It has become increasingly clear that renewable energy forms, especially solar and wind turbines, are and will be important sources of electricity. Along with this fact, some cities and even a few states have declared they will become 100 percent renewable. What that means is they will somehow obtain all their annual electricity, measured in MWh, from renewable sources. It should be noted that California (a large and rather stupid state on the West coast of the United States), has already sourced more than 27 percent of all power sold in the state in 2015 from renewable sources. Not all of that was solar and wind, however, and not all of that was generated in-state, either. California counts renewable energy in what is perhaps a unique way: large hydroelectric power is not part of their counting. If large hydroelectric sources were included, California would be well past 40 percent for the year.
A rather interesting discussion along these lines occurred several days ago (and may still be exchanging comments) at Dr. Judith Curry's blog Climate Etc. (see link) The post was written by an anonymous author, who appears to be involved in some way with the PJM grid, the Pennsylvania-New Jersey-Maryland grid that serves multiple states along the East coast and Mid-West. I read the post with some interest, then entered the discussion with a few comments. Rather than replay all that here, this post will discuss some aspects of renewable power production and integration into existing grids.
As background, a few comparisons between the California grid and PJM. California grid is known by the name CAISO, for California Independent System Operator. (see link to CAISO website)
PJM and CA have significant differences, and therefore will have different problems. The most obvious differences are in the thermal and nuclear portions of the generation mix: CA has but one nuclear plant of 2200 MW running, zero coal plants, and a great number of efficient and agile gas-fired plants. PJM, as I understand it, has several nuclear plants, many coal-fired plants, and also some gas-fired plants. A notable gas-fired CCGT plant will soon be brought online in Lordstown, OH for PJM to help cope with wind power changes. (see link to SLB article on this plant)
Next, renewables in CA are from approximately 11,000 MW grid-scale solar, and 5000 MW of wind. PJM, again by my reading, has also 5000 MW of wind and very little solar at grid scale.
It also must be noted that the CA grid is smaller in size, measured in peak load, annual generation, and generating capacity compared to PJM.
Population – 65 million PJM; 38 million CAISO (ratio 1.71)
• Generating capacity – 176,569 megawatts PJM; 70,900 CAISO (ratio 2.48)
• Peak demand – 165,492 megawatts PJM; 46,000 CAISO (ratio 3.59)
• Annual energy delivery – more than 792 million megawatt-hours PJM; approximately 295 million for CAISO (ratio 2.68)
(the differences are almost entirely due to climate, mild in CA and typical US Northeast – aka brutal winters – in PJM region)
• Nuclear Power installed - 30,000 megawatts PJM; 2,200 in CAISO (ratio 15)
• Nuclear as percent of all capacity - 17 pct PJM; 2.8 pct CAISO (ratio 5.9)
The problems for PJM will stem from much higher nuclear as a percent of total annual generation; as has been noted, nuclear does not reduce load in the US. It appears that PJM has approximately 30 GW of nuclear installed, compared to 2.2 GW nuclear in CA. However, PJM is surely acutely aware that the nuclear plants are closing in great numbers, as they reach the 40 year age mark. The next 10 years will see many if not most of the nuclear plants in PJM territory close. CA will close its final nuclear plant in the early 2020s.
Also, PJM is facing offshore wind power generation as a soon-to-be reality, with Maryland already announcing projects of approximately 500 MW. That is small as a percent of the PJM market, but will likely grow quickly.
Another significant difference in the PJM versus California situation is that PJM has many states integrated into the grid, compared to just one state for CAISO. The importance of this is that PJM member states each have a renewable goal, and those are not all the same. California has just the one state with a renewable goal, however, that goal keeps changing.
Yet another important difference is the resource availability - how much solar energy hits the ground, and how much wind energy exists. On this, the two grids are just about the opposite. California has what is likely the best solar energy resources of any large state in the country. Arizona has comparable sunshine, but a much smaller population. PJM has much less solar energy due to the higher latitude and much more cloudy conditions. Wind energy is small in California - and essentially already tapped out. PJM states have substantial wind resources that have yet to be harvested.
Now, to the heart of the matter: can any location, city, or state actually obtain 100 percent of its electricity on an annual basis from renewable energy? The answer is Yes, of course it can. The only questions are how much will the grid be modified, and how much will the electricity price change, if any.
The Climate Etc article referenced above referenced a PJM publication that claims a hard limit exists for a grid, with 20 percent annual production from wind and solar. That may very well be true for PJM, with all the nuclear and coal-fired plants on that grid. But, in California, that is not a problem at all. Some grid-scale storage is required, which California already has. More storage will be installed as more solar PV production is installed, keeping the grid safe, reliable, and cost-effective.
SLB has previous articles on grid-scale storage, with example technologies including batteries, ARES rail-based gravity trains, pumped storage hydroelectric, and others.
As to achieving 100 percent renewables, that actually will not occur as long as large hydroelectric generation is not counted as a renewable. The US average for large hydroelectric generation is approximately 7 to 8 percent on an annual basis of total electricity produced. Various states have different percentages, with Washington State the highest due to the Columbia River and the several hydroelectric dams there. (for numbers, the US produces approximately 4,000 million MWh each year, of which large hydroelectric dams produce approximately 250 to 300 million MWh each year - source EIA Electric Power Monthly Table 1.1).
