Renewable Energy, clean, green, and affordable, but held captive by an aging grid!

Renewable Energy referred to as RE for the purposes of this blog generally provides a great deal of economic opportunities as in profits and job creation, however that area of discussion is for another day.  RE can also provide a plethora of discussion about roadblocks.  One of the key roadblocks of (RE) is how to integrate all of the energy created into what is called the “electrical grid.” RE, in this discussion refers to the most common two (2) types of clean energy or green energy generation such as wind or solar.    

The first issue is that the net resulting production of clean energy is variable and not constant.  A typical coal fired or nuclear power plant produces “dispatchable” energy.   This is the type of electrical energy the grid(s) like to receive.  Unless the renewable energy is paired with a system of storage (more on this later), RE produces variable power.  

Some of the reasons for variable energy production is due to a lower than average amount of sun available, nighttime conditions, dirt of debris such as snow on the panels.  These all describe issues related to Solar Photovoltaic (Solar PV) systems.  When we consider wind generation, other issues come in to play.  For example low wind speed, no wind, lack of wind shear or cycling down the generators for maintenance of for optimal use strategies.  See photo below of snow partially covering Solar PV panels in Northern Indiana: 

Image provided by author.

 In addition, turning back to wind again, a low wind velocity or a loss of appropriate wind speed can create less favorable conditions.  The optimal scenario is having an adequate amount of “Wind Shear” available.  This is a term the renewable wind industry continuously mentions and is a condition that is crucial to the “efficient” generation of wind electrical energy.  If the wind shear is reduced efficiency also suffers.  What is wind shear exactly?  Wind Shear is the main reason why wind turbines are taller than many of the tallest buildings built. The tall designs allows the equipment to capture and “harvest” the stronger winds aloft during extreme wind shear conditions.  Incidentally, most of the higher winds also occur at night and this is when much of the power generation occurs.  Wind shear is a function of wind speed at different heights.  As turbines continue to get taller they are met with increasingly higher degrees of wind shear.  Additional information and a deeper dive into wind shear can be found at: http://ramblingsdc.net/wtnoise.html.

Returning to the idea of real roadblocks, naysayers of RE only focus on these dimensions of RE reliability or lack of being dispatchable in methods to denounce or refute the advantages of the clean power sources.  In addition to previously mentioned issues are the fact that the “electric grid” is actually three grids called Interconnections, which move electricity around the country.  

The Eastern Interconnection operates in states east of the Rocky Mountains, The Western Interconnection covers the Pacific Ocean to the Rocky Mountain States, and the smallest -- the Texas Interconnected system -- covers most of Texas, as displayed in the map below:

Grid Map Resource: http://www.geni.org/globalenergy/library/national_energy_grid/united-states-of-america/americannationalelectricitygrid.shtml

So the opposition to renewable energy is partially based on the argument that the grid can’t “take” or receive any more than about 15% of the RE being produced without making vast improvements to the grid.  It is important to point out, however, when many of the coal fired plants come off line today they are being replaced with new plants that combine some form of RE with natural gas fired systems.  Going back to the grid issue for example, curtailment will occur after a series of super sunny days) when the supply RE exceeds the capacity of the transmission lines. Alternatively, in cases when too much power from wind is being generated in Texas for example, some of the power being produced is also “curtailed” or sent to the earth (grounded).  This is sad and wasteful.  Thus many proponents of the RE movement over the years have determined why it is so important to include some type of storage technology to pair with the wind or Solar PV.  Under conditions of increased wind generation or Solar PV output, the additional power would be sent to the system of interconnected “smart batteries“ for use in the future when production of RE is down.  Below is an image of a “smart battery” system:

Image provided by author.

Most of the battery systems come in a variety of sizes and can be configured for quick release or a slower release over time.  A system such as this can be configured with a range of 125 kW – 375 kW 1 hour systems through a 100 kW 5 and 6 hour systems.  The release is when the battery is discharging for use by an end user, owner or to send to the grid.  These units are expensive and are equipped with many safety and unit protection as well as control features.  They normally have two (2) types of cooling systems designed to cool the batteries as well as the inverters (device that converts RE DC voltage into AC voltage).  A control system ensures proper charge/discharge procedures are deployed as well as sensors and inputs for gathering information’s about vital components and operational data. 

In summary, after a very quick look at Renewable Energy and the “manageable” pitfalls associated with it, now is not the time to turn our backs on the continued development of these technologies which will be able to provide all of us with a brighter and cleaner future.  Any discussion about infrastructure upgrades should include plans to upgrade the aging electric grid making it possible to receive any and all RE produced throughout the United States instead of curtailing the power that has been produced. 

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