Google guerrilla solar. A portable solar generator is silent, and it can be easily hidden, total cost could be under $750, depending upon where you purchased the components. 100 watt panels are well under $100. Take a hand truck, mount as large as a panel that you can afford to the back side of the truck, buy a couple of deep cycle batteries, and a charge controller. Buy an inverter sized to your pump off of ebay or amazon. If you need advice, or information, several of the members here are experienced. Solar doesn't have to be expensive. I've picked up over 600 watts of panels on Craigslist for under $200, through a couple of transactions.