The environmental impacts caused by traditional Horizontal Axis Wind Turbines (HAWTs) are quite small compared to alternative sources of energy—fossil fuels, nuclear and hydroelectric power.
The mining and burning of coal arguably have the greatest negative impacts on the environment.
Drilling, transporting and burning natural gas and diesel fuel can be less environmentally harmful than coal, but the list of negative effects caused by these energy sources is also long, especially absent expensive mitigation techniques.
If something goes wrong at a nuclear power plant, whether a generating malfunction or with the radioactive leak from its waste storage, the consequences can be catastrophic. Associated nuclear power environmental impacts are also high, including extracting uranium ore and the need for large amounts of water to cool the reactor core and used fuel rods.
Dams and reservoirs impede fish migration, destroy wildlife habitat by flooding land upstream, and cause other environmental impacts, including contributing to greenhouse gas emissions. When contrasted to these renewable resources, wind energy has a much smaller negative impact on the environment.
Vertical Axis Wind Turbines (VAWTs), especially when integrated into the understory of HAWT wind farms, may well have the least negative impact of any new, renewable energy technology.
Plentiful and inexpensive sources of renewable electrical energy will be critical to curtailing the consequences associated with global warming, including rising sea levels, more severe droughts and floods, and superstorms. Wind energy is one of the least expensive sources of electricity and complements solar energy, as wind farms often continue to produce power after the sun sets. Both attributes will drive its demand.
A major hindrance to the growth of wind energy is the same as the one that halted the growth in dam building. The best sites are built out first, making each subsequent dam or wind farm less cost-effective than the one before. For example, in California, the best wind resources were developed first, and now secondary sites cost more to develop, have more issues with endangered species and are farther away from transmission lines and customers. For both sources of renewable energy, each site has a limit to the total amount of power generation that can be realized. The size of the reservoir and annual precipitation in the watershed limits the generating capacity of a dam. Wind farm capacity is limited due to the required distance downwind that rows of HAWTs must be installed from one another, usually at least 10 rotor diameters. For a HAWT with a 50m diameter, the next row should be one-half kilometer downwind.
The best solution to the challenge of adding wind generation to an already fully developed site is to add Vertical Axis Wind Turbines (VAWTs) to the "understory" beneath and around the tall HAWTs.
Wind Harvest International predicts that VAWTs will achieve the efficiencies of HAWTs, and the costs to build them will drop, in the same way that HAWTs did in their early years of development. This will lead to VAWTs becoming among the least-expensive sources of new wind energy when placed in the understory of wind farms. Such project development and infrastructure costs should be significantly lower than those associated with new wind farms: the land is already purchased and zoned for wind energy; access and internal roads have been built; fencing and meteorological towers are in place; security, management, and administration is amortized over a larger capacity; and the higher density of turbines in itself should reduce operation and maintenance costs.
If research on small VAWTs by Stanford University Professor John Dabiri proves to be consistent with performance by larger VAWTs, such as WHI's G168, then understories of VAWTs should also increase the energy output of the HAWTs in a wind farm, further reducing the cost per kWh that can be achieved.
WHI’s analysis of wind farms and wind farm regions worldwide estimates that 25 percent of existing wind farms have good to excellent near-ground wind resources (6.5 –8+m/s (14.5 - 18 mph) average annual wind speeds). Coastal areas, mountain passes, ridgelines, hills, and mesas all often have a low wind shear, where the wind at 10m above ground level is nearly as strong as the wind at 30-50m (98-164 ft) above ground. Estimating a conservative increase of 8% per year in worldwide wind capacity, by 2030, HAWT capacity will be over 1 million MWs. WHI has a goal of stimulating the installation of 100,000 MWs of VAWTs in existing global wind farms, which is realistic, particularly after manufacturers of HAWTs enter the large and expanding VAWT understory marketplace.
Wind energy has one of the best Energy Returned on Energy Invested (EROEI) (aka “life cycle emissions”) of any energy option currently available. As part of its California Energy Commissions EPIC Program grant proposal, WHI calculated the CO2 produced in the making and installation of its G168 VAWT. Manufacturing the cement in the foundation, the steel for the arms, mast, shaft and base tower, and the aluminum in the blades produced the most CO2. However, it would take less than half a year's operation in a moderate wind site to offset all the CO2 produced in manufacturing the G168, an amount that compares favorably to the very low EROEIs of HAWTs.
Wind Harvest International anticipates that installing VAWTs in existing HAWT wind farms will result in a significant increase in the amount of renewable energy produced worldwide, energy that otherwise would not have been available. Energy produced in this fashion will be environmentally positive, since VAWTs that leverage the coupled vortex effect (CVE) have one of the best Energy-Returned-on-Energy-Invested of any option currently available, especially if they can increase the wind speeds that reach HAWTs and thus increase their energy output.
