California has one of these solar thermal towers. Quite a spectacle as you drive by on the way back from Vegas.
Interestingly this one does not store energy for 24/7 operations like the one in China. As they are both smolten salt based, not sure why
https://en.m.wikipedia.org/wiki/Ivanpah_Solar_Power_Facility
You can have it all with one brokerage in one fund and still be diversified. Suggest reading up on the 3 fund portfolio or boggle head.
S&P 500 is top 500 US companies. Many folks consider that diverse. You can also probably find a US Total Market fund. That will be even more diverse as it will include small and mid size companies in addition to the top 500.
Alternatively, even more diverse would be a Total Market fund. These typically include international companies, and represent the biggest diversification you can get.
No need to worry about Vanguard versus Schwab . The underlying stocks of the fund is what matters.