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Solar Decathlon

coloradosolardec.jpgThe Solar Decathlon is a competition sponsored by the US Department of Energy in which university and college student teams compete to design, build and operate energy-efficient solar-powered homes. Taking place on the National Mall in Washington DC, the event is open to the public through this Sunday. 18 teams competed in the Solar Decathlon, including teams from Puerto Rico, Canada and Spain, and the winning home designs were announced today. Colorado came in first (picture of the winning home to the right), followed by Cornell, Cal Poly, Virginia Polytechnic Institute and the New York Institute of Technology.

The designs vary dramatically, in part because the various institutions had access to differing funding levels, and in part due to the diverse philosophies underpinning the teams.

Cal Poly went with a minimalist approach, for example, while the Cornell team added a sophisticated custom Energy Recovery Ventilator system for a high-efficiency smart house. The top design, from the University of Colorado, emphasized the use of biomaterials in the insulation and building materials. The overall designs vary from the conventional to the futuristic, although most stick with a modular "pre-built" home layout; a gallery is available of the 18 different homes. Regardless of their layouts, all of the homes show a dramatic reduction in energy footprint compared to an average mainstream dwelling.

The competition is called a decathlon because the teams used the homes to compete in ten different contests, covering technical features, building aesthetics and usability, and the ability of the teams to explain what they've done.

Each team is judged on its solar home's architecture, livability, comfort, and ability to provide a consistent supply of electricity to run appliances, provide ample lighting, and charge an electric car. The homes must also be able to supply hot water for daily use. In addition to the design- and energy-related requirements of the competition, teams must also provide documentation about the development of the design of their homes and communicate about their homes to the public.

The final test -- and among the most critical -- was the Energy Balance contest: since all of the homes had to be entirely self-powered, this contest measured how much power remained in the backup batteries at the end of the week. The closer the batteries came to its starting level, the more the homes' self-power and usage efficiency balanced out.

Although the efficiency and power measurements undoubtedly could have been even more detailed, I appreciate the variety of contests in the Solar Decathlon. Super-efficient homes will not be adopted if they're not aesthetically appealing or are less convenient to use. The Solar Decathlon is a reinforcement of the argument that engineers need to understand design just as much as designers need to understand engineering. It's not so important that these are the homes of tomorrow -- the key result of the Solar Decathlon is that these are the home designers of tomorrow.

(Thanks to George Mokray, John Maas, and The Oil Drum)

Comments (12)

Dan Freedman:

Since the readers of this site seem to be "in the know." I had a idea that I wonder has been thought of before. Has anyone ever considered having a mobile solar array? The idea being, just put some large solar panels on the back of some 18 wheeler trucks (which if possible would run on the solar power the panels provide), and in the case of a wide spread outage like those seen after the hurricanes, the trucks could be dispersed into an area to connect into the grid and provide a local energy supply. This would only be useful of course until solar remains to expensive for wide spread usage in cities. Any thoughts?


I wonder what the CU mobile solar house would cost if mass produced. I would think that this would be a great way to introduce the technology quickly, help the solar industry, and lower costs at the same time. The onesie, twosie approach we are mostly using now isn't going to get us where we need to be quickly enough.

Kudos to CU. The won at the last Solar Decathlon as well.


Actauly I expect some day a solar tend in a box will do what your asking about dan.

Basicaly a massive solar tent thats set up and provides both shelter and power right off the bat.


I only repeat myself because it seems so obvious and yet nobody seems to want to pay any attention.

You want solar power? Well, biomass is solar power, and at any given time and place there is a hell of a lot more biomass lying around than there is solar energy, esp if it comes from PV, and all the stuff that has to go with it to make it actually work.

So stuff the biomass into a burner, even a crummy one, heat a stirling engine with it, and get big gobs of power , without all the whimpy PV fiddle-faddle and prayer dances for a clear day.

There are at least a couple of companies which used to provide PV (and in some cases wind) power for outdoor concerts. That's where I'd start looking for the big power trailer Dan Freedman is asking about.

As for secondary solar power, like biomass, Dean Kamen of Segway fame has a Stirling engine design that he is developing. It will also purify water as part of the process. It burns biomass. Problem is that burning biomass releases smoke and smoke is pollution and part of that pollution is CO2.

