Welcome back. In the next few videos, we're going to read, summarizing, and reviewing the entire course. It will be new material, but it'll be all put together concisely, pretty quick tour through the entire course. It's worth spending time to go through this review because to some extent, these concepts and ideas are new to you, it's going to help cement your understanding to hear it a second time, but it's going to be quick. To review at the beginning of the course, we talked about recent very dramatic trends and energy use in many countries. For example, data shown here from the UK shows in the electricity side, starting about 2005 dramatic change. Notice how fossil fuels have dropped over 50 percent in this time period from about 2017- 2019 in terms of electricity supply fuel, while renewables increased fourfold. That we also saw data from the US showing a similar pattern where coal consumption is felling very quickly, replaced in part with natural gas, but in part with renewables. Of course, the story varies by country, but in general, we're seeing a global shift towards renewables, pretty dramatic in the power or electricity sector. As this graph shows, the percent of new electricity. That is, if you think about new power plants built every year, right now or in 2019, 75 percent of net additions, essentially new power plants are renewable, and almost all of that is wind and solar PV and that number's up from 40 percent in 2009. Renewables are dominating new power plant construction worldwide. Where are we now? Well, renewables account for roughly 18 percent of the world's energy. A large part of that is what's called traditional biomass, that is people using wood scraps, agricultural waste products and things like that for open cooking and heating. Eleven percent is what are called modern renewables, which is a mix of hydro, biomass, wind, and solar. If we focus on electricity, it's a slightly different pattern, where renewable supply just over a quarter of total world's electricity as of 2019. A large part of that as hydro, but there are other pieces, wind, solar PV, and so on. Those small as percentages are growing very rapidly. That's where we are now. What's next? Well, to remind you how we restructured our discussion of renewable energy futures, we laid out four major areas. The energy scenarios, forecasts, where we looked at model results from specific organizations, and we focused on two scenarios, essentially businesses usual, meaning what if we don't do anything differently, what path that we currently on and then a separate climate stabilization path. What would it take to stabilize the climate? We then focused on technologies, renewable energy technologies, looking at current status and future possibilities, and we looked in-depth at five specific technologies. We then turn to enabling technologies, which are technologies which support or promote renewables but aren't by themselves renewable technologies, we looked at three in-depth, and then we focused on emerging issues in renewable energy, what is becoming important and we looked at handful seven specific emerging issues. Let's do a quick summary of all that material. When we started our energy scenarios in the forecasting discussion. We started with two sayings. It is difficult to make predictions especially about the future. Obviously, a bit tongue and cheek, but emphasizing the idea of the uncertainty of predictions and similarly, there are no facts about the future, so it's all speculation, but that doesn't mean it doesn't work doing, we can make informed guesses. We can essentially bracket the possibilities. We can think about where things are likely and which are unlikely, so it's definitely worth considering, assessing, analyzing trends and looking at what futures are likely, but maintaining a sense of humility about that understanding that we never really know. That said, what are the energy scenarios tell us? Well, we looked at three specific models. One by the International Energy Agency, IEA, one by US specific effort by the Energy Information Administration, and then the greatest detail at a scenario modeling exercise by the International Renewable Energy Agency. The details vary, the geographic coverage, the assumptions, but there are some universal findings in essence, that renewables will see large global growth, particularly in the power sector. There's universal agreement on that, and most of that will be in wind and solar PV. Every model, every exercise, every scenario pretty much shows that we'll be building a lot of wind and solar PV in the future worldwide. However, the data are also quite clear that as the current plans and policies, what government's policies they have in place, what plans they have in the sense of firm plans that they see realizing the short-term, is not sufficient, to achieve climate stabilization, is not sufficient to meet aggressive CO_2 reduction goals. The path we're currently on is not the path we need to be on to achieve climate stabilization. We'll take a quick break here and jump, come back and talk about the technologies themselves
