SOLAR STIRLING ENGINE SYSTEMS FOR ENERGY INDEPENDENCE

SOLAR STIRLING ENGINE SYSTEMS FOR ENERGY INDEPENDENCE
BY FRANCIS C W FUNG, PH.D.

Exactly two decades and four years ago I delivered a key note speech at the Second International Conference of Stirling Engines in Shanghai, China. The title of my speech was “The Promising Future of Stirling Engines in China”. At the time, I was General partner of the US Stirling Engine R and D Partnership (STRD Partnership) and a visiting consultant to Institute of Thermophysics, Chinese Academy of Sciences. In my speech, I announced the technology transfer of Stirling Engine technology from US Mechanical Technology Inc. to China, arranged by the US STRD Partnership. For reference, see the attached titled pages of the Stirling Engine Conference and the Agreement between Shanghai Marine Diesel Engine Research Institute (SMDERI) and STRD Partnership.

In the lapse of two decades great strides have been made by the world engineering communities in the applications of Stirling Engines, which variously has been also called hot gas engines or external heat engines. The last name is to distinguish it from the well known internal combustion engine. It can be said Stirling Engines now can be found working under Deep Ocean to the earth surface and out to space. Because its mechanical power is derived from external heating, its use of fuel is unlimited in form or source. Of particular interest we can mention solar heat, fossil fuels, nuclear fuel, waste and all forms of indigenous heat. Last but not least, one day we may find implanted nuclear isotope Stirling Engines in human bodies powering artificial hearts without the need for refueling or recharging.

The most endearing and commanding source of external heat to power Stirling Engines without doubt is solar heat. With solar heat as available power because of the simplicity of the Stirling Engine operating principle compared to the conventional internal combustion engine this is a winning combination from ecological and renewable energy considerations. In this application, the Stirling Engines can be miniaturized, sans intake and exhaust valves and cost minimized without the need for injection carburetion and ignition systems compared to internal combustion engines. The operating gas in a Stirling Engine is hermetically sealed and heat is added to the outside of the engine cylinder. In a solar powered Stirling Engine there is absolutely no need for intake and exhaust valves as in conventional internal combustion engines. Thus mechanically high efficiency Stirling Engines are still very simple. Most of all, because of its high heat and power concentration capability it is also particularly suitable for large electric utility applications compared to solar voltaic panels.

As of this writing, the two largest Solar power Stirling Engine Utility Plants under construction are the Solar One Project being built for Southern California Edison at the California Mohave desert and the Solar Two Project being built for San Diego Gas and Electric at Imperial County at Southern California. Following are descriptions and designed power capacities of the two projects.

SOLAR ONE PROJECT, Capacity: 500 MW (for 300,000 homes) with expansion option to 850 MW
20,000 - 34,000 solar dish Stirling systems
20-Year Power Purchase Agreement
Sited in the Mojave Desert east of Barstow, CA
The Solar One project site is located in San Bernardino County in an undeveloped area of the Mojave Desert.
SOLAR TWO PROJECT, Capacity: 300 MW with expansion options to 900 MW
12,000 - 36,000 solar dish Stirling systems
20-Year Power Purchase Agreement
Sited in the Imperial Valley near El Centro, CA
The project site for Solar Two is located in Imperial County in Southern California.

The first 500 MW phase of Project One is planned to go into service by the end of 2009. Once in service, this will become the largest solar powered utility plant in the world. The question is then, how well does large Solar powered Stirling Engine utility plant stacks up against the current technology of both renewable and conventional fueled utility plants? The answer is a resounding “very well indeed”. Otherwise Southern California Edison and San Diego Gas and Electric as experienced utility plant owners as they are, will not rush head long into these two huge projects. Without becoming an insider of the two projects, one can still easily arrived at their choices at today’s oil price hovering at US$ 150 a barrel. Here is my take on how their overview rational reasoning may go like as explained in the following.

