Recently we bought an off-the-grid, boat access waterfront cabin to use as our vacation house.
Currently, it’s powered mostly by propane but has a couple of solar panels. There’s a generator that came with the property for use in a pinch.
While propane can work and there’s a service that tops up propane for all the boat-access houses in the area, we prefer to look for something renewable and sustainable that will save a lot of money in the long run.
We’ve been talking to off-grid power source consultants, other folks living off-the-grid and reading extensively about it. We hope to start investing in something within the year.
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How to measure electricity
If you’re new to this stuff, it helps to get an idea how electricity is measured and how much you need. In other words, when talking about kilowatts generated, what on earth does that mean and is it enough?
Electricity is measured in watts (W) of power. The more common unit is kilowatt (kWh) which is 1,000 watts. A megawatt is 1,000,000 watts.
How much electricity in kilowatts does a house use in a year? According to the U.S. Energy Information Administration (EIA) it’s 10,649 kWh per year.
Accordingly, for any off-grid power source discussion, understanding how much kWh you need is important as it’ll dictate the type of power source and how big of a system you need.
List of the best off-grid power sources
Fortunately, there are quite a few off-grid energy options these days. Based on my conversations with consultants, folks living off-the-grid already and my research, here are the options.
1. Propane
Currently, the lion’s share of power to our off-grid, boat access cabin is propane. The property came with a large upright propane tank similar to the one pictured above. Apparently, it lasts pretty good and since we won’t be living there year-around, it’ll work for the time-being. But our goal is to get moving toward something that provides much more energy for a far lower cost without relying on any fuel source.
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1 gallon of propane generates 27 kWh. If a regular house uses 10,000 kWh per year, you would need 370 gallons of propane per year. A regular 20 lb. propane tank holds 4.6 gallons of propane. That means going through 80 twenty-pound propane tanks per year. That’s a lot of propane which is why the following power sources are so attractive.
Propane and Liquid Petroleum Gas (LPG) are well-known sources of industrial and domestic heating. Being fossil fuels, they are not usually listed with renewable sources like solar and hydro. Yet, they are practical tools for going off-grid.
While natural gas is delivered through an underground grid, propane is stored in a self-contained tank. Both LPG and Propane are available in smaller, portable cylinders. Either way, the system works by reticulating gas from a local store to the appliances that need it.
For efficiency of storage, the gas is stored as a liquid. LPG and propane have a 270x liquid to gas expansion ratio, increasing the volume of fuel held by a unit of space. The liquified gas is decompressed on exiting the containing cylinder or tank, consumed by its target appliance.
So-called “wet” valves allow the gas to leave the container in liquid form. This is sought-after in high-energy applications, where the consuming appliance requires a high amount of energy. Delivering in liquid form concentrates the gas, providing the necessary yield to the device.
Because of their history of widespread adoption, LPG and Propane gas are universally available. Fixed installations can be replenished by truck, with direct decant into the home installation. Alternatively, users may exchange empty cylinders for full.
Application
Gas is not a total solution for going off-grid, as there is a limit to its power appliances. Despite the availability of gas lamps, home lighting is not a domestic application. A representative list of gas appliances is:
- Geysers
- Stoves
- Ovens
- Heaters
- Refrigerators
- Generators
The availability of gas-powered generators makes for an effectively expanded list, as appliances like personal computers might be driven by the generators even though they cannot be powered directly by gas.
Using gas might not cover all your needs, but it is a readily available source that will reduce your overall electricity demand, thus lightening the burden for other sources.
The variety and standardization of sizes make it a versatile, scalable solution.
2. Solar Panel System
Solar is a viable alternative energy source whether on or off the grid for most people in the world. It’s better in sunny climates but for us, since we’ll mostly use the cabin in late Spring and Summer, it should get sufficient sun to generate some power.
Solar is costly especially since you need to get an inverter and something to store that power. Tesla wall batteries are a great option but they cost a lot of money.
How many solar panels do you need?
There are many variables such as how much electricity you use and the panel’s power output but generally speaking, you need 25 to 35 panels for 10,000 kWh per year. This article breaks down how many solar panels you need very nicely.
Which explains why the two or three panels on our cabin is totally inadequate.
That said, our cabin is tiny so it could get by with probably half that number.
Breaking it down, on average, a single solar panel can generate 1 kWh per day. That’s 365 per year. If you need 10,000 kWh per year, that’s 10,000 / 365 = 27
How much do solar panels cost?
Again, it depends on how many you need but expect to pay $10,000 to $20,000 for a regular-sized home. If it’s a tiny cabin, it’ll cost less unless the cost to deliver is high (like in our case where it’s boat access only).
