Techies rejoice!  Here’s your weekly run-down of some of the cooler green tech stories out there…

• Free energy? There’s a ton of it out there — 7 quadrillion BTUs — in the form of wasted heat. The Department of Energy has announced funding opportunities for R&D on how to tap this massive source of energy. (via Cleantechnica)
  
  
• NYC — the wind energy capital? It seems counterintuitive, but the Carnegie Institution and California State University have found that high-altitude winds, which are concentrated over the Big Apple (among other places), “contain enough energy to meet world demand 100 times over.” (via Green Living Ideas)
  
  
• Can you hear me now? Turns out cell phone towers may be able to double as flood prediction technology. (via The Register)
  
  
• DIY Solar: Solar energy systems are still pretty pricey, but there are a ton of less expensive uses for this technology. Solar backpack maker Voltaic has launched a new section of its website devoted to (relatively) inexpensive diy projects. (via sustainablog)
  
  
• The race is on: Gas 2.0 has launched an “electric vehicle war” between San Francisco and Portland, Oregon. Mayors Gavin Newsom and Sam Adams have already fired shots…
  
  
• Gas up your truck with pine needles? Among other things… Connecticut “tinkerer” Dave Nichols has been hard at work developing a system for powering vehicles on biomass ever since seeing Back to the Future. (via MNN)
  
  
• Power down with your webcam: UK-based environmental computer manufacturer VeryPC has developed an application that combines facial recognition and webcams to power down your PC when no one’s sitting in front of it. (via EcoGeek)
  
  
• So, what is this “smart grid” you speak of? CNET Green Tech’s Martin LaMonica has published a primer on the smart grid concept.
  
  
• You guessed it… iPhone apps: Yep, there always seems to be a green tech find related to the iPhone. This week, the folks at EcoSalon have made it easy: they’ve published a list of the best green apps (and many are free).
  
  

Anything critical we missed? Let us know in the comments…

Image credits: kennymatic at Flickr under a Creative Commons license; Voltaic