Energy Farming: Since I’m including the spacing requirements for everything else in this guide, I figured I’d also include the spacing and conditions necessary to provide energy in each of these situations. For all the math I’ll be using kilowatt hours and will include references as to what a kilowatt hour’s worth of energy can do. Not every energy source is great with every situation, hydroelectric is bad in arid environments, wind is bad in forests, solar is bad in northern climates. All of them have their uses and they can even combine to work together in interesting ways.
A single kilowatt hour is able to be stored in a deep cycle battery such as a large heavy lead acid battery that would cost around 200 dollars each, or a smaller lithium ion battery pack that would cost around 400 dollars per battery. Note that the price of batteries is changing rapidly due to technology advancing, and that by the time I finish writing this info it may be outdated.
The average house in the United states consumes 10,716 kilowatt hours a year, or 893 kwh a month, or just under 30 kwh a day. That’s a lot, but by India's standard for electrified homes, each household in India consumes 1,080 kwh a year, 90 kwh a month, or just 3kwh a day, roughly 10% what the USA uses.
1 kilowatt hour can run a microwave for an hour, or an electric stove long enough to cook a meal. It can run a Gaming PC for two hours or a laptop for ten hours. An older 60w lightbulb 16 hours, or a 6 watt LED bulb for 165 hours.
1 kilowatt hour can charge an electric car to drive 4 miles, or an electric golf cart roughly the same amount, or charge 1.5 electric bike batteries that could power it for 35-75 miles.
1 kilowatt hour can run a whole house air condition for fifteen minutes to a half hour. Or run a small efficient single room AC unit for 2.5 hours. It can also run a room sized space heater for 1 hour, a tiny personal space heater for 3 hours.
To farm Bitcoin and practically any other type of cryptocurrency, the numbers start looking insane. Estimates put the amount of power to mine a single bitcoin at 143,000 kwh, enough to power over 40,000 homes in India for a full day, or a small village in India for a year.
Note 1 Kwh = 3214 BTU (british thermal units)
Energy (Photovoltaics): Provides energy only in the day (without storage) but since most people are only awake during the day doing work (using energy) it tends to work out. Solar panels provide DC power at a rate of 15% - 25% efficiency. A small solar panel roughly 17.5 square foot panel can provide roughly 320 watts of power when directly facing the sun without obstruction. Rule of thumb is that someone can expect roughly 5 hours of power through solar panels a day per “Sunny'' day. Though this changes a good deal, especially spending on proper orientation of the panels per season (remember that we have a seasonal tilt of 23.5 degrees) taking that into account as well as the climate (desert areas have more sunny days that temperate/boreal zones) then a reasonable estimate for the amount of power produced a year can be calculated. Assuming a 17.5 square foot panel could output 1600 watt hours a day or nearly 1.6 kilowatt hours. Assuming 1000 square feet of panels angled towards the sun and clear of obstructions, that’s roughly 91 kilowatt hours of energy produced per sunny day.
While many people may balk at land use required for large amounts of solar energy. As of the time of writing this, based on how the solar fields are set up it can take 5 acres of solar panels and infrastructure to produce 1000 kilowatts of peak capacity or roughly 5000 kilowatt hours a day. That’s a land area of over 220,000 square feet. But the good news is there are plenty of places where the shade provided by solar panels can be helpful. Any roof that’s unsuitable for planting on top of and isn’t shaded by trees is a great option many people around the world do. Additionally placing solar panels for covered parking or covered pathways where trees are unsuitable is a great option. While many plants need sunlight of 6-8 hours a day or more, many more plants can be grown in the partial shade, meaning that interspacing solar canopies/pergolas with shade tolerant crops underneath them can make for a great combination called agrivoltaics. Or if these options don’t work, simply placing solar planes on heavily polluted land or any land such as extreme desert or bare rock, is always an option.