Here’s a photo of two Tesla wall batteries:
We’re currently talking to solar providers and installers about this option (in conjunction with getting a micro-hydro turbine system).
CSP vs. PV
Solar energy traps this potential through a combination of light-sensitive panels, mirrors, and batteries. There are two varieties: concentrated solar power (CSP) and photovoltaic (PV).
How Does CSP Work?
At the heart of a CSP system is a heat engine paired with an electric generator. Solar radiation is driven to the engine through concentrators, mirrors, and reflectors curved to focus the sun’s rays optimally.
CSP generates alternating current (AC) indirectly. The incoming radiation is converted to heat. This heat can be fed directly into industrial processes as process heat, or it can drive a turbine to generate electricity. This AC is then distributed through the system or stored in batteries if a surplus is produced.
Its ability to store energy for later use makes CSP a flexible source. The four CSP subtypes are trough, tower, Fresnel, and dish.
CSP Trough
These are the oldest solar power system and still dominate the US sun energy landscape. Unlike the tower arrangement, the collectors are shaped along a parabolically curved tube. The receiver consists of a fluid-filled pipe that overlays the receptors, traversing the focal line of each.
The heat absorber tube contains a thermal oil that is heated to between 550F and 750F. As with the tower configuration, heat from the tube powers a turbine.
CSP Tower
Heliostats are mirrors that rotate to face the sun directly as it travels across the sky (apologies to Copernicus). These heliostats are arranged around a power tower, to which they reflect the captured light. The incoming light is concentrated on a receiver at the tower top.
Heat transfer fluid in the receiver is warmed by the radiation, reaching temperatures above 1000F. This generates steam, which feeds a traditional turbine electrical generator.
CSP Fresnel
This is a derivative of the trough configuration. Here the collectors are linearly arranged in straight parallel rows. Typically they run orthogonal to the latitude of the Earth – an arrangement that maximizes the volume of heat generated during summer.
The collector mirrors are positioned directly on the ground, with the conductor pipe running above them. As with the other CSP modes, battery storage and turbine power are alternative options for directing the harvested heat.
CSP Dish
In a dish configuration, the collector is integrated with a single concentrator. The concentrator takes the form of the dish, whose concavity serves to concentrate solar radiation to a focal point at its center.
This sets the stage for mounting a receiver at the focal point. The dish is mounted on a dual-axis tracker, which tracks the position of the sun. Typically, the heat is used directly by an engine attached to the back of the receiver. Because dish configuration reaches high temperatures, it is favored for applications requiring high-heat fuel.
How Does PV Work?
While CSP, through an indirect AC conversion, relies on the heat/energy of the sun, PV captures a second feature – sunlight. Photovoltaic panels convert light into energy in a natural process. The solar PV panel absorbs light, which dislodges electrons inside the panels.
Electricity is the flow of electrons, and the dislodged electrons inside the panels create an electrical current as they stream together. This current is captured and generates DC – direct electrical current. To create a current fit for network distribution, a PV system is fitted with inverters that convert the charge to AC.
Application
The two main differentiation factors are:
- Scale: CSP systems generate more significant amounts of electricity and are physically large installations.
- Storage: PV systems are incapable of storing their current and are much smaller to produce and maintain.
This tradeoff favors CSP for industrial and smallholding applications, while PV scales more easily into residential environments, where it melds with the domestic budget.
3. Micro-hydro turbine
Because we have a stream behind the cabin with a license to use the water, we’re most keen about buying a micro-hydro turbine system. We’ll very likely complement this with some solar but the micro-hydro system, so we’re told, should provide more than enough power (assuming we also get a good battery for storage as well).
A micro-hydro turbine system is a small system that is placed in a creek or stream where the moving water generates the power. It’s similar to large hydro dam system.
In order to know whether a micro-hydro system will be enough, you need to take some measurements at the site including:
- Available water flow (lps, aka liters per second),
- Pipe length and diameter, and
- Pipe efficiency
Once we have this information we can figure out what size or how many micro-hydro systems we need. This is the next step for us.
How much power does a micro-hydro turbine generate?
There are many variables involved so it’s impossible to give a universal amount. “The amount of power available depends on the dynamic head, the amount of water flow and the efficiency of the turbine/generator combination.” [NoOutage.com]
Check out this micro-hydro calculator to figure out what you’ll need.
Hydroelectric systems convert the flow of water masses into energy. These are derived from dams, rivers, and the sea.
