This topic has great relevance to steam power because the end result is peak electricity production. In order to accomplish this goal there needs to be a complete system in place. Few people have the knowledge to design a complete system, one that uses modern steam, bio-fuel production, standard agriculture materials handling, drying and storage of fuel, and wind and solar power. This whole business sits on a farm and makes income for the farmer. The system uses ferro-cement, and specifically pre-stressed ferro-cement made with a system I developed years ago and for which I was under-capitalized.
This electrical generating plant is designed to be placed on a typical American farm of a thousand acres or so that is in the cash crop business. Cash crops are corn and soy beans, for the urban dweller. The purpose is to make distributed power to sell to the existing grid and this presumes laws requiring the utilities to purchase power. The power can be generated during peak usage times, and thus is of much greater value than power made randomly and irregularly, as happens with wind and solar.
The explanation will be long and involved and every piece has to work together for this to make sense. Some faith will be needed during the explanatory process, but little faith will be needed at the end. Here are the reasons this makes sense and also the reasons it will work. To begin with an American farm is already a small business, albeit one with high capital investments. Usually we are talking about $5 million in land, $1 million in buildings and facilities, and $2 million in equipment–tractors, combines, and semi-trucks. The main difference between this business and other businesses is the extreme seasonality of the work. I do not know for certain, but it appears to me that there is a month in the spring and a month in the fall when most of the farm equipment is used. The second difference between modern farming and other manufacturing is the very low rate of hired help. Most of the work is done by the farm family, hence the very large pieces of equipment. Back to the farm being a small business; it already has an office, a computer, a book keeper, a banker, and an accountant. Therefore everything is in place to run a business.
The second item needed to be in the electricity business is fuel. Of the several sources of bio-fuel, the first one would be from marginal land. Almost every farm has hills, ravines, poorly drained land or steep land or just plain unfertile land. Almost every farm has a wood lot. In other words there is usually land that cannot be economically used for growing cash crops. This land can be used to grow bio-fuels. When looking at bio-fuels what one is looking for is dry tons of cellulose per acre per year that can be burned. There are two kinds of trees good for this, and because they coppice; willows and poplar. The technique is to plant these in rows close together and every two years cut them about a foot or so from the ground. Coppicing means that many small branches grow from the stump achieving maximum productivity on a two year harvest cycle. The other crops are grasses, either Panicum virgatum, Miscanthus sinensis, Arondo donax, or whatever grows in that climate or whatever needs to be grown for ideological purposes, which is why native prairie grasses are talked about so much. Other bio-fuels are straw, corn stover, rotten or out of date seed corn, cattle manure, or wood from land clearing.
The bio-fuel crops are then harvested in the off-season for cash crop farming. Grasses will be harvested in the fall after frost and when dried the most and before the leaves fall off. Wood will be harvested in the spring either just before or after spring planting. Most of the existing agricultural equipment can be used to harvest, compact, and transport the fuel.
Storage and drying is important. The most practical method is to use a poly covered gutter connected greenhouse. The cost of materials is about $5 a square foot. A concrete floor will cost almost that much again. These structures can be made quite high or tall, with 20 feet being within reason, giving a large volume. The beauty of a poly covered greenhouse is how much it heats up in the summer when the sun is shining. It will heat up some in the winter when the sun is shining. If the structure is covered with tempered glass, a possibility if one can afford the extra cost, then heat is reflected back into the structure, causing it to heat up even more. Otherwise a double layer of poly with air blown between the layers, standard practice, gives some insulation value. Therefore the large gutter connected structure would be loaded up with dry material in the fall and wet material in the spring and be kept dry from the rain and heated up by the sun. Later on we will discuss the great benefit of hot humid air as it goes up a solar chimney and how we can use the energy from that air flow to power a turbine. For now we have solved the fuel storing and drying issue.
Some fuel processing is needed. The less the energy input the better and that is why we want to avoid shredding, pelletizing, grinding, or anything besides shearing, which takes relatively little energy. Straw and grass would be baled in the large round bales. Shrubs or wood branches would be bundled or sheared for transportation and then processed as little as possible for burning. Cattle manure would be dried in the gutter connected to be handled as a solid. In parts of the country everything from orange peels to olive pits will be used for fuel. Almost any agricultural by-product is cellulose and thus has potential for fuel.
Other sources of fuel will present themselves as the market develops. The beauty of every large farm having one of these systems is that transportation is minimized. One of the better potential fuels is glycerin, which is a by-product of bio-diesel production. It is difficult to burn alone but should be possible with other fuels. There is always sawdust where there is the lumber industry. We cannot anticipate all of the future by-products of food and manufacturing, we just assume they will show up sometime.
The next thing we need is a large silo shaped structure and this will be made from ferro-cement panels used as permanent forms and poured with concrete. It will be constructed with minimum labor and in a weather protected enclosure and be useful as a wind mill base or a solar chimney or for grain storage for the other farm products. The silo is not critical to getting the electricity made, it just will make the whole system work better.
The steam engine will be a 500 or 1,000 hp piston engine, or several ganged together. The latest designs are achieving good efficiencies, certainly better than the 6% the old coal fired railroad locomotives did. They had to be mobile and thus could not afford efficient heat exchangers. Several of these engines are being designed. Engineering development will be needed. It is possible to use a stationary Skinner Uniflow engine, or even to just copy one of them. At 200 rpm they are quite massive for the power produced. The burner and boiler, or more precisely the combustion chamber and heat exchanger, will be of modern design. Good combustion burns completely and cleanly. Good heat exchange will probably be a natural circulation water tube design that uses standard pipe of 21′ lengths with the fewest fittings or welding needed for construction.
The condenser is critical, and here is where the solar chimney comes in for good air flow without requiring energy inputs. If possible, the waste heat will be used to heat buildings. This is something that will develop organically. We, right now, do not need to figure out all possible side benefits to making electricity from bio-fuels because once this becomes common someone or more probably everyone will figure out what to do with the extra heat.
As long as the steam engine and infrastructure for making electricity and getting it onto the grid are in place, then it is logical to make solar heat using troughs. It almost makes sense to use a flat plat collector system to make steam, it is just not quite hot enough at saturation temperature to make efficient steam and therefore some extra reflectors or concentrators will be needed. Just roughly estimating, a 100 foot square area will produce 100 hp when the sun is overhead. Therefore not a whole lot of room is needed to produce enough solar power to be practical. What is needed is cheap and reliable. One would think that big solar troughs rolling on an area of flat ground to follow the sun would be a good way to start. I, of course, would make these out of pre-stressed ferro-cement. Once solar heat is made, then we will want to store the heat. Here, again, the issue is money and reliability and not necessarily perfect efficiency. I have many ideas on how this can be done.
And so we now have a system that will produce somewhere between $100 and $200 an hour worth of electricity. All that is needed next is to look at capital investment and capital cost, meaning interest rates. The unknown factor is carbon credits, tax incentives, and whatever else may be coming down the pipeline of political machinations. One may want to keep in mind that the political will is fickle. What it gives it can take away.
As the alert reader will note; this system has many highly technical parts. One needs to know how farms work, how steam engines work, how greenhouses work, how good combustion works, and how solar reflectors work. The reason we do not have these things all over the place now and instead have the landscape festooned with really complex wind turbines is because no one understands how each of the components work. It takes a broad knowledge base to put this system together. It is, likewise, not something that an engineer can design. It is something that an engineer can make work once someone else has designed it. Therefore the reader is fortunate to have my experience and skills and knowledge in agriculture, greenhouses, steam engines, solar collectors and making electricity.