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The Solar Powered Steam Car

May 24, 2009 Solar-Thermal Hybrid Vehicle 2 Comments

The Solar Powered Steam Car

Reprinted from Volume 23, #3 of The Steam Automobile
(Fall, 1981 issue, pages 32-36)

Editor’s Note: this submission came to the Automotive Tribune from Peter Brow who had originally posted the article on on his site.   Peter had spotted an article in the Steam Automobile Club of America from 1981 and had found significant interest and some of the commentary is included here.  Additional information about the Solar-Thermal Hybrid Vehicle is included at this link for the Automotive Tribune.  In our archives we have a copy of this particular 1981 SACA magazine which were unable to locate to add a photograph of the magazine cover and for possible inclusion of graphics and artwork that would be relevant to the reader.


Note: Peter Brow’s updated comments following this article, below.

[1-30-2001]

 


Introduction:

Here is a very interesting article on a technology which I think holds great promise for the future. Imagine a future where all cars are powered directly by solar energy without toxic electric batteries or gaseous emissions. I believe the heat-battery steam car technology described in the following article can be developed to where solar steam cars are quickly refueled by draining cooled “thermal liquid” out of onboard tanks and pumping in hot “thermal liquid” heated at desert solar-collector farms. The hot thermal liquid pumped into the car’s tanks generates steam, which runs a steam engine, which propels the car. The cool liquid is shipped back to the solar farms for reheating, and hot liquid is transported from solar farms to distant cities, especially those in less-sunny areas, via insulated pipelines or insulated road or rail tankers.

Due to the simplicity of the equipment and the low cost of the materials, I think nonpolluting solar cars like these could run at a lower overall cost per mile (purchase, maintenance, and energy) than cars powered by fossil fuels, electric batteries, fuel cells, etc.. My calculations indicate that the range of these solar cars could be economically extended to about 200 miles with extra solar heat-tank capacity.

Homes could be heated by pipelined solar “thermal liquid” too, and small steam-powered generators at each home could provide all electrical service.

So we may someday have a world whose energy not only comes entirely from the sun, but where energy is both cleaner and cheaper too!

Check out the following article, and see what you think. Eventually I will try to scan the pictures from the article, and include them on this page.

 


On-board “thermal battery” can be charged by parabolic reflector to provide boiler heat for steam-driven experimental car. Widespread application of propulsion concept could result in sizeable energy savings.

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With a hiss and a burst of steam, the solar-powered test car jumped to life. I drove a short distance, eased to a stop, checked the steam-pressure and thermal-battery temperature gauges, shifted into reverse and returned. The car had moved smoothly with surprising power, and solely by heat energy stored on board.

An intriguing contrivance — a 1977 Vega wagon stripped of its engine, transmission, and drive shaft, and refitted with a 1915 Stanley engine, a monotube flash boiler and a 700 lb thermal battery — the experimental car effectively demonstrated the feasibility of using solar energy for vehicular propulsion. The thermal battery, a unique heat sink and the key element in the design, contains a stable, high-temperature, heat-storage material that can be charged (heated) by a high-temperature solar concentrator, such as a parabolic reflector (for convenience a small oil burner charges the thermal battery during testing). Water pumped through the monotube boiler, which is submerged in the heat-storage material, produces steam to run the engine.

Designed and fabricated by Dr. Robert C. McElroy, president of the American Solar Energy Corp., Arlington, VA, the research vehicle has a theoretical range of about 35 miles at 55 mph on a single thermal-battery charge (roughly three hours with a 16-foot parabolic reflector in normal sunlight). A production solar-powered car, built specifically for solar propulsion, would probably stretch that range to 80 miles or so, easily more than most Americans drive in a single day.

The solar-powered test car represents a basic, straightforward propulsion concept, one with the potential to reduce petroleum fuel consumption considerably.

