Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.
“California Looks to Stationary Energy Storage as a Solution to Peaker Plants” • Central California electric utility Pacific Gas & Electric is planning to replace three old natural gas power plants in its network with stationary energy storage installations from Tesla. California is looking to add 1.3 GW of storage to its power grid by 2020. [CleanTechnica]

Second-generation technologies include solar heating and cooling, wind power, modern forms of bioenergy and solar photovoltaics. These are now entering markets as a result of research, development and demonstration (RD&D) investments since the 1980s. The initial investment was prompted by energy security concerns linked to the oil crises (1973 and 1979) of the 1970s but the continuing appeal of these renewables is due, at least in part, to environmental benefits. Many of the technologies reflect significant advancements in materials.
Biomass, biogas and biofuels are burned to produce heat/power and in doing so harm the environment. Pollutants such as sulphurous oxides (SOx), nitrous oxides (NOx), and particulate matter (PM) are produced from this combustion; the World Health Organisation estimates that 7 million premature deaths are caused each year by air pollution.[102] Biomass combustion is a major contributor.[102][103][104]

In its 2014 edition of the Technology Roadmap: Solar Photovoltaic Energy report, the International Energy Agency (IEA) published prices for residential, commercial and utility-scale PV systems for eight major markets as of 2013 (see table below).[2] However, DOE's SunShot Initiative has reported much lower U.S. installation prices. In 2014, prices continued to decline. The SunShot Initiative modeled U.S. system prices to be in the range of $1.80 to $3.29 per watt.[76] Other sources identify similar price ranges of $1.70 to $3.50 for the different market segments in the U.S.,[77] and in the highly penetrated German market, prices for residential and small commercial rooftop systems of up to 100 kW declined to $1.36 per watt (€1.24/W) by the end of 2014.[78] In 2015, Deutsche Bank estimated costs for small residential rooftop systems in the U.S. around $2.90 per watt. Costs for utility-scale systems in China and India were estimated as low as $1.00 per watt.[79]
Climate change and global warming concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization.[10] New government spending, regulation and policies helped the industry weather the global financial crisis better than many other sectors.[24] According to a 2011 projection by the International Energy Agency, solar power generators may produce most of the world's electricity within 50 years, reducing the emissions of greenhouse gases that harm the environment.[25]

Another economic measure, closely related to the energy payback time, is the energy returned on energy invested (EROEI) or energy return on investment (EROI),[131] which is the ratio of electricity generated divided by the energy required to build and maintain the equipment. (This is not the same as the economic return on investment (ROI), which varies according to local energy prices, subsidies available and metering techniques.) With expected lifetimes of 30 years,[132] the EROEI of PV systems are in the range of 10 to 30, thus generating enough energy over their lifetimes to reproduce themselves many times (6–31 reproductions) depending on what type of material, balance of system (BOS), and the geographic location of the system.[133]
Outline of energy Energy Units Conservation of energy Energetics Energy transformation Energy condition Energy transition Energy level Energy system Mass Negative mass Mass–energy equivalence Power Thermodynamics Quantum thermodynamics Laws of thermodynamics Thermodynamic system Thermodynamic state Thermodynamic potential Thermodynamic free energy Irreversible process Thermal reservoir Heat transfer Heat capacity Volume (thermodynamics) Thermodynamic equilibrium Thermal equilibrium Thermodynamic temperature Isolated system Entropy Free entropy Entropic force Negentropy Work Exergy Enthalpy
In 2006 California approved the 'California Solar Initiative', offering a choice of investment subsidies or FIT for small and medium systems and a FIT for large systems. The small-system FIT of $0.39 per kWh (far less than EU countries) expires in just 5 years, and the alternate "EPBB" residential investment incentive is modest, averaging perhaps 20% of cost. All California incentives are scheduled to decrease in the future depending as a function of the amount of PV capacity installed.
For a 6 kW wind turbine to produce that much energy per average year, you need an annual average wind speed of close to 5 m/s (11 mph) blowing at turbine hub height. It may not sound like much, but that is a reasonably windy place. Much of North America does not have that much wind at 100′ or below. Keep in mind, you need that much wind just to break even in energy production vs. solar. To outweigh the disadvantages of small turbines you better have more!
Wind is a form of solar energy and is a result of the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and the rotation of the earth. Wind flow patterns and speeds vary greatly across the United States and are modified by bodies of water, vegetation, and differences in terrain. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity.
Other renewable energy technologies are still under development, and include cellulosic ethanol, hot-dry-rock geothermal power, and marine energy.[156] These technologies are not yet widely demonstrated or have limited commercialization. Many are on the horizon and may have potential comparable to other renewable energy technologies, but still depend on attracting sufficient attention and research, development and demonstration (RD&D) funding.[156]
We've had our system running for about 6 months now, whole process took a little over 2 months, other than submitting a form to our HOA and reviewing/signing some docs, Brio took care of the whole thing. The system works great, one month after it was running our power bill with Duke went to $0! Even in the summer when it's usually really high, honestly we were kinda skeptical but it's worked as promised. We're in NC and mainly worked with Brendan, he explained everything clearly and has been very responsive whenever we had questions.... read more
This discussion is mainly about factory-made grid-tie wind turbines. The off-grid crowd has an entirely different set of decisions and goals. The main ones are that for off-grid use economic viability in comparison with the electrical grid is not an issue, and a wind turbine can make up for the loss of sunlight (and PV electricity) in the winter months. For the DIY group there are several good turbine designs available; Hugh Piggott and the two Dans have written books that outline this step-by-step. Building your own turbine can be a great hobby, and some of the topics touched below apply (such as proper site selection), but this discussion is not about those. The decisions involved in making your own turbine, and the cost basis, have little overlap with a the process of having an installer put a factory-made turbine in your backyard.
At the end of 2014, worldwide PV capacity reached at least 177,000 megawatts. Photovoltaics grew fastest in China, followed by Japan and the United States, while Germany remains the world's largest overall producer of photovoltaic power, contributing about 7.0 percent to the overall electricity generation. Italy meets 7.9 percent of its electricity demands with photovoltaic power—the highest share worldwide.[119] For 2015, global cumulative capacity is forecasted to increase by more than 50 gigawatts (GW). By 2018, worldwide capacity is projected to reach as much as 430 gigawatts. This corresponds to a tripling within five years.[120] Solar power is forecasted to become the world's largest source of electricity by 2050, with solar photovoltaics and concentrated solar power contributing 16% and 11%, respectively. This requires an increase of installed PV capacity to 4,600 GW, of which more than half is expected to be deployed in China and India.[121]
Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.
Solar heating systems are a well known second-generation technology and generally consist of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage, and a reservoir or tank for heat storage and subsequent use. The systems may be used to heat domestic hot water, swimming pool water, or for space heating.[21] The heat can also be used for industrial applications or as an energy input for other uses such as cooling equipment.[22] In many climates, a solar heating system can provide a very high percentage (20 to 80%) of domestic hot water energy. Energy received from the sun by the earth is that of electromagnetic radiation. Light ranges of visible, infrared, ultraviolet, x-rays, and radio waves received by the earth through solar energy. The highest power of radiation comes from visible light. Solar power is complicated due to changes in seasons and from day to night. Cloud cover can also add to complications of solar energy, and not all radiation from the sun reaches earth because it is absorbed and dispersed due to clouds and gases within the earth's atmospheres.[23]

