Green energy has come a long way from the earlier rise of popularity of passive solar systems a few decades ago. Discussions of green energy still refer to solar energy systems, of course, but today, they also are likely to include wind, biomass, hydro systems and geothermal applications. One constant is that green energy discussions always refer to renewable energy.
1. What is renewable energy?
Renewable energy is that which uses energy sources that can be replenished over a short length of time. Alternatively, some renewable energy sources are not depleted at all when they are used to generate energy. Wind and the sun are two examples. Hydro systems provide another example, as does the use of the thermal systems that use the thermal energy stored in the Earth’s crust, near the surface. Energy generation systems that use biomass as their beginning source also are renewable under sound management, as we replant harvested trees, wheatgrass, corn and other plants that produce specific biomass materials used in energy production.
The term “renewable energy” also implies the absence of hazardous processes or byproducts of energy production. Though nuclear power generations systems certainly are renewable in the basic sense of the word, most discussions of renewable energy focus on green alternatives that do not pose any hazards to people or the environment. Though nuclear power generation has served to reduce the amount of carbon in the atmosphere and has slowed demand for coal and oil as fuels used to produce electricity, dramatic incidents such as Japan’s tsunami illustrate how green nuclear power generation is not. It is an option, but there are other options that are far less dangerous.
This also brings up another implication of the term renewable. Though the fuel used to produce electricity from nuclear power plants is used for a long time – which qualifies it as being renewable – the uranium in its natural state is not renewable at all. This point also applies to coal, oil and natural gas. Though each has come to exist through natural processes, those processes are exceedingly slow and none of those energy sources are renewable by us. Once they have been used, they are gone and no longer available.
2. Why is renewable energy preferred?
Nearly all of the energy sources that have to be extracted from deep in the ground – coal, oil and uranium – have negative environmental effects when transferred to the Earth’s surface and used for the purpose of producing energy, either in the form of electricity or fuel. Natural gas is much cleaner and can be used directly as it is extracted, but supplies of natural gas are finite too. All of the others have to be treated, refined, enriched, transported or undergo some other process that prepares it for use to produce electric or fuel energy.
This is not the case with the energy sources that we refer to as renewable. Electricity produced by wind or solar generation is produced at or near the point that it will be used. It requires no other inputs of resources other than the equipment necessary to produce the energy it creates. Where wind, sunlight or small – scale water movement exist, they continue to exist whether they are used for energy generation or not.
3. Can renewable energy be bought or sold?
Where renewable energy sources are connected to the electrical grids in their local areas, the electricity produced in excess of what the application needs can be sold to the local electrical utility. Conversely, the local electrical utility can direct electricity generated from green sources to those electricity customers with which it has contracted in green preference.
There are two ways that customers and utility operators accomplish buying and selling electricity from renewable sources. On a sunny day, a home or commercial business with a roof full of solar panels easily can produce more electricity than they can use themselves. Electricity generated from solar sources is stored in a bank of batteries, which release that electricity during the night time hours or on cloudy days when solar electricity production is diminished. Any excess electricity remaining after direct use and battery replenishing can then be sold back to the electrical utility. The customer’s meter actually backs up, and the electrical utility credits the customer’s bill with the electricity the customer has provided to the electrical utility.
Another common approach to buying electricity from green sources is that increasing numbers of electrical utilities establish and maintain their own renewable electricity production facilities, usually in the form of wind farms and expanses of solar panels.
In terms of fuel for transportation, most commercially available gasoline contains at least a small percentage of ethanol, a fuel produced from biomass. Increasing numbers of cars are equipped to deal with flex fuels, meaning that they can use the fuels containing only ten percent ethanol, or they can use fuels consisting of up to 85 percent ethanol.
4. How does geothermal energy work?
There are two types of geothermal applications. The least common to date is the large, commercial harnessing of steam or hot water from the Earth’s crust, which then is used to produce electricity. That type of geothermal application actively produces electricity, but it must be located where the driving force is active and easily accessible.
