Power to the People
Whether for heat or electricity, we all need power, but we don’t have to rely on the grid to get it.
By Carol Ekarius
Courtesy Helix Wind Corp.
Wind turbines use kinetic energy to create electricity.
Flip a switch: The lights come on. Turn a handle: Water flows from a faucet. Chilly? Crank up the thermostat. No milk in the fridge? Hop in the car and run to the store.
This is life in modern America. It’s convenient, but most of us recognize there are issues with our energy system. If you’re among the many people who would like to do something to reduce your electric bill, your carbon footprint and your dependence on foreign oil, you have many options for generating alternative power at home in the city, the suburbs and the exurbs.
Odds are you’re among the 99 percent of Americans who are connected to the grid—a web of more than 300,000 miles of transmission lines, charged by 9,200 electric-generating units, delivering more than 1 million megawatts of generating capacity to homes across America. In fact, 40 percent of our national energy flows through these wires and is delivered to our homes and businesses as electricity.
The bad news is in 2008, only about 9 percent of electricity we consumed came from renewable sources, according to the Energy Information Administration. But there’s good news: That number is growing. According to the United Nations, in spite of the global recession, 2008 was a banner year for investments in renewable energy.
There are essentially two types of systems for renewable electricity: on grid and off grid.
For a grid-tied electricity consumer, you can join a movement to become less dependent on fossil energy and nuclear power incrementally, still getting some of your electricity from the grid when necessary. Grid-tied consumers produce power, reducing the electric coming from the power plant. If you produce more than you’re using, the electricity will feed back into the grid, spinning your meter backward (called net metering).
In all states, utility providers purchase the excess energy if you make more than you use, but in only a handful of states are the utility companies required to buy electricity from you at the same rate at which they sell it to you (called equality). Some utilities stifle consumers who want to tie in and take advantage of net metering; however, the attitude among utilities has improved dramatically in the last few years.
Off-the-grid generation systems supply 100 percent of the energy required for the household and have battery-backup systems to provide electricity needed at night or when the wind isn’t blowing. Owners can’t grow these systems over time. Instead, they must fully invest up front if they want to enjoy modern conveniences.
Off-the-grid consumers typically opt for gas or wood heat rather than electric and tend to use gas refrigerator-freezers, water heaters and stoves, as these are some of the biggest energy-sucking appliances. Batteries for these systems may require maintenance and generally need to be replaced every five to seven years.
Photovoltaic (PV) cells take advantage of something that scientists refer to as photoelectric effect, a phenomenon that causes them to absorb photons of light and release electrons that are captured as an electric current, thus creating electricity. Generally made of silicon, PV cells are attractive, require little maintenance and make no noise. Plus, they’re about the most environmentally friendly source of electricity there is.
Each cell is fairly small (about 4 square inches), but they can be combined into panels (also known as modules). The panels are sized to supply electricity at certain voltages: Six-, 12-, and 24-volt systems are most common. Panels can be wired together in an array (or group of panels). PV cells produce their maximum energy output (or amps) when the sun is hitting them directly; there’s less output when the sun is diffused by clouds or hitting the panel at an angle.
The potential for solar production varies dramatically around the country depending on the strength of the sun and the number of sunny days. To maximize the capture of energy, arrays are typically mounted on frames that can either be moved manually several times per year to follow the sun’s solar angle (low in the sky during winter, high in the sky during summer) or on a device that automatically tracks the best angle of the sun.
The energy output from the panels is direct current (DC) energy, similar to the energy from a battery. Because household electrical systems run on alternating current (AC) energy, tying a solar system into your household requires an inverter that converts the DC energy to AC energy.
Don’t call the devices that blow in the wind to create energy “windmills”! They’re wind turbines or wind generators.
With wind systems, we take advantage of kinetic energy (the energy of motion), to create an electrical charge. If you studied physics, you may remember learning that the kinetic energy of an object is proportional to the square of its speed. (In the case of a wind turbine, think rotations per second multiplied by rotations per second.) The windier an area, the faster the turbine spins and the more energy it produces. As with the other forms of renewable energy, the energy from the turbine is DC energy, so a turbine also requires an inverter.