Energy (Wind): To this day windmills are associated with farming, now they just farm energy. The difference between windmills and wind turbines is pretty simple. Windmills use kinetic wind energy to directly power a mechanical device (almost always a mill for grinding grain) though there are windmills that are used for pumping water or generating electricity. A wind turbine is used purely to convert the force of wind into electrical energy. Though to be honest the terms are somewhat interchangeable to most people nowadays. The most important thing in deciding whether to place a wind turbine is “is there enough wind around to make this viable.” Measure the wind speed at the place you’d like to build a wind turbine. Remember that the ratio is 1 mile per hour equals 0.447 meters per second. When looking for spots for placing wind turbines, if you want to get power out of it, it has to be in the highest area around. If there’s no high area around and you live in an incredibly flat place, that can also work. The next thing to focus on is to make that area even higher and the land around it. If there are any trees around that might obstruct the flow of wind, they may have to be taken down and replaced with bushes or groundcover plants. Additionally try to install a pole or tower as high off the ground that’s reasonable. When it comes to windpower it looks like the name of the game is go tall or go home. There are tons of design guides to wind turbines and windmills so I figure I’ll post the stats to both an old school dutch windmill, a middle ground option and a modern high tech wind turbine to show the range of possibilities for wind energy.
An old dutch windmill was a marvel of engineering at the time. Used to pump water out of swamps and brackish water around the coast, meaning the dutch managed to expand the amount of usable land of their country considerably. Anything, from hammer mills, sawmills, water pumps, and of course milling grain was done by these massive beasts of early renewable energy. Usually the mechanical structure was designed to be rotated entirely by having the mechanical section rest on top of a large stone or wood tower for tower mills, or on a massive wooden post for post mills. The mill could then be roasted by oxen early on or by using smaller sails in the back that, when able to face the wind, would automatically rotate the whole structure until they were no longer facing the said wind and the main sails could face the wind properly. The amount of the wind that blades would capture could also be regulated by throwing cloth onto the wooden frames that made up the individual blades, allowing a simple if somewhat dangerous method of variable wind power input. It’s hard to find stats on what these mill’s power output was or what their size was, however reasonable estimates were 20m in diameter for a smallish one, and a reasonable power output after losses was somewhere around 12-25 hp or 9 - 18.75 kilowatts of energy at peak operation. Note that this windmill would have a footprint of over 4000 square feet, but it’s still quite impressive for something that came out of the middle ages.
One of the earliest electric wind turbines I can find that has firm numbers, is Charles F Brush’s wind turbine that he built in 1888. Which looks to be a middle ground between the early Dutch windmills of the 1500s-1800s and the modern electric wind turbines being produced nowadays. This turbine was completely automated and provided power for its entire 20 year life cycle to Brush’s home in Cleveland. Aided by 12 batteries for storage (unknown kw hour rating) this system powered the first electric home in Cleveland Ohio. This turbine had a blade diameter of 17 meters (56ft) and a 12kw dynamo installed. Though this took up well over 3000 square feet (especially with the tail) this was an incredible feat for the late 1800s.
For modern wind turbines I’m picking on that fits the standard plot size we’ve been using the rest of this book. A 1000 square foot plot can fit just about a 31.6 ft or a 10m blade diameter wind turbine that can rotate in any direction. For this reason I’m basing this off the stats of Aeolos 20kw Wind Turbine.
The Aeolus 20kw model can generate 20kw reliably with a max power output of 25kw. It has a rotor blade diameter of 10m or 32.8 ft. Its start up speed is only 3 m/s, Its rated wind speed is 10 m/s, and its maximum rated speed is 50 m/s. At a total weight of 960 kg or 2112 lbs and a 20 year warranty, this is a reasonable turbine for many small applications. And unlike the other wind generator examples, this can be bought with a 18 meter (59ft) tall tower for the last listed price of $35,800 USD at the time of me writing this (Summer 2023).