The other type that is far more common is that which uses the relatively constant temperature of the Earth to heat water or another liquid, which then is pumped through pipes throughout a residential or commercial building. The liquid releases its heat inside the space, then the cooled liquid returns to a grid of pipes in the ground, where it then warms again. The process is reversed in summer, where the liquid absorbs heat in above – ground locations and cools in the portion of the piping system that is in the ground. There are some large office buildings exclusively heated and cooled using a geothermal system located under their parking lots. The system requires a small electric pump to keep the liquid moving through the system, but it requires little or no electricity to heat or cool the air of the interior space.
5. How does a solar hot water heater work?
There were exceeding poor quality solar hot water heater systems available in the 1980s, establishing a negative reputation that has been difficult to overcome. There is little resemblance between those old systems and those available today. The solar hot water heater works by placing a network of water-containing pipes where they receive the maximum amount of direct sunlight possible, usually on the roof. As the water is used inside the structure, it is replaced with cold water that then is heated as well. There are tankless systems available, but most have a backup tank fueled with natural gas or electricity.
6. Is a solar hot water heater a worthwhile investment?
Today’s systems are reliable, but they are expensive too, commonly between $5,000 and $6,500. With a backup tank, the North Carolina Solar Center estimates that most residential customers can expect to save $300 a year in water heating costs. Using those figures, the system pays for itself in as little as sixteen years. In the meantime, its use reduces the household’s total carbon footprint.
7. Are attractive solar panels available?
Big, bulky and unattractive solar panels are about to slip into history. Several companies now manufacture and install thin – film laminate solar panels that are very nearly invisible over asphalt shingles or metal roofs. These new thin laminates can be applied directly to curved surfaces, and eliminate the need for the bulky panels of the early days of photovoltaic panels.
8. Are plug-in hybrid cars truly environmentally beneficial?
It can seem that those buying plug-in hybrid cars – or even fully electric cars that must be plugged in to charge – are merely transferring demand from one nonrenewable energy source to another. This is true where they are plugging into an electrical utility that relies on coal or oil to produce electricity, but there are other options that are beginning to emerge. One is to purchase only green electricity from the utility, but a simpler approach is to generate the needed electricity on site. As example, one North Carolina high school converted a standard pickup truck to an all-electric maintenance vehicle, and erected an array of solar panels. The panels produce all of the electricity that the maintenance vehicle needs, eliminating the need for any fossil fuel without adding any load to the local electrical grid.
9. Is biofuel here to stay?
Without question, adding ethanol to gasoline reduces our total consumption of petroleum to some degree. Critics argue that ethanol production uses more energy than it produces, however, and to date it has caused corn prices to skyrocket to the point that food animal producers no longer are able to operate their businesses profitably, even as meat and grain food prices increase. There are other biomass plants that can be used instead of corn, however, and production processes are improving to be more efficient. Corn likely will not remain the primary biomass input in the future, but biofuels likely are here to stay indeed.
10. What about hydropower?
Many large and impressive dams were built decades before we recognized the environmental costs of those dams. Those that exist still produce hydroelectricity, but there are newer approaches that carry less environment effect. One of those is the micro hydro system that uses free-flowing streams or rivers to produce up to 100 kilowatts of power. “Run of the river” systems use the kinetic energy of naturally moving water without the use of a dam. These are reliable in that moving water moves all of time, providing a steady, constant supply of electricity.
Green Energy Articles
- Green Incentives
- It Pays to Be Green
- LEED Certification
- Types of Green Energy
- Tips for a Greener Home
Green Energy Resources
- Distributed Power Generation. Solarbuzz.
- Frequently Asked Questions. Green-e.org
- [PDF] Geothermal Energy. North Carolina Solar Center
- Photovoltaic Applications. Solar Center Applications. North Carolina Solar Center
- [PDF] Residential Solar Hot Water Systems. North Carolina Solar Center
- What is a ground source heat pump? International Ground Source Heat Pump Association