Resilience Through Functional Design
Energy
Moving Things
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 things function that energy serves. Examples of various techniques and specific elements are provided to illustrate different ways to move things.
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 things typically includes spinning fans and motor parts, compressing gases in refrigerators, pumping water, and raising and lowering objects. This is most often achieved by making a shaft spin in a motor or pump, and then translating that rotational energy into linear force or a pressure change. Electricity is the most common power source for this, but fluids (liquid and gaseous) such as water, compressed air, or wind will also do the job. Internal combustion engines, steam, and other turbines are also commonly used to move things, as well as human and animal muscles.
We break the typical residential applications for moving things into four main categories: water pumping, transportation and land development, refrigerant compression, and ventilation.
Water Pumping
Designing for systems to move water ideally starts before any structures have even been built or elements have been put in place at a site, at the very beginning – during the Whole Site Design phase. Taking the time to assess the needs of the site as a whole, determine the elements that will be requires to provide for those needs, thoughtfully place each in relation to each other, and design efficient water patterning throughout the site can significantly reduce or even eliminate pumping requirements.
The ideal circumstance at any site is having a water source that is higher in elevation than the various end-uses (kitchen and bathroom faucets, outdoor spigots, irrigation systems, watering troughs, etc). When the water source is higher than the end-uses, the water can be delivered by gravity – and if it is high enough, it can be delivered to those end-uses at desired pressure and flowrate levels. At most sites however, it is not possible to locate the end-uses below a water source (typically the static level of a well) and thus the water needs to be pumped in order to provide pressurized flow to the end-uses or to a storage system located at a higher elevation than the various end-uses which can then supply water with no need for additional pumping.
Increasing the pressure and flowrate of water can be done using a variety of energy sources. Electric motor-driven pumps (powered by a grid connection, wind turbine, solar photovoltaic panels, and battery banks) and mechanically-driven pumps (powered by human or animal muscles, liquid or gas fuels, and windmills) are the two main options.
Mechanically-Driven Water Pumping
Mechanically-driven pumps utilize mechanical force to move water. This mechanical force can be provided in a variety of ways, including human and animal muscles, harnessed wind energy, and even with other water!
Hand-Powered Mechanically-Driven Water Pump
The simplest mechanically-driven pump is the hand pump. This machine transfers the energy from a lever moved up-and-down by hand to a pump rod connected to a sealed plunger housed in a pipe descending into the water source. Each upstroke of the plunger pulls water into the cylinder, while on the downstroke, a check valve in the bottom keeps the water from being pushed out, so the water is forced up the pipe with the next upstroke.
a windmill-driven pump can be used to supply water from a source to a water storage system located at a higher elevation.
Wind-Powered Mechanically-Driven Water Pump
In areas with an abundant wind resource, the rotary motion produced by a windmill can be converted into the linear up-and-down motion that drives the same plunger mechanism as the hand pump.
Using the rotational mechanical energy of the windmill to drive a mechanical pump is more efficient than converting the rotational energy of the windmill into electricity via an alternator, and then converting that electricity back into mechanical energy at a motor-driven pump.
Since the wind isn’t always blowing, water should be pumped to a storage system located at a sufficiently high elevation to supply the end-uses with their minimum required input pressure via gravity. The windmill and water storage system should be sized to account for the maximum anticipated domestic water and irrigation requirements during the maximum duration of calm winds experienced at a site. Aermotor Windmill Company, a US manufacturer of windmills, offers a variety of windmill sizes- the largest of which can can lift water up to 1170 ft at 150 gallons per hour (or higher flowrates at lower elevation differentials, up to 3300 gallons per hour at 59 ft of lift).
Hydraulic-Powered Mechanically-Driven (“Ram”) Water Pumps
Hydraulic ram pumps are another type of mechanical pump that utilize the momentum of a relatively large amount of moving water (provided from a higher-elevation source) to pump a relatively small amount of water uphill – as much as 150 feet from a pump location. They are extremely simple machines, with only two moving parts, as described in the video below.