Energy (Water): Hydroelectric power is actually pretty easy to calculate and can be used to store power in an easy way (in theory not in practice). All you need are two reservoirs of water, storing the water in the higher elevation tank/pond/lake and having a high efficiency turbine in the middle right by the lower elevation tank/pond/lake. Though if you have no better options, a simple water wheel can do in place of a turbine at the cost of efficiency. For efficient turbines, go as high efficiency as possible and I recommend using peloton wheel style turbines for this reason. The only sad bit of this is the height requirements for pelton wheels, as these can require 100ft in some instances. As for the math, here's what you need. Please note I’ll be doing all of this in meters as it works better for math, then posting conversions.
P = Q * p * g * h * n
P = Power produced represented in VA or Watts. (1000 watts = 1kw)
Q = water flow per second in (m^3)/s. How much water hits the turbine every second of operation. This is roughly 1000 liters per second equivalent, 264 gallons equivalent, or 35 cubic feet equivalent.
p = density of the fluid in kg/m^3. Water is at 1000 kg/m^3 which is almost certainly what will be used.
g = gravity in m/s^2, this is good old 9.81m/s^2 here on earth.
h = height, often called the waterfall height. How high the water is in the high elevation tank compared to the turbine. This is in meters (1 meter = 3.28ft)
n = efficiency of the whole system. This value will differ from .5 to poorly built systems, to .7 for older systems, to .9 for modern efficient systems.
Most examples will probably be something like 10 meters in height at 0.01 meters cubed per second at an efficiency of around (.05) for a small DIY setup. This should yield around 491 watts every second of operation or around 0.491 kilowatts every second of operation. Provided this turbine could be kept running for an entire hour, that would generate 0.491 kilowatt hours.
The great thing about hydropower though, is that it can be turned on only whenever people need power. Say if the sun isn’t shining or if there isn’t much wind. This means that hydropower can essentially be a massive battery, even being able to recharge the system without waiting for it to rain, but instead pumping water up from a lower reservoir whenever the demand for power is low, and using the system’s turbine whenever the demand for power is high. To calculate how much hydroelectric energy storage a tank/pond/lake has is incredibly simple. For the output of the formula above (.491 kwh) take the water flow per second value (0.01 m^3/s) and find out how large of a tank/pond/lake you have. Then simply divide the tank size by the flow rate.
Size of Tank in M^3 / water flow per second in (m^3)/s = seconds of operation
Since we’ve been using 1000 square feet (92.9 square meters) often in this guide, let’s assume a tank size with a surface of 1000 square feet, that’s 10 feet deep. This is roughly 283 cubic meters of water.
283M^3 / [.01(m^3)/s] = 28,300 seconds of power or roughly 7.8 hours of sustained power. Multiplying that by our 0.491kw value from earlier and we have roughly 3.83 kilowatt hours of storage.
This is somewhat costly in terms of land use compared to modern batteries. However if there are bodies of water at fairly different heights close to each other. This is certainly a means of power worth looking into. And since Wind turbines/mills have historically been placed atop great heights and used for pumping water, this system could work well with other energy types, even solar panels atop the reservoirs could be used to help deal with evaporation.
Energy (Concentrated Solar): Solar panels aren’t the only way sunlight is collected, Directly capturing the sun’s heat through radiation is one of the oldest energy systems in the world. It’s used to heat homes through the proper placement of windows, dry and cook food, and if you use a solar collector, power a small steam turbine. The great news is that the sun produces a great amount of power per square meter, and at the top of our atmosphere on earth we receive 1413 -1321 watts per square meter. By the time it reaches us on earth, the value is 160 - 340 watts per square meter averaged over the course of a day.
When it comes to harvesting and using this power there are several options. Most of which involve something along the lines of using tons of mirrors to concentrate the sunlight to heat water. This water then can be used for regular hot water for home or industry purposes or it can be tossed into an efficient steam engine to perform work or run an electrical generator. While not nearly as popular as photovoltaics due to the higher complexity to setup and the relative plug and play of solar panels.
