Green Steam Engine®
Green Steam Engine Home Page Licenses technology



Patented "Flexible Rod Transmission System" or "Z" Drive

Manufacturing Licenses Are Available

Exclusive Licenses are for manufacturing rights to reproduce engines for sale, lease, and distribution world-wide. The license terms depend on the configuration of the engine (number of cylinders, 3 to 16), size range, and business plan. License terms are subject to minimum royalties per year and an Initiation Fee. Licenses are not available to make an individual engine.

Licenses are protected by Utility Patents, US patent # 6,647,813, US patent #8096787, PCT 048038, Chinese patent # ZL 200980101659.3  (2009), Indian patent 349/MUMNP/2011.    

Non-exclusive manufacturing licenses are available for two cylinder models in all size ranges. Terms depend on size range.

Do to recent retirement of the present owner, the four patents listed above are now available for purchase. Inquire by sending an e-mail or a phone call to: 949 581 2529, E-mail: mailto:rgreen999@comline.com

See detailed Engine and Market Overview at bottom of this page.

As an alternative to wind and photo-voltaic power generation, this new efficient engine is a good choice for domestic renewable energy production, for the following reasons:


·       A steam engine can run 24/7 regardless of wind, weather or time of day.

·       It is not affected by location.

·       Does not require a costly structure or unsightly towers exterior of the home.

·       Does not require permits that add to the cost and procedures.

·       Does not make noise or harm birds.

·       Does not adversely affect insurance rates.

·       Is not subject to damage from storms.

·       Can operate on a very large number of locally available fuels. (many free)

·       Can be operated on waste heat from IC engines to increase efficiency.

·       Can be operated from geo-thermal wells.

·       Can charge electric cars on household natural gas or bio-gas.

·       Produces electricity with a byproduct of hot water, space heat, cooling and distilled water.

·       Can clean waste water and grey water while operating a generator.

·       Has a very small footprint. Usually about the  size of a pallet (including boiler and peripherals).

·       The efficiency can be greater than solar-voltaic.

·       Can be carbon neutral when burning bio-mass, wood or biogas.

·       Pumps and recycles its own water.

·       Operates on safe low pressures.

·       Is self-starting.

·       Is by far the least costly to purchase and install.

·       Can provide excess power that can be sold to the grid for a profit.

In addition, the Green Steam Engine® does not require a back-up power source.


Plans for making single engines are available for two cylinder engines only. 

Here are a few samples of different commercial engines available for exclusive license. ( for videos see home page)


Single to Multiple Cylinder Steam Engines 


Three to Sixteen Cylinder Steam Engine From Fractional HP to Over 500 HP

Four Cylinder Version   

(runs in any position and is self starting)


Three Cylinder

Two cylinder flex rod engine

Two cylinder Z drive engine

Z8 Engine

Z6 Engine


(May be licensed in all sizes. Powerful and compact)

Three cylinder various sizes


Direct Drive Generators With 2 to 8 Cylinders




Steam Engine, Water Distiller, Space Heater, Water Heater, 500 Watt Generator, and Water Pump in One

(runs on a household pressure cooker or small water tube boiler)

Primary use as emergency and disaster relief power system. System is scalable for larger models.


Large engines may be constructed for hundreds of HP

These engines may be built on a concrete slab with the plumbing imbedded in the slab. The generator may be at the base in the center or placed above the engine on a beam.

Here is a residential combined heat and power system. It provides hot water, space heat and electricity. The unit utilizes existing hot water heater. The heater element in water heater is redundant- adds heat if water temperature is below normal requirements. Boiler water is recycled. Produces 1 to 10 kW output.


Click on the link bellow for a TED talk by Robert Green on replacing the electrical grid.




What are the best reasons to consider steam engines over solar or wind?


The Green Steam Engine® can run 24 hours a day regardless of location, weather or daylight.


There are no construction costs, towers, roof panels or permits required.


