Well-illustrated, and highly accessible, The Homeowner’s Guide to Renewable Energy by Dan Chiras (New Society Publishers 2011) is an essential resource for anyone wanting to enter the renewable energy field, whether their goal is a lower monthly utility bill or complete energy independence.
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What Is Renewable Energy?
Contrary to what many people think, renewable energy is not a source of energy we’ve just discovered. Humans have relied on renewable energy since the very first human-like creatures roamed the planet over three million years ago. Throughout most of human history, the energy human beings needed to survive and prosper has come from food molecules — primarily seeds, berries and roots. The energy in these foods provided the means by which we built early civilizations. Our early ancestors also burned wood to warm their caves and cook their food. But just what is renewable energy?
Plants, of course, are renewable resources, capable of regenerating themselves from seeds, roots or tubers. But plants are here by the grace of three other renewable environmental resources: soil, water and air.
Although our predecessors, and virtually all other life forms on the planet, received the energy they needed to survive from plant matter, the source of the energy extracted from our botanical companions is not the soil or water or even the air. The source is the sun — a massive hydrogen fusion reactor 93 million miles from planet Earth.
Plants capture the sun’s energy during photosynthesis. In this complex set of chemical reactions, plants synthesize a wide variety of food molecules from three basic “ingredients”: carbon dioxide from the air, water from the soil and solar energy from the sun. Solar energy that drives photosynthetic reactions is captured and stored in the chemical bonds of organic food molecules. When food molecules are consumed by us, or any other animal for that matter, stored solar energy is released. Solar energy contained in food molecules and liberated by the cells of our bodies is, in turn, used to transport molecules across cell membranes and to manufacture protein and DNA to power our muscles and heat our bodies.
Humankind’s greatest achievements were made by using the sun’s energy. The Egyptians, for instance, hauled massive stones to build the towering pyramids with nothing but ingenuity and the muscle power of conscripted laborers fueled by organic food molecules courtesy of the sun and plants. The Romans expanded their holdings to build a vast and prosperous empire, too, all with horse and human muscle powered by plant matter and, ultimately, sunlight.
For most of human history, then, renewable energy reigned supreme.
Then came the fossil fuel era. Lumbering to a start in the 1700s in Europe and the 1800s in North America, the fossil fuel era was first powered by coal, an organic sedimentary rock. Coal owes its origin to plants that grew in the Carboniferous era some 250 to 350 million years ago. Coal replaced waning supplies of wood in Europe and fed the industrial machinery that made mass production — and modern society — possible. So, in a way, the Industrial Revolution was also powered by solar energy — ancient sunlight that was captured by plants millions of years ago.
For many years, coal reigned supreme. But eventually coal was forced to share its kingdom with two additional fossil fuels: oil and natural gas. Also produced from once-living organisms (notably, aquatic algae), these fuels were relatively easy to transport and, like coal, are found in highly concentrated deposits. Over time, oil and natural gas, along with coal, became major components of the world’s energy economy.
In 2009 (the latest year for which data were available), oil supplied 37 percent of the United States’ total annual energy demand. Natural gas provided about 25 percent, and coal supplied 21 percent of our energy needs. Nuclear energy provided just under 9 percent. The remaining 8 percent of the United States’ energy diet was supplied by four renewable resources: hydropower, solar, wind and geothermal. Canada is similarly heavily dependent on oil, natural gas and coal. In 2008, oil, natural gas and coal provided 66 percent of Canada’s energy. Nuclear energy provided about 7 percent, and hydropower provided 25 percent of the nation’s energy.
In the more developed countries, fossil fuels clearly dominate the energy scene today, but their glory days are coming to an end. Oil and natural gas are entering their sunset years, making the shift to clean, affordable, reliable and abundant renewable energy inevitable. Fortunately, we have lots of options.
Making Wise Energy Choices
To make the wisest choices as individuals — and as a society — we need to understand our predicament — what energy resources are endangered. Many energy experts believe that global oil production will peak or already has peaked. Peak oil could result in a devastating rise in prices. Global natural gas production may also peak soon, creating further turmoil. Clearly, we need replacements for these two fossil fuels. But what about coal?
Given the devastating impact and high cost of global warming and a host of other energy-related environmental problems, coal will very likely need to be phased out in the near future. Although coal is abundant in North America, China and elsewhere, and its use is bound to increase dramatically as oil and natural gas production peak, coal is the dirtiest of all fossil fuels. Coal combustion not only produces sulfur oxides and nitrogen oxides that react with water and sunlight to form sulfuric and nitric acids that poison rain and snow, coal combustion also generates millions of tons of particulates that cause asthma and other respiratory diseases. Coal combustion also yields millions of tons of ash containing an assortment of potentially toxic materials such as mercury. Much of this ash is disposed of in ordinary landfills alongside our trash, and the toxic chemicals in the ash can eventually seep into groundwater. Perhaps most important to our future, however, is that coal combustion produces enormous quantities of the greenhouse gas carbon dioxide — far more carbon dioxide per unit of energy produced than any other fossil fuel in use today.
