Woodgas + solar

ok maybe not practical, but maybe worth exploring? Right now we take woodgas to power a mechanical engine. If we want electricity we then hook up a gen.

what if you had some solar panels out and during sunlight hours they generated electricity. Then during the night you had a giant Woodgas light bulb that you focused onto the panels?

Perhaps even making a big ball of solar panels that surround the Woodgas lightbulb.


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all this is fine, but there is one “but”, this is a coefficient of useful action … In simple terms, more energy will be obtained if the generator gas is used to directly rotate the generator of electricity in order to obtain energy for consumption and charging the battery.


Now how to apply Joni’s coefficient of useful actions; is easy . . . just count your energy form transitions steps.
Each form change will have a loss-price of minimum of 10% to 30%. In the true: Rob, Peter to Pay, Pauls of Life that man-in-the-middle always takes his bites.

The SUN the common at one end of each energies change strings.
Useable electricity power at the other end.
Sun → PV-watts → Battery-in → Battery out, useable electrical energy.
Sun → to wood growth → wood harvesting/preparation into fuel wood → Gasifier made fuel gas → Fuel gas in engine to shaft power → Shaft power to electrical generated power → Your electrical light made energy for the PV array. THEN you begin the PV string of steps.

You do not even have to use numbers to see the obvious many little bites to near nothing end useable.
Nice try though.
Shows you are interested and thinking of DIY.
Steve unruh

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Well said. I was just thinking investing your efforts in more storage would give a better return on investment.
Batteries for 2 days storage plus a big thermal mass that can be heated by both electricity and direct thermal to thermal exchange of energy. When you are short of electricity from the PV plus storage convert your wood stored energy into electricity and thermal energy and refill those storage tanks.
I keep thinking I would love to play with a Stirling engine like the Robertsons design for both thermal and electric power but my list of projects is too long. I just look at it as a wood stove that makes a small amount of electricity while also making some domestic hot water. I mostly think one of those spinning in a workshop would just look so cool. It is a dream at this point but your comments about energy looses reminded me of it because having the wood provide both space heating and electricity would increase efficiency.

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True useable, reliable, clean, safe CHP (combines heat and power) is the end-game we are all pursuing here.

But all of those damn Devilish details. Annoying residuals, and minor side effects . . . they do add up.
Count, account to better results. Less false hopes pursued.
As you say . . . only so much time/money/honey-interest in any fellow. Budget wisely. Re-interest regenerates so slowly once squandered away chasing woo-woos. She will feel left-alone too long. Leave you. Divorce you.

Why I focus on the Rurals living. They are the ones who can step back and intergrate an acre, five acres, more; as a whole system of CHP. Not just one cutesie’ small footprint live -in-your-basement device.
WayneK once leaked out a picture of some of his past wind machines in the back ground. Questioned he was mum. Hard worked efforts flattened to the ground. Hmm. He lives in an annual wind-shears/tornado’s area. You can see from his success now he learned to use this, then. The winds will mostly do my trees to the ground for me! I just have to gather it up and turn it into my heat and my powers too.
Steve unruh

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No I am not talking about an electric bulb. it wouldnt be woodgas > engine > gen > bulb. it would be woodgas > propane/natural gas bulb. ofc you lose energy coverting so many times. I read something like .07 m3 for a 100 watt equivilent gas burning bulb.

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Tanner, what a fun topic. You should look up what powers the pioneer and the Voyager spacecraft. They use RTG radio thermoelectric generators. They have a heat source that uses a Peltier junction to create electrical current. Sadly peltier junctions right now are only about 6% efficient similar to using a coal-fired steam locomotive. The cool thing about the Voyager RTG is that it’s still producing power even though there is no solar, in fact a voyagers are in interstellar space. This is probably more practical than trying to make higher frequency visible light with the flame of a wood gas flare.

This an example of a 12v producing Peltier junction.


@skirmisher, what is the reason to look up for such a solution? To spare wood during the daylight? Reuse the electricity generation capability of solar panels? Just being curious if it works?

