While I was in the Big Apple teaching a couple of days in the Passivehouse Consultant training, Vineyard Propane came by and took away my propane tank. I had recently sold our last remaining fossil fuel burner, the VT Castings gas heater (the dryer and kitchen range preceded it). I checked when I called them what it would cost for a current delivery - $5.09 per gallon. On a strict BTU basis, that's equal to $0.19/kWh for electricity, about what we pay here on MV. But that's figuring the propane at 100% efficiency. Since we're seeing a pattern when we do energy use assessments here of high summer propane and oil usage with boilers heating DHW, and warm season efficiencies that appear to be as low as 20% or lower, I'm beginning to think that as we design solar hot water systems we should just disconnect the entire DHW system from the boiler and use electricity for the back-up energy.
I'm supposed to get a refund for the propane in the tank, which had about 80 gallons according to the tank gauge. They filled it last fall even though I didn't want it done, and assured me then that I would get refunded for the propane left in the tank. We'll see!
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Posted by: Sea Water Reverse Osmosis | 09/06/2011 at 11:53 AM
Hello Marc,
I've enjoyed and learned from your blog immensely as I try and get our 1950's Albuquerque home with no insulation or southern exposure to net zero energy. Thankfully I have a powerful ally in the sun! I attended a day long presentation by Howell-Mayhew Engineering of Edmonton ( http://www.hme.ca/presentations/NetZero_Energy_Houses_--_What_We've_Learned_--_SAIT_--_2010_Nov_29.pdf ) earlier this year on what they have learned in trying to build NZE homes in Canada. One of their take home points was to keep the systems simple and familiar to the point where they think solar hot water systems might be an unnecessary component with the appropriate efficiency measures and the continuing drop in PV prices. I have not committed to an air heat pump or solar thermal for my domestic hot water heating, but I'm eagerly awaiting to read of your mental wrangling on the matter.
I recently read the article in Solar Today about a near NZE home in Minnesota http://www.solartoday-digital.org/solartoday/20110910/#pg70 clearly they had not attended a recent presentation by Howell-Mayhew Engineering. The mechanical room looks really pretty... pretty darn complicated, but if we hope to see NZE homes flourish, I would think that we would have to make the product easier to replicate and maintain.
Posted by: Seth Downs | 09/13/2011 at 02:25 AM
Seth, I know the energy consultant for the MN house, Mike LeBeau, and he was really trying things on that home he wouldn't normally get to do. I've visited there during construction as well. I agree about simplicity. I'll post soon about my water heating, but suffice it to say that the heat pump water heater will cost less but likely use more back-up energy than solar thermal.
Posted by: Marc Rosenbaum | 09/14/2011 at 01:50 PM