There is no noise or environmental impact associated with steam power.


The Green Steam Engine® can run on the widest range of fuels including solar and geothermal energy.


The steam engine does not require a back-up power system that is costly and redundant. Solar and wind does because of variable weather conditions.

Key Benefits

bulletSimple conversion from rotary to reciprocal movement and vice-versa.
bulletMultiple outputs from a single rotary source.
bulletMultiple output with separate timing, amplitude and duration.
bulletInput and output in same linear direction.
bulletExtremely simple structure.
bulletFew and easily constructed parts
bulletLittle or no lubrication requirements
bulletApplications include generators, distillers, boat propulsion, pumps, toy models, to suggest only a few.
bulletEngine may be operated on any fuel including solar, bio-mass, dung, corn and barley, wood, waste heat and unrefined fuels.


    The “Green Steam Engine™” design may be scaled to any size or configuration that suits your requirements. The area of the piston, length of stroke, RPM's, number of cylinders and steam pressure are all variable for the power and speed you wish to obtain. The efficiency of this engine depends on the configuration of the engine and the full extent of the utilization of the steam employed to run it.
    When the steam is simply exhausted to atmosphere while running a generator, for example, efficiency is relatively low; in the area of 15%. When the exhaust is condensed and recycled back to the boiler, the efficiency is around 24% to 30%. When the exhaust is condensed through a heat exchanger whereby the condensation process is used fully by heating water, space and distilling water, for example, the efficiency can be in the 70% range.
    In addition to the potential for efficient energy use and production, the designs' simplicity, economy and weight more than justifies its utilization. It is important to note that utilizing free or cheap fuel makes efficiency less important. There are numerous reasons that this design is considerably more efficient than standard historical steam engines. I will describe the reasons as follows:


   The Flex Rod Mechanism and the "Z" drive that replaces the standard bell crank provides straight-line, intermittent movement that eliminates side forces. Side forces account for most of the friction in the standard steam engine and the need for lubrication of the cylinders and crank mechanism. The Flex Rod Mechanism (FRM) eliminates from steam engines the crosshead, wrist pin and bearing, heavy piston rod and bearing, long and heavy pistons with metal rings, and the piston rod seal at the base of the cylinder. All of these parts are the main source of friction. The piston in this new design can be a thin disk with an "O" ring seal that has very little contact area and is lubricated by steam. Because it is pushed straight in the cylinder, it has very low friction. The piston rod may be a very light rod because all of the force is straight compression on the rod. The rod-ends and the one head bearing in the FRM are sealed bearings requiring only occasional re-lubrication. Only one head bearing is required for as many cylinders that one wishes to use. (1 to 16 cylinders ideally) The engine is modular so multiple cylinders may be arranged in a radial, compact arrangement. No oil is added to the steam that would foul the boiler return feed-water. The exhaust steam may be recycled directly back into the boiler. The process of condensing the exhaust provides useful byproducts such as clean hot water, space heating and distilled water. When the exhaust steam energy is fully utilized, the efficiency of the system can exceed 70%.

    Another reason for higher efficiency is that the cylinders in the Green Steam Engine® are easily insulated to prevent heat loss and can be made from molded insulating material such as glass or high temp carbon fiber. Cylinders do not wear. Only the "O" rings wear. "O" rings require less than two minutes to replace. Old type steam engines lose efficiency through heat sink in the metal castings. Their heavy and bulky structure draws heat away from the steam. This reduces efficiency. Other forms of fluid may be use such as refrigerant for lower heat phase changes.


    The flexible rod mechanism itself has little, if any, friction. As in a spring, the energy used to deflect it is returned. The flexible rod is deflected about 10 to14 degrees over its length. Its purpose is to maintain alignment of the cylinders and prevent rotation of the mechanism and convert reciprocal movement into rotating movement. The deflection of the rod is carried by the head bearing and does not cause friction in the rotation of the output shaft. These flex shafts are designed for continuous flexing at high speed for infinite numbers of cycles. There is never a need for overhaul, oil change or tune-up. Any part on the engine can be replaced in less than five minutes. The engine is designed for continuous operation.

