Tunneling. It's important, it's cool, and most importantly, the advent of TBMs has made it easier and quicker than ever to dig giant tunnels wherever you might need them, admittedly still with a decent sized tunneling crew and a very healthy budget.
What if there was a new way, though? Maybe you could just melt your way through the Earth with a giant plasma torch mounted on a robot? Well, that's what the new startup Earthgrid claims to be going for.
It (in theory) blasts the rock with a giant spiral of plasma torches, vapourising it into tiny pieces that are then carted away behind it in the existing tunnel. Sounds great, apart from one small issue - it needs 40 to 120 megawatts of power to run. That is basically an entire small power station's worth of power. Better make sure the supply cables to this thing don't melt first!
Manufactured homes - also known as trailers, or static caravans in the UK - seem like an obvious solution to housing issues. Built efficiently in a factory, moved around where demand is needed relatively easily, and cheaper than building a house to suit, they should be useful, but instead they have a rather negative reputation.
The wonderful Construction Physics newsletter (which I heartily recommend a subscription to) is diving into this conundrum in a multi-part series, starting with the history of them, their interaction with US building codes, and how they were unpopular almost from the outset. It's a really great read, and part two is already up as well.
There's a lot of places in the world that could do with solar power - in some places, panels are already cheaper per square metre than roofing material, so you'd be an idiot not to build roofs out of them.
A Ukrainian enterpreneur has launched a new design of solar panels designed to go on apartment balconies, and feed up to 600W back into your wiring by plugging it into a standard household electrical socket. Backfeeding like this is only legal in some countries - it's very much not allowed in the UK, for example - but it does massively simplify installation.
Of course, these vertical panels will only be somewhat efficient compared to ones oriented at the sun, but hey, it's free power.