On 25 Jan, 15:40, Martin wrote:
Have you ever flown over Zuid Holland at night and seen the light
coming off all
those green houses or been in one and watched the heating balance being achieved
by frequently automatically opening and shutting large windows in the top of the
greenhouses?

When I went to Berlin about 10 years ago, we saw them indeed. I have
since saw lots of articles and photos about it. I once asked someone in
this forum not to buy her daffodils from Sainsbury's ;o)