Q: What about solar energy? Can't we use solar for everything?
A: Solar can provide all the energy we need for cars. Solar can provide around 50% of our overall electric needs. However, solar will not work for ships and jets... nor steel or cement. Solar could produce green hydrogen to do the job; however, it would be at the expense of providing electricity to the grid. (also green hydrogen is only a 40% efficient way to store solar power.) Some countries are using wind or nuclear to make the green hydrogen. Some countries are creating their green hydrogen in other countries (eg Germany > Australia) using solar, than importing their green hydrogen (hopefully, in green hydrogen powered ships.)
Q: Is hydrogen really "green" or is that green washing from fossil fuel companies? Essentially as I understand hydrogen is more of a form of energy storage- as the water. Also, I'm intrigued by mechanical batteries for long term terrestrial storage more than chemical batteries but exciting to see what chemistry we can come up with.
A: Green hydrogen that is made from solar or wind is green hydrogen. Natural gas (methane) that is used to make hydrogen is blue hydrogen. There is yet another method for transitioning -- a mix of 80% natural gas (methane) and 20% hydrogen. The importance of all the above is getting from here to then. Most of Europe and the UK (and much of the USA) heat their homes with natural gas. The 80/20 mix can start to be used with the existing infrastructure. Long-term we will need to upgrade the infrastructure to go with pure hydrogen. The reason being -- hydrogen is the smallest atom (it can even leak between copper or steel atoms that make a pipe.) As for batteries, I've been involved with batteries and fuel cells for a long, long time, too. The most efficient alternative batteries are based on membrane technology. My favorite is the membrane based battery that can be 100% efficient and never losses it's ability to hold a charge. There are quite a few other battery types that do not involve mining or exploitation of natural resources. These include underwater bladders that solar electricity pumps up when the sun is out. Then, air is let out to turn turbines when batteries are needed. Another method is buried rocks that are heated up by solar during the sunlight and geothermal energy is used for batteries. The most practical alternative battery that is currently in use is the sand battery. The battery uses low-grade sand and is charged up with heat made from from solar or wind electricity. The sand stores the heat near 932 degrees Fahrenheit.
Q: Things have evolved rapidly in the solar space. 90% reduction in costs in less than a decade. Now we can truly scale this exponentially and power everything relatively cheaply and abundantly, can't we?
A: Yes, solar and battery are coming down in price quickly. But, the problem you seem to be missing is -- we can not power everything with electricity. You can not make cement with electricity. You can not make steel with electricity. A blast furnace requires blast. You can't fly passenger or cargo jets with electricity. You can't power a cargo ship with electricity. The storage size exceeds the vessel. You can't heat Europe, the UK, and the USA on electricity. Neither the grid, the solar resources, nor storage capacity are currently available. We need to think beyond our electricity needs when it comes to solar. That is not our biggest threat. Are largest threats are industry (providing mass consumption fashion and goods emitting that result in greenhouse gases) and land use (eg damage of building dams for hydro, taking down trees to put up solar panels, using bio-fuels that emit more pollution than fossil fuels, etc.) The roles of residential solar and EV transportation are already going good. I'm skeptical we can get people to stop their mass consumption (eg look around). I have more optimism that we can change our land and soil usage. Stop mining 100% Stop drilling 100%. This is obtainable now.