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Going Green: The InterHome Home Energy-Saving Project (3/8/2009)

By Johann Siau, Ellis Percival and Carol Chen, University of Hertfordshire

According to the official website of the UK government, 'Energy used in homes is responsible for over a quarter of all UK emissions of carbon dioxide - the main greenhouse gas causing climate change. Making your home as energy efficient as possible will reduce carbon emissions and could save you over GBP300 a year on your fuel bills.'

Modern life embraces so many electrical devices that electrical energy becomes essential for everyday activities. But are we consuming energy effectively? The need to reduce the amount of fossil fuels we burn becomes more obvious every day; with the effects it has on the weather, people's health and even the effect it has on our pockets. More sustainable and less destructive ways of providing power are on their way, but in the meantime we're sending even more harmful waste into the atmosphere. We need to find a way to reduce the consumption of our biggest drain on resources: our homes.

A huge amount of energy can be saved by turning off what we are not using, using our appliances more efficiently, and by using our commonsense. Unfortunately, for a variety of reasons, this often does not happen in practise. We need a helping hand. Computers do not suffer from being forgetful or being in a hurry, and are therefore perfectly suited to carrying out schedules and automating the mundane tasks in our lives. By creating a system to control and monitor our lights, heating, energy consumption and security, we can avoid leaving any lights on when there is nobody in the room, heating the house when there is nobody at home, and accidentally leaving our doors unlocked.


InterHome, an ongoing intelligent home project, is being developed by a group of researchers at the University of Hertfordshire. It is a model for a home that incorporates modular custom design units and draws on standard home automation systems which have been adapted so that the house Ďlearnsí and Ďadaptsí to its usersí lifestyles. It can learn from its residents and take decisive action, sending a text for example, if it is being burgled or if the door has been left unlocked. The system incorporates an intuitive touchscreen user control panel that also allows the house to be monitored and controlled using web browsers, windows mobile and any SMS-capable mobile phone.

InterHome's solution to problems of energy efficiency uses the Microsoft .NET Framework, the Microsoft .NET Compact Framework (CF) and the Microsoft .NET Micro Framework (MF), leveraging any existing hardware/software which the users may already own, whilst incorporating InterHome's custom hardware and software.

The prototype of an Interhome home, which has been developed in a dollís house, integrates embedded devices with the industry standard X10, so that it provides convenience and security to the home owner and also enables them to reduce energy so that they make savings of up to GBP300 a year and contribute to reducing greenhouse and carbon emissions.

The custom hardware divides each home into manageable sections, enabling a scalable solution whilst simplifying software development. Our custom hardware is capable of controlling relays to turn on and off devices such as computers, televisions, radios, lights, heaters and fans, rather than leaving them on standby. This same board provides input readings to InterHome, enabling devices such as temperature sensors, light sensors, movement detectors and audio sensors to be incorporated. This means that a huge range of devices can be connected up in each room, and control routines can be written easily in managed code, whatever the device is.

Typical InterHome hardware architecture.

Controlling these boards is the very low-powered microcontroller that runs the .NET Micro Framework. This MF device also connects to an X10 controller to control existing home automation systems. X10 is an industrial standard for communication between electronic devices that is used primarily for home automation. The X10 controller communicates with X10 devices via the existing mains power cables.

The MF device is connected to the Internet to update InterHome's Web Service. The Web Service is updated periodically with the status of each sensor and the outputs are set according to the data received. This Web Service is also checked by the eBox (a Linux-based open source distribution and development platform), and the touchscreen to which it is connected will be updated with the information received. If the user wishes to change something, i.e. turn an appliance on or off, dim the lights or change the temperature, the eBox will update the Web Service accordingly and send the command to the MF device which will update the relevant devices in the house.

Mobile control

Another way of controlling the automation system is by using a mobile phone or other mobile device connected either to the Web Service via the Internet, or via Bluetooth to the microcontroller. The mobile device runs the .NET Compact Framework and works in much the same way as the eBox, with the added advantage of mobility. SMS notifications are available to the user by using the GSM module in conjunction with the MF device. This allows updates to be sent to the user periodically, or warning messages to be sent when certain triggers are set off.

Users may also wish to send a simple SMS to their home to query its current status. In addition, users are able to control their house by sending SMS commands. The automation system is controllable from anywhere in the world via a web interface. This is secured so that only the correct people may access its potentially sensitive information. The advantage of this system is that users can check the status of their home from any computer anywhere in the world and, for example, turn the lights on and off to simulate a presence in the house whilst on holiday, or better still, let InterHome manage the house for them.


InterHome offers the functionality of saving energy and much more. It is an intelligent home system which learns our routines, knows our location and can adapt to our lifestyles. The system will save energy whilst being as transparent as possible to the end user. Features such as GPS location tracking, motion detection, light sensing and behavioural logging give the system a huge amount of data to learn from and adapt.

The electricity usage monitoring is a hugely important feature, as it allows the inhabitants of the home to see exactly how much energy they are using and compare it to other similar homes. For example, this feature can alert users to the fact that they are using a lot more energy than their neighbour, spurring them into taking remedial action. The effectiveness of the system can also be measured using this functionality.

X10 interaction ensures that InterHome can be integrated into existing systems, and also be retrofitted with the minimum of wiring and expense. For new builds, the wired version of InterHome can be used so that each wall socket can be directly connected to the system, eliminating the need for X10 modules. The ability to use Windows Mobile devices to control the system makes the system more convenient, and also provides the opportunity to tap into the GPS functionality of modern mobile phones in order to be able to tailor the house state in accordance to the users' location.

For non-Windows-based phones, SMS text messaging can be used to update the house, or retrieve its status. Thanks to these features, InterHome will do an excellent job at reliably reducing the amount of energy wasted in our homes. This will undoubtedly have a great impact on reducing greenhouse gas emissions, since our homes are such big factors in the amount of energy wasted.

Johann Siau, Ellis Percival and Carol Chen form the InterHome research group at the School of Electronic, Communication and Electrical Engineering, University of Hertfordshire. The University of Hertfordshire is one of the region's largest employers with over 2700 staff and a turnover of more than GBP205 million. With a student community of over 23,000, including more than 2000 international students from over eighty five different countries, the University has a global network of over 160,000 alumni.


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