On eliminating peak load auxiliary energy consumption in passive solar residences during winter

Abstract

This paper uses simulation analysis with Albuquerque, NM and Madison, WI weather data to address the following four questions: o 1. Assuming a properly designed and controlled passive house, how does total electrical auxiliary energy consumption depend on the choice of peak load blackout periods? 2. What comfort penalties arise from properly coping with a variety of peak load blackout periods? 3. Where should off-peak energy be introduced into the thermal masses of the house? 4. What are the effects of imprecise information on short term future weather? Using a combination of linear programming and gradient techniques, the following conclusions are obtained: During the worst days of the heating season, passive solar houses built above ground use a substantial amount of peak backup energy even if they are well designed. Even relatively crude off-peak controls provide reasonable comfort provided the energy is introduced in thermal masses well coupled to the room [e.g. 0.05 m (2 inches) beneath the inside face of the Trombe wall or 0.05 m (2 inches) below the top of the slab floor]. Introducing off-peak energy in thermal masses poorly coupled to the room (e.g. deep in the floor slab) makes proper control very difficult without very accurate weather prediction. Reducing backup use to zero from 7 am to 10 pm requires a doubling of daily backup use in Albuquerque and Madison. Excluding backup for shorter periods (e.g. 5 pm to 9 pm) requires an increase of about 25% in daily backup consumption. Even if off-peak energy is stored at points reasonably well coupled to the room, significant backup and comfort penalties are incurred with erroneous weather forecasts. Even in two adjacent days in Madison, reversing the weather patterns while maintaining the same off peak control strategies resulted in either wasting half the backup energy or severely under heating the house. The effects of faulty weather forecasts are more severe when poorly coupled storage sites are used.