Implementation on a river usually involves a water conveyance, a pipeline to divert water from the stream: the turbine pump and waterfall function as described, with a regulator in place to control the generator.
Micro hydropower utilizes the same physics on a smaller scale. Any property with a regularly flowing water mass is tractable to a micro-hydro solution. These systems typically generate up to 100 kilowatts of electricity. The key components are a turbine, pump, and waterwheel. Some plans include an inverter to make the DC to AC conversion.
Some systems include batteries to store the electricity generated. Batteries are best located close to the turbine, as it is difficult to transmit their low voltages over long distances. Micro-hydro features two turbine classes: impulse and reaction.
Impulse Turbines
These are the simpler of the two designs and the most ubiquitous implementation for micro-hydro. They rely on the velocity of the water, which moves the “runner” (the turbine wheel).
In the Pelton Wheel variation, the concept of jet force is used to create energy. The incoming water is shaped through a funnel into a jet. This jet force is sprayed over cups attached to the runner. This shaped impact rotates the runner at an efficiency rate of up to 90%. The Jack Rabbit and Turgo are variations of the same design.
Reaction Turbines
Reaction turbines have static blades that maintain constant contact with the oncoming water. They respond to pressure – rather than the directional speed of the water – converting pressure differentials directly into energy. These are the turbines of choice on larger plants.
The reaction-turbine variants used for micro-hydro follow the design of the propeller turbine. This features blades configured as in a boat’s propellor. Between three and six pressure-sensitive edges protrude into the stream, propelling the runner.
Application
Instead of hydraulic turbines, conventional pumps can be substituted. This is because pumps carry out the inverse action of a turbine and so are easily reverse-engineered. This is handy as pumps are less expensive and more widely available than turbines. Pumps are more robust – they do not damage easily and perform efficiently.
Micro-hydro scales beautifully. This is a simple and reliable system with hardy components. A 10-kilowatt system can provide enough electricity to supply a large home or a ranch. Smaller systems are in use by homeowners and small business owners.
4. Wind (Micro Wind Turbines)
Micro-wind turbines are pretty cool. You can get portable ones to power up devices when camping… maybe that’s all you need. Or opt for something more substantial (not portable) to provide far more power.
The issue with wind is ensuring it’s windy. You don’t have any control over that so if you don’t get enough wind, this option could be a huge waste of money.
How big does a wind turbine need to be to power a house?
It’s bigger than the example above. You can buy small hand-held sized options to charge devices but if you’re looking to power your home, you’ll need something more substantial… I’m talking a 50 to 100 foot windmill. It’s unsightly and can be noisy. It could also be against code in your area.
Read this example of a house powered with a wind turbine.
Wind power is generated by harnessing the kinetic force of the wind. It is regarded as a form of solar energy, as winds are caused by the sun’s uneven heating of the Earth, in combination with the unevenness of the planet’s surface and its rotation around the sun.
The operant principle in conversion is an inversion of our everyday use of fans. While consumer fans use electrical current to set blades in motion, wind generators use the physical energy of moving blades to create electricity.
Wind energy is generated from constellations of turbines. These mimic the structure of windmills that have been in use for agricultural processes over centuries. Unlike windmills, the deep central silo is replaced by a slender vane, which supports the blades. These are aerodynamically shaped to maximize their friction with the wind.
On a wind farm, sets of turbines are arrayed to catch headwinds over a broad surface area. Incoming wind causes an air pressure differential across the edges of the blade. This causes the rotors (to which the blades are affixed) to rotate in the direction of the pressure. The rotor connects to the generator, which carries out the conversion of rotational energy to electricity. Two types of generator differentiate wind technology: direct drive and gearbox.
Direct Drive Turbines
In direct-drive systems, the rotor fits directly into the generator. This is a relatively new system, having been developed in the nineties. It compensates for the risk of transmission loss and gearbox failure in the rival system.
A price for this increased system safety is performance. The natural turning speed of the rotors is slow, whereas the generators require higher incoming rotational speed to generate their required output frequency. Two types of magnetic enhancement have compensated this: permanent magnetic generators (PMGs) and electrically excited synchronous generators (EEGs).
PMGs are lightweight and small but do require magnetic components made from rare elements like neodymium. There are environmental concerns around the extraction of rare metals. They do enjoy an efficiency advantage over EESG’s, which suffer from field loss.
Gearbox Turbines
These turbines address the slow speed of the rotors by amplifying their rotational speed before they feed the generator. This is done by situating a gearbox between the low-rotation rotor and the high-rotation generator. The gearboxes achieve leverage of 90 times, ramping up the 20-rotation-per-minute natural speed of the turbines to 1,800 rotations.
