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AY Honors/Woodworking/Answer Key

2007-11-12T13:13:25Z

62.171.194.9: /* Dowel */

{{honor_header|2|1934|Vocational|General Conference}}
==1. Tell how the following processes are related to lumber and how each process is done: ==
=== Growing Trees ===
Lumber comes from trees, so in order to get lumber, a tree must be cut down. Before a tree can be cut down, it must be grown. Many areas are managed forests, where once the trees have been harvested for lumber, new trees are planted to take their place. Doing so make lumber a sustainable resource. The science of growing trees is called forestry.

=== Harvesting of Trees ===
Harvesting of trees is the practice of cutting them down in order to convert them into lumber. There are several approaches to this, including clear cutting and selective cutting.

When a forest is clear cut, all woody plants are removed. The larger ones are cut into 16' sections and used for making lumber. Contrary to popular belief, clear cutting can actually be beneficial to the forest, as it simulates the effect of a natural forest fire. The trees that are planted in the clear cut will receive more light, and thus produce more lumber more quickly. However, the clear cut should be replanted with the same species of trees that were harvested from the area. Clear cutting is often done during a season on several small tracts of land in a larger forest. This staggers the harvest so that it can be more easily sustained over long periods of time.

Selective cutting is the practice of only removing mature trees from a forest. This has a lesser impact on the forest, but it takes longer to produce lumber and it is more labor intensive than clear cutting. Selective cutting preserves other aspects of the forest though, including its beauty, and its role as a wildlife habitat.

=== Milling ===
Milling lumber is the process of sawing logs into boards. This is usually done at a saw mill. There are many ways to cut a log into boards, and the method chosen affects the quality of the lumber and the amount of lumber that can be obtained from the log. Quarter sawing produces the highest quality lumber, but it does not produce as much lumber as other methods (such as flat sawing). In quartersawn lumber, the log is first divided into quarters, and then each plank is sawn from that such that the growth rings go through the plank perpendicular to the plank's face.

[[Image:Quartersawn.png|300px|Quartersawn Lumber]]

In flat sawn lumber, All the cuts are made in the same direction. Thus, the growth rings penetrate the board at many different angles. This method of cutting produces the most lumber from a log, but that lumber will be far more susceptible to warping and cupping.

[[Image:Flatsawn.png|320px|Flatsawn Lumber]]

=== Curing/Seasoning ===
Curing and Seasoning lumber are two words for the same process. It is the process of drying lumber after it has been milled. When timber is first cut, over 50% of its weight is water. As the lumber dries, it changes shape. If it is dried unevenly, it will warp, twist, and crack (cracking is also called "checking"). This is because as the lumber dries, it shrinks. If it dries unevenly, it will also shrink unevenly. To season lumber, it must be allowed to dry evenly. There are several ways to accomplish this, but the two most common are air drying and kiln drying. After the lumber is milled into rough boards, it is stacked horizontally in layers. Each layer is separated by "stickers" which are small pieces of wood about an inch thick, an inch or two wide, and as long as the stack is deep. Stickers are placed on the floor first, and the first layer of lumber is stacked on top of it. More stickers are placed on top of the first layer directly above the stickers on the floor, and another layer of lumber is placed on them. This is repeated until there is a large stack of lumber. Separating the lumber like this allows air to circulate evenly, and thus, the lumber will dry evenly. Kiln dried lumber is stacked in a kiln (a type of oven) in the same way as air dried lumber.

=== Grading ===
The quality of lumber is widely variable. The difference between the wood suitable for making shipping crates and pallets and the wood suitable for making furniture and toys is fairly large. Grading lumber is the process of assigning a quality figure to it - not unlike grading a school paper or a test. Lumber is graded based on the poorest side of the lumber, and on the yield the lumber is expected to produce (that is, how much of the wood can be converted into boards verses how much will be thrown away).

There are four basic grades of lumber, and even these grades have sub-categories. The basic grades are listed here from the highest quality to the lowest quality:

'''FAS ''' is short for "'''F'''irsts '''a'''nd '''S'''econds." Lumber of this grade is at least 83% clear (free from all defects such as stains, splits, worm holes, knots, etc) on its poor side.

'''No. 1 Common''' is the next grade of lumber. It is often used in furniture making. It must be 67% clear on its poor side.

'''No. 2 Common''' must be at least 50% clear on its poor side. It is often used in cabinet making and in millwork (molding, baseboards, and other trim). This grade of lumber is excellent in applications that will be finished with paint (as opposed to a natural finish).

'''No. 3 Common''' is the lowest grade of lumber. There are two sub-categories called 3A and 3B. 3A must be at least 33% clear, while 3B must be at least 25% sound (rather than clear). 3A is often used for flooring, while 3B often used for making pallets and crates.

References:

[http://www.woodweb.com/knowledge_base/Basic_lumber_grades.html Basic Lumber Grades]

[http://www.woodweb.com/knowledge_base/Understanding_Hardwood_Lumber_Grading.html Understanding
Hardwood Lumber Grading]

=== Sizing ===
Once lumber has been milled and cured, it is sized. There are three common methods of sizing lumber. The first and most common is dimensional. The most well known of the dimensional sizes is the 2 by 4 (2x4). Other sizes include the 2x6, 2x8, 4x4, etc. Before a 2x4 is sized, it is 2 inches thick and 4 inches wide. The lumber is then planed so that the edges are smooth and the thickness is even. The planing process removes about a half inch of lumber, so the finished 2x4 is really 1.5 inches thick by 3.5 inches wide. It is still called a 2x4 though, because that's much easier than calling it a 1.5 x 3.5.

The second sizing method is known as quartering. Rough sawn lumber is sized in quarter inch increments. A one inch thick, rough sawn plank is called four-quarter, and this is written as 4/4. Rough sawn lumber is also available in 5/4, 8/4, and 10/4 sizes. These are 1.25", 2", and 2.5" thick respectively.

The third sizing method is the board foot method. A board foot of lumber is one inch thick, 12 inches wide, and 12 inches long. In other words, a board foot of lumber contains 144 cubic inches of wood. Even if the plank is not 12 inches wide or one inch thick, it is still sold by the board foot. One way to calculate how many board feet are in a plank is to first calculate the number of cubic inches (width times thickness times length, all in inches) and then divide that by 144.

==2. Collect and label five different kinds of wood used in woodworking. Tell the advantages and disadvantages of each. ==
'''Pine'''
Pine is the most commonly available wood in North America. Its primary advantage is that it is relatively cheap. This is because is grows rather quickly. Another characteristic of pine is that it is soft. This can be both an advantage and a disadvantage. The advantage of a soft wood is that it is easy to work. The disadvantage is that it can break easily; delicate joinery that works fine in hardwoods will not hold up in pine.

'''Oak'''
Oak is a very common hardwood. It is a tough wood that holds up well when stressed. It was often used in shipbuilding because of this toughness. Additionally, oak is fairly workable up until it is seasoned. Seasoned oak is ''very'' hard, which makes it difficult to cut, bore, plane or drive a nail through. This is an advantage in the finished product, but a disadvantage when trying to make something. When using oak, it is best to use unseasoned wood, and let it season once the object has been made.

'''Maple'''
Maple is a light colored wood that can be found with highly figured grain. Figured grain is difficult to work with, but makes for a beautiful piece of furniture. Maple is also great for toy making because it does not easily splinter and stands up well to the abuse of even the most destructive of children. Maple is also commonly available, and thus, is relatively cheap for a hardwood.

'''Walnut'''
Walnut is a dark hardwood. Its color is one of its chief advantages, and is probably wood most often "copied" by staining lighter, cheaper woods. Walnut also has figured grain and is fairly hard. It holds detail well, so it can be used in making intricate joints. It is also relatively expensive for a native hardwood.

'''Cherry'''
Cherry is another hardwood that is commonly used in furniture making. Its color starts off as a medium brown and then slowly turns to a dark, beautiful reddish hue over time. It takes a nice finish, and has no need for stain. It is a little cheaper than walnut, but still fairly expensive.

'''Poplar'''
Poplar is classified as a hardwood, but it is relatively soft (though still harder than pine). Because of its softness, it is easy to work.

