Picking up on our course review, we talked about options for grid integration, from approving connections to neighboring areas to change in the market structures. But one major, not the only one significant tool is storage. As we've talked about in the class again, for our review, there are lots of different storage technologies, but two are emerging as dominant, pumped hydro and batteries. If you look at what's actually installed in the ground now it's almost all pumped hydro, well over 90 percent of global storage capacity right now is in the form of pumped hydro. However, there's a lot of interest and rapid growth in battery storage. There are a variety of battery technologies. But what's clear over the last 5-10 years, is one technology, lithium ion is dominating the global storage market. There are a variety of other technologies, they may have a role going forward, but if you look again at market share, lithium ion is emerging as a dominant or need [inaudible] technology. Why is that? Essentially, the same reason that PV and wind are taking off because it's costs have come down so dramatically. Shown here are the cost of lithium ion battery packs. These cost data are for battery electric vehicles, but the fundamental technology is the same. As we talked about, a study that was published in 2015 showed the decrease in costs over time, showed forecasts of where the costs would go. Similar showed PV, the reception was that those forecasts were too rosy, that was not going to happen. Costs would remain high, but in fact, the actual costs are significantly below what the forecast said. Lithium ion batteries, similar storage as solar PV, the cost dropped much more quickly, much more dramatically than almost anybody expected. Where are we with this? Well, now in early 2020, batteries are starting to play a role in electricity systems, although that role currently is quite small. Here's the example of California showing battery charge and discharge over a random day in late 2020, not really 2021. In late 2020, batteries were playing a small role. Now, you can see it goes up and down, but notice the scale is plus or minus 200 megawatts. Keep in mind the California system is 40,000 megawatts. Batteries, again are not playing a major role, but they are seeing rapid growth. What are some other tools besides storage that can be used to affect or help integration of variable renewables. Demand-side management is one. Instead of accepting that demand goes up and down, you have to meet it. You can think about change in demand. We talked about the example of Hawaii, where the utility will install a switch on electric water heaters. For example, if the utility is short, electricity does not have enough, they can shut off the water heater, and most people would not notice because the temperature change would be fairly small. As shown here, there are 15 megawatts of what's called controllable peak demand. As we talked about and we had to interview some experts, this thinking of demand side management, changing demand, also called demand response, is just starting to be used to help with grid integration variable neural, but it's a potentially very powerful tool. Another example of thinking about demand side would be pricing. We have an example of a retell logistic provider in California who has four electric vehicles, inexpensive electricity from midnight to 6:00 AM, and expensive electricity from 4:00-9:00 PM, which is one that ramp is going up. You can actually change demand, which is just another way of thinking about another tool for integrating variable renewables. Of course, we then moved on to talk about structure of the market or the industry, which is a confusing structure. Well, we talked about how utilities are organized and the old fashioned model of the traditionally regulated monopoly, where there's one company that does generation and transmission and distribution. Then a modified version of that model, essentially, where there is one company or organization that does all these things, except private sector can play a role via something called an independent power producer. We had model two, and that captures, for example, the current structure in some African countries that we talked about in the course. Then a very different model that is emerging where there's wholesale competition. There is no one single entity responsible for generation where the wholesale market is competitive. EU rules, noted here, require member countries to allow for some competition. About two-thirds of electricity in the US is sold in these competitive retail markets. That's a summary of the entire course. You can get a sense of where renewable power is and how it's changing so quickly. There are tremendous opportunity worldwide.