    The arrangement, whereby the cylinders are in the same plane as the main shaft permits large engines to occupy a very small and compact space. Engines can fit in a tube.

    The same movements that operate the pistons, operate the valves in a separate intermittent timing. There is no additional valve actuation mechanism required. The valve opens and closes while the pistons are stopped at top and bottom dead center whereby the valves are fully open throughout the full piston stroke.

    Most of the parts are modular so few dies or molds are required for manufacture. The engine can be assembled in minutes and may even be assembled by the customer.

    In large quantities, the cost to produce this engine could be a very small amount over the weight of the material. The weight to power ratio can be extremely low; the larger the engine the better the ratio.


   This engine is ideal for saturated steam. Saturated steam is easily produced from waste heat, including the exhaust from IC engines. The boiler requirements are minimal because one can use very low-pressure steam yet produce substantial power using large diameter pistons with very short stroke. The ease at which the piston size may be enlarged without creating large, heavy, costly engines, makes this design increasingly attractive and utilitarian. The ability to utilize low-pressure steam to produce considerable power means that many processes that produce waste steam and heat can now recover that lost energy affordably.  

      Due to the crisis over the drawdown of fossil fuels and global warming, the timing is perfect for producing an engine that can use a wide range of fuel and sources of heat to generate power both by conserving and recycling heat as well as utilizing many forms of potentially free energy such as solar, waste heat and bio-mass.


      Unlike internal combustion engines that need high rpm's to develop full power, steam engines have full power at starting speed. Windmill generators operate at low rpm's (100 to 1000 rpm's). Although steam engines can run at high speeds, to do so requires more steam volume than necessary. It is much more economical to run them slowly. For electrical generation, use the same electrical system as you would for windmills. The difference is that the steam engine is not an intermittent energy source. It will run as much or as little as required.

Overview of the Engine and Market


          To issue licenses for manufacture and distribution or assignment of patents for the Patented Green Steam Engine™.


          The following information regarding the “Green Steam Engine”™ is intended to provide details of the structure, workings, unique features, ramifications for present and future use as well as its perceived market potential and targets.


Basic Invention:

    An axial piston fluid engine having single-acting cylinders incorporating swivel-joint attachment of the cylinders to rotary control valves wherein straight-line piston movement is established for the elimination of side forces on the pistons. The pistons and the control valves are operatively connected to a common wobble drive member and arranged in geometry of lever positions to coactively time the drive fluid into and out of the cylinders intermittently.

Invention Applied to Steam Engine:

    Because of the properties provided by this new technology, a steam engine may be constructed that is extremely lightweight, efficient, and economical. They produce virtually no noise and may be operated inside dwellings. Modern methods and materials are used to reinvent the steam engine and bring it into the twenty-first century. Because any combustible fuel as well as solar and geo-thermal heat may be used to operate this engine, it can provide a flexible means of producing power. The engine can operate on very low steam pressure and volume, which reduces boiler requirements for safe domestic operation.


                   The “Green Steam Engine” ® may be scaled to a range of sizes from micro engines to large industrial engines.

Micro engines can operate tiny mechanisms as well as disposable motors used for medical procedures such as bone grinding and drilling. The engine can operate on inert compressed gas for safe and quiet operating room environments. They may also be used to run model aircraft, small drones, robots, model boats, trains, and toys.

Small engines            that produce fractional HP can operate drills, flexible shaft type grinders, small-scale water distillers, cell phone, radio and flashlight chargers, RV and camping water heaters and pumps and electrical generators. This size unit can operate a combined water distiller, battery charger, space heater, and water heater for disaster relief.


