Brick and solid walls can absorb heat during the day and then radiate the heat to keep a house warm at night.
IT’S ENERGY THAT MATTERS |
15 |
ENERGY IS ESSENTIAL TO ALL LIFE. We rely on the Sun to drive all ecosystems on Earth and we eat food simply to obtain energy for us to function. Light and heat energy are commonly known as these are provided by the Sun, but there are many other forms of energy that include chemical, potential, mechanical, sound, gravitational, electric and kinetic.
Some of these energy types are directly and indirectly discussed here as we look at how we can use natural energies to live better and smarter.
Whenever we need to make decisions about energy we should undertake an energy analysis. We need to consider the embodied energy of materials and their life cycle assessment.
Embodied energy is the energy used in the production of a building, a product or some other structure. The amount of energy used in the manufacture of these materials can be a significant component of the life cycle impact of a home, for example. While it is important to improve the energy efficiency of any building, the amount of embodied energy it contains can be equivalent to many years of its operation.
The importance of embodied energy, and the environmental impacts of using some particular building materials, only becomes apparent when we examine the materials from a life cycle approach, usually known as Life Cycle Assessment (LCA).
LCA examines the total environmental impact of a material through every step of its life — from obtaining raw materials to using it in your home and then disposal or recycling. LCA can consider impacts such as resource depletion, energy and water use, greenhouse emissions and waste generation.
The amount of embodied energy varies with different construction types. A higher embodied energy level can be justified if it contributes to a lower operating energy. For example, large amounts of thermal mass, high in embodied energy, can significantly reduce heating and cooling needs in well-designed and insulated passive solar houses.
You could further reduce the embodied energy of the thermal mass if you used concrete made from recycled building material, such as crushed concrete, rock or bricks, for the aggregate.
Generally, the more highly processed a material is, the higher its embodied energy. For example, plastics have much higher embodied energy than sawn timber, aluminum window frames much more than wooden window frames, and clay bricks much more than stabilized earth. In fact, for every square foot of wall, a cement-stabilized rammed earth home has less than half the embodied energy of a double clay brick home.
There are also other considerations when choosing particular building products. For example, high monetary value, high embodied energy materials, such as stainless steel and aluminum, will almost certainly be recycled many times, reducing their life cycle impact. Furthermore, comparing the energy content per square foot of construction is easier for designers than looking at the energy content of all the individual materials used.
It doesn’t take too much effort to save energy or to reduce the energy we consume in our daily lives. We can also adopt simple technologies that rely more on human power than on fossil fuel power.
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Recycling 20 aluminum cans uses the same amount of energy required to make one new can from raw materials. Recycling 1 t of steel saves 1.1 t of iron ore, 1,320 lb of coal and 120 lb of limestone. Recycling newspapers for one year can save enough electricity to power a four-bedroom house for four days. The reuse of building materials commonly saves about 95% of the embodied energy that would otherwise be wasted.
We are all aware that the energy we currently obtain from fossil fuels is finite — it will run out one day. Renewable energy is our best option for electricity production in our future, but it has limited application to make a car work all day, every day.
As petroleum becomes scarce there will be major issues with every aspect of transport. As an individual there are some things you can do now to reduce the overall consumption of fossil fuels. Here is a list of 20, but I am sure you could think of lots more:
• Carpool. Join others on shared journeys to the office or shops.
• Take public transport. Reduce your car use by taking public trains, buses, ferries and trams.
• Bicycle. For short distances use a bicycle, even an electric one.
• Buy an electric car, or convert your current vehicle to run on solar power and batteries.
• Choose energy-efficient appliances and white goods, including low wattage light bulbs. Look for the energy rating — choose those that have the most stars.
• Install water-efficient devices and fixtures (such as taps, showerheads, washing machines, toilets) — this reduces the amount of energy government and private agencies use to treat and pump water to your house.
• Double-glaze windows. This can be as simple as putting a film over the glass window panes.
• Switch off appliances on standby — turn off completely when not in use.
• Set the thermostat for any heating and cooling devices to at least two degrees warmer in summer and two degrees cooler in winter.
• Follow the principle of passive solar design for your house as outlined earlier, such as: draft-proof doors and windows, shade windows that are receiving direct sunlight in summer, install insulation in the roof space and incorporate garden structures to help with heat control.
• Adjust your refrigerator setting to be a little warmer, and the hot water system to be a little cooler.
• Wash only full loads in the washing machine. Use a cold water setting rather than hot water for the wash.
• Turn off lights in rooms that you are not using. It is a myth that you use more power turning lights on and off rather than just leaving them on all the time. Flick the switch as you leave the room.
