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194 comments on DrumBeat: July 22, 2007

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AlanfromBigEasy on July 22, 2007 - 9:15am Permalink | Subthread | Parent | Comments top

I will grant that the duty cycle of such cars wouldn't really make them feasible

It depends. I could see myself using a GEM http://www.gemcar.com twice a week for a total of 12 or 15 miles/week. Such a light duty cycle might be supported by on-vehicle PV panels, at least in the sunnier weeks. None the less, occasional grid charging would be required when high use was coupled with low insolation.

As a general rule, a nameplate 1 hp electric motor can do the work of a 2 hp ICE, for a variety of reasons. Since I drive a 3,150 lb car with a 76 hp ICE diesel (it "gathers momentum") (#s from memory), I think a usable "car" can operate with less than 40 hp.

Best Hopes for Energy Efficiency,

Alan

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robert2734 on July 22, 2007 - 11:57am Permalink | Subthread | Parent | Comments top

The Gem car has a 10 grand base sticker price, 13 grand as equipped when Chrysler demoed it at old town market, and may be elgible for a six grand federal tax rebate. It will also allow Chrysler to meet federal fleet mileage requirements and keep selling dodge pickups and suvs.

If this product meets Alan's needs, that is great. I'm not against all subsidies. I'm against stupid subsidies.

The point Arizona Legislaturer was making is that somebody can sell $900 worth of solar crap for $2700 because the buyer is elgible for tax breaks. Without this product benefitting anybody.

I've got solar panels on my house of which the government paid 40% of the cost. $2000 tax credit from the feds and $3.50 a watt from the municpal owned utility. But this benefits myself and my community. And I'm not going to get rich doing this. I'll probably get a reasonable rate of return depending on future electric prices.

How are we going to produce additional electricity going forward. The three possibilities that I see are, "clean" coal for which a demo plant doesn't exist let alone a commercial operating plant, liquified natural gas which is also ridiculously expensive and then the overseas gas runs out, and wind power which is also subsidized. It is illegal to build a nuke in california. You can try to build one in arizona and run a power line here, but the bananas will try to prevent you from building the power line. Presently, clean coal is a scam, where a utility will make cosmetic changes to the coal without benefitting anybody and be elgible for federal money.

Ethanol is another method the government hands out money without improving the energy situation. Of course farmers have been subsidized since the great depression and this only differs by scale and lack of transparency.

I've read some disturbing things about the reliability of sterling engines for thermosolar plants. But it isn't my field. I wonder if they too are simply farming the government.

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Gilgamesh on July 22, 2007 - 3:55pm Permalink | Subthread | Parent | Comments top

One point, the power you are offsetting by equipping yourself with PV is the most expensive for the power utility. The peaking load has the highest cost to run (dirty and expensive fuels), it may be that you are saving the power company more money by going PV and alleviating peak daily power than they are paying you.

PV also allows you to lock in for a guaranteed amount of electricity (less .5% physical depreciation per annum) at the amount you paid originally. If power is going to get more expensive, you will save utilities much much more then by reducing the overall infrastructure needs as well as pollution.

PV panels pretty much only have 1 major pollutant, which is heavy metals, and this is a point source, easily containable in tailing ponds or using RO.

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wimbi on July 23, 2007 - 4:28am Permalink | Subthread | Parent | Comments top

Reliability of Stirling engines. I do know something about that. Not everything, but something.

The engines used by SES on sun are derived from automotive kinematic engines. These are an old design and are VERY UNRELIABLE. The scuttlebutt I got from the technicians working there is that they are "trying to bring the mean time to failure up to 8 HOURS"!

That said, I also know that several companies are working on free piston stirling engines, which have the same high thermal efficiency, and are believed by NASA to have potential to last for HUNDREDS OF THOUSANDS OF HOURS. The difference is that the free piston machines have no cranks, linkages or rolling contact bearings, nor any need for liquid lubricants; they use non-contact seals that do not wear.

Look on the web for Infinia and Sunpower.

The average person makes no such fine distinctions, and can easily fall into a funk regarding a perceived generic stirling that is "not reliable".

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eric blair on July 23, 2007 - 7:18am Permalink | Subthread | Parent | Comments top

Interesting tidbits on the SES. Does the Solo have the same problem/issue as they are one of the only shipping firms of a dish.

And for others here:
A claimed design of a sub $100 1 HP stirling existed. Nitrogen charged, made from pressed sheet metal, with an 8000 hour life to rebuild, then another 8000 hours till 'death'.
A link to the firm: http://www.omachron.com/projects.html

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wimbi on July 23, 2007 - 1:38pm Permalink | Subthread | Parent | Comments top

I spent time looking for data on mean time to failure of stirling engiines. Found very little, and that not trustworthy. All the numbers I did find seemed to say that crank (kinematic) stirlings have mean time to failure at best a few thousand hours, and that with service intervals much shorter. But the numbers tested seemed too small to give any confidence in any of the statistics.

What I did find was a few citations for free piston coolers (not engines) that had lasted about 60,000hrs without failure, and fuzzy extrapolations from that indicated hundreds of thousands of hours mean time to failure.

Now there you are, stat guys. go figure and tell me I am all wet; I already know it.

But I have a more serious question. A simple one. What is the life of a device that is sufficient to allow it to function to a time that it becomes so obsolete that a sane user would replace it?

For a wood chisel, maybe a couple of hundred years? For a car, maybe 20 years? For a computer, maybe 5 years?

I believe we can right now make cost-effective stirlings that would do that- perform well to the day that they should be recycled.

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WNC Observer on July 23, 2007 - 9:14am Permalink | Subthread | Parent | Comments top

I doubt that PV panels on NEVs are the way to go. A much better approach would be to mount them as a canopy over NEV parking spaces at parking lots, and provide metered recharging. This is the best way to match up daily max insolation with the actual location of the vehicle. As a bonus, you keep the NEV shaded during the day (thus making it a little more bearable for a non-air-conditioned trip home), and protect it from rain or snow.

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