net zero energy house

A Net Zero Energy Year - Oct 18-Dec 15 2010

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Free heat bathes the Mill Creek NetZero Home’s east wall.

October 18 – Dec 15

    • Net Import: 1995 kWh
    • Net Export: 391 kWh
    • Total Production: 572 kWh
    • Total Consumption (imported + production – export): 2176 kWh

On the production side, we produced about 9.7 kWh/day when our annual expected daily average is 23 kWh/day.

I’m a bit concerned that we consumed such a boat load of electricity over the past two months. We used 37 kWh/day. Most of that is space heating energy. Our annual expected daily average use is 23 kWh/ day.

I still think we’re in the game. The months clustered around the winter solstice will understandably be when we consume the most and produce the least. Last year we pretty much stopped heating on February 12th, so even if we burn up a large deal of our energy budget by then, the good times will have arrived.

Whatever happens, there will be no denying the numbers.

Today’s readings (October 18 readings in parentheses):

  • bi-directional power meter (total import and export of electricity for the house):
    • import: 6155 kWh (4160 kWh)
    • export: 3327 kWh (2936 kWh)
  • inverters (cumulative production from each of two PV arrays):
    • fixed modules: 3881kWh (3683 kWh)
    • movable modules: 990 kWh (616 kWh)

 

A Net Zero Energy Year - Assumptions

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From a presentation that I gave a couple of years ago, the above slide shows the assumptions that we made in claiming that the Mill Creek NetZero Home (MCNZH) will produce all of the energy that it needs on a net annual basis. We got the numbers by running HOT 2000 simulation runs, estimating hot water consumption (ignore the stuff about WATSUN – it proved to be inaccurate), making best guesses on appliance use based on Energuide numbers, and by consulting Edmonton solar electricity guru Gordon Howell about how much production we would get out of our PV modules.

There are three adults (one with his own stove and fridge downstairs) and two chillins living in the house.

After living in the home for 1.3 years, the space heating number looks low. On the other hand, the appliances number looks high.

I think we’ll be in the ball park, at the very least.

A Net Zero Energy Year - Questions

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We began our Net Zero Energy Year on October 18, 2010.

I have gotten some strange looks from people after telling them that we won’t be using our wood-burning stove this year. Here are the the questions that we are trying to answer:

  1. Will the Mill Creek NetZero Home (MCNZH) produce as much energy as it consumes between October 18, 2010 and October 17, 2011?
  2. If so, was   the year between October 18, 2010 and October 17, 2011 (in retrospect)an average year for warmth and sunshine? If not, would the MCNZH be Net Zero in a non-average year (sunnier/less sunny and/or warmer/colder)?
  3. How accurate were our computer simulations (HOT2000)?
  4. Can a true Net Zero Energy Home be built in Edmonton?
  5. How does our passive solar design behave in different situations?

Burning wood would make the data that we collect less reliable, because the amount of energy that any given armful of wood contains is an estimate. So we’ll abstain from our stove for a year.

Also, help is on the way for tracking energy use. I’ve just ordered a TED 5004-C so that our energy consumption and production can be easily collected and published to the web. More on that later, as well as more on how the Solar Energy Society of Alberta is helping our little monitoring project out.

A Net Zero Energy Year - Beginning

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(our bidirectional electricity meter – the first reading is how much power we had purchased from Epcor as of October 18, 2010)

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(how many kWh we had sold to Epcor as of October 18)

The concept of a net zero energy building is a brilliant one. For one thing, you can explain it to anyone in one sentence. For another, it sets a non-arbitrary goal. I think that most people have a gut feeling that if every part of the economy gave as much as it took, we would be approaching true sustainability.

From the beginning we have confidently declared that the Mill Creek Net Zero Home would annually generate as much energy as it uses, on a net basis. However, our assertions have been based on computer modeling and rules of thumb. That, and a good dose of optimism.

In fact, I’m not sure that we have a “proven” net zero energy building in Canada yet.

We aim to change that. Our PV modules are all installed now (more on that later), so it’s time to start a year of monitoring. We will only do one year of highly accurate measurement, because to make it a true test we have to abstain from burning waste wood in our wood stove. Since we are loathe to heat with coal-fired electricity  (even if we are offsetting it with solar power), and since the wood stove is such a nice way to heat a house, we only want to go through one winter without wood heat.

So on October 18, 2010, we began our year of monitoring. On that day, our meter readings were as follows:

  • bi-directional power meter (total import and export of electricity for the house):
    • import: 4160 kWh
    • export: 2936 kWh
  • inverters (cumulative production from each of two PV arrays):
    • fixed modules: 3683 kWh
    • movable modules: 616 kWh

I’m not sure how convincingly this experiment will “prove” that the house has achieved the net zero standard. Even if we do net out, I can’t absolutely prove that we didn’t burn any fires. We will be dismantling the stove so that we can seal the chimney off from letting cold air in. I'll post pictures, but besides that ya'll will have to just trust me!