• Install solar tubes or skylights in rooms that are naturally dark, even in the daytime.
• See if you can do without that second fridge on the veranda or at least turn it off until you really have to use it.
• Close all external doors and windows when the heater or air conditioner is running.
• When you have to replace your water heater, install a solar hot water system with a gas booster, a conventional heat pump or better still, a ground-source heat pump or a heat pump that uses solar water collectors to preheat the water.
• Insulate all exposed hot water pipes with lagging or some type of insulation to reduce heat loss.
• Turn a ceiling or stand-alone fan on rather than switching on the air conditioner.
• If wood is readily available use it in a stove to cook food or in a room heater.
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When compared to top-loading washing machines, front-loading machines use 50% less water, 40% less energy and up to 50% less detergent.
Energy-efficient or passive solar houses save both money and the environment. Passive solar means that the Sun’s energy is used to heat and cool a home without the use of pumps, fans, air conditioners, wood stoves and other devices to keep us warm or cool. A carefully planned house can be built that will be 10–20°F warmer in winter and at least 15°F cooler in summer.
In a climate-sensible or passive solar design of a house there are six key principles. The optimum living conditions and comfort will be found in houses that contain some combination of these principles when they are designed and built. These principles can be remembered by the acronym TO VIEW — thermal mass, orientation, ventilation, insulation, external influences and window placement. Most of these principles are well documented and generally well known, but here is a brief summary of each.
Certain materials have the ability to store heat. Heavier, dense materials such as concrete, stone, slate and bricks have a high heat capacity per unit volume to store heat. Houses made from brick, rammed earth or concrete have generally more stable temperatures than houses made of timber, plaster or metal, which tend to heat up and cool down quickly.
Dark surfaces are also better at absorbing and radiating heat than lighter materials. Dark slate and tiled floors can absorb winter sunlight during the day and then slowly radiate or give off this heat into the room at night to maintain a constant level of comfort.
Brick and solid walls can absorb heat during the day and then radiate the heat to keep a house warm at night.
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Black objects are the best absorber and radiator of heat. White-colored surfaces are the best reflectors of sunlight and heat. While dark-colored surfaces do absorb heat faster than lighter surfaces, they also give off this heat quicker, and thus cool down faster.
The correct orientation of your house takes advantage of the Sun’s movement during the day and throughout the different seasons of the year, and a good design would consider the Sun’s lower position in the sky in winter and a much higher position in summer.
Eaves can shade summer sun but allow winter sunlight to enter a room.
Houses that are rectangular and about twice as long as wide with the long axis stretching east-west tend to remain warmer in winter and cooler in summer. This is because more surface area (walls) face the winter Sun and so can absorb heat. During the summer there is minimum wall exposure to the Sun in the morning and afternoon and this reduces heat absorption, keeping the house a little cooler.
Eaves are an important design feature for houses built in warmer climates. Eave size or overhang can be as little as 20–30 in on the sun-facing side to sufficiently shade walls in summer. More protection is warranted on the east and west sides, so eaves can be larger or verandahs and trellises can be used to shade these sides.
Eaves are not so important for houses in colder climates where there could be too much shading or snow accumulation on the roof.
The correct placing of windows ensures good cross-ventilation of cooling breezes. Harvesting and directing breezes in summer can effectively cool the house down without the additional use of air conditioners.
During winter, doors in unused rooms should be closed and any gaps under the door sealed, as leaky buildings lose considerable heat.
Ventilation of the roof space should also be considered. Roof ventilation will allow insulation to work more effectively by allowing hot air a means to escape. However, vents should be closed in winter and cold weather to retain heat.
A range of materials can be used to insulate your home and prevent heat transfer. Heat is easily lost and gained through walls and ceilings, so at least these should be insulated. Solid walls transfer heat and cold, so building cavity-walled houses enables either air or some other material to be placed in the cavity to reduce thermal conductivity.
Common insulating materials include glasswool (fiberglass) and rockwool batts, cellulose fiber, reflective foils and polystyrene foam. Glasswool and rockwool do not burn whereas polystyrene does. Cellulose fiber insulation is often made from recycled newspaper but is mostly treated with chemicals to prevent it from burning too.
Ideally, walls, floors and ceilings should be insulated.
Many of these insulating materials trap air. Air is a good insulator and it helps prevent heat from passing through a material. Reflective foils work differently as they reflect heat either away from a house or back into a room. Insulation can also act as soundproofing, and different materials have different abilities to reduce the intensity of sound passing through.
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Insulating materials are given an “R” rating, which is a measure of thermal resistance. The higher the R value the better the resistance to heat flow. Higher R value materials should be used in areas that experience severe weather such as excessive heat or cold.
