Some pretty exciting breakthroughs in drying technology in the last few years.
Ultrasonic drying it's called, it doesn't require heat but rather shakes water out of material. Done a bit of reading on it yesterday, it uses similar set ups to a humidifier, which can create cold steam.
There has been commercial implementation in using it along with convection or warm air drying where they blast the material with the ultrasonic waves, but it's most efficient in direct contact set ups where the material is on the vibrating surface.
Up to 5 times more energy efficient than warm air drying and twice as fast.
Well what's the catch?
You get 10kwh of energy in a litre of oil, which can be used pretty much at 100% efficiency in producing warm air, but only 30ish% in producing electrical energy, so if you are using a diesel generator to supply the power for the system your benefit is marginal compared to just burning the diesel. And even in a stationary setup the price of electricity compared to oil still leaves it very expensive.
At the minute they can dry out 8kgs of water for every kwh of electricity, this could improve again but I'm not sure by how much, anyway if we are talking fresh grass to hay that's 6000kgs of water that needs removed so that's 750kwh per ton of dry matter at idk 12c/kwh? 90 euro a ton for dry hay any day of the year. That's not low enough yet but it's still a remarkable reduction in energy cost. Even with a little natural wilt say to 25% we could reduce that cost to 50 euro a ton.
Coupled with macerator mat technology on a good day you'd have hay for 35 euro a ton the same day you mowed it.