People tend to like the idea of PV because it is such an elegant concept: sunlight hits a crystal and electricity comes out - MAGIC! Of course, it's not that simple but that's the idea for most people. Install it and it should last for 25 years (single crystal and most amorphous and polycrystal panels). No muss, no fuss.

Biomass is much more complex and looks like a return to the wood-burning stove, even when you use a Stirling engine. Somebody has to feed the fire.

Personally, my favorite solar device is Edward Sylvester Morse's passive ventilation system which he patented about 1888. He built a glazed box on the south side of his Salem, MA house which had slate shingles as an absorber surface and vented openings into the house and to the outside air at the bottom and the top. The two vents allowed the solar collector to heat the house in the winter (close both bottom and top vents to the outside and open both to the inside) and cool the house in the summer (open the top vent to the outside and the bottom vent to the inside). Morse lectured on the device at MIT and installed another, probably larger version on the Boston Athenaeum although nobody there seems to remember it when I asked some years ago.

These days, such a device could be improved in a variety of different ways - replace the slate absorber with a copper selective surface, install a PV fan as a "natural" thermostatic control, use bimetallic strips to activate the vents at set temperatures, add phase change materials or thermal mass for storage...

And then there's Charles Greeley Abbot's parabolic trough oven from the early 20th century which used a clock motor and counterweight as the tracker and oil as a working fluid to generate termpatures high enough to bake bread.

Ain't history grand?


well jamais, I never heard of this but who know, maybe if we smarten up we'll all be competing to make solar powered homes, but this was a good idea to do.


i also like wintermanes idea too


Ok, but just a few further comments on biomass. You don't have to feed the fire, modern pellet stoves allow you to be just as lazy and subject to cardiovascular disease as if you were burning methane (natural gas). It's all quite automatic.

And as for CO2, the carbon dioxide from burning wood came from the atmosphere when the plant grew, so the net gain to the atmosphere is zero. Any fossil fuel adds to the carbon burden, by definition of fossil.

And for smoke, modern wood burners put out less than nearly anything. I can put my head in their exhaust and feel nothing but warm wet air. No smell. But don't keep your head in there too long- very little oxygen.

And, where do you get the engine? Look for British Gas MocroGen, and buy it from them. A very nice compact 1kW engine- alternator that has excellent efficiency, no noise, extremely long life since it is sealed like a fridge, and could put out honest red-blooded American 60 Hz 120 VAC direct to your hair blower or furnace or the grid without a lot of magic electronics in between. In the BG home boiler system, the stirling is running at 50 Hz. on nat. gas, but it is quite willing to run on any other stream of hot gas from any heat source, such as a cabal of fossilized executives.

All of the above is much cheaper than PV per kW-hr, and runs rain or shine, night or day.

Cabals of fossilied executives are very expensive although not in short supply. Other than that, your system sounds pretty good. Has anyone built one yet?


Speaking of historic low tech passive solar houses, Ralph Middleton Munroe, naval architect and founder of the Biscayne Yacht Club in Miami, built in the late 1800's a passively cooled house. Having seen it years ago I cannot remember the exact details, but basically it pulled cool air into the wooden central court atrium structure through subterranean openings, venting the rising air out through soffit roof vents, thereby creating continuous space-cooling air flow through the house in Florida's hot summers. The building, known as the Barnacle, is a national historic site in Coconut Grove.


Right, gmoke, people have built one alright, but until some senior manager of a team of product development people has the guts to say "go" nothing will happen in the real world.

Don't expect this in the US, but it is pretty likely in Brazil, Singapore, Tiawan, Korea, China or some such more enterprising place. After all, the components are all there, and there's even at least one all-up working prototype. Classic case of $100 bill lying on sidewalk. Who gonna pick it up?

Meanwhile, I too like the passive solar ideas, and have actually used a very simple version in a guest house. Works great. Never freezes even in beastly cold dark weather, of which I have a plentiful supply.

Ah yes, the business end. I've got a whole series of small scale solar products I'd like to see come to market. No interest as these things are not protectable, not patentable being "obvious" improvements on existing products and can easily be back-engineered by the Chinese.


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