There are plenty of other good comments explaining why negative tariffs exist, but not many giving a solution.
In Europe a lot of residential heating is from electricity, so why not enable this on-demand when the electricity prices go low? Most countries have a cheaper night tarrif as traditionally electricity was cheaper as night, but that’s not really true any more. Often the heat energy is stored (e.g. in storage heaters or an insulated hot water tank) before use, so the energy can be buffered here.
Smart metering is one way to do this, but the basic technology to achieve this has existed for decades. In parts of the U.K. residential electric heating is often controlled by a radio signal [0] that is used to enable/disable the off-peak tariff, but is somewhat dynamically enabled based on the electricity demand.