Medium engines are ideal for household power generation, automobile charging, air movers and conditioners, heat pumps, water pumps, water distillers, sewage processing, irrigation pumps, greenhouse pumps  and boat engines. This size engine may be used in place of, or back-up for solar and wind systems as off grid generators. 


Larger engines may be used for utility size electrical generators for villages and multi-unit dwellings and water treatment systems. In addition, it can be used to utilize waste heat from industrial processes, large ship and industrial diesel engines. They may be used to increase the efficiency of fossil fuel engines by utilizing the exhaust heat to operate accessories such as generators, water pumps, etc.              


Customer Demographics:

    A worldwide market exists for alternative energy home-power systems that can use a plurality of fuel sources to provide electricity, purified water, space heating, hot water for cooking, bathing and washing, and direct mechanical power to operate tools and equipment. Further, there exists a need for an alternative to costly and undependable solar and wind units that operate only within certain conditions and locations. Charging vehicle batteries is a new application that will become increasingly important.  

    A worldwide market exists as well for a small portable “disaster relief” power system that can operate on a choice of many combustible materials as well as solar thermal energy and geo-thermal energy for electrical power while distilling unclean water, pumping water and producing hot water for washing, cooking, bathing and space heating in one combined unit. 

    A worldwide market exists for recreational power systems for producing electrical generation, distilled water, hot water and space heat for tents and campers.

    A worldwide market exists for waste heat recovery that recycles the heat into useful processes that save money.

    A worldwide market exists for alternative energy production in rural and remote locations that is independent of local weather, wind and solar conditions. Local energy sources may include: natural gas, dung, wood, biomass such as straw and crop waste, corn cobs, rice husks, palm oil debris, bamboo, etc. Gas may be extracted from any of the above wherein the carbon is extracted and used as a soil enhancer, thus sequestering the carbon. Some of the carbon (charcoal) can be used as a cooking fuel.  

    A worldwide market exists for micro engines that operate medical tools, toys, robots, model planes, boats and trains as well as other future hobby mechanisms and educational models. This market has roots in the fascination for steam engines evident on the Internet and in literature.

    A worldwide market exists for an engine to produce electrical and mechanical power as a byproduct from distilling water from sea water, sewage, polluted water, gray water, and brine. 


Cost of Manufacture:

    The projected cost to manufacture the “Green Steam Engine ®" will be very low indeed because there is very little structure and few parts involved. Machining requirements are minimal. The elimination of an engine block, allows the engine to be manufactured in many sizes and configurations without castings or expensive machining. The shipping cost is low because the weight is low. The cost per power ratio is the lowest for any engine that exists.


    Competition is conspicuously absent for the niche that this steam engine fills. Wind, solar, and gas generators have serious deficiencies that have not been addressed. Wind and solar systems are expensive, require large expenditures for installation and often require permits from governmental agencies. They also increase insurance rates, property tax rates and require frequent cleaning, snow removal and inhibit roof repair. Windmills are restricted to rural areas and often are opposed for noise and aesthetic reasons. They frequently kill birds and throw ice. Windmill repair is problematic as well. The pay-back time is lengthy and the longevity is short. Wind and solar are ineffectual on most of the planet. Finally, as we all know, wind is sporadic, and the night is long and clouds are common. Seasonal solar intensity is an additional negative factor.

    Gas and diesel generators require expensive fuel, and are noisy. They require frequent maintenance that need skilled mechanics to repair and they often are hard to start when needed most. The proposed steam engine requires little maintenance, no oil changes, or tune-ups, minor and occasional lubrication and can run 24 hours per day. Maintenance and repair can be done by relatively unskilled local labor with unsophisticated tools. No transmissions are required because steam engines have full power at starting speed. Steam engines are self- starting.


