Checklist

• I am using the current master branch.

Describe the Bug

When a time-dependent variable, in this case n.links_t.p2 is all 0., the whole table is dropped upon export, here is the line of code where it happens:

I.e. if all columns equal the default, the whole table is dropped. Which leads to results disappearing.

MWE

!wget https://model.energy/networks/c6c1d08a805dbbeae283ce07a1195934.nc
import pypsa
n = pypsa.Network("c6c1d08a805dbbeae283ce07a1195934.nc")
(n.links_t.p2 != n.components["Link"]["attrs"].at["p2","default"]).any()
n.links_t.p2["hydrogen_electrolyser"] = 0.
n.export_to_netcdf("c6-test.nc")
n = pypsa.Network("c6-test.nc")
n.links_t.p2
n.links_t.p2["hydrogen_compressor"] = 0.
n.export_to_netcdf("c6c-test.nc")
n = pypsa.Network("c6c-test.nc")
n.links_t.p2

Solution

Should not actually drop anything, i.e. save the file exactly as the user expects, then let the compression algorithm worry about saving disk space.