(no line number):
This is BibTeX, Version 0.99d (TeX Live 2015/Debian)
Capacity: max_strings=35307, hash_size=35307, hash_prime=30011
The top-level auxiliary file: Semester.aux
The style file: alpha.bst
Database file #1: bibio.bib.bib
Warning--entry type for "Teknologikatalog" isn't style-file defined
--line 2 of file bibio.bib.bib
I was expecting a `,' or a `}'---line 9 of file bibio.bib.bib
 :

@misc{Teknologikatalog,
    Author = "Teknologikatalog",
    Title = "Energistyrelsen",
    howpublished = {url{https://ens.dk/service/fremskrivninger-analyser-modeller/teknologikataloger},
    {Sidst set 09/11-2016}}

Warning--entry type for "Teknologikatalog" isn't style-file defined

RequirePackage{filecontents}
begin{filecontents}{biblio.bib}
@online{Teknologikatalog,
    Author = "Teknologikatalog",
    Title  = "Energistyrelsen",
    note   = {url{https://ens.dk/service/fremskrivninger-analyser-modeller/teknologikataloger}, Sidst set 09/11/2016},
    year   = 2016,
}
end{filecontents}

documentclass{article}
usepackage[danish]{babel} % just a hunch...
usepackage[hyphens]{url}
bibliographystyle{alpha}

begin{document}
cite{Teknologikatalog}
bibliography{biblio}
end{document}