'''Elm'''
Elm is a hardwood that is highly resistant to splitting. Because if this, it was the only wood used to make the hubs of wooden wagon wheels. It has a highly figured grain that entwines, and tangles itself in all directions - this is what makes it so difficult to split, but it also makes it difficult to plane.

==3. List the basic hand and power tools necessary to do woodworking. Know how to safely use each tool and how to keep it in proper working order, including sharpening, if applicable. ==

Technically, no power tools are necessary for woodworking - everything can be done with handtools. Power tools can certainly make the job easier, but they are a relatively recent tool to arrive on the woodworking scene.

=== Handsaws ===
Handsaws are tools used for cutting wood. Handsaws come in many varieties, including the crosscut saw, rip saw, coping saw, tenon saw, backsaw, and dovetail saw. Each has its own special use. A crosscut saw is used for cutting across the grain of a piece of lumber. A rip saw is used for cutting along the grain. A coping saw is used for making curved cuts. A tenon saw is used for cutting tenons and other fine work. A backsaw is commonly used with a miter box and for small cutting jobs. A dovetail saw is used for cutting dovetail joints.

To use a crosscut or a rip saw, place the board on a supported surface at thigh-height (between the knee and hips). Grip the saw with the right hand (assuming right-handedness) and use the left knee to hold the board in place. Align the right shoulder, arm, and hand so that they are in line with the cut to be made. Begin with light strokes, noting that the saw cuts on the push stroke. As the cut progresses, keep an eye on the line, pulling the blade toward it. If this is to be a "finished" cut, you can score a "V" along the line first with a carton knife, and let the blade ride in the V groove. Score another line along the bottom of the board to prevent tear-out.

A saw is sharpened with a triangle file. The teeth of a rip saw (which cuts along the grain) are sharpened perpendicular to the blade. The teeth of crosscut saw are sharpened at an angle. Try to match the angle already ground into the teeth.

Maintain your saws by keeping them dry and sharp. Many tools (including saws) can be kept in great condition by wiping them down with a cloth and oil (or WD40) after each use. Coping saw blades can be obtained cheaply enough that it is easier to replace them than it is to sharpen them.

=== Chisels ===
Chisels can be used for making a variety of cuts in wood, from mortise and tenon joints to dovetail joints. They are often struck with a mallet or a hammer, but sometimes they are pushed by hand (watch for fingers!) to pare a joint or to smooth it. Chisels are also used to remove wood for recessing a hinge. To do this, the outline of the hinge is first scored with a knife, and then the wood is pared away with the chisel.

To cut a mortise, choose a chisel that is as wide as the desired mortise. Mortises should only be cut so that they are parallel to the grain of the wood. Mark the mortise out, and then place the chisel perpendicular to the grain, such that it covers the width of the mortise. Strike it with the mallet. Then move the chisel about an eight of an inch farther down the mortise and repeat. Each "bite" of the chisel will go a little deeper. When you get to the end of the mortise, reverse the chisel and take bites in the other direction (still perpendicular to the grain, but heading back toward the other end of the mortise). Continue until the mortise reaches the desired depth. Always cut the mortise first, and then size the tenon to fit.

To sharpen a chisel, hold it at a steady angle and drag it along a whet stone. If you use a grinder, be careful to not overheat the tip of the chisel as this will cause it to lose its tempering. It is better to sharpen them by hand with a whet stone, as it is very easy to overheat the blade with a grinder.

Store chisels in a way that will protect the cutting edge, either by covering them, or placing the edge where it will not come into contact with anything of equal (or greater) hardness than the blade. Like saws, chisels can be wiped down with cloth and oil to keep rust away.

=== Hand Planes ===
(Some material taken from the [http://www.wikipedia.com Wikipedia])

A hand plane is a tool for shaping wood. Planes are used to flatten, reduce the thickness of, and impart a smooth surface to a rough piece of lumber.

Hand Planes are one of the most satisfying tools to operate. Clamp the wood securely to a bench, and then push the plane along the grain. The blade should be adjusted so that it takes a thin shaving off the plank. A sharp, well adjusted plane will remove a continuous shaving the entire length of the board. Pay attention to how the grain runs - if the grain dives into the board, make sure the plane's blade does not break the shaving off below the surface. If this happens, try planing in the other direction (see illustration).

[[Image:Planing_wood_with_the_grain.PNG|300px]] [[Image:Planing_wood_against_the_grain.PNG|300px]]

Once the blade has been removed from a plane, it can be sharpened in the same fashion as a chisel. It should be sharpened frequently, as this will greatly improve its performance.

A plane should be stored on its side to respect the blade. You should also be very careful to not plane into a nail or a screw, as doing so will put a nasty notch in the blade.

=== Clamps ===
Clamps are used to hold a piece of wood in place while it is being worked, or to hold pieces of wood together after gluing them until the glue cures.

Clamps come in many varieties, including C-clamps and furniture clamps. Some say that it is nearly impossible to own too many C-clamps. When using a C-clamp in wood working be careful to not overtighten it. The clamping surface can easily leave a circular impression on the wood. If you need to get it really tight, place a piece of scrap between the clamping surface and your piece.

Furniture clamps (also called bar clamps) often have padded clamping surfaces, so making unwanted impressions on the wood is avoided. These are used for clamping large boards together, usually edge-to-edge.

Clamps can be periodically wiped down with a cloth and oil to keep rust at bay.

=== Drills, Bits, and Braces ===
Drills, Bits, and Braces are used for boring holes in wood. A brace and bit is the "old-style" cordless drill. It is hand-powered. The brace holds the bit, and the woodworker's hand cranks it, inducing a rotation in the bit. To drill a clean hole with either a brace and bit or a drill and bit, hold the bit perpendicular to the board and start drilling. You can start a pilot hole with a nail or a punch first to keep the bit from wandering. There are two ways to prevent tear-out when boring a hole. The first method is to support the board and drill into the supporting material. For this to work, the board and its support must be firmly clamped together. The second method can be used if you have a bit with a point that is much narrower than the hole's diameter (such as a spade bit, a brad-point bit, or a bit with a screw-lead). Using such a bit, drill through the material until the tip comes through the other side. Then turn the board over and place the bit in this hole. Continue drilling toward the center.

=== Power Tools ===
Power Tools should be used with much care. It is difficult to cut a finger off with a hand saw, but a power saw can do this in an instant, and before the careless operator even feels any pain, a severed finger can drop to the floor. Power tools can greatly speed production of wood projects though, so it's certainly worth having them around. Read the owner's manual carefully before operating any piece of power equipment. Pay special attention to safety features, and do not try to defeat them! Pathfinders below the age of 16 should not use power tools. Remember, power tools are not required for woodworking, they only speed it along.

==4. Explain the following joints: ==
=== Butt ===
A butt joint is the simplest of all joints, formed by butting two pieces of wood together and then joining them. But because glue will not hold to end grain, it is a joint that must be held together by mechanical fasteners such as nails or screws.

[[Image:Butt_joint.png|350px|Butt Joint]]

=== Dado and groove ===
[[Image:Dado.png|right| Dado Joint ]]
A dado and groove joint is formed by milling a slot (or dado) in one board, and inserting another board into that slot. The width of the dado should be equal to the width of the board that will be inserted into it. The dado is an excellent joint for joining plywood shelves to the upright sides of a bookcase. In this case, the dado should be cut into the side, and the shelf should be inserted into the dado. Such a shelf will support a lot of weight without relying on the strength of a mechanical fastener. A butt joint would likely fail in this situation, with the nail or screw splitting out the top of the shelf.

The dado can also be used in regular lumber as long as the dado runs along the grain - otherwise, any glue used to secure the joint would have to adhere to the endgrain. Plywood presents alternating layers of endgrain and straight grain to all three surfaces of the dado, and there is generally enough straight grain in the joint that gluing it works well. Dado and groove joints can be held together with mechanical fasteners (nails or screws), or without them (assuming enough non-endgrain surfaces in the joint).

