Many people build a walk in fermantation closet and use a garden variety A/C unit for cooling. Although a modified freezer is more effecient. It's also possible to use a refridgerator but most fridges have trouble getting and staying close to 32*F for lagering.
I do seasonal brewing. I'm not trying to reduce my carbon foot print or save the planet just reduce my sky high energy bill. I brew & ferment ale when the weather is cool, this year I plan to lager when the weather is cold.