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Cal Poly Living Lab
Devap air conditioning
Lake Atitlan Water-Distribution System
Living Off the Grid
Nuclear Generation and Desalination Power Plant
Portable Water Turbine System
Solar Harvesting on the Moon
Space Elevator - PHYS 310
Tokamak Thrust Engine
Use of Piezoelectrics (Human Powered Energy)
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Living Off the Grid
: Living completely off the grid by implementing renewable energy sources to provide energy for modern conveniences.
: The goal of this project is to outline a plan for you to build a single-person residence that minimized both energy consumption and carbon emissions, while using as much renewable resources as possible.
: Since you are living by yourself, you don't need a lot of space. Your energy resources are limited so it is also best to have a small living quarters for this reason as well.
The window on the south side of the house is the largest, this is because in North America, The sun is always in the southern hemisphere. The roof overhang is long enough so that when the sun is high in the sky as it is in summer, the overhang blocks the sun from the window. This process will keep the temperature of the house cool. In the winter when the sun is lower in the sky, all the sunlight shines on the window, keeping the house warm.
Since you want to conserve energy as much as possible, the windows will be insulated windows. These windows are made up of two panels spaced a certain distance apart and filled with Argon gas. The reason for using Argon is because the gas molecules transfer heat slower than regular air molecules.
The lighting in the house, barn, and outdoors will be completely LED. Although LED lights are more expensive to purchase than incandescent bulbs, but LED bulbs last much longer and are more energy efficient. A regular incandescent bulb takes about a 100 W to glow, but LED lights only require 5 or 10 W to operate which is significantly less. This translates to less energy used and less money spent on electricity. The most attractive aspect of LED lights is their life time, on average these lights can last for eleven years. Between the low energy use and the long lifetime, LED lights are much more efficient than incandescent bulbs.Four 5 W bulbs indoors and 4 10 W flood bulbs outdoors should be sufficient to meet your lighting needs.
Why do you need flood lights outside?
LED Light Bulb
LED will not only be used for lighting, but for water purification. Since the water is coming from a stream, there may be harmful bacteria present such as that which causes diarrhea. This means that the water is not suitable to drink, thus you must purify it. UV rays are very energetic
photons which can
penetrate bacteria cells and destroy their DNA, thus making the water safe to drink. Waterproof eight of these single watt lights and install them in your water storage tank to kill any bacteria. These lights will run 24 hours a day.
A utility that most Americans would agree is necessary is a hot shower. To achieve this you need to have water heater hooked up to your water supply. An average water heater uses energy to not only heat about 50 gallons of water, but it must also keep the water at this temperature until it is used. A more efficient method than a traditional storage water heater is a tank-less "point-of-use" water heater. This type of water heater turns on only when you turn on the hot water. Electric current heats a copper heat exchanger, and
water is circulated through the copper heat exchanger providing an endless flow of hot water. When you are done taking a shower or washing dishes, the tank-less water heater will shut itself down until it is needed again.The a good small tankless heater for your house is the Bosch Powerstar AE.2. At 7.2 kW, this unit uses more power when activated than any other appliance you will use, but it also has a "Low" 3.6 kW setting. You will be using two of these water heaters, one for the sink and the other for the shower. This water heater cost $
229.95, since you need two the total price will be $459.90
Is your system going to be able to handle 70 amps? .... or 140 amps if you run both water heaters at the same time? Have you considered solar water heating?
Tank-less Water Heater
From your man made pond, that you dammed from the stream, you have a water pump that pumps the water to the house so it can be used. A good water pump to use is the Shurflo 2088 Delivery Pump. It outputs 3.6 GPM and runs on 24 volts DC, and can lift water up to 100 feet. It has a self triggering pressure sensor, which you should set to 45 PSI. The cost of this water pump is $176.00.
