Any ideas on the best ways to open and close a solenoid valve (outside) without worrying about constant maintenance(i.e. batteries or the sort), and without worrying about using too much power?
Without more details, it's kinda hard to generate ideas. How often will the solenoid actuate per minute/hour/day?
Will the solution before the solenoid be under high pressure, or low pressure?
What Arduino do you have? Does it have an enclosure? The more info you can give, the better the results you'll get.
Not much power required if a pulse operated low voltage valve?