Mother Earth News: Alternative Energy Discussion

11/01/2005

Mother Earth News: Alternative Energy Discussion
October 2005

WHAT IS ALTERNATIVE ENERGY?

To move us away from dependence upon non-renewable oil, gas and coal, and high-risk nuclear power, alternative energy systems utilize renewable resources for electricity, heating, cooling and transportation. Alternative energy also encompasses efforts to use nonrenewable natural resources in more sustainable, environmentally benign ways.

WHY SHOULD WE SWITCH TO ALTERNATIVE SOURCES OF ENERGY?

Emerging Technology

The more we rely on renewable energy, the less dependent we are on the fragile electric power grid and nonrenewable, polluting fossil fuels. With world oil and gas supplies dwindling, experts estimate that the costs of gas, electricity and other conventional energy sources will increase significantly in the coming years. Some fear rising energy costs will severely disrupt the world economy.

There are many ways to create and use energy efficiently and sustainably, and the technology to do so is becoming more available and affordable than ever. In 2004, for example, shares of the world’s 24 publicly traded solar companies soared nearly 185 percent. Experts predict the solar photovoltaics (PV) market will grow from $7 billion to $30 billion by 2010. Even some national home improvement stores are beginning to sell alternative energy systems for home use.

Financial Incentives and Rebates

Buying a renewable energy system is more affordable than ever thanks to rebates, tax breaks (personal tax credits and property tax exemptions) and low-interest loans from state governments, local utilities and even private companies. Depending on where you live, renewable energy subsidies can reduce the cost of a wind- or solar-powered system by more than half of the total expense. In Rhode Island, for example, residents can receive a rebate for up to 50 percent of the cost of a photovoltaic (PV) system. In other states, such as New Jersey, rebates of up to 70 percent of system costs are available. California and Illinois will reimburse up to 60 percent of your wind or solar system costs.

As natural gas and oil prices rise and electric grid problems mount, an increasing number of cities and states are setting ambitious targets for boosting renewable energy production. New programs continue to pop up across the nation — visit http://www.dsireusa.org (the Database of State Incentives for Renewable Energy) to learn more about what’s available in your area.

WHAT ARE THE DIFFERENT SOURCES OF ALTERNATIVE ENERGY?

Some of the ways we can tap alternative, renewable sources of energy include our efforts to generate power, heat and cool our homes, heat our water, cook our food, and get around.

The technology to generate electric power from sources other than coal and petroleum is rapidly advancing. A few of these methods are wind energy; micro-hydroelectric power; and active solar power, including crystalline and thin-film photovoltaics (PV). These alternative system can be installed “off the grid” or connected to the utility company ("grid-tied").

Sustainable means of heating and cooling homes include passive solar power systems (with attention to site orientation, south-facing windows, thermal mass and landscaping); geothermal heat pumps (both air-source and ground-source); biodiesel for home heat; heating water with solar collectors; and traditional wood heating.

Alternative transportation has become an important issue now that the price of oil has surged to over $50 a barrel. The technology to build gas-electric hybrid automobiles that are both more energy-efficient and less dependent on gasoline is quickly becoming mainstream, and the incentives to purchase these cars include federal tax breaks and a substantial payback in savings at the gas pump.

ALTERNATIVE ENERGY: ELECTRICITY GENERATION PHOTOVOLTAIC SOLAR POWER
[Adapted from Simpler Solar Power by Doug Livingston, June/July 2005]

Photovoltaic (PV) ‘solar power” is one of the most widely available alternative energy options. Special panels can be placed on roofs or in free-standing arrays, where they generate electricity whenever the sun shines on them. PV modules (the panels that convert the sun’s energy into electricity) come in two types: crystalline and amorphous (also called “thin-film”). Both cost about the same for quality modules ($8 to $12 per installed watt), but they differ in the way they look and work. In many states, PV systems can be connected to the grid and whenever the system produces more power than is being used, the electric meter spins backwards and the customer gets paid for the extra power that is produced.

