Manufacturers often claim that their vertical axis turbine is superior to a horizontal one, because it always faces the wind. So does any horizontal axis turbine, thanks to their tail or yaw mechanism. If the airflow is such that wind directions change drastically from one second to the next it means you have lots of turbulence, and that means it is a poor place to put any wind turbine, HAWT or VAWT.
Most installers overrate the available wind resource. The majority of small wind turbine installations underperforms their predictions, often by a wide margin. Since wind speed is the most important parameter for turbine energy production, getting that wrong has large consequences (the power in the wind goes with the cube of the wind speed, so double the wind speed and the power in it is 2 * 2 * 2 = 8x as much). You have to be realistic about your annual average wind speed.
As the section above shows, anything under 5 m/s annual average wind speed is not going to be worth-while if you want any economic benefit out of a wind turbine. Even with government incentives, you would be better off with solar for most places. Let us take this a bit further, and assume your backyard is pretty windy, a full 6 m/s (13.4 mph) annual average wind speed at 100′ height. You get a 6 kW wind turbine installed, and shell out $50,000 for that privilege. If the installer did her job properly, the turbine is spinning in nice, clean, laminar air, and it will produce around 13,000 kWh per year. You are the kind of person that wins the lottery on a regular basis, marries a beauty queen (or king), and has kids that all go to ivy-league universities; your wind turbine never breaks and you do not have to shell out a single buck for maintenance over 20 years. Now your turbine has produced around 260,000 kWh of electricity, which works out to 19.2 cents per kWh in cost. Maybe you pay more than for electricity and it is worth it, but your are likely not getting rich, and any repairs and maintenance will drive that price up in a hurry.
The energy it calculates is in kWh per year, the diameter of the wind turbine rotor is in meters, the wind speed is annual average for the turbine hub height in m/s. The equation uses a Weibull wind distribution with a factor of K=2, which is about right for inland sites. An overall efficiency of the turbine, from wind to electrical grid, of 30% is used. That is a reasonable, real-world efficiency number. Here is a table that shows how average annual wind speed, turbine size, and annual energy production relate:
"Eggbeater" turbines, or Darrieus turbines, were named after the French inventor, Georges Darrieus.[31] They have good efficiency, but produce large torque ripple and cyclical stress on the tower, which contributes to poor reliability. They also generally require some external power source, or an additional Savonius rotor to start turning, because the starting torque is very low. The torque ripple is reduced by using three or more blades which results in greater solidity of the rotor. Solidity is measured by blade area divided by the rotor area. Newer Darrieus type turbines are not held up by guy-wires but have an external superstructure connected to the top bearing.[32]

According to the International Energy Agency, new bioenergy (biofuel) technologies being developed today, notably cellulosic ethanol biorefineries, could allow biofuels to play a much bigger role in the future than previously thought.[41] Cellulosic ethanol can be made from plant matter composed primarily of inedible cellulose fibers that form the stems and branches of most plants. Crop residues (such as corn stalks, wheat straw and rice straw), wood waste and municipal solid waste are potential sources of cellulosic biomass. Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be sustainably produced in many regions of the United States.[42]
Geothermal energy is produced by tapping into the thermal energy created and stored within the earth. It arises from the radioactive decay of an isotope of potassium and other elements found in the Earth's crust.[144] Geothermal energy can be obtained by drilling into the ground, very similar to oil exploration, and then it is carried by a heat-transfer fluid (e.g. water, brine or steam).[144] Geothermal systems that are mainly dominated by water have the potential to provide greater benefits to the system and will generate more power.[145] Within these liquid-dominated systems, there are possible concerns of subsidence and contamination of ground-water resources. Therefore, protection of ground-water resources is necessary in these systems. This means that careful reservoir production and engineering is necessary in liquid-dominated geothermal reservoir systems.[145] Geothermal energy is considered sustainable because that thermal energy is constantly replenished.[146] However, the science of geothermal energy generation is still young and developing economic viability. Several entities, such as the National Renewable Energy Laboratory[147] and Sandia National Laboratories[148] are conducting research toward the goal of establishing a proven science around geothermal energy. The International Centre for Geothermal Research (IGC), a German geosciences research organization, is largely focused on geothermal energy development research.[149]
The British Energy Savings Trust report titled “Location, location, location”: This requires some reading-between-the-lines as the Trust is rather closely aligned with the small wind industry. They looked at 57 turbines for a year, a number of them building mounted, others tower mounted, and concluded that building mounted turbines did very poorly.