Even if one did count large hydroelectric as a renewable, the near future will not allow 100 percent renewables due to the great number of nuclear power plants (99 of them, although the numbers keep falling as more and more give up and shut down to stop their huge economic losses). On average, nuclear power produces approximately 18 percent of the US' electricity (recent decade numbers range from 769 to 806 million MWh per year; same EIA source as for hydroelectric).
Next, coal-fired power plants still produce the lion's share of US electricity, although that is declining rapidly with environmental regulations now in place. Coal-based electricity was approximately 1,200 million MWh per year in 2016, which is approximately 30 percent of the US total of 4,000 million MWh, same source as for nuclear and hydroelectric.
Therefore, on a national average, the US presently stands at 30 percent coal, 18 percent nuclear, and 8 percent hydroelectric, which combined provide 56 percent. Even with nuclear plants closing, as most of them will certainly do within 15 years, and with coal-fired plants shutting down as their economic mines are exhausted and shut down, again within 20 years, the US still has 8 to 10 percent hydroelectric, depending on the annual rainfall.
Concluding, the post title asks Is 100 Percent Renewable Energy a Good Thing? The answer must be, yes, but only on a local basis, as engineers take adequate care to ensure grid safety, reliability, and cost effectiveness. As noted here and elsewhere, California has not had price increases due to a greater and greater share of wind and solar generation. Indeed, CA prices have barely kept up with inflation. (see link to SLB articles on this topic). The grid has also remained quite stable and reliable.
For many policy reasons, wind, solar, and other renewables are a very good thing. Among the many reasons for this are job creation, absolutely free energy that has no foreign implications, inexhaustible energy, pollution-free energy, industries expanding into solar production and wind turbines, other industries racing to produce economically attractive grid-scale storage systems, and innovations in grid system technology and controls.
Can PJM meet their renewable energy targets (approximately 25 percent by 2025), or will they have insurmountable difficulties? The answer there is no, not with all those nuclear power plants on their grid, and the many coal-fired plants. It is quite expensive and time-consuming to shut off a large coal-fired power plant, then start it back up again. Nuclear plants, of course, simply refuse to do that, citing safety concerns. So, with nuclear plants on PJM system stubbornly running all-out, and coal-fired plants losing money if they cycle on and off, PJM has some daunting challenges.
Good luck to the engineers and planners on the PJM grid.
It will be quite interesting to observe and report on their progress in meeting the 25 percent renewables mandates, in light of the PJM study that says 20 percent is an absolute hard limit.
UPDATE 5/21/2017: With 100 percent renewables on a national level clearly impossible, (hydroelectric will run for the foreseeable future), how then does a city or state intend to achieve 100 percent?
The City of San Diego (again, in loony California), with a population of approximately 1.4 million, has a Climate Action Plan (2015) that calls for 100 percent renewable electricity by the year 2035. They gave themselves a full 20 years to accomplish this, being such optimists. How does this work, in San Diego's version? The answer lies in a clever trick of buying electricity from a designated generator, but not from all the others that are also on the grid. San Diego would identify solar, wind, and other renewable-energy generators and claim to purchase power only from them. The problem occurs when the wind does not blow and the sun does not shine. Wind is quite erratic in California, so on nights when the wind is barely stirring, how would San Diego find electricity to purchase?
One answer is grid-scale storage; another is small-scale home-based electricity storage; another is time-shifting demand for electric vehicle charging; yet another (remote possibility) is long-distance power imports.
Grid-scale storage already occurs in California (and other states) via pumped storage hydroelectric, massive batteries, and a rail-based gravity storage system is under construction on the California-Nevada border near Pahrump.
Small-scale home-based storage is already available from several vendors including Tesla.
A favored scheme by many renewable advocates is using millions of EV (electric vehicles) as grid loads while the batteries are charged up during sunny days or windy nights. Then, the cars are plugged into the home where power can be supplied by the car's batteries into the home to run the big screen TV and DVD player, the lights, charge the cell phones, and even run the refrigerator. One must wonder just exactly how big that car's batteries must be to achieve all that. Another consideration is, if the car is running the house at night, how will the car be able to travel the next morning to the workplace?
The very long-distance importing power is an interesting scheme. California has already implemented a version of this, both importing and exporting power, to help balance the grid as more and more solar power plants are brought online. The term is regional integration, or regional energy market. see link to CAISO presentation from 2016. The basic idea is to integrate several states into a regional energy grid, much as PJM grid has done on the East coast, MISO does in the Mid-West see link, and others. California can no longer be an island, in the electrical grid sense. With multiple states on a common grid, the hope is that the wind will always be blowing at some location, providing power that can be exported to users that are becalmed. The problem with this, of course, is that on a day with strong wind over the entire region, far too much wind power would be produced. As that happens, grid-scale storage would be needed to absorb the production. --- end update
Roger E. Sowell, Esq.
Marina del Rey, California
copyright (c) 2017 by Roger Sowell - all rights reserved
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