Turbines have a built-in generator, which is similar to the alternator in your car that charges your car’s battery as you drive. Most turbines have a “cut-in speed,” where the turbine is spinning fast enough to start outputting energy, and a “cut-out speed,” where it disengages to protect it from blowing itself apart. Depending on the turbine, the cut-in speed equates to wind speeds of 3 to 10 mph, and cut-out speeds are 45 to 80 mph.
Although some newer wind turbines are quieter than their predecessors, the noise can be a dis-advantage in residential applications. Also, the turbine has to be set above all structures and trees to take best advantage of the wind, meaning they sit on a fairly high tower. This can be a disadvantage in core urban and densely populated suburban areas, but they do work in large-lot suburban areas or in the exurbs. Wind turbines are going through a period of exciting research and development, so look for turbines in the near future that will work in urban areas, such as new designs that don’t require as much clearance from structures and trees.
Although microhydro systems, which use the kinetic energy of moving water, have more limitations with respect to where they’ll work, they might be an option if you happen to have a small but steep stream running through your property. Hydropower is the product of head (or the vertical distance the water falls) times the flow of water.
On a microhydro system, a portion of water is diverted from the stream at the top of your property via a pipe (called a penstock) and moved down slope to the turbine. As long as it’s being fed water, the turbine spins continuously, creating DC current from the electrical generator to which it’s connected. As with the other renewables, it can be directed to batteries or into an inverter to connect to your household power.
This is another area where many new products are in development. One of the more clever options being researched hooks a turbine into the water line coming from your city water system or well. Every time you run the water, it spins the turbine and produces electricity. This system is not ready for residential use, but more research could make this an attractive option in the future.
Space heating and water heating account for about 60 percent of Americans’ home energy consumption. Natural gas and heating oil (fuel oil) are the most commonly used fossil fuels for heating, but there are also several renewable options.
PV panels are rarely used to produce heat because electricity is not the most efficient way to create heat, but you can heat space and water using the sun. In the case of heat systems, there are two types: passive and active. These systems can also be combined. Passive solar, which includes clever use of building placement, building materials, glazing (windows) and shade structures, is economical, but it requires planning prior to a building’s construction. Active systems include either hot-air or hot-liquid solar-collection panels that are attached to the roof or set up as a freestanding unit.
Liquid-based systems heat water or an antifreeze solution, while air systems heat the air within an air collector. Both approaches use pumps and fans to transfer and distribute the heat collected in the panels. They also generally have a storage system to capture and feed back heat when the sun isn’t shining.
Geothermal (or ground source) heat pumps are mechanical systems composed of heat pumps and piping systems that can be used for heating and cooling air as well as heating water.
According to the EPA, these systems can reduce energy consumption and corresponding greenhouse gas emissions by as much as 72 percent compared to conventional electrical heating and cooling systems. They help control humidity, maintaining indoor air at about 50 percent relative humidity, which makes them especially advantageous for humid climates. They can be built into new construction or retrofitted into existing homes. The systems are absolutely quiet, maintain almost constant temperatures (no blast of hot or cold air often associated with other systems), and require almost no maintenance, with component lives that run from 20 to 50 years.
Geothermal heating and cooling relies on the fact that the ground—just 10 feet or so beneath the surface—remains at a relatively constant temperature throughout the year. The system pulls in heat stored in the Earth during the winter, and moves heat out of the building during the summer, sending it back into the ground.
The series of pipes (called a loop) is buried, either vertically or horizontally, in the ground near your house. The pump moves liquid (usually water or antifreeze) through the loop, which absorbs or dissipates heat. The loop is brought into contact with the house’s duct system where, by natural exchange, air is either warmed or cooled.
With all that’s happening in the alternative energy world, it’s a great time to reconsider how your power is made.
About the Author: Carol Ekarius is a writer and veteran off-the-gridder living in Colorado.
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