While there are many DIY plans around I’ll be basing these off the Lytefire 4 as it’s a large system that takes up relatively little space and makes for some easy math. The Lytefire 4 uses a 4 m^2 of mirrors (43 square feet) to direct sunlight into a metal place or cook area to deliver 2 kilowatts of energy in optimal conditions. If a water boiler were to be placed on top and fed through a reasonably efficient turbine generator setup, that could easily produce 1 kilowatt of power in the sunshine assuming normal losses. The waste heat could even be used for other things such as home or greenhouse heating in the wintertime.
Energy (Solid fuel combustion): If a steam engine is available and the sun isn’t shining someone might be asking, why not toss some wood under a high efficiency boiler and produce power that way. And truth be told this is an option.
Wood: It’s a great resource that we already calculated rough farming at 4-10 tons per acre elsewhere with pollarding/coppicing with modern hybrid trees. At average that’s 7 tons of wood per acre or 14000 lbs per acre. That’s 318 pounds per 1000 square feet. After the wood has been dried it has a btu rating of between 8500 and 9000 btus or british thermal units. That’s around 2.5 kilowatt hours of energy per pound of dried wood. That means in a year 795 kilowatt hours of energy could be collected off of 1000 square feet of well managed timber. Or realistically something around 230 kilowatt hours of energy given the efficiency of average modern engines.
Bamboo: It burns quickly, but it’s still solid fuel. From what I can gather, dried bamboo has the same weight to kw hour as lighter wood (around 2.5 kilowatt hours per lb), however people seem to think that it’s much lower than that because wood is traditionally stored in cords which are a unit of volume. In any case bamboo contains air pockets inside of it, giving it a low density compared to wood. Since these air pockets can explode in high temperatures it would be advisable to crush bamboo or turn it into pellets. Additionally bamboo has the tendency to burn quickly and release all of its heat at once. This makes it great for starting fires, but unless someone is going to be nursing the fire and feeding it constantly, it may be wise to supplement this combustion with wood so there is no need to babysit it. Bamboo can be farmed in some locations at over 16 tons per acre a year, or 32000 lbs per acre per year. That roughly turns into 727 lbs of bamboo a year off of 1000 square feet. That would be theoretically over 1800 kilowatt hours of energy per 1000 square feet. Or more realistically over 540 kilowatt hours of energy given the efficiency of modern engines..
Dung: Poop is something that if you keep animals, the questions will likely come up about what to do with all of it. The good news is that if dried it can be used as a fuel source and not just as “green” manure. Dried dung from animals such as cattle and camels has an energy rating of just under 2 kilowatt hours per pound. Not terrible for something that can be used for free. Amount of dung that can be collected is heavily dependent on what animals are available and how much they’re being fed. For cattle, they produce partially wet manure based heavily on their size and diet but a decent estimate is a cow will poo 8% of their body weight per day. That’s roughly 96 lbs of manure a day for a 1200 lb cow, assuming said fresh manure is 85% water, that equates to 14.4lbs of dried manure per day, or potentially over 27 kilowatt hours of energy per cow per day. Though an engine wouldn’t extract that energy at nearly 100% efficiency, 30% efficiency may be reasonable giving 9 kWhs of energy each day off a cow’s manure.
Energy (Liquid Fuel Combustion): We have stats for producing ethanol and vegetable oil (biodiesel) so why not include them. Note that the efficiency of the engine is what really counts here. Will be focusing on cars as that’s what the majority of people use their fuel on.
