As we had projected, our solar array has generated a significant electricity surplus:
We have generated approximately 20,000 kWh of solar power. Although our utilization is increasing as expected, we have accumulated a net of -8,000 kWh. This has resulted in a significant credit on our statements from West Penn ($355.34), our electrical utility; we haven't paid an electricity bill since our net meter was installed. They deduct a "customer distribution charge" of $5.00 each month. As described on our monthly bills, this is a fixed charge for meter reading, billing, surface line maintenance and equipment.
Our biggest energy concern last fall was whether our high tech balanced ventilation system by Zehnder of the Netherlands (http://www.zehnder.nl/producten-en-systemen/comfortabele-ventilatie) would keep our house cool in the summer.
In lieu of air conditioning, our home has a Zehnder ComfoAir heat recovery unit and a Zehnder ComfoCool unit to regulate the temperature and humidity of the fresh air. The ventilation system consists of the ComfoAir unit, a duct system for supply of outdoor air and exhaust of indoor air, supply and exhaust valves. These were seamlessly incorporated into our build out.
Ceiling exhaust (left) and floor intake (right)
Because of our impressive home insulation, our breathing generates significant carbon dioxide in our home When set on automatic, a CO2 sensor which is a component of the system will control the ventilation setting; it looks like this:
We can also track CO2 and humidity via our Domovea server. The data looks like this:
There are two key differences between air conditioning and our ventilation system. Air conditioners recirculate air but do not provide ventilation. Our ComfoCool system supplies outdoor air. Air conditioners only work in the rooms in which they are located. The ComfoCool system cools air throughout out home. The system is controlled using a operating panel: The panel looks like this:
We typically set it like this when we are at the house:
And like this when we are away:
The real question is whether this is working. And the answer is yes. We weren't concerned about our geothermal heat pump keeping the house warm in the winter but we were dubious that the house would be comfortable in the summer months without air conditioning. And we were wrong. Here is a summary of interior and exterior temperature for May 2014 to May 2015:
This graph is busy but important showing the temperature on the y-axis and both our rooftop temperature (via our weather station which is described in a previous post) and the temperature in the center of our home (the dining room). There is a gap due to some inexplicably lost data, but in spite of some significant fluctuations in outdoor temperature our home has remained very close to 23 degrees Centigrade = 73.4 degrees Fahrenheit and very comfortable. The system is almost silent (our plant room is highly sound-proof) and even though the house has multiple glass panels, the circulation of air is imperceptible. This really is a very smart house.
Our only other major addition since my last post has been the purchase of a tractor to begin preparing our old hay field for planting of either a wildflower mix or switch grass.
We really love the house. But even more than the house we love the view. Two weekends ago, we got an terrific look (not well captured on film because of our shock) of an adult male harrier:
Who knows what next weekend will bring?
