If you are not already running your lights from about 9pm to 9am I'd change that right away; same goes for an air-cooled hood.
I feel your pain; I just dropped $200 on a cheap imported no-name portable a/c unit... the 'good' ones were like $400! And that's in a basement, running at night.

Here's an idea: High temperature shutoff. You plug your 'main' light into the unit, which has a thermostat that you can set to 85'F. When it trips, the power is cut to the socket. You keep as backup a couple flourescent fixtures flanking the edges of your hood, and those stay on during the timed 'on' period to maintain photoperiod without adding significant heat.

Also try switching your intake to come from within your cellar if it doesn't already, or if you have a cool crawlspace duct air from that. For more ideas on cheap passive cooling, check out sites about passive solar home construction, the concept of the envelope house, and thermal mass cooling systems. Often these include a basement room full of large rocks. I've toured a couple, and intend to build one someday. They are fascinating.