One big disadvantage of a ram pump is that it wastes a lot of water – typically, only about 10% of the water it consumes actually makes it up the delivery pipe, with the rest flowing out of the pump. For this reason, they are typically used with streams or springs where the water is already flowing downhill and its’ potential energy can be captured and used in the ram pump.
Electrically-Driven Water Pumping
Electrically-driven pumps are the most commonly-used machine for pumping water in this era of the electrical grid. Electric motors convert electrical energy into rotational energy, which can then be used to move water in a variety of pump designs, the most common of which is a centrifugal pump. In a centrifugal pump, the mechanical energy produced by the motor turns an impeller with many curved blades, which channel the water through the pump, ultimately exiting at a higher pressure and flowrate.
Ideally, a centrifugal pump should be located at or below the static level of the water source, as it requires less energy to “push” water than to “suck” it. Centrifugal pumps can be placed above a source and “suck” the water up into the impeller, however this is limited to less than 100ft (depending upon site elevation) – and the closer the pump can be to the water source, the better. In the case of a well, especially a deep well, a better choice is to have the pump submerged into the water (a submersible pump), where its rotational energy can be used entirely to “push” the water up to higher elevations.
Since the focus of this post is on systems that can move things using locally-produced and -abundance energy sources, AC grid-powered pumps will not be discussed.
Solar PV-Powered Electrically-Driven Water Pumps
In areas with an abundant solar resource, a direct current (DC) electric motor-driven pump powered by solar photovoltaic panels can be used to pump water. Utilizing a direct current motor hardwired to the solar PV panels or battery bank eliminates the typical inefficiencies that result from inverting the direct current produced by the solar PV panels to the alternating current required for typical electrically-driven pumps. A solar PV-powered electrically-driven pump configuration supplying water from a well to a water storage system is shown below.
Since the sun isn’t always shining, there are two main ways to ensure pressurized water to the various property end-uses in a solar PV-powered pumping system: pump the water to a storage system located at a sufficiently high elevation to supply the end-uses via gravity during periods of no sun, or use electrical batteries charged by the solar array to power the pump during periods of no sun. Water storage typically has a lower environmental and financial cost than batteries, and thus is typically recommended if at all possible. The solar PV panels and water storage system should be sized to account for the maximum anticipated domestic water and irrigation usage during a typical spell of overcast days and dark nights (backup electricity during atypically long overcast/rainy spells can be provided by a generator, discussed in greater detail in the upcoming Moving Electrons post).
Transportation and Land Development
Humans have been trying to figure out how to reduce the amount they need to walk and carry their things, speed up the time it takes to get themselves or their things from one location to another, and extend the distance they can go for a long time. Horses were leveraged for transportation as early as 10,000 years ago, not long after the advent of agriculture, and donkeys, mules, camels, and others have been used since as early as 3500 B.C. The steam locomotive was developed in the early 1800s (wow- just over 200 years ago!), and vehicles based on the combustion engine came about in the late 1800s.
While assembly lines have made personal automobiles and internal combustion engine-driven machinery relatively cheap and attainable (with an estimated 273.6 million on the road in the U.S. alone in 2018), their true costs are only recently being more fully acknowledged, with rivers, oceans, and air around the globe polluted by the waste products of their manufacturing processes and international wars fought over the oil used to fuel them – among others.
Electric cars in recent years have appeared as a kind of “savior”, however they are not quite as “renewable” or “zero-emission” as advertised. The electric motors themselves are very efficient at converting electrical energy to rotational energy at the wheels – however, when accounting for all of the energy inefficiencies in getting the electricity to the motor (often from coal-fired power plants, along transmission lines to an AC/DC converter, to a battery bank manufactured with non-renewable resources using fossil fuels, to a DC/AC inverter, to a motor controller, and, finally, to the motor), the energy efficiency is near that of an internal combustion engine. Charging an electric vehicle from a nearby solar PV system removes some of these inefficiencies, but there are environmental and energetic costs to manufacturing solar PV panels as well.