There are two aspects of external influences: integrated gardens, and house and garden structures, such as verandas, trellises and pergolas.
Few architects and designers consider integrated gardens, which can be effective in moderating house temperatures. Many people may not realize that gardens can be designed to take an active role in the heating and cooling of the house.
For example, deciduous trees and tall shrubs should be planted to allow winter light to pass into rooms while shading the house during the summer. Remember that protecting walls from direct heat radiation will lower the overall temperature of the house.
The positioning of shrubs and trees is important for the success of this strategy. The low winter Sun can cast long shadows while in summer, the Sun, which is higher in the sky, produces shorter shadows. You will need to consider the height and spread that trees usually attain to know where to plant them.
Shrubs and trees can also perform other functions. Plants can be positioned to deflect cold or hot winds from the house by acting as screens and windbreaks. Creepers and climbers can grow on a frame or the wall itself on the western side. Plants can absorb heat and prevent heat radiation from reaching the wall, keeping that side of the house cool.
Plant deciduous trees on the Sun-facing side of the house.
The nature of the tree foliage may also be important. Light-colored, shiny leaves will reflect light onto house walls, adding heat during winter, while dark leaves tend to absorb heat, rather than reflecting it onto surfaces.
Metal or wood blades, spaced apart at an angle, can shield summer sunlight or direct winter sunlight into the house.
Garden structures can also be used for temperature control. A hothouse or greenhouse attached to the sun-facing wall can provide winter heating for the house as well as being used to grow food. Vents will control the direction of heat. In summer, the hothouse roof should be vented at all times to limit unwanted heat transfer to the inside of the house. In winter, other vents can be opened to direct warm air into the home.
Similarly, a shadehouse on the opposite side of the house helps with cooling in summer. Breezes passing through a moist shadehouse on that side of a house can be cooled. This cooler air can be vented throughout the house by opening and closing windows and doors. Any air blowing across pools or ponds is usually cooled in this way before it reaches the house.
Verandas, pergolas and trellises are common garden and house structures that are used to shade walls. Horizontal trellises and pergolas should be placed on the sun-facing and western sides of a house to increase the summer shading of walls. Vertical trellises are more appropriate along western walls.
Water has a high heat capacity and can store energy.
One variation of the standard pergola is the sun-controlled pergola. This is a structure that has blades set at a particular angle so that only winter sunlight can pass through.
The blades of the sun pergola can be made of metal or timber. With the correct angle and spacing of the blades you will be able to get the maximum winter sunlight to enter the house while completely shielding the roof during summer.
Trellises can either be covered with deciduous vines or shadecloth for summer shading. Being able to remove or retract the shadecloth in winter will allow additional winter heating of house walls.
Even a rainwater tank attached to a wall also helps moderate the heating of a house. The tank should be able to absorb winter sunlight but be completely shaded in summer.
Water can hold lots of heat, which can be slowly radiated and transferred through walls into rooms.
Integrating our garden with the house is an important concept that is often underrated as a means to moderate the effect of temperature and climate extremes.
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Three main pigments in the leaves of deciduous trees become the colors of autumn. Carotenoids are responsible for the yellow hues of the season as well as the coloration of carrots, corn, daffodils, and bananas.
Anthocyanins are responsible for the red, scarlet, blue and purple hues in nature. They comprise the characteristic colors of cranberries, blueberries, red apples, cherries, strawberries and plums.
Tannins are the third prominent pigment, and these cause the brown tones to the leaves, especially those of the oak and elm. After the carotenoids and anthocyanin have decomposed, the tannins alone remain, giving the dead leaves their characteristic brown color.
The size and placement of glass doors and windows is an important passive solar design principle. Heat is easily lost or gained through glass or by the action of winds.
In a climate-sensible house, windows are placed on particular sides of the house to exploit cooling breezes and to facilitate good cross-ventilation.
Generally, rooms on the west and east sides should have the minimum number of windows, and these should also be small or shaded by trees and verandas.
Correctly placed windows will allow additional sunlight into rooms.
Sometimes about half of a sun-facing wall could be glass to let winter light into the room. As long as the eave overhang is sufficient the summer sun will be screened out. However, too much glass may result in excessive heat loss in winter and too little may mean not enough sunlight is absorbed into rooms.
Sides of the house that are always shaded (south in southern hemisphere, north in northern hemisphere) will tend to be the coldest. Here, double glazing may be helpful. Double glazing (two layers of glass) is common in colder areas of the world as this reduces heat loss from the house.
Window protection is also important to prevent heat transfer. Curtains, reflective foil, tinting, blinds, awnings and shutters can be used effectively to shade glass.
