Resilience Through Functional Design
In the Introduction to Appropriate Energy, energy is defined as the ability to do work. There are three jobs that energy typically performs: moving heat, moving things, and moving electricity. This article delves into the moving electricity function that energy serves. Examples of various techniques and specific elements are provided to illustrate different ways to move electricity.
The techniques and elements described below are context-specific, meaning they efficiently and sustainably provide for the desired function at the specific site that they were designed for. They are not one-size fits all techniques – and in fact, what may work well at one site may be a poor fit for another site right next door. Before any energy system is designed (ideally as part of a whole site design process), the intrinsic characteristics of a site should be thoroughly compiled and assessed so that the extent of the energy resources available are well understood.
Moving electricity is used to do tasks that are almost impossible to do in other ways, such as computing and communicating over long distances. Before we dive deeper into the work that electricity can do, let’s talk about the title of this post- why did we say moving electrical charge, instead of generating electricity? Unfortunately the field of electricity is rife with more misconceptions than most others in science, and this is one of them. Electricity, or electrical charge, is not generated. It exists in all metals, all the time. Electrical charge does work when it flows, and the faster that the electrical charge flows, the more work it can provide. So, the key here is to move electricity – to pump it – to create current. That’s what generators, batteries, solar panels, and other systems do – they convert one form of energy (such as mechanical and chemical) into electrical current.
There are three common ways that electrical charge is moved in order to do the modern jobs that it does:
- Chemically – chemical reactions (such as those that occur in a battery) are converted into electrical movement. This can be simply achieved using two different metals and an electrolyte solution such as saltwater. (Awesome video using magnesium, graphite, and seawater here).
- Photovoltaically – reactions between sunlight and chemical elements are converted into electrical movement; in some ways, also a chemical process.
- Mechanically – mechanical energy (such as the rotational energy of a turbine or an internal combustion engine aka “generator”) is converted to electrical movement using electromagnetic induction motors, which can be made simply with as little as an iron magnet and a length of copper.
Movement of electrical charge can be achieved simply by using two different metals and an electrolyte solution such as saltwater, or the use of a magnet and length of copper wire. However, while these and other “simple” examples of building these at home have been linked above, all of them require access to mined and processed metals – metals that most of us don’t have sitting around for the easy mining and processing on our properties. This explains why intentionally moving electrical charge to do work only became a reality in the industrial age, when materials were able to be mined from one location, processed, and then distributed throughout the world. This should also highlight the complex and energetically-intensive processes that go into doing work with electricity – far more complex than burning wood to move heat for example – and thus why using electricity to produce heat is such an inefficient use of energy.
So, knowing that we’re not likely to create devices for moving electricity using materials found in our backyards, how can we intelligently leverage the incredible value that those purchased machines provide on our own properties? We start by minimizing our need for moving it! Using the principle discussed in our Introduction to Appropriate Energy – match locally-available sources to end use in the fewest steps- if you can do something without using electricity using locally-available energy sources, do that first! If there is a need to move heat on a property, try and do so with the warmth of solar radiation first; if supplemental warmth is needed, use the stored energy of sunlight in the wood from the deadfall in your local forest or intentional fuelwood plantings on your property. If you need to pump water, utilize gravity to do so if at all possible; if unable to do that, try to utilize mechanical means – say, a handpump or windmill if you live in a particularly windy area. If you need to use light, consider burning wood, beeswax candles, or oil lamps (can run off of waste animal and vegetables fats procured from local restaurants!).
However, there are some things that just can’t be done any other way – such as computing or communications. And we live in a modern world, and most of us will likely want the conveniences of on-demand lighting with steady output at least at some moments. For these, electricity is the only way. So we then move to the next step – producing electricity from locally-available sources using globally-sourced machines. Let’s revisit the three main ways of doing that…
Chemically-Driven Electricity Pumps (AKA Batteries)
Chemically-driven electricity pumps are most commonly referred to as batteries, and they move electricity as direct current (DC). This direct current can be either utilized as-is by the many DC appliances and devices that exist, or inverted (at an efficiency loss) into an alternating current (AC) for AC appliances and devices. Because of this efficiency loss in the DC-to-AC inversion process, DC end-uses should be chosen wherever possible if batteries are used as the primary means of moving electricity at a site! This is especially true in an off-grid application. More on this in the “Device Charging” and “LED Lighting” sections below.
