Sustainable Energy Options

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Sustainableenergyoptions.unl.edu

Sustainable Energy Options for Rural Nebraska is a research and demonstration project funded by the United State Department of Energy

 

Project Goals 

  • Demonstration of Small Wind and Solar Systems
  • Research related to realibility function of small wind and solar
  • Independent evaluation of ethanol fueled engines as a power source for irrigation pumping plants

Project Outputs

Wind Turbines and Solar Array's at Haskell Ag Lab What We've Learned 2012-2015

Solar and small wind turbines are options to add renewable energy on a farm, acreage or residence. Our experience demonstrates the successes and challenges with such systems.  The Haskell Ag Lab outside of Concord Nebraska is a 1 square mile research farm run by the University of Nebraska Lincoln.  We had the opportunity to install two small wind turbines and a solar array in 2012 with a grant from the United States Department of Energy.  Our goals for the renewable projects were twofold: research and demonstration.  The turbines would be typical size of ones installed at homes, farms or acreages. Solar arrays are scalable meaning a small array can easily represent any size array with some arithmetic. We have learned a lot from the process and our experiences represent a number of the trials, tribulations and successes common of such systems. 

 In choosing our wind turbines we wanted good turbines from reputable companies. We chose two turbines with similar attributes A 5 kW Evance and a 6 kW Eoltec, both manufactured in Europe. There are some good American turbines available today. Not all turbines available today are good  there are many crazy designs for wind turbines. Many of these unique designs also have flashy advertising and exaggerated production, the rules below apply at all turbines even if the advertisements or salesmen say otherwise.

 Wind Turbines Obey The Laws of Physics:

 Rule #1: No wind or slow wind = No power or almost no power

Rule #2: Small turbines = Small amount of power

Rule #3: Kinetic energy in wind is converted to rotational energy is always less than 59% efficient no  

                matter how innovative the design.

Rule #3a: Rotational energy means turbines spin: (spinning makes vibrations)(spinning is cool)

Rule #4: Turbines on buildings = almost no power  (because of Rules #1, #2 and #3 )

 The choice for wind turbines may be somewhat simplified in the future due to a new rule adopted by the federal government which requires turbines be certified if the purchaser wants to access the federal tax credit. This requirement will limit the list from dozens of turbine models to 13 with certification in summer 2015.  Gone should be the days to long claims the turbines will never live up to. Currently no vertical axis designs are certified.

 Solar Photovoltaic (PV) Panels Obey the Laws of Physics:

 Rule A: Solar panels need sunlight

Rule B: Shading is bad for solar panels (because of rule A)

Rule C: Tracking solar can produce more than stationary panels (because of rule A)

                Rule C-1: Tracking solar has moving parts. Moving parts increase maintenance

Rule D: Solar is good because it has no moving parts. (Solar is boring  because it has no moving parts. It

just sits there and produces electricity)

 When a renewable small wind or solar PV system are installed properly following the rules above, they have a significantly higher chance for success.  With that in mind we started our process and chose to work with a skilled and experienced installer.  We have farm crew and engineers on staff at the Haskell Ag Lab, but the specific knowledge of how to properly install wind and solar is invaluable to getting a long lived product.   Experience with how grid tied wind and solar systems relate to the electrical code is a critical piece of knowledge a skilled installers brings.

 WHAT WE INSTALLED:

 5 kW Evance wind turbine on a monopole tilt up tower

6 kW Eoltec wind turbine on a guy wired tilt up tower

6 Solar panels of varied manufacturers about 230 Watts each

 WHAT WE HAVE LEARNED 2012-2015: 

 SMALL WIND TURBINES

 INSTALLATION: 

 Not too bad! But need a tractor with loader or fork lift. A person with moderate technical skills and tractor with a loader can assemble a small wind turbine, yet trouble shooting issues and discrepancies between the actual parts and the manual is where an experienced installer is invaluable. An experienced installer can make sure the job is done right. Get an installer with experience and make sure to get references for installations which are still flying (turbines in operation are sometimes said to be flying).

 SAFETY:

 Safety is of greatest importance for both the owner of the renewable system and any utility workers who maintain power infrastructure.  All distributed generation systems must not feed electricity onto the grid then grid is down endangering the utility workers. Renewable systems accomplish this through safety features and proper inspections.  A disconnect switch between the inverter and the meter allows utility workers to have a visual confirmation the system is shut down.  In addition to the shut off inverters used in renewable systems are UL listed and will not put electricity onto the grid when they do not detect the grid. 

Follow the electrical code when designing and installing a system. If you do not have knowledge or experience with the code consult a professional.

Once installed systems should be inspected by a local electrical inspector to ensure all codes and other utility rules are followed.  Only after passing inspection is the system ready to turn on.

 MAINTENANCE:

 Wind turbines require maintenance, and even more when there is human error. Yes, we broke stuff! Maintenance requires accessing the turbines, either with a tilting tower which can be lowered or with a crane.  Either way attention to detail when raising or lowering is key to safe problem free maintenance.  We had an issue when we failed to remove one nut of the 14 holding the base to the foundation on our monopole tower.  That one nut held tight and bent the tower base when attempting to lower the tower.  This error cost us the price of repair and several months of the turbine out of operation.

Eoltec Generator

BALANCE OF THE SYSTEM:

It takes a lot of extra stuff! The balance of the system consists of all parts other than the main components. Main components are the turbine, tower and inverter.  The balance would then be wire, conduit, the materials to mount the inverter, etc.  It is critical to plan and pay close attention to what you will need to minimize your trips to the hardware store. There will still likely be a number of trips.