Water Pipe Heater
In the winter, when the temperature drops below freezing, you don't want your water pipe from the pond to freeze. To prepare for this, wrap the pipe in heavy insulation, and bury it several feed underground. If where you are living suffers extreme weather you may need a water pipe heater.The specific water heater being used is the WinterGard 3 Watt 120V #H-311 Heat Tape. WinterGard heat tape is designed to be used at 120V AC using 3 watts per foot.
The total price a 100 foot pipe heater system is $377.15.
Power and Energy Consumption
Below are all of the electrical appliances and fixtures that you should have in your house, with number of units, power ratings, and estimated duty cycles. The total output load is calculated form these raw numbers, but your actual energy needs are increased by two factors. The batteries have about a 95% efficiency, and the electrical control systems which match voltages, control automated units, and invert to AC power for the pipe heater have an estimate 80% efficiency.
power rating [W]
forced air heater
Energy Use [kWh/y]
To meet these needs, you will need to utilize renewable energy in form of hydroelectric and PV solar generation.
In a city clean water is delivered to your house through pipes from a water treatment plant. In rural places there is no such luck, however, you still want the luxury of running water from your faucet. The house is located near a stream and so this will be your water source. Water and potential energy can be used to get mechanical energy, this is in principle what a waterwheel is. You dam the stream and use a waterwheel as a regulator of the flow from your dam to the stream. The waterwheel creates power which will be connected to a batteries to charge it. The batteries will be used to power any of the utilities.
Assume a creek that is 3 meters wide and an average of 10 cm deep, flowing at half a meter per second. To build up the head, you must build a dam. Cinderblocks would make a good cheap readily available material for building a dam that was sturdy but could be easily repaired on the fly if damage occurred, without needing to drain the creek. Let the dam hold half a meter of head behind it. A Breast-shot waterwheel design (shown) with a 1 meter diameter would be preferable for this application, because it is more efficient than an Undershot wheel and doesn’t require a slough. Connect the wheel to a small waterproofed permanent magnet generator. If the allowances around the wheel are tight, such a system can easily achieve 50% efficient power generation. This would produce:
PV Solar Power
: The location of your hermitage is in the state of Kentucky. The average solar irradiance in this area is a little above 4.0 kWh/m2/day. You will need eight 1 meter by 1.7 meter polycrystalline solar panels rated for 235 Watts. Mounted on the south-facing (front) side of your roof or on tall stilts, and tilt them at 70 degree angle to the ground to maximize power in the winter when the sun is lowest. Make sure they are clean and free of shadows, dirt, and snow at all times.
The power rating of the panels is for 1 kW/m2 laboratory conditions. The efficiency of these panels can be easily calculated from this:
Individual panels with this efficiency on an average day in your location will produce actual power at:
The deficit power load after you build your waterwheel is 225 Watts. To fill this gap you will need 6 of these solar panels, but this is for an average day. By using 8 you can still meet your average daily needs if the solar irradiance drops below 3kWh/m2/day without dipping into your battery reserves.
Your power production capacity will drop greatly at night when your solar panels are not functioning, but night time will be when you will likely use the most electric energy lighting and especially heating your house. To fill in the gaps where your production and load don't match up, you will need a battery system for your house. The best battery to use is the Rolls Surrette S460 Battery, which is designed specifically for solar and other alternative energy systems. This battery features a high cycle life with thick positive plates and a large liquid reserve. These batteries are rated to have a 10+ lifespan, and come with a 7 year warranty.
Design your electrical system so that the solar panels and waterwheel both feed directly into the batteries, and all of your electrical needs are powered from them. Because the batteries have about 95% energy efficiency you do lose some energy this way, but this is the simplest way to ensure that your batteries are always charging if there is extra production capacity. Suppose, however, that something went horribly wrong and both your solar panels and your water wheel were offline. This could happen if there was a very bad storm that broke your dam and blew away or damaged your panels. Your batteries would be able to support your electrical needs while to wait out the storm and make repairs, but only for a limited time:
If you continue using power at your average load:
Your batteries are rated at,
If you operate on emergency power, drawing o
nly almost the lowest current the batteries are rated for:
This is sufficient to power UV lights, water pump, and water line and biogas heaters at nearly normal load if heaters are cycled on only one at a time.
