The boiler that heats the gîte (and a bit of the house), burns wood chips. These are delivered here by a lorry which blows them into the wood store using special hoses, via an inlet in the bunker. The inlet is matched by an outlet that lets the blowing air out, so the roof doesn't lift off.
The height of the inlet determines the maximum height of the wood chips you can blow into the bunker, and for various reasons, largely down to last-minute changes in the bunker design, these allow only for 20 cubic metres of wood to be delivered at a time, when the lorry can carry 30. The bunker can hold 30 cubic metres, too, but much of the volume is above the height of the inlet.
This is a waste, since the price of a wood delivery is in two parts; a fixed part for the transport, and a variable amount that depends on how much wood you take, so it makes sense to get as much wood delivered each time as you can. I have been taking deliveries of 20 cubic metres at a time for a while, and I have been applying myself to solving the problem of being able to accept deliveries of 30 cubic metres.
You can't raise the height of the inlet since the lorry driver won't be able to reach it to attach the hose. The solution is to attach a tube inside the bunker to carry the wood chips higher up, so a greater volume of bunker can be used. This is what I have been trying to do. I have bought a hideously expensive length of steel-reinforced polythene tubing designed to cope with the wear & tear of wood chippings blasting through it, and various attachments to mate it to the inlet.
I have tried it on one delivery, and it all worked well for a short while, until the tube blocked with wood chips, whereupon the blower tone changed from a steady roar to an angry whine. The lorry driver dived for the "off" switch, but too late, and one of his hose fixings gave way, causing a small explosion of wood chips over the car park, and a writhing hose. I think perhaps I had too tight a curve in the tube, so now I'm changing its path to make it straighter. Next delivery attempt in a few weeks. Watch this space.