Crystalline PV modules

Crystalline PV modules come in two types: mono and poly. Monocrystalline PV has blue or gray-black cells that don’t completely cover the module face. A white backing usually shows at each cell’s rounded corner. Polycrystalline cells are cut into rectangles that completely cover the white background, providing a uniform appearance. They usually are a sparkly blue color. Both mono and polycrystalline modules are covered with tempered glass in an aluminum frame. Mono and polycrystalline PV perform similarly—your choice likely will be decided on availability, price and personal aesthetics.

Amorphous ("thin-film") PV modules

Amorphous PV has not been on the market as long as crystalline PV, and the first generation or two did not prove to be durable. Even now, most amorphous modules only carry a five-year warranty, although United Solar Systems’ UniSolar amorphous PV carries at least a 20-year warranty and has maintained good performance after decades of operation. UniSolar’s standing-seam thin-film laminates can be bonded directly onto a metal roof, creating a durable, uniformly dark surface that also is pleasing to the eye. Usually, the thin-film PV can be connected invisibly to its wiring under the roof’s ridge cap.

Amorphous PV requires more space per generated watt than crystalline PV, but it has two significant advantages: High temperatures and partial shading do not affect amorphous PV as much as crystalline. All PV modules produce less electricity the hotter they become, but the output reduction for amorphous PV is about half as much as it is for crystalline PV. As PV production increases, the price of amorphous should decrease to less than crystalline modules.

On-grid Solar Power Systems

You don’t need to unplug from the utility grid in order to use solar panels to produce your own power. Grid-tied solar systems are connected to the utility grid, and you can use the grid to “store” your excess solar power. In most states, net metering laws require your utility to credit you whenever your system produces more power than you can use. This means that when the sun is shining, your electric meter may spin backwards! On-grid solar systems provide the simplest way to switch to renewable energy for your home.

Off-grid Solar Power Systems

Grid-independent solar systems can help you achieve true energy independence. They are a great option for homebuilders facing the cost of running power lines to a new property. Banks of batteries store your excess power, and the power remains there until you need to use it.

ELECTRICITY GENERATION: WIND POWER

[Adapted from Get Wind Power! By John Ivanko & Lisa Kivirist, Summer 2005; Harvest the Wind by Michael Hackleman & Claire Anderson, June/July 2002]

Wind Power: An Introduction

Another means of becoming energy independent is through the use of wind-generated power. In many parts of the continent, you can tap the power of the wind to generate nonpolluting renewable electricity for your home. Wind plant designs have improved so much—and the costs of oil, natural gas and nuclear power are so high—that many power companies are building large-scale wind plants. Farmers are being paid as much as $2,000 a year to lease one-eighth-acre sites for 200-foot-tall commercial wind plants. Experts predict wind-electric generation will soon become a major energy source in the United States.

The idea of relying on the wind as an energy source may seem risky, since wind seems to be variable from day to day. But wind actually acts in fairly predictable ways. Analysis of more than a half-century’s recorded data, from thousands of sites, shows distinct patterns in both wind direction and speed through the seasons. The windiest months occur in winter, while the calmest winds are during summer. This means a marriage of wind (peaks in winter) and solar power (peaks in summer) can often provide the best power partnership. Even if you’re not located within the breezeways of the plains or the windy valleys of California, you still may be able to produce some of your power from wind. While your region of the country may not be ranked as ideally suited for wind power, your individual microclimate paired with energy winds (storm winds and gusts) might yield enough energy to justify a wind plant system.

Wind Power: Components

The turbine, or generator, is the electricity generator that is attached to the top of the tower.

The rotor is the set of rotating aerodynamic blades. The load on the airfoil-shaped blades is captured by the attached generator. The amount of “swept area” is determined by the rotor diameter; generally, the greater the diameter, the more power is generated. Two-or three-blade rotors are most common. Three-blade rotors, while less efficient, spin more smoothly, extending the life of the equipment and allowing the turbine to start at lower wind speeds.

