The Pros and Cons of Wind Energy

Who knew passing wind would be so exhilarating?

Last month we discussed a few basic aspects of wind as a source of clean energy. We showed what wind was, how it forms and where it goes.  Then after going on a tangent about the history of turbines, we showed where on the Earth we could recover the highest amount of wind energy and how this potential changes with altitude. Today’s post offer the pros and cons of wind energy while touching upon several topics discussed in the previous post before diving into the optimal where and when.

Getting into the “What”

With an established worldwide potential of more than 400 TW (20 times more than what the entire human population needs) and a clean, renewable source wind is definitely attractive to the current and future generations. In terms of harvesting it, over 99% percent of wind farms in the USA are located in rural areas with 71% of them in low-income counties. Indeed, the more land is available (and the fewer buildings), the higher the possibility and interest to transform this kinetic energy into mechanical work and then most likely electricity.

Where one would see sporadic turbines on the side of the highway, these stand-alone equipment have begun to turn into actual modules (farms) that can work as an overall unit instead of individual ones. This strategy of creating a network of turbines follows the philosophy of “the Whole is Greater than the Sum of its Parts”. What this translates into is that by having 20 (arbitrary number) wind turbines working together to determine the best orientation, pitch, etc. of their blades in such a way that it least negatively impacts the downstream units we can produce more energy than if each of them were live-optimized individually (some interesting A.I. work is going into this). This means that the overall system is more efficient at converting energy and therefore it is more cost effective to provide bulk power to the electrical grid. This is similar to the concept in the post on solar energy comparing PV panels and CSP. Read the full post here. 

In terms of power production per wind turbine, the utility-scale ones range from about 100 kW to several MW for the land-based units (Offshore wind turbines are typically larger and produce more power – getting ahead of myself here but check out the figure below for wind potential in Western Europe that clearly showcases coast vs. non-coast data). On the low-power end of the spectrum, we find some below 100 kW for some non-utility applications like powering homes, telecommunications dishes, water pumping, etc. Solar power (PV) is generally regarded as the first choice for homeowners looking to become energy producers themselves, but wind turbines make an excellent alternative in some situations. It would take a wind turbine of about 10 kilowatts and $40,000 to $70,000 to become a net electricity producer. Investments like this typically break even after 10 to 20 years.

Wind potential in Western Europe
Figure 8 Wind potential in Western Europe – https://globalwindatlas.info/

Onto the “Where”

One of the elements of wind formation we covered in the last post here was a different in pressure (and therefore temperature). This simplification works rather well at the macro-scale, but as we zoom in closer to the surface we can see that wind flow speeds and patterns vary quite significantly based on more than just the general location of Earth. On top of the altitude we already discussed, factors like vegetation, presence of high-rise buildings or bodies of water come into play.

If you have ever left a beach towel by the water without putting rocks (or shoes) at the corners, then you already know the winds can be pretty strong at such land-water interfaces. Looking back at the figure from the previous section or even the maps shown last month it is easy to see that coastal regions are generally the most attractive when it comes to harnessing wind power. Despite this, 41 U.S. States have utility-scale wind farms today and the USA is the number two country (behind China) with the highest installed capacity for wind power generation which contributes to about 6% of the total U.S. electricity generation (> 80GW); both countries have very vast lands and rather long coast lines. Other remarkable countries with high rates of installed wind power include Denmark, Portugal and Ireland, which each get more than 20% of their nation’s electricity from wind energy. All three of these are peninsulas. Therefore, having vast land and/or access to water definitely helps with accessing this renewable energy source. One attractive aspect of wind turbines is that one can make use of the space between them for crops or grazing livestock.

Here is a quick comparison of different places regarding wind statistics, taken from https://globalwindatlas.info/:

Statistics on Wind

Now that we have seen locations of most interest for wind turbines let’s look at the reasons why it is an interesting source of energy as well as arguments made against it.

Here are a few of the main advantages of wind power:
  1. Cost-effective. Land-based utility-scale wind is one of the lowest-priced energy sources available today, costing between two and six cents per kilowatt-hour, depending on the wind resource and the particular project’s financing. Due to its relative stability for given locations and seasons, wind energy mitigates the price uncertainty that fuel costs add to traditional sources of energy.
  2. Clean Fuel Source. Wind energy does not pollute the air like power plants that rely on combustion of fossil fuels. Also, wind turbines do not produce atmospheric emissions that cause acid rain, smog, or greenhouse gases. The manufacturing of the equipment is of course as clean as the plant that produced it. Note that the release of greenhouse gases during manufacturing and installation of wind turbines are usually recouped within 9 months of clean operation.
  3. Domestic. It is abundant and inexhaustible, meaning renewable.
  4. Compatible with Existing Land Use. Wind turbines can be built on existing farms or ranches.This helps boost the economy of rural areas while allowing landowners to get a monthly rent check that would make their financial wellbeing less dependent upon yearly harvests.
  5. Extremely Low Operational Costs. Once the infrastructure is paid for (and beside maintenance) the power generated is almost free as the operational costs are low.
On the downside we can see the following:
  1. Steadiness. The main disadvantage of wind power is that the wind does not blow consistently or steadily. Indeed, wind is a fluctuating (intermittent) source of energy and is therefore not suited to meet the base load energy demand unless some form of energy storage is utilized (e.g. batteries, pumped hydro).
  2. Wildlife Impact. Not only birds, but bats have experienced fatalities (~10,000-440,000 per year in the USA). The same argument can be made against vehicles and stationary buildings (up to 976M) though.
  3. Localized Impact. Due to a change of the wind pattern, wind turbines may cause a localized impact on night-time temperatures and weather.
  4. Visual Pollution. This seemed to be the first complaint when wind turbines started to sprout, but it appears people are getting used to them.
  5. Noise. This is not a problem with offshore wind turbines at all. New designs for onshore installations show significant improvements compared to older models and generate less noise.
  6. Competition. Conventional power generation sources are currently cheaper in most places, so wind farming may not be cost-competitive even though prices have decreased significantly over the last decade.
  7. Location. Wind turbines need land or water. The electricity generated is usually used in urban areas, so transportation of the energy is required.
  8. Land Investments. Despite the fact that inter-turbines space can be used they may not be the most profitable land investment for the locals, especially in places where land is scarce like in Japan for example.
  9. Initial Capital Investment. The manufacturing, delivery (ever seen these oversized trucks carrying a single propeller on the road) and installation of wind turbines requires heavy upfront investments.
  10. Seasonal Potential. Winds are seasonal. The figure below showing regional wind trends across the USA throughout a selected year.
Monthly Wind Plant Capacity Factors
Figure 10 https://www.eia.gov/todayinenergy/detail.php?id=20112

Each of these unsteady factors make it difficult for companies to provide reliable estimates on wind power generation which represent a higher risk factors for some lenders/buyers.

In conclusions, we have seen where and when it was best to consider wind power and, we looked at the pros and cons of harnessing this renewable resource. Overall, wind speeds seem higher during spring and fall unlike the potential for solar energy, which was higher in the summer months. Based on the US national average, using solar and wind together seems to be the best option for clean energy generation throughout the year (see figure below).

Implications of diurnal and seasonal variations in renewable energy generation for large scale energy storage
Figure 11 Implications of diurnal and seasonal variations in renewable energy generation for large scale energy storage
Journal of Renewable and Sustainable Energy 6, 033105 (2014); https://doi.org/10.1063/1.4874845

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