Price Strategy:

    Because the “Green Steam Engine“Green Steam Engine®" would be very economical to manufacture and have short pay-back time, a modest price could produce large sales volume. Making the engine very attractive with a low price could draw customers to buy numerous add-ons and accessories that could be priced to increase profit overall. A basic mid-size engine could start at a suggested price of $499. to $1500. depending on the size.  Added accessories could fill out a complete system that could sell for between $2500. to $10,000. depending on the size. The accessory package could include a generator, a water distiller, an inverter, a battery, a pump, a boiler and a choice of burners that use different fuels. A steam engine electrical generating system is exactly the same as a windmill system, therefore, no new technology needs to be developed for that part of the system. Boilers are very old well established products. However, new, small boilers dedicated to steam engine technology will need enhanced designing and updating. Simple and inexpensive boilers are prolific on U-tube and the internet.

 Basic Invention

    The engines may be produced in sizes ranging from fractional horse power to hundreds of horse power and may be operated on air, steam or volatile fluids including refrigerant and expandable gas. Where heat is used to expand and compress the gas, a Rankin cycle is typically employed to recover and recycle heat and fluid. The efficiency is therefore maximized.  

    Besides the extreme economy of structure, the properties of the "Straight-line Piston Fluid Engine With Wobble Drive Valve Actuation" and the  "Flexible Rod Transmission"  invented by Robert Green, provides this engine with the advantage of eliminating the typical crankshaft and valve mechanisms that require heavy cast parts and precise machining. It also provides the unique configuration whereby the cylinders are aligned in the same direction as the main shaft. The result is a compact, lightweight and slim engine that is extremely simple to construct and assemble.

    This engine is called a "green" steam engine. The reason that it is green is that it runs on renewable fuels such as biomass, solar thermal energy, waste heat from other engines or processes and geothermal heat.  Natural gas is a relatively inexpensive and convenient fuel as well. Because biomass releases carbon into the atmosphere when it decomposes, burning it in a boiler to produce steam power results in less carbon being released. The reason this is so is because some of the carbon is destroyed and the power that is produced replaces power that would otherwise be produced by fossil fuels.

    Burning biomass is considered "carbon neutral". Combustion in a boiler is typically cleaner than burning fuel in an internal combustion engine. The reason is that combustion in a boiler can be controlled much more effectively by injecting proper air flow. When biomass is processed by gasification, the resulting gas (syngas) is not clean enough to use directly in internal combustion engines. It must go through an expensive cleaning process. However, boilers have sufficient oxidation to burn the unclean syngas cleanly. Additionally, when biomass is gasified, the combustible gas is separated from the carbon, yielding gas and charcoal. The charcoal (carbon) can then be mixed into soil where it becomes a soil enhancer that reduces the need for fertilizer. It also sequesters the carbon from the atmosphere; a win-win result. 

    Gasifying  fuels such as farm waste (corn cobs, stalks, rice husks, wood etc) and, or a fast growing plant like bamboo, one is essentially creating energy without the carbon burden. In fact it is solar energy that is being utilized. The difference is that using this syngas to run a steam engine, one can utilize the energy 24/7 rather than only when the sun shines with weather and location permitting.        

      Another reason it is "green" is that in addition to the rotary power that is produced to do useful work, usable byproducts may be generated at no extra cost. These products are hot water, air cooling, distilled water, and space heat. Even the exhaust heat and water from the engine may be recycled back to the boiler to add efficiency. This recycling of the heat and water is called a Rankin cycle.

     The "Green Steam Engine "Green Steam Engine®"   is an axial piston fluid engine with a straight-line piston movement. It uses a wobble-drive with a variable number of articulating cylinders positioned radially with all the cylinders facing in the same direction around a center.  The result is a very compact engine wherein the larger the engine, the greater the power to weight ratio. Because the engine has straight-line movement, it can operate with "O" ring piston seals with light-weight disks for pistons and light-weight piston rods. The low reciprocal mass that results greatly reduces friction and power loss.

    Another result of the straight-line movement is that the steam is the only lubricant required in the cylinders. No oil needs to be added to the steam as in the old type engines. The exhaust can be condensed into distilled water. The elimination of an engine block reduces heat loss that robs the expansion of the steam and the power. It also significantly reduces its manufacturing cost. The engine may be scaled to any size and contains very few parts that cost very little to produce.