Below is a spreadsheet that models your electricity production and consumption. Change the parameters that are boxed to see how your power system will operate under different scenarios and circumstances.
Food Preparation and Preservation
With no grocery store in sight, you will need to grow everything that you eat, including meat. Plant and maintain a vegetable garden near your home
Choose root vegetables that are hardy like carrots and potatoes, or that can be dried and stored long term like beans and peas so that you have a steady food supply.
Goats are great sources of meat protein, and the does can be milked once they have thrown a kid. The meat is lean and nutritious, but may taste strange to someone who is used to beef. Goats are much easier for a single person to manage than a herd of cattle, however. You will need to grow and harvest enough alfalfa or hay to feed them, and straw for bedding, but a herd of 10 goats will consume a great deal less feed than a herd of 10 cows. Also, goats are foragers like deer, not grazers like sheep and cattle. This allows them to supplement their own diet with available things like bark, sticks, roots, and leaves. They are good jumpers though, especially the bucks, and can easily clear a fence that is built too low. Their enclosure should be very strong too, because goats will ram into wooden fence posts repeatedly until they break or fall over. Place stakes very close together, and run a wire every few inches. They will need a barn to sleep in, with about 16 square feet of space for each goat. Allowing space for 20 goats, as well as about 50 square feet for you water and gas systems which should be kept inside, build your attached barn to be 15 feet by 25 feet. Insulate it as well as you insulate your house, top to bottom
: A small orchard of apples, apricots, and other tree fruits will provide you with fruit for a more balanced diet, the wood from the trees will also be a perfect fuel for the smoker. The leaves from pruned limbs can be fed to your goats. Also it provides shade to the goats on particularly hot summer days when they are foraging.
Cooking and Preserving
Most of your cooking will be done on your gas stove, which runs on pressurized Biogas. You will not be able to cook every meal from freshly harvested ingredients, so you must preserve some of your food supply to extend it into winter months. One way to do this for vegetables like peas is just to dry them. Fruits and other vegetables with more water will rot if you try to do this, so you must can them. This is easily done one a stove by adding hot filling to mason jars and closing them. Boil the closed jars in a large pot for a few minutes to remove some of the air, then let them cool in the pot. Foods that are properly canned will not need to be heated again when they are opened to make them food safe, but you make wish to do so to make them more palatable.
You can find two burner biogas capable stoves for about fifty dollars that have 98% burn efficiency and good thermal efficiency, greater than 57% (according to the supplier). You can boost this thermal efficiency by adding a polished stainless steel shield that goes around your cook pot, keep in the hear from escaping around the sides. This may raise your stoves thermal efficiency to about 65% or more.
If you estimate the average amount of energy to cook one meal is about the same as needed to heat 2 liters of water to boiling from room temperature, then your thermal cooking energy needs are as follows
Running a refrigerator requires a great deal of power, but you must be able to preserve your meat. The best method of keeping your food from spoiling is to smoke it. However, there are some disadvantages to smoking your meat. One such disadvantage is that these systems tend to be extremely energy inefficient. Commercial smokers are designed to maximize smoke flavor, not minimize energy use. The other side of the issue is that for a smoker to be effective in drying the meat there must be a continuous air flow to carry away the moisture, which carries a lot of the heat away as well. Also since the smoker is effectively a large piece of metal, it will radiate heat to the environment. You can improve this situation by building your smoker out of high polished steel, which does not radiate very much. Your smoker should also be double walled with heat resistant insulation, to further cut down on heat losses. Build your smoker with a very small fire box at the bottom that can be sealed, but with slats to draw oxygen or a place to insert a bellows. The chimney should also be small, and able to be closed.
Some species of goats will kidd year round, two sometimes even three times a year. If your permanent herd is ten goats with six females, you can reasonably afford to slaughter six goats per year. At 45 kg goat will yield a carcass that is about 50% that weight. About two thirds of the carcass will be meat, the rest bone, connective tissue, and fat. This will give you about 14 kgs of meat, which rationed out will give you 60 half-pound equivalent servings of meat over two months.
