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

Condensing, tankless hot water heater (left) with drain water heat recovery unit.

The decision is usually thrust upon you. Shower water goes luke warm, or worse, stops altogether one morning. If you're lucky, the basement won't be all wet when you go downstairs to investigate. Yes, the hot water heater has died.

In the hectic days following, you need to make a decision quickly. If long-term energy security and environmental impact are priorities for you, here is a short guide to buying a new hot water heater.

Note: this post was co-written by a good friend of mine who is, in my mind, one of Edmonton's most knowledgeable experts on energy efficient retrofits. He recently installed the water heater shown above in his own home.

Solar Hot Water

The most efficient way to make hot water uses solar collectors, but if you don’t want to (or have the time to) go the solar route, your best option is to use our plentiful and cheap natural gas. Although electricity provides 100% efficient water heating, the electricity itself was generated at 30%-50% efficiency, often using dirty Alberta coal.

Tankless Hot Water Heaters

Using natural gas, the most efficient choice is a condensing, on-demand hot water heater (seen above). This means that there is no tank, and therefore no standby heat losses, and the combustion of the natural gas to heat the water is the most efficient. They have an energy factor (EF) of 0.92-0.96, and they cost around $3000-4000 installed. The combustion gases are near room temperature and are vented directly outside through the basement wall often using PVC pipe.

Predictably, I (Conrad) endorse the above choice. Long term, people! Think long term.

The next most efficient choice is a regular combustion, on-demand hot water heater (no tank, but the combustion is less efficient). They are vented up an existing furnace/hot water chimney or out the side wall using metal pipe. They have an energy factor of 0.82-0.84. (we have no info on costs - anyone?).

Hot Water Tanks

Next up are condensing hot water tanks. Their combustion efficiency is in the 96% range, but because of the standby losses of the tank the energy factor is around 0.83. They cost around $4000 installed.

Finally, there is the regular old hot water tank, which has been around for more than 100 years. Some are insulated better than others and energy factors range from 0.53 to 0.66. (again, no cost info, although this is certainly the cheapest option). 

Tankless = Durable

Besides energy efficiency, a compelling reason to choose a tankless heater is durability. Every tank will eventually corrode and spring a leak. The difference in life spans between tank and tankless heaters is significant. In fact, "Expected life of tankless water heaters is 20 years, compared to 10 to 15 years for tank-type water heaters" (source).

So there you have it. To me, tankless seems like the way to go, but obviously every situation is different. If you do decide on a tankless unit, Edmonton contractors are much more knowledgeable about them than they were just a few years back. Also, make sure to get at least two quotes, as I have heard of $1000 differences for installation and purchase of the exact same unit.

* The Energy Factor of a hot water heater is based on three factors: 1- the efficiency with which the combustion energy of the natural gas is transferred to the water; 2- the heat lost due to storage; 3- cycling losses due to startup and shutdown. 

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