400 lb of BTU’S

Capturing the energy collected by a high-heat solar concentrator, such as a parabolic reflector, for use in a mobile application, is made possible by the heat-storage material in McElroy’s patented thermal battery. The stable, tar-like, refinery by-product, trademarked Thermal Liquid, can be heated to upwards of 1000°F without igniting, degrading, or creating high pressure.

Characterized by high density and high specific heat, Thermal Liquid absorbs and stores a large number of Btu’s in a relatively small volume, maximizing the storage container surface area, and thus minimizing area to be covered by insulation against heat loss, and increasing portability. The Thermal Liquid composition in the test Vega has an auto ignition point of 620°F (in oxygen), but chemists have advised McElroy that certain modifiers will raise the auto ignition point to 1000°F or more. The material freezes at about 200°F.

Though Thermal Liquid performs satisfactorily and is readily available and reasonably priced, McElroy continues to assess other possible storage media, including synthetic lubricants, to improve heat-storage efficiency. Phase-change salts offer some of the properties desired, but are considered too corrosive.

Sun-charged battery

Major components in the solar-power test vehicle include the thermal battery (with monotube flash boiler), feed water pump and engine. The Thermal Liquid and the monotube boiler are contained in a rigid, 275-lb, 1/4-inch steel tank positioned behind the four seats in the area normally occupied by the back seats and luggage. (The area available for the tank dictated the size of the storage battery — and likewise the estimated range.) To install the tank, McElroy ripped out the floor and the front and back seats and replaced the floor with aluminum (diamond tread), and the front seats with light bucket seats.

The tank is insulated by Cer-Wool, a high R-

[some of the article seems to have been accidentally omitted from The Steam Automobile at this point. Sorry folks, not my fault — Peter]

sulation holds ambient battery losses to about 60°F per day from 600°F plus.

A parabolic reflector would charge the thermal battery in a truly solar-powered configuration, but the reflector is considered a proven component and has not been used in testing. The reflector would be stationary, perhaps mounted beside the driveway or on top of the garage (or used in conjunction with residential heating/cooling equipment), with a quick-disconnect optical universal connecting the reflector to the thermal battery. Solar energy reflected by the reflector face to a secondary receiver above the reflector would be transferred through the optical universal to a target plate in the thermal battery.

The 400 lb of Thermal Liquid in the thermal battery contains about 200,000 usable Btus, figuring a 375°F to 620°F working-temperature range. A 16 foot parabolic reflector, with 80% efficiency, could net a conservative 60,000 Btu/hour, considering system losses, and could recharge the battery in a little better than three hours. (Geographical location, of course, has an impact on charging time and the size of the parabolic reflector.)

The back-up heat source, which has been charging the thermal battery exclusively during tests, consists of a simple, high-efficiency oil burner, installed in a tube leading into the thermal battery. Roughly equivalent to a 16 foot parabolic reflector, the burner recoups one day’s ambient heat loss in about 1 hour.

An expansion area at the top of the thermal battery accomodates the expansion and contraction of the Thermal Liquid as it is heated and cooled. To keep the storage material from combining with oxygen, which would promote degradation, the expansion area is charged with a couple pounds of nitrogen.

The flash boiler, submerged in the Thermal Liquid in the thermal battery, connects to the feedwater line at the top of the tank. (McElroy installed a removable panel in the roof to expose the connection). To keep steam in the boiler from backing up into the feedwater line, causing a vapor lock, the feedwater line connects first to an aluminum fitting — a thermal barrier — then to a steam check valve before meeting the stainless steel boiler.

The heat energy stored in the thermal battery has been satisfactory for the steam quantity and pressure required, but the monotube boiler is unable to keep up under high demand conditions. As a result, McElroy will replace the existing boiler by a boiler with a one gallon reservoir inside the thermal battery, an engineering change that should alleviate the low-steam problem.