But to make the meat last two months, first you have to get all of the water out, and the meat is about 70% water. The specific heat of water is 4180 joules per kilogram per degree heated, and figure that your meat is heated about 80 K from room temperature to boiling. The heat of vaporization of water is 2.26 million joules per kilogram water, and you will want to vaporize as much of the water from the meat as possible.
If your smoker is efficient enough, it is reasonable to expect at least 3% of the heat from the fire box will go to heating and drying the meat. From this your thermal energy needs for smoking are estimated to be:
The heat value of aged dry firewood is 15.7 MJ per kilogram, so:
Wood is not a renewable resource, but this estimate shows that with a high efficiency smoker design you would only have to gather and dry about 160 pounds of firewood every year to fill your needs, which is not very much in the grand scheme. Your fruit orchard will need pruning to keep it healthy and improve the harvest, so if you can use this wood instead of cutting down existing trees all the better.Another disadvantage of smoking as the prime method of food preservation is that, it causes pollution to the environment. Burning one kilogram of wood releases:
Despite these environmental drawbacks, smoking your meat the best method for preserving it long term
For those times when you want to bake your food instead of purely using the stove, you can use a solar powered oven. Using concentrated sunlight to heat food you can bake a chevon roast or bake some apples for dessert. This will help to reduce your gas needs in sunny weather.
Gas cooking is easy and cheap for someone connected to a city gas main. For you, it will have to be easy and free, and you have no gas main. To accomplish this, you will build and utilize an Anaerobic Digester for producing biogas. Anaerobic digestion is the process by which methanogenic bacteria breakdown organic digestible material in an oxygen depleted environment, producing methane and carbon dioxide gas as a byproduct. To harness this you need three things: digestible material, a completely airtight digester/collector system, and methanogenic bacteria. The first and last two are easy, because your goats' manure makes great digestible material, and contains the bacteria that you need. The digester system you will need to build yourself, because they are not commercially available (yet?).
One way to build such a system is this: start with eight 55 gallon (200 L) steel drums. Clean them of all paint and then polish until they are as shiny as you can get them, like a mirror. You will need to cut several holes in each drum. Each barrel also need an airlock loading chute at the top. This will be complicated to achieve, but it is extremely important. You could use a tube with independently opening ends, or a hopper and a hand cranked wheel with vanes that scoop material from the outside and deposit it inside without exposing the interior to oxygen. Each barrel will need a central mixing shaft with a turning mechanism. Attach lawnmower blades to the shaft to mix and liquefy the material inside. Cut a hole at the bottom and attach a watertight valve for emptying the effluent. Cut another hole in the top for the gas line to attach. Each barrel will also need to be outfitted with a DC heater and a thermostat set to 100 degrees Fahrenheit, because this will ensure that the correct bacteria are thriving. Heat the barrels
from the inside
instead of the outside, because the high polished steel will keep in heat very well, but it will also keep Out heat. The reaction that produces the gas is exothermic, but you will need to supply it with some heat, especially to get it started. Each of these barrels will cost about $1500 to construct.
The barrels that are actively producing gas will need to be connected to something that can store and pressurize the gas for use. Since a compressor uses a lot of power, use the "floating drum" method. Obtain or commission two very large round plastic basins, about 10 cubic meters each. One should fit neatly upside down inside the other, but not so snug that it won't slide. This is the top. Cut five holes in the side of this one for gas inlets, and one for an outlet. Place it in the empty bottom basin, and fill the bottom so that as much air as possible is expelled from the top. Attach lines to the gas inlets and outlet. When the barrels begin to produce gas, the top basin will float and contain it, and the weight of the top will keep the gas at a constant pressure. Monitoring the level of the top drum lets you know how much gas reserves you have. If the pressure is not high enough you can add weight.The containment reservoir will cost an estimates $1000. With this, the eight digester barrels, and eight DC heaters the entire system will cost you $13400 total.
