Energy Efficiencies in a Home Energy Management System (HEMS)

I have always been intrigued by smart home concepts and technologies that seemingly make life easier for consumers. My view is that a smart home would actually be smart in its efforts to curtail energy waste and reduce cost to the homeowner.

The industry as a whole looks at load shedding, dynamic pricing, Time of Use (TOU) and so on as issues of importance in conserving electricity use within buildings. What the industry doesn’t do is consider alternative solutions that can compliment or even supplant these methods of reducing energy usage.

Instead of TOU, Home Energy Management Systems can buy energy when the pricing is low and store it for use when the prices are high. TOU and load scheduling becomes less of a player when pricing becomes an important part of the overall strategy for energy management. There are other things that also impact energy use that a smart home can manipulate and control to effect energy reduction. For smart homes to be truly effective in energy conservation, they must, in the words of Mark Feasel (Dir of Sales and Marketing at Schneider Electric’s Energy Solutions Business) be “situationally aware” of all factors impacting energy consumption – pricing, TOU, lifestyle habits and so on.

Al Presher in his article, “Metering and Monitoring Trends” (Motion Control/Automation, Design News, April 2010) points out that energy within a home or building can be stored and used to offset electricity use. Smart systems can set up a “profile to store energy in the form of pre-cooling or pre-heating and coast through those peak times.” Buy electricity when its price is low to use when it’s high.

I once visited a “green” newly constructed home and was amazed at the level of technology employed. What I did notice while there was the lack of a cohesive approach to total home involvement in energy management. The house wasn’t “situationally aware.” Let me elaborate. The sun rises on one side of the house and sets on the other. The home is technically being heated on one side first and, as the sun moves across the sky, incrementally heated until the sun sets. In the summer time, this would create more energy need on the side where the sun is most prevalent. A normal house doesn’t cool air using this approach though. Instead, the wall thermostat, which is supposedly placed strategically in the central part of the house (assuming one unit only) acts as the temperature regulator that determines when and how long the air conditioner runs. So portions of the house are hotter then others and the cooling uneven throughout. The air conditioner runs longer to compensate for the “distant ends” that are being stressed by heat from the sun.

What if the house had inexpensive automated dampers that control air flow throughout? What if the Home Energy Management System managed these dampers by closing and opening them based on a low cost remote temperature sensor within each room? Using the above strategy, the HEMS would focus cool air flow on those areas being affected by the sun while diminishing those areas that are not being impacted.

If those rooms are not being used, then the HEMS would regulate air to the areas occupied and close the dampers where needed. In a properly insulated house, the empty rooms would act as air buffers to the rest of the house being cooled.

What amazed me about the green home was its lack of a means to measure efficiencies. While it did employ modern technologies in house construction, it had no means of gauging how all that applied to whole house energy efficiency nor did it have a way to sustain that efficiency rating yearly without an outside agency doing the evaluation. A HEMS integrated network would have looked at the energies being used and compare periodically for degradation of efficiencies, whether it be found in increased heating or cooling requirements, whether it be appliances requiring more electricity due to poor air flow (such as the refrigerator and the air conditioner/heater), or whether it be just an increase in consumption due to appliance breakdown and lack of maintenance.

As climate change impacts weather, the need to ascertain energy efficiencies within homes increases and more will be required from HEMS.