$50 per hp

McElroy contacted a number of steam car owners before finding a steam enthusiast in Pennsylvania willing to part with an applicable engine, a 20 HP, 2 cylinder Stanley engine. Ironically, McElroy paid $1000 for the steam engine, manufactured in about 1915, but recovered only $125 when he sold the engine from the four year old Vega.

Steam engines, which are noted for simplicity and low parts count (21 moving parts in this engine), provide high torque at low speeds and do not require gearing to accomodate low-speed operation. Because steam is injected into one end of each cylinder each stroke (exhausted at the opposite end), with intake and exhaust valves reversed for the return stroke, a two cylinder steam engine has four power strokes per revolution. The Stanley powering the test car turns 773 revolutions per mile, in effect 3092 power strokes per mile.

The Stanley hangs under the car, between the rear axle and the rear bumper. (Integrating the steam engine to the Vega required as much dexterity with a torch as familiarity with automotive design.) Because the engine is built on four lag screws that pass through the axle housing, McElroy had to cut and weld the housing extensively. In addition, he was forced to grind out the housing to accomodate an 8 inch industrial flat-cut gear that had been hollowed to fit over the stock Vega carrier. A sheet metal cover (not installed during my test drive), holds oil for splash lubrication.

A small, 1/2-ton truck frame was substituted for the stock rear end to handle the weight of the Stanley and the thermal battery. The springs in the rear, however, are not adequate and McElroy has wedged a block of wood between the floor and springs to keep the suspension from bottoming until heavier springs can be installed. (Even with the added load in the rear, the Vega weighs approximately 400 lb less than delivery weight.)

To provide lubrication for the cylinders, McElroy chose a Detroit lubricator — an antique, but still rugged, reliable, and easily metered. Similar to lubricators found in later Stanleys, the pump squirts 600 weight cylinder oil into the engine each revolution (squirt being a stretch of the imagination). The pump runs so slowly that it took 3000 oscillations to move oil from the pump, mounted on the floor between the seats and the thermal battery, to the engine when the lubricator was installed.

The engine turns over at 100 psi, runs quite adequately at 200 psi, and is red lined at 600 psi; for my test drive we charged it to 375 psi. A floor mounted lever controls direction — forward or reverse — and variable valve timing (the length of time steam is injected in each stroke, an efficiency boosting economizer).

Priming and condensing

Once the Stanley is running, a power takeoff from the engine drives a water pump (an 800 psi high-pressure car wash water pump in the Vega), assuring an adequate supply of feedwater. Getting started, however, requires a primer pump to jack up the steam pressure.

McElroy installed two primer pumps, in the test car, one hand-operated, the other driven electrically. The electrical pump, jerry-rigged to a 3/8 inch Black and Decker drill in a fixed position under the hood, has not performed as intended due to an inverter problem. At present, McElroy uses the drill only for static tests, since he must plug it into a wall socket.

The hand-operated primer pump, infinitely more interesting, is an authentic Stanley brass pump, designed a good 75 years ago. Mounted on the floor between the seats, about where a gearshift might be positioned, the pump can achieve 1000 psi or better.

At present, exhaust steam flows through a feed-water preheater, an oil trap, then is exhausted. Though a condenser is important — and though McElroy has experimented with a couple of designs — it is not a mojor thrust in this demonstration because a production solar powered car would not use water as a working fluid, eliminating the problem of separating heavy lubricant from steam.

Solar powered car in production

McElroy does not intend to develop this particular design much further. Beyond installing the new boiler with the one gallon reservoir and making some full range road tests, the car will see few other refinements.

The next step involves applying the lessons of this proof-of-concept demonstration to a true solar powered prototype, built from the ground up. In a production solar-power-car-design, for example, the thermal battery might contain a heat storage material with higher temperature capability, higher specific heat and higher density, to increase the number of useable Btu’s stored in a given volume.