The tail is the component that tracks the wind’s direction.

The governor is the mechanism that limits the amount of electricity produced, protects the equipment from overproducing and burning up in high winds, and limits the centrifugal force.

The tower is the post upon which the turbine is mounted. It’s made from high-strength materials with three common styles: free-standing, guyed lattice and tilt-up. Towers help the generator avoid ground wind drag (the friction between the earth and moving air masses) and turbulence caused by obstacles on the Earth’s surface.

Wind Power: Installation

There are several keys to successful wind energy production. First, the site must have consistent wind at an average speed of 8 to 12 mph or higher. A site assessment should be completed using national windspeed data collected by the U.S. Department of Energy or other appropriate sources. The site also should be large enough to allow a turbine to be placed on a tower with its rotor at least 30 feet higher than anything within 500 feet of the tower. Typically, a half acre of land will suffice for the tower and equipment. The Federal Aviation Administration does not allow towers higher than 200 feet to be erected without fulfilling expensive additional requirements. Zoning regulations or proximity to airports may require additional modifications.

Besides the wind itself, several variables determine how much energy can be generated, each having a trade-off in the cost and complexity (and maintenance) of the system. In general, the larger the rotor diameter, the greater the wind-swept area and the greater the energy generated.

Additionally, the higher the tower, the faster and more regular the wind—thus more energy is generated. It’s usually cheaper to install a higher tower than to install a larger wind generator.

Additional information on residential wind turbines is available from Wisconsin Focus on Energy (http://www.focusonenergy.com), the Midwest Renewable Energy Association (http://www.the-mrea.org) and the American Wind Energy Association (http://www.awea.org).

Wind Power: Is it for You?

A small wind-energy system can provide you with a practical and economic source of electricity, if:

- Your property has a good wind resource; - Your home or business is located on at least one acre of land, or your property is in a remote location that does not have easy access to utility lines; - Your local zoning codes or covenants allow wind turbinesl - Your average monthly electric bills are $150 or more; - You are comfortable with long-term investments.

POWER GENERATION: HOME-SCALE HYDROELECTRIC POWER [Adapted from Homestead Hydropower by Steve Maxwell, February/March 2005]

Home-scale hydroelectric Power: An Introduction

Home-scale hydroelectric power systems offer an opportunity for humans to forge an intelligent and sustainable partnership with sunshine, rain and running water. Sometimes dubbed “microhydro,” this approach uses low-impact mechanical systems to harness moving water to generate clean, reliable electric power. Unlike the intermittent power from wind or solar systems, hydroelectric power can flow night and day from year-round streams.

A hydroelectric system converts the force from flowing water into electricity. You take the kinetic energy of water flowing downhill from a stream or river and direct it onto a wheel in a turbine that converts the rotational energy to electricity. The amount of power produced depends on the volume of water flowing onto the turbine and the vertical distance it falls through the system. Equipment costs range from about $1,000 for the smallest, to $20,000 for a system large enough to power several modern homes. Many microhydro systems generate 75 to 350 kilowatt hours (kWh) per month.

Microhydro: The Basics

To implement a successful microhydro system, you will need the following basic requirements:

- At least 2 gallons per minute of flowing water, and a lot of drop; or 2 feet of drop and 500 gallons per minute of water flow. - A proper turbine, alternator and shelter from bad weather. - Permission from the relevant authorities, even if the project is entirely on your own land. - A water intake and enough pipeline or “penstock” to divert water to the turbine and return it to the stream. - A transmission line to move the power from the alternator to the point of use. - Batteries and a power inverter subsystem to convert the electricity to an alternating current (AC), and a controller for the electrical system.

Microhydro: Site Assessment

If you’re lucky enough to have an abundance of flowing water, you may be tempted to envision projects that are larger than what is normally required. You should plan to produce only the power you need, not the maximum amount possible. If you don’t have an obvious microhydro location — but you still have access to running water — you still may be able to set up a system.

