I found something interested on last weekends Edmonton Eco Solar tour: A wood fired fireplace / boiler.  Made by Wallnofer (from Germany, I believe) and distributed in Canada by Power Strength & Energy Solutions Ltd. (PSES, http://www.pses.ca), the boiler has two combustion chambers.  When a control arm of the side of the boiler is opened, an internal plate is lifted and the upper chamber of the boiler behaves like a normal fireplace.  This setting is used for 8 or 10 minutes after lighting the wood.  Once up to temperature, the side control arm is used to close the upper chimney port which forces the exhaust gases down to the lower combustion chamber where additional air is added causing the gases to burn a second time.  The gases then circulate up a chamber at the back of the boiler, past a water jacket that picks up some of the heat, and them up and out the chimney.  Interestingly, this design does NOT require the use of an electric fan to push to exhaust gases down.  (Obviously the pumps to circulate the water through the water jacket within the boiler require power.)  Note that in the pictures I took with my phone, a cover was removed from the side of the boiler to show the piping connections.  Under normal use, these would not be visible.

The results are impressive: an efficiency rating of 93%, 14.9kw/51,000BTU with 70% of the heat going into the water to be used for space heating or domestic hot water and 30% radiating into the room.  Given how much heat goes into the water, the representative I spoke to said that a storage tank of at least 600L was required and that 1000L of storage was better.

Here's a link to more information on the boiler: http://www.pses.ca/downloads/walltherm.pdf

The Riverdale Net Zero duplex (http://www.riverdalenetzero.ca) has a series of solar thermal collectors that store heat in a 16,000L water tank - practically the size of an in-ground swimming pool - built with concrete walls when the basement was poured.  I've understood from discussions with some of the people that worked on that project that there's a certain amount of heat loss just trying to store the heat from September into January and that the cost, complexity and performance means that design probably won't be used again.  When considering how we could store solar energy collected in the summer to use months later in the winter, it seems to me that nature provides us with the perfect solution: trees.  I find the Walltherm boiler to be a genuinely interesting design that allows us to use wood for more than just space heating.

Ken

Mill Creek NetZero Home, December 15, 2009, 14:00.

As we approach the winter solstice and the three-month anniversary of our moving in, we continue to learn about our new house. These observations are mostly qualitative, because we don’t have the rest of our solar modules up, and we haven’t set up monitoring equipment yet. We are tentatively planning to remove the door of our wood stove on July 1st, 2010  and then monitor the house’s energy use for a year.  read more... »

Mill Creek NetZero Home Living Room - finally some autumn sunshine!

Have you ever noticed that as soon as you move in to a solar house the sun stops shining? It’s been overcast since the beginning of October here in Edmonton – since just after we moved into the Mill Creek NetZero Home – and the fact that Edmonton has as many hours of sunshine as Miami has seemed hard to believe at times. Finally we have the return of sunny days, and the house is great to be in right now.

So what have we learned so far?

• the transition to living on concrete floors has been painless for us. They are much warmer than I thought they would be, and since we were already in the habit of wearing Crocs around the house, I really haven’t noticed the different floor surface. We have been encouraging guests to put on a pair of Crocs from the box in the front entrance.
• the house makes us much more in tune with the solar cycle. The above picture was taken at around 1 o’clock. I enjoyed sitting in the sun for a while before lunch, but now that I’m using the computer the sunny areas of the house aren’t appropriate anymore. Solar houses should have non-sunny areas, and the occupants must be willing to flex with what is going on outside.

the library area on the second floor is bathed in sunlight on a sunny day – luxurious at times, and to be avoided at others  read more... »

The Mill Creek NetZero Home is substantially completed.

The stucco is finished on the outside. We went with a cement-based stucco because of its looks and durability.

Peter Amerongen built a brick wall behind the wood burner. We used the bricks from the foundation of the house that used to be standing on the property. This wall adds more thermal mass (to capture both solar and wood heat) to the house, as well as a bit of history.

 read more... »