Also, the thermal battery in a production car would be reconfigured for safety. McElroy suggests putting the well insulated battery inside the rectangle formed by the automobile frame, secured with shock absorber mounts. In a collision, the mounts and insulation would damp the tank movement, while the frame would physically protect it. Attaching the passenger compartment to the battery, McElroy adds, could afford the passenger compartment the same shock absorption and cushioning given the thermal battery.

The engine in a modern solar power vehicle using McElroy’s thermal battery would not be steam powered at all, but would use a low boiling point medium, such as Freon. In addition, the engine would have smaller bores, longer strokes and probably more than two cylinders, and would be designed for more complete expansion of the working fluid (or optimized variable valve timing) aiming for phase change at the end of the stroke. Engine efficiency in a production model might still be comparatively low, but it remains that the engine will operate only on demand (i.e., not when the car is stopped in stop-and-go traffic, or at traffic lights), and it will operate on an energy source that is renewable and, in a sense, free.

Sizing and citing [sic] parabolic reflectors is another application detail, but not insurmountable. Available sun in a particular locale, of course, will determine size of parabolic reflector and length of charge. To accomodate commuter cars, cars driven to the train station, cars not at home during the day (where a reflector most commonly would be), employers and municipalities might erect parabolic reflectors in parking lots, charging stations paid for by the hour. Going a step further, collapsible reflectors could be designed — reflectors folded on the top of a car that the driver could pop open to charge the thermal battery while the car is parked.

McElroy recognizes the innate inconvenience of being tethered to a parabolic reflector, and even now is working on a solar car design with selfcontained charging components. He envisions concentrating lenses built into the body of the car, lenses that would provide energy for a flash boiler or charge the thermal battery, depending on the need, whenever the car is in the sun, driven or parked. Ultimately, he projects, an integrated solar powered car could be driven nearly nonstop on a sunny day without using backup energy sources.

A concept stalled?

Plugging into a backyard parabolic reflector may not be every driver’s idea of convenience, but given the outlook for fuel availability and cost, that prospect will be less odious as time goes on. McElroy estimates that a four-seat, compact solar car could be manufactured in production for close to the cost of a conventional compact car, less the parabolic reflector. He also estimates that such a car could be on the road in the next decade — if research continues.

The climate for funding for this type of venture has grown foul in recent years, and shows no sign of improving. Both government and industry in this country, for a multitude of reasons, have cut spending on numerous promising energy-saving ideas, flywheel propulsion and continually variable transmissions being two excellent examples. Whether the concept demonstrated by McElroy is investigated further to determine its true potential, or whether the red, white, and blue Vega with the NOGAS license plate remains parked in a driveway in Alington, VA, remains to be seen.

[End of article]

 


Some Comments On This Article

It is too bad that this concept was not further developed or researched. But this is a typical result with R&D projects structured around government or corporate research grants. I believe that to succeed, alternative-energy projects have to be structured as independent, private, productive, for-profit start-up enterprises, and completely focused on delivering major cost, convenience, and other advantages directly to consumers on schedule.

I have some ideas for making a solar heat-battery car a lot more practical and convenient. First of all, the idea of using Freon or other low-boiling-point liquids and vapors in the boiler, has serious problems. The pump horsepower losses with such liquids are very high, the fluids tend to break down with time, the powerplant is larger and heavier for a given power output, and leaks in the system can be toxic, expensive, and a hassle to replace. Many good articles have been written on the subject of alternatives to water as working fluids in vapor-expander powerplants, and most of the articles I have seen have concluded that water and steam are the best vapor-cycle working fluids known. This subject is much too complex to get into here; see Jerry People’s excellent article “The Secret Fluid”, and others, in back issues of The Steam Automobile. I will look up the reference and include it in this space in the near future; back issues of TSA, and an index to them, are available from the Steam Automobile Club of America, listed in the links page elsewhere on this website.

