1. Microcontroller-based Smart House for Improved Energy Efficiency Summary

2. The Problem Reducing the energy footprint at the individual level can have a major impact on total energy and environmental costs A typical household could save 2 metric tons of CO2 and $400 (US) per year though 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

3. 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 Lessons Learned: Microcontrollers

4. Lessons Learned: Heat Loss and Newton’s Law of Cooling Sources of heat loss in house transient and steady-state conduction convection radiation Newton’s law of cooling: A simple body in contact with a thermal reservoir will cool or heat exponentially over time T(t) - T out =  T i e -t/ , where T(t) is the temperature at time t, T out = the temperature of the reservoir,  T i = T(0) - T out, and t is a time constant that characterizes the rate of cooling or heating

5. Lessons Learned: Modeling of Steady- State Systems Lumped-element analysis q’’ = (T in - T out ) /R equiv

6. Lessons Learned: Thermoelectric Effects Peltier effect: when a junction is formed between two dissimilar metals, a current passed between them will product 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)

7. Energy Tradeoffs Oil –Easy to handle, store and transport –Easy to extract –Nonrenewable resource –Burning produces CO 2 –Numerous environmental safety hazards Coal –Abundant resource (although non-renewable) –Low cost –Mining damages environment –Emits pollutants even with anti-pollution measures –Burning produces CO 2

8. 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

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

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

11. 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