I need a Graph Showing Electrical Generation by Source over time for a 24 hour day.

[NYC_SKP]

(thanks in advance for any help you can provide)

I'm trying to find a graphic for a graph for a 24 hour period of time that indicates electrical generation by each source for CA.

If it's for a different state, it would be better than nothing.

Something like this, but broken down by source, NG, Nuke, Wind, Solar, Coal....

And it has to have a zero base line on the y-axis...



http://www.caiso.com/outlook/outlook.html

HERE is an example of the type of graph, but with different data, that I need.

[vincna]

1. There is too much day to day variability...

for a daily graph to be meaningful. For one thing, it would depend on the time of year - simple cycle gas turbine peakers generally only run in the summer (some parts of the country have a winter peak, so there are exceptions). Weekday or weekend? Weekend loads are generally much lighter. Is it hot out? You will have more gas fired generation on a hot day. Is it windy and/or sunny? Renewables are pricetakers and will put as much power on the grid as they can, irrespective of dispatch.

Some generalizations:
The coal fired units and the nukes are base loaded, meaning they run 24/7. Mid-merit plants, such as combined cycle plants will operate for 12 - 14 hours per day on weekdays. I don't have a lot of experience with hydro (not too much of it in the northeast), but I suspect that it runs somewhat like mid-merit, unless there is a lot of water or very little water, in which case adjustments are made: more water = base load, less water = minimum flow except at peak hours. Hydro's generally have minimum flows that must be maintained, so they are usually generating some power. The renewables are all over the place depending on the weather and the ISO will balance the system with the peaking units, usually 4 -5 hours per day in the summer.

I've been in the electric power business for 26 years and I don't think I've ever seen a daily graph. Why don't you get some graphs for the overall system load and allocate the it using the guidelines I described? Do it for different times of the year.

[NYC_SKP]

2. Absolutely, time of year matters, but...

I thought one might be available that is either for a peak summer day or for a "typical day" using averages from a given year.

And I realize it would look different for each electric utility provider and for each state.

I like your suggestion and I'll probably have to create one using data from PG&E or the California System Operator.

Thanks!

I need to understand for myself and for people I work with how base load is met and how different sources come into play to meet peak demand.

A graphic as I describe would be great for that, wouldn't it?

:P

[vincna]

3. I don't have any experience with California, but...

it's a competitive market and they all work pretty much the same. I'll describe PJM which serves a large portion of the mid-Atlantic region. For each hour of the day, generators submit a bid that is essentially that generators price to supply a certain amount of power to the grid. The bid would include a lot of parameters: $/MWH, Start Charge. minimum run time, ramp rates, minimum time between shutdown and next start, etc. With this information, the system operator looks at the estimated load for the next day and schedules the dispatch in order of price with the lowest cost bids being scheduled first. This is done the day before the generation is needed and the system operator tells the generators their schedule for the following day. In practice, the system operator dispatches in real time and turns units on and off to meet load as the load changes. but price is still the main criterion.

Base load units like coal plants or nukes can't be run as dispatchable plants because it takes a day or two to start one from a cold, shutdown state. For that reason, base load units bid very low, sometimes zero or even a negative number to insure that they stay online 24/7. Combined cycles can generally start up in about three hours and simple cycle plants can be at full load in 20 or 30 minutes. These plants will bid a higher price.

I've simplified the process - it's actually a little more complicated than this. The basic principle is that the system operator schedules the generation to insure that lowest cost generation is dispatched before higher cost units.

[NYC_SKP]

4. Very helpful, thank you.

Despite the fact that every day looks different from the next, a graphic would be a good teaching tool.

[kristopher]

5. One more point to add

The final price all accepted bids receive is set by the last accepted bid. For example suppose the system operator needs 250MW and someone bids 100MM at an extremely low price to ensure their bid is accepted, but since there is more electricity needed the system operator will continue to accept bids until they have the 250MW covered. Whatever the last accepted bid is sets the actual price that all accepted bidders receive.

vincna can correct me if this is wrong, but I believe that most coal is sold through the use of long term contracts which ensures maximum utilization at least cost.

[happyslug]

6. Watch Hydro, two problems when it comes ot calculating its "value"

First, Hydro is the easiest to turn on and off, thus is generally kept back for peak use periods (Natural Gas is the second easiest to start and also tend to be kept back for peak use periods). Now, Hydro power based on a river will always produce some constant flow and thus always some base energy, but most lakes behind Hydro Dams have enough capacity to hold the water till needed so this is rarely a problem (It does raise its head every so often, especially during droughts but overall not a major concern).

The Second problem is several locations in the US, during off Peak hours, excess power from base units are used to pump water uphill behind hydro dams, then the water is used to power the hydro dam during any subsequent peak period. Is this power really hydro powered or based load? Viewing it directly it is Hydro, but looking at HOW the water was able to be used it is base loaded (Whatever is the base load power generation source in that area).

A separate set of problems with Hydro electricity, at the present time, is that most locks and dams built on the tributaries of the Mississippi have no electric Generation capacity. The Corp of Engineers took over those locks and dams in the late 1800s before electricity came into wide spread use and thus were never given the authority to make such locks and dams electric generators at the same time. The main purpose of the dams was NOT to keep water back to prevent flooding or even later Electrical power, but to keep the water level up so Barges can operate on the rivers 365 days a year instead of about 180 days a normal flowing river permits (The Lower Mississippi is the big exception to this rule, but it has extensive locks and dams on the Upper Mississippi, Ohio, Missouri and Red Rivers (And more locks and dams on other Tributaries to those four rivers in addition to the lower Mississippi itself). Flooding and electrical power generation was done with the large Dams up river from where Barges generally traveled. No River Traffic permitted Dams without locks, and such dams could be made very large, permitting them to hold a tremendous amount of water for later use.

AS to the Locks and Dams, in the 1970s the Corp was given the power to make these produce hydro electrical power but had to "share" the duty with whatever municipality was on River AND considered under state law adjacent to the lock and dam. Some municipalities took this up as an opportunity to raise revenue, the biggest problem was one or two municipalities found it was more profitable to take up the option AND then never go forward with the conversion (Clairton in the Pittsburgh Area was the worse case of this, opting using Pennsylvania Law to take options on ALL the Locks and Dams in Pennsylvania in the Pittsburgh District of the Corp of Engineers, thus killing any conversion of those lock and dams to this day, I believe Duquesne Light was behind this but can NOT find any evidence, so it might just be Clairton, a depressed community, just trying to make money but also possible some underhanded deal was involved).

Please Note the above Law on the Corp of Engineers affects Lock and dams NOT Dams built to control flooding. The former is just to keep River flow steady so that barges can use the rivers 365 days a year, the later generally STOP any use of the River up stream of the Dam, but contain a huge amount of water and thus the main source of Hydro Power in the US Today.

One last Comment, one company has claims that using modern technology it can use the power of flowing rivers to produce electrical power. It has proposed building its generators between St Louis and New Orleans deep in the Mississippi River for that purpose. Now this would be a base load system since it will generate power all day long at the same rate. It could NOT keep any water back for later use. If such electrical systems are built and harm to fish and animals can be kept to a minimum (and that appears to be the case in such system), this may be a whole new source of base electrical production. The only problem with it, is that it would be a base electrical source NOT a peak source.