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2006 December » Our Sustainable Home
Archive for: December, 2006

Wildly efficient Stirling engines

December 31st, 2006

I first became aware of the Stirling engine when reading about inventor Dean Kamen many years ago. He didn’t talk about the Stirling Engine in detail, but what I did find out was that it is an incredibly efficient non-combustion engine, that is powered by differences in temperature. (e.g. you can buy small a Stirling engine that is powered by the difference in the heat from your hand and the ambient temperature.

Sounds great right? In our home, maybe we could generate heat on the roof, and take cool from the ground and generate some free power, right? As is often the case, the first tip-off that there might be a problem with this logic is that nobody has done so already.

I did a little more research and it seems that unless you can get a heat differential of about 300 degrees Celsius, a Stirling engine practical for powering a typical home would itself need to be about the size of a typical home. Stirling engine size is proportional to the amount of power one needs, and inversely proportional to the heat differential between the cold and hot sides of the engine.

Another problem would seem to be the noise. The seemingly inappropriately named WhisperGen of New Zealand specializes in producing Stirling engine water-heater/power-generator combination units. According to their literature, these devices produce 63dBA of noise (and only a fraction of a house’s power requirements). While that’s quite quiet for a generator, it’s still the volume of a loud conversation, or air conditioner. That’s fine if one is encountering it from time to time, but to have it going in one’s home all the time would likely get a little grating.

It might very well be possible to overcome the heat differential limitation, but given the noise they generate it seems unlikely that Stirling Engines can be a part of any urban sustainable build.

Posted by Colin
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Follow-up: Generating your own solar power

December 30th, 2006

Alex had mentioned that as a general guideline, energy prices are assumed to rise on average 5% per year, even though they’ve risen 7% per year in recent years. I actually find it hard to believe this would be the case over a 25 year period. This would mean energy costs would be over 3x more expensive than they are today (without factoring in inflation) by 2031.

As energy prices rise, the viability of various technologies to make energy generation more efficient rises. But if we do assume this number is correct that just removes the interest portion from our calculation and results in a monthly cost for solar panels of $83.39, which is still more expensive than simply buying the power from Bullfrog.

This advantage might disappear if there were financial incentives offered for providing solar power to the grid, but so far I’ve been unsuccessful at finding any. I had heard that the price paid for adding power to the grid was significant, but have also heard from someone else that those incentives are no longer available.

In addition, when those subsidies were offered, there was no commitment as to their term. An incentive that can be withdrawn at any moment is not much of an incentive at all. I’ll have to investigate further.

Posted by Colin
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Design Meeting #5

December 19th, 2006

Our fifth design meeting continued to refine the garret and the access to it. It now includes an area which will be open to the ground floor and should act as a large chimney to allow hot air to rise and vent out, in the summer. We decided a curved, narrow but fixed staircase would be the best way to access the garret (instead of a pull-down staircase that would be less stable). The area will also include a narrow walkway through open ‘chimney’ to get to the attic space at the front of the house.

I took this opportunity to discuss my previous ideas about the economics of solar panels with Alex. He had read the article and suggested I’ve messed up the math in a couple of ways:

  1. I didn’t include the usual 5% rise in energy costs (5% is used even though energy costs have actually averaged 7% in recent years).
  2. There was no allowance given for the financial incentives offered by the utilities.

I’ll continue the discussion of these factors in the follow-up to the solar panel post.

Posted by Colin
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A river ran through it?

December 18th, 2006

When I was chatting with one of our neighbours yesterday I found out some interesting hearsay history of our property. Apparently he was talking with another neighbour who’s father built the houses a few doors down from us, and her Dad told her that a river used to pass through the area where our house is now, and there is quite possibly still an underground river there.

We’ve passed this information on to Alex, of course, who is now factoring in the possible need for specialized drainage for the property, and extra insulation around the foundation.

No word yet as to whether we’ll need a geotechnical survey to confirm this.

Posted by Colin
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Vertical-axis wind power generation

December 15th, 2006

There’s an interesting video on YouTube about a new(ish) style of wind turbine called an AeroTurbine. It was developed by Bill Becker from the University of Illinois and has some tremendous advantages over traditional wind power generation.

In particular, his turbine doesn’t require a constant wind source; It works just fine with gusts of wind, as are common in urban settings. Also, this type of turbine cannot be spun too fast, whereas horizontal-axis turbines need to be shut down in high winds. AeroTurbines apparently run much quieter than H-axis wind turbines (though I’ve personally stood right beside a wind turbine and couldn’t hear a thing).

They are hoping to promote AeroTecture amongst architects to better capture wind with these devices in newly constructed buildings.

Unfortunately, no projected cost information is available at this time.

Posted by Colin
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Generating your own solar power seems wasteful

December 8th, 2006

As mentioned previously, we aren’t going to be able to afford solar panels for our house, initially. We are planning space and wiring for them, and are confident solar technology will become quite affordable within a decade. Unfortunately, even our smallish appetite for 350kWh/mo. can only currently be sated by a $25,000 photovotaic array (factoring in the amount of sun we’d receive in Toronto).

But considering 350kWh/mo. only costs $49.221 from Toronto Hydro, I decided to run the numbers on the approximate cost of ownership for solar panels and was very surprised at the result. The disruptive force in the calculations was Bullfrog Power.