=== Dovetail ===
[[Image:dovetail.png|right|300px|Dovetail Joint]]
A dovetail joint is made by making "tails" in one piece of wood, and "pins" in the other. In the diagram here, the tails are made in the board on the left, and the pins are made in the board on the right. This joint is very strong and will only pull apart in one direction. It is often used for making drawers and boxes. When making a drawer, the pins are cut in the drawer front, and the tails are cut into the drawer sides. This will prevent the joint from pulling apart when the drawer is opened. A drawer facing is then glued to the front to hide the joint, or the joint can be modified to hide them inherently (these are called "blind dovetails").

To make the joint, cut the tails first. Lay them out with a bevel gauge, and saw from the edge to the line. Remove the waste with a chisel. Then lay this board on top of the board that will have the pins and line them up. Mark the pins with a knife. Then saw the pins with a dovetail saw (or a backsaw). The waste on either side of the pins can be removed with a saw. The waste between the pins can be removed with a chisel or with a coping saw. Assemble the joint to test it for fit, and pare the joint with a chisel if necessary.

In the illustration, the endgrain is colored orange. When gluing a dovetail joint, don't bother applying any glue to the endgrain surfaces. Note that the top surface of the pins (brown) are not endgrain, nor are the surfaces they mate to on the tails.

=== Dowel ===
[[Image:Dowel_joint.png|right|Dowel Joint]]
A dowel joint is formed by drilling holes in the two pieces to be joined, and inserting dowels (small wooden rods) into these holes. The dowels are coated with glue prior to insertion. This is most commonly done with butt joints and miter joints, as the addition of the dowel greatly increases their strength by providing gluable surfaces to the joint.

The most difficult aspect of making a dowel joint is lining the holes up on the two pieces of wood and making sure that the holes go in at a 90 degree angle. This can be done more easily with the aid of a doweling jig. A doweling jig resembles a clamp with a guide hole drilled into it. It is clamped to the board which will eventually accept the dowel, and the hole is drilled by inserting the bit into the guide. A doweling jig will ensure that the hole is drilled at a consistent distance from the board's facing edge and that it is made at a 90 degree angle. The woodworker is still required to ensure that when multiple holes are used (recommended to prevent the joint from twisting), they are drilled the same distance apart. this is the best.

=== Lap ===
[[Image:Lap_joint.png|350px|left|Lap Joint]]
A lap joint is made by overlapping two boards. Wood is removed from the joint so that each board contributes about half of the wood in the joint. Lap joints can be made to join boards at a 90 degree angle (as shown), no angle at all (that is, splice two boards into a longer one), or the two boards can form a cross. This joint is ideal when you need to bring two boards together but keep them in the same plane. It is very strong even without mechanical fasteners as there is a lot of gluable surface area in the joint.

The laps can be cut with either a saw, or a with a saw and a chisel. Large lap joints should be cut with only a saw, but they can be trimmed with a chisel. A dovetail saw or a backsaw works well for both cuts.

=== Miter ===
[[Image:Miter_joint.png|350px|right|Miter Joint]]

A 90 degree miter joint is formed by cutting the two boards at a 45 degree angle and joining them. The choice of a miter joint is purely aesthetic. Miter joints are easy to cut with a power miter saw, but difficult to cut by hand. A miter box can help, but the angle of the cut must be very nearly perfect, or the joint will either not be 90 degrees, or it will show a gap. The gap can be eliminated by "kerfing in" the joint. Kerfing in a joint is done by clamping the two pieces together and then running a fine-toothed handsaw down the joint. Ideally, the saw should remove wood from both pieces. This procedure can be repeated until the woodworker is happy with the fit, but keep in mind that every time this procedure is performed, the board gets a little shorter. For this reason, it is best to cut the miter joint first, and then cut the piece to length. If both ends of the board are to be mitered, the board should be cut a little long and then tuned to length by kerfing it in.

Miter joints must be reinforced or they will not hold (once again, endgrain comes into play). Usually the pieces are fastened to some underlying structure so that the miter joint is not subjected to stress, nor is it relied upon for structural integrity. In other cases, the joint itself can be reinforced using dowels (as in a dowel joint) or some similar mechanism.

=== Mortise and Tenon ===
[[Image:Mortise_and_tenon.png|250px|right|Mortise and Tenon]]

The mortise and tenon joint is a strong joint used to join two pieces of wood usually at a 90 degree angle. The mortise is a hole cut into one of the pieces, and the tenon is shaped to fit snugly into this hole. The tenon is usually narrower than the rest of the piece that it is cut into. The joint may be glued, pinned, or wedged to lock it in place.

The mortise is usually cut first, and its width is equal to the width of the chisel used to cut it (see the section on chisels). The tenon is then sized to fit the mortise, and it is cut with a tenon saw, dovetail saw, or backsaw. The first cuts are made along the grain and are called the cheek cuts. The final cuts are made across the grain and are called the shoulder cuts. The tenon can be pared with a chisel to tune the fit.

=== Rabbet ===
[[Image:Rabbet.png|200px|right|Rabbet Joint]]

A rabbet joint is very similar to a dado joint, except that the groove is cut at the edge of the board. This groove is called a rabbet. It is also sometimes called a rebate. A rabbet joint is often used for joining the back to a cabinet or bookcase. It can be glued, held on with mechanical fasteners, or both. The rabbet can be cut in either or both pieces to be joined.

A rabbet joint can be made with a table saw or a router. It can also be made with a rabbet plane. The blade of a rabbet plane comes all the way to the edge of the tool so that it can remove wood from the corner of the rabbet.

==5. Know the characteristics of and how to work with the following: ==
=== Hardboard ===
Hardboard (also called Masonite) is an engineered wood product made by turning wood chips into long fibers by steaming them. These fibers are then heated and pressed into a solid board. Hardboard is sold in 4'x8' sheets of various thicknesses in the United States. It is an extremely stable material, expanding and contracting very little with changes in temperature and humidity. It is highly homogeneous, having no distinct grain. Because of its lack of grain it behaves very differently as compared to regular lumber.

Hardboard has high bending strength, but has very little structural strength, so it cannot be used in many applications where plywood or regular lumber are more suited. It can be used for building arches, and its strength can be improved by laminating several sheets together. Hardboard is often used as drawer bottoms, or as the back of cabinets, etc.

=== Particle Board ===
From [http://www.wikipedia.com Wikipedia], the free encyclopedia.

Particle board (sometimes called chipboard) is a material manufactured from wood particles (for example, wood chips, sawmill shavings, or even saw dust) and a synthetic resin or other suitable binder, which is pressed and extruded. Particle board is very dense, heavy, and flat. It is used as a cheaper and less durable substitute for solid wood or plywood. Particle board is very prone to expansion due to moisture.

Particle board should not be used in applications where it is likely to get wet. It is generally not used in furniture making unless it is covered with a veneer (or in inexpensive furniture, a vinyl covering similar to wallpaper). It is not generally finished with stain, varnish, or paint, as aesthetics are not high on its list of characteristics. It is, however used in the hidden portions of woodworking projects such as drawer backs and sides.

=== Plywood ===
From [http://www.wikipedia.com Wikipedia], the free encyclopedia.

Plywood was the first type of engineered wood to be invented. It is made from thin sheets of wood veneer, called plies, which are stacked together with the direction of each ply's grain differing from its neighbors by 90° (cross-banding). The plies are bonded under heat and pressure with strong adhesives, usually phenol formaldehyde resin, making plywood a type of composite material.

A vast number of varieties of plywood exist, tailored for all manner of conditions and uses. Softwood plywood is usually made either of Douglas fir or spruce, pine, and fir. Decorative plywood is usually faced with hardwood, including red oak, birch, maple, lauan (Philippine mahogany) and a large number of other hardwoods.

Plywood production requires a good log, called a peeler, generally straighter and larger in diameter than that required for processing by a sawmill. The log is peeled into sheets of veneer which are then cut to the desired dimensions, dried, patched and glued together to form the plywood panel. The panel can then be patched, resized, sanded or otherwise refinished, depending on the market it was intended to be sold in.

The most common varieties of softwood plywood comes in three, five or seven plies with dimensions of 4 feet × 8 feet. Each ply is 1/8 inch.

A common reason for using plywood instead of plain wood is because plywood is more stable and because it is less prone to change (shrink, twist or warp). Plywood is stronger than particle board and hardboard, and because the outer layers can be made from fine hardwoods, it is often used in furniture making. It is suitable for natural finishing or painting.