The price paid for this efficiency is a system at risk of failure due to the torque and physical stress of rotating large objects. Designers address this through load compensation and lubrication. All the while, the system is vulnerable to damage through the accumulation of grit.
Application
The key constraints to wind energy are geographic:
- Wind abundance and variability: Wind farms need situation on areas that do not have prolonged bouts of windlessness.
- Land availability: Optimal installations require a large surface area for several tall turrets to capture a bank of wind.
- Free Flow: The incoming wind must be unobstructed. Any dissipation will reduce the yield or may not cause rotation at all.
The latter points put inner-city areas out of contention. While microturbines are being developed, the wind is not ready for home use, and the scale of an installation requires communal – as opposed to the single owner – application.
5. Small-Scale Geothermal (Mini-geo)
The middle of the Earth is a scorchingly hot place, estimated to be 10,800F, approximately equal to the heat on the face of the sun. The heat reduces in a gradient towards the surface – hitting 392F at the upper boundary of the Earth’s mantle. Geothermal energy exploits this natural resource by extracting subterranean heat and converting it to energy.
Natural geothermal springs emerge at cracks in the surface of the Earth. These form around the edges of the tectonic plates, which constitute the Earth’s surface. Magma – the substance that makes lava hot – is exposed at these edges. It heats water that comes in contact with it, creating a source of energy.
Geothermal Plants
Geothermal plants lend themselves to off-grid applications where a local community or sizeable industrial complex wants to secure an independent energy supply. They constitute a private source for the industry or a mini-grid for the community.
These plants are based on vertical tunnels in which a u-bent pipe traces a path into and out of the ground. Water looping through the tube is heated by the warm Earth surrounding the lower sections of the pipe bend. The surfacing hot water generates steam that drives a turbine.
Typically these plants generate 30-50MW, a fraction of what a conventional fossil-fuelled plant generates. About two dozen geothermal stations are needed to stand in for a 1GW power station. The operating costs are much lower, though.
Geothermal Heat Pumps
At shallow depths, yards below the ground, soil temperatures are higher than the winter air temperature. This is due to natural geothermal conduction and also the retention of solar radiation absorbed by the Earth. This heat source can be exploited in a manner analogous to the design of geothermal plants.
A geothermal heat exchanger is a temperature regulation system fitted directly to a building. It consists of a system of upward and downward pipes conducting liquid between the building and the ground.
The pipes are laid in loops, either vertically or horizontally arranged. During winter, the system pumps heated water from below the Earth to a heating unit in the building. This passes heat in the incoming water to the atmosphere of the building. The process is reversible in summer, with a drop in demand. This uses pumps derived from air conditioning.
Application
The United States regulatory Environmental Protection Agency (EPA) has ranked geothermal heat pumps the most energy-efficient and cost-effective solution for regulating the temperature of buildings. They score highest also for environmental impact. They are versatile in that no installation is off-limits to their application.
Biofuel
Biofuels are diesel-generated through the exploitation of living, farmable organisms. Biodiesels hold the promise of creating fuel from the abundant, low-cost organic organism. It is environmentally safe, renewable, and cost-effective. The development of biodiesels is categorized into three generations.
Generation One
Sugarcane ethanol is a fuel produced by the fermentation of sugarcane juice and molasses. It has grown in popularity as the technology has stabilized, delivering cost benefits. It is considered a clean source and has a low carbon-emission footprint. It adds oxygen in combination with gasoline, reducing carbon emissions in the domains of application.
Global production of ethanol continues to surge. 40% of US-grown corn is destined for ethanol production, with that figure set to grow. Brazil is the worldwide leader in cane ethanol production, and China is bringing excess sugar stock on stream in a fledgling biodiesel program of its own.
Generation Two
Since plant waste is rich in sugar and animal waste contains digestive and other gases, organic waste emerged as a second source of mineable biomass. The attraction of this category is that it does not compete with scarce human food sources, as sugar and corn ethanol do.
To begin energy synthesis from plants, the rigid cellular structure has to be destroyed. There are two processes for this high-temperature and low-temperature deconstruction.
In high-temperature deconstruction, extreme heat is applied to the biomass through three stages: pyrolysis, gasification, and hydrothermal liquefication. The processes differ in the ranges of temperature involved and water use (in the hydrothermal case).
In low-temperature deconstruction, the active breaker is not heat but a catalyst; in the form of either an enzyme or chemical. The cell walls are softened through a pretreatment process, after which the catalysts are brought to bear. This results in simple sugars, which are then processed into fuel through hydrolysis.