The world of small wind turbines is much like the wild-west of a century ago: Anything goes, and no claim is too bold. Wind turbine manufacturers will even routinely make claims that are not supported by the Laws of Physics. Energy production claims are often exaggerated, as are power curves. In fact, this is the rule, not the exception. Those manufacturers that tell the truth are the exception. Many manufacturers have never tested their wind turbines under real-world conditions. Some have never tested their turbine before selling it to unsuspecting customers. We are not joking! Because we sell grid-tie inverters for small wind turbines we have a front-row seat when it comes to actual operation of turbines of many makes and models. It turns out that some do not work; they self-destruct within days, and sometimes run away and blow their inverter within seconds after being turned onfor  the first time (clearly nobody at the factory bothered to ever test it).
Turbines used in wind farms for commercial production of electric power are usually three-bladed. These have low torque ripple, which contributes to good reliability. The blades are usually colored white for daytime visibility by aircraft and range in length from 20 to 80 meters (66 to 262 ft). The size and height of turbines increase year by year. Offshore wind turbines are built up to 8(MW) today and have a blade length up to 80 meters (260 ft). Usual tubular steel towers of multi megawatt turbines have a height of 70 m to 120 m and in extremes up to 160 m.
In the case of a “wind turbine generator”, the wind pushes directly against the blades of the turbine, which converts the linear motion of the wind into the rotary motion necessary to spin the generators rotor and the harder the wind pushes, the more electrical energy can be generated. Then it is important to have a good wind turbine blade design to extract as much energy out of the wind as possible.
The comments stand in contrast to those made by Trump administration representatives also speaking at the energy summit, which is known as CERAWeek. Rick Perry, the energy secretary, on Wednesday criticized what he described as the “mind-set of the Paris agreement” that he contends supports renewable energy to the exclusion of other energy sources. And he took aim at countries pledging to phase out coal use.
We harness the earth’s most abundant resources – the strength of the wind, the heat of the sun and the force of water – to power the world’s biggest economies and the most remote communities. Combining onshore and offshore wind, hydro and innovative technologies, GE Renewable Energy has installed more than 400+ gigawatts capacity globally to make the world work better and cleaner.
Technologies promote sustainable energy including renewable energy sources, such as hydroelectricity, solar energy, wind energy, wave power,[citation needed] geothermal energy, bioenergy, tidal power and also technologies designed to improve energy efficiency. Costs have decreased immensely throughout the years, and continue to fall. Increasingly, effective government policies support investor confidence and these markets are expanding. Considerable progress is being made in the energy transition from fossil fuels to ecologically sustainable systems, to the point where many studies support 100% renewable energy.
The Vestas V164 has a rated capacity of 8 MW,[79] later upgraded to 9.5 MW.[80][81] The wind turbine has an overall height of 220 m (722 ft), a diameter of 164 m (538 ft), is for offshore use, and is the world's largest-capacity wind turbine since its introduction in 2014. The conventional drive train consist of a main gearbox and a medium speed PM generator. Prototype installed in 2014 at the National Test Center Denmark nearby Østerild. Series production began end of 2015.
When a turbine is mounted on a rooftop the building generally redirects wind over the roof and this can double the wind speed at the turbine. If the height of a rooftop mounted turbine tower is approximately 50% of the building height it is near the optimum for maximum wind energy and minimum wind turbulence. While wind speeds within the built environment are generally much lower than at exposed rural sites,[29][30] noise may be a concern and an existing structure may not adequately resist the additional stress.
Sunforce Wind Generators are primarily used to recharge all types of 12-Volt batteries, including lead-acid automotive batteries, deep-cycle (traction type) batteries, gel-cell batteries, and heavy-duty (stationary type) batteries. When using this wind generator to run appliances on a regular basis, the use of deep-cycle marine batteries is recommended. This type of battery is designed to withstand the frequent charge and discharge cycles associated with wind power use. Attempting to run the wind generator on an open circuit without a battery may cause damage to the generator or connected equipment.

