5. Electrical, HVAC, appliances and solar
Electrical -
All the lights in the house are LED, with a larger cost up front but high energy efficiency and long lifetime. They are all installed in regular medium-based fixtures to reduce the cost. Bulbs were bought in bulk from Home Depot to reduce the purchase price.
HVAC -
A Geothermal unit was installed as it is 2 times as efficient as a regular heat pump and when run off solar is carbon free. A regular heat pump for 100 watts of electricity produces 300 watts of heat. For a Geothermal unit 100 watts of electricity produces 600 watts of heat. Also a regular heat pump only last for about 15 years and a geothermal unit as it is inside your house last for 25 years and the ground loop for 50 years average. The other great advantage is that it is almost silent and you have no noise outside your house. No blowing fan or compressor.
The HVAC unit is from Water Furnace - series 7 geothermal unit. It reduces power usage by being variable flow/speed in the ground loop, compressor and blower. (Note that the house could have been close to net zero with a standard heat pump because of the insulation and low air infiltration.) This unit allows for monitoring of the power usage and for creating different zoning areas of the home for temperature control, thus allowing for additional heating and cooling in just the areas being occupied. This could have also been accomplished with a mini-split system, but that was not felt to be as energy efficient. To reduce cost in the installation of the unit, all the ground loops were installed in existing trenches that were being dug for the house. The water line trench was dug to 6 feet and the Geothermal line installed and then the trench was partially filled and the water line installed. Alternatively, the geothermal lines could have been installed around the foundation and basement walls to save cost (in comparison to digging geothermal wells). This can all be found in research done at ORNL (Oakridge National Laboratories) website. http://info.ornl.gov/sites/publications/Files/Pub10081.pdf, and www.ornl.gov/File%2520Library/Main%2520Nav/SCIENCE%2520AND%2520DISCOVERY/Clean%2520Energy/articles/Z... - 43k - Text Version
All the ducts are insulated, sealed, and within the conditioned space, therefore decreasing thermal energy losses. Because the house is so airtight it has an ERV – (energy recovery ventilation system). This system will operate for 100% of the day will draw fresh air into the house in exchange for conditioned air. The ERV will exchange energy and reduce humidity by either cooling or warming the outside air that is being drawn into the house. This is done by having the air basically go thru a radiator, with conditioned air being in the radiator and outside air being drawn across this to reclaim the heat or cooling energy there. This system operates at about 60% efficiency. This will supply the house with fresh air that is almost at room temperature. It therefore uses less energy to get fresh air into the house and up to room temperature than drawing the air directly into the HVAC unit to increase its temperature. This energy exchange is done mostly as a passive process except for the blower motor contained in the unit. (In the photo below the water furnace unit is shown with the ERV in the foreground. Four pipes are connected to it, 2 to the outside wall and 2 to the house.)
All fan motors – Ceiling fans and bathroom fans have DC, motors thus reducing their energy use. With the use of ceiling fans, the house can be at a warmer temperature and still feel comfortable by using less kilowatts of power. The Emerson DC ceiling fans draw about 30 watts to provide the same air movement that a normal AC ceiling fan would use 120 to 150 watts to produce (4 to 5 times more efficient). The Panasonic bathroom fans use only 3 to 4 watts (10 to 20 times more efficient than a normal bathroom fan) and are on a timer to control their run time. They are also at a low exhaust volume. This is all to reduce energy loss.
Supplemental fireplace heat is available if there is a power outage. It has a closed loop burn chamber, using outside air with a heat exchanger for the air in the house, thus keeping out smoke and carbon monoxide. For installations affiliated with the Tennessee Valley Authority (TVA), as this one is, the use of solar power in a power outage is prohibited. Safe ways of detaching a home installation from the grid need to be explored in order to make it possible for homeowners to use the energy they generate when the grid is not available.
Appliances -
Appliances were selected from the list of Energy Star Qualified products for their low energy usage; other considerations were their ease of use and low maintenance. http://www.energystar.gov/index.cfm?fuseaction=find_a_product.&s=mega
A conventional electric cook top uses about 40% of its energy to cook the food and the rest is wasted. So 60% of the electricity that you are paying for is lost. With a gas stove only about 60% of the energy consumed is used to heat the food and the remainder is lost into the house. This also generates pollutants from the burning of the gas. Of course this could be exhausted, but this would cause more energy loss. The most efficient cooking is done with induction technology. With this method approximately 80% of the energy is used to cook the food. This is not new technology. It is somewhat standard in Europe and its cost is similar to our current stove costs. The range hood also uses low volume ventilation to decrease energy loss. We use a Air King unit, one of the more efficient ones made.
Solar -
Solar power for the house was chosen so that products were mostly produced in the USA. To do this we used Suniva panels and Enphase microinverters. Both have long manufacturer warranties and the microinverters ensure that we will have maximum electric generation when there is partial shading or a problem with a panel. Basically the microinverters are in parallel so if an inverter or panel goes out you can still get power from all the other panels. Also with their Enlighten system I can get real time reports on my energy production. Go to their website to learn how microinverters are so much more efficient that a string inverter. The house was oriented to the South with the appropriate angle to the roof to maximize solar gain on the solar panels.