Generation Three
There has been a waxing and waning of interest in algae as a source of large-scale, commercially biodiesel. Algae held considerable promise as an improvement over organic waste, but this has been frustrated by technical problems.
A critical problem in the algal process was the drying of the plants. A dry powder was required for the extraction of the energy-rich lipids. But the cost curve could never be bent into shape, requiring more energy than the expected crop yield.
The absolute yield itself was a problem – with farmable quantities never yielding the quanta of energy for commercial use.
While an investment boom ended essentially in bust, research continues to bring these fuels to market. Technical advances are bringing solutions to the technical hurdles closer to fruition.
Application
Biodiesel is harder for the home or small business user to lean on. The technology is in flux, and first-generation ethanol is used to power grids rather than as a retail product like propane.
Algae has off-the-grid potential, as the technology permits private cultivation. This is no practical option for any but the most die-hard home users and would require a small-scale industry of private producers and bottlers to get going before it reaches commercial viability.
While this is likely too expensive for a single house, if you have an off-grid community, the mini-geo concept looks very good.
It’s a modular powerplant about the size of a shipping container that can produce energy 24/7 without relying on any fuel.
Read about small-scale geothermal here. It’s fascinating.
Kinetic Energy
Some solutions have piggybacked on the natural kinetic energy generated through everyday movement. This creates low wattage reserves that can be redeployed.
Empower Playgrounds is a not-for-profit organization in rural Ghana. Founded by a retired engineer, the company installs merry-go-rounds in rural schools. These toys are fitted with kinetic converters that convert the torque from the moving rides into electricity. The charge is stored in batteries that power LED lamps.
The lamps are lent to village children for nighttime reading. Many of them lack electricity at home.
In Kenya and rural Bangladesh, a British company called GravityLight has pioneered a simple solution. A heavy bag lifted off the ground is tethered to a retarding device. This causes the bag to drop slowly to the ground as it does—the motion powers a dynamo, which can keep a light burning for twenty minutes. Recharging is a simple matter of resetting the bag.
Application
The term “off-grid” conjures images of independence from an oppressive utility. This category of off-grid sources targets people who are off-grid of necessity, as their power requirements are not met by a utility. They are not solutions with an industrial application or of interest to more affluent consumers.
Conservation
A necessary prerequisite to going off-grid is minimizing your electricity use and heating requirement. Retrofitting and insulation are key steps in this process. Excess electricity generated by your off-grid system should be stored in batteries and harvested.
The less energy you consume, the broader your options. Personally, I’m averse to the schlepp of lugging gas cylinders. As a suburbanite in a hot country, my preference is for a mix of solar and geothermal. Whatever your inclination, the technology morphs radically over time, and the best combination for your situation evolves with those changes.
6. Diesel generator
There’s always the generator, right? Actually, a generator at a cabin is a last-resort power source. It’s good to have one fully fueled but it’s the last power option we want to rely on just because it’s not easy getting fuel up to the cabin and it’s loud.
Which off-grid power sources are we going with?
We’re leaning toward the micro-hydro plant since we have a stream up behind the cabin (it also serves as our water source). For the money, when moving water is available, a micro-hydro plant is the best deal.
However, we’re also looking into the cost of adding more solar panels as well as backup or in addition to ensure sufficient electricity. The downside to solar panels is it’s not sunny in the area year-around. Summer is pretty good but it’s just outside of Vancouver which is a fairly rainy and cloudy region.
Currently, the place is powered by propane which is not all that great. It needs to be refilled monthly and requires rationing. I’d much rather invest in off-the-grid electricity where it’s renewable and consistent.
References:
- Forbes- 11 Of The Best Microwaves That Perfectly Reheat Delicious Leftovers In Seconds
- Solar Reviews – Off-grid solar systems: An introductory guide
- ResearchGate – Importance of Off-Grid Power Generation using Renewable Energy Resources – A Review
- TechCentral – Going off-grid is easier, and cheaper, than ever
- IRENA – Off-grid renewable energy statistics 2019
- OKR – Policy and Governance Framework for Off-grid Rural Electrification with Renewable Energy Sources
- Today’s Homeowner – LIVING OFF THE GRID: HOW TO GENERATE YOUR OWN ELECTRICITY
- Energy.Gov – Energy Saver Guide: Tips on Saving Money and Energy at Home
- Renewable Energy World – How Solar PV is Winning Over CSP
- Engineering.com – The Future of Wind Turbines: Comparing Direct Drive and Gearbox
- EIA – Geothermal explained
- Fast Company – A Merry-Go-Round That Turns The Power Of Play Into Electricity
