Some energy is captured by plants, electricity can be stored by pumped hydro, CSP can store heat , most energy demand is in the daytime.
The infrastructure is beginning to be built now, we don't need solar today, we can manage for next 20 years using wind, hydro, nuclear and FF.

What infrastructure being built? Where and how much? Please provide data here on TOD. Or perhaps you just think it is - based on anecdotes. No significant potential exists in pumped hydro (it has been discussed here on TOD). The infrastructure required for transporting and storage of significant wind and/or solar component in the grid isn't being built! And we cannot 'manage' with the next 20 years with wind, hydro, nuclear, FF, while making enormous investments into solar energy - we have trouble servicing the rest of our infrastructure with the energy there is left - and will have no capital for expensive luxuries like solar - see discussion on energy for the past several years here on TOD...

the average energy from sunlight is about 5kWh/day per meter^2. That sounds like a lot of energy to me. So a typical house roof receives 450 KWh/day allowing for 20% efficiency that's 90KWH/day. So just the roof area( not being used for anything else) could provide all of the electricity required by the highest electricity consuming nations. Then you have the back yard, vacant lots, parking lots, .... deserts which have about 50% more solar radiation.
20% capture is more than enough, solar heat would be more than that.

Hey, nobody is arguing with you about the 'niceness' of putting some panels on your roof. We are talking about increasing resource (matter) availability - not having more useless electricity for your flat screen tv. Solar does not replace liquid fuels, oil, with which the whole infrastructure functions (and don't even start about hydrogen economy - its been discussed to death here on TOD many times).

The amount of sunlight you can capture and convert to electricity or heat per sq meter might sound much to you if you are fixing some panels on your roof - but its feeble compared to the energy density of FF - huge areas have to be covered with panels, conversion, load balancing and transporting need enormous investments in infrastructure - investments in materials and capital, which we don't have!

And mainly because its not worth it! Having a bit more electricity isn't that important - you cannot get any more metals off the ground with it - you cannot use it to transport anything physical - and you cannot make food with it (all fertilizers and pesticides are made, processed and transported with FF). More electricity is nice but it doesn’t solve the problem - and it certainly doesn’t justify the unlimited investments to it...

No problem with electrifying mines( many are already), transport by electric rail, electricity is used now for refining many metals(magnesium, aluminium. No technical problems here.

Exactly, they are already mainly electric. How are you going to increase the flow rate? Make the conveyors go faster? Open the electricity valve more so that the machines make more stuff? Do you think electricity use is a limiting factor in mining operations currently? It’s not. Making them bigger, more complicated is the limiting factor. They are already big, the biggest machines we have ever made. That's real world engineering. If you have some suggesting of how to actually use more electricity in the process, then please do make a specific suggestion that one can evaluate in engineering terms. Just claiming one can increase production by hosing the process with more power is naive. Electricity is cheap, almost free, in many countries with major mining operations - it is not a limiting factor - something else is - real world limits (capital expenditure, material physics, laws of physics) - otherwise mining industry would've done the magic already.

And the thing is - it doesn't scale! Sure they are making bigger dump trucks every year - but they aren't twice as big as the last ones - in order to seriously go after the low grade ores, you would have to device a way to SCALE the whole process - at least in some significant increments like x2. Why do you think they haven't done it already? As I said - there are limits to the size of the masses you can exploit and process in one go - physical limits - which are HARD to extend - they require real world engineering solutions - not just more of something (power, oil, men).

"In the end all your investments into 'unlimited energy' have actually been an enormously wasteful exercise producing only a marginal increasing in resource availability."

North America now gets 18% of its electrical power from nuclear and 18% from hydro and 2% from wind; none of these investments could be described as "wasted" unless you see no value in electricity. All done by "real world engineering", or am I imagining that the lights go on when I flip a switch.

Nice way to weasel out of the argument, claiming I meant something else and arguing that - its called a straw man argument. Using virtually free energy, in increasing the flow rate of mining of metals, is by definition a wasteful effort. We already waste enormous amounts of energy in inefficient processes. Making a sludge pool bigger or adding more heating with your free power provides marginal benefits, compared to lets say developing a new catalyst which multiplies the production efficiency.

Flip of a switch, yes. But even then you are wrong. You see if more cheaper energy WAS such a big deal, not just in mining but everything else (some processes and industries it is the limiting factor) than we should be seeing a massive effort in investing in new power plants everywhere? If having more power available is so significant, why isn’t every effort and expense being made to make more power? Could it be that there are other limiting factors, which I have already stated - capital, distribution, load balancing - and in fact, hasn't this been already done: so many power plants already built that building more would only have a marginal effect - the law of diminishing returns at work!

And the thing is, your solar power isn't free - its not even cheap - its more expensive than any other (common) form electricity generation (except mayby nuclear) - we're only talking about it because its supposedly 'sustainable' - but for our impoverished and crippled civilization, clinging onto the last rays of the sundown in the horizon of our own making - its too late - we've built dependance on massive but fragile systems which have physical limits that cannot be replaced with another system overnight (just like you cannot just replace all internal combustion engines overnight) - perhaps we should've started investing in it during the 70's maybe - then would've had the time and resources for it, maybe...