When nighttime approaches, or during hot summer days, curtains and protective covers can be drawn to reduce heat loss or sunlight penetration.
Everyone can make a difference. Everyone has the opportunity to make energy conservation a part of their daily lives. Remember, it is not more expensive to build an energy efficient home, but it does take careful planning.
It is always better and cheaper to make changes to house plans prior to building than to retrofit an existing home to make it energy efficient.
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In winter, heat is easily lost in poorly designed homes. Heat loss due to air leaks is about 20%, through walls and ceilings about 50%, and floors and windows 30%. On a typical house, ceiling insulation can save about 25% of heating costs, and wall insulation a further 14%.
Water and space heating are usually the largest consumers of energy in a house, accounting for about 27% and 42% respectively of an average household energy bill. Consequently, the type of water and space heating used in a dwelling has a considerable influence on energy costs and associated green house gas emissions. If Australians were to cut their greenhouse gas contribution by only 1%, then greenhouse gas emissions would be reduced by 1 million tonnes each year.
Active solar systems have to use pumps to move air or water, or power to operate motors and controllers. While the sun is involved in heating the water in a solar hot water system, for example, energy is used by a pump to transfer water to a storage tank, which is often on the ground.
A simple heat exchange system where a hot coil sits inside a cool water tank is a good way to link a low pressure heating system (such as the solar water panels in the diagram opposite or from the water jacket in a slow combustion stove) to a high pressure house supply system.
Active systems may use a pump to circulate water or air.
Some solar electricity panels (photovoltaics) are mounted as an array and can move to “track” the sun. While some of these devices rely on passive heating of gases to move the array, other devices use small amounts of electricity to drive a motor to turn the panels.
Even though energy is used in active systems, the advantages of higher efficiency and greater production far outweighs the cost of the power consumed.
One or two solar air panels mounted on a roof can provide supplementary heating of the house in winter. Temperature sensors in the house and on the air panel are connected to a controller. When the house temperature is say 20 degrees cooler than the panel, a fan is activated to draw cold air from the house, blow it across the panel where it heats up by the sun and then back into the house. The system is turned off during summer.
A solar air panel mounted on the roof of a house.
Heat pump hot water systems are similar in operation to reverse-cycle air conditioners. They use a fan to blow air over an evaporator coil pipework that contains a refrigerant. The liquid refrigerant changes into a gas, which is then pumped through a compressor to increase the gas’s temperature (and pressure).
A solar air panel can produce cheap heating of rooms in winter.
The excessive heat of the gas transfers through a heat exchange pipe system to heat the surrounding water, and the gas subsequently cools back into a liquid. The cooled liquid flows back to the evaporator coil and fan area and the cycle is repeated.
The advantage of a heat pump is that it simply uses the energy of the air to heat water, and it produces more heat than the energy used to achieve this. If you can preheat the water (via roof-mounted solar water panels) before it enters the heat pump storage tank, then even less energy is used to operate the fan.
A heat pump extracts energy from the air to heat water.
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The ratio of energy produced to that used to make it is known as the coefficient of performance. An electric storage hot water system uses electricity to heat water, and at best the coefficient is about 1 (but usually less). Heat pumps can have a coefficient of performance between 2 and 5, which is a significant heat (energy) saving.
There are two aspects to energy generation. Primarily, it is about producing electricity, but it also may involve using energy to provide heat and power, move water or be burned as fuel.
The use of renewable energy to provide electricity and power has been discussed in reasonable detail in my Basics of Permaculture Design book, so only a brief summary of photovoltaic, wind and hydro systems are detailed here.
Many individual cells make a module and many modules are joined to make an array.
Solar electricity panels (solar cells) are getting more efficient and cheaper as years go by. As sunlight hits the surfaces of particular elements, electrons from the atoms are released and these flow as electricity (hence the name photovoltaic — photo = light and voltaic = volt, electricity).
Individual solar cells are mounted as a module or panel and many of these are joined to form an array.
The cells are based on a sheet of the semiconductor silicon, most often dosed with small amounts of other substances, which may contain gallium, arsenic, cadmium and germanium.
Emerging research has seen the development of thin film solar cells, including some that incorporate light-sensitive dyes and organic polymers, which have been used to create walls of buildings and even solar cell windows.
Other thin film cells, such as the copper indium gallium selenide cell and the gallium arsenide cell, have demonstrated the most efficiency of converting light into electricity.
Most solar cells installed around the world only have efficiencies of 6–20%, but some new technologies (called triple junction cells) have shown over 40% efficiency.