Thermal storage technologies allow heat or cold to be stored for periods of time ranging from hours or overnight to interseasonal, and can involve storage of sensible energy (i.e. by changing the temperature of a medium) or latent energy (i.e. through phase changes of a medium, such between water and slush or ice). Short-term thermal storages can be used for peak-shaving in district heating or electrical distribution systems. Kinds of renewable or alternative energy sources that can be enabled include natural energy (e.g. collected via solar-thermal collectors, or dry cooling towers used to collect winter's cold), waste energy (e.g. from HVAC equipment, industrial processes or power plants), or surplus energy (e.g. as seasonally from hydropower projects or intermittently from wind farms). The Drake Landing Solar Community (Alberta, Canada) is illustrative. borehole thermal energy storage allows the community to get 97% of its year-round heat from solar collectors on the garage roofs, which most of the heat collected in summer.[58][59] Types of storages for sensible energy include insulated tanks, borehole clusters in substrates ranging from gravel to bedrock, deep aquifers, or shallow lined pits that are insulated on top. Some types of storage are capable of storing heat or cold between opposing seasons (particularly if very large), and some storage applications require inclusion of a heat pump. Latent heat is typically stored in ice tanks or what are called phase-change materials (PCMs).

In October 2018, the American Council for an Energy-Efficient Economy (ACEEE) released its annual "State Energy Efficiency Scorecard." The scorecard concluded that states and electric utility companies are continuing to expand energy efficiency measures in order to meet clean energy goals. In 2017, the U.S. spent $6.6 billion in electricity efficiency programs. $1.3 billion was spent on natural gas efficiency. These programs resulted in 27.3 million megawatt hours (MWh) of electricity saved.[160]
Wind turbines do work; put them in nice, smooth air and their energy production is quite predictable (we will get to predicting it a bit further on in this story). The honest manufacturers do not lie or exaggerate, their turbines really can work as advertised in smooth, laminar airflow. However, put that same turbine on a 40 feet tower and even if the annual average wind speed is still 5 m/s at that height, its energy production will fall far short of what you would predict for that value. How short is anybody’s guess, that is part of the point; it is impossible to predict the effect of turbulence other than that it robs the energy production potential of any wind turbine. Roof tops, or other locations on a house, make for poor turbine sites. They are usually very turbulent and on top of that their average wind speeds are usually very low.

Sunforce Wind Generators are primarily used to recharge all types of 12-Volt batteries, including lead-acid automotive batteries, deep-cycle (traction type) batteries, gel-cell batteries, and heavy-duty (stationary type) batteries. When using this wind generator to run appliances on a regular basis, the use of deep-cycle marine batteries is recommended. This type of battery is designed to withstand the frequent charge and discharge cycles associated with wind power use. Attempting to run the wind generator on an open circuit without a battery may cause damage to the generator or connected equipment.

My system has been installed for about a year now. When I first contracted with Envismart, the sales rep was very available and eager to help with my questions but after the installation, he was very hard to make contact with, seldom returned my calls, and when he did seemed to tell me what he thought I wanted hear and very seldom followed through. The system had a shaky start, it died after one day and after two new inverters and several optimizers over several months of on again, off again operation it seems to be running smoothly, at least for the last few months. Customer support was not very good, to be kind, but the service personnel that came out were prompt and there when they said they would be and very open about what the problems were and quickly fixed them. I was told my recurring system problems were a little unusual and I have to take their word on that but they gave me their personnel cell numbers and told me to call them when I couldn't get Customer Support to call - and when I called them, they came through and got me serviced a lot more quickly. They are the main reason I rated the company a 3.I have to say, the last month or so, it seems like the company is starting to work on changing its image. I have been called on several occasions by the "Quality Assurance" group at their initiation and asked if everything was OK with my system and I usually had an issue about something (admittedly, sometimes very minor). They always followed through with answers and corrected my concerns which was a big change from my previous experiences. I want to encourage them to continue improving their Customer Support after the sale in this manner as that is the real reputation for their company. I am still reserving my opinion but I am very much encouraged by their recent efforts - Keep it up!... read more

