043. The 2009 Solar Decathlon winner is Team Germany

A little diversion away from our house building story. I had the pleasure of visiting the first Solar Decathlon competition in Washington DC back in 2002 and now I try to follow it "virtually". The winner of the 2009 competition is Team Germany from the Technische Universität Darmstadt with their surPLUShome. Incidentally, Darmstadt is the home of the Passivhaus Institut I've mentioned on this blog before.

Here is a description of the event from Wikipedia:

The international and biennial event is sponsored by the United States Department of Energy and the National Renewable Energy Laboratory (NREL). Competing colleges and universities build solar powered homes and operate them on the National Mall for 3 weeks every other year.

The point of the competition is not to create new building technologies. On the contrary, entrants have to use commercially available products to demonstrate that a sun-powered home can be commercially reproduced.

Link → US Department of Energy's Solar Decathlon Homepage
Link → Team Germany Homepage

042. From Minergie to Minergie-P (rejoice!)

Figure 33. The new calculated energy balance for the house. The numbers are in kWh/(m²). Compare to figure 23.

Back in April I had started to write a little about the calculations of the projected energy usage that had been done based on the components making up the house. Since then much has changed and the structure of the house is now going to be made entirely of wood[1]. The windows have been upgraded to have better energy performance. We also have a new energy planner who is a better fit for our project. He changed the heat pump to a better-tested model, added 4 m² of solar collector (for hot water) and an Erdregister (earth tube heat-exchanger). The result of all these changes is that we now have an optimized system with lower numbers. Numbers that put us firmly in Minergie-P territory!! Read on for more information...

First, the quantities listed in the diagram above are:

- Q_iP: heat generated by the residents.
- Q_iE: heat generated by the electrical equipment.
- The total internally generated energy is Q_i = Q_iP + Q_iE.

- Q_S: heat delivered by the sun.
- The total gain Q_g = Q_i + Q_S.

It is assumed that only 60% of Q_g can be used by the house:
- Q_g,u = 0.60 Q_g
- Q_V is the energy lost through the ventilation system.
- Q_t is the energy lost via transmission through the shell.

Also back in April, in post 021, I had written about the requirements of Minergie. Here again is the relevant equation (refer to the old post for details):

With the new construction plan, the various energy demands are computed to be:
Q_H,eff = 13.9 kWh/(m²·a)
Q_WW = 6.7 kWh/(m²·a) and the rest is met via solar energy
Q_V = 2.51 kWh/(m²·a)

This gives a weighted energy demand of 20.7 kWh/(m²·a). The limit for Minergie-P is 30 kWh/(m²·a), so we are comfortably within this requirement. This is great news!

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[1] In the earlier plan, the lower level was going to be made of concrete and bricks, and the upper level out of wood.

041. The excavation

Figure 31. The excavator operator checks his work against the plans from time to time. Figure 32. The trench for the sewer pipes has been dug.

040. Preparation of the construction site

Figure 30. View from the south-west, looking at the excavator sitting on the north part of the land.

A lot of things have happened over the last couple of months but I wanted to wait until the dust settled (so to speak) to do an update. It's high time for it now, as yesterday the ground preparation work started.

We hadn't had the land mowed in months and the ground cover was really quite dense so the first thing that was done was that the sod was turned over using this excavator. I think most of the top layer will be stored on the site, to be used to fill in after the construction ends. The material that is dug out from lower down will have to be transported away and dumped.