Adding id column of table to a hstore column postgres
Usually in SQL double quotes used to specify the identifiers like tables, columns, functions and other DB objects which name contains "non-conventional" characters or have to be case-sensitive. For example it is correct PostgreSQL statement:

create table "This is#my...%TABLE" ("And&amp;Field" int);


(It is not recommended to use such names however because it may cause a lot of problems)

So double quoted literals meanings the DB objects and in the your statement "id" meanings the id field.

On the other hand to specify the string literal in the standard SQL you have to use single quotes. For example:

select 'foo' as "bar field";


Here 'foo' is a text constant and "bar field" is a column alias where double quotes is required because of the space character inside it.

According to the above you have to change your statement to

update new_table set hstore_col = hstore_col || hstore('id',id::text) where id = 1