These include E-glass/carbon, E-glass/aramid and they present an exciting alternative to pure glass or carbon reinforcements. that the full replacement would lead to 80% weight savings, and cost increase by 150%, while a partial (30%) replacement would lead to only 90% cost increase and 50% weight reduction for 8 m turbine. The world currently longest wind turbine rotor blade, the 88.4 m long blade from LM Wind Power is made of carbon/glass hybrid composites. However, additional investigations are required for the optimal composition of the materials [50]
^ Jump up to: a b c d Alsema, E.A.; Wild – Scholten, M.J. de; Fthenakis, V.M. Environmental impacts of PV electricity generation – a critical comparison of energy supply options Archived 6 March 2012 at the Wayback Machine. ECN, September 2006; 7p. Presented at the 21st European Photovoltaic Solar Energy Conference and Exhibition, Dresden, Germany, 4–8 September 2006.
A 1.5 (MW) wind turbine of a type frequently seen in the United States has a tower 80 meters (260 ft) high. The rotor assembly (blades and hub) weighs 22,000 kilograms (48,000 lb). The nacelle, which contains the generator, weighs 52,000 kilograms (115,000 lb). The concrete base for the tower is constructed using 26,000 kilograms (58,000 lb) reinforcing steel and contains 190 cubic meters (250 cu yd) of concrete. The base is 15 meters (50 ft) in diameter and 2.4 meters (8 ft) thick near the center.[43]
Energy engineering Oil refinery Fossil-fuel power station Cogeneration Integrated gasification combined cycle Electric power Nuclear power Nuclear power plant Radioisotope thermoelectric generator Solar power Photovoltaic system Concentrated solar power Solar thermal energy Solar power tower Solar furnace Wind power Wind farm High-altitude wind power Geothermal power Hydropower Hydroelectricity Wave farm Tidal power Biomass
It is unfortunate to see how well marketing for small wind turbines is working: I often see people post questions on forums, where they are looking for a wind turbine “with a low cut-in wind speed”. Depending on whom you ask, the cut-in wind speed is either the wind speed where the turbine starts turning, or the wind speed where it starts to produce some power. For most wind turbines it is around 2.5 – 3.5 m/s (5.5 – 8 mph), and it is an utterly meaningless parameter.
Current Texas solar incentives include generous rebates for solar electric and solar hot water systems.  When combined with Federal solar rebates your solar panel installation will be approximately 50% less because of the incentives!  Our solar installers will be happy to answer your questions and explain the benefits of solar power.  Simply click the image below, fill in the form, and a certified solar installer will contact you by phone at your convenience.
The energy number that is left over should be a good approximation of what you can expect from that VAWT. Compare the resulting numbers with those mentioned in just about all sales brochures of VAWT type turbines and it should be immediately clear that their marketing people are smoking The Good Stuff. There is no relation to physical reality in their numbers, they are consistently much too high. Keep in mind that the energy production numbers calculated here are ‘best case’; for a turbine in nice, smooth air. Most VAWTs are placed very close to the ground, or on buildings, where there is little wind and lots of turbulence. Under those conditions they will do much, much worse than predicted.
Solar power is produced by collecting sunlight and converting it into electricity. This is done by using solar panels, which are large flat panels made up of many individual solar cells. It is most often used in remote locations, although it is becoming more popular in urban areas as well. This page contains articles that explore advances in solar energy technology.
Commercial concentrating solar power (CSP) plants, also called "solar thermal power stations", were first developed in the 1980s. The 377 MW Ivanpah Solar Power Facility, located in California's Mojave Desert, is the world’s largest solar thermal power plant project. Other large CSP plants include the Solnova Solar Power Station (150 MW), the Andasol solar power station (150 MW), and Extresol Solar Power Station (150 MW), all in Spain. The principal advantage of CSP is the ability to efficiently add thermal storage, allowing the dispatching of electricity over up to a 24-hour period. Since peak electricity demand typically occurs at about 5 pm, many CSP power plants use 3 to 5 hours of thermal storage.[65]
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