smart plugs.

for the residents.

3.3. Energy management strategy

consumption of the building under that predefined level.

4. Observation and analysis of the proposed HEMS

Figure 6. Simple structure of an intelligent wireless smart plug.

Figure 7. Layout of the communication among wireless modules.


The smart meter is connected to a coordinator wireless module and smart plugs are connected to the routers/end users. When a new device is connected to the network, it sends a predefended frame, which includes the type of module that could be a router or an end user and address of the module. The smart meter reads the data then about the module and stores the 64-bit address of the module in its EEPROM. Therefore, from then onwards, the smart meter can communicate with the smart plugs through the wireless network of XBee modules. Figure 5 shows the implemented smart meter as well as the smart plug.

Smart plugs that are proposed and implemented in the HEMS are categorized in two groups. The first category is the normal smart plugs. These plugs can control the electrical appliances by measuring the power consumption of them and send/receive the commands to/from a smart controller. The second category of the smart plugs is the thermal smart plugs. These plugs are connected to the thermal appliances such as air-conditioning system and refrigerator. They are able to measure the inside temperature of the thermal appliances beyond the ability of normal smart plugs.

#### 3.3. Energy management strategy

B. MCU unit: This is the central unit or the microcontroller unit, which is interfaced to the sensor units and responsible for analyzing, storing, and sending the collected data to the

C. Transmission unit: This unit is responsible for sending the collected data by MCU as well as to the smart meter [18]. XBee 802.15.4 model XBIB-R-DEV enables us to send data via wireless communication with low power consumption and low cost. The operating frequency of this module is 2.4 GHz. It has serial USART interface connection, which makes it easier to interface with other devices. Figure 7 represents the layout of the communication among smart plugs, whereby C is for coordinator, R represents router, and E repre-

The smart meter is connected to a coordinator wireless module and smart plugs are connected to the routers/end users. When a new device is connected to the network, it sends a predefended frame, which includes the type of module that could be a router or an end user and address of the module. The smart meter reads the data then about the module and stores the 64-bit address of the module in its EEPROM. Therefore, from then onwards, the smart meter can communicate with the smart plugs through the wireless network of XBee modules. Figure 5 shows the

local controller/smart meter through the transmission unit.

Figure 6. Simple structure of an intelligent wireless smart plug.

72 Smart Microgrids

Figure 7. Layout of the communication among wireless modules.

sents end user.

implemented smart meter as well as the smart plug.

There are many methods to reduce the power consumption during peak hours such as direct load control [19], dynamic electricity pricing to incentivize the costumers [20], load management based on game theory [21], and keeping the overall consumption of the building under the certain value [22], which are used as the optimization strategy for electricity price minimizing in this chapter. In order to reduce the electricity price according to Eq. (1), it is required to reduce the electricity consumption (TGð Þτ ) as much as possible. Therefore, the smart meter tries to keep the overall consumption of the building under the predefined value. Residents can turn on any appliance at any time. Each smart plug is interfaced with one appliance; therefore, when one of the residents tries to turn on an electrical appliance, the related smart plug sends a request to the smart meter. Then, the smart meter checks the electricity price, rated power, as well as the priority of the related appliance. If the electricity price is cheaper, related electrical appliance will be operating on the grid. Otherwise, the operation of the electrical appliance with the lower priority value is curtailed for some time, and a new appliance operates on the grid. However, if the priority of the new appliance is lower than the other appliances, the operation of the new appliance is delayed for some time to keep the overall consumption of the building under that predefined level.