Solar paint is also being developed where semiconductor polymers are suspended in water and then coated onto plastic or glass sheeting.
Eventually, you may be able to simply paint the solution onto a roof to generate electricity.
Very few houses have access to good wind and a small domestic turbine produces only meager power due to inefficiency and size. Wind is too variable so there are only some sites suitable for wind power. Certainly wind generators can be used in conjunction with solar or hydro systems to complement these.
Much research has been undertaken, including this generator design by Ben Storan.
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The Sun provides about 100W/ft2 at the Earth’s surface. This is enough power to light fifty 20W compact fluorescent light bulbs.
Silent turbines are not yet available in the marketplace so you need to be mindful of noise — for your family and your neighbors who may not appreciate your energy harvesting endeavors. Generally, to generate reasonable power you need larger blades and taller towers.
In recent years turbine technology has changed and weird and wonderful designs are being built. These new wind generators are more efficient and respond to lower air speeds than the traditional blades, which have been used for decades.
X-wind. Just another example of the many innovative wind generators now becoming available.
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Householders who generate power from photovoltaics or wind generators, or some combination of these, have two options. Systems can be grid-connected where your domestic or commercial system is interconnected to the state service provider. You sell and supply the power you generate to the “grid”.
Remote homes may not be able to obtain electricity from a government or private energy supplier. They require a stand-alone system to produce enough electricity to run their household or property. This is often called a RAPS — Remote Area Power Supply.
Moving water has inherent kinetic energy. This can be harnessed and converted to mechanical or electrical energy and then used to operate machinery or power homes. However, the energy in moving water or from a waterfall has to be controlled and contained before it can become useful. This may involve pipes from the high water point to a lower point, some weir, dam or storage of water at the high point and suitable equipment, like a turbine, to convert the energy in moving water into a form that can be better used.
An impulse turbine spins when water is directed onto blades.
Turbines are grouped into two types: impulse turbines and reaction turbines. Impulse turbines spin when a fine jet of water is directed onto the cups or blades. Pelton wheel, cross flow turbines and water wheels are common examples of these devices. Under-shot and over-shot water wheels have been around for literally thousands of years, while most of the other turbines were developed less than 200 years ago.
Reaction turbines don’t change the direction of water flow as much as impulse turbines. Reaction turbines simply spin as the water or air passes through them.
Reaction turbines spin as water (or air) passes through them.
A windmill is a very common example of a turbine that reacts to moving air, while Francis and Tyson turbines are common examples of water turbines.
Some of the water reaction turbines can sit in the stream itself and be suspended by a floating raft or anchored to the bank of the stream.
The amount of power that turbines generate depends on the vertical “head” of pressure and the flow. Fast water movement produces more spinning action and more energy can be transferred from water that is dropped from a great height.
Every turbine has particular operating parameters: some work well in high flow situations, others require high head and low flow and others again maintain good efficiency rates when there are variable flows.
Mini hydro systems are only suitable in properties that have a continuous running water supply and a slope over the land.
Unless you have a steam or creek that flows all year round, with a vertical drop of at least a few yards, generating power from water may not be an option for you. It may be better to examine the possibility of solar or wind power.
A hydraulic ram can lift about 10–20% of the water that passes through it to great heights.
Besides generating power from running water, air-driven pumps, called hydraulic rams, can be employed to move water from a stream to a header tank or dam. Hydraulic rams are simple devices that capitalize on the energy in water to compress air in a pump mechanism to lift water.
Disused bicycles can be converted into electricity generators.
Both wind and water generated electricity requires a turbine or generator to convert moving energy into electricity. Many bicycles are fitted with a small generator attached to a wheel that spins and makes enough power to light up a headlight while riding at night. Some manufacturers have adapted this principle to make a range of human-powered machines to enable batteries to be recharged, lights to operate and to drive a water pump and a number of household appliances.
You can even buy a “kit” to convert an unused bicycle into a generator, and use this to both power the appliances and exercise at the same time. For example, a laptop usually draws about 50W, so a 20 minute exercise on a bicycle generator will power the laptop for one hour.
Many bicycle generators can produce up to 500W, so this is enough power to enable an inverter to operate simple household appliances such as kettles, toasters and blenders.
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Many homes have appliances that have a “standby” mode. Even when you think that you are saving power, these appliances, such as computers, TVs, stereos, DVD and CD players, contribute to about 5% of greenhouse gas emissions and cost you about $100 each year in power bills.
There are a variety of gases useful as fuel, and these include liquefied petroleum gas (LPG), natural gas and biogas.
LPG is a mixture of volatile fractions from petroleum refining: principally propane and butane, with small amounts of propylene and butylene.