==6. Know at least two ways to finish the edges of plywood. ==

Unfortunately, some layers of plywood often have knots in them, and the knots fall out before the layers are glued together. This leaves a void. In furniture-grade plywood these voids will be confined to the inner layers. In order to finish the edge of plywood, you can either fill these voids with a wood putty, or you can cover the edges with a band of material - typically, a veneer or a thin strip of wood. Some veneers are made expressly for this purpopse, and they come with an adhesive on one side. By heating the veneer, the adhesive is activated. When it cools, the adhesive bonds to the edge of the plywood. If you plan to use a natural finish, banding works best, because wood putties and wood tend to take natural finishes unevenly. This results in a splotchy finish where the wood putty stands out rather than concealing the defect. Either method can be used if you plan to finish with paint.

==7. Demonstrate the proper technique of gluing and clamping wood. ==
The first rule of gluing wood joints is that glue does not stick to end-grain. Most woodworking joints were in fact designed to avoid the application of glue to an end-grain surface. Evaluate your joint first, and find two non end-grain surfaces that will come into contact. After making a test fit, apply glue to one of these surfaces. Spread the glue in a thin layer, being careful to not use too much glue. Then clamp the two pieces together. Use enough clamping pressure so that the pieces are held firmly together, but do not use so much force that all the glue is squeezed out of the joint. Once clamped, the pieces should be left alone until the glue sets. Setting times vary from one glue to the next, so read the instructions on the glue container.

==8. Choose a plan for and complete an article of household furniture, such as a small table, footstool, writing desk, or bookcase. List the materials needed for your project. ==
There are thousands of plans available on the Internet, and many of them can be downloaded for free. Others are offered for a fee. You can also find plans in books and in woodworking magazines (although the magazines tend to have more complex plans). Choose plans that are simple. Although the instructor may be an experienced woodworker, the student is often not. Avoid complicated joints such as dovetails and mortise and tenons. Butt joints, dados, and lap joints are within the reach of a 12 year-old, so steer your Pathfinders to projects that use them. Use lots of pine. Pine is relatively inexpensive, and using it makes it a lot easier to start over. It can be heartbreaking to watch a youngster destroy an expensive piece of wood, and the temptation to salvage it (and thus ruin the project) can be overwhelming. Save complicated projects and expensive hardwoods for after the Pathfinder develops some skill.

[[image:Sm_table_complete.jpg|240px|right|Small Table]]

The table described here has been successfully constructed by a group of Pathfinders ranging from Friend to Guide. It is relatively inexpensive, as seven tables can be constructed from a single sheet of plywood, five 8-foot 2x4's, some plywood banding, 28 1/2" #8 woodscrews, seven dozen 1.5" #8 woodscrews, some flat metal brackets, and some 3/8" dowels. Seven is a good number of Pathfinders for two instructors to handle in this honor. More Pathfinders (or fewer instructors) and it is difficult to give them the attention they'll need to execute the project successfully.

=== Preparations by the Instructor ===
The instructor should rip the 2x4's into 2x2's, and perhaps crosscut them into 30" lengths (although this can be left to the Pathfinder). These 2x2's will make the legs of the table, and the instructor should make sure the legs are square (that is, each side should be 1.5" or 1.25" wide - the exact measurement is immaterial so long as it is the same on all four sides).

[[image:Sm_table_parts.jpg|240px|right|Small Table Parts]]

The instructor should also cut the plywood into squares. For seven tables, 14 12"x12" squares (for the bottom and middle shelves) and 7 14"x14" squares should be made (for the tops). These should be made from furniture-grade plywood with a hardwood veneer. Birch veneer works well for this.

=== Cut the corners ===
The Pathfinder should mark the corners of the shelves by measuring in 1 inch from each corner and drawing a line across the corner. If the shelves are square, this should make a perfect 45° angle. Do not cut the corners off the 14"x14" tabletop. Save the corners, as they can be used to correct a common mistake (discussed below).

=== Notch the legs ===
The pathfinder should then cut two notches in each of the four legs in the three steps shown below:

[[image:Sm_table_cut_legs.jpg|350px|Cutting the Notches]]

'''1:''' Mark a pencil line one inch from the corner edge of the leg. Do this on two adjacent sides.

'''2:''' Measure the width of the plywood and mark where the notches are to be cut with a square. It is better to mark all the legs at the same time, making sure leg bottoms are flush and the notches all line up. Once all the notches have been marked, a notch can be made by cutting two kerfs (saw cuts) through the corner of the leg stopping when the line is reached. You may wish to score the notches with a carton knife before using the saw. Make the first score on the line, holding the knife at a 90° angle. Then make a second score at a steeper angle next to the first score line, but towards the middle of the notch so that the two make a V. Remove wood from the V. This will give you a defined groove for the saw blade to ride in. Pay close attention to ''both'' lines when cutting, and be sure to take the width of the kerf into account when making the cuts. The width of the notch should equal the width of the plywood.

'''3:''' Use a 3/4" chisel and a mallet to remove the wood between the kerfs. Do not try to remove all the wood at once, but rather, remove a quarter inch on the first three passes, and an eigth of an inch on the final passes. Pay attention to the pencil lines.

=== Attach the Shelves===
The next step is to attach the shelves to the legs. This can be done using dowels or screws. In either case, drill holes into the leg from the outside, centered on the notches. Put the shelf into the notch, and drill a hole into it, using the hole in the leg as a pilot. If using dowels, use the same sized bit (sized for the dowel, 3/8" recommended). If using 1.5" #8 screws, use a 1/8" bit, and then counter sink the hole in the leg 1/2" to 3/4" deep. The screws can be covered with dowels or with wood putty (but don't use wood putty unless you plan to paint).

=== Correcting Problems ===
If the notches are too wide, use a chisel to shear a ply off the corners that were removed from the shelves and wedge it beneath the shelf. Note that this is a corrective procedure only - it is much more desirable to cut the notches to the proper width. Using this technique pretty much decides that the table will be finished with paint instead of with a natural finish, but it can still come out looking pretty good. If the notches are not wide enough, use a chisel to widen them a bit. Don't overdo it.

If the notch is too wide to be corrected with a single ply from a corner, discard that leg and start over. That's why the legs are made from 2x4's - you can get six legs from a single 2x4, so each leg will run you about 50 cents (in 2005 anyhow).

Once both shelves have been attached to all four legs, the screws can be covered with dowels (if the screws were countersunk) or with wood putty.

=== Fasten the Top ===
Finally, it is time to add the top. The easiest way to do this is by using flat metal brackets. Look for them in the fastener department of the hardware store. Basically, they should be pieces of steel about 3/8 inch wide and 2 inches long, with holes drilled in either end. At least one of these holes should be countersunk, or they should be countersunk on opposite sides of the bracket.

[[Image:Leg_bracket1-4.png|600px|thumb|1. Bore first hole; 2. Overlap second hole; 3. Connect the channels; 4. Attach the bracket]]

 

Mill a groove into the top of the leg to accept the bracket. This can be done with a 3/4" spade bit or auger. Drill into the endgrain no more than an eighth of an inch, centered on the leg. Drill a second hole overlapping the first, and make sure the edge of the hole extends over the inside corner of the leg top. If necessary, chisel out a channel between the two holes and then lay the bracket in the channel. The brackets should point towards the center of the table top.

Attach the brackets to the legs using 1.5 inch #8 screws. Make sure that bracket is oriented such that the ''other'' hole will be countersunk when a screw is passed through it into the bottom of the tabletop.

Once the brackets are attached, turn the top upside down (choose the best surface for the top), and place the rest of the table on top of it. Center to the best of your ability. The table top is oversized to hide any "unsquareness" of the rest of the table. If the unit will not lay flat on the table top, mark the underside of the tabletop where the screws are touching it. This can be done by daubing a little wood putty on the screw head. Remove the unit and drill a small hole no more than a quarter inch deep into the underside of the table top. It helps to wrap a piece of masking tape around the drill bit at the desired depth so the woodworker can stop when the tape reaches the wood. Replace the unit on the table top again.

Drive screws through the brackets into the underside of the table. Again, use #8 screws, but remember that the table top is only 3/4" thick. Play it safe and use 1/2" long screws.