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My guess is that wont work well that you will probably not get much light at the frequency the solar panels need and if you try to reflect it into then you will over heat the panels at which point their efficiency will drop off rapidly. Over heating is one of the biggest problem with the efficiency of solar panels so burning something to light them doesn’t seem productive. Just take a single small panel and test your theory put it in full sun measure the output then try your gas light off your propane tank before you go to far. My guess is you wont like the results.


idk dan the heat issue is just details there are ways around that, for example we could use a 5ft diamter ball (bulb) and use a shroud to focus the light (weak laser) to a solar panel that is far enough away that it doesnt get heated from the gas that is burning

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Those worked good in space because the extra cold made a good thermal delta. On earth the biggest problem is your device eventually become the same temperature on both sides as you simply can’t wick heat off fast enough without consuming energy to do it. I looked at that technology when I was working in the laser industry back in the late 90s early 2000s I will grant you the technology had advanced but we gave up using them on the laser cooling system quickly not because of the cost or return of electricity. There was grant money that made it cost effective if we could keep it running 24/7 we couldn’t without using more energy that we recovered. IIRC we got a design of a cooling loop that ran a few hours but no where near what we needed.

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Start building and let me know how it works

I dont have the education or resources to compete with universities Dan. It seems like you have alot of knowledge in this department so I will agree with what you say.

So if the panel gets hot from the laser, then cant the laser shine into a reflective cone, which will disperse the light and spread the heat across many panels setup around the cone

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Oh my, it looks like you are trying to teach horse skating :grinning:

Listen to @DanNH. Start small, fail fast! Try small solar battery charger or something alike. Charge in sunny day. Measure the time. Next night use camping gas light till full recharge. Measure the time. Compare the time. Estimate gas consumption, eg. by weight.
And then try to make conlusions.


solar hot water heater is more efficient then solar panel for producing electrical power . And GE bought out all google matches . It is more efficient to convert solar heat to heat then electricity .
Solar water heater .

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Henry the idea behind solar PV to hot water is two fold. First you don’t need to worry about freezing temperatures. Sure there are ways to deal with them but solar thermal panels on your roof are basically a water leak waiting to happen as they age.
Second if you buy enough solar panels to be off grid the over sizing means you have spare electricity most days. Here in NH the recommendation is to size for 2 hours of full sun to meet your daily avg loads and to have 2 days battery storage capacity. That means if you get a 8 hour sunny day your panel off grid is basically suffering from 6 hours of lost opportunity as your system will be recharged in 2 hours for the full days usage. So if you have a thermal mass as a opportunity load you can get cheap storage to take advantage of that opportunity when it is there.
The last kicker I have seen on solar thermal lately is that the cost of solar panels is low enough to offset the energy loses. When it comes to money spent you are actually ahead to buy PV and an electric water heater converted to DC. It will cost less and not suffer reduced capacity in cold weather. Infact the PV will probably perform better in cold weather.
So yes in terms of energy efficiency you are correct but in terms of return on investment I believe PV plus storage wins.

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I know you are wrong . I know it is better to go with solar thermo then solar pv to hot water . I would like to show a small system but I can not .

Here is someone who did setup that test.

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Saw a tiny house show where they installed tiny solar water heater . I can not find anything like it .
I have been folowing this subject for twenty years . I do not think the best survived .

Solargenix Energy is a manufacturer of compound parabolic collector, solar heat exchange and solar water heating systems for residential and commercial markets. Compound Parabolic Concentrating (CPC) collector focuses sunlight onto a high efficiency absorber tube.The Compound Parabolic Concentrating (CPC) collector can be used for solar water heating, and space heating.
8/18/15 5:51:08 PM


Hey All,
Have you ever heard about a solar furnace? My current theory on an ultra low cost home heating system would be to build a rocket mass heater, and then use a solar furnace to heat the cob bench on sunny days, and wood on cloudy days. All bold text are good search terms on youtube.

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