This is often used as a substitute for gas in motor vehicles because it is easily liquefied and has a reasonably high fuel (or calorific) value when burned.
Natural gas is a fossil fuel typically trapped and buried under ground or under the seafloor. It is mainly methane, but does contain smaller amounts of other organic substances as well as carbon dioxide and hydrogen sulfide. Natural gas is harder to capture and store as it is a gas at room temperature.
Homemade biogas generators are common in some countries.
Biogas is a by-product of the anaerobic decomposition or fermentation of organic matter and has a similar chemical composition to natural gas. It is easily made from a few simple substances and inexpensive equipment. Biogas can be produced from many organic substances, such as food wastes, plant residue, manures, fruit cannery wastes and landfill green wastes.
Biogas can be used as a fuel for heating, cooking and steam generation, or as a fuel in internal combustion engines. It burns gently and produces carbon dioxide and water, with little or no poisonous carbon monoxide, so it is relatively safe as a fuel in a home.
When biogas is made, it may contain reasonable levels of hydrogen sulfide and carbon dioxide, and these need removing in an operation called “scrubbing.”
The main purpose of scrubbing is to reduce these corrosive gases, which combine with the water vapor to form acids and hence corrode all metal parts of the gas system, as well as to get rid of the unburnable carbon dioxide that simply “takes up space” for no useful return.
To remove these gases, the biogas is bubbled through water and then passed through steel wool, iron shavings or something similar to remove the hydrogen sulfide.
In an optimum operation you can produce about 9–12 ft3 of gas (250– 300l) in a 50 ft3 digester, which has about 4% solids — that’s 130 lb of wastes in approximately 400 gal (1,500l) of water.
This volume depends on the temperature of the system and the type of solids added, so returns are mostly lower than this. At a practical level, one bucket of manure is typically required to produce enough biogas to operate a stove for the day’s meals.
Cows produce 65 lb/day — about two bucketsful, while pigs produce about 13 lb/day and chickens much less than 1 lb/day. (One cow produces over 1 ton dry matter each year, which is equivalent to about 10 tons of fresh manure.)
Generally, humans do not produce enough solid waste (even with daily food scraps thrown in) to produce enough biogas to run a stove. Human waste only makes about one-quarter of the biogas produced from the equivalent amount of cow manure.
Some research is being undertaken with algae and fungi to produce biogas. Various algae and microalgae are being cultivated in oceans to provide the feedstock to be used in biofuel (biodiesel) production or fermented directly to make biogas.
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The average household in Australia throws out about 30 lb of waste each week. Half of this is food scraps and garden refuse, which could easily be composted. Composting your organic waste would save about 900 lb of landfill each year.
Fungi are being used as a pre-treatment strategy. Fungi change and digest cellulose and lignified material, such as hay and straw, to enable microbes to ferment these materials easier, resulting in greater biogas production.
Biodiesel can be a substitute for diesel in engines. Sometimes it is blended with petrodiesel but can be used “neat” with minor engine modifications, or even no modifications at all.
Biodiesel is made by chemically combining fats (such as vegetable oils and animal lard) with an alcohol to produce organic compounds known as esters. These substances are volatile and burn easily, even though the calorific value is slightly less than petroleum-based diesel.
Typical feedstocks (to provide the oil or fat content) include soybean, canola and sunflower oils, although animal fats and grease from pork and poultry, for example, can be used but with diminishing returns. Backyard operators often obtain the cooking oil and fat wastes from fish and chip shops, filter it and then add the reagents.
The most common alcohol used for the conversion of oil into esters is methanol (and ethanol is an option), and a catalyst, such as sodium hydroxide (NaOH) or sodium methoxide (CH3 ONa), is used to speed up the process, which may still take several hours.
While the majority of what is produced is biodiesel, many by-products are also formed and these have to be removed. Soap, glycerol, excess alcohol and some water have to be decanted or drawn off, and the relative amounts of each of these depend on what oil or fat and what catalyst was used.
Plant oils can be used to make biodiesel.
How to make a hot compost pile was discussed in chapter 4. While you wouldn’t want to take all of this heat away, as microbes use the energy to break down the organic wastes, some of it can be used to heat water, animal enclosures or our homes.
Hot water can be extracted from a compost pile.
As long as the compost pile has the correct ratio of ingredients and is large enough (held within a 70 ft3 wire cage or bigger), the heat generated can heat a coiled pipe and produce hot water for a few showers.
Alternatively, hot water can be passed in pipes through a heat exchange space heater to heat a room or animal pen to keep everyone and everything nice and warm during the night and in colder months.
