[hannob]

The Sahara thing is ultimately just to illustrate that there's no real limit to solar energy (because the upper commenter claimed that nuclear is the only energy that is practically limitless). But of course in practice you'd do the easy things first - that is, build solar on every rooftop. No country is anywhere close to that.

I guess in the future we'll use imported solar for hard to solve problems, e.g. turn it into hydrogen or synthetic fuels (which also makes the transmission loss problem much smaller), while our electricity needs will be served mostly by local wind and solar.

[chrisco255]

There's no solar energy in the Sahara at night. And then as people mentioned, there is energy lost in transmission through resistance in power lines. There's also the fact that not too many of the world's 8 billion people live within serviceable range of the Sahara, assuming you can get past the geopolitical instability in that region to construct and maintain such things. The solar cells would need constant cleaning from dust storms to keep them running at high efficiency.

No, running solar on rooftops isn't the most practical use either. Depending on latitude, weather, cost of solar installation and battery installation, orientation and layout of roof to the sun, the problems with snow, rain, and hail, the lack of solar at night, the fact that none of this generates enough power for those times when you need it most like in the middle of winter in northern climates, etc. Solar and wind will never meet the growing needs of modern economy. Period. It's a pipe dream.

They are great supplemental sources of electricity. They cannot power a first world economy.

[eloff]

Every thread in HN is filled with pessimistic people pointing out how things can't work. It's tiring to read.

Solar and wind absolutely can produce all the energy the world currently needs, using only a tiny fraction of available land area. You could power the whole of the US by 100 square miles of solar panels in the southwest, backed with one square mile of batteries [1]. Clearly it's a hard problem and there are many obstacles to overcome, but just as clearly it's not fundamentally unsolvable.

Long-distance electrical transmission is actually pretty efficient nowadays, so that's not a showstopper either.

Bottom line, optimists are responsible for progress and while many people on HN are content to write comments about how it can't be done, somewhere there's an entrepreneur working hard to make it happen - and the smart money is on them, collectively, over the long-term - and thank goodness for that!

[1] http://www.digitaljournal.com/tech-and-science/technology/we...

[belorn]

You can absolutely power the whole of the US by 100 square miles of solar panels in the southwest. The cost would be to build the solar panels, the square mile of batteries, replace all the power lines in the US with cables that can handle very high voltage (twice or more than what current power transmission cables can handle) needed for long-distance, and replace all the power stations connected to those so that can take that high voltage.

It not impossible at all, we have the technology, it just money. Replacing 200,000 miles of cables, with a price tag of a few millions per mile is a project the US could undertake. Replacing all the power station to handle the very high voltage is similarly possible.

When choosing between the many alternatives it is something which should be calculated next to the cost of building nuclear plants in a distrusted pattern, and the long term cost of nuclear waste that such plan would entail. If entrepreneurs could invent power transmission cables and power stations that can manage millions of volts and cost a fraction of existing methods to install would make a centralized place for power generation a much more attractive option.

[cameldrv]

It's a lot more than 100 square miles. Here's an NREL report on this exact question: https://www.nrel.gov/docs/fy13osti/56290.pdf If you extrapolate (see analysis here: https://www.freeingenergy.com/how-much-solar-would-it-take-t...), you get 21,250 square miles. Elon musk says 100 miles x 100 miles, which is 10,000 square miles. Both of those figures are just for current electricity demand, so if we electrified all transportation and industry, we're looking at maybe 60,000 square miles.

60,000 square miles is half of Arizona. Now suppose we want to scale up energy consumption in the U.S. by a factor of 100. At that point, you're at twice the land area of the U.S. Even at current consumption, the amount of ecological damage you're causing by covering half of Arizona with solar panels is huge.

On the other hand, if you wanted to replace all U.S. energy production with nuclear, you'd need about 7-10x more than we have today, or about 1000 reactors. The land area for these reactors is about 700 square miles, or about 25x25 miles. If we wanted to scale it up by a factor of 100, we'd be looking at half of Arizona again.

[eloff]

Sorry, it's 10,000 square miles in the article I linked. I can't edit my post anymore, but my point stands.

Energy consumption is actually dropping in the US currently, but I don't expect that trend to continue indefinitely, eventually we will get to 100x energy usage. And you're right, at that point solar wouldn't cut it.

But that's a far cry from your original post saying it won't work for a developed nation, when it clearly can work for the world's richest and most energy intensive nation.

As for the very far future when solar won't cut it? I'm sure we'll use a lot of nuclear, and by then probably a lot of nuclear fusion. Or maybe we won't have those crazy energy requirements because we've moved most industry off the planet like per Jeff Bezos' vision of the future. It's enough to get ourselves sorted in the present, so we can have a bright future, and solar and wind power can help us achieve that. There's no reason nuclear can't be a part of that picture, but they have a hard challenge ahead because current nuclear is not competitive cost wise with renewables plus energy storage.