Goats defecate five percent of their body mass per day. Not all of this can be collected because you will need to let the goats out of the barn to forage for food. It is reasonable to suppose that you should be able to collect at least 10% of their manure. If your herd is ten 100 pound goats:
Assuming a similar density to water, this gives you about two and a quarter liters of manure per day
Lab results indicate that it is possible to produce 10 liters of biogas per month from two liters of slurry made from goat manure, food trash, and water. At least one of these barrels should be outfitted with an attachment that allows you to flush your own solid waste into it. Human waste is not particularly good for producing biogas as it is too high in nitrogen but it is not useless. This tank will need to be supplemented with additional digestible material. The slurry should be 95% water for optimal gas production. Your steel digester barrels are 200 liters each, so you will need 10 liters volume of manure and food trash to fill one barrel. You can also supplement the food trash with dirty bedding from the goats as this will make good digestible material. You should be able to come up with this much material easily within a week. Each barrel will need to wait for about 15 to 25 days before it will begin to produce gas. Once a barrel begins to build up pressure, hook it up to the main storage tank. With five barrels producing gas:
5 cubic meters is more than your estimated cooking needs, so by this estimate you will be more than able to feed yourself a delicious, food-safe diet.
Each filled barrel will produce gas for about 40-50 days before you will need to replace it with a fresh barrel, so you should have 3 backups standing by. The effluent that remains in the barrel after it is depleted has more available nutrients than the raw material that went in because of the digestion process, so it will make your garden and orchard flourish. Digestion also reduces or eliminates disease vectors and is less attractive to flies, so collecting and processing the goat manure and trash in this way can help to keep you and your goats healthy.
Extremely remote land can be found in appropriate climates in the midwest for about $87,000. Assuming construction costs of $180/square foot, this home will cost you just under $200,000 to build.
Your energy consumption is in two forms, electric and thermal from wood and gas. Per year you will use:
Compared to the US average per person energy consumption of 10,300kWh/year, you are cutting your energy use by about half.
Your carbon emissions come from burning biogas which is a mixture of methane and carbon dioxide, methane emissions from your goats. Burning wood does not emit net carbon because those emissions go into the air when the wood decomposes, though burning does speed up the process. The biogas you use is 60% methane, and you can estimate about a 95% reduction or more of your methane emissions from your goats, because you are collecting their manure and using it for fuel. Methane is about 20 worse of a green house gas by mass than carbon dioxide, so your carbon emissions per year (in kg carbon dioxide equivalent) are:
The average per capita carbon emission for the US is close to 16,700 kg carbon dioxide equivalent, so you will cut your carbon footprint by to one quarter by living this way.
This is no way to live. It would be lonely, would require an incredible amount of technical knowledge including farming, electrical engineering, ranching, and construction, and would leave you without access to medical care. This lifestyle is strictly subsistence living, leaving you with no income. If you can maintain zero contact with the outside world, it may be possible to live like this for a while, but once your batteries need to be replaced or a super-expensive insulated window breaks or you get sick, things will become very hard for you if you don't have any cash.
That said, this is really intended to be more of an elaborate thought experiment. If you are inspired by it, find what elements of it you like and incorporate them into your lifestyle now. Biogas digesters are becoming popular among American farmers and have been used much larger scales by waste management facilities for some time. Countries in Europe and South America have been using tank-less water heaters since the 70's; it's only here in the United States where our energy has always been so cheap that they never caught on. While not everyone can build a waterwheel in their backyard, many people have unused roof space that is ripe of PV Solar. In the coming decades, rising energy costs and climate change issues are not going to go away; they are much more likely to become bigger and bigger news. Why not get a head start on the curve?
Heater for Anaeronic Digesters
Tankless Water Heater
Forced Air Heater
Anaerobic Digestion Article
Wood Heating Value
Average carbon emissions
Average Energy Use
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