FOLLOW UP TO MAKE SURE YOU GET CREDIT:

 Make sure the power company does the math! After installation and commissioning is complete pay close attention to your utility bills. The inverter will tell how much energy is produced by the wind turbine or solar panels. Your utility bill should reflect this with a reduction in your bill resembling the magnitude of energy produced or a credit showing how much energy was put onto the grid. The net production minus consumption should be reflected on the bill.  Our system was inadvertently billed improperly for 3 years. We expressed concern about the issue early on but were assured there was no problem. After the issue became clear to us we pushed much harder and only after completing tests on our system to prove there was a billing error was the issue corrected. The system was installed properly but billing numbers were switched and we were being billed for what we were delivering to the grid and credited for what we were using.

WIND TURBINES ARE COOL (see Rule #3):

Wind turbines have spinning rotor which can be seen from a great distance. This is both good and bad! Wind turbines are way more fun to look at than solar arrays. You can visually see when a wind turbine is producing power. Conversely a solar array is boring and just sits there (see the solar section for why this is also a good thing).

Keep checking the turbines. In May of 2014 we had an issue with our two blade Eoltec turbine which shut off and when restarted gave a grinding noise.  We have since lowered and removed the turbine for inspection. The issue was a broken disk which connected the shaft to the generator. The question of why it broke is more interesting.  After close inspection one wire from one of the three phases was burnt and no longer attached (possibly caused by a bad crimp attachment). The turbine then was effectively under load for two phases and freewheeling through the third, thus causing extreme vibrations which broke the disk attachment. Unfortunately the Eoltec company is no longer in business (we tried to pick a good company with staying power but it was not to be). We were able to locate a replacement part and our installer helped us disassemble the turbine and return it to service in the fall of 2014.

In the spring of 2015 the Evance turbine unexpectedly shut down. After further inspection we were able to determine the inverter shut down due to an over voltage situation on the grid side where the grid voltage was higher than the range programed into the inverter, this led to the shutdown. (The inverter monitors the grid electricity so it can match the quality characteristics of the electricity and to enable the system to shut down in a situation when the grid power has an outage). We were able to remedy this by restarting the system and a small adjustment to the inverter configuration.  This took less than one day and required us to call the installer who helped us troubleshoot. In this case the installer did not have to come to the location and we were able to follow his instructions.

SOLAR PHOTOVOLTAIC ARRAY

INSTALLATION:

 Piece of cake but don’t forget the electrical code. Solar PV installation is relatively simple especially with microinverters, yet the balance of the system components like grounding, and wire management are important to meet all electrical code compliance.  Be sure you know what is required for code compliance. This is where an experienced installer can help.  We chose microinverters for the flexibility of monitoring each individual panel. Microinverters can be more expensive than one larger string inverter yet are a good choice when part of the array may be shaded or individual monitoring is desired.

 

SOLAR IS ROBUST: 

 There are plenty of brands of good panels on the market. Many modern silicon solar panels are high quality and are sold by many brands. The brands we chose came from both US and Chinese manufactures. Chinese made panels are common due to great scale up in Chinese production. Consider Chinese panels that come from reputable companies perform similarly to domestic panels. Consider the company and warranty when choosing a panel.   

SOLAR IS BORING (in a good way):

A solar panels best attribute is the fact it has no moving parts. This same attribute also makes it boring. So far outside of human error our boring solar panels have functioned flawlessly for 3.5 years which we cannot say the same for our wind turbines.  A tracking solar array will give more output for the same size system but will add moving parts which have a much higher likelihood of failure. Keeping it simple is the way to go.  We faced our solar array south and tilted at approximately 42 degrees. We have the ability to adjust tilt based on the season and have adjusted them to a higher angle in the winter to take advantage of the lower sun angle in the winter. In order to keep it simple we did not use batteries to store the electricity. Grid tied systems don’t provide backup power but they do cost less and have less maintenance than battery backup systems.


SOLAR IS SCALABLE:

One panel or one hundred just do the math. Our experience with just six panels would translate to 10, 60 or 600 panels.  Only difference being the space required for the array.  Currently in 2015 solar PV systems will cost between $3 and $4 per Watt installed with the lower cost per Watt for larger systems and slightly higher cost for smaller systems. The energy production would scale almost perfectly based on the number of panels. 

SHATTERED SOLAR PANELS:

In May of 2014 two of our six panels had shattered glass.  The glass surface was shattered by what looks like hail stones (The Trina solar panel was rated to withstand a one inch hail stone at 50 miles per hour).  Upon close examination of the data it was determined that there were no storms at the time and date of the damage and possibly a rock thrown from a shredder may have caused the damage.  The broken panels still produced power yet at about half the rate of the unbroken panels.  We would expect the panels would have eventually failed due to corrosion from water infiltration. We replaced the broken panels at a cost of about $200 each including shipping.  We were able to reuse all other components such as microinverters etc. 

CONCLUSIONS:

 

Wind and solar PV are feasible for a farm, business, or residence.  High quality components are available and unfortunately there are also some low quality options available. Do your homework to find good components. Although we tried to select from turbine companies who looked to have longevity, it turned out otherwise. Any future repairs are in jeopardy if we cannot source repair parts. 

The economics of small wind and solar is somewhat more complex. Solar has declined in price in recent years and thus the payback period is considerably lower than small wind. Each individual will have to determine if the economics is right for them.  The goals for each person may also differ, for example a person who values the clean energy may be happy with a longer payback than someone looking at it as an investment. 

Below is the basic economics of our systems. Businesses may also be able to depreciate a system and gain additional savings not calculated here.