    The engine is designed to run continuously with only occasional maintenance. Unlike windmills and solar panels, maintenance is simple, on the ground, and easily done in a few minutes by low-skilled persons. 

    The final result is a highly efficient, low cost prime mover with multifunctional applications and a very wide selection of fuels- many of which are unrefined, free and readily available throughout every continent world-wide.


Summary of Advantages and Market Potential

    Recent awareness of the pending energy crisis has been illuminated by rapidly rising prices in the energy sector. People in all parts of the world, including developed nations are looking for ways to cut energy costs and find alternative ways of supplying their energy needs. A portable, inexpensive power supply that can operate on fuel as diverse as cattle dung and solar collectors is a niche market with increasingly high potential.

    Further, disasters such as hurricanes, floods, earthquakes and storms have shown how vulnerable the electrical grid, water supply and rescue systems can be. Even though there is often ample supply of combustible material available, there is no means to convert the heat into a usable resource. In cold climates, pumping hot water through a small radiator may provide space heating from an outside campfire.

    Emergency equipment such as cell phones, radios and battery-powered lights soon give out and there is no way to recharge the batteries. Potable water is soon exhausted as well. An electrical generating system that can operate from any heat source and produce potable water and pumped hot water as a byproduct has an intrinsic value in its own league.

    An engine that can run on trash will not want for customers. Many industries produce waste heat and, or waste combustibles that could reduce their energy costs substantially. If they were able to convert the waste to rotary motion, they could easily be convinced of the benefit. Large units may be developed for this market. As the cost of energy increases, the generation of customers will increase exponentially.

    Farms could benefit from an engine that could aerate ponds and manure storage tanks as well as run air movers for barn ventilation. These engines can operate on animal waste. 

    The recreational market is another important customer. Small units that are nearly silent running can operate boats, without the pollution and noise associated with traditional engines. The recreational vehicle and camping industry could well be a major market- providing battery charging, potable water, hot water for washing and space heating for tents and vehicles. Pumped hot water through a small radiator in the tent or camper can provide heat without the danger of fumes. In addition, it should not be ignored that there is a great romantic affection for steam engines historically. A survey of key words “steam engine” on Internet search engines will convince any skeptic as well as point to some of the additional markets not covered here.

    Future development could add home power generators that attach to existing home heating units. A small heat exchanger attached to the heating unit could produce the steam to drive a generator without any additional energy spent. Because the engine units are nearly silent running, they could be placed on or next to the heater. These engines could run heat pumps that could provide air conditioning as well. Microprocessors could easily control all aspects of this system. All the heat that is used for the generator is returned to the space heating. The market for such a system is huge.

    Thousands of documented requests for purchases have been received including many requests from Non-Governmental Organizations  (NGO's) specializing in community assistance and energy solutions.

    Proof that there is substantial interest in the Green Steam Engine™ can be seen by the position of the web site, www.greensteamengine.com  on the most popular search engines. By placing the search words: "steam engines" in the browser, you will see that this site is at the top or close to the top of the first page. Google has over 5,000,000 results for that search request. www.greensteamengine.com is number one on the list.  

 Investment and License Opportunity

    Our goal is to license or assign the patents to a company or companies to manufacture and market the "Green Steam Engine®". The owner of the patents is retired, in good health and is available for consulting and contributing know-how. Photos and additional information is available on the web site: www.greensteamengine.com        

    Engines are covered by US patent # 6647813 (Green, 2003) and Patent # 8096787. PCT filed 06/19/2009, Chinese Patent #CN 101910561(2010), Indian patent 02/2011. Patents are available in other countries and may be requested with Licenses for a limited time.

Contact Information

Robert Green  2337 B Avenida Sevilla, Laguna Woods, CA  92637  (949) 581 2529


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