Microcontroller-based Smart House for Improved Energy Efficiency Summary

The Problem Reducing the energy footprint at the individual level can have a major impact on total energy and environmental costs A typical U.S. household could save 25% of its $1,900 yearly energy bill and over 2.5 metric tons of CO2 through improved energy efficiency Automated techniques will play a major role in efforts to increase energy efficiency Small, very-low-cost microcontrollers will be a key enabling technology in this effort Many microcontroller manufacturers are introducing lines of smart microcontrollers for applications ranging from solar panels to intelligent air conditioner control

Lessons Learned: Microcontrollers Microcontrollers provide a low-cost, effective means of controlling processes that might be encountered in a temperature control problem Microcontrollers feature low cost high degree of integration large amount of on-board memory large amount of I/O Microcontrollers are programmed at a relatively low level A typical household may have as many as several dozen microcontrollers controlling microwave ovens, wireless phones, computer printers, etc. A typical midsize car may have 50 or more microcontrollers

Tin (t) = Tout + Tin (0) - Tout) e-t/ Lessons Learned: Heat Loss and Newton’s Law of Cooling Sources of heat loss in house conduction convection radiation Newton’s law of cooling: The temperature inside a body in contact with an outside body at a lower temperature will cool at a rate given by Tin (t) = Tout + Tin (0) - Tout) e-t/

Lessons Learned: Thermoelectric Effects Peltier effect: when a junction is formed between two dissimilar metals, a current passed between them will produce a transfer of heat from one to the other the rate of heat transfer is proportional to the current and the difference between the Peltier coefficients of the two metals the reverse effect (Seebeck effect), in which a voltage is produced if the metals are held at different temperatures, is the basis for the thermocouple, used for measuring temperature Efficiency ~20% of a typical refrigerator Historically used to cool semiconductor components (microprocessors, semiconductor lasers, etc. Growing use in portable coolers/chillers (now available as USB drink coolers) Reversible (use as heaters or coolers)

Energy Tradeoffs Oil Easy to handle, store and transport Easy to extract Nonrenewable resource Burning produces CO2 Numerous environmental safety hazards Coal Abundant resource (although non-renewable) Low cost Mining damages environment Emits pollutants even with anti-pollution measures

Energy Tradeoffs Nuclear Cost effective Lowers reliance on fossil fuels Limited pollution Waste is radioactive (long half life) Mining damages environment Safety is a major issue Natural Gas Minimal pollution Nonrenewable Environmental impact of exploration

Energy Tradeoffs Wind Low environmental impact Safe High cost Requires alternative source as backup Impact on local fauna Tidal Low maintenance cost Predictable Expensive to build Few suitable sites

Energy Tradeoffs Solar Renewable Safe Low environmental impact Small plant footprint High cost Geothermal No pollution Geographically limited

Potential Benefits to Society Substantial cost savings at the individual and societal level Reduced reliance on nonrenewable resources Reduced damage to the environment Reduced impact on global climate Reduced geopolitical tensions