Sandia, Stirling Energy Systems set new world record for solar-to-grid conversion efficiency

Interesting that they are using Stirling Engines for the conversion of heat to power.

Let's hope that solar cells can be built, with at least 70% total efficiency, that will remove the heat/mechanical/power transformations.

Kind Regards....

A quick search of the web shows solar cell efficiency has reached 42.8% although that isn't in high volume production yet. Still it is much better than the 31.25% efficiency for the Sterling Engine system. It makes you wonder why they are even bothering with the Sterling Engine approach unless it is much cheaper. I'd love to see metrics attached to these stories of $/KWH so we could compare them. Some of the plastic or thin film solar cells are much less efficient (~6%) but are much cheaper per square foot so they become cost competitive on the $/KWH basis. Ultimately its the cost which will determine whether I gets used on a wide scale basis.

Irving, you are right on, regardless of the efficiencies with solar cells vs heat engine driven power generation, it is the costs that matter. Today, the best commercially available solar cells are set at around $4 per watt, give or take 50 cents. If the sterling engine driven generator can provide its power at around $0.40 per watt, then it is competitive with conventional power stations. All of this is initial costs of a turnkey installation, of course. Sunlight is free, so, after the equipment is installed, than the costs of the power would be free or simply the costs of maintenance plus the payout for the original installation. One must consider the life expectancy of the equipment, too. If the payout for the equipment plus maintenance is 10 years and the life expectancy is only 5 years, then it becomes a loosing proposition, however, reverse the figures and you have a winner.

AH, but you miss an important point. While CELL efficiency is reaching above 40% in controlled lab conditions, this claim is for SYSTEM efficiency, for grid electricity. Put cells into modules, then modules into arrays, then arrays through an inverter, and PV SYSTEMS are in the low to mid 20% range. Compare CELL efficiency to the thermodynamic efficiency of the Stirling cycle, which should be in the upper 40%'s.

Costs of CSP systems are touted to approach 6 cents/kW-hr, though current systems are more like 12 cents. Available PV is in the 20-40 cent range at best, but coming down.

And with SOFC efficiency at 50-60% for direct conversion of Methane into Electric power and by co-generation (via sterling heat engine for generation, and for home heating and hot water) at 25 t0 40%, at 85% to 90% efficiency, the cost is down to around $400 per kilowatt (Siemens next generation system to be on market this year or early 2009). That means a three fold reduction in greenhouse gas emissions, three times less fuel costs (natural gas = methane). If biomass digestion is used to produce the methane (and a new system to produce hydrogen directly using E-coli bacteria being developed at Texas A&M) than the costs are reduced still more. The sterling heat engine would be one of several heat engines for mechanically generating power, however, keep in mind that most home owners do not have the expertise to maintain a mechanical system while the direct conversion by SOFC's is virtually maintenance free, just an annual replacing of the sulfur filter is all that is required. Carbon is a very useful material if use properly and not wasted in big fast car toys for little boys street race.

In the long run, we will need all of the clean energy systems, both available today and those being developed. We cannot be so simple minded to sit on one system and say it is the final solution. We will need solar power, wind turbines, heat engine driven generators, fuel cells, batteries, and biomass conversion. We will still need fossil fuels, too, but in a far less amount. Coal and Oil is a primary source of the feed stock or plastics and high strength carbon composites. Carbon is a very useful material if use properly and not wasted in big fast car toys for little boys street race.

The plus of the Stirling is the fact it will work from whatever is available, Solar, Methane, Geo, or Trash. Another plus is that it is public domain technology.

I agree that it looks hard to make and maintain, though there is a company making a refined updated Stirling.

Still I think we do need to determine what is good enough, and a workable core system that is affordable and powerful enough to supply the average American Home off grid.

Many homes in the US run fine from 100 Amp power boxes. Many Mobile homes come with 50 Amp supplies. Of course Electric Heating units suck energy so a gas and electric combination is required in reality for cold climates.

Low temperature zone also mean that biogas production is slowed or inhibited since there is an optimum temperature range for the process. Above ground biodigestion backyard plants where the common fuel oil tank sat, would at least need to be painted black in higher latititudes, if not put in black plexi sheds.

Still there are infrastructure decisions to be made.

For instance, how do you actually imput a SOFC into your house? I have never plugged a Solid Oxide Fuel Cell into anything. My house runs my computer and the lights and the fan and the tv and the radio on AC power, unless I run the radio or one of the tvs on the batteries, which are DC. I marvel that some of my stuff will work when the grid is down during ice storms.

It is suggested that if SOFCs are the best Alternative Power Source, then all Square D or Siemans Power Panel Distribution Boxes come with an imput and back feed block out bullswitch so they prepare the path for their powersource to be readily useful as purchased and sold by them.

Cutler Hammer also makes the Distro box that feeds your house, building or boat.

Component design for such power boxes where the breakers go would acommidate an inverter to convert DC to AC, and all new stuff really needs to cut back on the Watt wants.

In the end we do need to adopt a standard of imputs and outputs that is safe, reliable and adjustable.

220 and 110 AC plugs of European Standards need to be internationally standardized so to work from the SOFC and other system offerings.

and that is where I am at in this today. Good to you Chtank. Love Russell

P.S. A system for the simple minded is good.

I knew I was missing something so thanks for filling in some of the missing pieces. It's good to see all this renewed interest and work on alternative energy systems. The last time I saw it was in the mid-70's during the "first" oil crisis but after that was averted by importing oil the $ incentives to develop alternative energy all but disappeared. I don't see a similar bail out on the horizon so it looks like alternative energy will become a much bigger part of our lives in the future.

I supposed one advantage to a Stirling system, is after it gets dark I can always build a fire under one end?

http://www.abc.net.au/news/stories/2008/04/24/2225980.htm

As long as the coal holds out.

I like it! Solar cells definitely aren't as flexible as a Stirling system. Sure any heat source would do, fire, a pile of manure, geothermal, even a big hug! Have you hugged you Stirling system today?