In its simplest form, the energy potential of flowing water depends on its flow rate (usually measured in gallons per minute) multiplied by the pressure behind that flow (related to the overall distance of water drop, called “head” in the business). Accurate site assessment is key because it identifies the total energy potential that’s available, and it all begins with a measurement of water-volume flow rates.

One of the ways to find the total amount of available water is to use the “container method.” Find a spot where the potential stream’s water enters a culvert and time how long it takes to fill up a container of a known size. The stream’s flow in gallons per minute equals the size of the container in gallons divided by the time it takes to fill in seconds, times 60. For example, if a 5-gallon bucket fills up in 10 seconds, the stream flows at 30 gallons per minute (gpm).

Next, you need information on the pressure behind that flow, which relates to the amount of vertical drop the water undergoes as it travels through your site. Pressure measurement combines with flow rate to determine the raw energy potential of a location. In turn, this defines the universe of choices for the hardware necessary to produce the electricity you need at wall sockets, light fixtures and appliances. Flow rate multiplied by pressure equals power.

You won’t get very far in the microhydro adventure before you realize something important: There’s more to a good system than just flowing water. You also are dealing with terrestrial conditions, and that’s why creating a stream profile is essential and should be the third factor to consider when choosing your optimum site.

What you’re aiming for is an accurate representation of the water flow over natural landforms, and how those characteristics can be used to good advantage in your plans. By using a surveyor’s transit, a water level or a laser level, you can produce a side-view profile — or cross-section — of the entire stream landscape as water runs from pipeline intake to output port.

A stream profile also helps you determine the best location for the water-intake end of the pipe. This is where most of your regular maintenance will happen (cleaning out brush and stream debris, for instance), so you need to choose a spot with easy access, if possible. Also, if the flow rate of your stream is more than a few gallons per minute, you may find several possible locations for the turbine itself. The stream profile often makes it easier to identify optimal turbine placement, which usually consists of a stable water level, accessibility and water relatively free from debris. Another important consideration is to place the turbine in an area where it won’t be affected by freezing water.

Most microhydro installations include a pipeline that diverts water over land down from an area of high elevation, connecting to an enclosed water wheel (that’s the turbine) at some lower level. This situation raises key questions: Will a 2-inch-diameter pipe give you the best energy potential in relation to the cost of the material and its flow rate? How does this compare with a 4-inch pipe? Will your energy expectations be met with a 500-foot pipeline, or do you need a 1,000-foot pipe to get more head (water pressure)? How will flow volume, vertical drop and friction in the pipe affect the amount of power generated? All these questions are important because they each can have a tremendous effect on power output.

Microhydro: The Hardware

Most people who choose hydropower are attracted to the fascinating variety of unusual hardware that makes clean, low-cost electricity.

Turbines complete the first part of the energy-conversion process, and in many ways, they’re the heart of any hydropower system. Many designs are available, but most include some kind of fanlike wheel on a shaft - set within a metal case - that contains and directs water flow to spin the blades. Turbines are designed for both low- and high-pressure applications.

High-head impulse turbines are the most versatile—used for situations with heads ranging from 6 to 600 feet—and can generate enough power to sustain most any requirement given the right conditions.

Low-head turbines are meant for heads under 10 or 12 feet. These turbines are ideal candidates to charge batteries a long way from the powerhouse at low expense.

Constructing your own microhydro system also can be a viable option. Many different methods can be good alternatives to purchasing commercially produced turbines and alternators, but the efficiency and effectiveness of a homemade system depends much on its design. A centrifugal pump can be made into a backward-running Francis turbine (in which water flows through the turbine runner); an induction motor can be used as an alternator; and a crossflow turbine can be fabricated with readily available materials. Go to http://www.otherpower.com for ideas on how to make homemade systems.