As of 2011, small solar PV systems provide electricity to a few million households, and micro-hydro configured into mini-grids serves many more. Over 44 million households use biogas made in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cookstoves.[26] United Nations' Secretary-General Ban Ki-moon has said that renewable energy has the ability to lift the poorest nations to new levels of prosperity.[14] At the national level, at least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond, and some 120 countries have various policy targets for longer-term shares of renewable energy, including a 20% target of all electricity generated for the European Union by 2020. Some countries have much higher long-term policy targets of up to 100% renewables. Outside Europe, a diverse group of 20 or more other countries target renewable energy shares in the 2020–2030 time frame that range from 10% to 50%.[11]

We've had our system running for about 6 months now, whole process took a little over 2 months, other than submitting a form to our HOA and reviewing/signing some docs, Brio took care of the whole thing. The system works great, one month after it was running our power bill with Duke went to $0! Even in the summer when it's usually really high, honestly we were kinda skeptical but it's worked as promised. We're in NC and mainly worked with Brendan, he explained everything clearly and has been very responsive whenever we had questions.... read more
Some of the second-generation renewables, such as wind power, have high potential and have already realised relatively low production costs. At the end of 2008, worldwide wind farm capacity was 120,791 megawatts (MW), representing an increase of 28.8 percent during the year,[30] and wind power produced some 1.3% of global electricity consumption.[31] Wind power accounts for approximately 20% of electricity use in Denmark, 9% in Spain, and 7% in Germany.[32][33] However, it may be difficult to site wind turbines in some areas for aesthetic or environmental reasons, and it may be difficult to integrate wind power into electricity grids in some cases.[10]
Over $1 billion of federal money has been spent on the research and development of hydrogen and a medium for energy storage in the United States.[150] Both the National Renewable Energy Laboratory[151] and Sandia National Laboratories[152] have departments dedicated to hydrogen research. Hydrogen is useful for energy storage, and for use in airplanes and ships, but is not practical for automobile use, as it is not very efficient, compared to using a battery — for the same cost a person can travel three times as far using a battery electric vehicle.[153]
Renewable energy is energy that is collected from renewable resources, which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat.[3] Renewable energy often provides energy in four important areas: electricity generation, air and water heating/cooling, transportation, and rural (off-grid) energy services.[4]
The Desert Sunlight Solar Farm is a 550 MW power plant in Riverside County, California, that uses thin-film CdTe-modules made by First Solar.[41] As of November 2014, the 550 megawatt Topaz Solar Farm was the largest photovoltaic power plant in the world. This was surpassed by the 579 MW Solar Star complex. The current largest photovoltaic power station in the world is Longyangxia Dam Solar Park, in Gonghe County, Qinghai, China.
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