Technical Corner

Replies to This Discussion

Permalink Reply by Walter H Rose on January 26, 2010 at 11:48am

High penetration is definitely the way to go but it's not without technical challenges. Wind varies in intensity by time of day, season, and with the weather. It does not always blow at a constant rate; it can be gusty. The demand for electricity, while it varies somewhat by day and by season, is much more constant than the wind; the electricity provided by a system must reflect this fact. As you move from lower to higher penetration systems the need for additional controls, thermal dump loads, battery (or some other type) storage, and other accessories increases dramatically. The additional hardware required for higher penetration does not generate electricity; it adds to the cost of power provided by the system.

In answer to the residential heat question, I mention Thermal Dump Loads above. When the amount of power produced by the wind exceeds the size of the load something MUST be done with the excess power. One solution for higher penetration systems is to attach a bank of "resistors" or electric heaters, which can be quickly switched on and off as the wind comes and goes. Typically heat from the resistors is used to heat a large tank of water which is then circulated to surrounding structures and used for heating. Electricity dumped to the thermal load is typically billed at a highly discounted rate making that type of electric heating competitive (or possibly even less expensive) than diesel fired solutions.

Battery systems are expensive, especially in rural Alaska where shipping costs can be very high. Lead Acid batteries are heavy; they are also a durable and reliable proven technology. Lithium Ion batteries are lighter but much more expensive. To date their use has been limited to automobile applications. The absence of any safe, reliable, durable, and affordable storage system is one of the key barriers to high penetration wind today. Many people are working on solving the problem; the one who solves it might go down in history.

Permalink Reply by Alan Fetters on February 10, 2010 at 8:23am

We are working on a new diesel plant with a large electric boiler for Unalakleet. a We logged on the the wind site yesterday afternoon. 6 Northwind 100's onsite, 4 online, producing nearly 400kW to the grid! At that moment probably nearly 50% penetration. Typical grid demand is 600 to 1000kW. No live data available on power quality or the grid. Of the two turbines down, one has electronic control board issues and the other a over torque issue. Noticed genaric warning messages poping up on the running turbines, guessing over torque since they where running near their peak?

Permalink Reply by Ian Graham on March 6, 2010 at 11:42am

Have you looked into the SEL syncrophasor application? It could be benefitial to track power quality real time, or depending on the power meter you are using could be integrated with an RTU control. What type of SCADA system is the system using? I am aware of the N100 system but what about the balance of your system? Very intereted in the electrical boiler you mentioned what is the model you are working with, again an RTU interface is what we have been looking at for thermal & electrical load control.

In Nome we are moving to tracking both frequency stability and power quality real time, with induction machines there are modifications you an do on the power delivery side but not as much room to work as the syncronous generator application.

On the errors you are getting from the turbines are the accelerometers firing in high winds? It could be a miss calculation in the accel algorithum. (just fixed one in a V47 in boston MA) Perhaps something to look at.

Where are ya based out of? Next time in Nome i would love to make a detor down to Unakleet.

Good stuff.
Ian

Alan Fetters said:

We are working on a new diesel plant with a large electric boiler for Unalakleet. a We logged on the the wind site yesterday afternoon. 6 Northwind 100's onsite, 4 online, producing nearly 400kW to the grid! At that moment probably nearly 50% penetration. Typical grid demand is 600 to 1000kW. No live data available on power quality or the grid. Of the two turbines down, one has electronic control board issues and the other a over torque issue. Noticed genaric warning messages poping up on the running turbines, guessing over torque since they where running near their peak?