The mechanical sounds that emanate from older-model HAWTs have mostly been eliminated with better bearings, direct drive systems and other improvements in the newer models. The most noticeable noise created by HAWTs is the “aerodynamic swoosh of the blades passing the tower” The faster the blade tips move, the louder the swoosh, though “[i]t is possible to stand underneath a turbine and hold a conversation without having to raise your voice. As wind speed rises, the noise of the wind masks the noise made by wind turbines.” VAWT geometry and blade tip speeds ensure that they will be quieter than HAWTs.
Blade tips creating the swoosh noise in HAWTs are often traveling at 150–200-plus mph. Blade-tip speeds of WHI G168 VAWTs range from 40 mph at startup to a top speed of 90 mph. These lower tip speeds result in less noise. Mechanically, VAWTs are also inherently quieter. Their drive shafts are vertically oriented, and the weight of the rotor does not sit on one side of the bearings but rotates evenly between them. Also, VAWTs such as the WHI G168 that use direct-drive generators don’t require gearboxes, another potential source of noise.
Sound experts predict that the noise emanating from a pair of VAWTs will not travel significantly farther or be louder than that from a single VAWT. Third party-evaluated acoustical profiles for G168 VAWTs, both singly and in pairs, will be secured through the certification field testing process and made available.
HAWTs are known to have negative impacts on radar systems. Air-traffic regulations in many countries prohibit installing HAWTs near airports or in areas where they could decrease the effectiveness of radar and affect aviation or military safety. The taller and larger the HAWT rotors are, the more problematic they can become. VAWTs are significantly shorter than HAWTs and can be situated in the landscape such that they avoid radar interference. Moreover, their height allows VAWTs to become indistinguishable from the clutter created by similarly sized trees and objects.
Installing VAWTs in the understories of existing wind farms should not increase the already existing effect on local radar created by the taller HAWTs. If VAWTs are found to create a higher-than-allowable radar cross section (RCS), there is evidence to suggest that radar absorbent material (RAM) could be used to cover the main mast/shaft of the VAWT, typically the part contributing to radar interference.
The increasing use of drone technology is impacting the development of wind energy sites in areas proximate to air force bases and other places from which drones are flown.
In one instance, in Southern California, the US Air Force set a height restriction for wind farm sites of 26.5m (87 feet) within given distances from its bases. Wind Harvest International’s VAWT Systems are 18-25m tall (59-82 feet), and thus could open such sites to development.
The rotation of wind turbine blades can create shadows that “flicker” at regular intervals across the landscape. When the sun is low in the sky, these flashes of alternating light intensity through windows or into yards can create problems for nearby residents. In extreme cases, these shadow flickers can extend to windows more than a kilometer away from a tall, rotating HAWT.
VAWTs also create shadow flicker, but with some fundamental differences. The primary reason lies in their shorter heights and narrower rotors. The diameter of the rotor and the top of the blades of a standard-size WHI G168 VAWT is roughly one-fifth to one-tenth that of a modern HAWT. Their smaller size alone reduces the potential for problems that nearby residents might realize from shadow flicker induced by VAWTs.
The rotational speed of some VAWTs and smaller HAWTs could be a problem for people with photosensitive epilepsy, where strobe rates of 5 to 30 flashes per second can cause seizures. The WHI G168 VAWT has a maximum rotational speed of 67 rpm. At this speed, their three rotor blades can cast shadows that flicker 3.4 times per second. Large HAWT blades will flicker an average of once per second or slower.
Whenever G168 VAWTs are installed near homes and buildings, an evaluation should be conducted of the potential impacts of shadow flicker.
Large HAWTs began to populate high-wind sites in the late 1980s and early 1990s. In many regions of the world, people living close to the turbines objected to what they called “visual blight.” According to some, the beautiful countryside is disrupted by the spinning of the stark, tall, white turbines, attracting attention and marring the traditional view for miles. The last two decades have seen growing resistance to installing tall turbines in close proximity to communities. As a result, despite the availability of a high-wind resource, numerous local and national governments have enacted policies that preclude new turbine installations.
In certain jurisdictions, a turbine under a certain height (e.g., 60 feet or 20m) can secure an installation permit where taller turbines would be restricted. For a HAWT to be under 20m (65 ft), it has to be quite small, usually less that 5kW with 5m (16 ft) blades on a 15m (49 ft) tall tower. Yet a 100m- long row of the WHI G168 VAWTs would have a capacity of 560 kW and could still be completely compliant with the height restrictions.
Unlike the much-taller HAWTs, Wind Harvest International’s G168 VAWTs are significantly shorter, with the tips of the G168 VAWT blades on the lowest towers reaching a height of just 18m (59 ft). Visual studies using photo montage and computer-generated Zones of Theoretical Visibility can be used to place the VAWTs along ridge lines, among hills, and farther back in the landscape so as to significantly lessen the visual impact on nearby populations. These advantages promise to open otherwise unharvested wind resources in areas where taller HAWTs would not be permitted.