Despite industry’s frequent mention of an elusive “clean coal technology,” it’s difficult to make coal clean. Without question, the efficiency of coal combustion can be increased to reduce the amount of pollution per unit of energy produced, and I applaud any efforts to do so. But capturing carbon dioxide and storing it underground — one way to make coal cleaner — is energy intensive and will dramatically increase coal combustion itself. (Carbon capture increases the energy consumption at a power plant by around 25 to 30 percent.) Even with the best technologies in place, coal combustion will produce lots of pollution; it is inevitable, and the more coal we consume, the greater the output of potentially harmful gases and particulates and solid waste. Carbon dioxide, for example, is the unavoidable by-product of combustion of any carbon fuel. Much of the sulfur that contaminates coal in varying degrees can be removed before or after combustion by pollution control devices. The sulfur, however, does not magically disappear. Most of what is removed by smokestack scrubbers ends up in a toxic slurry that is disposed of in landfills where the toxic components can leach into groundwater. It’s a simple mass balance phenomenon: if the chemical ingredients of the pollutants are in the fuel, they’re going to be a by-product one way or another. They won’t mysteriously vanish because a coal executive tells you they do. In the end, “clean coal” seems like nothing more than just a deceptive marketing ploy of the coal companies to make a dirty fuel appear more environmentally acceptable.
To make the wisest choices, we also need to understand the end uses of each of the fuels we are trying to replace. Remember, it is the products and services these resources provide that we want, not the fuels themselves. As natural gas supplies decline, we don’t necessarily need more natural gas. We need to ensure the services that natural gas currently provides. For example, many homeowners use natural gas to provide space heat; to heat water for showers, dishwashing and laundry; and to cook food. Finding replacements for natural gas means finding ways to provide these services via clean renewable resources and technologies — for example, solar hot air systems to heat our homes and solar water systems to provide space heat and heat water for domestic use.
This book lays out the options available to us that can ensure the continuation of services currently supplied by now-failing or environmentally unacceptable fuel sources. Don’t forget, though, that the easiest way to meet our needs is often achieved by simply being more efficient. A warm home or business, for instance, can be achieved by sealing up those obnoxious cracks around windows, doors and elsewhere. It can also be ensured by installing additional insulation to the ceilings and walls of our homes and offices. Additional space heat can be provided by retrofitting our homes for passive solar — adding windows on the south sides of our homes to let in the low-angled winter sun. Space heat can also be achieved by installing active solar hot water system. Solar hot water systems generate hot water that can be integrated with heating systems already in many of our homes — from baseboard hot water systems to radiant-floor systems to forced-air systems. There are many other options out there. For example, homes can be heated via heat pumps, devices that remove heat from the ground or even the air and transfer it to the interior of a building.
To make wise choices, you also need to know which options make the most sense. How do we assess the appropriateness of a renewable energy option?
Two of the most important criteria are cost and net energy yield, which often go hand in hand. Consider an example: To replace declining supplies of oil, many fossil fuel advocates suggest that we can turn to oil shale and tar sands. Unfortunately, a huge amount of energy is required to extract the oil from these natural resources. The energy required to extract oil from tar sands and oil shales subtracted from the energy of the final product is known as the net energy yield. It can be thought of as the energy returned on energy invested. Both oil shale and tar sand oil production have very low net energy yields compared to conventional oil (although new processes have steadily improved the net energy yield of tar sand production). The lower the net energy yield, the more costly the fuel. As the price of conventional oil increases, the cost of oil shale and tar sand oil will inevitably rise.
Environmental impact should also be a key criterion when selecting an alternative fuel. To build a sustainable future, we must develop fuels that meet our needs for energy without sacrificing an equally important, though often overlooked, requirement: our need for a clean, healthful environment.
Resource supplies are also vital. From the long-term perspective, it makes sense to pursue those resources that are most abundant. And what could be more abundant than a renewable fuel supply?
In sum, when seeking alternatives to waning supplies of fossil fuels, we must proceed with caution and intelligence. We need to develop energy resources that meet our needs and have the highest net energy yield, the most abundant supplies and the lowest overall cost — socially, economically and environmentally. In this book, I present up-to-date information on net energy yields to help you sort through the list of options. I’ll also look at the pros and cons of various technologies, to help you make the wisest choices.
More from The Homeowner’s Guide to Renewable Energy
• How to Size Solar Hot Water Systems
• What Is Passive Cooling and What Can You Do to Make It Work for You?
• Using Attached Sunspaces in Passive Solar Design
This excerpt has been reprinted with permission from The Homeowner’s Guide to Renewable Energy: Achieving Energy Independence Through Solar, Wind, Biomass and Hydropower by Dan Chiras, published by New Society Publishers, 2011.
