ASK THE EXPERTS: Steam Electricity

Intermediate
Wood-Burning Steam Engine
Dan Fink's wood-burning steam engine.

I live in an off-grid cottage and my biggest energy expense is for propane, which I use for space heating in winter. Because my farm has more firewood than I can possibly use, I’m planning to install a wood-fired, water-heating stove to eliminate the need for propane. I would like to find a way to convert wood to electrical energy as a backup, so I don’t need to rent a generator and can run electricity to other dwellings and buildings on the farm.

I know this technology was around long ago, because steam locomotives used it to generate electricity for their running lights. Only 100 to 150 psi of steam was needed. A small boiler/turbo generator could be installed for backup or full-time power as needed, with no dependency on outside energy sources.

Are there any companies that make small boiler turbo generators (5–20 kW) that could be run on wood?

Clyde Koral • via e-mail

 

You’ll likely be out of luck trying to buy a commercial, home-scale steam turbine generator that burns wood, for two very good reasons—safety and practicality.

Water expands to 1,700 times its original volume when heated to steam, and each gallon of water in a boiler carries the potential energy of a stick of dynamite! Boilers for steam turbines and steam engines must be monitored constantly, especially when burning fuels like wood where the energy density varies from one chunk to the next. Even a 10-minute trip to the fridge for a soda and sandwich is too long to leave a woodfired steam system unattended.

We have a wood-burning steam engine here at our off-grid shop, spinning a 2 kW alternator, but it’s there for fun, not to depend on for backup electricity. Someone has to monitor, stoke, and water the boiler all day long, thus getting little work done in the shop, making steam backup power impractical for us. Steam power is fascinating, though, and there are many science-fair-sized steam turbine models on Internet video sites, or you could join a steam-engine enthusiasts club for help in restoring an antique or building your own.

There are other options besides steam for making electricity from wood, but all are complicated and expensive do-it-yourself projects at the 5 to 20 kW scale you want:

  • Stirling cycle engine: These heat-powered machines are quite safe, but very pricey. Plans for machining and building your own are available, but few actual products larger than toy model fans for your wood heater exist. Plus, they have a reputation for early failure.
  • Thermoelectric cells: Also common in wood heater fans, these use the Peltier- Seebeck effect to make DC power directly from heat. Modules of 25 to 100 watts are very expensive, and past products have suffered reliability problems from overheating.
  • Wood gasification: This technology uses heat and chemical reactions to break down wood into flammable gases for burning in a standard internal combustion engine. Tens of thousands of vehicles were retrofitted with gasifiers in Europe and Asia during 1940s wartime gasoline shortages. You can buy a parts kit today to build your own, and plans abound. However, wood gas is not a “hit the switch and forget it” sort of fuel, and deadly carbon monoxide is one of the gases it produces and burns. You can’t just throw logs into your gasifier; charcoal, sawdust, or very small chunks of wood are required. Gasification is a very advanced do-it-yourself project, but is probably your best bet if you choose to continue your quest.

Making electricity with firewood is a difficult way to go, and requires lots of time, money, advanced skills, and imperturbable enthusiasm. If I had a huge surplus of wood as you describe, I’d harvest sustainably, sell the extra wood, and invest the proceeds in greater energy efficiency for my home and more solar-electric modules for my roof.

Dan Fink • www.otherpower.com

Comments (8)

raoofahmedkhan's picture

Is Solar power really worth?
1. We need batteries to store it as backup this is recurring cost.
2. The life of Solar is at max 25 years and after first 10 years the efficiency starts declining gradually.
3. Security for such a big plant is always a problem of its size.
4. Roof top solar power will be of small size which will be sufficient to the same home and cannot be put to commercial use; in general.

There could be many more ways of Renewable Energy (RE); perhaps wind and bio waste can be put to better use for power generation.

Michael Welch's picture

Ian responded to you from the home-scale perspective, but let's also look at it from the utility-scale perspective.
1. Yes, it is true that solar only happens when the sun is shining, but the peak production times are the same as peak-usage times: when millions of air conditioners are running across the nation. Solar can, and increasingly has, rid us of the need for expensive, occasionally-run peaking power plants.

If comparing to fuel-fired plants, they have recurring expenses constantly -- in the form of coal, oil, gas, wood, or uranium fuel rods.

2. The life of a PV module is more like 70 years, and yes the efficiency declines gradually. Warranties are around 20-25 years.

3. All utility-scale plants require similar security, the exception is nuclear which requires a huge amount of military-type armed security.

