It’s that time of year when it rains horse chestnuts – if, that is, you stand under a towering tree of the species Aesculus hippocastanum and there’s a gust of wind. There are a bunch of those stately trees on the grounds of what used to be the Bureau of Mines in Albany. It hasn’t been called that since 1996, but old habits are hard to break. The place has been the National Energy Technology Laboratory since 2005.