The electrical side of any hydropower facility always includes a device to convert the mechanical energy of a spinning shaft into electrical energy (either a generator for direct current or an alternator for alternating current). That electrical energy is then sent through a series of components called the “balance of system” equipment, which saves and regulates the electricity once it’s generated. But before you tackle the electrical side of hydropower, you need to understand something about the two basic types of electricity: direct current (DC) and alternating current (AC).

DC is the sort of electricity delivered by a battery. Imagine a whole bunch of electrons piled up against one pole of a battery, desperately trying to get to the other pole. When you close the circuit across both poles, energy flows in one direction and can spin a motor or light a bulb in the process. DC electricity is more complicated to generate than AC, and it travels less efficiently. That said, you can store DC power in a battery, and that makes it more useful for small hydropower applications that need to build up a stockpile of energy to meet large intermittent loads.

Smaller hydropower systems might include a series of deep-cycle batteries for storing DC energy for intermittent high demand, though having a DC foundation to your system doesn’t necessarily rule out the option of AC output, as well. The secret is something called an inverter, that coverts DC to AC power. If your energy needs are medium to high, you should consider a microhydro system that generates AC power with an alternator right from the start.

Microhydro is a clean, sustainable source of power for homesteads in the right location. By considering some of the preceeding requirements, you’ll know if it can be a possibility for you.

ALTERNATIVE ENERGY: HEATING AND COOLING

HEATING AND COOLING: PASSIVE SOLAR POWER

[Adapted from Build a Solar Home and Let the Sunshine In by Dan Chiras, August/September 2002]

Passive Solar Power: An Introduction

Including simple, passive-solar features in new homes can cost next to nothing up front and save you unbelievable amounts over the long-term in reduced energy bills. Millions of homes easily could be designed to capture free heat directly from the sun. But instead we are burning - wasting - huge amounts of oil and natural gas every winter. The missed opportunities to tap into solar energy are so fantastic they boggle the mind, and nowhere is our blindness to the potential of solar more troublesome than in the home-heating arena.

You can incorporate passive-solar heating in any style home, or you can add solar features when remodeling an existing home, as long as the south side of the house receives full sun most of the day. When correctly designed, solar homes provide unrivaled comfort in winter and summer. They offer large, south-facing windows, generous views, sunny interiors and open floor plans.

Passive Solar Energy: How it Works

Heating homes with sunlight, known as passive-solar heating, is based on the simple idea of using south-facing windows to admit low-angled winter sun. Sunlight streaming into the home warms the interior space. Thermal mass, such as tile floors and interior masonry walls, stores the sun’s heat and releases it when room temperatures fall at night or during cloudy weather. Choose a house design that accommodates the right amounts of south-facing glass and thermal mass. Add careful caulking and ample insulation (usually slightly higher than building codes currently require), and you’ll have a solar-heated home that requires little or no heat from any nonrenewable fuel source. In the summer, a solar home’s thermal mass and insulation, together with properly sized overhangs to shade the windows, keep the home comfortable and reduce cooling requirements.

Simply orienting a conventional house to the south will cut annual energy bills by at least 10 percent, saving thousands of dollars over a home’s lifetime. Add a long south-facing wall of windows and some thermal mass and you easily can tap sunshine’s free energy to meet 50 percent to 70 percent of a home’s heating requirements. Do your homework or hire a solar architect to create a rigorous passive-solar design and you can reduce your energy bills by 80 percent to 100 percent. Given the probability energy costs will increase steadily in the coming years, the long-term savings from a passive-solar home could become very substantial.