Provider Monthly
(25 year span)
Monthly
(35 year span)
Total
(25 year span)
Total
(35 year span)
Toronto Hydro1 $49.22 $49.22 $14,776.00 $20,672.40
Solar Panels3 $146.152 $104.392 $43,844.25 $43,844.25
Bullfrog Power1 $65.52 $65.52 $18,756.00 $26,258.40

Even though I’ve skewed the numbers in support of buying solar panels, that option is still 60% more expensive, for no real benefit to the environment (considering one can buy clean power from Bullfrog).

When I first thought about writing this entry, it was supposed to be about the revolution of distributed power generation that will come with low-cost, high-efficiency solar panels. But now that I’ve run the numbers I don’t see that happening.

A relatively small power generation company like Bullfrog can already sell green power at very reasonable prices. Given the overhead involved in managing one’s own power generation, Bullfrog are in a much better position to take advantage of changes in technology than individual consumers are. When prices drop for individuals, they’ll drop even more for Bullfrog, and other power generation companies.

In fact, companies are just the sorts of long-lived entities that thrive on long term capital investments such as solar panels… when there is actually any profit in it. The fact that no power-generation company is generating with solar (at least not around here) leads me to believe that buying solar panels for home power generation is terrible investment (financially and environmentally). For those living anywhere near an urbanized area, it seems likely there will always be a company able to generate green power with the latest technology far more efficiently than any individual could.

Using solar water heaters in the home still seems like a good idea. (Water can’t be heated ‘cleanly’ by someone else and then piped into your house.) But this also raises a question: If heating our home or water via non-solar means, is it better to do it with less efficient but green electricity, or more efficient but dirtier natural gas? I will have to do a few more of these types of studies on the cost of solar water heaters for tap-water and radiant floor heating vs. electrical heaters.

At the moment, I’m thinking the answer might just be Bullfrog.

FOLLOW-UPS TO THIS POST ARE NOW AVAILABLE (Follow-up 1, Follow-up 2).

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1 Factoring in GST, the cost of power from Toronto Hydro is $13.17+10.3cents/kWh (source).
The total cost from Bullfrog is $13.17+14.1cents/kWh (source).
These numbers are not this simplified at either of these sources. You will have to work through their breakdowns to come to the same numbers.
2 Monthly costs for the solar panel solution is based on being able to borrow money at 5% (which is probably too low) via our mortgage, and paying it down with the rest of the mortgage over 25 years. This seems reasonable as anyone with a mortgage is choosing to spend money on solar panels instead of paying down their mortgage. As such, 5% is the true cost of those dollars regardless of where the money comes from. The 35-year calculation is simply the cost incurred over 25 years, spread over 35 years. These numbers are actually skewed in favor of solar panels because of the generous interest rate used, not factoring in any maintenance over their lifetime, and not including the monthly charges for connecting one’s panels to the grid (which you pay even when you are providing power to it).
3 Solar panel pricing is for the CE20180SB kit from Mr.Solar and converted to Canadian dollars. (source).
Posted by Colin
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Design Meeting #4

December 5th, 2006

Our fourth design meeting was really good.

The plans are quickly becoming solidified, but that didn’t stop us from making significant changes here and there. The small storage room at the top of the house wsa turned sideways, at Alex’s suggestion. It will now allow quite a bit of light into the main stairwell, and the room will not block the light from getting to solar panels on the south roof.

We had also sent Alex a variety of photos from our neighbourhood showing what style of houses we liked, and which we didn’t. This was definitely a big help in shaping the ‘face’ our house would have. Taking photos of interiors and exteriors that capture your interest will be extremely useful as you move through your design process.

I would really like to post some schematics to show everyone, but I’ve promised the architect I wouldn’t show unfinished work (which I can completely understand — I hate doing that, too). As such a lot of the discussion about why we chose to position everything where we did, will have to wait a few more weeks.

Posted by Colin
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Good deals at/from Consumer Reports

December 4th, 2006

I had been doing some online research into various appliances when my googling landed me at the Consumer Reports web site. It’s a magazine I’ve known about forever, of course, but not one I ever considered subscribing to because, even though I usually do a ton of research before making a purchase, scouring through hundreds of magazines in hopes of finding a review of whatever I was interested in buying.

Enter: The Internet.

When I wasn’t looking, Consumer Reports went and got ‘it’ exactly right.

Their web site contains every impartial review they’ve published in the last 4 years (plus their buying advice guides, etc.). And the whole thing is searchable so you can find exactly what you need in seconds.

A significant portion of the site’s materials are absolutely free, but subscriptions to the full web site for a one year is just $26 (or $6/mo.)!

If you still don’t feel compelled to visit their site when trying to find the right gear to put in your home, then I should also mention their companion site: Greener Choices. Greener Choices deals specifically with those items that can help to conserve resources, including your cash; the reviews list the estimated annual cost of the energy that will be use to run the device.

This is so precisely the information resource I needed I am frankly, just a little stunned. The information on the Greener choices site is actually free, but is so relevant to me at the moment, I’m happy to offer them the very reasonable fee for the subscription to the regular magazine.

Posted by Colin
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