Sources

For most applications methane is overrated. If you run a dairy or a sewer plant, you might have enough biomass to do some good, but for the rest of us, it is a poor use of effort.

Wind varies widely in energy and availability. If you have the misfortune of living in a windy environment, you might console yourself with the use of this source. On the plus side, the amount of energy in wind increases with the cube of the velocity, so it can be a valuable resource.

Solar, although cyclic, is far more predictable. Solar cells can give you about 10% of the sun's energy in the form of electrical power. If it has to be converted to another voltage, it will lose a bit – likely at least 25% (of the 10% collected). If stored in batteries for later use, it will lose more in charging and discharging the batteries.

Panels that collect heat can deliver 70% and more, which can be efficiently stored for later use. The efficiency of focusing collectors varies widely with design and application.

Fire -- Wood and other biomass is a more versatile source that can be efficiently stored and produce energy on demand. It goes without saying that reliance upon this source requires intentionally planting trees for an ongoing energy supply.

The Perpetual Motion of Fools I am frequently amazed at how otherwise intelligent people tout energy sources they cannot document.

Applications

Keeping warm: There's more to this than heat.

Alternative engines can be powered by heat from any source.

Electrical power can be efficiently derived from mechanical power.

Lighting is available from electrical power or flames

Refrigeration can be produced in a number of ways

The Energy Tree

As you scan the headings and subheadings in the list below, consider their benefit in a locally sustainable infrastructure. These are real processes achievable through heat. Links to many of them (some redundant) are embedded in this outline.

Space heating

Cooking

Hot water

----Convection space heating (old technology radiator)

----Cooking, bathing, etc.

----Heat storage in hot tub or tank

Steam

--Mechanical energy (steam engine)

------Shop power

------Electrical energy

----------Lighting

----------Appliances

----------Shop power

--Cleaning

--Pest control (cockroaches hate getting scalded)

Kiln or high temperature oven

--Ceramics

------Basic kitchen implements

------Special purpose bricks, etc.

------Stove parts

------Machine parts

------Tiles

----------Floors

----------Counters

----------Pools

------Vacuum chamber construction

----------Aluminize surfaces

--------------Mosaic for solar energy collector

--------------Lighting reflectors

--------------Reflective optics

----------Drying of foods, etc

----------Chemical separation processes

--Glass blowing

------Recycling broken or discarded glass

------Artistic creations

------Kitchen containers

------Chemical process hardware and storage

--Forge for blacksmithing steel

------Custom steel parts

------Custom tools

------Welding

--Metal casting

------Lead, Aluminum, pot metal

------Precious metals

------Copper, bronze

--Refining of certain ores

--Desiccant drying

------Heat retrievable through adding water

----------Portable stored heat

----------Transportation fuel

----------Camping comfort

------Drying vegetables and fruits, and other things

--Pyrolisis of wood or biomass (Over 40% of energy in wood is gas)

------Charcoal production and reactivation

----------Filtering

----------Clean fuel for cooking and heating

------Petrochemical replacement

----------Cooking gas

----------Internal combustion engine fuels, both liquid and gas

----------Bases for paints, solvents, plastics, varnishes, etc.

--Pyrolisis of bone and calcium based minerals

------Cement

------Plasters and related compounds

--Charge thermal storage for remote usage

------Solid thermal mass

------Desiccant or other thermal reversible processes

------Phase change thermal storage (such as eutectic systems)

Non-steam heat engines

--Forced air heating

--Shop power

--Electrical generation

For further discussion see The World We Face (and what to do about it)

Conservation

A sustainable lifestyle should depend upon as little energy as possible. Structures should be well insulated, and conservative in size. Lighting should be focused, and strategically placed. An efficient community design would minimize transportation needs.

Energy should be produced as close to its point of use possible. Small distributed systems should be optimized. Timing is another factor; plan the use of energy so that it will achieve as much as possible within the time it is being used.

Whenever energy is changed from one form to another there are losses. Electrical heating is convenient, but if thermal energy has been converted to mechanical energy to produce electrical energy, most of the original thermal energy is lost. It is obviously much better to use thermal energy directly whenever possible.

Sometimes thermal energy can be scavenged from high-intensity applications – for instance: Exhaust from a cooking fire or motor may still have enough heat left over to heat water for washing dishes or bathing.

Storing energy

Energy from solar collectors that heat air has commonly been stored in insulated bins of rocks. Fluid-based solar heating systems commonly rely on tanks of water.

There is also a category of thermal storage that involves the use of a “eutectic”; a eutectic often refers to anything that can be melted and frozen. The advantageous property of a eutectic is that it stores and yields a lot of energy when changing from one phase to another. The most commonly used material in this category is water. Ice keeps your drink at a constant low temperature until the last of it has melted (or frozen).

During a period of inadequate employment I worked as a security guard (I’ve decided I’ll never get around to writing my book titled “The Adventures of Rent-a-Pig”), My beat sometimes involved sitting still in a pickup truck for hours at a time in Colorado winter nights. Paraffin melts at about 140 degrees F, and remains at about that temperature until it re-freezes. I filled a gallon can with paraffin, melted it by putting the can in boiling water (houses have burned down because people were melting containers of paraffin directly over the fire), wrapped it in an old blanket, and used it as a foot-warmer during my watches. One tricky thing about paraffin however it that it expands and contracts a lot as it melts and freezes. So the cap should not be on the can while heating, and needs to be loosened periodically while cooling.

There are also chemical reactions that can store heat. Calcium chloride for instance has a powerful attraction for water molecules. When it is heated enough to drive out all the water and then allowed to cool, it will produce significant heat when re-exposed to moisture. I know of at least one commercial thermal storage system based upon this principle. There are commercially available hand-warmers that are activated by allowing two chemicals to mix.

Batteries have been here longer than any of us, but there is a price to pay. A lead-acid battery that is about 70% charged may store over 80% of the charging current. By the time it’s 90% charged however, the charging efficiency will drop off to about 60%. Varying efficiency losses are unavoidable with any battery technology. Another problem with batteries is that they typically last only a few years. Replacing a massive bank of batteries is an ecological and financial disaster.

Compressed air stores energy proportional to the square of the pressure. Years – decades – ago I read of a go-cart powered by a modified air-hammer. The claim was that with a tank of nitrogen pressurized to the obscene extreme of twenty thousand PSI (I have never heard of such pressures, and frankly remain skeptical), it had a theoretical range of 600 miles.

The problem with compressing air or any other gas is that the temperature increases with the pressure. So right off the bat you lose energy in the form of heat when you allow it to return to ambient temperature. The interesting side of this is that as you allow the pressure to escape while yielding mechanical energy, it also cools. Those of us who have used jackhammers or other air-powered equipment are familiar with the frost build-up that can occur; if you happen to want a refrigerator however, you’re in luck.

While speaking of compressed air (though not directly related to storing heat), there is an incredible fire-starting device discovered in occasional use in Southeast Asia called a fire-piston. A close tolerance stick sealed by greased winding of thread was fitted into a precision hole about three inches deep (the stick and hole were about 3/8” diameter).

There was a shallow hole in the inside end of the stick that held tinder. When the piston was forcibly plunged down the cylinder and immediately withdrawn, the air (heated to about 800F) ignited the tinder. A traveler from Europe observed a Philipino using one to light a cigarette and traded him a Zippo lighter and some bubble-gum for it. Some believe that this was the original inspiration for the diesel engine. I have not yet successfully built one of these – a little smoke, but so far no fire.