Heavy curtains/blinds will help with the windows. As well there are some reflective coverings you can apply to windows now I believe to deflect sunlight and avoid the room heating up because of it. This might help somewhat with the sunlight issue.
Otherwise the air conditioner is the only way you're going to accomplish your task. That or a serious re-do/think on how you're heating your enclosures.
Even if the airconditioning unit isn't set to cool, but just move hot air OUT that might work somewhat.
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