=== Finishing ===
The only thing that remains is to finish the plywood edges and paint (or use a natural finish). Use veneer banding for this, following the instructions on the label. Trim the edges of the veneer off with a carton knife or a chisel. Sand the table and apply two coats of paint or stain and varnish.

If this is a first-time project, the Pathfinder is likely to achieve better results with paint than with stain and varnish. If painting, go back over the piece and cover all screw holes and imperfect shelf joints with wood putty. Woodworking masters eschew wood putty, but it is appropriate for the novice. Wood putty and paint can cover a multitude of woodworking sins!

=== Leveling ===
If the table needs to be leveled, place it on a flat surface such as a workbench or a table covered with hard board or cheap plywood. Have one of the longer legs hang off the edge while the other three are in contact with the flat surface. Use a saw to cut the bottom of the offending leg off by laying the blade on the flat surface and drawing it into the leg. This '''will''' mar the surface of the table unless a "flush cut" saw is used, but executed properly, it is by far the easiest way to level a table or a chair.

==9. Know and use the proper steps in finishing a wood project with either natural finish or stain. ==
The first step in finishing a wood project is to make sure all the surfaces are smooth. This is most commonly done by sanding the surfaces with sandpaper, starting with rougher paper (80-100 grit) and then progressing though successively finer grits (often to 220 grit). Sanding is only necessary if the surface is not already smooth, and some tools (notably planes and cabinet scrapers) will leave a sufficiently smooth surface so that sanding is unnecessary. In fact, sandpaper was patented in the United States in 1834, and woodworking had been going on for millennia prior to that!

The next step in finishing is to remove all dust and dirt from the surface. This can be done by wiping the wood down with a tack cloth, or with a soft cloth which has been wet with mineral spirits. Tack cloth is a soft cloth that has been treated with various finishing compounds (such as mineral spirits and varnish) so that it is slightly sticky or "tacky." It picks up any wood dust it comes into contact with.

Once the surface has been prepared, it can be stained. This can be done by wiping the stain on with a soft cloth (wear vinyl gloves) or with a paint brush. Read the instructions on the can. Staining wood can even out its color. It generally does not fool an experienced woodworker into thinking pine is really walnut or cherry. Staining is optional.

Once the project has been stained (if staining was desired), it can be coated with a finish such as varnish, polyurethane, or tung oil. The purpose of these finishes is to reduce the absorption of moisture. Some finishes do this better than others. Recall that as wood absorbs moisture, its shape changes, so limiting the amount of moisture the project can absorb is a very desirable thing to do.

These finishes are applied again with either a soft cloth (wear gloves!) or a paint brush. You can also buy finishes in spray cans. Several coats are applied, but remember that it is always better to apply several thin coats rather than a few thick ones. Again, read the instructions on the can. Some finishes require that the product dry completely between coats, and others do not.

Make sure the finish is applied in a dust free environment, and do not stir varnish prior to its application, as this will only introduce bubbles which will appear in the finished product. If you do get bubbles, they can be rubbed out between coats with very fine sand paper or with steel wool. The final coat should not be sanded but should rather be polished with a soft cloth.

==10. Do two of the following: ==
=== Make a project with a door or lid with inset hinges. ===
=== Make a scale model of a house or building with a cutaway view showing the interior detail.===

'''One way to do this is to create a 1:20th scale model that looks much as a real house does before it has siding and a roof put on it'''. Use balsa wood, a sharp razor blade, and balsa glue.

Create a house plan (keep it simple). You may use typical houseplans that are available in Houseplan magazines and books or create your own.

In order to achieve greatest accuracy, it is recommended that you draw out the scale model to full size grid-paper. Make sure to mark all doorways, windows, entries, and stairs.

Determine what balsa wood sizes will represent each of the standard stud sizes.

'''Another option''' is to build a doll house out of wood. These are usually 1:12 scale models, and make a great gifts!
Doll House kits are available for sale online.
http://miniatures.about.com/od/dollhousekits/ht/bldkit.htm

'''Purchasing the kit or the balsa wood can be rather expensive'''. Talk with the hobby shop in your town before beginning! They'll probably help you make the wisest financial decisions. This would be a great project to work on as a class or unit!

=== Assist in making and/or repairing wooden toys for needy children. ===
Any toys you make can be included in the packages that are often delivered to needy families during the Pathfinder's Can Collecting activity.

[[Image:Toy_tugboat_illustration.png|250px|right|frame|Tugboat]]
'''Tugboat''' 
An easy toy to make is a small tug boat. This can be made from two pieces of scrap wood and a dowel - dimensional lumber (2x4's) works great for this. The bottom piece makes the boat's hull and deck, and the top layer makes the cabin. Cut the hull to shape with a coping saw and smooth with a rasp. Before cutting the cabin to its final dimensions, drill the hole for the smokestack. It's a lot easier to drill into a large piece of wood than it is to drill into a small piece. You could also clamp the cabin in a vise for drilling. If desired, bore the hole at a slight angle (about 5°) so the smokestack tilts back. Glue the smokestack dowel into the cabin, and glue the cabin onto the hull. If you use a waterproof glue such as epoxy, the glue joint will be strong enough to not require further reinforcement. Otherwise, reinforce the cabin/hull joint with screws through the bottom of the hull into the cabin. Make sure the screw is well recessed so that it does not scratch the floor (or table) when the tug is dragged around. Optionally, you can drill a small hole straight down through the deck near the front of the boat, and drill a larger hole into the hull from the bottom so that it meets the small hole. Pass a rope through the hole and tie a knot in it to keep it from pulling through the smaller of the two holes. It would be easier to use an eye screw, but this may present a choking hazard to small children. Sand well, and finish with colorful paint.

'''Car''' 
Another option is to make Pinewood Derby cars. See the instructions in the [[Adventist Youth Honors Answer Book/Arts and Crafts/Pinewood Derby|Pinewood Derby]] section of the [[Adventist Youth Honors Answer Book/Arts and Crafts|Arts and Crafts]] chapter of this book.

=== Make a project using dowel, miter, or mortise and tenon joints. ===
=== Make a project using curved cuts, or beveled or rounded edges. ===
==About the Author==
{{:About_the_author/Jomegat}}

[[Category:Adventist Youth Honors Answer Book|{{SUBPAGENAME}}]]
[[Category:Adventist Youth Honors Answer Book/Completed Honors|{{SUBPAGENAME}}]]

AY Honors/Renewable Energy/Answer Key

2006-01-04T11:47:12Z

62.171.194.9: /* Water power */

{{Template:Environmental technology}}
'''Renewable energy (sources)''' or '''RES''' capture their energy from existing flows of energy, from ''on-going natural processes'', such as [[solar power|sunshine]], [[wind power|wind]], [[hydro power|flowing water]], [[biomass|biological processes]], and [[geothermal]] heat flows.
The most common definition is that renewable energy is from an energy resource that is replaced rapidly by a natural process such as power generated from the sun or from the wind.

Most renewable forms of energy, other than geothermal and [[tidal power]], ultimately come from the [[Sun]]. Some forms are stored solar energy such as [[rain]]fall and wind power which are considered short-term solar-energy storage, whereas the energy in biomass is accumulated over a period of months, as in [[straw]], or through many years as in [[wood]]. Capturing renewable energy by plants, animals and humans does not permanently deplete the resource. [[Fossil fuel]]s, while theoretically renewable on a very long time-scale, are exploited at rates that may deplete these resources in the near future (see: [[Hubbert peak]]).

Renewable energy resources may be used directly, or used to create other more convenient forms of energy. Examples of direct use are [[solar oven]]s, geothermal heating, and [[watermill|water-]] and [[windmill]]s. Examples of indirect use which require [[energy harvesting]] are [[electricity generation]] through [[wind turbine]]s or [[photovoltaic]] cells, or production of fuels such as ethanol from biomass (see [[alcohol as a fuel]]).

