Darrell Russell, Carl Woodard, Heath Hurst
In the United States, residential home energy consumption accounts for roughly 20% of the total energy usage. That comes out to about ten quadrillion British Thermal Units (BTUs) used per year. As the population of the United States continues to rise this will continue to increase and place a greater strain on national and global energy markets while contributing to existing environmental issues. For this reason, it is imperative to find simple, affordable, and intuitive solutions to reduce the energy consumed by the average household.
In the U.S. about 48% of total energy consumed by the residential sector was from heating and cooling according to the U.S. Department of Energy (DOE). This means that any plan or tool conceived to help reduce residential energy usage must consider one of the largest portions of consumption. For this reason, we have chosen to focus on how to reduce overall heating and cooling costs, and by extension reduce the burden on the environment. To help achieve the greatest effect on energy usage the solution needs to introduce the smallest possible burden on the user to ensure continued use, show tangible results after implementation, have minimal impact on the daily routine of the consumer, and allow access by the widest possible population.
Our solution is to create an integrated control system that can replace and/or act along side of the built-in thermostat for homes with central heating and cooling. This system will be fully automated once the initial preferences are entered by the user, allow the user to assume manual control without disabling the system, account for multiple users, utilize Global Positioning Systems (GPS) during automatic control, and provide real-time or historical data for the household's energy usage. All of these capabilities would be ineffective if the system was beyond the economic means of the average household, that being the major issue with many automated heating and cooling systems currently on the market, which is why this solution also focuses on using reliable and affordable components to reduce overall cost without compromising the ability of the system.
The first portion of the system is the remote temperature monitor, constructed from a system microcontroller, electronic thermometer, and radio frequency (RF) transmitter. This allows for high accuracy temperature readings that may be taken from an area that can be more representative of the average temperature in the home than the built-in thermostat. By using high accuracy thermometers and placing the monitor in a more representative location, or in multiple locations if more than one monitor is used, the possibility of over use of the heating or cooling unit occurring because of error in low accuracy thermometers or nonrepresentative temperature samples is reduced. Also, unlike the standard thermostat used today, the monitor does not measure temperature continuously, again reducing the energy usage of the system itself. The simplicity of the monitor also allows for a reduction in cost, since RF transmitters are used rather than direct connection to the internet. Hardwiring the monitors is also unnecessary, lowering the installation difficulty and widening the possible market.
The next critical portion of the system is the GPS integration. A small, non-intrusive application is downloaded onto the user's phone which accesses the GPS location on a regular interval. This information is used to calculate the estimated time it would take for the user to arrive home from their current location. During the initial runtime of the control program, several preferences are decided upon by the user, and may be changed at any time, two of which are the first and second preference distances (Figure 2). The first distance is the area in which one wishes the heating and cooling system to remain active, usually a short distance that would not cause a short-term fluctuation in temperature if the user leaves their house for routine errands. The second distance is recommended by the program based on the size of the home and the efficiency of the heating or cooling unit, which serves as the decision point used by the control program.
Once the remote temperature monitor collects temperature data, it is transmitted to the monitoring unit. This unit collects and converts the data so it can be processed by the system's programming to control the home's heating and cooling. Once the program receives the data the automatic control uses that data to set the thermostat's temperature. However, the control program has several other inputs to consider before deciding on the thermostat's setting. First, the system will remain idle if manual control has been chosen by the user. Second, the system checks the GPS data described above. If the user has been outside of the second distance preference, the program will reset the thermostat to the desired user temperature. If the user has been outside of the first distance preference but inside of the second, the program will incrementally move the thermostat setting closer to the desired user temperature as the user moves closer to the home. Lastly, the program will not allow one's home to drop below, or go above, preset temperatures, included for users who have pets or sensitive possessions that require a more restrictive temperature range. The logic flow diagram (Figure 1) is included to show the process flow.
At any time the user wishes, or on a desired interval, the real-time and historic data for energy usage may be accessed, either as tables or graphs. This however is an abstract body of information. To make the data more tangible to the user, the estimated cost of electricity is used to convert the energy used to money spent, which will be the default setting for display. Also, a separate counter will be shown while accessing the data, showing how much money has been saved by using the automated system instead of constantly heating one's home.
This system is designed to run completely in the background, functioning without further user input past the initial entering of preferences and diagnostic test used to calculate the home's air mass. Since one of the major barriers affecting the usage of automated heating and cooling systems, even with individuals who already own or have installed smart home devices, is the need for continued input from the user, this system aims to eliminate user input. Removing this necessity will increase the likelihood of continued use and savings in energy consumption. Having a fully automated program also removes some of the excess energy use introduced via human error. It is not necessary to remember to reset the house's thermostat before leaving home, or going on vacation, as it would for other automated control systems. Also, there are no set time intervals for the house to be heated or cooled, meaning that if the user deviates from their normal schedule their home will not be heated or cooled unnecessarily, nor will they arrive home to find the temperature far above or below their preference temperature. All these factors culminate in this system being invisible, intuitively controlling the temperature and regulating home energy use without affecting the daily lives of the users. We believe with the combination of minimal user input and low cost, this solution stands out from market available alternatives.