Do Wind and Solar Offset the Use of Fossil Fuels?
Nuclear energy proponent Dr. Gene Nelson, whose Ph.D. is in biological radiation physics, takes issue with my statement that wind energy offsets fossil fuels, and he certainly has a point. He writes:
Dear Craig: I respectfully disagree with your claim that wind energy is offsetting fossil fuel consumption for electric power generation. The fundamental problem is the significant intermittencies associated with wind generation. In order for a grid operator to integrate wind generation into their grid requires that a subset of the fossil-fired generation be operated in “back down mode” or “back off mode.” The problem with fossil-fired generation plants is they require a significant amount of time to heat the boilers to operating temperature. You can observe this yourself in a small scale when you heat a large pan of water to boiling. It takes considerable time. Some power plants require as much as 24 hours to produce power from a “cold start.”
Instead of turning off the fossil-fired plant when the wind is blowing with sufficient velocity, the fuel input is merely “backed off” enough to keep the water employed to create steam to spin the turbines at or near the boiling point. That way, when the wind suddenly diminishes, the power plant may be throttled back up and pick up the load. This mode still requires significant energy inputs from the fossil fuel source. There is only marginal improvement when a bank of batteries is used in some new General Electric power generator designs to supply power for the short interval while the generator is “spinning up.”
Attached find a half-year scatter plot with supporting tabular data showing the significant day-to-day variability of the approximately 80% of California Solar and Wind generation that is managed by the California Independent System Operator (CAL-ISO)
Additional background regarding energy storage is found in the attached two-page cover letter. Note that instead of Helms Pumped Storage being used for 6 hours/day the actual average daily usage for the period from 2003 to 2016 ranged between 12 minutes/day and 68 minutes/day.
I look forward to your response.
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I respond:
Three things:
- The way solar and wind “offset” fossil fuels takes different forms in ISOs (Independent System Operators, aka grid managers) around the country/world,
- The way this happens today is not necessarily the way it will happen next year, let alone a decade hence, and
- As wind and solar scale along with HVDC transmission the issue of intermittency diminishes. Storage solutions will help as well, of course.
This doesn’t strike me as a valid indictment of intermittent resources.
Btw, you’re the man! I just got out of the car, where I was listening to your presentation on “Issues and Ideas” on (our local NPR affiliate) KCBX. You did a fabulous job.
Now, the wind and solar energy can not offset the fossil fuels. But I believe in future, the wind and solar energy will certainly offset the fossil fuels.
Craig,
I’d like to take a different swipe at that.
Dr. Gene Nelson:
First, and most importantly: You seem to be conflating the ideas of “100% elimination” and “reduction”. The two concepts are not the same.
Second, the time that it takes for power plants to cycle up or down depends on the type of plant, and yes does impact the efficiency of the plant and the O&M cost addition to the power provided. Throughout most of the plains states and the wind corridor at large, coal is king. The level ground offers easy and cheap dispatch via train of literally hundreds of millions of tons of coal per year, and most of the states’ power in that region traditional came from coal. But coal power cycles VERY poorly. It takes ~8 hours to really ramp up the boiler and the efficiency drop is truly punishing.. and any significant drop in power needs might require venting – a horrible process in which 0% of the escaped energy is recovered.
So within these regions, as the variable wind farms have become more prevalent; more and more natural gas power has been used to balance that wind energy. The cost of variably-supplied coal power is higher than the cost of variably-supplied natural gas, so most of the fossil balance power used in regions of high wind penetration is going to be natural gas.
Thus, the penetration of wind into the region has forced the dispatch switch from coal to natural gas.
Third: In areas of significant hydropower, dam uprating has allowed hydroelectric dams to cycle slightly… increasing flow during wind lulls and decreasing flow during high winds… and in those regions hydroelectric power can partially or fully balance wind variation. There are also pumped hydropower storage facilities that can serve to constantly balance power quite effectively.
Fourth: With a large distributed grid network (as seen in the plains), the variation in overall wind energy is reduced – as winds may fall in one area and rise in the another… so that the overall wind power generation is more stable. Also within such a large grid, more and more fossil generation is wired in, so that the variation that does occur can be distributed to more and more natural gas power plants. When these plants are running at lower capacity, the turbines are spinning at or near full speed. They just have the magnets moved so that there is less torque opposing the spin, and less energy required to keep the turbine spinning. At such times the units are still operating at or near peak efficiency. If a sudden shift in energy demand is required, the magnets are adjusted so that the torque increases… and the “spinning reserve” in the turbine is gradually released as the turbine speed reduces. This can respond in seconds, and if there are sufficient turbines within the grid, can happen in staged release with more than enough time for some of the natural gas boilers to ramp up while maintaining high efficiency. So not much energy is wasted in such a network responding to variable energy supply.
Taking this into account, a new wind farm built in the Midwest would reduce total fossil generation by nearly the total amount of energy that it produces, and force dispatch switching of some large amount of energy from coal to natural gas.
It both offsets fossil energy and forces more coal off the grid than its total offset. That’s a win/win.
Craig and Glenn,
I think the divergence in opinion between Dr. Gene Nelson and yourselves, is how your determine the objective. .
The objective of providing the most reliable, and economically viable electricity for an industrialized economy, is not the same as providing the least carbon emission free power source.
Since trying to achieve both without compromise is virtually impossible, it become a debate between which objective is the greater priority with advocates for Wind and Solar refusing to accept reality and arguing vainly the impossible can become true.
Even more curious are those advocates opposing coal as a resource while simultaneously opposing fracking, new natural gas fields, natural gas pipelines and nuclear technology !
In reality, most wind and solar renewable energy is only economically viable due to government support in the form of regulatory distortion of the economics, heavy subsidies and other support.
If the only criteria is a reduction in pollution, it could be said that Wind and Solar are successful. (although that’s debatable).
Unfortunately for Wind And Solar advocates, modern industrialized economies are highly competitive. The requirement is power on demand, the source of power must be economically competitive with other industrialized economies.
Pretending a mule is a horse because it’s similar, is ok if the mule can perform all the functions of a horse, but if your mule if required to compete against other horses, it quickly find itself at a disadvantage.
Therein lies the problem. When mule enthusiasts insist governments change the rules in favour of mules, sooner or later the illusion will collapse, taking with it the rest of the economy.
(Btw, I love mules, and own 5 1 🙂 )