A parameter sometimes used in renewable energy is the [[tonne of oil equivalent]] (toe). This is equal to 10,000 [[Calorie|Mcal]] or 41,868 MJ of energy.[http://www.iea.org/Textbase/stats/unit.asp]

For aspects of renewable energy use in modern societies see [[Renewable energy development]]. For a general discussion, see [[future energy development]].
{{TOCright}}

== Modern sources of renewable energy ==

=== Wind energy ===

{{mainarticle|Wind power}}

As the sun heats up the Earth unevenly, winds are formed. The kinetic energy in the [[wind]] can be used to run [[wind turbine]]s, some capable of producing 5 MW of power. The power output is a function of the cube of the wind speed, so such turbines generally require a wind in the range 5.5 m/s (20 km/h), and in practice relatively few land areas have significant prevailing winds. Luckily, offshore or at high altitudes, the winds are much more constant.

There are now many thousands of wind turbines operating in various parts of the world, with utility companies having a total capacity of over 47,317MW.[http://www.ewea.org/documents/Thefacts_Summary.pdf] Capacity probably means maximum possible output which does not count load factor. It is worth noticing that this number suggests a much higher real percentage of power supply than it really has.

New wind farms and offshore wind parks are being planned and built all over the world. This has been the most rapidly-growing means of electricity generation at the turn of the [[21st century]] and provides a complement to large-scale base-load power stations. Most deployed turbines produce electricity about 25% of the time (load factor 25%), but some reach 35%. The load factor is generally higher in winter. It means that a 5 MW turbine can have average output of 1.7 MW in the best case.

Global winds long-term technical potential is believed to be 5 times current global energy consumption or 40 times current electricity demand. This requires 12.7% of all land area, or that land area with Class 3 or greater potential at a height of 80 meters. It assumes that the land is covered with 6 large wind turbines per square kilometer. Offshore resources experience mean wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy.[http://www.stanford.edu/group/efmh/winds/global_winds.html][http://www.ens-newswire.com/ens/may2005/2005-05-17-09.asp#anchor6] This number could also increase with higher altitude ground based or airborne wind turbines.[http://www.wired.com/news/planet/0,2782,67121,00.html?tw=wn_tophead_2]

There is resistance to the establishment of land based wind farms owing initially to perceptions that they are noisy and contribute to "visual pollution," i.e., they are considered to be eyesores. Many people also claim that turbines kill birds, and that they in general do little for the environment.

Others have argued that they find the turbines beautiful, that turbines out at sea are invisible to anyone on the shore, that cars kill more birds annually and that turbines are continuing to evolve.

Wind strengths vary and thus cannot guarantee continuous power. Some estimates suggest that 1,000MW of wind generation capacity can be relied on for just 333 MW of continuous power. While this might change as technology evolves, advocates have suggested incorporating wind power with other power sources, or the use of energy storage techniques, with this in mind. It is best used in the context of a system that has significant reserve capacity such as hydro, or reserve load, such as a desalination plant, to mitigate the economic effects of resource variability.

[[Wind power]] is renewable and the only direct form of [[greenhouse gas]] mitigation, because it removes energy directly from the atmosphere without producing net [[carbon dioxide]].

=== Water power ===

{{Mainarticle|Water power}}

Energy in water can be harnessed and used, in the form of motive energy or temperature differences. Since water is about a thousand times heavier than air is, even a slow flowing stream of water can yield great amounts of energy.

There are many forms:
* [[Hydroelectric]] energy, a term usually reserved for hydroelectric dams.
* [[Tidal power]], which captures energy from the tides in horizontal direction. Tides come in, raise waterlevels in a basin, and tides roll out. The water must pass through a [[turbine]] to get out of the basin.
* [[Tidal stream power]], which does the same vertically, capturing the stream of water as it is pushed around the world by the tides.
* [[Wave power]], which uses the energy in waves. The waves will usually make large [[pontoon]]s go up and down in the water.
* [[Ocean thermal energy conversion]] (OTEC), which uses the temperature difference between the warmer surface of the ocean and the cool (or cold) lower recesses. To this end, it employs a [[heat engine | cyclic heat engine]].
* [[Deep lake water cooling]], not technically an energy generation method, though it can save a lot of energy in summer. It uses submerged pipes as a [[heat sink]] for [[air conditioning|climate control systems]]. Lake-bottom water is a year-round local constant of about 4 °[[Celsius|C]].

Hydroelectric power is probably not a major option for the future of energy production in the developed nations because most major sites within these nations with the potential for harnessing gravity in this way are either already being exploited or are unavailable for other reasons such as environmental considerations. However, [[micro hydro]] may be an option for small scale applications such as single farms, homes or small businesses.

Building a dam often involves flooding large areas of land, changing habitats, and while hydroelectric energy produces essentially no carbon dioxide, recent reports have linked hydroelectric power to methane, which forms out of decaying submerged plants which grow in the dried up parts of the basis in times of drought. Methane is a potent greenhouse gas.

The other methods of energy generation (and cooling) have had varying degrees of success in the field. Wave and tidal power prove hard to tap, while OTEC has not been field tested on a large scale.

The general public mostly considers water power energy to be renewable.

===Solar energy===

[[Image:Solar_panels_on_yacht_at_sea.jpg|thumb|right|300px|The solar panels (photovoltaic arrays) on this small yacht at sea can charge the 12 V batteries at up to 9 amperes in full, direct sunlight.]]

{{mainarticle|Solar power}}

Since most renewable energy is ultimately "solar energy" this term is slightly confusing and used in two different ways: firstly as a synonym for "renewable energies" as a whole and secondly for the energy that is directly collected from sunlight. In this section it is used in the latter category.
Solar power can be used to:
* generate electricity using [[solar cells]]
* generate electricity using [[Solar power#Solar thermal power plants|thermal power plants]]
* generate electricity using [[Solar Tower|solar towers]]
* heat buildings, directly
* heat buildings, through [[heat pump]]s
* heat foodstuffs, through [[solar oven]]s.

Obviously the sun does not provide constant energy to any spot on the Earth, so its use is limited. Solar cells are often used to power batteries, as most other applications would require a secondary energy source, to cope with outages. Some homeowners use a solar system which sells energy to the grid during the day, and draw energy from the grid at night; this is to everyone's advantage, since power demand for air conditioning is highest during the day.

=== Geothermal energy ===

{{Mainarticle|Geothermal energy}}

Geothermal energy ultimately comes from [[radioactive decay]] in the core of the [[Earth]], which heats the Earth from the inside out, and from the sun, which heats the surface. It can be used in three ways:
* Geothermal electricity
* Geothermal heating, through deep Earth pipes
* Geothermal heating, through a [[heat pump]].

Usually, the term 'geothermal' is reserved for the thermal energy from the core of the Earth.

Geothermal electricity is created by pumping a fluid (oil or water) into the Earth, allowing it to evaporate and using the hot gases vented from the earth's crust to run [[turbine]]s linked to [[electrical generator]]s.

The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such [[geothermal power]] sources exist in certain geologically unstable parts of the world such as [[Iceland]], [[New Zealand]], [[United States]], [[Philippines|the Philippines]] and [[Italy]]. The two most prominent areas for this in the United States are in the [[Yellowstone National Park|Yellowstone]] basin and in northern [[California]]. [[Iceland]] produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.

Geothermal heat from the surface of the Earth can be used on most of the globe directly to heat and cool buildings. The temperature of the crust a few feet below the surface is buffered to a constant 7 to 14 °C (45 to 58 °F), so a liquid can be pre-heated or pre-cooled in underground pipelines, providing free cooling in the summer and, via a [[heat pump]], heating in the winter. Other direct uses are in agriculture (greenhouses), aquaculture and industry.

Although geothermal sites are capable of providing heat for many decades, eventually specific locations cool down. Some interpret this as meaning a specific geothermal location can undergo depletion. Others see such an interpretation as an inaccurate usage of the word depletion because the overall supply of geothermal energy on Earth, and its source, remain nearly constant. Geothermal energy depends on local geological instability, which, by definition, is unpredictable, and might stabilise.

The present consumption of geothermal energy does not in any way threaten or diminish the quality of life for future generations, consequently, it is considered a renewable energy source.

=== Biomass ===

{{mainarticle|Biofuel}}

Plants use [[photosynthesis]] to store solar energy in the form of [[chemical energy]]. Biofuel is any fuel that derives from biomass - recently living organisms or their metabolic byproducts, such as manure from cows. It is a renewable energy.

Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work.
[[Biomass]], also known as biomatter, can be used directly as fuel or to produce liquid [[biofuel]]. Agriculturally produced biomass fuels, such as [[biodiesel]], [[ethanol]] and [[bagasse]] (often a by-product of [[sugar cane]] cultivation) can be burned in [[internal combustion engine]]s or [[boiler]]s.

A drawback is that all biomass needs to go through some of these steps: it needs to be grown, collected, dried, fermented and burned. All of these steps require resources and an infrastructure. However, since the government passed legislation that requires the integration of 7.5 billion U.S. gallons (28,000,000 m³) of ethanol into the gasoline supply experts estimate that six million dollars of investment will be created along with 200,000 additional jobs in the United States.

Biomatter energy, under the right conditions, is considered to be renewable.

==== Liquid biofuel ====
Liquid biofuel is usually bioalcohol such as [[methanol]], [[ethanol]] and [[biodiesel]]. Biodiesel can be used in modern diesel vehicles with little or no modification and can be obtained from waste and crude vegetable and animal oil and fats ([[lipid]]s). A major benefit of biodiesel is lower emissions. The use of biodiesel reduces emission of carbon monoxide and other hydrocarbons by 20 to 40 percent. In some areas [[maize|corn]], [[sugarbeet]]s, cane and grasses are grown specifically to produce ethanol (also known as alcohol) a liquid which can be used in [[internal combustion engine]]s and [[fuel cells]]. Ethanol is being phased into the current energy infrastructure. E85 is a fuel composed of 85% ethanol and 15% gasoline that is currently being sold to consumers.

The EU plans to add 5% [[bioethanol]] to Europe's petrol by 2010. For the UK alone the production would require 12,000 square kilometres of the country's 65,000 square kilometres of arable land assuming that no biofuels are created using waste produces from other agriculture.

==== Solid biomass ====
Direct use is usually in the form of combustible solids, either firewood or combustible field crops. Field crops may be grown specifically for combustion or may be used for other purposes, and the processed plant waste then used for combustion. Most sorts of biomatter, including dried manure, can actually be burnt to heat water and to drive turbines.

[[Sugar cane]] residue, [[wheat]] chaff, [[maize|corn cobs]] and other plant matter can be, and is, burnt quite successfully. The process releases no net CO2.

Solid biomass can also be [[gasification|gasified]], and used as described in the next section.

==== Biogas ====
{{mainarticle|biogas}}
Many organic materials can release gases, due to metabolisation of organic matter by bacteria ([[fermentation]]). [[Landfills]] actually need to release this gas to prevent dangerous explosions. Animal feces releases methane under the influence of [[anaerobic bacteria]].

Also, under high pressure, high temperature, [[anaerobic]] conditions many organic materials such as wood can be [[gasification|gasified]] to produce gas. This is often found to be more efficient than direct burning.
The gas can then be used to generate electricity and/or heat.

Biogas can easily be produced from current waste streams, such as: paper production, sugar production, sewage, animal waste and so forth. These various waste streams have to be slurried together and allowed to naturally ferment, producing methane gas. We just need to convert current sewage plants to biogas plants, build more locally centered smaller biogas plants and plan for the future. Biogas production has the capacity to provide us with about half of our energy needs, either burned for electrical productions or piped into current gas lines for use. It just has to be done and made a priority. Besides, when a plant has extracted all the methane it can, we are left with a better fertilizer for our farms than we started with.

== Small scale energy sources ==
There are many small scale energy sources that generally cannot be scaled up to industrial size. A short list:
* [[piezoelectricity|Piezo electric]] crystals generate a small voltage whenever they are mechanically deformed. Vibration from [[internal combustion engine|engines]] can stimulate piezo electric crystals, as can the heels of shoes
* Some watches are already powered by kinetics, in this case movement of the arm
* [[Electrokinetics]] generate electricity from the kinetic energy in water that is pumped through tiny channels
* Special [[antenna (electronics)|antennae]] can collect energy from stray radio waves or theoretically even light ([[Electromagnetic radiation|EM radiation]]).

== Issues ==
=== Aesthetics, habitat hazards and land use ===
Some people dislike the aesthetics of [[wind turbines]] or bring up nature conservation issues when it comes to large solar-electric installations outside of cities. Some people try to utilize these renewable technologies in an efficient and aesthetically pleasing way: fixed solar collectors can double as noise barriers along highways, roof-tops are available already and could even be replaced totally by solar collectors, [[photovoltaic cell|amorphous photovoltaic cells]] can be used to tint windows and produce energy etc.

Some renewable energy capture systems entail unique environmental problems. For instance, wind turbines can be hazardous to flying birds, while hydroelectric dams can create barriers for migrating fish - a serious problem in the Pacific Northwest that has decimated the numbers of many salmon populations. Burning biomass and biofuels causes air pollution similar to that of burning fossil fuels, although it causes a lower greenhouse effect since the carbon placed in the atmosphere was already there before the plants were grown, rather than being "new" carbon from fossil fuels .

Another problem with many renewables, especially biomass and biofuels, is the large amount of land required, which otherwise could be left as wilderness.

=== Concentration ===
Another inherent difficulty with renewables is their variable and diffuse nature (the exception being [[geothermal energy]], which is however only accessible in exceptional locations). Since renewable energy sources are providing relatively low-intensity energy, the new kinds of "power plants" needed to convert the sources into usable energy need to be distributed over large areas.

Electrical power consumption in Western countries averages about 100 watts per person (i.e. about 1 MWh per year). In cloudy [[Europe]] this would require about eight square meters of [[solar panel]]s, assuming a below-average solar conversion rate of 12.5%. Systematic electrical generation requires reliable overlapping sources or some means of [[grid energy storage|storage]] on a reasonable scale ([[hydroelectricity|pumped-storage hydro system]]s, batteries, hydrogen [[fuel cell]]s, etc). So, because of current costs of such energy storage systems, a stand-alone system is only economic in rare cases, or where a connection to a public grid would be impractical.

=== Proximity to demand ===
The geographic diversity of resources is also significant. Some countries and regions have significantly better resources than others in particular RE sectors. Some nations have significant resources at distance from the major population centers where electricity demand exists. Exploiting such resources on a large scale is likely to require considerable investment in transmission and distribution networks as well as in the technology itself.

=== Availability ===
One recurring criticism of renewable sources is their intermittant nature. Solar insolation, for example can only be expected to be available during the day (50% of the time). Wind energy is somewhat more available, while geothermal and wave energy are available all of the time, although the intensity of the waves varies season to season. A wave energy scheme installed in Australia is generating electricity with an 80% availability factor.

=== Fossil fuels ===
{{mainarticle|Fossil fuel}}
Renewable energy sources are fundamentally different from fossil fuel or nuclear power plants because the Sun will 'power' these 'power plants' (meaning sunlight, the wind, flowing water, etc.) for the next 4 billion years. They also do not directly produce greenhouse gases and other emissions, as fossil fuel combustion does. Most do not introduce any global new risks such as [[nuclear waste]].

Fossil fuels are not considered a renewable energy source, but are often compared and contrasted with renewables in the context of [[future energy development]].

The traditionally, though not universally, held Western (biogenic) theory postulates that fossil fuels are the altered remnants of ancient plant and animal life deposited in sedimentary rocks. They were formed millions of years ago and have rested underground, mostly dormant, since that time.

In contrast, the [[Abiogenic petroleum origin]] theory states that [[petroleum]] (or [[crude oil]]) is primarily created from non-[[biology|biological]] sources of [[hydrocarbon]]s located deep in the [[Earth]]. This view was championed by [[Fred Hoyle]] in his book ''The Unity of the Universe''.

Though it is possible to produce complex [[hydrocarbons]] artificially by using the [[Fischer-Tropsch process]], this process does not generate energy, and cannot be considered a large scale solution to the energy problem.

The coal industry in the US is publicly claiming coal is renewable energy because the coal was originally biomass. However, the biomass of fossil fuels was produced on the time scale of millions of years through a series of events and it is considered to be a deposit of energy, not an energy flow. Some scientist hold the view that the formation of fossil fuels was a one-time event, made possible by unique conditions during the [[Devonian]] period, such as increased oxygen levels and huge swamps.