Generally, the larger the compost pile, more heat over a longer time can be utilized. If the compost is really “cooking” then temperatures a little over 140°F are common.
While black poly irrigation pipe can be used as the coil, soft and bendable copper tubing is far better to absorb the heat and move the hot water.
Bear in mind that even 0.75 in (20 mm) copper piping only holds 10 oz for every three feet in length, so you may need a very long pipe to have a shower.
Even if you only use 7.5 gal for a shower (say 2.5 gal/minute for a 3-minute shower — that’s quick!) you need about 120–150 ft of copper coil, assuming that as water passes through the coil it can quickly heat up.
To overcome this problem, a shorter coil is used to transfer hot water to a small storage tank, typically supported on a stand several feet above the pile, so that gravity can be used to operate the shower.
Three to six feet of “head” is not ideal as this results in just a trickle, so you could pump the hot water if that was feasible.
Cooking food requires heat or fire, or both. Low technology solutions utilize either solar energy or biological fuels to provide this energy.
A solar oven or solar cooker uses sunlight to cook food. These can be easily made from simple materials and can produce high enough temperatures (often up to 300°F) to cook any sort of food.
There are two main types of solar cookers — parabolic reflectors and box cookers. Parabolic reflectors incorporate a reflective foil or mirrors to concentrate the sunlight energy to a focal point. The food or pot is held at this focal point and heats up.
Solar box ovens typically consist of an insulated box with dark-painted internal surfaces, and a glass lid. One or two adjustable reflective surfaces may be added to help direct sunlight into the box.
Reflective curved surfaces can direct sunlight onto a pot to cook food.
Meals, such as stews, rice dishes, bread, cakes and even roasts, cook over several hours. Occasionally the cooker is moved to follow the Sun’s path across the sky to ensure maximum heat gain.
Biological fuels include biogas and wood, but can also include other organic substances such as manure (dung), oil and flammable solvents. Biogas has been discussed earlier, so let’s talk about wood.
It is possible to view wood as a renewable energy source. This is because we can grow and harvest wood and timber in a sustainable way. We just need to remove and use wood at the same rate at which it grows, or a lower rate.
Solar ovens can be made from simple materials.
Planting specific species of plants that can be coppiced to produce a continual supply of timber and fuel is easy to do. There are many plants that are currently used for these purposes, and others that tend to be fast growing and produce high heat energy when burned can be tried.
Even compressed sawdust, a by-product from the timber milling industry made into pellets, or paper pulp bricks are far less costly than using kerosene, oil or gas for heating and cooking.
Coppicing fast-growing trees enables a steady supply of wood.
The majority of people in the world who use biomass as a fuel burn animal dung. Cow and other animal patties are dried in the sun and burned in stoves. This is not as efficient as burning wood, but in many places wood is in short supply.
Rocket stoves are becoming popular in some countries, as these require smaller volumes of wood to produce heat at a very efficient rate. The combustion of the wood is thorough as the stove has good air flow and the generated heat is better utilized and not lost “up the chimney.”
A rocket stove is very efficient as the generated heat is retained.
A rocket mass heater is a recent variation of the rocket stove where the fuel burns sideways, the exhaust gases are relatively cool (and clean) and there is hardly any smoke.
Strong convection currents inside the insulated riser tube draw the flame into the heater. The majority of the heat produced stays inside the heater and is not lost as it would be in a conventional wood fire.
A rocket mass heater produces heat from relatively small volumes of wood or fuel.
Wood-fired ovens are also becoming popular in outdoor kitchens. These “pizza” ovens are easy to make but you can buy readymade kits and ovens themselves. Most use refractory cement to prevent cracking but many people who build “do-it-yourself” ovens just use a clay and sand (or clay and straw as in a cob oven) dome built on a brick floor. Normal household bricks can be used but fire bricks are best. Refractory cement is a purpose-made product and makes a fire-resistant mortar for use in kilns and furnaces.
Pizza ovens are becoming popular outdoor kitchens.
The most popular mortar for a pizza oven is a hybrid mix of refractory cement, normal cement, sand and lime. This allows the surfaces and joints of the oven to be sealed like a ceramic. Fire bricks have a high alumina content and this ensures they can withstand very high temperatures without cracking and falling apart.
Most people probably think of air conditioners when they investigate ways of cooling the rooms of their homes. Cheaper and lower operating cost options include ceiling fans, evaporative coolers and whole-house fans in the roof space.
Reverse-cycle air conditioners are heat pumps that can be used to both heat and cool a home, depending on the ambient temperature, and tend to be more efficient and have cheaper operating costs than whole-house ducted air-conditioning systems.