First and foremost, the solar Stirling Engine technology being used in these two projects are called the SES SunCatcher system, they hold the record for the most efficient solar electricity generation technology in the world. The SES SunCatcher is a highly concentrating solar thermal technology that converts sunlight into electricity at a rate of 31.25 percent, significantly more efficient than its closest competitor by far. Each SunCatcher dish is 38 feet tall, 40 feet wide and generates 25,000 watts of power, which means they occupy much less space compared to any solar voltaic panels power to power. The large space required for solar voltaic panels, high price and low 10% efficient, disqualified them as candidates for large utilities in competing with solar Stirling Engine. A check of the largest solar voltaic panel utility planned by these utilities, uncovered a plan for 80 MW to supply electricity for 50,000 homes. This planed design is only one tenth in capacity of Project One or Project Two. Project One and Two when go into full service will provide 1750 MW electricity total for 930,000 homes. These each of these Stirling Engine utility plant is thus 10 times larger than the largest photo voltaic plants planned by the same utility owners. This large capacity is equivalent to two large size Nuclear Power Plants. Since we are now at the range of Nuclear Power plant utilities, let us compare nuclear and solar Stirling Engine power plants.

Because of the strict need and regulation requirements to prevent nuclear radioactivity leaks, all nuclear power plants must be housed in fortified containment housing. All systems of hot and cooling water circulations must be heavily protected. So the cost of nuclear power plants is manifolds higher than equivalent fossil fuel power plants. The construction cycle is also unduly long. Despite all the built in safety factors for nuclear power plants, mechanical failures and human errors do occur. Accidents like Three Mile Island in the US and Chernobyl in Russia are unavoidable and the consequences are too dear to accept. The need for more electricity in China is expected. Currently the per capital consumption of electricity in China is less than one tenth of the US. What if the China per capita consumption eventually catches up with the US?

For sheer amount of enormous energy needed for electricity generation , Solar Stirling Engine System utility wins hands down over nuclear and other renewable energy choices in China and other large countries. California has voted for Stirling Engines and moving ahead. China should not wait either. Since Three Mile Island accident, for over thirty years, the US has consistently delayed building nuclear power plants. That is to be commended. Large countries like US, Brazil, China with enormous solar power availability have little need for nuclear power plants. Formidable Cost and even the most remote possibility of nuclear melt down, makes the good ahead of 30 more nuclear power plants in China unthinkable and irresponsible. I was one time the China country representative of Combustion Engineering for the sales of moth-balled Tennessee Valley Nuclear power plants ( See attached pages of my contract with CE). The nightmares of TMI and Chernobyl still haunt me. After the unprecedented severe Sichaun earth quakes, the construction of huge hydro power plants such as the three Gorges anywhere in the world will be most likely put off for a long time if not forever.

China is rich in hydropower resources. Its use will continue, but extra ecological consideration must be exercised to reduce harm to marine life. For enhanced environmentally friendly hydropower applications, I recommend my patented hydraulic air compressor electric generator technology for indirect, small scale use of hydro power. In my invention applications, water is only diverted through the air entrainment unit and does not go through the generator turbines, so marine life is not harmed, and the water is aerated but not heated. Thus the tail water of my invention is oxygenated for improved fish farming and cleaner and richer irrigation.

With concerns over nuclear power plants and other large renewable energy electric generation technologies less competitive from the consideration of cost, efficiency and space requirement, we again is left with Solar Stirling Engine as the commanding choice. There are too many regions in China and the world where sunshine and space are ample, such as Western, South Western, Northern China, US, Brazil and the Middle East to name a few. Even in indigenous hilly areas all over the world, the compact Stirling Engine System of 25 KW each, has a big market in the form of appropriate energy technology using solar, and available fuel and waste heat. This was detailed in my aforementioned paper “The Promising Future of Stirling Engines in China” delivered 24 years ago at the Second International Stirling Engine Conference. The application of Stirling Engine Systems in China is unlimited, renewable or conventional heat, large and small, urban and rural, in the prairies and the valleys, in the flatlands or the mountains the word “Promising” is still most appropriate for Stirling Engines future in China.

