Zero energy homes (ZEH), often called net-zero energy, or zero-use energy homes, have been receiving increased attention from the building industry in Europe and, more recently, in the United States. Techniques employed in ZEH homes include passive solar heating and water heaters, thick layers of insulation in exterior walls and attics, and extremely well-sealed and thermally efficient doors and windows.
Most ZEH homes utilize energy efficiency technologies and alternative energy sources that are focused on addressing primarily heating, cooling, and water-heating needs within the home. With very good insulation techniques, the energy needed to heat and cool modern homes can be greatly reduced: in demonstration communities throughout the US, a reduction of over 50% has been achieved in heating, cooling, and water heating energy use.
As ZEH building techniques have reduced the energy needs for heating, cooling, and water heating in the home, other building trends have incorporated systems that required additional electricity. Modern new construction often includes home automation and controls systems, structured wiring, distributed entertainment and security systems, and enhanced lighting.
Just how much power do these other electrical devices consume? According to a report by Lawrence Berkeley National Laboratory in the United States, appliances, lighting, and miscellaneous electronics can consume between 46% to 88% of the electricity used in a home. The study looked at homes located across the United States, in all climate regions – some results are illustrated in Figure 1.
Figure 1 Percent Energy Use in Homes Source: LBNL Report 62440
As ZEH building techniques continue to make heating and cooling more energy efficient, the contribution of additional electronic devices can be expected to increase as a percentage of home energy use.
To be truly zero energy use, a home would need to generate as much energy as it consumes from the grid over a one year period. According to the U.S. Department of Energy’s Building America study, as of 2005, somewhere between $20,000 and $30,000 of photovoltaics would need to be installed to meet the growing power needs of home electronics. This number was expected to double over a ten year period at the time of the study.
While smart electronic devices will present problems in maintaining ZEH goals, the other side of the story is that these very devices can reduce energy use as well. Systems that have automatic shut-off switching for lighting and electronic devices, smart climate control for heating and cooling, and delayed turn-on switching for appliances like dishwashers, can all reduce overall energy use despite the fact that these systems requires some constant level of power to operate.
Achieving ZEH status in residential construction will most likely involve an optimization process for smart devices and alternative energy sources. Smart systems can be used to minimize and conserve energy use, while technological breakthroughs in solar and battery power will enable the affordable implementation of alternative power sources for home electronics.
(Source : leonardo -energy )
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