Dear RG researchers,
As you know, the power output of wind turbines is stochastic and thus it may occasionally be more than the local load. I think this is a controversial issue in the isolated power networks such as micro grids.
In practice, what are the electrical equipment (as virtual loads) for curtailing the surplus power of non-dispatchable Renewable Energy Resources? Does it need Power Electronic based devices or something like damping/dummy load is used?
Any help would be much appreciated.
Regards,
Morteza Shabanzadeh
Dear Morteza,
You have raised an important question. The well-being of the network is very crucial, and that is why something has to be done if the effect of a grid-connected renewable energy generation poses a threat to the power system. Also, in off-grid situation, you don't want to curtail energy generation. The reason is that an off-grid generation is localised (designed to suit a particular load), the cost will also be taken into consideration. We are encouraging the maximization of renewable energy generation, rather than curtailing it. Dedicated energy management and control system could help manage the generation and demand (this is a combination of energy storage and control systems). You may wish to have a look at this publication " REVIEW OF ENERGY STORAGE TECHNOLOGIES FOR SUSTAINABLE POWER NETWORKS"
http://authors.elsevier.com/a/1Pbpg7tDQ8sDv4
if you need a copy, you can contact:
Daniel
Apology, this is the link with Apple wind energy curtailment
http://iphone.appleinsider.com/articles/12/12/27/apples-wind-turbine-technology-uses-heat-not-kinetic-energy-to-generate-electricity
Dear Gerro,
Many thanks for your help. However, it seems a new technology which is introduced by Apple. What about the traditional methods for curtailing online the surplus wind power?
Best,
Morteza
Dear Morteza,
energy storage is a valid option to avoid curtailing the excess wind energy in a stand-alone application. Currently, different energy storage devices are available (i.e.: batteries, ultracapacitors, electrolyzers...) Using energy storage and an adequate control strategy, there is no need to curtail the wind power surplus. Such wind/storage hybrid systems allow a more flexible energy management to supply the grid (or microgrid) demand, also achieving higher efficiency, since no excess energy is curtailed (= wasted).
I hope this answer will help you. If you are interested in this topic, there are plenty of papers which address this issue thoroughly.
Best regards.
Here is an interesting project - aiming at storage of energy in underground water tank:
http://godevelopment.dk/
A trade-off analysis between storage and curtailment should be in place to decide. I suppose the curtailment can be achieved via torque set point signal sent to the turbine control system.
Dear Abubakar,
You are absolutely right. Using wind turbine control systems to curtail surplus energy can be much easier and cheaper than energy storage devices.
Regards,
Morteza
Dear Morteza,
You have raised an important question. The well-being of the network is very crucial, and that is why something has to be done if the effect of a grid-connected renewable energy generation poses a threat to the power system. Also, in off-grid situation, you don't want to curtail energy generation. The reason is that an off-grid generation is localised (designed to suit a particular load), the cost will also be taken into consideration. We are encouraging the maximization of renewable energy generation, rather than curtailing it. Dedicated energy management and control system could help manage the generation and demand (this is a combination of energy storage and control systems). You may wish to have a look at this publication " REVIEW OF ENERGY STORAGE TECHNOLOGIES FOR SUSTAINABLE POWER NETWORKS"
http://authors.elsevier.com/a/1Pbpg7tDQ8sDv4
if you need a copy, you can contact:
Daniel
Maybe this paper can give you some clue about it.
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6895531
Recently, I found out that Power-to-Gas (PtG) facilities, as a new technology, can effectively convert the surplus of renewable energy into natural gas that can be potentially stored, transported, and reused via the existing natural gas infrastructure!
It means that, in near future, the renewable energy curtailment can not be considered as a 'wasted energy' anymore!
Hi, with variable speed wind turbines, you can control the conversion efficiency, thus power output, by acting on the rotational speed of the blades (through the tip-speed ratio). It is the same principle which is used for implementing the maximum power point tracking.
Regards
Dear Fabrizio,
In the case of an individual wind power plant, do you know how much energy curtailment can be possible using the tip-speed ratio? (I mean, with respect to its nominal capacity or in percent (%)). I also would like to know its typical 'response time'.
However, I think this capability is very limited in practice and that is the reason why we call such power plants 'non-dispatchable'.
Hi Morteza,
I don’t have practical experience for wind turbines, but, for instance, with PV plants (where similarly to wind, you need to track the maximum power point, but on the the i-v characteristic), setpoints are typically achieved within few seconds and you can control power output from the upper generation bound to a few hundreds watt (for kW class plants). For variable speed wind turbines, speed is typically controlled to achieve MPPT, but I imagine this is a slower process as it entails changing the rotational speed of the shaft.
While there is a lower bound for the generation output for this kind of plants (that you can achieve by curtailing), the upper bound is a stochastic quantity, that you can’t really dispatch, and that’s why we call it nondispatchable generation.
Hi Morteza Shabanzadeh,
There is an anemometer on the top of the wind mill which can tell the wind velocity. The plant controller can calculate the maximum power possible by that turbine with the given wind velocity. By controlling pitch and yaw, the curtailment is possible between the maximum and minimum possible power outputs of the turbine. Any how, in a network with low RES penetration, to harvest maximum possible free energy, MPPT is used, and the adjustment are done with the other fossil based generators, where you have the luxury for control. As the RES penetration is increasing, to avoid this short term control adjustment, local storage is proposed (Hybrid wind park) BR Venkat.
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