Biodiesel: This fancy vegetable oil has an energy density of 9.17 kwh for every liter, or 34.7 kwh per gallon. That means that if you had a 100% efficient diesel generator, it would be possible to power an electric car to go 138 miles or power a house a whole day. Sadly most high efficeincy diesel engines in cars usually are only 41% efficient and the majority of diesel cars hover at around 30% efficient. So burning biodiesel in a modern relatively compact piston engine only nets around 10.4 kwh per gallon. Still not a bad value for something the size of a milk jug. Going off one of our more impressive oil crops in the guide, 1000 square feet of avocados could produce around 6.3 gallons of vegetable oil. That would net roughly 218 kilowatt hours at 100% efficiency or 65 kilowatt hours at around 30% efficiency.
Ethanol: It’s just extremely high proof alcohol, and has an energy density of 6.66 kwh for every liter, or 25.2 kwh per gallon. As with diesel fuel, that’s an insane amount of energy for something that could fit in a milk jug. Sadly the issue is the same with most cars only converting around 17-21% of the energy stored in the fuel going to the wheels with it reaching around 30% efficiency for high end engines. Do at 20% efficiency that’s around 5 kwh per gallon of fuel. It’s impressive, but of the two I’d look into biodiesel. For 1000 square feet of corn as a feedstock in producing ethanol, 7.2 gallons of ethanol could be produced. That’s roughly 181 kilowatt hours at 100% efficiency or 36 kilowatt hours at 20% efficiency.
Energy (Gaseous fuel combustion): While storing this is much more complicated than bottling oil or stacking firewood, both biogas and wood gas can be made somewhat on demand. Though biogas definitely requires some forethought.
Methane (Biogas): People who like this option have probably either seen the old british tv show the good life, have an abundance of livestock, or have someone in their household that farts all the time. In any case, in order to produce methane or natural gas / biogas, the primary thing to look at is to build an anaerobic digester. From then the feedstock is loaded and gradually bacteria break down organic matter into methane and other residual gasses such as carbon dioxide. Methane has roughly 10 kilowatt hours of energy per M^3 kilogram of gas, with biogas usually being around 50-70% methane, giving most biogas somewhere around 6 kilowatt hours of energy per M^3. It can be used to power some natural gas appliances and even diesel engines can be converted to run on it. Think of an anaerobic digester as a pre-composter, whenever there’s anything that may need to be composted on a homestead then it can be tossed in the digester for power production first. Then the decayed remnants of feedstock from the digester can be tossed in the
Below I have listed some figures I dug up for various feedstocks and how much biogas they gave off each per ton. Please note that these numbers are per imperial tons
Sewage Sludge is exactly what it sounds like. All the solid stuff that gets flushed down the toilet or disappears down the drain is considered this or sometimes called biosolids. Per Pennsylvania, one household produces roughly a quarter ton (500lbs) per year. While this doesn’t sound like much, towns and cities can have thousands to millions of households hooked up to a sewer system. Meaning harvesting biogas at wastewater treatment plants may be a viable option for some.
Cattle manure is usually produced at around 8% of a cow’s body weight per day. Meaning that a 1200 lb steer would produce roughly 96 lbs of manure per day.
Pig manure seems to be produced at roughly 4% of a pig’s body weight per day. That means a 300 pound pig will produce roughly 24 lbs of manure in a single day.
Poultry Manure is usually produced around 0.2 lbs to 0.44lbs per chicken or duck that weighs around 4lbs. That averages to about .33 of manure per bird, giving a percentage of around 7.5%
Hay and Silage is often produced at around 150 lbs per 1000 square feet per year. And since straw is usually in animal bedding, it usually soaks up a lot of animal waste. Tossing old bedding straw into an anaerobic digester seems like a good use of resources.
Expired Food is sadly a common occurrence to everyone I know. On average people waste around 30% - 40% of all the food brought into a home, nevermind what spoils on farms and in stores. Even the least wasteful homes still report throwing out 8.7% of food brought into the house. America collectively wastes 100 million tons of food each year or nearly 600 lbs per person (though most of this is lost in food production and distribution). This sadly makes food waste an excellent source of biogas.
