In the previous two blogs of this series of three (Part 1, Part 2), I discussed the concept of passive solar architectural design, the potential for system autonomy, solar electric on-grid power and the way a heat pump works. This blog is about putting these together with a way of controlling their interface to achieve stand-alone heating and cooling systems that are powered by the sun and take energy from the earth or atmosphere, and that working with the patterns of nature approximate perpetual motion. As long as the earth circles the sun this type of system will continuously function within the lifetime of the equipment.
A system that is properly designed will heat and cool a house year around without requiring additional auxiliary heating or cooling. When a ground source heat pump system is coupled with a solar electric photovoltaic system for powering the unit, we create a closed loop operating system that does not need imported, or off site energy to operate. A heat pump can deliver hot or cold water or air to the house by using heat exchange devices; which means it can be used to: provide hot water for radiantly heated floors and domestic hot water, (one of my clients is using a system like this to melt ice off the driveway in winter), cool water or air, or heat a spa or swimming pool. It is best to use a system year around for both heating and cooling to optimize return on the investment. Heat pumps are not the cheapest first cost type of space conditioning systems, but in the long run they are the most cost effective when compared to standard fossil fuel heating or cooling methods.
When a combined photovoltaic powered ground source heat pump installation is activated by a control system that senses the passive solar heat gain to the house, total automated comfort can be achieved. Sophisticated controls can use mean-radiant temperature sensors, differential temperature reading thermostats, and even microprocessors to manage the delivery of heat and cold to different parts of the house. For example in a space heated by a radiant floor if the sun starts shining into the room adding passive solar gain, a mean radiant temperature sensing thermostat will quickly shut off the hydronic delivery to the space to keep it from overheating, automated ceiling or duct fans can be used to further move heated air to remote parts of the house effectively balancing the heat comfort of the entire house.
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Smart microprocessors with memory capability can anticipate outside sun/temperature affecting the weather skin of the house to allow delivery routines to respond to near future space conditioning needs. These same devices can be set to vary the temperature of various spaces, or zone control, giving custom heating/cooling options to provide better comfort and energy management. For instance the temperature in a bathroom can be reduced at night to save energy when unoccupied, but be programmed to either sense occupancy, or go on at predetermined times such as warming the space in the morning before you rise, or even heating the shower floor and towel bar before you take your normal shower. The limitations are our imaginations.
These developments in technology are available now and will become commonly used in the future as our conventional energy resources become more expensive. Tapping directly into the sun and the earth’s crust, to power and regulate the comfort of buildings, is making good advantage of Mother Earth’s potential. Designing towards a perpetual motion machine is what I consider to be the natural pathway to true sustainability.
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