4. Just imagine if every rooftop that had solar exposure had PV modules on it, and just imagine if Americans became energy-smart, as solar enthusiasts often are, and reduced their usage to something more reasonable than the average wasteful utility customer. We could close, and not build, more fuel-powered plants.

Wind SHOULD be exploited more, but it also has a similar concern in that the wind is not necessarily blowing when utilities want the energy. Burning biowaste can be problematic. First, it releases CO2 very quickly into the atmosphere. Of course, even natural decomposition releases it, but much more slowly. But a big problem is the other pollutants that are released.

Ian Woofenden's picture

Hi Raoofahmedkhan,

Solar electricity is usually the easiest, most cost effective, and most reliable way to generate clean energy. Larger scale renewables are -- of course -- more cost effective, but residential systems make lots of sense!

Batteries are only needed if you are off-grid or have a strong need for utility outage protection.

My first solar-electric modules were installed in 1984, and they are still going strong. Most modules today are warranteed for 25 years of energy production, and a prediction of 40-50 years of useful life is not unreasonable. It's a remarkable technology.

With net metering, batteryless grid-tied systems can use the grid as a sort of storage battery, selling the regular surplus back to the utility for credit, which can be used when it's dark or cloudy.

It's quite possible today to design and build homes that make all of their energy on site, and a crucial part of this is a solar-electric system (other key parts are an excellent building envelope, efficient heating system, and energy efficiency throughout).

Regards,

Ian Woofenden
Home Power senior editor

Inresol AB's picture

I hope this link creates a little awareness, as I wish to inform you that our company INRESOL is now manufacturing high power 'portable' 10kW CHP Stirling engines with multi fuel capabilities. I agree that until now there hav not been many affordable solutions. The Third Industrial Revolution is at our doorstep.

KAStuff4711's picture

I was just browsing the internet and was wondering about steam powered generators. Burning wood seams like it would work. Couldn't most of the "monitoring" be done by a computer. You know, bells and sirens when the prssure gets too high or the water gets too low. Or an automatic shut off to prevent damage. Also, seems like a useful thing if you burn alot of your garbage (papers and such).

NRLY WRX's picture

Ziachan is CORRECT.

I do not know what Dan Fink was smoking and drinking when he wrote a lot of this article.

Ziachan is correct, you will not see a sterling engine or any size OR a steam turbine of relative size for home use because the power brokers want to keep humanity under their thumps to effectively oppress and profit off of....

Rather Fink wrote the article out of being naive or merely supporting the powers to be doesn't matter: the end result is the same, it is misinformation and serves to help no one.

Buckville Energy's picture

I'll ignore the insults here; I'm used to them from people who ask questions and don't like to hear the facts.
Wood fuel -- whether for generating electricity from a steam engine, steam turbine, wood gasifier, Stirling engine--has very inconsistent energy density. Each chunk of wood has a different energy density and releases it at a different rate when burning. That makes automatic control systems impractical. I have experience in both off grid steam engines and wood gasification. These systems DO work--but the fuel energy density has to be standardized, and for wood that means pellets. Same for coal--they don't toss irregular chunks of coal into a coal fired power plant steam boilers, they are ground down to uniform size and density. Same with wood. The link posted here for a portable Stirling engine is very interesting! But note that it runs on wood pellets, not sticks from your backyard or woodlot. Save those for smoking in your BBQ. Setting up a wood pellet factory in your garage is not practical. Really the most standarized wood fuel source today is Charcoal Briquettes. Not cost effective, though maybe your computer control system can be custom programmed for Kingsford vs. Kroger.
Money is certainly the driving force in renewable energy, it ALL comes down to $ per kWh, especially when living off the grid. The added step of pelletizing / standardizing wood fuels pushes the $ / kWh figure very high, which is why the "power brokers" don't use it. Great fun to experiment with in your off-grid backyard, though.
Good luck -- and always watch your steam boiler pressure.

DAN FINK
Buckville Energy Consulting | Otherpower
IREC Certified Instructor™ for:
~ PV Installation Professional
~ Small Wind Installer
NABCEP / IREC / ISPQ Accredited Continuing Education Providers™

Zlachan's picture

Making electricity with firewood can be carried out pretty safely! The problem is that the idea of having your own electricity does not go down to well with major electric suppliers! Just imagine how many households (out of the city) use firewood as a major in not only means of fuel. This is the reason why technology in the west has not concentrated on expanding research into wood fired electric generators. There are many excellent examples of safe steam use, one of which is the everyday pressure cooker! I have been designing my own steam generator for just over a year now and have not seen problems that cannot be safely overcome especially in the age of and easy access to computer technology!

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