A drawback of batteries is that they come pre-energized with a set amount of electrical charge that can be moved – once this charge has been used by the various end-uses, the battery is depleted. Modern batteries however can be “re-energized” using an external electricity pump. This pump can be a solar photovoltaic array (which is ideal from an efficiency standpoint, as the solar PV array moves electricity in the DC form that is required by all batteries), or an electromagnetic induction motor driven by a wind, hyrdroelectric, or other turbine, or an internal combustion engine. More on these in the “Mechanical Electricity Pump” section below.
Even in applications where a utility grid-connection is available, we often still recommend batteries as the main system of moving electricity, with a local energy source (such as solar PV array or wind turbine) providing primary battery energization, and the utility connection as a backup energizing source (during prolonged periods of overcast/still weather, or in the event of equipment failure). Transfer switches can be used in a system like this to automatically switch from the battery energization source to the utility connection.
Even if a landowner prefers to maintain the utility grid connection as a primary way of moving electricity, batteries can still be used to automatically take over as the primary mover of electricity to on-site end uses when utility time-of-use on-peak rates are higher in order to reduce costs. This time-based shifting of energy sources in order to maximize off-peak electricity rates is called “load shifting”. A battery bank used in this type of system can also be used as a backup electricity pump in the event of power outages (which are becoming more common in our California region as utility companies are utilizing rolling blackouts as wildfire prevention). A unique type of inverter called a “storage-ready” or “hybrid” inverter, like the Outback SkyBox Hybrid System, may be required to take advantage of load-shifting depending upon which battery bank system is used in a grid-tied setting.
Most battery bank systems in recent decades were constructed with lead-acid batteries. However, the use of much longer-lived, though initially more expensive nickel-iron batteries is recommended at WFH to create a battery bank with a near indefinite lifespan. Nickel iron batteries were first patented by Thomas Edison in the early 1900’s, and have been around for the past century in a number of different industrial applications. They have been enjoying a resurgence amongst off-gridders and homesteaders in recent years. Nickel iron batteries have incredibly long lifespans when properly cared for, some are still operating today from the 1940’s. Nickel-iron batteries can also handle repetitive deep discharges, up to 80% with no ill-effect on battery life (as compared to the 50% recommended for lead-acid batteries, meaning a smaller capacity bank can be used), as well as overcharging, and they operate well in both extreme cold and extreme heat. For more information regarding the design and emplacement of Ni-Fe battery banks, visit IronEdison.com.
Another option worth looking into is the Lithium Iron RE-Volt battery manufactured by Iron Edison. The RE-Volt is a sealed, maintenance-free battery solution with 20-year life expectancy, and is completely recyclable upon end-of-life. An integrated battery management system prevents damaging overcharging or over discharging. Up to fifteen batteries can be paralleled, providing up to 150 kWh of capacity.
Photovoltaically-Powered Electricity Pumps
Solar photovoltaic (PV) arrays move electricity in the form of direct current (DC) as long as they are exposed to solar energy, making them great for end-use applications that occur during the daytime. The two applications that we most often recommend solar PV arrays for are the energizing of batteries and pumping water uphill for gravity-pressurized use (if means of mechanical pumping at the site are not available, feasible, or desired).
In the energy systems we have designed and built using the principles presented in earlier parts of this series, we have found that a 600 – 1,200 watt solar PV array is sufficient to cover the electrical needs of a single-family residence – as opposed to the 2,500-5,000 watt arrays commonly prescribed for conventional residences.
Mechanically-Driven Electricity Pumps
Most mechanically-driven electricity pumps use an electromagnetic induction motor to convert mechanical energy into moving electrical charge. This mechanical energy is commonly provided by a turbine (converting the linear energy of wind, moving liquid and gases, etc into rotational energy) and by an liquid- or gas-fueled internal combustion engine (“generator”), among other ways.
Like solar PV panels and sun, mechanically-driven electricity pumps only move electrical charge when they are in motion, making them great for end-use applications that can be timed for when that mechanical energy is present. When a site has an energy source consistently flowing through it like flowing water or geothermal energy, AC end-uses should be chosen wherever possible to match the AC current produced by most electromagnetic induction motors. At a site with a sporadic, inconsistent energy source flowing through it like wind, mechanical electricity pumps like wind turbines are most commonly recommended for the energizing of batteries in order to provide a more consistent and reliable means of moving electricity. Liquid- and gas-fueled internal combustion engine-driven electricity pumps like gas, diesel, and propane generators are also often recommended as part of the energy system at sites we design, but their use is only recommended as a backup means of battery energizing or for temporary uses in remote locations due to their requirement for the ongoing import of fuel.