Fat is not only what you think it is from animals, but also fat rich foods such as those found in the oil crops section. Tossing in the leftover pumice from pressing oil out of crops is great for anaerobic digesters. It looks like for a mature cow (1400lbs) around 280 lbs of fat and bone are produced per butchering. Assuming half of that is fat, that’s roughly 140 lbs of fat per dead cow. Combining this with other forms of butchery refuse, and this begins to look like a viable option for power generation, if said fat is going to waste.
Wood Gas: Wood gas is an option mainly used for converting old cars and trucks to run on wood when gasoline is no longer available. To do this requires building a high efficiency gasifier, and if wanting to use it to run a vehicle, somehow mounting it on said vehicle. Per a single source who runs an old Dodge Dakota truck, they get roughly 5200 miles per cord of wood. A Dodge Dakota truck gets roughly 16 mpg in the city and 20 mpg on the highway. Assuming a cord of dry wood that’s roughly 3000 kw hours of energy, that’s roughly 1.6 miles to the kw hour of energy, meaning this truck could run roughly 3 miles on a pound of wood. Not a bad value for an abundant fuel source (the person I’m sourcing is using scrap lumber from a sawmill).
Energy (Muscle Power): Something I’m asked about fairly routinely is, could you put a person on a treadmill or large hamster wheel contraption and use them to power a home? The answer is no, but muscle power has historically been used often for power generation so it may not be a bad option in some circumstances. The term horsepower (746 watts) even originally refers to how much energy a house is able to sustain producing over the length of a day. Additionally this means that a horse and every animal on this list has a much higher ‘peak’ wattage or horsepower, with the max horsepower on a horse being around 15hp or 11 kw.
Here’s a chart that shows how much each animal can sustain producing over the course of a day (8 hours maybe) of work. Everyone has different outputs of work depending on effort, muscles, training, willpower and constitution, so expect a good amount of variation on this.
Firewood Trees: Fire is the oldest method of keeping warm and cooking food on the planet. Firewood is measured in cords, each of which are 4x4x8ft in size, or roughly 128 cubic feet. Based on numerous sources, the amount of firewood that could be harvested sustainably off of an acre of forested land is roughly 1⁄2 to 1 cord. Though this depends on many factors ranging from the density of the forest, fertility of the land, to the person managing said forest. As for how many cords a person needs though winter, well this can vary greatly depending on climate, insulation, and the woodburning apparatus. A cord of wood contains over 3000 kilowatt hours of energy, it’s just usually collected highly inefficiently. As a general baseline, for every 1000 square feet of house, 3 cords of wood are needed to heat a house through winter. Though the type of winter could vary greatly, a house in a harsher winter will need more wood and in a milder winter will need less. Setting Maine as a baseline (as of 2022) 3 cords per 1000 square feet is average, with more mild wintered areas like West Virginia needing 25-50% less firewood per winter. Additionally the quality of the woodburning apparatus plays a central role, with open fire fireplaces being nearly the least efficient, and rocket mass heaters being about the most efficient (reportedly needing 80-90% less wood per season). So my best recommendation for firewood would be to invest in good insulation, collect more firewood than you think you need, and to invest in a rocket mass heater(or other high efficiency heater) if at all possible.
Coppicing/Pollarding: Instead of cutting down an entire tree to the ground, one option is just to lob off the top with enough tree left to grow again. This allows for a steady supply of firewood without needing to replant. The difference between coppicing and pollarding is fairly simple. Pollarding is used if the land is to be used to let animals roam through it and these animals are at danger for eating the young shoots/leaves of the tree, then the tree is lobbed off at such a level that said animals cannot reach it. Meanwhile coppicing is just cutting it off closer to the earth as it’s more convenient to harvest that way. Modern hybrid trees that are rapidly growing can produce 4-10 tons of firewood (or roughly 3-7 cords) per acre provided they’re properly managed and under proper conditions. That’s 318 pounds per 1000 square feet
