The California Independent System Operator's (ISO) mission as described on their web page: The ISO manages the flow of electricity across the high-voltage, long-distance power lines that make up 80 percent of California’s and a small part of Nevada’s grid. The nonprofit public benefit corporation keeps power moving to homes and communities.
One would figure this source would offer a realistic view of the California electrical system and how we are doing in terms of renewable sources of power and what the future might need to look like to get to 100% renewable by 2045.
Today's electrical demand isn't all that high due to relatively mild temperatures throughout the major metro areas in California. See the screen capture below:
The lowest demand for power was at 4AM this morning with 21,340 MW. The peak demand hasn't occurred though it is projected to occur in the early evening at 19:45 where demand may reach 32,700. In the screen capture, it reports the highest electrical demand ever occurred on July 24, 2006 when demand reached 50,270 MW during an epic heat wave.
The state is on track to hit the 50% goal by 2030 if today's grid performance is typical. In the screen capture below, it says the grid was receiving 44.4% of its electricity from renewable sources.
Solar is the main source of renewable power (79.1%) in this snapshot.
What do these graphs tell us?
Since I haven't followed the issue, here are the things that strike me:
#1 The high amount of solar power is a pleasant surprise. With so much sunshine in California, it isn't surprising that solar would be an option but I hadn't realized that it represents such a large portion of the electrical supply.
#2 The low amount of wind power is a disappointment. With all the hype about wind and solar, I would have thought the balance between the two would have been closer. As you can see solar has a 16-fold edge over wind at this snapshot. It varies from day-to-day and hour-to-hour but clearly solar far exceeds wind in California.
#3 The supply graph confirms what I have heard, wind power does vary considerably. It peaked at 3011 MW (1:05AM) and fell to 630 MW (12:35). I looked back at a few other days to see if this is pretty typical. Some days wind can get almost to 4000 MW (July 18) and got as low as 412 MW on that same date.
#4 The other incredibly obvious feature of the supply graph is that solar varies from 0 in the dark to 10,000+ MW during the day time and it can stay at that level for a handful of hours during peak sunshine.
#5 On today's screen capture graph, the "imports" reached 16.4% (4473MW). Looking at a few random days in previous months that is not unusual. On some days the imports can reach up to 10,000MW. This highlights one of the major challenges of electrical management: matching supply with demand. From a random look at some other days in the last few months, it seems California is routinely importing some amount of electricity. I wonder if this is a consequence of our reliance on solar? Unlike a natural gas plant or a nuclear plant that you ramp up and down to the amount you want, you can only take an educated guess at how much solar you might get from the various solar farms throughout the state. I would guess the Cal ISO would then try to make up the shortfall by spinning up gas/nuclear plants and if still short, they buy power from suppliers outside of California possibly at higher prices?
#6 There is a small item in the "current renewables" box called "Batteries (charging)." I would imagine on some occasions they can bleed off excess production into battery charging. One wonders how much battery capacity there is in the system right now? In the Today's Supply Outlook page further down (not shown in my screen captures) there is a box describing storage. Periodically power is drawn from storage (positive value) and charging into storage (negative value). A random look at a few days here and there from the past months show those values rarely exceed 100 MW.
UPDATE: According to EIA report "US Batter Storage Market Trends May 2018" Cal ISO has 130 MW of battery storage capacity (p. 5). They project that by 2050, in the USA there will be about ~ 40,000 MW of battery storage (p. 19) with ~ 708 MW as of 2017 (p. 1). They mention in California AB 2514 sets a goal of 1325 MW of storage (p. 19) by 2024.
How do we get to 100% renewable by 2045?
Between electrical efficiency and population growth, will demand for electricity rise in the next few decades?
In the supply screen capture above it says available capacity is 43,055 MW. However, in practice, some percentage of capacity is probably off-line for maintenance and shut-off since expectations of demand might not require that capacity to even be on stand-by.
If today's current demand 28,000 MW is typical (it will get higher later in the day), let's figure by 2045, a typical mid-day demand rises to 42,000 MW, a 50% increase.
UPDATE: Went ahead and did a web search for information about projected growth in electricity usage. According to the Energy Information Agency (EIA) press release "Annual Energy Outlook 2018" on page 17, depending on economic growth rate assumptions, electricity use will rise somewhere between 0.5 to 1.5% per year. If we take the 1.5% per year and project out to 2045, we get to 41,854 MW.
Let's say we have a mix of sources that is 100% renewable as follows during peak daylight hours
80% solar = 33,600 MW
5% wind = 2100 MW
15% everything else = 6300 MW
Today, we have 10,000 MW of solar. Thus, we need three times more solar.
Today, wind is contributing 630 MW so that would require a three-fold increase in wind farms.
Today, we get about 2000 MW from everything else; thus, we need three times more from those sources.
Of course, on a broiling summer day when everyone has their air conditioners running, the demand will be much higher so these three fold estimates are on the low end of what is needed. Cal ISO will want some spare capacity for those high demand situations.
But what about night time?
If the lowest demand at night is 28,000 MW (two-third of daylight), what is the supply mix?
solar = 0 MW
wind = 10,000 MW (if we assume we can get 5x more wind power at night versus the day time?)
everything else = 6300 MW (all the other forms of renewable are fairly steady producers)
deficit = 11,700 MW
Additionally, there is a "shoulder" period of about 1-2 hours in the morning after sunrise and 1-2 hours before sunset when solar power hasn't reached 100% capability.
In the end, there will still need to be 10,000 to 20,000 MW of capacity that can be turned on/off quickly to make up for troughs in solar and wind electrical production.
Battery storage is one way but that is currently at only 100 MW. There will need to be a 100-fold increase just to get to the low end of what is needed.
Thus, will natural gas and nuclear plants be helping pick up the shortfall?
UPDATE: Let's take the lower end assumption of 0.5% growth in electricity per year that yields a demand of 32,036 MW by 2045.
80% solar = 25629 MW
5% wind = 1602 MW
15% everything else = 4805 MW
Need 2.5X more solar, wind, and other sources to match demand with supply.
Night low demand = 21,357 MW (assume 2/3 of day demand)
solar = 0 MW
wind = 8010 MW (if 5x more wind power at night than daytime)
everything else = 4805 MW
deficit = 8542 MW
In the end, there will still need to be 8000 to 16,000 MW of capacity that can be turned on/off quickly to make up for dips in solar and wind electrical production.