There are two main types of generators: conventional and inverter. Conventional generators provide AC electricity directly, although it can be of poor quality under constantly varying loads (like variable speed motors or loads turning on and off quickly) and poor efficiency under part load, while inverter generators produce very clean high quality AC power for varying loads and operate with relatively constant efficiency. Both generators are comparably efficient at full load. Conventional generators are also cheaper, more simple to repair, louder, and bulkier than inverter generators.
Generators are also mainly available in three different fuel types: gasoline, diesel, and propane (there are also dual-fuel models available that run on both gasoline and propane). These are compared below:
|Generator Fuel Type:
|Liquid Propane Gas
|Slightly higher on a per-watt basis, but not available in lower-wattage outputs
|Fuel System Installation and Storage Cost
|Varies(low cost in small sizes)
|Varies(low cost in small sizes)
|Moderate(if adequately sized tank already at site)
|Fuel Storage Duration
|Fire and Safety Concerns
|High(highly flammable, vapors poisonous)
|Low(high flash point)
|Low-Moderate(rare leak or tank explosion risk)
|High(spill risk, exhaust not clean)
|High(spill risk, exhaust not clean)
|Moderate(easy to purchase)
|Moderate(must be delivered and stored)
|Moderate(must be delivered and stored
|Cold Starting and Operation
|Poor(forms gum deposits)
|Moderate(hard starting at cold temperatures)
|Excellent (no tank vaporization issue)
|Engine Life and Durability
|Poor/Moderate(depends on engine type)
7th Generation Design generally recommends propane-fueled generators due to their low cost, ability to store fuel indefinitely, and relatively clean-burning exhaust.
To charge the battery banks and power any DC devices hardwired to the battery bank (in the ADUs, Woodshop, and Classroom Zone) using the generator, a converter/battery charger will be required.
Interior and Exterior Lighting
Ideally, a site (and it’s contained structures) have been designed so that no supplemental light is required when the sun is shining. However, there are inevitably applications at nearly every site where supplemental light is required – if even only at night. If a site has no locally-available energy sources that can produce light in a single step or two (such as wood, beeswax, or vegetable/fruit/animal fats), or if those systems for providing light are simply insufficient or undesired, then electricity is typically the only remaining energy source that can be converted into light. While many options exist for this, including incandescent and fluorescent, light emitting diode (LED) lamps are the most efficient (they use approximately 90% and 30% less energy than comparably bright incandescent and fluorescent lamps, respectively) and have a lifespan that is many times longer.
The LEDs in all LED lamps require direct current. At a site wired for utility grid-supplied alternating current, LED lamps with a built in converter that converts the alternating current supplied to the fixture to the direct current required by the LEDs must be used, at an efficiency cost. Since most houses are wired for AC, this is the type of LED lamp almost universally found in stores. These types of lamps are typically only recommended by 7GD in the context of a site where the landowner plans to maintain their grid connection as the primary means of moving electricity throughout that home, or a site supplied with consistent alternating current by some other means (such as hydroelectric).
At sites where electricity is primarily supplied as DC (batteries, solar PV panels, etc) utilizing these conventional LEDs first requires inversion of the DC to AC, which is subsequently rectified from AC back to DC – all at a huge efficiency loss. These inefficiencies can be avoided by powered the LEDs directly from the source, eliminating any and thus reducing the battery bank and/or solar PV array’s size requirements. LED light fixtures designed to be hardwired directly to a DC source, like the one shown below, are not typically found in stores, but can be found online.
For sites with existing incandescent or fluorescent lamps, we typically recommend replacing them with the more energy-efficient and longer-lasting LED lamps upon reaching end of life.
Computing, Communications, and Entertainment Devices
Most if not all computing, communications, and entertainment devices (including computers and phones) are entirely comprised of components that utilize direct current electricity (DC). In structures laden with the wall outlets that we are all so familiar supplied by utility grid-supplied alternating current (or perhaps hydroelectric, if you’re so lucky as to have that source), “rectifiers” (also sometimes called transformers, converters, or power supplies) must be used to convert the AC supplied to the outlet to the DC required by the devices, at an efficiency cost. These are the black “wall warts” found at the end of the power cords for older devices, the hot and heavy plastic-encased units found spliced into the middle of computer charging cords, and the USB wall plugs used to charge cell phones and tables. And since nearly every house that has been built in the modern era is wired for AC, (even houses with batteries and solar PV as their primary means of moving electricity), nearly all devices come out of the box ready to accept an AC power supply and rectify it to DC.