Also, as should be obvious, McElroy’s car was a very simplified low-budget test vehicle. A production solar steam car would have completely automatic controls for the water pumps. Get in, turn the key, and drive. As with the fuel-burning steam car I am working on, everything would be automatic, and with much simpler equipment too. The driver merely operates the steering wheel, brake, and accelerator pedals, plus of course a reverse lever when backing up. The car would run with absolute smoothness and silence, and with legendary steam car acceleration as well.

There are nearly endless possibilities for the size, shape, mounting, materials, and design of a heat battery, not to mention for the heat exchangers and reheating/recharging methods. McElroy’s system is only one of many possibilities.

Personally, I think it would be most economical to have specialized commercial facilities for collecting the solar heat, many perhaps far removed from the places where the heat is used. Many areas have very little solar energy available for much of the year, while others, particularly the vast arid wastelands and deserts of our planet, receive vast amounts of solar radiation year-round. I think a successful solar-battery energy system would collect the heat in one place and transport a heated medium to the point of use. This could be done with hot solar liquids transported through insulated pipelines or in insulated tanker trains or tanker trucks. The heated liquid would either be put directly into a vehicle heat battery, or perhaps circulated through the steam-generating tubes inside the heat battery, to reheat it.

And, of course, the cooled liquid or other medium would be returned to the solar collectors for reheating.

For safety, it might be desireable to make a heat battery as a series of small modules which would not release the heat-storage material in a collision, even in the most severe high-speed collisions. It might also be desireable to use a thicker liquid, or even a solid, which would not flow, or at least would not flow far, if accidentally released. On the other hand, a rugged enough tank, perhaps spherical in shape and with its insulation serving also as an impact-absorbing barrier, could be devised to safely contain even a thin liquid.

It is also possible to design solar steam cars with quick-change modular heat batteries. This has been proposed many times for electric cars. I think it could work well with heat-battery solar steam cars. You drive up to a recharging station, park in a certain place, and your power cells are replaced by an automatic machine of some type, either from one end of the car, or by opening the hood and lifting batteries in and out, or perhaps by lowering/raising batteries through the bottom of the car on a special floor jack. The method would be standardized. The heat batteries would be modules of standard size and shape, perhaps relatively small, with standard connections. The number of heat batteries to replace would vary from car to car depending on the size and range of the vehicle, and the battery-changing machine would automatically detect how many modules to remove, replace, and charge you for. This would be the fastest recharge method of all, even with thin, fast-flowing thermal liquid, and would be preferable for heat batteries with a solid or thick liquid storage medium. If completely automated, you could recharge your solar steam car faster than filling the tank of the car you drive today.

Water refill would be automated too. You could sit in your driver’s seat during the whole operation, which might only take 60 seconds. In fact, the unmatched convenience of such a car might be its greatest attraction!

Size Of Solar Steam Cars

The size and weight of a solar steam car would be its biggest problem. However, I think it is entirely a problem of perception, not of economic or technical feasibility.

Today, many people view large vehicles as inherently wasteful or undesireable. But if a solar heat battery steam system could be made cheaper overall than polluting fossil fuels, it would be not only acceptable but very desireable to build larger cars, in fact much larger cars, so that larger heat batteries can be carried to give greater range and convenience.

The problem is changing people’s thinking about the size of cars, so that larger cars are acceptable.

People would have to keep this in mind: if the energy is completely renewable, low-cost, and completely non-polluting, then a bigger, heavier car does not deplete energy resources, waste extra money, or increase pollution of the environment.

How big might a solar steam car be? Even if we could not do better than the size and weight of McElroy’s heat batteries, we could still give a car 200 miles or more range by simply making the car bigger and giving it bigger heat batteries. McElroy got 30 miles out of a 700 lb. heat battery. Thus witha5,000 lb heat battery and small energy density improvements, 200 miles range would be possible. With modern materials, the total weight of the car would be up to 8,000 lbs.. This is very large by today’s standards, but there is at least one SUV on the market today in that weight range, and like most SUVs and other large vehicles, these are commonly driven with one person on board.