When the term renewable was introduced (see [[Renewable energy#Defining renewable|Defining renewable]] within this article), it was a generally held belief that the Earth's sources would be depleted within some 50 years. Since then, large deposits of deep-Earth oil have been found, which has extended this timetable. Because the current rate of consumption exceeds the rate of renewal (if, indeed, there is renewal of fossil fuels), the Earth will eventually run out of fossil fuels (''see [[peak oil]]'').

=== Transmission ===
If renewable and [[distributed generation]] were to become widespread, [[electric power transmission]] and [[electricity distribution]] systems might no longer be the main distributors of electrical energy but would operate to balance the electricity needs of local communities. Those with surplus energy would sell to areas needing "top ups". That is, network operation would require a shift from 'passive management' - where generators are hooked up and the system is operated to get electricity 'downstream' to the consumer - to 'active management', wherein generators are spread across a network and inputs and outputs need to be constantly monitored to ensure proper balancing occurs within the system. Some Governments and regulators are moving to address this, though much remains to be done. One potential solution is the increased use of active management of electricity transmission and distribution networks. This will require significant changes in the way that such networks are operated.

However, on a small scale, use of renewable energy that can often be produced "on the spot" lowers the requirements [[electricity distribution]] systems have to fulfill. Current systems, while rarely economically efficient, have proven an average household with a solar panel array and energy storage system of the right size needs electricity from outside sources for only a few hours every week. Hence, advocates of renewable energy believe electricity distribution systems will become smaller and easier to manage, rather than the opposite.

== Historical usage of renewable energy ==
Throughout history, various forms of renewable and non-renewable energies have been employed.

*[[Wood fuel|Wood]] was the earliest manipulated energy source in human history, being used as a thermal energy source through burning, and it is still important in this context today. Burning wood was important for both [[cooking]] and providing heat, enabling human presence in cold climates. Special types of wood cooking, [[drying (food)|food dehydration]] and [[smoking (food)|smoke curing]], also enabled human societies to safely store perishable foodstuffs through the year. Eventually, it was discovered that partial combustion in the relative absence of oxygen could produce [[charcoal]], which provided a hotter and more compact and portable energy source. However, this was not a more efficient energy source, because it required a large input in wood to create the charcoal.
*[[Animal power]] for vehicles and mechanical devices was originally produced through [[animal traction]]. Animals such as horses and oxen not only provided transportation but also powered mills. Animals are still extensively in use in many parts of the world for these purposes.
*[[Water power]] eventually supplanted animal power for mills, wherever the power of falling water in rivers was exploitable . Water power through [[hydroelectricity]] continues to be the least expensive method of storing and generating dispatchable energy throughout the world. Historically as well as presently, hydroelectricity provides more renewable energy than any other renewable source.
*[[Animal oil]], especially [[whale oil]] was long burned as an oil for light.
*[[Wind power]] has been used for several hundred years. It was originally used via large sail-blade [[windmill]]s with slow-moving blades, such as those seen in the [[Netherlands]] and mentioned in [[Don Quixote]]. These large mills usually either pumped water or powered small mills. Newer windmills featured smaller, faster-turning, more compact units with more blades, such as those seen throughout the [[Great Plains]]. These were mostly used for pumping water from wells. Recent years have seen the rapid development of wind generation farms by mainstream power companies, using a new generation of large, high wind turbines with two or three immense and relatively slow-moving blades. Today, wind power is the fastest growing energy source in the world.
*[[Solar power]] as a direct energy source has been not been captured by mechanical systems until recent human history, but was captured as an energy source through architecture in certain societies for many centuries. Not until the twentieth century was direct solar input extensively explored via more carefully planned architecture (passive solar) or via heat capture in mechanical systems (active solar) or electrical conversion (photovoltaic). Increasingly today the sun is harnessed for heat and electricity.
*Attempts to harness the power of [[Wave power|ocean waves]] appears in drawings and patents back to the 19th century. Modern attempts to capture wave power began in the 1970's by Professor Steven Salter who started the Wave Energy Group at the University of Edinburgh in Scotland. There are several pilot plants generating power into the grid, and many new and curious designs are in various stages of development and testing.

== See also ==

{{Wikinews|:Category:Energy}}

* [[Action on Climate Change]]
* [[Ashden Award]] for Renewable Energy
* [[Battery electric vehicle]]
* [[Carbon sequestration]]
* [[EU Intelligent Energy]]
* [[European Union Climate Change Programme]]
* [[Electric boat]]
* [[Future energy development]]
* [[Green car]]
* [[Mitigation of global warming]]
* [[Net energy gain]]
* [[Nuclear power phase-out]]
* [[Renewable energy development]]
* [[Renewable energy links]]
* [[Soft energy path]]
* [[Sustainable energy]]
* [[Wind power]]

== External links ==
* [http://eosweb.larc.nasa.gov/sse Surface meteorology and Solar Energy - a renewable energy resource for data and images]
* [http://www.greenmountain.com Green Mountain Energy]
* [http://www.renewableenergyaccess.com Renewable Energy News from around the world]
* [http://www.futurecrisis.com/alternative-energy-plans.php Renewable Energy Projects and Daily News]
* [http://energia.co.nr/ Renewable Energy Projects (site in spanish)]
* [http://www.cus.net/ Renewable Energy]
* [http://groups.yahoo.com/group/worldoilboycott World Oil Boycott Grassroots Organization]
* [http://www.greenprogress.com/alternative_energy.php Green Progress - alternative energy news]
* [http://www.solardrome.com SolarDrome Renewable Energy from Around the Web]
* [http://www.greenfuelonline.com/enterprise4.htm Technology turns greenhouse gas emissions to clean air biofuels]
* [http://www.ief-energy.org/ International Energy Foundation]
* [http://www.inboxrobot.com/news/AlternativeEnergy Alternative Energy newsletter for Research Professionals]
* [http://www.nrel.gov/ National Renewable Energy Laboratory (American)]
* [http://www.GenomeNewsNetwork.org/categories/index/energy.php Genome News Network (GNN) Energy News] Collection of articles about how advances in genomics is leading to advances in energy production.
* [http://www.cat.org.uk/ Centre for Alternative Energy (European)]
* [http://www.activistmagazine.com/index.php?option=content&task=view&id=120 Carbon Activism for Beginners].
* [http://www.ecoresearch.net/election2004/report/sentence?s=1 Renewable Energy Media Analysis] — US Election 2004 Web Monitor
* [http://europa.eu.int/comm/energy/intelligent/index_en.html EU Intelligent Energy], [[energy efficiency]] and [[renewables]].
* [http://www.ademe.fr/ French Agency for the Environment and Energy Management], fields of activity : air quality, wastes, energy-efficiency and renewables, environmental management, polluted soils, transportation
* [http://www.itdg.org/ Intermediate Technology Development Group]
* [http://www.thehydrogenexpedition.com/ The Hydrogen Expedition] Renewable energy world record
* [http://www.aapg.org/explorer/2002/11nov/abiogenic.cfm Abiogenic Gas Debate] On the possible abiogenic origin of fossil fuels
* [http://wiki.greenpowered.org Green Wiki] Collective articles on renewable energy and other topics related to sustainable living
* [http://energy.sourceguides.com/index.shtml The Source for Renewable Energy] A directory to more than 9000 renewable energy businesses worldwide
* [http://environmental-finance.com Environmental Finance magazine]
* [http://climatechangeaction.blogspot.com/2005/09/energy-efficiency-vs-small-scale.html Renewables vs Energy Efficiency] Where should i spend my money if i want to have a low carbon home?
* [http://europa.eu.int/comm/energy/res/index_en.htm European Union website about renewable energy]
* [http://www.rengen.info/?p=6 The wide world of renewable energy]

== References ==
*[http://eia.doe.gov/ U.S. Energy Information Administration] provides a wide range of statistics and information on the industry.
*Boyle, G. (ed.), ''Renewable Energy: Power for a Sustainable Future''. Open University, UK, 1996.
*[http://www.eere.energy.gov/ U.S. DOE Energy Efficiency and Renewable Energy (EERE) Home Page]

[[Category:Climate change]]
[[Category:Renewable energy| ]]
[[Category:Sustainability]]

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[[he:אנרגיה חלופית]]
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