There's so much to say about renewable energy. You can conceive it this way: imagine civilized life on Earth before the advent of the fossil-fuel era. Think of ancient Rome, the Italian Renaissance and the settlement of America, all of which took place using only sun, wind and water, along with draft animals, for power. Imagine that we could live healthy, happy and productive lives without electricity. This was reality for our great-grandparents (that is, if you're my age; if you're under 30, add another "great"). Think of Abe Lincoln in the White House, a once-habitable place to live and work without air conditioning (well, maybe not in July and August), gas furnaces and electric lighting.
As we start to bump up against the limits of planetary ecosystems to absorb all the waste and effluents made possible by fossil and nuclear fuels, we once again are reminded of the need to start living not off our inherited wealth, fossil fuels, but off our continuing income from the sun, wind, flowing water, geothermal energy and growing plants. Every 20 minutes, enough solar energy reaches the surface of the US to power the entire country for a whole year;128 the problem is gathering it and using it economically.
For green buildings the most important renewable sources for onsite energy production are solar, wind, small hydroelectric (for rural uses near a river or stream) and geothermal (the Earth's heat). For powering our vehicles and cities, we can look to biomass power such as ethanol from corn production (and possibly plant residues) and, in the future, possibly solar-electric hybrid and electric cars. In the farther future, solar- and wind-generated electricity might be used for making hydrogen to power cars and buildings with fuel cells.
Counting wood burned for fuel and electricity, as well as large hydroelectric projects, wind farms and biofuels, renewables currently account for about 12% of total US energy use.129 Many state legislatures are beginning to consider laws that would require electric utilities to produce 15% to 25% of their electricity from renewable sources within 20 years, by 2025 to 2030.130 A newly formed group encourages government programs to help America's farms, forests and ranches generate 25% of the country's total energy needs from sun, wind and biofuels by 2025.131
From a design perspective, the key to using renewable energy economically in buildings is reducing overall energy demand through building orientation, passive solar design techniques, more efficient building envelopes (insulation and glazing) and more efficient equipment, both HVAC systems and lighting, as well as reducing internal "plug loads" such as computers, printers, copiers and refrigerators. That way, the renewable energy systems will supply a higher percentage of the building's total energy demand for the same cost than in a less-efficient building.
A 2007 report by the American Solar Energy Society showed that re-newables such as solar, wind, biofuels, biomass and geothermal could supply a carbon reduction of more than 500 million metric tons per year, about 40% of the total needed to meet Kyoto treaty obligations.132 Using onsite renewable energy, green buildings have a critical role to play in reducing our carbon footprint.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.