However, at sites where electricity is primarily moved as DC (batteries, solar PV panels, etc), these rectifiers can either be bypassed or devices designed specifically for the DC power supply can be chosen in order to maximize efficiency. These devices are often marketed to the RV world, where battery banks are consistently found, but are beginning to be marketed to the off-grid housing sector.
For the USB-powered devices we own (like the cell phones and tablets), USB plugs that wire directly to a DC source are widely available. How do we power our other computing, communications, and entertainment devices that don’t charge via USB though, like our computers? This is where the 12VDC socket comes in.
While they can require some searching, some third-party manufacturers have designed prefabricated laptop charging units that plug into a 12VDC automotive socket and convert from the 12VDC supplied by the battery bank and/or solar PV array to the DC voltage required by the device, with the appropriate charging plug required by the device. Two of these units are shown below, with links in the captions.
The word “appliances” usually refers to stoves/ovens, refrigerators, washing machines, dryers, etc.
We’ve already noted multiple times throughout this series that electric heat should be avoided except in the most unique of circumstances, and thus stoves and dryers that utilize electricity to move heat should be avoided. For other recommendations regarding cooking, please see our Moving Heat post.
While non-electrical alternatives exist for the remainder of the appliances we’ve listed (which are discussed further in Parts 1 and 2, Moving Heat and Moving Things), most of us prefer the conveniences and speed of modern electrically-powered versions. The electricity used for these appliances is used to drive the motors, and since almost every house in existence is wired for AC (even the ones that primarily utilize batteries and/or solar PV to move electricity), those motors are typically designed for AC.
For the landowner who prefers to maintain their utility-supplied AC connection or has onsite or nearby hydroelectric as their primary supply of electricity (or perhaps a wind turbine, if the landowner has the flexibility of using their power tools when the wind is blowing), appliances with AC motors are recommended.
However, at sites where electricity is primarily supplied as DC (batteries, solar PV panels, etc), appliances and tools that utilize DC motors should be utilize wherever possible. There is currently a relatively small selection of DC-motor equipped refrigerators, washers, and dryers available to come by, but they are becoming more widespread. These are nearly always hardwired directly to the batteries and/or solar panel array, however a plug of some sort could be used, including the 12VDC plug discussed above.
For those appliances that are only available with AC motors, an inverter can be used to invert the DC supplied by the batteries and/or solar to AC. There are two types of inverters: modified sine wave and pure sine wave. Pure sine wave inverters are the more expensive of the two, but produce a better quality output (minimizing risk of damage to electronics) at a higher efficiency, and thus are recommended by 7th Generation Design for all applications. These inverters can be purchased as standalone units, like the unit shown below, or in combination with an AC-to-DC charger, allowing for backup energizing of the batteries with a generator or grid connection.
As discussed further in Part 2: Moving Things, drill bits and saw blades can be moved mechanically by a variety of sources, including human- and animal-power, windmills, and waterwheels. These mechanically-powered tools can be surprisingly efficient as well, and are certainly worth investigation – especially from an environmental standpoint. However, the convenience and speed of electricity-powered tools is undeniable.
For the landowner who prefers to maintain their utility supplied AC connection or has hydroelectric as their primary supply of electricity (or perhaps a wind turbine, if the landowner has the flexibility of using their power tools when the wind is blowing), tools with AC motors are recommended. These are the “corded” tools, and interestingly enough, in this category of electricity end-uses they are fading out slowly in favor of DC motor-driven tools.
This expanding variety of DC motor-driven tools is occurring due to advances in rechargeable battery technology, and is fortunate for landowners with DC as the form of their primarily electricity supply (batteries, solar PV panels, etc). However, to maximize the efficiency possible through matching the DC battery-powered tool with the DC power supply, the AC-to-DC charging unit that comes with the purchase of every major tool manufacturer’s battery must not be used, and a specialty DC-to-DC charging unit used. Fortunately, several tool manufacturers have released these for use with the 12VDC socket shown above.
That’s a wrap on our overview of potentially appropriate technology for Moving Electricity on a homestead! We’ll be continually updating this with new information. Please leave a comment below, and make sure you check out our Introduction to Appropriate Energy if you haven’t already and the rest of this series, Part 1: Moving Heat and Part 2: Moving Things!
And if you would like help designing for the energy needs of your site, please reach out to us!