Such a car could be built much lower to the ground than an SUV if desired, its size and shape perhaps similar to one of the larger American sedans of the 1950s or 1960s. This would not “look environmental” by today’s standards, but this is simply a matter of getting over the automatic revulsion to large cars which has been programmed into us since the 1970s, in reaction against the excessive pollution and energy waste of the internal combustion era. Yes, at first glance the solar steam car might look like a giant, smog-belching gas guzzler, but in reality it is absolutely non-polluting and runs on completely renewable energy!

Now, the above example assumes that McElroy’s super-low-budget, highly non-optimized 1970s-technology backyard proof-of-concept project cannot be improved upon. That is an extremely conservative assumption. In fact, from my studies of heat-transfer media, I think substantial improvements in energy density can be achieved, so that compared to the above example, the 200-mile solar car could weigh 3,000 lbs less (total weight, 5,000 lbs, same as most large pickup trucks & sport-utility vehicles) and be several feet shorter in length and visual impact. Or, the size and weight of the above example can be kept, and the car’s range extended to 300-400 miles, for those who like long-range driving.

 


UPDATE — Tuesday, January 30th, 2001:

I have done some more study of this concept, and have sketched a concept vehicle which uses an inexpensive liquid oil of indefinite service life instead of a phase-change medium for storing solar heat. A luxurious 6-passenger 4-door sedan with such a powerplant would have a spacious trunk, would weigh just under 5,000 lbs, and would have a driving range of over 200 miles. Vehicle size would be barely more than that of a large American sedan of the 1950s — think 1956 Chevy, but with futuristic styling and features. The “heat tanks” would be quickly drained of cooled oil and refilled with hot oil in about the same time required to fill a conventional gas or diesel car. Tank shape/location and 50/50 f/r weight distribution of the heavy hot oil have been worked out, and a filling of oil would stay useablyhotfor up to a month. Cost of powerplant would be even lower than the fuel-burning steam car I am currently working on, and it would be much simpler. I also believe that a production version of this vehicle would be better-performing and safer in a crash than today’s gasoline powered cars.

I now estimate that the total per-mile vehicle cost, including solar heating and long-range distribution of oil, would be equivalent to driving a smaller modern car fueled by US$1.00 a gallon gasoline. In the 1950-1973 era, Detroit showed that large, heavy vehicles can be mass-produced for very affordable prices, and current experience with SUV’s shows similar results. Two desireable side effects of the high vehicle weight are that the ride and stability would be excellent. I have plans for test equipment to verify the workability of this affordable, silent, zero-emissions powerplant concept, though this idea is still “on the back burner” as work proceeds on the fuel-burning steam car.

 


In reality, everybody wants and needs different cars, so in a future world of solar steam cars, there would be at least as big a variety of vehicles as we have today. The main difference would be that solar steam cars, on average, would be larger and heavier than today’s cars for a given payload and driving range. If the result is reduced cost, zero pollution, and eternally renewable domestic energy supplies, then I think bigger cars are more than worth it, and I think almost everyone would quickly accept them.

This is an idea I plan to work on. With the environmental and energy concerns facing the world today, I think it has great potential.

Is there a solar-powered steam car in your future? Let’s hope so!

 

–Peter Brow

Currently there are "2 comments" on this Article:

  1. socpiter says:

    Cars which work on electricity becomes all more and more. They our future and will change our picture of cars.

  2. Rebekah says:

    I am fascinated by the idea of a true solar thermal car that would be independent of the grid. Someone is building one with parabolic mirrors on a trailer pulled behind it. Pretty bulky. But what if you used some kind of Fresnel lens on top of the car to concentrate sunlight and could charge the thermal batteries as you drive and park, or even provide heat directly to the engine from the sun? If it was programmed as cleverly as today’s hybrids, it could automatically switch between heat sources. With an electrical battery and generator and a backup source of heat such as propane, it could be something truly world-changing

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