Passive Solar Energy: Design Basics

Here are the basic principles to follow in designing a new or remodeled passive-solar home:

Choose a site that receives south sun during winter. Obstructions to the south of the site, such as tall evergreen trees, buildings or hillsides, need to be kept at least 1.7 times their height away from the home. When in doubt, visit the site around December 21, when the sun is the lowest in the sky. The site should receive full sun from 9 a.m. to 3 p.m. If you’re choosing to build on a small lot, select one that is deep from north to south, to ensure good solar access. Locating the house’s septic drainage field within the solar access zone is another strategy for maintaining good solar access, since that area will need to be kept clear of trees and shrubs, which would otherwise block the southern sun. Choose a home design with few projections below the roofline and no porches on the south. Projections shade adjacent windows; porches on the south prevent the sun from entering. Porches on the east and west can be beneficial by shading windows from the hot summer sun. Orient the longest wall of the house so it faces true south. Rectangular floor plans minimize the exposure of east and west walls to summer sun, which is especially helpful in hot climates. The front, back, or side of the house can be the south wall. (True south is not the same as the magnetic south shown by compasses. Check with a local surveyor’s office to find out how many degrees to adjust from magnetic south.) Can you deviate from a due south orientation? Sure, but you’ll pay a price in dollars and thermal comfort. Straying from a solar-south design reduces wintertime heat gain and may increase summertime solar gain, leading to overheating. The more rooms that have some south windows, the better. This helps eliminate the need for fans or ducts to move warm air from one area to another. Place rooms that require less heat, such as workshops, bedrooms and kitchens, on the north side of the house.

Maximize windows on the south side. South glass should be a minimum of 7 percent of the house’s square footage for a sun-tempered home and a maximum of 12 percent for fully passive-solar designs. Don’t go wild on windows. Exceeding the 12 percent guideline for south windows may cause the home to overheat in summer, and may allow excess heat loss from the windows during the night and during long, cold, cloudy periods. Coleman recommends choosing south glass carefully for your climate. Many of the new low-emissivity (low-e) coatings reduce heat loss and gain, but for south windows you do not want glass that keeps out the solar heat. She recommends south glass that has a Solar Heat Gain Coefficient (SHGC) of at least 0.5. In warmer climates with properly designed south overhangs, uncoated double-pane glass is preferred.

Design the roof overhangs to shade windows properly from the high summer sun. Overhangs are key to successful solar homes. Judkoff says the exact geometry of overhangs is critical for balancing the need to admit maximum sunlight in winter and minimize solar heat gain in summer. Generally, the warmer and sunnier the climate, the deeper the overhang should be. A 2-foot overhang nicely shades an 8- to 9-foot wall in most locations. Coleman recommends the Web site http://www.susdesign.com/overhang/index.html to help you design overhangs properly. If overhangs aren’t possible, use insulated shutters to keep out the summer sun.

Provide thermal mass (tile floors and brick or masonry walls) in the south side of the house. Mass absorbs and stores heat when sunlight strikes it or when its temperature is lower than the air temperature. As the room’s air temperature drops below the mass’ surface temperature, heat is released and the air is warmed. Temperatures indoors remain relatively stable and comfortable, despite dramatic oscillations in outdoor temperatures. The mass in floors, framing, wallboard and furniture is usually sufficient to accommodate the solar heat in sun-tempered homes. But when you build a full passive-solar design with up to 12 percent south glass, you need to add extra thermal mass in the form of tile, concrete floors, or masonry walls or planters. For optimal results, some mass should be in direct contact with the incoming sunlight throughout the day. The mass also should be distributed throughout the house. Add about 7 square feet of 4-inch-thick mass for every 1 square foot of south glass above the 7 percent minimum. One easy, inexpensive way to add this mass is to choose a concrete slab-on-grade foundation. In addition to these solar design factors, follow these two principles that apply to all energy-efficient homes:

Insulate and seal the structure well. Careful attention to detail is essential. Insulation should not be compressed and air should not leak in. If you can’t get as much south glass as you would like, adding extra insulation can result in the same overall lower-energy consumption. Judkoff recommends insulating at least to the level prescribed by the International Energy Conservation Code or ASHRAE 90.2, which are region-specific recommendations for the building-envelop elements and mechanical systems. Choose energy-efficient windows and consider using insulated shades to keep heat from escaping at night (and to keep the heat out in the summer), especially in cold climates.