China is also rich in coal. She has one of the largest reserves in the world. But coal miners pay a high price with their life. Increasingly high rate of accidents will become more and more unacceptable to the society. The only conscientious regulation is to increase protection of the miners. This will of course increase the cost of coal mining. Assuming that the Chinese government can maintain a harmonious balance between safety and coal mining, the transportation and other pollution problems of using coal as a large source of fuel still abound. Let us now make a rational overview assessment of coal and solar energy for electricity generation. Solar energy as employed by Stirling Engine Systems is direct, simple, clean and absolutely no pollution, as well as its outstanding free and renewable merits. It is befitting to say “The best things in life are free”. Sunshine is the most beloved.

As a source of energy for electricity generation there are two ways to use coal. One is direct burning in conventional furnace or fluidized bed for more complete combustion. The other is to liquefy or gasify coal for example. Either way, the coal must still be scrubbed and cleaned and the treatment of the cleaning fluid remains always a problem in disposal. This will increase the cost tremendously and the cleaning and scrubbing continues in the conversion process. On course, not to mention, we are only postponing the CO2 pollution emission to a later stage.

Aside from the fact that Solar Stirling Engine for electricity generation is non polluting and renewable, the final merit is the economic pay back of its low life cycle cost due to ease of maintenance of the engine. Solar Stirling Engine systems do not require the many additional ancillary accessories as diesel and steam engines. In a Solar Stirling Engine System the working fluid is permanent and hermetically sealed. There is on replacement or treatment necessary in the life cycle of the engine. In the case of steam engine boiler and the combustion chamber of the internal combustion diesel engine constant maintenance and treatment of boiler and combustion chamber increases greatly the cost of operation. Of course, both steam engine with boilers and diesel engines pollute through their exhaust systems as well known.

In conclusion, as a national and local policy to become more energy independent, to reduce environmental pollution, to practice conservation and to reduce cost of operation all points to the choice of using Solar Stirling Engine Systems as the most viable solution. This recommendation is based on my over five decades of experience as a practitioner of energy conservation engineer in government as well as private industries. China and most of the developing world are at a very critical stage of modernization. The important policy of scientific development calls for harmony with nature, within the society and world harmony. To play a responsible role as a rising and renaissance major nation China must set an example in her renewable energy policy. With the ample evident merits as discussed here, not to include the Solar Engine Systems for consideration as a major part of China’s energy independent policy is unconscionable. Your humbly is available for consultation by invitation from relevant energy implementation department and provincial heads. An Executive Summary of Stirling Engine Concept Proposal is available by request.

In Service of Energy Independence
Francis C W Fung, PH.D.
Solar Stirling Engine Partnership (SSEP)
A Commission of World Harmony Organization

Capacity: 500 MW with expansion option to 850 MW
20,000 - 34,000 solar dish Stirling systems


Phase 1 of this project is to develop 500 MW of electricity generating capacity, which will then be followed by Phase 2, which will involve an expansion up to 850 MW of generating capacity.
Power output from this facility will be sold in accordance with a 20-year power purchase agreement to Southern California Edison Company (www.sce.com), a subsidiary of Edison International.


The project site for Solar Two is located in Imperial County in Southern

Capacity: 300 MW with expansion options to 900 MW
12,000 - 36,000 solar dish Stirling systems
20-Year Power Purchase Agreement


Phase 1 of this site will consist of 12,000 solar dish Stirling systems that will be capable of generating 300 MW of electrical power. Phase 2 of this will expand the number of solar dish Stirling systems to 36,000 units, which will be capable of generating up to 900 MW of power.
The power generated at this site will be sold in accordance with a 20-year power purchase agreement to San Diego Gas & Electric (www.sdge.com).