While we aren’t suggesting that we should abandon the leveraging of animals or technology to help us to work, we would like to suggest that, with more thoughtful design, our need for transportation assistance can be greatly reduced – on a homestead scale, on a regional scale, and on a global scale. Solutions to the last two are beyond the scope of this post, and we will focus on the first – homestead scale transportation.
Planning for the transportation needs at a site starts at the very beginning – during the Whole Site Design phase. Taking the time to assess the needs of the site as a whole, determine the elements that will be requires to provide for those needs, thoughtfully place each in relation to each other, and design efficient access routes throughout the site can significantly reduce the distances that humans, animals, and materials need to travel onsite. Done well on a homestead and small farm scale, the need for electricity-, liquid-, and gas–fueled transportation systems to move things around a site can even be eliminated in favor of walking, hand carts, bicycles, and working animals.
When a need for additional help in moving things still exists, vehicles should be chosen that can be most easily converted to run off of locally-produced energy in the future once those production systems are in place.
Liquid and Gas Fuel-Powered Mechanically-Driven Vehicles and Equipment
We find ourselves often recommending older diesel vehicles, especially in sites with a low solar resource and high fuelwood resource, as they were built with durability in mind, are much easier to repair than gas and electric vehicles, can be fueled by biodiesel with no modification, and can be fairly easily converted to run as a dual-fuel system with alcohol made from woody debris or biogas as a secondary fuel, as shown below, which can be produced from byproducts of elements typically found on a homestead of farm.
Solar PV-Powered Electrically-Driven Vehicles and Equipment
In locations with an abundant solar resource, battery-powered electric vehicles charged by solar PV panels be the most environmentally-friendly solution. Some electrically-driven homestead- and farm-management equipment we’re come across include:
- Tractor – Solectrac is the first producer of consumer-ready electric tractors in the U.S., with two models as of this writing: their Compact Utility Tractor shown below has 3-6 hours of runtime on a single charge, compatibility with all Category 1 – 540 PTO implements, and a 1,650 lb lift capacity.
All-Terrain Utility Vehicle (UTV) – Polaris has released its Ranger EV electric side-by-side,shown below with a range of ~45 miles on a single charge, a box capacity of 500lbs and a towing capacity of 1500lb. This UTV can be fairly easily charged with a solar array of appropriate voltage output.
Other manufacturers of electric UTVs include include Nikola, Hisun, and Textron.
Refrigerant Compression
A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas and back again as it transfers heat to and from the environment. Refrigerants are typically used to provide space cooling (of refrigerators and freezers, and rooms) in residential settings.
As with water pumping and transportation, designing for systems to move refrigerant ideally starts before any structures have even been built or elements have been put in place at a site, at the very beginning – during the Site Assessment and Whole Site Design phase. Taking the time to identify the sectors (external energies like wind, sun, etc) that influence a site and its various microclimates will help ensure that a house is well-sited, -oriented, and -designed to take advantage of passive solar heating and cooling, and selecting climate-appropriate construction materials will maximize thermal buffering – both of which will provide space temperature regulation, and will surely reduce or possibly even eliminate the need for moving refrigerant to supply supplemental cooling.
When a need for moving refrigerant still exists after this design phase or at an already-developed site, refrigeration systems should be chosen that can be powered by locally-produced energy in the fewest conversion steps.
Solar PV-Powered Electrically-Driven Compression Refrigerators/Freezers
In areas with an abundant solar resource, direct current (DC) electric motor-driven compressor refrigerators, freezers, and air conditioners powered by a solar PV-charged DC battery bank are recommended to provide for refrigeration needs. This configuration eliminates the typical inefficiencies that result from inverting the DC supplied by PV panels and batteries to the alternating current required by typical air conditioner and refrigerator compressors. The battery bank and solar photovoltaic system serving the units should be sized to account for the maximum anticipated refrigeration usage during a typical spell of overcast days (backup electricity during atypically long overcast/rainy spells can be provided by a generator, discussed in greater detail later in this section).