If houses are designed to be passive solar, then a ceiling or freestanding fan is all that is generally needed to cool a house down in hot weather spells. Ground-source heat pumps (also called geo thermal heat pumps), which have pipes buried under the ground, are one way to further reduce cooling (and heating) costs in a home, and while these are relatively unknown they certainly warrant investigation.
In some countries, water piping buried in the ground can be cooled or even heated to produce supplementary cooling or heating in a home.
Using the ground to cool a home is not new. Air drawn through pipes buried about a yard or two below the ground can be ducted into rooms or used to cool fruit and vegetables as part of a solar (thermal) chimney.
Air can be cooled as it is drawn through a pipe buried underground to keep vegetables fresh.
A black-painted chimney heats up during the day and the hot air rises and is ducted out of the house. This causes a suction of air along the pipe. This air is cooled by the earth and enters the house as much cooler air.
Passing this air through an insulated cupboard keeps food fresh, while a pipe network under the house enables cool air to enter each room as required, by opening and closing a vent.
Piped air can also be effective as a simple air-conditioning system.
Evaporating water can also cool air. The heat of the air can be used to evaporate water and while this is the principle of evaporative air coolers, a device called a Coolgardie safe is used to keep food cooler and longer before any spoilage occurs.
Burlap, with one end dipped into a tray of water on top of a cupboard and allowed to hang down, absorbs water and holds it in within its fibers.
As a breeze passes over the burlap, water evaporates and the air passing through the bag is cooled. For water to change from a liquid to a gas, it requires energy.
The heat in the air (of the breeze) is enough to enable the change of state of water, and so the air cools.
A Coolgardie safe cools air as water evaporates from its sides.
Besides burning fuel, using the heat from compost production and employing a heat pump device, solar energy can be used for heating. Sunlight can be harnessed to heat water, dry foods and produce freshwater.
Solar water heaters are devices that capture sunlight, convert this to heat and then use the heat energy to produce hot water. Some systems have the storage tank on the ground (active systems), others above the solar heating panels (passive systems). In a passive system heated water rises towards the horizontal storage tank and colder water falls downwards into the collectors.
A passive solar hot water system utilizes natural flows of warm and cold water to make hot water.
Thermosiphoning occurs and there is a steady flow of water into and out of the storage tank. On low sunlight days or during continuous cloudy weather, the water temperature may remain low. A booster is required to heat the water enough for its use inside the home. The most common boosters either use electric heating elements or gas burners.
Active solar hot water systems use pumps to move water from a storage tank on the ground to the roof area where the collectors are mounted. They may still need a booster, but they tend to lose less heat and be more efficient than passive systems.
A solar still makes small amounts of pure water by only using sunlight.
A solar still is also used to heat water but it enables the production of pure water from salty or contaminated water. Any type of water source can be used, and the sun’s energy causes some of the water to evaporate, leaving the salts and pollutants behind. The water vapor is trapped and condensed, so that pure liquid water is able to be collected. A solar still generally doesn’t provide huge volumes of freshwater each day, but certainly enough for survival and emergency water.
The other advantage of a solar still is that it can heat water to a high enough temperature to sterilize it. Most microscopic organisms die at 140 to 160°F, and this temperature is easily achieved in a solar still.
A homemade fruit dryer uses clear plastic or glass sides and top to desiccate fruit.
Solar dryers are typically used to dry fruit, as a method of food preservation. Sliced fruit, meat and herbs generally take a day or two to dry. Not all of the moisture is lost, so fruit tends to be leathery and a little flexible.
There are a few different versions of solar dryers, but they rely on the heat of the sun to cause air to heat up and to move upwards and through the trays, slowly drying the fruit.
Several trays, often with window screen mesh as the base, allow air to move through and over the thinly-sliced fruit and vegetables.
Sunlight heats air, which passes over and through shelves containing fruit slices.
I am a firm believer that when you have a machine, or can afford to hire one, use it. You wouldn’t spend days or even weeks digging holes, shifting soil for major landscaping works and creating roads and dams all by hand. Machines save us time and work, even when many consume fuel.
However, there is always opportunity for people power. If you can’t afford machinery then manual labor will have to do. One day maybe all vehicles will run on biodiesel made from farm waste.
Nevertheless, there are times when a scythe is more appropriate than a string trimmer, a horse and plow better than a large tractor, hand tools instead of power tools, and an ax less hassle than a chainsaw.
Sometimes, a simple tool such as a scythe saves us time and energy.
Unfortunately many people will need to re-skill or learn new skills if they ever need to use simple tools and techniques, but there is nothing wrong with that! As we all move into a new era of human history, let’s embrace the consideration and use of appropriate technologies.