There are several manufacturers of DC electric motor-driven compression refrigerators and freezers, including SunDanzer and NovaKool – both available from Backwoods Solar. HotSpot Energy manufactures a DC electric motor-driven compressor air conditioner.
Gas Fuel-Powered Absorption Refrigerators/Freezers
Gas-fueled refrigeration systems are typically recommended for sites with a lower solar resource. Gas-fueled refrigeration units, like propane absorption refrigerators and freezers, are durable (there are no moving parts, unlike an electric refrigerator which use a motor-driven compressor) and currently have a low fuel cost (propane is currently cheaper per unit of contained energy than solar PV and batteries, and even more so in an area without a frequent number of sunny days per year), and can be converted to operate with biogas produced on-site.
There are several manufacturers of propane absorption refrigerators and freezers, including Crystal Cold, available from Backwoods Solar.
Ventilation
Ventilation is the intentional introduction of outdoor air into a space. Ventilation is mainly used to control indoor air quality by diluting and displacing indoor pollutants; it can also be used to control indoor temperature, humidity, and air motion to benefit thermal comfort.
The intentional introduction of outdoor air is usually categorized as either natural ventilation (also known as passive ventilation) or mechanical ventilation (also known as active ventilation). As with earlier systems for moving things that we’ve discussed, we first start with thoughtful design to provide appropriate levels of natural ventilation and minimize or eliminate any requirement for supplemental mechanical ventilation.
Natural (Passive) Ventilation
Natural (passive) ventilation is the intentional passive flow of outdoor air into a building through planned openings (such as louvers, doors, windows, and earth tubes, discussed further in our Moving Heat post). Natural ventilation does not require mechanical systems to move outdoor air. Instead, it relies entirely on passive physical phenomena, such as wind pressure, or the stack effect (movement of air using temperature differential). Natural ventilation openings may be fixed, or adjustable. Adjustable openings may be controlled automatically (automated), controlled by occupants (operable), or a combination of both.
Solar Chimney
A solar chimney is a type of natural (passive) exhaust system that can be used, when coupled with an intake, to maintain a consistent introduction of fresh air into a structure. In its simplest form, the solar chimney consists of a black-painted chimney. During the day, solar energy heats the chimney and the air within it, creating an updraft of air in the chimney. The exhaust of air out of the chimney will create negative pressure in the structure, and thus a suction of fresh intake air at any other openings. The intake openings can be thoughtfully situated and designed to provide cooled intake air when desired (by placing operable windows or vent openings on the north-facing shady side of the structure, or using earth tubes), or warmed intake air when desired (by placing operable windows or vent openings on the south-facing sunny side of the structure).
The integration of an earth tube system with a solar chimney to provide cooling for a structure is illustrated below.
Mechanical Ventilation
Mechanical (active) ventilation is the intentional fan-driven flow of outdoor air into a building. Mechanical ventilation systems may include supply fans (which push outdoor air into a building), exhaust fans (which draw air out of a building), or a combination of both. Mechanical ventilation is often provided by equipment that is also used to heat and cool a space.
Solar PV-Powered Electric Motor-Driven Exhaust Fans
Small DC electric motor-driven fans installed in-line with solar chimneys (or roof vents) and hardwired to a solar PV panel are recommended to provide supplemental ventilation when required. These fans can be turned on using a simple wall switch if a higher air exchange rate than the solar chimney provides is ever desired.
That’s a wrap on our overview of some of the appropriate technology that can be used to Moving Things 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 3: Moving Electricity!
And if you would like help designing for the energy needs of your site, please reach out to us!
